Contents

O. Arnalds and H. Oskarsson Introduction ........................................................................................................................ 5 Opening session Randy A. Dahlgren, Masami Nanzyo and Masahiko Saigusa Volcanic soils: an overview and new perspectives............................................................... 8 E. García-Rodeja A. Martínez-Cortizas, J.C. Nóvoa, X. Pontevedra, and P. Buurman Multivariate statistical analysis of reference volcanic European soils ................................ 10 G. Stoops and M. Gérard

Micromorphology of the volcanic ash soils of the COST-622 reference profiles................ 12 B. Delvaux, T. Delfosse and A.J. Herbillon Non-volcanic Andosols in Europe..................................................................................... 14 Hlynur Óskarsson and Jón Guðmundsson Volcanic soils in an ecological context: The importance of scale, time and function.......... 15 F. Terribile, A. Basile, M. Iammarino, G. Mele, S. Pepe Landslide processes and andosols: the case study of the Campania region......................... 16 Regional soil resources C. Dazzi Environmental features and land use of Etna (Sicily – Italy).............................................. 18 J. Pinheiro, J. Madruga, L. Matos and F. Monteiro "Thermal" soils of Terceira island - the Azores ................................................................. 20 A. Economou, D. Pateras, P. Michopoulos and E. Vavoulidou Properties of soil derived from different volcanic parent material in Greece ...................... 21 J. Balkovi�, B. Juráni Slovakian “Andozem” in the frame of Andosols in Europe ............................................... 23 O.C. Spaargaren Andosols in the World Reference Base for Soil Resources and their correlation within other classification systems .................................................................................... 25 Olafur Arnalds Icelandic volcanic soils ..................................................................................................... 27 Mineral constituents and organic matter Markus Kleber, Fernando Monteiro, Reinhold Jahn Patterns of phyllosilicate mineralogy in COST samples..................................................... 30 P. Buurman, E.L. Meijer, A. Fraser and E. Garcia Rodeja Extractability and FTIR characteristics of poorly-ordered minerals in a collection of volcanic ash soils .......................................................................................................... 31 P. Buurman, K.G.J. Nierop, P.F. van Bergen and B. van Lagen NaOH and Na4P2O7 extractable organic matter in two allophanic volcanic ash soils of the Azores Islands - a pyrolysis-GC/MS study .............................................................. 33 D.W. Hopkins and F. Bartoli Size and activity of the soil microbial community from a range of European volcanic soils .................................................................................................................... 35

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Chemical properties and soil pollution A. Martínez-Cortizas, J.C. Nóvoa, X. Pontevedra and E. García-Rodeja Elemental composition of Reference European Volcanic Soils.......................................... 38 M. Madeira, F. Monteiro, E. García-Rodeja and J. C. Nóvoa-Moñoz Complex exchange properties of soils from a range of European volcanic areas ................ 40 R. Jahn and H. Tanneberg Heavy metal ad- and desorption of andic and non-andic horizons...................................... 42 M. Espino-Mesa., J.I. Rodriguez, and J.M. Hernandez-Moreno BCR sequential extraction of trace elements in COST-622 soils........................................ 44 P. Adamo, A. Basile, C. Colombo, R. D’Ascoli, R. De Mascellis, L. Gianfreda, L. Landi, M.A. Rao, G. Renella, F.A. Rutigliano, F. Terribile, M. Zampella Trace element pollution in Italian volcanic soils: the case study of the Solofrana river valley........................................................................................................................ 46 Physical properties and land use F. Bartoli Shrinkage and drainage in undisturbed soil cores and aggregates from a range of European volcanic soils ............................................................................ 49 C. Fernandez, F. van Oort and I. Lamy Physical and chemical study on irreversible changes of water retention properties in an Azores Andisol......................................................................................................... 51 A. Basile and A. Coppola

Effects of drying on volcanic soil degradation: Practical implication on hydrological behaviour .......................................................................................................................... 53

Rocks and Parent materials P. De Paepe and G. Stoops A classification of tephra in volcanic soils. A tool for soil scientists. ................................. 56 P.Quantin, J. Dejou and M. Tejedor Soils and paleosols on volcanic rocks of Cantal (Massif Central, France); Example of Puy Courny, Aurillac...................................................................................... 58 Ward Chesworth and Felipe Macias Proton pumping, electron pumping, and the activities of aluminosilicate components in the formation of Andosols ......................................................................... 60 C. Colombo, A. Di Cerce, M.V. Sellitto, G. Palumbo and Terribile F. Genesis and formation of volcanic soil in Fregrean Fields................................................. 61 Gy. Füleky, Á. Kertész, B. Madarász, O.Fehér Soils developed in volcanic material in Hungary ............................................................... 63 S. Jakab, G. Füleky and O. Fehér Environmental conditions of Andosol formation in Transylvania (Romania). Soils of the Gurghiu volcanic chain. .......................................................................................... 65 B. Juráni Some specific features of soil distribution in volcanic mountains of Slovakia.................... 67 M. Nanzyo and T. Takahashi Relationship between Andosolization and Elemental Composition of Volcanic Ash Soils in Japan............................................................................................................. 68 Paul Quantin

Andosols criteria and Classification of European Volcanic Soils : up to date proposals. Genesis, key factors and distribution ................................................................................. 70

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Micromorphology, weathering and mineral soil constituents R. Bäumler Soil development processes in non-volcanic Andosols. ..................................................... 72 E. García-Rodeja, T. Taboada, A. Martínez-Cortizas, B. Silva and C. García

Soils with ‘andic’ properties developed from non-volcanic materials. Genesis and implications in soil classification....................................................................................... 74

E. García-Rodeja, J.C. Nóvoa-Muñoz, A. Martínez-Cortizas and T. Taboada Abrasion pH and abrasion solution composition in reference European volcanic soils....... 76 S. R. Gislason, and E. H. Oelkers Dissolution rate of basaltic glass. ...................................................................................... 78 Thorsteinn Gudmundsson and E.A FitzPatrick Micromorphology of an Icelandic Histosol........................................................................ 79 Rannveig Guicharnaud and G.I. Paton The effect of acid deposition on ion leaching and weathering rates of an Andosol and a Cambisol............................................................................................... 81 Herre A., Lang F., Siebe C. and M. Kaupenjohann Development and composition of surface coatings in volcanic soils .................................. 82 M.V. Sellitto, G. Palumbo, A. Di Cerce, C. Colombo, Application of diffuse reflectance spectroscopy to characterise volcanic soil color and mineralogy.................................................................................... 83 B. Sigfusson, S.R. Gislason and G.I. Paton Soil solution composition and weathering rates of a Histic Andosol, Iceland..................... 85 Organic matter and biological activity Rannveig Guicharnaud and Hólmgeir Björnsson C and N mineralization rates of cultivated Icelandic Andosols .......................................... 88 B. Sigfusson, G.I. Paton and S.R. Gislason Soil carbon fluxes during leaching of a Histic Andosol, Iceland - evaluation of scale and sampling techniques....................................................................................... 90 E. Vavoulidou, M. Wood and E.J. Avramides Biophysical characterization of soils on the island of Santorini (Greece) ........................... 91 E. Vavoulidou, A. Oikonomou and F. Bartoli Enchytreid reproduction test in volcanic material on Santorini. ......................................... 93 Physics-chemistry, nutrient and pollutant binding E. Auxtero and M. Madeira P adsorption and desorption capacities of andisols from European volcanic areas ................................................................................................................... 95 Julian J.C. Dawson, Olafur Arnalds and Graeme I. Paton Distribution and bioavailability of heavy metals in Icelandic Soils. ................................... 97 T. Delfosse, P. Delmelle and B. Delvaux Acid neutralizing capacity of Andosols: Effects of weathering stage and sulfur storage..... 99 Gy. Füleky Phosphate sorption of European volcanic soils ................................................................ 100 E. García-Rodeja, J.C. Nóvoa, X. Pontevedra, A. Martínez and P. Buurman Characterization of reactive components using selective dissolution methods, and their relation to soil properties in European Volcanic Soils ....................................... 102 Marin Ivanov Kardjilov, Sigurður Reynir Gíslasson, Guðrún Gísladóttir and Árni Snorrason GIS for the geochemistry of surface waters in Northeastern Iceland ................................ 104

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J.C. Nóvoa; X. Pontevedra; A. Martínez-Cortizas and E. García-Rodeja Mercury accumulation in European volcanic soils with special reference to the role of the properties of andic horizons...................................................................... 106 Graeme I. Paton, C.J. Paterson, Alan Winton, Tinnakorn Tiensing, Olafur Arnalds

and Julian J.C. Dawson Distribution, bioavailability and behavior of persistent organic pollutants in Andosols: with specific reference to Iceland................................................................ 108 Grégoire Pochet and Bruno Delvaux Water properties of volcanic ash soils rich in high charge halloysite................................ 110 Sansoulet J., Cabidoche Y.M., Cattan P., Clermont Dauphin C., Desfontaines L., Malaval C. Solute transfert in an andisol of the French West Indies after application of KNO3 : from the agreggate to the field experiment ...................................................................... 111 T. Takahashi and M. Nanzyo Aluminum solubility in nonallophanic Andosols from northeastern Japan....................... 113 D. Wolff-Boenisch, S. R. Gíslason and E. H. Oelkers Proton/Al3+ exchange reaction as a precursor of the hydrolysis of volcanic glasses.......... 115 Land use S. Armas-Espinel, C.M. Regalado and J.M. Hernández-Moreno Response of physical properties of Andisols and andic soils from Tenerife to saline and sodic treatments.......................................................................................... 117 Frédéric Feder and Antoine Findeling Solute and water fluxes in andisol fertilized with pig manure: soil columns experimentation.......................................................................................... 119 O. Fehér, B. Madarász, Á. Kertész and G. Füleky Land use changes of traditional vine-growing areas in volcanic regions of Hungary........ 121 C. Jiménez, M. Tejedor and M. Rodríguez Influence of land use changes in the soil temperature regime of Andisols........................ 123 B. Madarász, Á. Kertész Soils developed on volcanic material and their erodibility in Hungary............................. 125 J. Madruga, J. Pinheiro, and L. Matos Soil P status and eutrophication on volcanic watershads of the Azores ............................ 126 M. Tejedor, C. Jiménez and F. Díaz Use of volcanic mulch for saline-sodic rehabilitation: short and long term experiences in the Canary Islands.................................................................................... 127

5

Introduction

O. Arnalds and H. Oskarsson Agricultural Research Institute (Rala), Iceland

A group of European soil scientists has over the past six years participated in an European COST action titled Soil Resources of European Volcanic Systems (COST-622). Soils of volcanic areas often exhibit unique properties that separate them from other soils on Earth. The most common soils of volcanic regions are Andosols, but the Action had a broad agenda dealing with all soils that form in volcanic regions regardless of age of the parent materials. The action is chaired by Francois Bartoli (France). During the action, both workshops and small group meetings have been held in various locations in Europe, based on activity of 5 working groups. Action workshops have been held in Iceland, Napoli, Canary Islands, Azores, Sicily, Massive Central (France), Manderscheid (Germany), Budapest, Wageningen, and with small group meetings at various locations in Europe. This issue of Rala Report contains abstracts for the last workshop of the COST-622 action, which is held in Akureyri and Hallormsstadur in North and East Iceland. It exemplifies the extensive research activity throughout Europe involving soils of volcanic areas. There are about 60 abstracts, covering a range of issues such as mineralogy, chemistry, physics, organic matter, soil genesis and land use. It also includes abstracts from non-European scientists, such as from the U.S., Canada and Japan. The fact that scientists from 17 countries will attend the meeting in Iceland reflects well the international aspect of this work. One unique aspect of the COST-622 was a joint sampling of soil pedons in the participating countries. The samples were subsequently distributed to the participating laboratories for various analyses. The European COST-622 pedons are therefore among the best studied soils in the world. Many of the abstracts included here deal with these COST pedons. The Action has brought a new light on the unique properties of volcanic soils and their distribution in Europe, and has entered European soil scientists more actively into international scientific debate about such soils. This issue is an example of other similar publications with abstracts in relation to this COST Action (e.g. COST-622, 1998, 2001, 2002; Kertész, 2002). Papers from the German meeting were also published in the Mainzer Naturwissenschaft Archiv 40. In addition, the partnership has resulted in special issues of the scientific journals Geoderma (Bartoli et al., 2003) and Catena (Arnalds and Stahr 2004). Publication activities have also included field guides and reports of various working groups. The partnership established between European soil scientists involved in research of volcanic regions by the EU-COST program is an excellent example of what such programs can achieve. It has been especially important for the Icelandic partners, which has the largest extent of Andosols in Europe, enhanced both science and education this field and opened up research co-operation and friendship among partners that will remain long after the conclusion of the COST action. References Arnalds, O., and K. Stahr. 2004. Volcanic Soil Resources: Occurrence, Development and

Properties. Catena 56(1-3). Special issue. Bartoli, F., P. Buurman, B. Delvaux, and M. Madeira. 2003. Volcanic soils: Properties and

Processes as a Function of Soil Genesis and Land Use. Geoderma 117(3-4). Special issue.

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COST-622. 1998. Soil resources of European volcanic systems. Iceland 1998. Abstracts. If any references, they should follow similar format as Soil Science Society of America Journal, both within the main text and in the reference list.

COST-622. 2001. Volcanic soils: properties, processes and land use. International Workshop, Ponta Degada (S. Miguel, Azores, Portugal. Abstracts. Soc. Port da Ciencia do Solo. ISBN 972-8669-09-8.

COST-622. 2002. Program and abstracts of the COST-622 meeting: Soil resources of European Volcanic Systems. Manderscheid / Vulkaneifel. Maarmuseum, Manderscheid, Germany.

Kertész, Á. COST ACTION 622 Soil resources of European volcanic systems. Abstracts and field guide. Hungarian Academy of Sciences, Geographical Research Institute, Budapest, Hungary.

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8

Volcanic soils: an overview and new perspectives

Randy A. Dahlgren1, Masami Nanzyo2 and Masahiko Saigusa2 1University of California – Davis, USA; 2Tohoku University – Sendai, Japan

Volcanoes are revered and feared for their awesome and devastating eruptions that obliterate terrestrial ecosystems, and often cause tremendous casualties to humans and wildlife. Yet from these ashes of devastation arise some of the most productive soils in the world with the capacity to sustain high human population densities. Soils formed in volcanic ejecta have many distinctive physical, chemical and mineralogical properties that are rarely found in soils derived from other parent materials. These distinctive properties are largely attributable to the formation of noncrystalline materials (e.g., allophane, imogolite, ferrihydrite) containing variable charge surfaces, and the accumulation of organic matter. The nature and properties of volcanic soils have been intensively studied, yet the unifying principles concerning their genesis, mineralogy, biological properties and agronomic utilization have not been fully established. The bulk of previous research has focused on volcanic soils formed in the humid-temperate environment. In contrast, there is a paucity of information regarding volcanic soils formed in tropical, arid and cold regions. There is a strong need for a comprehensive global analysis of existing data to establish thresholds in soil genesis (especially between competing soil groups) and mineralogical transformations. Transitions between allophanic and nonallophanic Andosols are not fully understood, nor are transitions between dominance by noncrystalline (e.g., allophone, imogolite, ferrihydrite) versus crystalline (e.g., halloysite, 1:1- 2:1 mixed layer clays) mineralogical assemblages. A key to establishing threshold conditions is to understand processes regulating aqueous aluminum and silica activities and kinetic factors regulating aqueous-solid phase interactions. There are numerous opportunities to apply our knowledge of volcanic soils to important environmental issues. Unique properties of volcanic soils, such as high anion exchange capacity, provide opportunity for attenuating nitrate leaching in agricultural systems and potential for utilization in low-level radioactive waste disposal sites to retain radioactive anions (e.g., iodine, technetium). Similarly, the abundance of noncrystalline materials and organic matter provides a high capacity to retain heavy metals, trace elements (cations and anions) and organic compounds making volcanic soils a good candidate for disposal of biosolids. Volcanism plays an important role in the global carbon cycle, representing a primary source and sink for carbon. Soils formed in volcanic materials contain the largest accumulations of organic carbon among the mineral soil orders. Understanding the mechanisms by which organic matter is preserved in these soils may contribute to management techniques to sequester carbon as soil organic matter. Given our understanding of the nature and properties of volcanic soils, there is an opportunity to apply this knowledge to agronomic management practices that provide for sustainable production of food, fiber and forage. Within the concept of sustainable management, there is a lack of knowledge concerning the interaction of biological processes with chemical and physical soil properties of Andosols. The differences in the agricultural productivity among Andosols are largely attributed to the colloidal composition in the rooting zone, namely allophanic versus nonallophanic. Nitrogen and phosphorus cycling, aluminum toxicity, acidity amelioration, mycorrhizae interactions and protection from soil pathogens require additional research in terms of their role in soil quality and sustainable management practices. Phosphorus is often a growth-limiting nutrient for agricultural production in volcanic soils. In young volcanic soils, apatite plays an important role in providing phosphorus for revegetation and crop production without addition of phosphorus fertilizers. Under low phosphorus availability, inoculation with mycorrhizae fungi greatly enhances

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phosphorus availability. Some plants also have the ability to enhance phosphorus availability by growing roots to completely encapsulate phosphorus-bearing materials. Silicon is considered an agronomically essential element for certain plant species (e.g., rice, sugarcane). Soluble silica concentrations are strongly related to soil mineralogy and the intensity of the weathering environment. Application of silicate fertilizer not only enhances plant silicon levels, but may also enhance phosphorus availability by increasing the zero point of charge, thereby decreasing the phosphate sorption potential. Application of controlled release fertilizers with nutrient release patterns synchronized to crop nutrient demands can greatly improve fertilizer-use efficiency for a number of crops grown on Andosols. Aluminum toxicity is most prevalent in nonallophanic Andosols containing high concentrations of water soluble and KCl-extractable aluminum derived primarily from 2:1 layer silicates. While these forms of aluminum may be toxic to sensitive crops, they may also enhance crop productivity by suppressing several soil borne plant pathogens. Subsoil acidity may limit root development resulting in deep leaching of nutrients and loss of crop productivity. Surface application of gypsum, phosphogypsum and organic calcium salts may provide a cost-effective means of ameliorating subsoil acidity. Based on their degree of development and soil properties, volcanic soils may be considered among the most productive agricultural soils (generally younger soils) or among the most infertile agricultural soils (generally nonallophanic Andosols). To maximize the productivity of volcanic soils, proper management based on an understanding of the unique physical, chemical, and mineralogical properties of these soils must be practiced.

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Multivariate statistical analysis of reference volcanic European soils

E. García-Rodeja1 A. Martínez-Cortizas1, J.C. Nóvoa1, X. Pontevedra1, and P. Buurman2

1Dept. Edafología y Química Agrícola, Facultad de Biología, Universidad de Santiago de Compostela 2Laboratory of Soil Science and Geology, Wageningen University, Wageningen, The Netherlands

Within the framework of EU-COST action 622 twenty soils developed on volcanic materials from Italy (EUR01 to 04), Azores Islands (EUR05, 06), Iceland (EUR07 to 09), Canary Islands (EUR10 to 12), Greece (EUR13 to 15), France (EUR16, 17) and Hungary (EUR18 to 20) were described, sampled and analyzed for a large number of soil properties by different research groups. This database provides a good opportunity for the application of multivariate statistical methods, although the number of samples is moderate (94). We developed two different approaches for the explanation of the variance structure of the European volcanic soils: 1) an exploratory analysis using principal component analysis (PCA), and 2) a confirmatory analysis based on PCA separation and knowledge on andic and vitric horizons using discriminant analysis.

The soil properties used for the analyses are listed in Table 1, and relate to aspects like granulometry, soil reaction, organic matter, and parameters characterizing the reactive components. As mentioned above, in a first step we performed an exploratory PCA analysis. Six axes explained 84% of the total variance and the first two a 60%. From the projection of these first two axes as well as from the components matrix it was clear that the first factor is dominated by properties related to reactive components at one side and soil reaction, exchange complex (SB, Bsat) and the composition of allophane (Alp-Alo/Sio) at the other side; while the variation in the second component is dominated by the organic matter and its influence

in other soil properties (C, Alp, Fep, Alp/Alo, CEC). The clay content groups with the last set of properties, perhaps due to its effect on soil CEC. The plot of the samples in the projection of these two first axes (Figure 1) shows a separation of andic and vitric horizons. Non-andic/vitric horizons plot in the left side while vitric and silandic horizons spread to the right side, but remain separated. The maximum of reactive components is represented by all horizons of soil EUR06 (Azores). Organic and aluandic horizons appear above the silandic horizons. Their small number does not result in a clearly separated group.In addition,the Alu-andic horizons are very rich in organic matter.

Table 1 Soil properties of European volcanic soils used for multivariate statistical analyses Granulometry clay

Soil reaction pH in water (pHw), pH in KCl (pHk), pHk-pHw

Organic matter

total C content

Exchange complex

CEC, Base cations (SB), base saturation (BSat)

Reactive components

Total Al and Fe (Alt, Fet), extracted in NaOH (Aln, Sin), extracted in acid aommonium oxalte (Alo, Feo, Sio), extracted in CuCl2 (Alcu), extracted in Na-pyrophosphate (Alp, Fep), extracted in dithionite-citrate (Fed). pHNaF (pHf), P rentention Calculated variables: Alo+1/2Feo, Alo/Alt; Alp/Alt, Alp/Alo; (Alo-Alp)/Sio, Fed/Fet, Feo/Fed, Fep/Feo; allophane content

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To confirm this interpretation we performed a discriminant analysis, using as classification criteria the andic nature (i.e. 5 aluandic, 41 silandic, 23 vitric, 5 organic and 20 non-andic horizons).

-2,0

-1,5

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0,0

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1,0

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-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0

Factor 1

Non andic

Vitric

Organic

Aluandic

Silandic

Figure 1. Projection of the first two axis of the PCA

Two canonical functions explained 98% of the variance and included: P retention, total C, pH in NaF, pH in water and Alp as predictor variables. Again, the first canonical function separated the horizons by their andic/non-andic nature and the second by the role of the organic matter. The elimination of the organic horizons gave also two significant canonical functions including P retention, pH in water, Alo and Feo; while the elimination of P retention resulted in inclusion of pH in water, pH in NaF, Alo, Sio and the ratio Feo/Alo. Thus, if organic horizons are not considered only variables related to the reactive components are significant in the separation. These resutls are consistent with the nature of andic soils and with the criteria required for their characterization. These results are promising but also indicate that the disgnificance of the analysis could be improved by 1) enlarging the database of andic volcanic soils, 2) include non-volcanic andic soils and 3) use other statistical methods such as SEM (structural equation modelling), which take advantage of the large redundancy among soil the properties.

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Micromorphology of the volcanic ash soils of the COST-622 reference profiles

G. Stoops1 and M. Gérard2.

1 Laboratorium voor Mineralogie, Petrologie en Micropedologie, Universiteit Gent, Belgium; 2 Institut de Recherches pour le Développement (IRD), Bondy, France

In the frame of the COST-622 action, undisturbed and oriented samples were taken from 17 reference profiles on volcanic ash. Thin sections were prepared in three different laboratories, and systematic micromorphological descriptions made according to Stoops (2003). The least developed profiles are found on Iceland and Santorini. More developed profiles occur in the Massif Central (France), and southern and central Italy, whereas the most developed ones were sampled on Tenerife and the Azores. The Iceland profiles (N7-N9) are characterised by the presence of high amounts of weakly decomposed organic material, mainly subhorizontally oriented organ residues. An alternation of organic and inorganic layers is noticed. Within the inorganic layers a microstratification, often showing different mineral parageneses, occurs. These features point to a sequential deposition on the surface. The inorganic material is always unweathered, varying from pumice, over different types of glass to pyroclasts with single grains of feldspar and pyroxene. The presence of peat-like organic layers and diatom skeletons indicates moist conditions. A higher micromass content in some layers points to a possible erosion product of more evolved soils. Locally an isoband structure latter points to repeated freeze-thaw processes. The Santorini profiles (N13-N15) (only Ah horizons sampled) are merely coarse volcanic deposits of different composition, some pumice rich, other dominantly composed of pyroclasts, with only a low degree of weathering. Feldspars and pyroxenes are general angular and fresh. The small amount of micromass, occurring as coatings or aggregates, has an undifferentiated b-fabric. The microstructure varies from coarse monic to enaulic and chitonic. The Italian profiles (N1 and N2 Naples, N3 and N4 north of Rome) are all characterised by a bimodal granular microstructure in the topsoil, grading with depth to a blocky one with a weakly separated granular intrapedal microstructure. The coarse material of N1 and N2 contains variable amounts of pumice, pyroclasts and volcanic minerals, whereas in N3 and N4 pyroclasts dominate. Compared to the profiles of Iceland and Santorini the amount of micromass has considerably increased, but the b-fabric remains undifferentiated. Rock fragments, especially pumice fragments, show a micromass coating. Infillings and excrements point to a high biological activity. In the lower part of some profiles truncated, more evolved palaeosols, with anisotropic clay coatings, appear, pointing to polygenetic soils. The French profiles (N16-N17, Massif Central) (only Ah and Bw horizons sampled) have a granular microstructure, sometimes weakly separated forming angular blocky aggregates in the Bw horizon. The coarse material is a mixture of mainly microlithic pyroclasts, pyroxenes and feldspars, with a dominance of pumice in the Bw of N16. Rock fragments are surrounded by a coating of micromass with undifferentiated b-fabric, sometimes with a lighter colour than the rest of the micromass in the same horizon. Two profiles were sampled on the Azores, one on Fayal (N5) and one on Pico (N6). Angular blocky microstructures prevail, except in the Ah were granular microstructures occur. Microlithic pyroclasts and vesicular vitric lapilli dominate the coarse material, although fresh pumice is found in the top of N5. Most of the vitric vesicular lapilli show a pellicular weathering to an orange isotropic material composed of Si, Al and some Fe. The often dominant micromass has an undifferentiated b-fabric. Hypocoatings and nodules of iron

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hydroxides point to a mobility of iron. Isotropic allophane coatings and anisotropic clay coatings are indications of a more advanced stage of weathering and soil formation. The profiles of Tenerife (N10-N12) are clearly polygenetic. The microstructure grades from granular in the surface horizons to angular blocky in the solum, except when layers of loosely packed lapilli are intercalated. The glass is commonly weathered to an orange isotropic material. In general, rock fragments and minerals show a considerable degree of weathering. The micromass, sometimes dominant, still has an undifferentiated b-fabric, which locally becomes weakly stipple speckled, pointing to the formation of phyllosilicates. With progressing weathering and soil formation, microstructure evolves from single grain over granular to blocky. In general a high biological activity is noticed, except in the profiles of Iceland, where microstratification is preserved throughout the profiles. Only in an advanced stage of weathering the undifferentiated b-fabric changes to a speckled one. The orange alteromorphs of volcanic glass have an allophane like composition and strongly influence the results of selective oxalate extractions of Si, Al and Fe. The coatings of micromass around pyroclasts observed in most profiles are typical for these volcanic ash soils. In several profiles indications are found of a polygenetic soil formation and truncated palaeosols. References Stoops, G. 2003. Guidelines for the Analysis and Description of Soil and Regolith Thin Sections.

SSSA. Madison, WI., 184 pp

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Non-volcanic Andosols in Europe

B. Delvaux, T. Delfosse and A.J. Herbillon Soil Science Unit, Université catholique de Louvain, Belgium

In Europe, reported occurrences of non-volcanic Andosols are linked with Hercynian rocks in smoothened highlands with a cool and humid climate. These occurrences have been reported in British islands, Northwest Portugal and Spain, France, Switzerland and Austria. Most of these non-volcanic Andosols are non-allophanic and thus exhibit an aluandic diagnostic horizon in the WRB-system. Their most prominent features are strong acidity, large accumulation of organic carbon and incorporation of iron and aluminum into metal-humus complexes.

The regional distribution of non-volcanic Andosols matches very well with the one described for the new “Umbrisol” Reference Soil Group, since the latter occur in “cool and humid regions, mostly mountainous and with little or no soil moisture deficit”. In these regions, developed soils associated with Umbrisols are either non-volcanic Andosols or Podzols or both.

The genesis of Umbrisols promotes the accumulation of organic carbon as well as strong acidity and base desaturation despite of limited profile development. These conditions make Fe and Al available for the formation of metal-humus complexes, since weatherable minerals act as metal sources during soil genesis. These complexes are major components of non-allophanic non-volcanic Andosols. In these soils, the relative dominance of Fe or Al in metal-humus complexes –as estimated by selective extraction– is linked with the nature of soil parent material, which encompasses a large diversity: oxide-rich clay regoliths, basic and metabasic rocks, as well as more siliceous rocks such as micaschist and granite. In several cases, the mobilization and complexation of iron contributes to the formation of the andic horizon, which is in fact part of an umbric horizon in non-allophanic non-volcanic Andosols.

The occurrence of Umbrisols, Andosols and Podzols in the ecological conditions of cool and humid European mountains thus strongly suggest common soil processes involved in the formation of these three reference soil groups. We believe that these groups actually form an evolutive sequence Umbrisol�Andosol�Podzol. In this sequence, non-allophanic Andosols are likely Umbrisols further developed by increasing Fe and Al complexation (acido-complexolysis). They may also be regarded as poorly developed Podzols –‘abortive Podzols’–, wherein the mobility of organic matter has been hampered by carbon stabilization into metal-humus complexes. We believe that the Umbrisol-Andosol-Podzol association or sequence requires further studies to better understand C storage and fate in mountain soils, and to better know the distribution and occurrence of European Andosols.

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Volcanic soils in an ecological context: The importance of scale, time and function

Hlynur Óskarsson and Jón Guðmundsson

The Icelandic Agricultural Research Institute, Reykjavík, Iceland Soils are an important component of terrestrial ecosystems. From an ecosystem perspective soils are central to certain key ecosystem functions, such as, biogeochemical cycles, hydrology and media for organisms. The significance of soils to ecosystem function is important at the scale of the ecosystem, but also at larger scales, such as at the level of a watershed or a landscape. Even on a global level soils play an important role, for example in biogeochemical cycles. Andosols exhibit unique properties, so-called andic soil properties, and many of these are important in terms of ecosystem function. Properties such as high water holding capacity and high carbon content have important ramifications at scales ranging from the ecosystem to the global level. The presentation will address the importance of Andosol properties to ecosystem function, with emphasis on the significance of temporal and spatial scales in this respect. Examples for illustration will be drawn from various studies in Iceland.

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Landslide processes and andosols: the case study of the Campania region

F. Terribile1, A. Basile2, M. Iammarino1, G. Mele2, S. Pepe1 1Dipartimento di Scienze del Suolo, della Pianta e dell’Ambiente, Università di Napoli Federico II 2 Institute for Mediterranean Agricultural and Forest Systems, CNR, Ercolano (NA), Italy

The general goal of this research has been the study of soils connected to the initiation

mechanisms of debris flow landslide in the Campania region. More specifically the following aims were investigated: 1) a regional scale analysis concerning the relationship between soil types and landslide initiation mechanisms in Campania; 2) a local scale analysis on selected sites where hydropedological landslide initiation processes were explored.

The study was conducted in the following step: (i) analysis of historical reports; (ii) georeferencing of the main landslide detachment crown in Campania; (iii) morphological description and sampling of selected profiles located in the detachment crown; (iv) chemical and physical (hydrological) analysis; (v) hydrological physically based modelling for water balance simulation at the time of landslides.

The analysis has clearly shown that the most important Campanian debris flow landslide occurred in mountains very fertile forest (mostly chestnut) ecosystem with complex sequences of Andosols both as surface and buried soils. Such soils have a high allophane and imogolite content, high water retention properties and well developed tixotropy. These features along with the high slope and/or the slope discontinuity (roads, cliff) seem to have played a very important rule in the landslide initiation mechanisms.

From the outputs of the regional scale analysis, few selected sites (5 soil profiles) were investigated with a detailed analysis of the hydropedological processes affecting landslide initiation mechanisms. Bulk and undisturbed (steel cylinders) samples were collected in each soil horizon for standard chemical analysis and for determining hydraulic properties by the Wind method.

Physically based water balance models have been applied. More specifically, the knowledge of water retention and hydraulic conductivity functions along with the knowledge of the boundary conditions enable the solution of the Richard equation and therefore the inference of water balance in the period of the landslide. Functional properties (i.e. water content at specific depth, soil weight at specific depth) were then defined and obtained as an integrated model output for estimating the susceptibility of the soil system to landslide initiation processes.

17

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18

Environmental features and land use of Etna (Sicily – Italy)

C. Dazzi Dipartimento di Agronomia Ambientale e Territoriale – Università di Palermo - Italy

Owing to its position, an isolated mountain in the middle of Mediterranean sea, to its shape and size and to its activity which continue uninterruptedly since its eruption from the sea approximately 550.000 years B.P., Etna is certainly one of the most important volcano of the word and one of the most active (in the sense of “productive” and eruption frequency). It is a complex strato-volcano, formed of lava flows alternating with pyroclastic materials, emitted over various eruptive areas which have, over centuries, built up the actual volcano. Today Etna reaches 3315 meters above sea level, a huge triangular shape with its peak blown off, where explosions at the summit develop into spectacular eruptions. The gentle slopes towards the base of Pleistocene clays, form most of the eastern third of Sicily. The climate in the Etna area is basically Mediterranean but rainfall and temperatures are affected by height, exposure of slopes, by winds and by clouds coming from the coast. Temperature distribution is uniform around the volcano but rainfall is irregular. Moist winds from the sea bring rain to the eastern slopes. The pedoclimate show an udometric regime ranging, according to altitude, from xeric to udic and a thermometric regime ranging from thermic to mesic to frigid. On the lower slopes of the south-western flank the morphological features show alluvial terraces, while there are marine terraces on the south-eastern flank. These may be interrupted by sub-vertical escarpments which reach 200 metres in height and few kilometres in length. Above 900 m altitude forests prevail, lava flows greatly influence the landscape and produce morphologies with irregular, rough surfaces. Slopes get steeper with frequent abrupt variations; some areas with gentle slopes and regular contours can be found. A peculiar morphological feature are the numerous cones along the perimeter, they are the result of the accumulation of the pyroclastic ejected. Above 2000 m the very steep slopes reach the main craters. After the recent lava flows the land has become a blackened moonscape. The wide variation of soil types is due to the parent material, age, different morphologies, climatic features and last, but not least, to exposure and to winds which carry and deposit ash and lapilli which may be abundant. These characteristics greatly influence land use and distribution of vegetation. The following vegetation belts can be distinguished:

1. base to 900 m approx: the crop belt with many orchards of different fruits. 2. from 900 m to 1500 m approx: the woodland belt where forest vegetation prevails. 3. from 1500 m to 1800/2200 m: the mountain belt dominated by vegetation of high

Mediterranean mountains until the altitudinal vegetation limit which ranges from 1800 m to 2200 m a.s.l. according to exposure and morpho-climatic conditions.

In the crops belt, agriculture takes on very peculiar features mainly determined by the physical characteristic of the landscape. Tree fruit cultivations characterize above all the landscape of this crop belt owing to the wide surface that they occupy and for the peculiarity of some of their productions. The most cultivated species both with specialized systems or in promiscuous cultivation are: citruses, olives grapes, pistachio, apples, pears, cherries and kernels. It is to outlined also the prickly pear cultivation and of others tree fruit cultivations that show a marginal importance for the Etna area but that, as happens also for the strawberry of Maletto and for the sub-urban horticulture supply local markets.

19

Between 1000 and 1500 meters, the forest area is characterized by important forest formations: prevail the pine-wood with laricio Pine, the birch-wood with Etna birch, the beech-wood and the poplar-wood with trembling poplar. The chestnut-wood is diffuse and depending on the local situations represents a wooden tree used mostly for timber production, and sometimes for the fruit yields. The vegetation in the mountain belt is characterized by the astragalus that, in this particular environment shows different aspects. The most important is represented by the Spino Santo (Astragalus siculus) which dominates the landscape where thorny xerophytes prevail.

20

"Thermal" soils of Terceira island - the Azores

J. Pinheiro1, J. Madruga1, L. Matos1 and F. Monteiro2

1Departamento de Ciencas Agrarias, Universdade dos Açores Angra do Heroismo, Azores, Portugal; 2Departamento de Ciencias do Ambiente, Instituto Superior de Agronomia, Lisboa, Portugal

The volcanic nature of the Azores islands determines that hydrothermal activity occurs at surface in some localized spots, generally associated to gas emissions of varied chemical composition, and exerting a direct influence on pedogenesis. In the hydrothermal Furnas field (Terceira island) and its vicinities we studied two pedons, distant from each other not more then 50 metres, developed from the same parent material (basaltic lapilli) and showing a similar horizon sequence, being only one of them under present hydrothermal influence as observed from profile temperatures and gas emissions. The analytical results from these two pedons show some dramatic differences concerning the weathering degree as inferred from particle size distribution. The “thermal” pedon also shows drastic base depletion (aqua regia extracted) as compared to the non-thermal one. Acid oxalate extractable Al and Si also have an intense decrease in the C horizons of the “thermal” soil which, consequently, has low contents of allophonic materials.

Possible taxonomic implications of the hydrothermal effects are also addressed.

21

Properties of soil derived from different volcanic parent material in Greece

A. Economou1, D. Pateras2 , P. Michopoulos1 and E. Vavoulidou3. 1,2,3 National Agricultural Research Foundation, 1 Forest Research Institute, Athens; 2Institute of Soil

Clasification and Mapping, Larissa, 3 Soil Science Institute, Athens. Five soil profiles developed on volcanic parent materials were selected throughout Greece. Three were taken from the South Aegean Volcanic arc and two from the island of Lesbos and Limnos, North East of Greece (Fig. 1). Profile No1, Methana is located on the east peninsula of Peloponnesus, at 316 m altitude, Landform: mountainous relief, slopes >25%, position: middle slope, vegetation: Pinus halepensis, Pistacia lediscus, Pistacia terebinthus, Quercus coccifera, Acer creticus, Gyclamem greca. Parent materials are andesites (SiO2: 56-63%). Although the volcano is considered active for the last 900.000 years the last eruption is dated around 250 years BC and a tomb of 1.3 km was formed. Two profiles come from Santorini Island, profile No2, Vlychada and No3 Profitis Ilias, which were also selected in the frame of Cost 622 action and possed the No13 and 14 reference soil profiles of the Soil Resources of European Volcanic Systems Programme.

Fig.1 Volcanic arc

No2 is situated in the south of Santorini, at 80 m altitude, Landform: Volcanic sediment plain, Land element: Terrace, slope 2%, Position: Intermidiate,Vegetation: Grassland, Chrysanthemum coronarium, Thymus, Echium Plantagineum sp., Geranium sp., Scolymus hispanicus, Lolium. sp. Parent material: pumice. No3 is situated in the south east of Santorini, at 300 m altitude, Landform: Volcanic sediment plain. Slope: Very steep, Position: Middle slope, Vegetation: 90% Rhagnalon rupestre, Carthamus sp. Parent material: pumice, volcanic ash, Upper Pumice series.

Profile No 4, has been taken from Mitilini Island, at 460 m elevation. Landform: hilly. Land element: Slope, Slope: 18-40%, Position: Middle slope Vegetation: Quercus coccifera, Q. infectoria, Pinus brutia, Cistus incanus. Parent material: Dacitic, latitic, latiandesitic, and quartz-andesitic, minor rhyodasitic lavas. Profile No 5 has been taken from Limnos Island, at 280 m elevation, Landform: hilly. Land element: Slope, Slope: 18-40%, Position: Upper slope, Vegetation: Avena sterilis, Bromus hordeaceus, Hordeum bulbosum, Crepis foedida. Parent material: Volcanic Traheyiandesites, Andesites. The Methana profile (No1) is of shallow depth, has a thick layer of organic matter, 6 cm thick, derived from the pine forest litterfall. The soil depth is 34 cm, with a lot of stones on the surface. Four horizons have been distinguished, A0 (6-0 cm), A1 (0-14), A/C (14-34) and C (>34), with a light texture for all of them. The sand fraction is 80, 82 and 82% and the clay one is 12, 10 and 8%, the pH (1:1H2O) is 6.9, 7.1 and 7. The CEC is 4, 5.8 and 4.8 cmolckg-1, the P olsen 344, 2.5 and 2.5 mg kg-1, the organic carbon is 25, 4.2 and 1.6% for A1,A/C and

No1

No2,3

No5

No4

22

C horizons, respectively. There is absence of carbonates. It is classified (WRB) as Aridic tephric Regosol. The Vlychada (No2) reaches the depth of 1 m. Four horizons have been distinguished, A (0-7 cm), A2 (7-40), C(40-68) and Ck (68-100+). The sand fraction is 79.7, 83.0, 72.7 and 71.9%, the clay one is 3.0, 2.0, 2.1 and 2.4%, the pH (1:2.5 H2O) is 7.51, 8.60, 9.07 and 9.33, the CEC is 8.10, 5.25, 5.87 and 5.26 cmocKg-1, the P olsen 17.0, 2.9, 0 and 0 mg Kg-1, the CaCO3 0.93, 0.88, 2.96 and 2.03%, the organic carbon is 1.80, 0.31, 0.45 and 0.36% for the four horizons, A, A2, C and Ck respectively. It is classified (WRB) as Aridic tephric Regosol. The profitis Ilias (No 3) is a very shallow soil too, developed on pumice parent material. Three horizons have been distinguished, A (0-7 cm), AC (7-30) and C (>30). The sand fraction is 33, 81 and 91%, the clay one 6, 4 and 6%, the pH (1:2.5 H2O) is 7.82, 8.23 and 8.92, the CEC is 12.67, 4.64 and 1.20 cmolcKg-1, the P olsen 16.7, 6.7 and 0 mg Kg-1, the CaCO3 10.12, 3.08, and 2.42%, the organic carbon is 7.09, 0.91 and 0.21% for the three horizons, A, AC and C, respectively. It is classified (WRB) as Aridic tephric Regosol. The Mitilini (No4) reaches the depth of 75 cm. Four horizons have been distinguished, A0 (2-0 cm), A1 (0-19), A3 (19-43) and C (43-73+). The sand fraction is n.e., 71, 69 and 72%, the clay one is n.e., 14, 16 and 16%, the pH (1:1 H2O) is 5.83, 6.50, 6.40 and 6.18, the CEC is 85, 15, 9 and 9 cmolcKg-1, the organic matter is 54.64, 1.49, 0.41 and 0.35% for the four horizons, AO, A1, A3 and C, respectively. It is classified (WRB) as Eutric Regosol. The Limnos (No 3) is a very shallow soil. Two horizons have been distinguished, A (0-7 cm), and C (7-17). The sand fraction is 61 and 64%, the clay one 16 and 16%, the pH (1:1 H2O) is 6.02 and 5.35, the CEC is 40 and 24 cmolckg-1, the base saturation is 37 and 59%, the organic matter is 2.73 and 0.53% for the two horizons, A and C, respectively, Sandy loam textured throughout the profile. It is classified (WRB) as Eutric Regosol. The soil developed on volcanic material in Greece seems to show quite different properties from the other volcanic soil due to climatic conditions prevailing in these regions.

23

Slovakian “Andozem” in the frame of Andosols in Europe

J. Balkovi�1, B. Juráni2 1Soil Science and Conservation Research Institute in Bratislava

2Department of Soil Science, Faculty of Natural Science, Comenius University in Bratislava Some volcanic mountains in Slovakia, namely those which are built by Neogene andesite rocks, are somewhere covered by Andosols (“Andozem” in Soil Classification System of Slovakia). The contribution deals with basic characteristics of andic properties of Slovakian profiles in the frame of European Andosols. Moreover it also deals with some specific andic properties aiming to show that andic soils in Slovakia fulfill an assumption for being classified as Andosols. We used four COST profiles of Slovakian volcanic soils (N 21 SK – N 24 SK). They are tentatively classified as Sili-Dystric Andosol (N 21 SK), Sceleti-Dystric Andosol (N 22 SK), Andic Cambisol (N 23 SK) and Fulvi-Sceleti-Dystric Andosol (N 24 SK). Basic classification attributes of studied profiles are summarized in table 1. Table 1 Basic soil properties relevant for describing andic soil profiles Prof. Hor. Corg Sio Alo Alp Feo Fep All. Fer. Pret pH

(NaF) BD Colour

% % % % % % % % % g.cm-3 wet A 10.2 0.35 1.56 1.24 0.32 0.54 1.9 0.6 98.20 10.30 0.66 10YR2/1

Bw1 2.10 0.96 3.28 0.91 0.62 0.02 8.8 1.1 99.74 11.06 0.80 7.5YR4/4 N21 SK Bw2 0.42 010 0.78 0.27 0.41 0.02 - 0.7 76.33 9.50 1.21 7.5YR4/5

A 10.8 0.04 0.68 0.67 0.98 0.58 0.2 1.7 85.53 7.93 0.69 10YR2/1 A/B 5.85 0.25 1.92 1.96 0.85 0.52 1.0 1.5 98.50 10.88 0.83 5YR 2.5/3 N22

SK Bw 1.92 0.57 2.07 0.85 0.56 0.03 4.5 1.0 97.33 10.89 0.86 10YR4/4 Ah1 7.20 0.10 0.59 0.54 0.59 0.14 0.50 1.0 65.38 8.96 0.72 10YR2/1 Ah2 4.65 0.05 0.61 0.58 0.58 0.14 0.20 1.0 68.46 9.04 0.78 10YR3/2 N23

SK Bw 2.55 0.06 0.69 0.51 0.58 0.12 0.70 1.0 69.97 9.43 0.92 10YR4.5/3 Ah1 15.9 0.03 0.39 0.20 0.54 0.30 - 0.9 61.2 7.73 0.73 10YR2/1 Ah2 12.0 0.22 1.23 1.04 0.38 0.05 1.2 0.7 98.4 10.78 0.65 10YR2/2 A/B 8.40 0.44 1.94 1.37 0.31 0.09 2.6 0.5 98.1 11.59 nd 10YR3/2 Bw 6.0 1.18 3.18 0.44 0.21 0.04 10.1 0.4 99.3 11.68 nd 10YR3/3

N24 SK

B/C 0.90 0.86 1.51 0.45 0.05 0.03 5.0 0.1 96.6 11.26 nd 10YR4/4 Notes: organic carbon content (Corg), oxalate silica, aluminium and iron (Sio, Alo, Feo), pyrophosphate aluminium and iron

(Alo, Feo), allophane 100/[(-5.1(Alo-Alp)/Sio) + 23.5]Sio (All.), ferrihydrite 1.72Fe (Fer.), exchangeable alkalinity in 1N NaF (pH(NaF)), bulk density at field moisture (BD), nd – not determined

Described profiles show a variety of andic soils in Slovakia from weakly developed Andic

Cambisols (N23SK), through “sil-andic” Andosol (N21SK) ending at well developed Fulvic Andosols (N24SK). This sequence relatively accurately describes the general andic catena in Slovakian volcanic mountains as it is schematically presented in figure 1. We can follow some general geographical rules in distribution of sil-andic and alu-andic horizons in dependence on altitude and precipitation.

Selective dissolving extractions indicate that reactive aluminium in sil-andic horizons of Slovakian Andosols shows the Al/Si ratio between 1 and 2.5, what is probably because of allophane like minerals with gibbsite admixture (Balkovi� et Bartošová, 2003). Based on the same source we can assume that organically associated reactive Al prevails in alu-andic soil horizons, where it is accompanied by “opaline” silica. These genetic rules intimately reflect the Al-solubility mechanisms and Al/Si – ion speciation estimated in horizons of Slovakian volcanic soils (Balkovi� et Slivková, 2002a). Studied soils have the effective mechanisms for specific anion sorption. Some quantification of these typical andic properties from Slovakia are presented by Balkovi� et Slivková (2002b).

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A

Bw

R

A

Bw1

Bw2

R

A

Bw1

Bw2

R

A

A/B

Bw

R

A1

Bw2

R

Bw1(A/B)

Allophanic horizon

Non-allophanic horizon

pH, base saturation

Altitude, precipitation, organic carbon content

Eutric Cambisol

AndicCambisol

Sili-DystricAndosol

Pachi-Dystric Andosol

Fulvi-DystricAndosol

WRB 1998

Fig. 1 General geographical catena of andic soils in Slovakian volcanic mountains.

We also compare Slovakian soils with andic properties with some other COST profiles of

Europe with respect to some classification criteria given by WRB ‘98. The results prove that Slovakian profiles appropriately complete a set of European database of andic soils and they represent a unique soil cover in the Central-European volcanic region of Neogene age.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Alo+1/2Feo [%]

Sio

[%

]

FranceHungaryItalyTenerifeSlovakia

Alu-andic

Sil-andic

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.0 2.0 4.0 6.0 8.0 10.0Alo+1/2Feo

Alp

/Alo

FranceHungaryItalyTenerifeSlovakia

Sil-andic

Alu-andic

Fig. 2 Slovakian COST profiles in some classification frame of European Andosols. References Balkovi�, J., and K. Slivková. 2002a. Aluminium solubility and and Al/Si-ion speciation in

volcanic soils of Slovakia. Phytopedon (Bratislava). Vol. 1., No. 1: 68-77. Balkovi�, J., and K. Slivková. 2002b. Phosphorus retention in volcanic soils of Slovakia.

Phytopedon (Bratislava). Vol. 1., No. 1: 78-85. Balkovi�, J., and M. Bartošová. 2003. Active aluminium, iron and silica in volcanic soils of

Slovakia. Phytopedon (Bratislava). Vol. 2., No. 1.: 42-50.

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Andosols in the World Reference Base for Soil Resources and their correlation within other classification systems

O.C. Spaargaren

ISRIC – World Soil Information, Wageningen, The Netherlands

WRB Andosols In the World Reference Base for Soil Resources (WRB), Andosols are defined as: soils having a vitric or andic horizon starting within 25 cm from the soil surface; and having no diagnostic horizons (unless buried deeper than 50 cm) other than a histic, fulvic, melanic, mollic, umbric, ochric, duric or cambic horizon (IUSS-ISRIC-FAO, 1998). The salient characteristic for an Andosol is the presence of a vitric or andic horizon. These horizons represent, respectively, slight and moderate weathering stages of, mainly, pyroclastic deposits. To be diagnostic, these horizons must have a minimum thickness of 30 cm. A vitric horizon has 10% or more volcanic glass and other primary minerals in its fine earth fraction (fraction less than 2 mm), and has a bulk density of more than 0.9 kg dm-3, an Alox + ½ Feox

2 of more than 0.4%, or a phosphate retention of more than 25%. The requirements

have been modified with respect to the 1998 ones (Driessen et al. (eds), 2001), because the original appeared to be unsatisfactory (properties of fresh volcanic ashes did also comply with the 1998 definition). An andic horizon, representing a more advanced stage of weathering than the vitric horizon, requires a bulk density of less than 0.9 kg dm-3, 10% or more clay, an Alox + ½ Feox of 2% or more, phosphate retention of 70% or more, and less than 10% volcanic glass in the fine earth fraction. Two subtypes of andic horizons are recognized and used to differentiate amongst the Andosols: the silandic and the aluandic horizon. Allophane and similar minerals predominate in the silandic horizon, whereas aluminium, complexed by organic acids, prevails in the aluandic horizon. The difference between the two is also reflected in the soil reaction: the silandic horizon being acid to neutral, the aluandic horizon acid to extremely acid. The initial division of Andosols, through its ranking of “qualifiers”, is based on the type of diagnostic horizon present. Soils with a vitric horizon key out first - as Vitric Andosols. Soils with a silandic horizon key out next, either as Eutrisilic Andosols (high content of exchangeable bases) or as Silic Andosols. The implication of this sequencing is that Andosols that do not meet the criteria of Vitric or (Eutri)Silic Andosols, automatically belong to the aluandic type. Therefore reference to this type is not made in further subdividing Andosols. As a second step for further division, typical horizons or properties associated with Andosols are used: melanic or fulvic horizons, and hydric (high water content) and pachic (thick surface horizons) properties. As a consequence of the first division, a Melanic Andosol will have an aluandic horizon, otherwise the soil would be classified as Melani-Silic Andosol. The next line of subdivision shows the intergrades to other reference soil groups, i.e. histic, leptic and skeletic, gleyic, mollic, duric, umbric and arenic. In cases where buried horizons occur, intergrades to Podzols (placic), Ferralsols (acroxic and vetic) and Luvisols (luvic) can be used. If other buried horizons are present, the qualifier Thapto in combination with the diagnostic name of the buried horizon is used, e.g. Thaptomelanic Vitric Andosol. Chemical characteristics appear last in the sequence of qualifiers: calcaric (calcareous), sodic (sodium-rich), dystric (low base saturation) and eutric (high base saturation). Links with other WRB reference soil groups are made through andic qualifiers in Cryosols, Gleysols, Ferralsols, Phaeozems, Alisols, Nitisols, Acrisols, Luvisols, Lixisols and

2 Alox and Feox are acid oxalate-extractable aluminium and iron, respectively (method of Blakemore et al., 1987)

26

Cambisols. In the Arenosols and Regosols, the presence of non- or only slightly weathered pyroclastic products in these soils is handled through a Tephric qualifier. Rules of qualifier use are such that conflicts or overlaps must be avoided. Consequently, Mollic, Calcaric, Sodic or Eutric Andosols do not exist because this would imply a combination of high base saturation with the acid soil conditions in aluandic types of Andosols. Similarly, Dystric Andosols would signify an overlap, low base saturation in combination with acid soil conditions. Correlation of WRB Andosols with other soil classification systems Some other systems of soil classification that have special classes for soils derived from volcanic ash are the USDA Soil Taxonomy (Soil Survey Staff, 1999), the French Référentiel Pédologique (AFES, 1995), the Chinese Soil Taxonomy (CRGCST, 2001), the Japanese Classification of Cultivated Soils (CCCS, 1996), the Russian Soil Classification (Stolbovoi, 2000), and the New Zealand Soil Classification (Hewitt, 1998). The table below provides approximate correlations of the main Andosol types:

WRB USA France China Japan Russia New Zealand

Andosols Andisols Andosols Andosols Regosols

Volcanic soils

Vitric Vitri- Great Groups

Vitrosols Vitric Andosols

Volcanogenous Regosols

Volcanics banded

Pumice soils

Silic Eutric subgroups

Silandosols Typic subgroups

Haplic subgroups

Volcanic ochre

Typic Allophanic

soils Aluandic Alic

subgroups Aluandosols Alic

subgroups Non-allophanic

subgroups (not

recognized) Acidic

Allophanic soils

References AFES (Association Française pour l’Étude du Sol). 1995. Référentiel Pédologique. INRA Éditions,

Paris. Blakemore L.C., P.L. Searle and B.K. Daly. 1987. Methods for chemical analysis of soils. N.Z. Soil

Bureau Sci. Rep. 80. Soil Bureau, Lower Hutt. CCCS (Classification Committee of Cultivated Soils). 1996. Classification of Cultivated Soils in

Japan. Third Approximation. NIAES, Tsukuba. CRGCST (Cooperative Research Group on Chinese Soil Taxonomy). 2001. Chinese Soil Taxonomy.

Science Press, Beijing. Driessen P., J. Deckers, O. Spaargaren and F. Nachtergaele (eds). 2001. Lecture notes on the major

soils of the world. World Soil Resources Reports 94. Food and Agriculture Organization of the United Nations, Rome.

Hewitt A.E. 1998. New Zealand Soil Classification. 2nd edition. Landcare Research Science Series No. 1. Manaaki Whenua Press, Lincoln, Canterbury.

IUSS-ISRIC-FAO. 1998. World Reference Base for Soil Resources. World Soil Resources Reports 84. Food and Agriculture Organization of the United Nations, Rome.

Soil Survey Staff. 1999. Soil Taxonomy. A Basic System of Soil Classification for Making and Interpreting Soil Surveys. Second Edition. Agriculture Handbook 436. USDA-NRCS, Washington.

Stolbovoi V. 2000. Soils of Russia: Correlated with the Revised Legend of the FAO Soil Map of the World and World Reference Base for Soil Resources. IIASA, Laxenburg.

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Icelandic volcanic soils

Olafur Arnalds Agricultural Research Institute (RALA), Reykjavik Iceland

Controlling factors and classification Icelandic soils, recently reviewed by Arnalds (2004), are predominantly Andosols, including many soils of deserts which are termed Vitrisols according to the RALA classification. Wind erosion is extremely active in Iceland, which leads to massive redistribution of vitric materials from desert surfaces throughout Iceland. Tephra deposition is frequent. The soil surface is generally rising as eolian materials and tephra are continuously being added to the surface. There is a clear gradient in soil properties from the active volcanic rift-zone and desert areas to the Tertiary landscapes of the east, north and west Iceland, as is indicated in Fig. 1. Rate of eolian and tephra deposition controls the pH, with sufficient release of bases to maintain the pH in areas of rapid/frequent deposition, while pH becomes lower in areas of less deposition. Soil pH controls to a large extent both allophane formation and accumulation of metal-humus complexes. Allophane does not form when pH is < 4.9 (Fig. 2a), but it occurs in subsurface horizons at such low pH because of redistribution of soil materials, and possibly changes in pH in time caused by environmental change. Much more carbon is accumulated in soils of low pH than in soils with higher pH (Fig. 2b). These relationships are used to separate Icelandic Andosols into main classes of Icelandic soils, which are indicated by the shades in Fig. 1. The classes are: Vitrisols (V), Brown Andosols (BA, freely drained Andosols, < 12% C), Gleyic Andosols (GA; Andosols of wetlands, < 12% C), Histic Andosols (HA, organic Andosols of wetlands, 12-20% C), and also Histosols (H, >20% C). Cryosols, Arenosols, and Leptosols also occur. Soil map of Iceland can be obtained from www.rala.is/desert. Icelandic soil class names are shown with italic letters in this abstract. Morphology and properties The Andosol/Histosol mantle over the 10 000 year old glaciated surfaces is commonly 0.5-2 m thick. The Andosols often show distinct layering as a result of tephra deposition and eolian events. Tephra layers are sometimes prominent, especially near the active volcanic belt. The soils are very friable, lack cohesion, and some soils show thixotropic properties. Bulk density is characteristically low and more related to carbon content than allophane as is high 15 bar water retention (30-200%). The physical properties of Icelandic soils magnify cryoturbation resulting in clear cryogenic features. The mineralogy of the soils is dominated by basaltic rock minerals and clay minerals characteristic of Andosols. Smectites and other phyllosilicates have been found in horizons influenced by sediments from the Tertiary basalt stacks (Kleber and Arnalds, unpublished). Undisturbed Icelandic soils are generally rich in OC, which can extend to >2 m depth with erratic distribution. There is a clear trend in OC which relates to the pH of the soils and distance from sources of tephra materials (Fig. 1). Soil reaction (H2O) ranges from 4 (Histosols, Histic Andosols) to >7 (Vitrisols), also depending on vitric inputs to the soils. pH(KCl) is 0.3-1.5 unit lower, with d pH closely related to pH (H2O). Vitrisols Typical Vitrisols, which are mainly associated with desert surfaces, have different character than Andosols under vegetation. Carbon and clay contents are low, they are coarse with higher BD, but lower water retention and CEC than typical Andosols. Their extent in Iceland

28

(> 20 000 km2) warrants their separation from the other Andosols. Many of the Vitrisols meet criteria for Andisols (Soil Taxonomy), but many fail to meet the depth requirements of Andosols (WRB). Vitric materials dominate their mineralogy but (Al+½Fe)o is often >0.4%. The oxalate treatment is doubted as criteria for classifying the Vitric materials globally, due to possible partial dissolution of the basaltic glass and it does not separate Icelandic soils. Icelandic Vitrisols are subjected to intense cryoturbation processes and erosion. References Arnalds, O. 2004. Volcanic soils of Iceland. Catena 56:3-20. Figure 1 Range of carbon and clay (allophane + ferrihydrite) content and pH in Icelandic soil classes. H: Histosols; HA: Histic Andosols; GA: Gleyic Andosols; BA: Brown Andosols; V: Vitric Andosols. Lines for clay and organic carbon are also reflected in Fig. 2. Figure 2 The relationships between pH (H2O) and allophane content (a) and organic content (b) in surface horizons.

pH H2O

3 4 5 6 7 8 9

% a

lloph

ane

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4

6

8

10

12

14

16

18

pH H2O

2 3 4 5 6 7 8 9

%C

0

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20

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50a) b)

clayOC

pH

H HA GA&BA V% C andallophane

10

20

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>20%C 12-20%C 1-12%C <1%C

vitric input

pH

4

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7

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30

Patterns of phyllosilicate mineralogy in COST samples

Markus Kleber1, Fernando Monteiro2, Reinhold Jahn1

1Institut für Bodenkunde und Pflanzenernährung, Martin Luther-Universität Halle - Wittenberg, Weid, Germany. 2Departamento de Ciencieas do Ambiente, Institut Superior de Agronomia/Centro de Pedologia, Lissabon,

Portugal The phyllosilicate mineralogy of selected COST samples was assessed by means of XRD. Sample preparation included removal of short range order components by acid oxalate extraction and the preparation of oriented specimen on porous ceramic tiles. COST samples may be grouped in increasing order of the abundance of phyllosilicate clay minerals: 1) absent or in traces (Iceland; Acores) 2) just discernible (Canary Islands) 3) well developed (Canary Islands) 4) dominant, short range order component missing (Hungary) XRD signals in groups 1 and 2 often appear to be broad and characterized by a low signal to noise ratio, indicating early development stages and low crystallinity. Signal intensity ratios and peak shape parameters (FWHM, full width at half maximum) are evaluated as a means to add in the understanding of pedogenesis from volcanic parent materials.

31

Extractability and FTIR characteristics of poorly-ordered minerals in a collection of volcanic ash soils

P. Buurman1, E.L. Meijer1, A. Fraser2 and E. Garcia Rodeja3

1Wageningen University (NL); 2McAuley Institute (GB); 3Santiago University (E) Volcanic ash soils are characterized by either Al-organic complexes, or by low-order aluminium silicates such as allophane and imogolite. In practice, the presence of Al- complexes or –silicates is assessed by combinations of more or less specific extractions (acid oxalate, pyrophosphate pH10, etc). Especially for aluminium silicates, the relation between the character of the extracted component and its extraction behavior is hardly known. Extractions are standardized and performed only once. At high contents of low-order Al-silicates, such extractions are incomplete. In addition, they extract unknown amounts of other minerals, such as halloysite and gibbsite, which obscures the interpretation. We undertook the present study to investigate the relation between extractability of low-order Al-silicates and factors such as total amount, Al/Si ratio, and admixed crystalline minerals. Special attention was given to the hydration state of the material and to coordination of its Si component. In general, there is a loss of oxygenated groups and a relative increase of aliphatics with depth. We measured acid-oxalate extractability and FTIR spectra of 34 samples from Costa Rica and from nine COST-622 reference profiles in four European countries. Sio, Alo, and Feo, were measured following two procedures, i.e., standard extraction and sequential extraction in 5 to 7 steps. Solid phase FTIR spectra were recorded for original samples and for residues after extraction. To obtain spectra of the extractable fraction, spectra of residues were subtracted from those of the samples before extraction. Repeated oxalate extraction removes all amorphous Al-silicates, but not necessarily all non-silicate iron phases. For this reason, also dithionite-extractable Fe (Fed, single extraction) was measured. The aim was to distinguish similarities and differences between the characteristics of (aggregates of) poorly-ordered minerals in this collection of samples. This is important for understanding the variety of physical and chemical properties of volcanic-ash soils. Many samples show characteristic decreasing yield with each subsequent extraction, but a number of anomalies were observed. Also FTIR spectra may show great similarity between samples from different origin, but mostly they show a wide range of transitions between typical mineral spectra from literature. Especially for Fe, 5-7 sequential extractions sometimes extracted more than a single dithionite extraction, probably indicating dissolution of crystalline Fe-oxides such as magnetite. Oxidation of organic matter by H2O2 to remove organic matter resulted in the formation of ammonium dioxalato aluminate, an artifact that was encountered in most spectra of this collection of volcanic-ash soil samples. We expect that this complex formed from organically-bound aluminium. It has a typical combination of adsorption bands at 1721-1700-1419-1286-805 or 1722-1699-1417-1288-808 cm-1. Another artefact is Ca-oxalate, which is visible in some FTIR spectra of residues after acid-oxalate extraction, with typical absorption bands at 1619-1318-782 cm-1. Samples that have been dried insufficiently show a peak of adsorbed water at about 1635 or 1653 cm-1. Top horizons frequently show peaks at 2924 and 2854 cm-1, due to CH2 and CH3 in organic matter that was not removed by peroxide oxidation. The allophane-type (Al/Si=2) that has a FTIR spectrum most similar to that of imogolite is called proto-imogolite. The typical difference of imogolite in comparison to proto-imogolite

32

is the splitting of the 965 cm-1 silica peak into a doublet 992-946 cm-1 and a little tendency of splitting of the 573 cm-1 alumina-band into 592-562 cm-1. Allophane-types with lower Al/Si ratios have a single silica-peak at >1000 cm-1 with a “shoulder” at <1000 cm-1, so at higher wave number than proto-imogolite, but an alumina-peak at about about the same wave number (576 cm-1). Because of the shoulder we must be aware of the possibility that the latter allophane-types consist of a mixture of proto-imogolite with polymeric silica. References Russell J.D., and Fraser T., 1994. Infrared Methods. Chapter 2 in: Wilson M.J. (Ed.), Clay

Mineralogy: Spectroscopic and Chemical Determination Methods. Chapman and Hall. ISBN 0 412 53380 4.

33

NaOH and Na4P2O7 extractable organic matter in two allophanic volcanic ash soils of the Azores Islands - a pyrolysis-GC/MS study

P. Buurman1, K.G.J. Nierop2, P.F. van Bergen3 and B. van Lagen1

1Department of Environmental Sciences, Laboratory of Soil Sciences and Geology, Wageningen University, The Netherlands.

2IBED-Physical Geography, University of Amsterdam, The Netherlands. 3Shell Global Solutions International - Amsterdam, The Netherlands.

Andosols are well known for their capacity to store organic matter. The 14C age of soil organic matter (SOM) in Andosols ranges from modern to 7000 years BP in the Ap and Ah horizons, similar to several other soil types, but increases with depth. Ages range from 5000 to 30,000 BP and even 150,000 years BP, which is a much larger mean residence time of SOM than in any other soil type (Wada and Aomine, 1973, Torn et al. 1997). Despite this notoriety of volcanic ash soils, the organic matter composition has hardly been studied at the molecular level.

Two extensively analysed soil profiles from the Azores Islands were selected for organic matter charaterization. These profiles were collected for the COST Action 622, European Volcanic Soils, which was funded by the European Commission.

Profile N5 (Ah – C – 2Ahb – 2Bw – 2BwC – 3C) consists of two superposed profile, developed in three ash layers. It is located in extensively grazed grassland on the Island of Faial, Azores. The altitude is 510 m asl, and the parent material is pyroclastic material. Temperature regime is mesic, and moisture regime is udic. The soil is tentatively classified as a Hydric, acrudoxic Fulvudand (SSS, 1999).

Profile N6 (Ah – ABw1 – ABw2 – 2Bw1 – 2Bw2 – 2Bw3) is developed in two superposed ash layers. It is located on the Island of Pico, Azores, in a plantation forest with Cryptomeria japonica with undergrowth of Pittosporum undulatum, Erica azorica, Rubus ssp, and ferns. The altitude is 400 m, and the parent material is basaltic pyroclastics. The temperature regime is mesic, and the moisture regime is udic. This profile is a Acrudoxic Hydrudand.

Samples were first extracted with 0.1 M NaOH and consecutively with 0.1 M Na4P2O7

(pH=10). The obtained extractable organic matter fractions were studied by pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). The pyrolysates of all samples were dominated by polysaccharide-derived compounds. The Na4P2O7 extractable fractions were slightly enriched by markers of lignin, chitin, proteins and lipids. Only in the topsoils (A horizons) lignin was be present in significant amounts and, notwithstanding substantial side-chain oxidation, the distribution of lignin-derived products could be related to the overlying vegetation. A similar trend was observed for lipids, especially the high abundance of C26 alkanol in profile N5 clearly reflects the grass vegetation. Below the topsoils, lignin and lipids were hardly detectable. With depth, markers of intact polysaccharides decreased relatively to smaller compounds and also in relation to chitin. The occurrence of large amounts of polysaccharides including chitin points to an important in situ production of SOM by fungi and/or arthropods.

The topsoils of both soils are not dark enough to qualify for a melanic epipedon (SSS, 1999), and they lack the very high content of char-derived) aromatic moieties that are so characteristic of such topsoils. The topsoils of the two soils were not burnt regularly.

The fact that the pyrophosphate extract is slightly enriched in lipids, lignin, chitin and proteins may have two different explanations: (1) these components are relatively strongly bound to amorphous silicates and therefore less extractable with NaOH, or (2) NaOH extracts the majority of the polysaccharides and therefore the residue after NaOH extraction is relatively enriched in the compounds other than polysaccharides. Because the two extractions

34

do not remove all organic matter from the soil, it is possible that the most strongly-bound compounds are not identified by the present approach. References Soil Survey Staff. 1999. Soil Taxonomy, a Basic System of Soil Classification for Making

and Interpreting Soil Surveys. 2d Edition, US Dept. of Agriculture, Agriculture Handbook 436. Washington D.C.

Torn, M.S., S.E. Trumbore, O.A. Chadwick, P.M. Vitousek, and D.M. Hendricks. 1997. Mineral control of soil organic carbon storage and turnover. Nature 389:170-173.

Wada, K., and S. Aomine. 1973. Soil development on volcanic material during the Quaternary. Soil Sci. 116:170-177.

35

Size and activity of the soil microbial community from a range of European volcanic soils

D.W. Hopkins1 and F. Bartoli2

1School of Biological and Environmental Sciences, University of Stirling, Scotland UK, 2Laboratoire Sols et Environnement INPL(ENSAIA)-INRA, Vandoeuvre-lès-Nancy France,

Despite previous work, biological characterisation of Andosols has not been fully explored. In this paper, we report the results of two investigations of the biological properties of volcanic soils that builds on the work of many collaborators. First, we present the results of a survey of the soil microbial biomass, respiratory activity of ten topsoils from the COST 622 reference volcanic soils of Europe (Soil Resources of European Volcanic Systems). The soils used were sampled from reference profiles in five countries (Italy, Portugal [Azores], Iceland, Spain [Tenerife] and France) with two profiles in each country. They were all Andosols (six Silic, two Aluandic and one Mollic Andosols according to the WRB classification), except one from Tenerife which was a Pachic Andic Umbrisol. Second, we report the results of detailed investigations on the mineralization of carbon in soils collected from Mt Etna, Sicily. Seven of the eight soils from Etna were also Andosols, and included soils at different stages of development in dated lava flows which we used to test two hypotheses of community development on volcanic chronosequences.

For the COST 622 volcanic topsoils, the hypothesis was that availability of soil organic matter to microorganisms decreases with increasing of Al-humus content, following the observation by Boudot (1992) that biodegradation of citric acid was low when adsorbed on poorly-ordered Al-hydroxide or Al-organic complexes, but not on allophane or imogolite. This hypothesis was not validated for the Andosols studied. First, from the soil survey the soil microbial biomass and respiration rates fell within the typical range for soils and both microbial biomass C concentration and respiration rate were positively correlated with total soil organic C (Fig. 1). Figure 1 Relationships of biomass C (a) or respiration rate (b) with soil organic C. The outliers (diamond symbols) were those from Faial[Azores] (a) and those from Tenerife (b).

Second, excluding the Faial [Azores] soil, the mean biomass C-to-soil C ratio was 1.3 % and with the Faial soil it is 1.66 %. These ratios are much larger than the extremely small biomass C-to-soil C ratios in Andosols from Japan (mean 0.2 %) reported by Murata et al. (1998) or from Costa Rica (mean 0.3 %) by Mazzarino et al. (1993). Furthermore, both biomass C-to-soil C ratio and respiration rate-to-soil C ratio were not related to Al-humus content, but were positively related to total porosity (Fig. 2), which itself was positively related to soil organic C (aggregation) and to capillary porosity (90 to 98 % of total porosity).

0

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36

Figure 2 Relationships of biomass C-to-soil C ratio (a) or respiration rate-to-soil C ratio (b) with total porosity. The excluded topsoils (lozenge symbols) were those from the Faial Fulvic Silic Andosol and the Icelandic Pachic Fulvic Silic Andosol (a) and those from Tenerife (b).

Using the soils from Mt Etna, we have determined the rates of decomposition of leaf litter in soils at different stages of development and tested two hypothesis. First, that the decomposition kinetics that the proportion of C in added plant material that would be mineralized is greater for soil microbial communities at later stages of development than at earlier stages. Experimental results indicate that the general applicability of this hypothesis depends on the source of the litter. Second, the hypothesis that the efficiency of leaf litter decomposition increases with soil development, was supported because the ratio of C mineralized from the insoluble fraction of the litter to the C mineralized from the intact litter was greater for the young soils compared with the more developed soils.

We thank Luciano Lulli and Fabio Terribile (Italy), Jorge Pinheiro and Manuel Madeira (Azores), Olafur Arnalds and Hlynur Oskarsson (Iceland), Marisa Tejedor and Jose Hernandez-Moreno (Tenerife) and Folkert van Oort and Jean Dejou (France) for the selection of the COST 622 reference profiles, Toine Jongmans (The Netherlands) and Folkert van Oort (France) for the soil and site description, Paul Quantin (France) for the WRB soil classification, Gérard Burtin and Elisabeth Schouller (France) for assistance with the physical and chemical data, and Eduardo Garcia-Rodeja (Spain) for the oxalate and pyrophosphate extractable Al, Si and Fe data. We are grateful to Luigi Badalucco, S Marco Meli and Antonio Ioppolo (Italy) for site section and description in Sicily and Lorna English (UK) for assistance with the microbial assays. References Boudot, J.P. 1992. Relative efficiency of complexed aluminium, non-crystalline Al

hydroxide, allophane and imogolite in retarding the biodegradation of citric acid. Geoderma 52: 29-39.

Mazzarino, M.J., L. Szott, and M. Jimenez. 1993. Dynamics of soil total C and N, microbial biomass, and water-soluble C in tropical agroecosystems. Soil Biol. & Bioch. 25: 205-214.

Murata, T., N. Nagaishi, R. Hamada, K. Sakagami, and T. Kato. 1998. Relationship between soil sugar composition and the amount of labile soil organic matter in andisol treated with bark compost of leaf-litter. Biology & Fertility of Soils 27: 342-348.

0

1

2

3

4

5

0,6 0,65 0,7 0,75 0,8

y = 9,144 x - 5,117 r = 0,985; p < 0,001

Total porosity (cm 3 .cm-3 )

Bio

mas

s C

/soi

l C (%

) (a)

0

250

500

750

1000

1250

0,6 0,65 0,7 0,75 0,8

y = 1172,46 x - 526,19 r = 0,769; p < 0,05

Total porosity (cm 3 .cm-3 )

Res

pira

tion

rate

(mgC

.day

-1.k

g-1

soi

l C) (b)

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Elemental composition of Reference European Volcanic Soils

A. Martínez-Cortizas, J.C. Nóvoa, X. Pontevedra and E. García-Rodeja Dept. Edafología y Química Agrícola, Facultad de Biología, Universidad de Santiago de Compostela

Within the framework of EU-COST action 622 twenty soils developed on volcanic materials from Italy (IT: N1 to N4), Azores Islands (AI: N5, N6), Iceland (IC: N7 to N9), Canary Islands (CI: N10 to N12), Greece (GR: N13, N14 N14A), France (FR: N15, N16) and Hungary (HG: N17 to N19) were described, sampled and analyzed for a large number of soil properties by different research groups. Here we describe the results of the analysis of 27 elements (Si, Al, Fe, K, Ca, Mg, Na, P, Cl, Ti, Cr, Mn, Ni, Cu, Zn, As, Se, Br, Rb, Y, Zr, Pb, Th, U, and Hg). Subsamples from each soil horizon were air dried and homogenized, and all elements except for Hg were determined by XRF analysis. Mercury was measured with a LECO-ALTEC AMA-354 Hg analyzer, which is a single-purpose atomic absorption spectrophotometer for solid and liquid samples. No sample pretreatment was done for any of the determinations. In general terms each volcanic area showed a specific elemental composition (Table 1). For example, Italian soils have the highest K, As, Rb, Sr, Pb, Th and U and the lowest Mg, Ti, Cr, and Fe concentrations of all soils; soils from Azores are very rich in Mn, Fe, Br and Hg and the poorest in Si, Ca, and Sr; Icelandic soils have the highest Mg, Cu, Zn and Y and the lowest, K, As, Rb, Pb and Th concentrations; soils from the Canary Islands are the richest in Al, Ti, Cr, Ni, Ga, and Zr and the poorest in Na; Greek soils are rich in Si, Na and Ca and poor in metallic elements; while soils from France and Hungary have intermediate concentrations for almost all elements. The most similar soils are those from Azores Islands and Canary Islands, due to their richness in many metallic elements (Al, Ti, Cr, Fe, Ni, Zn, Ga). This similarity is confirmed by PCA analysis, since the horizons for soils N5, N6, N10, N11 and N12 plot very close in the axis projections. Table 1 Relative elemental composition of soils from the different volcanic areas. Values between parenthesis are the maximum (rich) and the minimum (poor) average concentrations. (Si, Al, Ca, Mg, Na, K, P, Cl, Ti and Fe are in % and the rest of the elements in µg g-1 except for Hg which is in ng g-1). Volcanic area Rich Poor ITALY K (5.3), As (24.5), Rb (282), Sr (613),

Pb (81.4), Th (48.3), U (15) Mg (0.5), P, Ti (0.4), Cr (<d.l.), Mn, Fe (2.7), Ni, Zn

AZORES Is. Al, Mg, P, Ti, Cr, Mn (3039), Fe (10), Ni, Zn, Ga, Br (362), Hg (216)

Si (13.1), Ca (1.0), Sr (157), Pb

ICELAND Ca, Mg (1.2), Mn, Cu (75.5), Zn (128), Y (44.8)

K (1.0), As (<d.l.), Rb (17.6), Pb (0.9), Th (2.9)

CANARY Is. Al (14.4), Ti (3.9), Cr (470), Fe, Ni (125), Zn, Ga (33.2), As, Br, Zr (699), Th, Hg

Na (0.7)

GREECE Si (28.2), Na (2.3), Ca (3.5) Al (7.9), P (<d.l.), Ti, Mn (707), Fe, Ni (8.2), Cu, Zn (60), Ga, As, Br, Sr, Y, Zr (179), Hg (11.9)

FRANCE P (0.7), Sr Si, K, Rb, Y (22.1), Zr, Th HUNGARY Si, Mg, Rb, Pb Al, Na, Ca, Cu (27.4), Ga (14), Br (6.5),

Y

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Of the major elements analyzed, Si showed negative correlations to Fe, Ti, Cr, Zn and P, and positive correlations to Na, K and Rb. Aluminium showed large positive correlations to Fe, Ti, Mn, Ni, Ga, Sr (N1 to N4), Zr, Th, and U. A combination of PCA and cluster analysis also revealed geochemical discontinuities in most of the soil profiles, in agreement with their complex stratigraphy. Some soils show major geochemical discontinuities, as for example N1, N5, N7, N8, N9, N10 and N11; while a few of them showed a more homogeneous elemental composition throughout the soil profiles (N12, N13, N16, N17, N18, N19)

Table 2 Geochemical discontinuities (vertical bars between horizons) in the soil profiles Volcanic area Soils ITALY IT-N1 Ap-Bw1-Bw2 | BC-C IT-N2 O-A1 || BC1-BC2-C1

IT-N3 O | A1-A2-AB-Bw1-Bw2 IT-N4 O | A1-A2-A3 | Bw1-Bw2 AZORES Is. AÇ-N5 A1 || 2A-2B2-Bw/C || 2C1

AÇ-N6 A-ABw-2AB | 2Bw1-2Bw2-2Bw3 ICELAND IC-N7 O-A1|| A2 || A3-Bw1-Bw2-Bw3 || 2BCg

IC-N8 A1-A2-Bw1|| 2Bw || 3Bw-4C IC-N9 A1-H1|| C || 2H CANARY Is. CI-N10 A1| Bw1-Bw2 || Bw3|| Bw4

CI-N11 A1| C1 || 2Bw-2BC CI-12 A1-A2-Bw-2A1b GREECE GR-N13 A1-A2-C-Ck Gr-N14 A | AC-C GR-N14a Ah | C FRANCE FR-N15 Ah2-Ah3 | Bw-C/R-R/C Bw-C/R-R/C | R/C

FR-N16 Ah1-Ah2-Ah3-Bw1-2Bw HUNGARY HU-17 Ah1-Ah2-AC HU-N18 Ah1-Ah2A+R HU-N19 Ah1-Ah2-Bw+R

These results suggest that the elemental composition of the European volcanic soils

analyzed here is largely dependent on the parent material original mineralogy, a result already suggested in previous studies (Buurman et al., 2003; Martínez Cortizas et al., 2003). But also as found by Martínez Cortizas et al (2003) pedogenesis, organic matter content, climate conditions and soil management by man are other important factors in the distribution of some elements.

Very mobile elements (Ca, K, Sr) and even Zr, Th and U seem to have been leached in the most evolved horizons and soils; while Cu, Zn, Pb and Hg show elevated concentrations in the organic rich horizons, suggesting a role of the organic matter in their retention in the soils. On the other hand, Br is more dependent on its external source (the ocean) and the dominant climatic conditions, since the highest concentrations are found in the more oceanic (Azores) and rainy areas (as it happens for the Italian soils). Finally, the degree of enrichment in Cu, Pb and Hg in some soils (as for example N1, and orchard soil) indicates that soil management (i.e. fertilization and use of biocides) and atmospheric metal pollution are also significant sources of some elements. References Buurman, P., García-Rodeja, E., Martínez Cortizas, A., and van Doesburg, J.D.J. 2003.

Stratification of parent material in European volcanic and related soils studied by laser-diffraction grain-sizing and chemical analysis. Catena, 56: 127-144.

Martínez Cortizas, A., García-Rodeja, E., Nóvoa Muñoz, J.C., Pontevedra Pombal, X., Buurman, P., and Terribile, F. 2003. Distribution of some selected major and trace elements in four Italian soils developed from the deposits of the Gauro ad Vico volcanoes. Geoderma, 117: 215-224.

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40

Complex exchange properties of soils from a range of European volcanic areas

M. Madeira1, F. Monteiro1, E. García-Rodeja2 & J. C. Nóvoa-Moñoz2

1 Departamento de Ciências do Ambiente, Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal; 2 Departamento de Edafología y Química Agrícola, Fac. Biología, University of Santiago de

Compostela, Campus Sur s/n, 15782 Santiago de Compostela, Spain.

Most Andisols contain large amounts of pH-dependent charge, which influence the majority of the reactions which control the ability of the soil to retain cations and anions. The influence of the pH-dependent charge components on the cation exchange capacity (CEC) and the anion exchange capacity (AEC) is of considerable importance for the successful management of Andisols. The CEC measured by the 1 M NH4OAc at pH 7 is commonly used and has become a standard reference to which other methods are compared. The values of the sum of bases by 1 M NH4OAc at pH 7 are used to establish criteria for taxonomic separation of Andisols at the sub-group level.

Hence a study on a wide range of Andisols and related soils from European volcanic areas was conducted to determine (1) the CEC and the AEC, (2) the base exchange cations and the effective cation exchange capacity (ECEC), and (3) the influence of various components of the soil colloidal systems on CEC and AEC values. Seventeen pedons of Andisols (of the COST 622 reference soils of Europe; Soil Resources of European Volcanic Systems) selected from representative volcanic areas of Italy, Portugal (Azores), Iceland, Spain (Tenerife), Greece, France and Hungary were used. Determinations were done on the fine earth fraction (<2mm) of air-dried samples. The results are expressed on an oven dry basis (1050C). The CEC was determined by the 1 M NH4OAc method (SM), using continuous leaching of 5 g of soil with 100 mL of 1 M NH4OAc. The leachate was used to determine the exchangeable bases, measured using the atomic absorption spectroscopy. The CEC was also measured by the compulsive exchange method (CE), and AEC was also measured by the same method (Gillman & Sumpter, 1986). The ECEC was calculated by taking the values of the sum of bases plus the 1 M KCl extractable Al. For presentation, data of Andisols and non-Andisols are shown separately.

The CEC values of Andisols measured by the SM showed a wide variation (17.64-89.30 cmolc kg-1) and were higher in the Andisols very rich in organic C than in the other soils. Those values were positively correlated with the organic C content (r=0,82; p<0.01); the correlation between CECSM and Alo content was not observed. In the other soils (non-Andisols), CECSM values varied between 4.64 and 62.64 cmolc kg-1. The values were weakly correlated with organic C content (r=0.58; p<0.05), and strongly correlated with the Alo content (r=0.83; p<0.01). The ECEC values (as the sum of basic exchangeable cations and extractable Al) of Andisols were positively correlated with the organic C content (r=0.77; p<0.01) and negatively with Alo content (r=-0.72; p<0.05).

For Andisols, CECCE values were much lower than those obtained by the SM, especially in Andisols very rich in organic C. Similar trend was observed for non-Andisols. The values by the two methods were not correlated. Those values varied from 0.20 to 21.55 cmolc kg-1, for Andisols, and from 1.30 to 26.77 cmolc kg-1, for non-Andisols. CECCE values were not correlated with Alo and organic C contents. Values of Andisols were positively correlated with ECEC values obtained by the SM (r=0.70; p<0.05); this correlation was also observed for the non-Andisols (r=0.69; p<0.01).

The difference between CECSM and CECCE (∆CEC) increases with increasing content of a variable charge constituents (i.e. organic matter and allophanic constituents). The values of Andisols showed a wide variation (about 10 to 68), and the highest values were observed in

41

the Acrudoxic Hydrudands (Azores). This is in agreement with results reported by Madeira et al. (2003) for Andisols from the Azores. The values in Andisols were positively correlated with both organic C (r=0.56; p<0.05) and Alo (r=0.68; p<0.05) contents.

The values of CEC by the SM of the Andisols Ah horizons were positively correlated with the organic C content (r=0.82; p<0.01), but not with the Alo content. For B horizons, the correlation of those values with Alo content was stronger (r=0.77; p<0.01) than with organic C content (r=0.64; p<0.05). Similar trend was observed for ∆CEC values (r=0.86; p<0.01; r=0.60; p<0.05). Values of ECEC of subsurface horizons were negatively correlated (r=-0.73; p<0.01) with Alo content.

The values of exchangeable Ca were strongly variable among studied soils. Andisols with high allophane content (and/or organic C contents), that is, Typic Hapludands and Acrudoxic Hydrudands (Azores), and Alic Hapludands (France) showed the lowest values, especially in the Bw horizons (0.40-0.56 cmolc kg-1). Similar pattern was observed for the exchangeable Mg. These data corroborates results reported by Madeira et al. (2003) for Andisols from Azores. Non-Andisols mostly showed higher contents of exchangeable Ca and Mg than Andisols. Exchangeable K was very high in both Andisols (0.84-4.74 cmolc kg-1) and non-Andisols (6.76-23.70 cmolc kg-1) from Italy; additionally, values in Andisols were mostly lower than in non-Andisols. Extractable Al showed high values (3.89-7.60 cmolc kg-1) in the surface horizons of Andisols from the Azores (both Haplic Hapludands and Acrudoxic Hydrudands) and France (Alic Hapludands).

The values of anion exchange capacity (AEC) determined by the CE, that is, at field pH conditions, showed strong differences according to soil types. Those values were very low (<0.54 cmolc kg-1) or null for non-Andisols. Values for Andisols varied from 0.25-0.84 cmolc kg-1 (Eutric Fulvudands) to 4.09-15.45 cmolc kg-1 (Acrudoxic Hydrudands). Correlations between the AEC values and the organic C and Alo contents were not observed. The ratio AEC/CECCE was generally less than one; this ratio was greater than 1 in Andisols from the Azores, and in most of the horizons of Andisols from France.

Authors thank Fabio Terribili (Italy), Jorge Pinheiro (Azores, Olafur Arnalds and Hlynur Oskarsson (Iceland), Marisa Tejedor and José Hernandez-Moreno (Tenerife), A. Economou (Greece), Toine Jongmans and Peter Buurman (The Netherlands), Folkert Van Oort, Paul Quintin and Martine Gérard (France), G. Fuleky, A Kertesz, B Marasz and O. Feher (Hungary) for the selection of COST 622 profiles and/or the soil and site description, Otto Spaargaren for Soil Classification (Soil Taxonomy), and Isabel Meireles and Ana Batista for technical assistance.

References Gillman, G. P. and Sumpter, E. A. 1986. Modification to the compulsive exchange method for

measuring exchange characteristics of soils. Australian Journal of Soil Research 24: 173-192.

M. Madeira, E. Auxtero and E. Sousa 2003.Cation and anion exchange properties of Andisols from the Azores, Portugal, as determined by the compulsive exchange and the ammonium acetate methods. Geoderma 117: 225-241.

42

Heavy metal ad- and desorption of andic and non-andic horizons

R. Jahn and H. Tanneberg Institute of Soil Science & Plant Nutrition, Univ. of Halle, Germany

Introduction Andosols have a high binding capacity for heavy metals which may be naturally accumulated or anthropogenically derived. These metals are bound in mineral structures, on mineral surfaces, and complexed by organic matter. Some trace elements may be so strongly bound that they become unavailable to plants. But in this respect, information is very scarce, but extremely important for environmental protection. The dominance of variable charge sites in Andosols has driven us to study the pH-depended sorption and desorption of trace elements. Materials and Methods Horizons of COST- profiles of Italy (EUR01, Humi-Tephric Regosol (Eutric); EUR03, Fulvi-

Silandic Andosol (Dystric)) and the Azores (EUR06, Hydri-Silandic Andosol (Umbric and Acroxic)) were selected based on distinct differences of contents in organic matter and short range ordered minerals (see Tab. 1). For comparison, an Ap-horizon of a Siltic Chernozem (Germany) without short range ordered minerals was also included in the study. Sorption kinetics as well as adsorption and desorption studies was done in accordance with the OECD Guideline 106. For the sorption and the desorption studies, modifications in the methodo-logy was done due to limited availability of materials. For sorption kinetics 2g soil

(based on dry weight) was added with 50 ml 0.01 M Ca(NO3)2 solution containing 300 mg of Cd, Pb, Cu, Ni, and Cr as chloride. At an interval of 10 to 4 days, 0.4 ml solution was taken for the determination of sorbed metals. The sorption behaviour was evaluated by Batch procedure (48 hours) at the pH value of the soil as well as in soil samples with pH adjusted to pH 4 and pH 7. The concentration of the heavy metals in the M Ca(NO3)2 solution occurred between 1 and 2000 mg L-1. Desorption was evaluated on the samples with the highest metal loading. The samples were shaken in 20 ml M Ca(NO3)2 solution 10 times. Quantification of the metal concentration was done by flame-atomic absorption spectrophotometry and inductively coupled plasma. Results From the sorption kinetics it can be concluded that in all samples the sorption of trace elements is governed by ion association, ion exchange and rapid sorption within a few hours. After only 30 minutes, 75 % Cd, 90 % Pb, 65 % Cu and 75 % Ni of the existing amount were sorbed. It was only with Cr that sorption was found slower. The sorption capacity of the individual horizons varied, was also dependent on the kind of metal and was generally high. Without any exception no clear maximum of sorption was reached up to a maximum concen-tration of 2000 mg L-1 in the solution. The Ap horizon of the Chernozem showed the strongest

Tab. 1 Selected data of the investigated soil samples (COST-data)

Soil Depth Hor. pH Corg Allophane cm KCl % % (Sio · 7.1) EUR01 0-16 Ap 4.7 2.7 0.7 EUR01 54-95 Bw2 5.2 0.7 0.5 EUR03 0-22 A1 4.9 6.7 7.7 EUR03 48-70 AB 5.4 2.1 13.4 EUR03 98-125 Bw2 5.5 0.6 13.2 EUR06 0-20 Ah 4.6 19.1 6.4 EUR06 40-60 2AB 5.4 11.0 15.1 EUR06 100-120 2Bw3 5.7 4.5 25.6 Chernozem 0-24 Ap 7.5 2.0 0.0

43

heavy metal sorption (at a heavy metal presence of 7.5 g per kg soil and ambient soil pH) while the subsoil of the Andosol N3 showed the weakes. When one considers the horizons with high allophane content, no unique influence can be observed. The subsoil with the second highest allophane content (EUR03Bw2) is also the horizon with the lowest sorption capacity. Values of the adsorption studies were for Cd fitted into the Freundlich isotherm and from it the adsorption constant KF was calculated. In the case of Pb, Cu and Cr, sorption was especially very strong at pH 7 such that no isotherm calculation could be done. Regarding Cd, no correlation was observed between the KF values and the allophane content of the soils. In contrast, a high correlation was observed between KF and pH value. In general, a contradictory results behaviour of the horizons studied was noted. In EUR03 sorption capa-city increased systematically with Corg content (Fig. 1 right) while in EUR01 and EUR06 no fundamental difference between the horizons existed (Fig. 1 left; for EUR06 not all horizons are shown). The Freundlich desorption isotherms were always higher than for adsorption. Thus, it can be said that sorption processes are not fully reversible.

Fig. 1 Cd-adsorption and desorption isotherms of the selected horizons (soil pH) Fig. 2 shows a very strong effect of pH values and is most prominent for Cd and Ni. At pH 7, strong fixation occurred for the horizons of profile EUR06 such that Freundlich isotherm for the AB2 could not be determined. The sorption of Cr and Pb are only less affected by pH

changes. At the pH of the soils, the horizons varied in their sorption capacity. The highest was the concentration of Cd in the equilibrium solution at pH 4. At this point, sorption capacity increased with the Corg content of the horizons. The subsoil horizons of the Andosol containing high amounts of allophane had much lower sorption capacity at pH 4 compared to the Ah horizon. Fig. 2 Cd-adsorption isotherms at different pH

Conclusions Volcanic soils exhibit a very high sorption capacity for heavy metals. In particular, they exhibit strong sorption of copper, lead and chromium. The sorption of Cd and Ni is strongly pH dependent. A relation of the sorption as well as of the desorption behaviour to the content of allophane was not found. The high sorption capacity is mostly caused by organic matter.

equilibrium solution [mg Cd L -1]0 20 40 60 80 100 120 140

Cd

sorb

ed [g

kg-1

]

0.0

0.5

1.0

1.5

2.0

2.5

CHAp

06Ah

01Bw201Ap

equilibrium solution [mg Cd L -1]0 20 40 60 80 100 120 140

Cd

sorb

ed [g

kg-1

]

0.0

0.5

1.0

1.5

2.0

2.5

03Ah1

03AB

03Bw2

EUR03EUR01EUR06CH

0 50 100 150 200

Ah

AB2

2Bw30.0

1.0

2.0

3.0Ah

2Bw3AB2

Ah

2Bw3

pH 7ambient-pH

pH 4

equilibrium solution [mg Cd L -1]

Cd

sorb

ed [g

kg-1

]

EUR06

44

BCR sequential extraction of trace elements in COST-622 soils

M. Espino-Mesa., J.I. Rodriguez, and J.M. Hernandez-Moreno

Dept. Edafología-Geología, Universidad de La Laguna (ULL)

In soils and other natural systems, the mobility, transport, and partitioning of trace elements are dependent on their chemical form. Chemical extraction is employed to assess operationally defined metal fractions, which can be related to chemical species, as well to potentially mobile, bioavailable, or ecotoxic phases. Sequential extraction has been applied using extractants with progressively increasing extraction capacity. The selectivity of many extractants is weak or not sufficiently understood, and it is questionable as to whether specific trace metal compounds actually exist and can be selectively removed from multicomponent systems. For purposes of comparability and quality control, the Community Bureau of Reference (BCR, now Standards, Measurements and Testing Program) has launched a program to harmonize sequential extractions schemes for the determination of extractable trace metals in sediments. BCR has proposed a standardized 3-step extraction procedure (BCR EUR 14763 EN). This procedure is currently used and evaluated also as an extraction method for soils (1,2).

In this work, the BCR sequential extraction scheme was studied in some COST-622 profiles from Italy (IT), Portugal (AZ), Iceland (IS) and Spain (TFE). A modified BCR sequential extraction (1) was applied: extraction-1: 0.11 mol L-1 Acetic Acid, extraction-2: 0.5 mol L-1

Hydroxylammmonium Chloride, extraction-3: 8.8 mol L-1 Hydrogen peroxide digestion and extraction with 1 mol L-1 Ammonium Acetate. Residue from the third step, extraction-4: Aqua Regia (AR). The sum of extractions 1, 2, and 3 are considered the potentially mobilizable (PM) pool of an element. An independent extraction with AR was performed to determine the “pseudototal” content. A certified reference material (BCR) was used for quality control purposes.

Total-AR metal contents were compared with total values (FRX) from the COST-622 soil database. Strong correlations were observed for Cu, Ni and Cr, total-AR representing about 70% of the total content for Cu and Ni and only about 10% for Cr. Total metal contents generally agreed with soil lithology. Values greater than “Maximum Allowable Concentrations” were observed in IT samples. High values of Ni and Cr were also observed in some AZ and TFE samples.

The metal distribution (mg Kg-1) in the four extractions are shown in fig 1 for Zn and Cu. Only for these elements a significant amount was obtained in extractions 1 and 2. In the case of Cu the PM pool was more important in relation to the residual form than for Zn. In IT samples, PM forms of Cu were predominant; this, together with the high total Cu values and soil lithology points to anthropogenic contamination. Chromium was only detected from extraction 3; Ni and Pb were mostly residual.

The relative metal distribution also varied with horizon type for each element. Only in the case of Mn (Ext-1), a monotonic decrease with depth was observed.

An important dissolution of Al, Fe, and Mn occurred already from the first extraction (e.g., Al in extraction-1 ranged from 3000 mg Kg-1 in AZ to 180 mg Kg-1 in IT). The amount of Al in the first three extractions exceeded Alo values. This is a peculiar behaviour of the Andic soils which has to be considered when interpreting sequential extractions; for example, less bioavailability of the “exchangeable” forms can be expected in relation to other soil types.

45

coun

try c

ode

AZ

IS

IT

TF

Mean Zn

120100806040200

Extraction

4

3

2

1 coun

try c

ode

AZ

IS

IT

TF

Mean Cu

160140120100806040200

Extraction

4

3

2

1

Figure 1 In conclusion, considering the results obtained and the increasing work on the evaluation of the BCR sequential extraction for soils, this procedure seems a promising tool in both pedological and environmental studies of volcanic soils.

References Rauret, G., J.F. Lopez-Sanchez, A. Sahuquillo, R. Rubio, C. Davidson, A. Ure, and Ph.

Quevauviller 1999. Improvementof the BCR three-step sequential extraction procedure prior to the certification of new sediment and soil reference materials. J. Environ. Monit. 1, 57–61.

Pueyo M., J. Sastre, E. Hernandez, M. Vidal, J. F. Lopez-Sanchez, and G. Rauret. 2003. Prediction of Trace Element Mobility in Contaminated Soils by Sequential Extraction J. Environ. Qual. 32:2054–2066

46

Trace element pollution in Italian volcanic soils: the case study of the Solofrana river valley

P. Adamo1, A. Basile2, C. Colombo3, R. D’Ascoli4, R. De Mascellis2, L. Gianfreda1,

L. Landi5, M.A. Rao1, G. Renella5, F.A. Rutigliano4, F. Terribile1, M. Zampella1 1Department of Soil, Plant and Environmental Sciences, University of Naples Federico II; 2 Institute for

Mediterranean Agricultural and Forest Systems, CNR, Ercolano (NA); 3 Department of Animal, Plant and Environmental Sciences, University of Molise; 4Department of Environmental Sciences, Second University of

Naples; 5Deparment of Soil Science and Plant Nutrition, University of Florence The Solofrana river valley is an agriculture based area of southern Italy characterised by a huge concentration of tanning plants (∼160). Despite the recently observed decline in Cr content in river water (Adamo et al., 2001) the soils from the valley still contain this and other trace elements in concentrations above usual levels, mainly as a consequence of the long use of the polluted river waters as a source of irrigation, of the frequent river overflow as well of the widespread use of metal-rich agricultural materials. The high metal retention properties of the volcanic soils of the valley might play a key role to maintain the elements in soil for a long time. A suspect that an increase of soil contamination could cause severe damage to crops suggested soils have to be supervised (Adamo et al., 2003).

A multidisciplinary study, taking into consideration pedoenvironmental, micromorfological, chemical, hydrological, biological and microbiological analyses, was carried out in 2001 restricting attention to overflooded soils. Crossing in a GIS environment different land information (soil, hydrology, flood and land use maps) three study sites of about 700 m2 with the same soil type, Humic Haplustand (Soil Survey Staff, 1998), not cultivated by 5 years and affected by different numbers of floods were selected: 1) E1, flooded in 1981; 2) E2, flooded in 1981 and 1993; 3) E3, flooded in 1981, 1993 and 1998. At the E3 site, flooded again in 2002, soil and sediments were sampled soon after the event as E4 site. A site without flooding (C site) as control was also individuated. The selection of not cultivated sites was produced in order to avoid the influence of agriculture treatments over microbe activities, hindering the influence of the trace metals.

Pedological profiles were opened on the two extreme cases: P1, the not polluted control site (C site), and P2, the site subjected to 3 flood events (E3 site). Soil sampling was carried out following different operative methods and at different depths, according to the analyses to be performed.

Soils were classified as sandy-loam (clay content 127-205 g kg-1), with neutral-subalkaline pH according with carbonates presence. All the soils had a good amount of organic C (23-52 g kg-1), total N (2.2-4.1 g kg-1) and available P (19-45 mg kg-1). In general, soil properties showed some grade of variability, especially in E3 and E4 soils, probably because of the disturb caused from the recent overflowing events.

Copper and Chromium were the main soil contaminants: their total content in many cases was higher than the limits established by the current Italian legislation (DL 92/99: Cu 100 mg kg-1; DM 471/99: Cu 120, Cr 150 mg kg-1). The distribution of total content among studied soils suggested for Cu and Cr different sources. Only Cr accumulation was related to overflowing events. Cu accumulation was most likely attributable to past agricultural use of fertilizers and pesticides.

Sequential chemical extractions indicated for all polluted soils preferential association of Cr and Cu with oxidizable forms, whereas in non polluted soils both elements mostly occurred in residual mineral forms of a silicate and oxide nature. For both metals the soluble and exchangeable forms made always a small contribution to the total. Significant amounts of Cr and Cu were recovered in the acid ammonium oxalate extraction, suggesting association of

47

metals with short-range-order aluminosilicates and organo-mineral complexes. Cr(III) isotherm adsorption curves obtained at pH 6 were adequately described by the Langmuir equation and showed significative difference between control and flodded soils. High adsorption capacity of Cr(III) ions from aqueous solutions on the control and flooded E3 soil was observed. A significant presence of short-range ordered mineral phases, shown by selective chemical extractons and by the x-ray diffractometry of the clay fraction, was likely involved in soil metal retention.

Total microbial biomass and fungal mycelium were generally higher in soil E1. Similarly, in this soil was observed the greatest bacterial diversity, as compared to soils E2 and E3. In terms of bacteria community similarity (Sørensen index) the studied soils could be ranked as follow: C ≈ E1 ≈ E2 ≈ E3. Only some of the measured enzymatic activities (acid phosphatase, arylsulphatase, β-glucosidase, dehydrogenase) decreased with the number of flooding events, whereas others (urease and FDA hydrolase) were not changed or increased. In some cases the control soil showed lower enzymatic activities than those of flooded soils. The high metal content of soils did not appear to have a predominant influence on the studied biological and biochemical parameters possibly as a result of both low metal mobility and high C content. Infact, soil E4 sampled immediately after a new flooding event, although its high Cr content (536 mg kg-1), had higher biological and biochemical activities. The large input of Cr from the sediments (1012 mg kg-1) was masked by their high levels of organic carbon (61 g kg-1). Soil hydraulic properties and solute transport behaviour, determined by the Wind’s method and by a miscible flow experiment on P1 and P2 profiles, confirmed the high Cr(III) retention capacity of the soil with high values of dispersivity and showed occurrence of preferential flow paths. The analysis of the soil water retention curves showed a decrease of large pores in the flooded soil compared to control. Frequent occurrence of clay and silt coatings along elongated pores in the surface and subsurface soil horizons was showed by optical microscopy observations. This suggested a possible transfer of metal-rich sediments along the soil pore network during water movement. References Adamo, P., M. Arienzo, M.R. Bianco, P. Violante. 2001. Impact of land use and urban runoff

on the contamination of the Sarno river basin in Southwestern Italy. Water, Air and Soil Pollution 131: 36-45.

Adamo, P., L. Denaix, F. Terribile, M. Zampella. 2003. Characterization of heavy metals in contaminated volcanic soils of the Solofrana river valley (southern Italy). Geoderma 2027: 1-25

Soil Survey Staff. 1998. Keys to soil Taxonomy. United States Department of Agriculture Natural Resources Conservation Service (USDA). Washington, pp. 22-23

48

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49

Shrinkage and drainage in undisturbed soil cores and aggregates from a range of European volcanic soils

F. Bartoli

Laboratoire Sols et Environnement INPL(ENSAIA)-INRA, Vandoeuvre-lès-Nancy France,

Andosols are characterized by their large retention capacities due to their large capillary porosities (low bulk densities). Despite previous work, shrinkage of Andosols has not been fully explored. Shrinkage of fine-grained soils on drying is caused by movements of microaggregates as a result of pore-water tension developed by capillary menisci. Our hypothesis was therefore as follows: the intensity of the shrinkage process occurring in undisturbed Andosol horizons varies as a function of their initial capillary porosities. We widely validated this hypothesis. We present the results of shrinkage and drainage on controlled drying of either undisturbed soil cores or aggregate counterparts from four Ah-Bw horizon couples and one H1 horizon from five of the COST 622 reference volcanic soils of Europe (Soil Resources of European Volcanic Systems). The soils used were all Andosols: one Fulvic Silic and one Pachic Hydric Aluandic from Azores Islands, Portugal, one Molli Silic and one Pachic Fulvic Silic from Iceland, and one Silic from Tenerife Island, Spain, according to the WRB classification. Undisturbed wet soil cores of 28.6 cm3 (2.7 cm diameter, 5 cm height) were sampled. In the laboratory, these soil cores were submitted to capillary rise for 48 h and to controlled 40°C drying kinetics for 39 to 51 hours thereafter, with regular (mostly each hour) measurements of both total soil volume and volumetric soil moisture. The main results are as follows. Total volumetric shrinkage of the soils was clearly controlled by initial capillary porosity (Fig. 1a), which was in its turn controlled by the proportion of organo-mineral clay (Fig. 1b), determined by the Na resin method (Bartoli et al., 1991) and which concentrated most of allophane, ferrrihydrite, Al-humus and organic coatings, key microaggregative soil constituents (Bartoli et al., unpublished results).

Figure 1 Relationships between initial capillary porosity and total volumetric shrinkage (on 40°C controlled drying kinetics) (a) or clay content (b). N5, N6, N8 and N10 Andosols were those from Faial, Pico (Azores Islands), Iceland and Tenerife Island, respectively. The N9 H1 horizon, rich in organic C (21.8 %), belongs to a Pachic Fulvic Silic Andosol from Iceland. Shrinkage was also more pronounced for the Bw horizons than for their topsoil counterparts (Fig. 1a). Furthemore, our results show inter-relationships between weathering intensity (clay content) in the Bw horizons, development of capillary porosity (microaggregation) and sensibility to shrinkage, with a positive gradient from the Icelandic Andosol to the Azores

0

20

40

60

80

0,6 0,65 0,7 0,75 0,8 0,85 0,9

y = 297,16 x - 179,69 r = 0,920, p < 0,001

Initial capillary porosity (cm 3 .cm -3 )

Tota

l shr

inka

ge (%

)

(a)

0,6

0,65

0,7

0,75

0,8

0,85

0,9

20 30 40 50 60 70

y = 0,006 x + 0,437 r = 0,921, p < 0,001

H1

Bw

Ah

Bw

Ah

Bw

Ah

Bw

Ah

Initi

al c

apill

ary

poro

sity

(cm

3.c

m-3

)

Organo-mineral clay (%)

������

������

����

���� �

����

(b)

50

ones (Fig. 1), from Cryic-Frigid/Udic to Mesic/Udic temperature/moisture regime, respectively.

Many changes in physical properties are associated with this change of void volume; for example, proportion of water-stable aggregates was negatively related to their porosities for of the 40°C dried soils whereas this relationship was only a tendency for their wet soil counterparts (Fig. 2a). Furthermore, an increase of water-stable aggregates occurred when the wet soils were 40°C dried. This was related to total volumetric shrinkage (Fig. 2b).

Figure 2 Relationships between proportion of > 200 µm water-stable aggregates and total porosity for both the wet soils and their 40°C dried soil counterparts (a) and between the increase of water-stable aggregates occurring during drying and total volumetric shrinkage (see Fig. 1 for symbols legend). Large and small symbols of figure 2a correspond to the wet soils and to their 40°C dried soil counterparts, respectively. Finally, the drainage and shrinkage kinetics, and the shrinkage curves will be also discussed as well as complementary results obtained on wet aggregates (bulk wet soil sampled in plastic bags and stored at 4°C thereafter) using the new approach, recently designed by Poulenard et al. (2002), combining mercury porosimetry and vacuum drying kinetics. We thank Jorge Pinheiro and Manuel Madeira (Azores), Olafur Arnalds and Hlynur Oskarsson (Iceland), Marisa Tejedor and Jose Hernandez-Moreno (Tenerife) for the selection of the COST 622 reference profiles, Toine Jongmans (The Netherlands) and Folkert van Oort (France) for the soil and site description, Paul Quantin (France) for the WRB soil classification, Elisabeth Schouller and Gérard Burtin (France) for technical assistance. References Bartoli, F., Burtin, G. and Herbillon, A. J. 1991. Disaggregation and clay dispersion of

Oxisols: Na resin, a recommended methodology. Geoderma 49: 301-317. Poulenard, J., Bartoli, F. and Burtin, G. 2002. Shrinkage and drainage in aggregates of

volcanic soils: a new approach combining mercury porosimetry and vacuum drying kinetics. European Journal of Soil Science 53: 563-574.

0

25

50

75

100

0 0,2 0,4 0,6 0,8 1

y = -136,31 x + 120,99 r = 0,880, p < 0,005

Total porosity (cm 3 .cm -3 )of wet (field) or 40°C dried soils

(a)

Wat

er-s

tabl

e ag

greg

ates

(% 1

05°C

dri

ed s

oil)

of w

et (f

ield

) or

40°C

dri

ed s

oils

0

20

40

60

80

0 20 40 60 80

y = 0,945 x - 3,561 r = 0,947, p < 0,001

Total shrinkage (%)

Incr

ease

of

wat

er-s

tabl

e ag

greg

ates

(% 1

05°C

dri

ed s

oil)

(b)

51

Physical and chemical study on irreversible changes of water retention properties in an Azores Andisol.

C. Fernandez, F. van Oort and I. Lamy

INRA, Unité de Science du Sol, RD-10, 78026 Versailles, France Introduction Andisols are widely used for agronomic land-use in many parts of the world. However, they are highly responsive to farming practices that do not sufficiently take into account their specific physical and physico-chemical properties, in particular irreversible drying effects. These effects have been for a long time attributed to a rearrangement of pore space (Maeda & Warkentin, 1975) due to a micro-aggregation of elementary allophane particles (Kubota, 1972). On the other hand, Wada (1989) mentioned that negative charges could develop during desiccation related to changes in coordination of some surface Al atoms. In order to identify mechanisms governing irreversible drying effects of allophanic material, we studied both soil water retention and surface charge characteristics on samples of an andisol with exceptional model physical properties. Material & Methods Samples of a deep, 7-Snd horizon in an andisol located at the Azores Islands (Lagoa do Caiado, Pico Island) were selected during the 2001 Cost 622 meeting. The soil was slightly acid (pHwater 6.2), highly weathered, containing 24% allophane. It displayed a complete isotropic character under optical polarising light. Physical study showed an extreme low bulk density (0.18 Mg/m3) and a high water content (> 450%). Soil water retention was measured during desiccation and rehydratation of centimetre-sized samples, initially equilibrated at various water potentials. On the same samples, we determined the Zero Point of Charge (ZPC) and total variable charges by NaOH - HClO4 titration, with different ionic strenght. Results & Discussion During desiccation, the total water content decreased from 450 to 20% (air-dried), and normal shrinkage was observed (Fig. 1) until drying to < 32.5 h.r. (< -150 Mpa). These results indicated an absence of soil structure at a mm and µm scale in the studied soil material. Rewetting experiments showed that notable loss of hydration capacity occurred for water potentials > -320 kPa and < -33 MPa. For lower water potentials (-33 to – 234 MPa) only 7% of the initial water content was reached (30g/100g soil). ZPC values strongly varied with the state of drying of the samples. Calculated surface charges at different water potentials revealed two distinct domains: > - 320 kPa and < - 1Mpa. The soil's rehydration capacity after drying and the amounts of total negative surface charges were strongly correlated (Fig. 2). Conclusions This combined physical and chemical study suggested a two-step mechanism for irreversible changes of water retention properties in andisols. On drying of a field moist sample, the first step was mainly chemical and corresponded to coalescence of elementary allophane particles resulting from water extraction with reduction of surface charges together with a slight increase of bulk density. At higher water potentials, a second step was a mainly physical: consolidation of the material with a strong increasing bulk density. Only minor losses of surface charges were observed due to some interaction of chains of allophane particles. For the studied model material, our findings highlighted a distinct threshold of irreversibility of physico-chemical properties for water potential of approximately -500 kPa.

52

References Kubota, T. 1972. Aggregate formation of allophanic soils; effect of mechanical impedance to

growth on the levels of ABA and IAA in roots tips of Zea mays L. Journ. Exp. Botan., 33: 943-951.

Maeda, T., and Warkentin, B.P. 1975. Void changes in Allophane soils determining water retention and transmission. Soil Sci. Soc Am. Proc. 39:398-403.

Wada, K. 1989. Allophane and imogolite. p. 1051-1087. In: J.B. Dixon and S.B. Weed (ed) Minerals in soil environment, 2nd ed. SSSA Book Ser. no 1, Madison, WI.

Figure 1 Shrinkage curve of cm-sized samples during drying.

y = 335,81x + 28,895R2 = 0,9504

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Permanent charges contribution during desiccation (OH- mol.l-1.g-1)

Wat

er c

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) af

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Figure 2 Relation between the soil's rehydration capacity and the of total negative surface charges established on centimeter-sized samples equilibrated at various water potentials.

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53

Effects of drying on volcanic soil degradation: Practical implication on hydrological behaviour

A. Basile1 and A. Coppola2

1Institute for Mediterranean Agricultural and Forest Systems (ISAFOM-CNR), Ercolano (NA), Italy

2Department DITEC, University of Basilicata, Potenza, Italy Many volcanic soils (Andisols) show an irreversible volume changing after drying. The irreversible changes occur when elementary unit particles, weakly bonded together, come sufficiently close to enable strong bonding; larger size aggregates are formed and they are not broken up on re-wetting. These modifications affect very much the type, volume and pore-sizes distribution and therefore modifies several physical properties (i.e. water retention, hydraulic conductivity and apparent hydrodynamic dispersivity) producing remarkable effects on many hydrological processes taking place in the soil. Several basic mechanism are not yet know on this distinctive effect: among others the energy level at which the irreversible change starts and develop, its development rate, and the effect of the time on the energy accumulation process. This deficit of knowledge limits our capability in distinguishing the status, in respect of the time scale, of the field degradation and therefore the prediction capability of the process. Such scenario is especially relevant considering that in much research and practical activities many physical properties are obtained on dried samples. One of the aim of this study is therefore the prediction of the hydrological behaviour of soil profiles studying the influence and the effects of samples drying. Two different case studies were investigated: the first one in an agricultural area with intensive tillage and inputs (SARNO plain); the second one on a natural slope (Monte FAITO). The drying effects on the Ap horizons of these different soil profiles have been compared in terms of the single physical property (i.e. water retention, saturated and unsaturated hydraulic conductivity, pore sizes distribution, PDF, etc..). Moreover, this drying effect on the solute and water balance has been tested. Undisturbed soil samples were collected in cylinders from the main horizons of volcanic soils classified as Humic Haplustand and Typic Hapludand. The Humic Haplustand was located in the SARNO plain, an alluvial plane surrounded by limestones covered by volcanic material; they were formed by pyroclastics fall and volcanic colluvial material. The Typic Hapludand soil was located at 1120 m a.s.l. on limestones relief covered by volcanic ash and pumices. Soil water retention and hydraulic conductivity functions were measured by means of tension table and Wind’s method, saturated hydraulic conductivity by means of constant head permeameter and solute transport characteristics by means of a miscible flow experiment. These measurement were performed twice, the second one after the samples were oven dried. Main results of the comparison in the SARNO soil were that the drying induces: (i) reduction in the total porosity of the 20%; (ii) the translation of the soil water retention curve (at least for values of potential ranging between –5 and –350 cm), along with the corresponding pore-size distribution. Taking into account the invariance of the bulk density, this confirms that the porosity reduction occurs in the small pores region; (iii) an augmented fraction of large pores, as indicated by the pore-size distribution analysis; (iv) the saturated hydraulic conductivity values agree with the new distribution; (v) the breakthrough curve become slightly asymmetric and a preferential flow can be hypothesised.

54

Main results of the FAITO soil were that the drying induces: (i) reduction in the total porosity of the 10%; (ii) this porosity reduction occurs in the small pores region. Furthermore, a physically based water balance model has been applied calculating a specific ‘functional properties’ for each case study. The effect of the drying on the Ap horizon was compared in terms of environmental risks. Particularly, in the SARNO plain the functional properties derived were (i) the solute resident time and (ii) an index of groundwater vulnerability while in the FAITO mountain was (iii) an index derived by the surface runoff.

55

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56

A classification of tephra in volcanic soils. A tool for soil scientists.

P. De Paepe and G. Stoops Laboratorium voor Mineralogie, Petrologie en Micropedologie, Universiteit Gent, Belgium

Fieldwork and microscopic studies in the frame of the COST-action 622 have shown that there is a need for a uniform and simple system for the description and classification of pyroclastic material in soils and soil thin sections. Although geologists and petrographers dispose of an internationally accepted, comprehensive system for classification and textural description of igneous and pyroclastic rocks (Schmid, 1981; Fisher & Schmincke, 1984; Le Maître et al., 1989), soil scientists quite often continue to use local and/or obsolete terms. The aim of this paper is to propose a selection of terms to be used in order to reach a more uniform description of volcanic materials in soil profiles, both in the field and in thin sections. Taking into account that some physical properties of tephra may influence soil properties, following parameters are considered to be of major importance: 1° particle size, 2° vesicularity, 3° crystallinity and texture, and 4° chemical composition. 1° Particle size. Tephra is a collective term used in petrology for unconsolidated accumulations of solid fragmented matter produced by explosive volcanism. Individual pyroclastic fragments, also known as pyroclasts, can be named according to a wide range of criteria, but the most fundamental basis for description purposes in the field and under the microscope is grain size. Hence, the widely used granulometric classification and nomenclature of pyroclasts and well-sorted pyroclastic deposits elaborated under the authority of a subcommission of the International Union of Geological Sciences (IUGS) (Schmid, 1981) should be applied by preference (Table 1). Table 1 Classification and nomenclature of pyroclasts and well-sorted pyroclastic deposits based on clast size (after Schmid, 1981)

Pyroclastic deposit Clast size

in mm Pyroclast

Mainly unconsolidated: tephra

Mainly consolidated: pyroclastic rock

bomb, block agglomerate

bed of blocks or bomb, block tephra

agglomerate pyroclastic breccia

Lapillus layer, bed of lapilli or lapilli tephra

lapilli tuff

coarse ash grain coarse ash coarse (ash) tuff

64 2

1/16 fine ash grain (dust grain)

fine ash (dust) fine (ash) tuff (dust tuff)

2° Vesicularity. Vesicles form by expansion of dissolved gases in the molten rock. Their abundance controls the bulk density and alteration rate of volcanic glasses and crystalline rocks. Pumice is light coloured, extremely vesicular silicic glass with low density. Vesicular basaltic ejecta (so-called scoriae) are black or iridescent when fresh, but their colour becomes drab to deep reddish brown with increasing degree of oxidation, rendering them nearly opaque in transmitted light. They seem also more resistant to weathering.

57

3° Crystallinity and texture. Crystallinity expresses the degree to which a pyroclast (or rock fragment) is composed of crystalline material in relation to the glass phase. Vitric particles are characteristically glassy, whereas holocrystalline fragments consists wholly of mineral grains. In pyroclasts composed of a mixture of glass and crystals, the resultant texture is called hypocrystalline (or merocrystalline). Pyroclasts consisting exclusively of crystals too small to be discernible with the naked eye or using a hand lens are said to be aphanitic-textured, whereas the term porphyritic refers to fragments carrying relatively large, usually well-shaped crystals (phenocrysts) set in a fine-grained or glassy groundmass. When there is a parallel alignment of tabular crystals (especially feldspars), suggestive of flow, the texture is called trachytic. 4° Composition. The IUGS modal classification bases the names of volcanic rocks on the relative proportions of five mineral groups: Q (quartz, tridymite, cristobalite), A (alkali feldspars), P (plagioclases An5 to An100), F (feldspathoids) and M (mafic and related minerals) for which volume modal data must be determined. The texture and the nature of the minerals, and some physical properties of volcanic glass provide valuable information on the chemistry and the cooling history of the source magma. Colour in transmitted light and relief (or refractive indices) of volcanic glasses show a close correlation with chemical composition, basaltic glasses (sideromelane) being coloured and having a positive relief, whereas rhyolitic glasses tend to be colourless, with negative relief. Palagonite is the primary alteration product of sideromelane. It has a wax-like or resinous appearance and in thin section it is yellow to orange, isotropic or weakly birefringent. During palagonitisation some chemical elements are leached out, while others show gains. This is reflected by either a decrease, or an increase of the refractive index. Volcanic glasses are inherently unstable and decompose more readily than mineral phases they are associated with. Alteration of basaltic glasses may change drastically the chemistry of interstitial pore waters and frequently results in deposition of secondary mineral phases (zeolites, carbonate minerals, opal, etc.) in cements and pore spaces. In contrast, alteration of silicic glasses promotes lithification, cementation by redistribution of silica and formation of bentonitic clays. It is the main purpose of our poster presentation to illustrate the granulometric and textural features related above and their impact on weathering, using field photographs and micrographs of soil and rock thin sections. References and further reading Fisher, R.V. and H.-U. Schmincke. 1984. Pyroclastic rocks. Springer-Verlag, Berlin. Le Maître, R.W. (ed). 1989. A classification of igneous rocks and glossary of terms.

Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. Blackwell Scientific Publications, Oxford.

MacKenzie, W.S., Donaldson, C.H. and C.Guilford. 1987. Atlas of igneous rocks and their textures. Longman, Harlow, UK.

Schmid, R., 1981. Descriptive nomenclature and classification of pyroclastic deposits and fragments: Recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks. Geology 9:41-43.

58

Soils and paleosols on volcanic rocks of Cantal (Massif Central, France); Example of Puy Courny, Aurillac

P.Quantin1, J. Dejou2 and M. Tejedor3

1IRD, Paris; 2INRA, Clermont-Ferrand ; 3University of La Laguna, Spain. Introduction Red fersialitic soils were studied in the Cantal on late Miocene basalts (Dejou & al.1982, Chesworth & al. 1983). The present soils, of Holocene time although on Miocene volcanic rocks, are aluandic Andosols or andic Brown soils ( Hétier 1975, Moinereau 1977, Chesworth & al. 1983). A new study of the Puy Courny cut (after the COST 622 Meeting in Auvergne, 30-05 to 3-06 2001) shows the following succession of volcanic products, ‘alterites’, paleosol, and present soil, from bottom to top : - a/ over a basanite flow, 7.3 M. years old, a green ‘alterite’ and a red paleosol; - b/ series of 5 to 6 outburst pyroclastic products, partially altered; -c/ a weakly altered basalt flow, 6.4 M. years old; - d/ the present soil, deriving from periglacial deposits of weathered trachybasalt material. Results The whole elements chemical composition allows us to approximate the magmatic family of successive original volcanic materials : a/ 1st series : an augite-olivine trachybasalt flow, evolving up to quartziferous basalt in the red paleosol; b/ 2d series : pyroclasts of quartziferous latite composition, evolving from dark quartziferous latite to rhyodacite; c/ 3d series : upper-Cantalian basalt flow, near to augite-olivine trachybasalt; d/ 4th series : weathered products of trachybasalt. The mineralogy of clay minerals and the chemical composition show different types of successive alteration or weathering processes.

1. Paleosol and present soil weathering : 1.1 : The red paleosol, of late Miocene formation, almost completely weathered, is fersialitic from its chemical composition (Ki = 2.7, Kr = 1.8), as well as its clay mineralogy, of predominant dehydrated halloysite, a little of disordered smectite and of hematite and goethite iron oxides, without residual organic matter. ( Ki = SiO2/Al2O3 mol. ratio ; Kr = SiO2/Al2O3+Fe2O3 mol. ratio). 1.2 : The present Brown soil, with eutrophic and weakly andic properties, is only partially weathered, rich in silica ( Ki = 5.0, Kr = 3.4 ) and residual primary minerals. It differs greatly from paleosol in its clay mineralogy, of predominant disordered smectite, a little of illite and non-crystalline iron oxi-hydroxide, and traces of allophane.

2. Two types of ‘alterites’ : 2.1 : ‘pre-meteoric’ : probably formed under hydromagmatic conditions during the deposit process or immediately after. That is characterised by formation of well crystallised vermiculite, in the basanite alteration products and overlying green alterite, as well as in pyroclastic flows of quartziferous latite (blast of bright grey sand or pumiceous lahar) and the altered ‘cortex’ (crust) of bowls of the upper basalt flow. 2.2 : probably ‘meteoric’ : characterised by poorly ordered smectite clay minerals in red brownish alterite, brown cinerite, purple brownish tuff, as well in the present andic Brown soil. The chemical properties, from top to down of the cut, are characterised by : pH (H2O) slightly acid in present soil, then slightly alkaline in all ‘alterites’ and red fersialitic soil; �pH (H2O-KCl) >1, from 1.3 to 1.9, in relation with high permanent charges and CEC clay minerals, even in halloysitic paleosol; high values in exchangeable bases and bases saturation

59

ratio of CEC, in present andic Brown soil. The andic diagnostic criteria are near the acceptable limits to be an andic intergrade to Brown soils, but not in lahar alterite. To note in Andic Brown soil the high ratio Feo/Alo and the very little allophane content ( ˜ 1%). Conclusion The genetic processes, of present Brown soil, red paleosol and successive ‘alterites’ are : The present soil is an eutrophic Brown soil intergrade to andic (Andic Eutrochrept). It was forming during the Holocene time (< 10 000 years old), on preweathered trachybasalt periglacial materials., under a semi-humid (ustic) temperate (mesic) climate. The red paleosol, from pyroclastic quartziferous trachybasalt, is a ‘Fersialitic’ soil. It was probably forming during a long weathering time (> 100 000 years) under a warm (thermic) and semi-humid (ustic) climate. The vermiculite alterites were probably formed immediately after the volcanic eruption under hot and hydrated, hydromagmatic, conditions. The poorly ordered smectites alterites could be due to a slow underground weathering, without obvious soil formation, through a slow rainwater percolation. References Chesworth, W., Dejou, J., de Kimpe, C. et al., 1983. Etude de paleosols rouges développés sur

basaltes miocènes du Massif Central français. Principales caractéristiques physico-chimiques de ces pédogénèses. Cah. ORSTOM Sér. Pédol. XX (3): 189-208.

Dejou, J., Chesworth, W., and Larroque, P. 1982. Données nouvelles sur l’évolution superficielle fersiallitique subie par les basaltes pontiens du Bassin d’Aurillac (Cantal, France). Cas du profil de Saint Etienne de Carlat et considérations paleoclimatiques. Pédologie, Gand, 32 :67-83.

Hétier, J.M. 1975. Formation et évolution des andosols en climat tempéré. Thèse Univ. Nancy I : 194 p.

Moinereau J. 1977. Altération des roches, formation et évolution des sols sur basalte, sous climat tempéré humide (Velay, Vivarais, Coirons). Thèse Univ. Sci. Et Techn. Languedoc. Montpellier:139 p.

Acknowledgements : to Dra Concepción Jimenez, of La Laguna University, for her contribution to soil analysis.

60

Proton pumping, electron pumping, and the activities of aluminosilicate components in the formation of Andosols

Ward Chesworth1 and Felipe Macias2 1University of Guelph, Guelph, Ontario, CANADA

2Universidad de Santiago, Santiago de Compostela, Galicia, SPAIN. The chemical evolution of soil is essentially determined by fluxes of protons and electrons. The proton flux is produced by the pumping of H+ ions from an organic or carbonic acid source, to a sink comprised of the carbonate and aluminosilicate bases predominant on the earth’s land surface. The electron flux takes place between organic matter as the major source, and atmospheric oxygen as the pricipal sink. A convenient way to show these features of soil genesis is by means of the Pourbaix, or Eh(pe)-pH diagram. The combined effect of proton and electron pumping is to confine the field of most soils within an envelope with three salients in Eh-pH space – acid, alkaline and hydromorphic, respectively. The acid salient is the one of interest in any discussion of the formation of andosols. It represents the path of evolution of three major types of soil genesis: podsolization, ferralitization and andosolization. The first two are distinguished principally in terms of the proton source, the last in terms of the parent materials – volcanic glass being characteristic. Volcanic glass, even as an interstitial phase in basic rocks such as basalt, tends to be acidic in a petrological sense, and normatively rich in felsic, rather than femic components. Si, Al, Na and K are the major cationic constituents, and the typical products of low PT alteration are dominated by phases in the system SiO2-Al2O3-H2O. The commonly observed difference in andosols between allophanic assemblages and those containing imogolite, are explainable in terms of initially amorphous precipitates undergoing Ostwald ripening from different starting points in logAl3+/(H+)-log(H4SiO4) space.

61

Genesis and formation of volcanic soil in Fregrean Fields

C. Colombo 1, A. Di Cerce 1, M.V. Sellitto, G. Palumbo 1 and Terribile F. 2 1Dip. Scienze Animali Vegetali e dell’Ambiente, Unversità del Molise, Campobasso, Italy

Dipartimento di Scienze del Suolo della Pianta e dell’Ambiente, Università degli Studi di Napoli Federico II, Portici Italy

The Volcanic soils located in the Flegrei Fields district are formed from heterogeneous pyroclastic rocks. The origin of the Flegrei District, according to its geographic location and to the age of the products, has been ascribed to about 30 different volcanic events begun more than 30.000 years ago. They formed large deposits of pyroclastic products such as the geologic formation called “Neapolitan yellow tuff”. The aim of this work was to study the mineralogy and the geochemistry of two soils of the northern slope of Mt Gauro: the first soil (EUR01) occurring on flat terraces and it has a specialized fruit trees (apples) land use ; the second soil (EUR02) is located on chestnut forest at the top of Mt Gauro. On both soils physical and chemical analysis were carried out. The profile EUR02 has been also object of micromorphological description and mineralogical analysis (Fig. 1). The thin sections were analysed by optical microscopy (OM) and selected areas have also been observed by scanning electron microscope (SEM) and microanalysis (EDS) to observe the differences in the chemical composition. All grain size fractions have been analysed by X ray diffractometry (XRD). The pedogenetic environment of the volcanic soils studied results particularly complex for the heterogeneity of the pyroclastic materials stratified during the intense volcanic activity in the last 5000 years. The studied profiles have a good degree of soil development . The profile EUR01 has slight acidity in the surface horizons (O, A1); pH increase toward the C horizon. The EUR02 profiles (forest soil) has similar features but higher KCl acidity .

Figure 1 Scanning electron images and Al, Si, Ca and K distribution map for selected grain pumice in the thin section showing the variability in chemical composition.

Si Al

K Ca

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Such behaviour is associated with the presence of exchangeable aluminum which accumulates in the lower part of the profile (horizons BC2 and C). The differences in the values of the chemical parameters of the two profiles EUR01 and EUR02 can also be related to differences in soil management; in fact the EUR01 profile show a lower content of organic matter and CEC. The profile EUR02 has very high values of CEC that was not correlated to the presence of organic matter. The micromorphological analysis has shown the rare presence of clay coatings in the C horizons along with pumice having different degree of weathering. The chemical analysis obtained by SEM - EDS on the same sections has shown that the silicon has accumulated in the external parts of the pumice; such areas appeared optically isotropic to the OM while aluminum has a very different distribution from the silicon. In addition other element mapping of the pumice in the thin sections have shown in prevalence similar distribution of alkaline cations, indicative of moderate weathering (Fig.1). Mineralogical composition of the clays has shown the presence of halloysite (hydrated form) with a peak at 1 nm and meta-halloysite with a peak at 0.72 nm. In the clayey fraction zeolitic minerals (mainly analcime and philippsite) have also been observed, in the deepest horizons ( (BC1, BC2 e C1 of the EUR02 profile), while in the top soil zeolites clearly decrease(Ming et al., 1989). In the sand fraction biotite, leucite, sanidine have been observed along with minor content of phillipsite ed analcime. The presence of such mineral related with higher values of CEC in the EUR02 profile results of particular interest, to understand the weathering of the zeolites mineral and their influence on the specific chemical characteristics of the volcanic soil in the Flegrei Fields district. References Ming D. W., and Mumpton F. A. (1989). Zeolites in Soils. In Minerals in Soil Environments

(2nd Edition) – SSSA Book Series, no.1., Ed. J. B. Dixon e S.B. Weed., 873-911.

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Soils developed in volcanic material in Hungary

Gy. Füleky1, Á. Kertész2, B. Madarász2, O.Fehér1

1 Szent István University Department of Soil Science and Agricultural Chemistry, Gödöll�, Hungary 2Hungarian Academy of Sciences, Geographical Research Institute,Hungary

The neogenic volcanism has two basic types in the Carpathian basin. In Hungary, the major part of the Northern Uplands belongs to the Inner-Carpathian volcanic belt. The volcanic activity occurred in the Miocene and Pliocene, with the mountains getting younger from SW to NE. Intermediary and acidic lava and pyroclastics are the products of the volcanic activity, with an increasing silicate content. The other type of the volcanism is the basaltic volcanic activity related to faults. The basaltic volcanism may be estimated to have taken place in the postpannonian period, 6-2.2 million years BP, including Transdanubian Uplands and the basalt occurrences in Nógrád district.

Soil profiles were discovered on different volcanic materials in Hungary: on andesite (Tokaj N 19 and Magas-Tax) on rhyolit tuff (Andornaktálya and Tolcsva), on basalt (Badacsony N 18) and basalt tuff (Tihany N 17).

Considering the parameters of andosol properties of the investigated soil profiles we can conclude that the andosol properties of investigated 3 soil profiles do not fulfil the criteria of andic, vitric properties. (Table 1.)

According to the X-ray diffraction analysis illite was the dominant (76-93%) clay mineral followed sometimes by smectite (N 17 9-19%, N 18 2-7%, N 19 0-1%). These results also prove the evidence of former loess contamination at the investigated profiles.

Considering the non-European volcanic soil profiles we can conclude that in the case of Andornaktálya and Tolcsva soils developed on rhyolite-tuff do not completing any criteria of andic, vitric properties. Same in case of Magas-Tax developed on andesite in Börzsöny Mountains.

Only the profile in Mátra Mountains, in Galyatet� developed on andesite is close to andic properties with bulk density of 0,7, organic matter of 7-8% and a phosphate retention of 61%. The Alo+1/2Feo content of this profile is the nearest to 1% among all the Hungarian profiles. It is interesting to mention the ecological conditions of the last location: altitude above 900 m, precipitation more than 700 mm, temperature is cooler then at the other profiles, vegetation is evergreen forest, parent material is andesite.

We can conclude that in Hungary located at the lower part of the Carpathian-basin both the quality of volcanic material (age, weathering etc.) and the ecological conditions are not favourable for andosol development. On volcanic material rather Cambisols, Phaeozems, Umbrisols etc. could develop and only on the higher points of the Carpathian mountains both in Slovakia and Romania andosols could be found. The classification of the Hungarian volcanic soils: N 17 – Tihany: diagnostic: mollic, no-calcic, xeric

WRB: haplic Phaeozems US.ST: typic Haploxerrols RPF: Calcisol calci-magnesique, sur tuf basaltique, rather than Phaeosol.

N 18 – Badacsony: Umbric, an acid pH and probably BS<60% fit with umbric and dystric qualifers;

under this type of forest in some altitude xeric, a transition to ustic; dark cloloured and high C content fit with humic qualifier. WRB: humic Umbrisols US. ST: dystric Xerochrepts RPF: Brunisol mésosaturé humique, éolico-culluvial sur basalte altérée.

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N 19 – Tokaj-Tarcal: xeric (transition to ustic), dark coloured and high C content fit with humic qualifier) WRB: humic Umbrisols US.ST: dystric Xerochrepts RPF: Brunisol mésosaturé humique, éolico-colluvial sur andésite altérée.

Galyatet� – Mt. Mátra: umbric epipedon with transitive andic features in the top-epipedon, but too shallow to be diagnostic. Ustic moisture regime. WRB: humic Umbrisol, intergrade to humic andic Umbrisol US.ST: dystric Ustochrepts RPF: Brunisol mésosaturé humique, intergrade andique, éolico-colluvial/andésite altérée.

Andornaktálya – near Eger: shallow dark epipedon at the limit for mollic – dark cambic horizon with incipient vertic features (discret slickensides on pads surface near the bottom) – lithic contact near 50 cm depth – xeric moisture regime. WRB: endoleptic Phaeozems US.ST: lithic Xerochrepts, rather than lithic Haploxerolls RPF: Chernosol (Ach chernique) leptique, sur tuf rhyolitique

Tolcsva – near Sárospatak: Shallow dark eutric epipedon, cambic Bw and B/C horizons, lithic contact below 50 cm or more xeric moisture regime. WRB: endoleptic eutric Cambisols US.ST: typic Xerochrepts RPF: Brunisol saturé leptique, sur ignimbrite rhyolitique

Magas Tax – Mt. Börzsöny: umbric, ustic moisture regime WRB: Umbrisol

Table 1 Basic soil properties of the soils developed in volcanic material Soil profile Horizon Depth db

-3clay Pret Al0 + 1/2 Fe0 pHH2O Humus

N17 Ah1 0-15 0.88 36 30 0.59 6.67 8.00 Tihany Ah2 15-35 0.87 32 36 0.65 7.41 3.00 AC 35-70 0.90 14 34 0.67 7.75 2.70 N18 Ah1 0-7 0.87 20 23 0.61 5.57 16.31 Badacsony Ah2 7-25 0.92 17 29 0.70 5.20 9.97 A+R 25-50 0.98 3.3 28 0.80 5.61 4.82 N19 Ah1 0-12 0.72 25 21 0.33 5.14 7.83 Tokaj Ah2 12-45 0.74 27 26 0.35 5.34 6.64 AW+R 45-60 1.2 28 15 0.26 5.80 2.33 Tolcsva Ah 0-12 1.0 14 12 0.11 6.49 4.48 AC1 15-25 1.0 24 23 0.10 6.20 0.98 AC2 25-55 nd 9.5 12 0.09 6.37 0.65 Magas Tax Ah 5-20 1.0 21 23 0.44 5.43 2.11 B1 20-40 1.0 11 30 0.44 5.78 0.54 B2 40-80 1.3 7.4 38 0.54 5.74 0.38 Galyatet� 0 0-10 nd 23 61 0.82 4.11 8.11 Ah1 10-20 0.66 5.2 39 0.78 5.04 6.87 Ah2 20-33 0.77 5.0 38 0.76 5.17 3.00 B1 33-44 nd 2.8 47 0.71 5.21 1.65 B2 44-58 nd 5.8 40 0.73 5.11 1.24 Bw1 58-70 0.9 13 30 0.60 5.15 0.69 Bw2 >70 nd 12 30 0.47 5.20 0.42 Andornaktálya Ah 0-25 1.1 18 17 0.17 6.29 1.88 AC 25-44 0.88 2.4 12 0.08 6.56 0.53 C >44 nd 0.1 12 0.04 6.65 0.21

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Environmental conditions of Andosol formation in Transylvania (Romania). Soils of the Gurghiu volcanic chain.

S. Jakab1, G. Füleky2 and O. Fehér2

1Sapientia Hungarian University of Transylvania, Faculty of Technical and Human Sciences, Targu Mures

2Szent István Universiyt, Department of Soil Science and Agrochemistry, Gödöll�, Hungary;

The area of our case study is located in the C�limani -Gurghiu-Harghita volcanic chain in the Western part of the East Carpathians.10 sites were investigated in details during July and August of 2003.

This volcanic chain is the youngest volcanic area of the Carpathians and the length’s of it is approximately 160 km. The volcanic activity started in the northern part in the C�limani Mountains, roughly some 9.5 million years ago. On the basis of K-Ar dating the age of rocks of the central part of the volcanic chain, the Gurghiu Mountains, is of about 7,2 million years (Szakács–Seghedi.,1995�, whereas the last eruptions of the southern Harghita Mountains (at Mt. Ciomadul [Csomád]) occurred only some tens of thousands years ago (Pannon Encyclopaedia, 1999). As a consequence of its young age, the volcanic edifices of the chain are well preserved. The region is still showing post-volcanic activity. According to Michailova et al., 1984, Pécskay et al., 1985, Seghedi et al. (in print): the whole massiv of the Gurghiu Mountains, both petrologically and geochemically can be considered homogenious and mainly built up of pyroxene-andesites.

The starting point of our toposequence is the top of Seaca (1780m), famous for its superbly oval caldera. The Seaca is built up mainly of lava flows and pyroclastic sequences. The the foothill areas of the volcanoe are composed of more or less reworked secondary products intercalated between pyroclastic fall and flow deposits and subordinate lava flows (Pannon Encyclopaedia, 1999).

The slopes of the cone of Seaca are dissected by the streams of Sovata, Nyárád, and Gurghiu rivers. Surface runoff at the study area is limited due to dense vegetation cover and very high drainage of the soil surface horizons. Only are occurring along the forest roads and sheep-tracks.

Present day climate is mainly influenced by three main factors: continentality, significant vertical elevation differences and the north-south orientation of the mountain ranges. According to 20 years measured average the precipitation varies between 800-1200 mm and mean annual number of days with snow cover may reach 200 days. The typically north-south-oriented mountain ranges experience a great amount of annual precipitation especially on their western side, from the prevailing westerly winds. The mean annual temperature is around 3.5oC. Elevation differences may cause significant changes within short distances. The mean annual number of frost days may exceed 160-180 even in the basins.

From the point of view of soil formation all the above mentioned climatic conditions are favouring strong leaching and intensive weathering processes.

The other factor of understanding of soil genesis at our study was the influence of the paleoclimate: an extension of the last (Würm) glaciation, when the whole region was dominated by periglacial climatic influences, the rejuvenation of the surface was possible.

Vegetation cover at the elevations of 600-1200m is mainly beech forest (Fagetum carpaticum (Soó, 1935) mixed with Picea abies and grass-cover (Oxalis acetosella, Galium odoratum, Dentaria glandulosa , Luzula albida, L. sylvatica), Circaea alpina) conditions. Above 1600m vegetation mainly composed of: Pinus mugo and ocassianly species of Picea abies appears. The grass cover composed of Vaccinium myrtillus, V.uligimosum, Festuca rubra and Nardus stricta.

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Human influence is only limited to wood-cuts and animal grazing. Chemical data of selected soil profiles In the following table we are illustrating the chemical data of selected soil profiles from the starting point of the toposequence at Seaca at 1780 m, the middle part at 1400 m and at the bottom at 750 m. Horizon Depths

cm Color moist

BD g/cm3

pH KCl

OC% Alo+1/2Feo%

Sio mg/kg

Pret%

Seaca, Profile N 1 elevation of : 1780 m P1H1 0-30 10YR 2/2 0.51 3,85 22,048 1,997 676 82 P1H2 30-43 10YR 3/2 - 4,19 17,535 3,84 1270 94 P1H3 43-56 5YR 3/3 0.62 4,12 13,092 4,05 1520 94 Helicopter landing place at N8 At elevation of 1400 m P8H1 0-24 10YR 2/2 0,35 3,7 27,997 1,885 685 83 P8H2 24-28 7,5YR3/2 0,50 4,38 17,657 5,605 11300 95 P8H3 28-45 10YR 3/4 0,69 4,73 10,157 5,8855 17500 92 P8H4 45-80 10YR 4/3 0.67 4,93 9,1125 5,623 18700 93 Fels�halas patak N7 at elevation of 750 m P7H1 0-8 10YR 4/2 1,02 4,04 7,8016 0,8605 582 50 P7H2 8-28 10YR 4/3 1,16 4,15 5,2668 0,866 680 53 P7H3 28-40 10YR 5/3 1,07 4,54 3,5267 0,661 691 31 P7H4 40-70 10YR 5/3 1,31 4,84 3,6195 0,6495 922 27 BD: bulk density at filed capacity OC: organic carbon content Pret: phosphate retention References Michailova, N. et al. 1983. New palaeomagnetic data for the C�limani, Gurghiu and in the

Romanian Carpathians. An. Inst.Geol.Geofiz. 63. 112-124. Pannon Encyclopaedia. The land that is Hungary. CD-ROM: ARCANUM Adatbázis Ltd.

1999. Pécskay, Z. et al. 1995. K-Ar datings of Neogene-Quaternary calc-alkaline volcanic rocks in

Romania. Acta Vulcanologica 7. 15-28. Seghedi, I., A. Szakács, and P.R.D. Masaon. 1995. Petrogenesis and magmatic evolution in

the East Carpathian Neogene volcanic arc (Romania). Acta Vulcanologica, 7(2)1. 35-143. Soó Rezs�. 1935. A történelmi Magyarország növényszövetkezeteinek áttekintése I. MTA

Mat. és Term.Tud. Ért. LIII, 1- 58 Budapest

67

Some specific features of soil distribution in volcanic mountains of Slovakia

B. Juráni Comenius University, Faculty of Natural Science, Department of Soil Science, Bratislava,

Slovak Republic Volcanic soils in Slovakia are rather wide-spread, covering totally over 10 per-cent of the whole area. The main part (66 per-cent) is covered by forest, rest (34 per-cent) is used for agriculture. As a most dominant soils of this area can be considered (WRB 1998) Cambisols, but rather well spread are also Leptosols, Regosols, Luvisols, Albeluvisols and Planosols, smallest extend is covered by Andosols

Soil distribution in different mountains has specific features resulting from geological, climatic, vegetation conditions and way of land use in any part of the given area. Paper deals with Slovakia most interesting features of the soil distribution, which occurs.

Krupinská planina mountains (868.6 km2) has very specific distribution of soil. The main part of the area is built by andesites and pyroclastic material in form of plateau , later deeply cutted by erosion. Flat rests of the plateau forms today long ridges, with flat surface on the top. This surface is covered by rather thin (just a few meters thick) layer of loam having, eolian and solifluction origin.. Under such conditions most common soils here are Stagnic Albic Luvisols, Stagnic Albeluvisols, Luvic and Albic Planosols This land is used for agriculture of lower intensity. Steep slopes of erosion valleys are covered mainly by Cambisols, but on rock-outcrops also with Leptosols. Due to steep sloping and shallow soils, the main part is covered by forest, except southern promontories , thanks to influence of Hungarian lowland climate as well as microclimatic conditions (southern slopes) for centuries wine is grown, This is reason, why mainly Anthrosols can be find there.

Another type of specific soil features occurs in Cerová vrchovina mountains (496,7 km2) dominantly built by basalt and its pyroclastic material. On highest part of the mountains occurs Eutric Cambisols and Skeletic Leptosols, but locally also Chromic Cambisols (according Kubiena 1953 Rotlehm and Braunlehm), on few places also accumulated Chromic material with admixture of eolian sediments. Similar soil conditions does not occurs in any other volcanic mountains of Slovakia.

Andosols in Slovakia occurs only in highest volcanic mountains, in elevation over 800 m over sea level, with one exception. The most important are climatic conditions, to be wet enough, to create Andosols. Vegetation is mainly deciduous forest. Agricultural land use is less common an if, than today mainly meadow and pasture. For this reasons, Fulvic Andosols are dominant, Melanic Andosols are mostly exception References FAO, ISRIC, ISSS. 1998. World Reference Base for Soil Resources. p. 88 Rome Kubiena, W.L. 1953. Bestimmungsbuch und Systematik der Boden Europas. p. 388 Stuttgart

68

Relationship between Andosolization and Elemental Composition of Volcanic Ash Soils in Japan

M. Nanzyo and T. Takahashi

Graduate School of Agricultural Science, Tohoku University A characteristic process of Andosolization is preferential formation of noncrystalline materials such as allophane, imogolite, opaline silica, ferrihydrite, and Al-humus complexes. No significant tanslocation of Al, Fe and dissolved organic carbon take place. These soil components are Al- or Fe-rich materials except the opaline silica that is found in the A horizon of young Andosols. The Si/Al atomic ratio of imogolite is 0.5 and that of allophane in Andosols is mostly around 0.5 according to selective dissolution analyses. In contrast, the Si/Al ratio of pyroclastic materials and volcanic glasses, major parent materials of Andosols, are 4.8-2.4 and 5.2-2.3, respectively. These materials are rich in Si compared with those of the Al-rich noncrystalline materials mentioned above. Thus, a large amount of Si is removed during Andosolization, and Al and Fe is concentrated in Andosols. It is easily deduced that contents of other elements are also affected during Andosolization. Table 1 shows the correlation coefficient between oxalate-extractable soil components [Si (Sio), Al (Alo) and Fe (Feo)] and total contents of 57 elements. The number of samples is 95 and they were obtained from allophanic Andosol areas of Hokkaido, Tohoku, Kanto, Chubu and Kyushu districts in Japan. The number of data for 9 elements is less than 95 due to their very low content. Significant negative correlation was found between Sio and 4 elements (C, N, Na and Sr), between Alo and 3 elements (Na, Ca and Sr) and between Feo and 3 elements (Na, Si and K) at p=0.1%. These elements are alkali and alkaline-earth elements except C, N and Si. Some other alkali and alkaline-earth elements also tended to show negative correlation with Sio, Alo and Feo although not as strong. Thus, many alkali and alkaline-earth elements are lost with Andosolization. The relatively strong negative correlation between Sio and humus content (C and N) can be explained due to inhibition of allophane formation by humus. The strong negative correlation between Feo and Si is partly attributable to the properties of parent materials as well as the Andosolization process. Negative correlation between Fe and Si content is basically found in fresh tephras having a wide range of rock types. Significant positive correlation was found between Sio and 24 elements (Be, Al, Sc, Ti, Mn, Fe, Y, Zr, Nb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf and Ta), between Alo and 22 elements (Be, Al, Sc, Ti, Fe, Ge, Y, Zr, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Hf), and between Feo and 18 elements (Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Y, Eu, Gd, Tb, Ho and Er). These elements are concentrated in Andosols during Andosolization. Due to very high correlation between Sio and Alo, 21 elements among 23 strongly correlated with Sio, also showed high correlation with Alo. Mn and Ta, strongly correlated with Sio, also showed significant positive correlation with Alo at p=1%. Ten elements (Al, Sc, Ti, Fe, Y, Eu, Gd, Tb, Ho and Er) that showed strong correlation with either of Sio and Alo also correlated with Feo. However, 11 elements (Be, Ce, Pr, Nd, Sm, Dy, Tm, Yb, Lu and Hf) among 21 elements that correlated with both Sio and Alo did not correlate very strongly with Feo. Other 8 elements (V, Cr, Mn, Co, Ni, Cu, Ga and Ge) correlated strongly with Feo in spite that they did not correlate with either Sio or Alo very strongly. All the members of first transition metals from Sc to Cu showed strong correlation with Feo, adding Sc, Ti and Fe that correlated also with Sio and Alo. Correlation between oxalate-extractable components and La, Th, U etc. appear weak in Table 1. However, grouping the samples with rock type of parent materials estimated from V

69

and Zn content in ferromagnetic minerals of Andosols, some positive correlations were found as exemplified in Fig. 1. As discussed above, many trace elements are concentrated in Andosols in spite that these soils are formed with strong leaching. This is possibly due to high affinity of allophane, imogolite, Al-humus and ferrihydrite to many multivalent cations. As a result, content of many trace elements in Andosols is higher than that of other soils in Japan. Thus, the content of noncrystalline materials, i.e., Andosolization, and rock type of parent materials strongly affect the elemental composition of volcanic ash soils. Table 1 Correlation between content of Sio, Alo and Feo and total content of 57 elements. The coefficients shown in bold face is significant at p=0.1%. Notably high correlation coefficients of 0.5-0.69 and 0.7 or greater were highlighted with gray and black, respectively.

Si o Al o Feo Li Be C N Na Mg Al Si P K Ca Sc Si o 1.00 0.02 ���� ����� ����� ����� 0.00 ��� -0.02 -0.32 -0.21 -0.32 ����

Al o ���� 1.00 -0.04 ���� -0.19 -0.24 ����� -0.02 ��� -0.27 -0.22 -0.30 ���� ����

Feo ��� ���� 1.00 -0.16 0.10 0.10 0.16 ����� 0.02 ��� ����� 0.12 ���� -0.10 ���

n* 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95*: The number of samples.

Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge Rb Sr Y Zr Si o ���� 0.18 0.11 ���� ���� 0.27 0.14 0.08 -0.10 0.17 0.36 -0.04 ����� ��� ����

Al o ���� 0.17 0.24 0.30 ���� 0.31 0.24 0.11 -0.14 0.14 ��� -0.07 ����� ���� ����

Feo ��� ��� ��� ���� ��� ��� ��� ��� 0.04 ���� ���� -0.27 0.05 ���� 0.15n 95 95 95 95 95 95 95 95 95 74 74 95 95 95 95

Nb Mo Ag Cd Sn Sb Cs Ba La Ce Pr Nd Sm Eu Gd Si o ���� -0.11 -0.10 -0.25 0.29 -0.04 -0.04 -0.10 0.29 ���� ���� ���� ���� ���� ����

Al o 0.30 -0.19 -0.09 -0.30 0.14 0.01 -0.02 -0.21 0.29 ��� ��� ��� ���� ���� ����

Feo 0.03 -0.06 0.17 0.03 0.25 -0.03 -0.14 -0.05 0.04 0.09 0.19 0.27 0.26 ���� ����

n 95 86 74 74 33 33 95 95 95 95 95 95 95 95 95

Tb Dy Ho Er Tm Yb Lu Hf Ta W Tl Pb Bi Th U Sio ���� ��� ���� ���� ���� ���� ���� ���� ���� 0.16 0.14 -0.03 -0.31 0.28 0.17 Alo ���� ���� ���� ���� ���� ���� ���� ���� 0.27 0.12 0.08 0.01 -0.30 0.26 0.12 Feo ���� 0.26 ���� ��� 0.24 0.22 0.30 0.17 -0.03 -0.08 0.24 -0.02 -0.11 -0.11 -0.12

n 95 95 95 95 95 95 95 95 95 95 92 95 92 95 95

Oxalate-extractable Si content, g kg -1

LaCs U

804008040080400

Total element content (Cs: 0-14, La: 0-51, U: 0-5.2 mg kg )-1

:Dacitic, :Andesitic, :Basaltic-andesitic, :Basaltic Fig. 1 Relationship between Sio and total element content (Examples of Cs, La and U).

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Andosols criteria and Classification of European Volcanic Soils : up to date proposals. Genesis, key factors and distribution

Paul Quantin

5 rue Boileau, Dijon, France

1. Classification A new proposal is presented for the classification of COST 622 reference profiles of European volcanic soils. That is a tentative up to date classification concerning 24 soil profiles from : Italy, Azores, Iceland, Tenerife (Canary Is.), Greece (Santorini Is.), France (Massif Central), Hungary and Slovakia. However many problems are still remaining, due to : either lack of diagnostic criteria, like soil moisture and temperature regime, water retention capacity, volcanic glass content, exch. Al, bulk density; or a doubt for the credibility or reliability of data, like clay content or exch. bases saturation ratio; or discrepancy of soil description or data comparing new with former reference data, for example profile 12 in Tenerife; or about limits of diagnostic criteria, like for andic/vitric horizons, eutric or eutri-silic qualifiers, colour of melanic/fulvic or umbric epipedon, or the priority andic/histic in H horizons of profile 9 in Iceland. There is a lack of information on the true parent material of soils over old volcanic bed rock reworked by glacial or periglacial processes. Another problem arises from the buried paleosols, in order to express better the whole soil profile and its genesis. About andic/vitric diagnostic criteria limits some little changes are proposed, namely : - Alo + ½ Feo , to be lowered to 1.7% , only for eutrisilic and aluandic horizons, according to Pret. > 70% - glass content not useful; to be deleted and replaced by other chemical (CEC) or physical (water retention capacity) properties, but taking into account org. C content. - � Bases to be lowered to 15 cmol Kg-1 for eutric or eutrisilic qualifiers. 2. Genesis The soil genesis and distribution are schematically related to 3 key factors : time of weathering, climate and topo-climatic sequences. 2.1. Time : At first on recent pyroclastics deposits, Andosols, namely silic Andosols, are predominating, although there is a gradual evolution of weathering from vitric to silic Andosols. While on old volcanic bed rock, aluandic Andosols predominate under a mesic – udic climate regime, although the time of present soil formation is holocenic. In this case the nature formerly preweathered of periglacial parent material must be taken into account. 2.2. Climate : - soil moisture regime : On recent pyroclastics, according to the moisture regime, Andosols are fulvic or melanic and dystric under udic regime, or eutrisilic under ustic regime, or vitric under xeric regime. But in Greece, due to rather aridic conditions, pyroclastics soils remain weakly weathered, as tephric Arenosols. – soil temperature regime : On recent pyroclastics the variation from thermic or mesic to frigid or cryic, does not seem affecting greatly the nature of the weathering products; although in Iceland the cryic temperature regime affects the soil structure. 2.3. Topo-climatic sequences : According to climate distribution, from top ( frigid or mesic, udic ) to downwards ( mesic or thermic, ustic or xeric ) of a toposequence, there is a gradual evolution of soil properties. For example in Massif Central ( France ), we observe : on recent pyroclastics an evolution from fulvi-silic to eutri-silic Andosols and even to eutric Cambisols; while on older lava flows : from fulvi-alic Andosols to andic or humic Umbrisols and eutric Cambisols. In Azores from top to downswards, there is a change from hydri-alic Andosols to fulvi-silic Andosols.

71

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72

Soil development processes in non-volcanic Andosols.

R. Bäumler Institute of Soil Science, Department of Ecology, Technical University of Munich, Germany

In the literature an increasing number of sites is described having andic and partly podzolic characteristics, that have developed in non-volcanic and commonly non-allophanic materials, and lacking typical Podzol eluvial and illuvial horizons. They cover a wide range of parent materials under different temperature and moisture regimes. They have been regarded as restricted to small areas, so that they were of minor interest. They were either assigned to Andisols/Andosols, Podzols/Spodosols or andic Inceptisols in WRB and Soil Taxonomy, sometimes also named Cryptopodzols (Garcia-Rodeja et al., 1987; Hunter et al., 1987; Alexander et al., 1993; Bäumler and Zech, 1994; Blaser et al., 1997; Aran et al., 1998; Caner et al, 2000). Recent soil survey in Bhutan showed that these soils are widespread all over the country between 2200 - 3500 m asl covering several bioclimatic zones (Baillie et al., 2004). The aim of this paper is to give an overview about the specific properties and processes of soil formation described so far to enhance the discussion about their position in the world of soils. In general these soils are characterised by high contents of organic carbon even at greater depth, pHH2O values <5, extremely low bulk densities (105°C) partly <0.5 g cm-3 despite clay contents of >50 %, P retention of >85%, low CEC at soil pH, and in many cases a dominance of Al-hydroxy-interlayered 2:1 clay minerals. The results further indicate advanced soil development with high amounts of both poorly and well-crystallised oxidic Fe and Al compounds. Thixotropic features of subsoil B horizons are common as well. Recent REM studies of their sand fractions indicate microaggregates of clay and fine silt particles, which were highly resistent to any dispersion procedure. In consequence specific surface areas of the <2 mm fractions are comparably high partly exceeding 50 m2 g-1. Colum experiments indicate podzolisation with mobilisation and translocation of a cocktail of DOC, Fe and Al from topsoil to subsoil being responsible of the high SOM contents in the subsoil. In addition, the mobilisation of an inorganic Al compound could be shown in the subsoil horizons. Radiocarbon ages of the organic matter in B horizons are high with respect to subsoils (up to 16 ka BP; KI-4987), which might not be fossil A horizons and which are subject to recent biogenic processes. 13C solid state NMR spectra of the soil organic matter commonly provide a dominance of aryl- and carbonyl-C compounds (Caner et al., 2003; Bäumler et al., 2004). It confirms the comparably high radiocarbon ages, as such organic compounds are generally known as partly resistant to biodegradation. The results are clearly different from Podzols having strong signals from O-alkyl and alkyl C (Wilcken et al., 1997). NMR spectroscopy, 14C ages, and colum experiments therefore indicate re-stabilisation of DOM against biodecay despite recent rooting, continuous biodegradation, and rejuvenation processes in a leaching environment. Applying soil classification criteria these soils appear to have andic and podzolic characteristics, but fail sole diagnostic features of Andosols/Andisols and Podzols/Spodosols, i.e. no visible E horizon or Alo+½Feo. Summarizing the results upon these soils almost all sites appear to merge soil forming conditions favourable to andosolisation and/or podzolisation, i.e. moderate or cooler temperatures and high humidity, high input of organic material, good drainage, and weathering conditions or weatherability of the parent materials providing a fast release of metal cations, forming metal-organic compounds and most probably also acting as binding cations to form pseudosand-like microaggragates partly causing thixotropy. Commonly these soils appear not to dry out at all despite the fact that some of the studied sites have monsoon climate with a dry season.

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Very recently discussed soil development aspects are frequent (daily) freeze-thaw cycles during the cold periods (J. Galbraith, 2003, pers. comm.; Caspari et al., 2004), and a major role of iron (Delvaux et al., 2004) that could be shown by EDX element mapping of the microaggregates providing high contents of evenly distributed Fe (Bäumler et al., 2004). It indicates a stronger influence of Fe compounds, as previously thought, which might be named “Ferro-(Alu-)andic” properties. Another overall factor might be airborne, fine-grained sediments independent of the driving forces and the source materials either volcanic or non-volcanic (Adjadeh and Inoue, 1999), and providing the basis for structural properties and chemical weathering (Caspari et al., 2004). With respect to the worldwide occurrence of such soils and the specificity of their physicochemical properties, it is suggested a re-definition and probably simplification of existing classification schemes as already mentioned by Poulenard and Herbillon (2000). The apparently distinctive processes in these soils need to be further investigated. Such studies may indicate that these are different from Andosolisation and Podzolisation sensu stricto. References Adjadeh, Th.A., and K. Inoue 1999. Andisols of the Kitakami mountain range, northeastern Japan:

their characterization and classification. Soil Sci. Plant Nutr. 45:115-130. Alexander, E.B., S.Shoji, and R. West 1993. Andic soil properties of Spodosols in nonvolcanic

materials of southeast Alaska. Soil Sci. Soc. Am. J. 57:472-475. Aran, D., M.Gury, M.Zida, E.Jeanroy, and A.J. Herbillon 1998. Influence de la roche-mère et du

climat sur les propriétés andiques des sols en région montagnarde tempérée (Vosges, France). Europ. J. Soil Sci. 49:269-281.

Bäumler, R., and W. Zech 1994. Characterization of Andisols developed from nonvolcanic material in eastern Nepal. Soil Sci. 158:211-217.

Bäumler, R., Th. Caspari, K.U. Totsche, Tshering Dorji, Chencho Norbu, and I. Baillie 2004. Andic properties in non-volcanic materials – a freak of nature or something special? Unpublished manuscript.

Baillie, I.C., Kado Tshering, Tshering Dorji, H.B.Tamang, Tsheten Dorji, Chencho Norbu, A.A. Hutcheon, and R. Bäumler 2004. Regolith and soils in mid-latitude Bhutan, Eastern Himalayas. Europ. J. Soil Sci., in press.

Blaser, P., P. Kernebeek, L.Tabbens, N.van Breemen, and J. Luster 1997. Cryptopodzolic soils in Switzerland. Europ. J. Soil Sci. 48:411-423.

Caner, L., G. Bourgeon, F.Toutain, and A.J. Herbillon 2000. Characteristics of non-allophanic Andisols derived from low-activity clay regoliths in the Nilgiri hills (Southern India). Europ. J. Soil Sci. 51:553-563.

Caner, L., F. Toutain, G. Bourgeon, and A.J. Herbillon 2003. Occurrence of sombric-like subsurface A horizons in some andic soils of the Nilgiri Hills (Southern India) and their palaeoecological significance. Geoderma 117:251-265.

Caspari, Th., R. Bäumler, Kado Tshering, and Chencho Norbu 2004. Aeolian influence on the formation of non-volcanic Andosols in the Phobjikha valley, Western Central Bhutan. Manuscript, unpublished.

Delvaux, B., F. Strebl, E. Maes, A.J. Herbillon, V.Brahy, and M. Gerzabek 2004. An Andosol – Cambisol toposequence on granite in the Austrian Bohemian massif. Catena 56:31-43.

Garcia-Rodeja, E., B.M. Silva, and F. Macias 1987. Andisols developed from non-volcanic materials in Galicia. J. Soil Sci. 38:573-591.

Hunter, C.R., B.E. Frazier, and A.J. Busacca 1987. Lytell series: a nonvolcanic Andosol. Soil Sci. Soc. Am. J. 51:376-383.

Poulenard, J. and A.J. Herbillon 2000. Sur L’existence de trois catégories d’horizons de référence dans les andosols. Earth Planetary Sci. 331:651-657.

Wilcken, H., C.Sorge, and H.-R. Schulten 1997. Molecular composition and chemometric differentiation and classification of soil organic matter in Podzol B-horizons. Geoderma 76:193-219.

74

Soils with ‘andic’ properties developed from non-volcanic materials. Genesis and implications in soil classification

E. García-Rodeja, T. Taboada, A. Martínez-Cortizas, B. Silva and C. García

Departamento de Edafología y Química Agrícola, Facultad de Biología, USC

The central concept of Andosols refers to soils developed from volcanic materials whose colloidal fraction is dominated by short-range-order minerals (allophane, imogolite, ferrihydrite) and/or Al(Fe)-humus complexes. Nevertheless, the weathering of primary minerals in parent materials of non-volcanic origin may lead to the formation of soils with these type of components, some of which can be also classified as Andosols. Since the late 70’s the presence of soils with properties close to those of Andosols was identified in NW Spain (Macías et al., 1978; García-Rodeja et al., 1987). These soils, typically their organic matter rich Ah horizons, had properties like high content in Al(Fe)-humus complexes, low bulk density, strong reaction with NaF, dominance of variable charge, high phosphate and sulphate retention capacity, etc., which make them to fulfil the requirements defined for ECDAM, ‘andic properties’, ‘andic materials’ (García-Rodeja, 1985; García-Rodeja et al., 1987) or the ‘andic’ horizon. These properties are mainly related to the abundance of Al-humus complexes accompanied by halloysites with very poor crystallinity and allophane. The formation of non-volcanic Andosols with similar properties have also been reported in Nepal (Baumler and Zech, 1994), India (Caner et al., 2002) and Austria (Delvaux et al, 2004). The climate of Galicia, with mean temperatures between 8º and 15ºC and annual precipitation ranging from 900 to 2500 mm has an important influence in pedogenesis which makes soils and saprolites differ from those of surrounding areas. A great lithological variability, together with variations in temporal and biotic factors leads to a great diversity in pedogenetic processes, within a general trend to acidification in well drained systems, that in some cases leading to the formation of Andosols or soils with properties close to them: - In rocks where weatherable minerals are dominant (gabbros, amphibolites, granulites and some biotite and plagioclase-rich schists) on old surfaces, saprolites are thick and composed almost exclusively of kaolinite and goethite (fermonosiallitization). In areas that undergo rejuvenation by erosion, two situations can be differentiated, depending on the importance of the biotic factor: i) in abiotic conditions the weathering systems are characterised by a mixture of primary materials, products of mica degradation and secondary minerals with gibbsite, halloysite and disordered materials (imogolite, allophane, Al hydroxides, iron oxihydroxides, ii) under the influence of organic matter, soils are more acidic, leading to highly reactive secondary products (mainly Al(Fe)-humus complexes, halloysite and small quantities of allophane). In many cases, these soils meet the requirements to be classified as Andosols. The organic matter accelerates weathering and together with humidity, contributes to the stabilisation of the disordered phases. Therefore, the andosolization process occurs frequently in organic matter rich horizons of soils developed from intermediate to basic rocks. - The weathering of granitic and quartz rich metamorphic rocks is slower than in the above mentioned situations. In abiotic systems the formation of kaolinite (monosiallitization) and/or gibbsite (allitisation) is accompanied by degradation of micas. In the presence of organic matter the dominant process is aluminosiallitisation, and the soils are characterised by the abundance of Al-humus complexes, Al-intelayered vermiculites, halloysite and less frequently, allophane. In some cases the Ah horizons also meet the requirements of the andic horizon. In summary, the process of andosolization that affects parent materials rich in weatherable minerals (but also other as granites or schists if weathering conditions are more aggressive),

75

can be defined as a function of weathering kinetics, the existence of adequate conditions for the stabilisation of intermediate, metaestable, products, and absence of vertical redistribution. Therefore, the allocation of the soils formed by this process as Andosols (or Andisols) is not only a consequence of fulfilling the conditions required by the classification systems but also because many of their properties are close to those of typical Andosols, particularly to ‘non-allophanic’ or ‘aluandic’ Andosols, dominated by Al(Fe)-humus complexes. Summary of the chemical and mineralogical characteristics of the main weathering and soil forming processes that lead to the formation of non-volcanic Andosols (adapted from García-Rodeja & Macías, 1984 and Calvo & Macías, 1992) Aluminosiallitization Andosolization Monosiallitization

(incipient) Monosiallitization

Biogeochemical processes Geochemical processes Horizons A A, AB Bw, C B, C Parent materials Granites

Schists Slates, Shales

Intermediate & basic rocks

Granites, Schists Shales, Slates Basic rocks

Basic rocks Biotite-rich schists

Mobility Si > Al, Fe Si > Al, Fe Si > Al, Fe Si >Al, Fe Weathering mechanism

Acid complexolisis (moderate)

Acid hydrolisis Acid hydrolisis Hydrolisis

Acid hydrolisis Hydrolisis

Weathering of primary minerals

Moderate Incipient Moderate Total

Evolution of 2:1 minerals

Degradation, aluminization

Degradation Degradation Destruction

Colloidal components

Al-humus, Allophane Halloysite Al interlay. 2:1 phyll.

Al(Fe)-humus Allophane, Al gels, Halloysite

Gibbsite Allophane, Al gels

Kaolinite Goethite

Soil properties pH pH NaF %C %Alo AlKCl (cmolc/kg) P ret. (mg/kg)

4.8 (4.0-5.5)

11.0 (8.9-11.6) 6 (3-16)

0.7 (0.3-2,2) 3.5 (1.4-6.6)

1100 (400-1900)

4.9 (4.5-5.8)

11.0 (10.2-11.7) 9 (5-14)

2.6 (1.6-4.1) 2.1 (0.6-3.0)

2000 (1300-2800)

5.0 (4.4-5.9)

10.7 (8.0-11.5) 1 (0.1-2)

0.6 (0.2-1.6) 2.0 (0.7-3.2)

850 (200-1400)

5.2 (4.5-5.9) 9 (8.0-10.1)

-- 0.8 (0.3-1.3) 1.2 (0.3-2.5)

400 (200-600) References Baumler, R., and Zech, W. 1994. Characterization of Andisols developed from non volcanic material in eastern

Nepal. Soil Science, 158:211-217. Caner, L., Bourgeon, G., Toutain, F., and Herbillon, A.J. 2000. Characteristics of non-allophanic Andisol

derived from low activity regoliths in Nilgiri Hills (Southern India). European Journal of Soil Science, 51:554-563.

Delvaux, B., Strebl, F., Maes, E., Herbillon, A.J., Brahy, V., and Gerzabek, M. 2004. An Andosol-Cambisol toposequence in the Austrian Bohemian Massif. Catena, 56:31-43.

García-Rodeja, E. 1985. Sobre la clasificación de Andosoles y su existencia en materiales no volcánicos de Galicia (NO de España). An. Edaf. Agrob., 44: 1651-1661.

García-Rodeja, E., and Macías, F. 1984. Caracterización de suelos ácidos (Podsoles-Andosoles-Suelos Alumínicos) de Galicia. Relación con los procesos edafo-geoquímicos. I Congreso Nacional de la Ciencia del Suelo, 589-602.

García-Rodeja, E.; Silva, B., and Macías, F. 1987. Andosols developed from non-volcanic materials in Galicia, NW Spain. Journal of Soil Science, 38: 573-591.

Macías, F., and Calvo, R. 1992. Caractérisation pédogéochimique des sols de la Galice (NW Espagne) en relation avec la diversification lithologique. Mise en évidence d'un milieu de transition entre les domaines tempérés et subtropicaux humides. C.R.Acad.Sci.Paris, t.315, Série II, p.1803-1810.

Macías, F., Puga, M., and Guitián, F. 1978. Caracteres ándicos en suelos sobre gabros de Galicia. An. Edaf. Agrob., 37: 187-203.

76

Abrasion pH and abrasion solution composition in reference European volcanic soils

E. García-Rodeja, J.C. Nóvoa-Muñoz, A. Martínez-Cortizas and T. Taboada Dpto. Edafología y Química Agrícola. Facultad de Biología. Universidad de Santiago de Compostela

Stevens and Carron (1948) established the use of abrasion pH as an aid in mineral dentification. Later, Grant (1969) used abrasion pH as an indicator of rock weathering and Ferrari and Magaldi (1983) proposed it as an index of potential fertility of soils. The abrasion pH is obtained by grinding the minerals into distilled water; its value is affected by the quantity of residual cations released from primary minerals and the amount and type of clay minerals. In consequence, the higher values are expected in soils that are rich in fresh and weatherable minerals and, as weathering proceeds and the clay content of the soil increases, the abrasion pH tends to decrease. In this study abrasion pH and abrasion solution composition were determined in 15 COST action 622 soils (72 horizons) developed from volcanic materials in different European volcanic regions: Italy (Napoli: N1, N2; Rome: N3, N4), Azores (N5, N6), Iceland (N7 to N9), Tenerife (N10 to N12), Santorini (N14), France (N16) and Hungary (N19), with the aim to evaluate its use as an index of weathering degree and/or of potential soil fertility in these particular soils using a set of samples that covers a wide range of volcanic materials, climatic conditions and degree of soil development. Abrasion pH was measured in peroxidized samples (to minimize the homogenizing effect of organic matter in the pH values) following the method of Grant (1969) that consists of measuring the pH of a soil (20g):distilled water (40mL) suspension after a grinding period of 2¼ min (+ 2 min for settling) in an agatha mortar. After centrifugation of an aliquot of the suspension, base cations (Ca, Mg, Na, K) and Fe, Mn Si and Al were measured. The results showed a wide range of abrasion pH values (4.5-7.7), with the lower in the soils from Azores (4.5-5.3) and the higher in those from Santorini and Hungary (>7) a fact that can be related to the different climatic conditions (udic vs xeric) determining their weathering and pedogenesis. In some cases the variations along the profile are small (N1, N2, N5, N6, N14, N19) although the lower values for each soil tend to correspond to the A horizons. In other soils the variation of abrasion pH along the profile is more complex and, frequently, can be associated to discontinuities in the parent material or to different cycles of soil formation. For example, the soil N3 has more acid abrasion pH in the subsurface horizons than in the upper part of the profile with the limit located at a discontinuity marked by a stone line; in the soils N10, N12 and N8 the buried horizons, with higher degree of weathering and pedological evolution, also have lower pH. Other approach to evaluate the abrasion pH as a weathering index in volcanic soils was to make a comparison to the weathering index of Parker (1970) (WIP), considered the most appropiate for soils on heterogeneous parent materials materials because it only includes the highly mobile alkali and alkaline earth elements in its formulation (Price and Velbel, 2003). (WIP = (100) [(2Na2O/0.35)+(MgO/0.9)+(2K2O/0.25)+CaO/0.7)]). From the comparison of both parameters (see figure) two groupsof soils can be differentiated. In one side are those from Italy and the N5 from Azores, with higher WIP, developed from more alkaline materials (trachytic and phonolitic), than the other ones, mainly formed on basaltic or andesitic parent materials, which tend to have lower WIP for the same abrasion pH. When both parameters are compared for each soil profile, the expected parallelism between them is only found in two soils (N9, N10), while in other, like N4 or N16, they follow opposite trends.

77

The quantity of base cations released to the abrasion solution is very low in all the studied horizons (Ca+Mg+Na+K<0.5 cmolc/kg), with the lower concentrations in the soils from France and Azores (0.03-0.1 cmolc/kg). The only exception is the soil from Hungary, with abnormally high contentent in all the measured cations. The composition of abrasion solution has no relation to the abrasion pH neither to other parameters generally related to the potential fertility of soils like the total reserve of bases (TRB). Only K and Ca in exchange complex are relatively well correlated to their concentration in abrasion solution (r2=0,771 and =0,638 respectively, for most but not all samples).

Weathering index of Parker vs abrasion pH in volcanic soils

In conclusion, abrasion pH can be interpreted, in a very general way, in terms of weathering or pedogenetic evolution in the soils of volcanic regions and also may serve as a tool to understand the complex processes that frequently occur in these soils (heterogeneity of parent material, burial processes, tephra inputs, polygenesis). Nevertheless, the mentioned complexity can also limit the use of this single parameter. As the value of abrasion pH depends on the chemical and mineralogical composition of the material, but also on the physicochemical behaviour of the new surfaces created during the grinding process, many of the unusual characteristics observed in the abrasion pH and abrasion solution composition of volcanic soils are to be linked to the special constituents and properties that characterize these soils, in particular their charge properies and the effects that grinding may produce on them. This represents a disadvantage of the method but it may also help to the understanding of the behaviour of these soils and their components when the obtained information is analyzed in detail for each particular soil or horizon. References Grant, W.H., 1969. Abrasion pH, an index of chemical weathering. Clays and Clay Miner.

17:151-155. Ferrari, G.A., and D. Magaldi. 1983. Degree of soil weathering as determined by abrasion pH:

Applications in soil study and paleopedology. Pedologie 33:93-104. Parker, A. 1970. An index of weathering for silicate rocks. Geol. Mag. 107:501-504. Price, J.R., and M.A. Velbel. 2003. Chemical weathering indices applied to weathering

profiles developed on heterogeneous felsic metamorphic parent rocks. Chem. Geol. 202:397-416.

Stevens, R.E., and M.K. Carron. 1948. Simple field test for distinguishing minerals by abrasion pH. Am. Mineralogist 33:31-49. In Grant (1969).

020406080

100120140160180

4,0 5,0 6,0 7,0 8,0

pHabr

WIP

IT

AZ

IC

TF

GR

FR

HU

78

Dissolution rate of basaltic glass.

S. R. Gislason1, and E. H. Oelkers2 1Science Institute, University of Iceland; 2 CNRS/URM 5563, Université Paul Sabatier, Toulouse, France

Rapid cooling of magma on the Earth produces approximately one billion cubic meters (1 km3) of glass each year, mainly along the 70,000 km oceanic ridge system (Morgan and Spera, 2001). Most of this glass is of basaltic composition. The overall objective of the studies reported here is to define and understand the dissolution rate of volcanic glasses in the surface environment of the Earth. Basaltic glass dissolution rates were measured far from equilibrium as a function of aqueous aluminium, silica, and oxalic acid concentration at 25° C and pH 3 and 11, and as a function of pH from 2 to 11 at temperatures from 6° to 50° C, and at near neutral conditions to 150° C (Oelkers and Gislason, 2001; Gislason and Oelkers, 2003). Dissolution rates decrease dramatically with increasing pH at acid conditions, minimize at near neutral pH, and increase slowly with increasing pH at basic conditions. The pH, at which basaltic glass dissolution minimizes, decreases with increasing temperature. Rates are most likely controlled by partially detached Si at the basaltic glass surface, which is linked to the Al/proton exchange on the glass surface. The exchange of aluminium for three protons at the surface leads to the formation of three partially detached Si atoms on the glass surface. Regression of far-from-equilibrium dissolution rates obtained in our studies and reported in the literature for basaltic glass indicate that all data over the temperature and pH range 6° < T < 300° C and 1 < pH < 11 can be described within uncertainty using

( )3/1

Al

3H/

,+3

+

exp��

�

�

��

�

�= −

+ a

aAr RTE

AgeoA

where r+,geo signifies the geometric surface area normalized steady-state basaltic glass dissolution rate at far-from-equilibrium conditions, AA refers to a constant equal to10-5.6 (mol of Si/cm²/s), EA, designates a pH independent activation energy equal to 25.5 kJ/mol, R stands for the gas constant, T signifies temperature in K, and ai represents the activity of the subscripted aqueous species. References Gislason, S.R., and H.E. Oelkers. 2003. The mechanism, rates and consequences of basaltic

glass dissolution: II. An experimental study of the dissolution rates of basaltic glass as a function of pH and temperature. Geochim. Cosmochim. Acta, 67: 3817-3832.

Morgan, N.A., and F.J. Spera. 2001. Glass transition, structural relaxation, and theories of viscosity: A molecular dynamics study of amorphous CaAl2Si2O8. Geochim. Cosmochim. Acta 65: 4019-4041.

Oelkers, E.H., and S.R. Gislason. 2001. The mechanism, rates, and consequences of basaltic glass dissolution: I. An experimental study of the dissolution rates of basaltic glass as a function of aqueous Al, Si, and oxalic acid concentration at 25° C and pH = 3 and 11. Geochim. Cosmochim. Acta 65: 3671 - 3681.

79

Micromorphology of an Icelandic Histosol

Thorsteinn Gudmundsson1 and E.A FitzPatrick2 1LBH Hvanneyi IS; 2Aberdeen GB

Introduction Histosols and Andosols are agriculturally the most important soil types in Iceland. The Histosols preserve remains that document the natural history and they store large amounts of carbon and nitrogen. A Histosol profile in North Iceland was selected for intensive studies, including the determination of the C and N reserves and micromorphological investigations using large (5x10 cm) thin sections. The thin sections were made after replacement of the soil water with acetone and impregnation with a polyester resin (FitzPatrick and Gudmundsson 1978). The soil profile has three distinct rhyolitic tephra layers from eruptions of the volcano Hekla. The top tephra layer ‘H1’ is from the eruption of 1104 and is thus 870 years old at the time of profile description in 1974. The age of the other tephra layers has been determined through radiocarbon dating as follows; the middle layer ‘H3’ about 2800 BP and the bottom layer ‘H4’ about 3800 BP. These dates allow the calculation of the rate of deposition at different time intervals. The peat formation is assumed to have started about 9.000 years ago. The soil organic C content is 19 – 27 % in the top 22 cm increasing to 40 – 48 % below 94 cm. In the top 22 cm the mineral material is about 50% but decreases to about 20% below 62 cm. The yearly input of C and N is highest in the top 22 cm due to living roots and slow rate of decomposition whereas the decomposition has gone further at greater depth. Thus the average input of C and N during the 9.000 years period is 126 and 6 kg/ha respectively. The yearly input of mineral material was 2 - 3 times higher above the top tephra layer than previously. This is associated with the period of habitation and the well documented wind erosion and aeolian input after the settlement of the country.

Soil Mineral material Organic C Total N Depth cm

Period/ Number of

years total t/ha

Yearly increase kg/ha

total t/ha

Yearly input kg/ha

Total t/ha

Yearly input Kg/ha

total t/ha

Yearly input kg/ha

C/N

0 - 22 Surface to Tephra H1 870 years

563

616

247 284 129 148 8,3 10 15 – 17

28 - 60

Between tephra

H1 and H3 1930 years

610

316

253 131 171 89 8,9 5 18 – 26

62 - 90

Between tephra

H3 and H4 1000 years

506

506

113 113 199 199 8,2 8 23 - 27

171 - 235

H4 to Bottom

5200 years

1804

347

550 106 635 122 24 5 26 – 36

0 – 235

Whole profile 9.000

3456

384

1163 129 1134 126 50 6

Micromorphology Structure and pores. Generally the structure is massive with laminar arrangement (fabric) of the organic residues. In the top 20-30 cm the laminar arrangement is undulating due to intensive cryoturbation and the formation of thúfur at the surface. The cryoturbation has also distorted the top tephra layer especially in the thúfur. Throughout the profile there are frequent vertical channels associated with larger roots. Below 40 cm woody fragments

80

become frequent and below about 75 cm they are dominant. There are very large pores associated with the woody fragments. They often occur between the bark and the shrinking wood, which also has large discrete pores that reduce the active porosity for water movement. Faecal material and living plant material predominate in the top 5 cm. The living plants are mosses at the surface and roots below. Mediums to very small faecal pellets are found within plant remains, occasionally clustered in the matrix and are being assimilated into the fine organic material. Mineral grains diatoms and phytoliths occur within the pellets. Plant residues. In the middle and lower part of the profile woody residues dominate. The cork is the best preserved tissue with its cells mostly filled with dark brown to black material, probably dense hydrocarbons formed from tannins and other ringed hydrocarbons. In some cases the cork cells are breaking apart. The wood has in all cases separated from the bark tissues due to decomposition of the cambium and phloem tissues but also due to shrinkage of the wood. In some cases the wood has fully disappeared leaving an elliptical ring of bark lying horizontally. Wood vessels fillings are light to yellowish brown indicating a different alteration product than is found in the cork cells. Of the herbaceous residues highly lignified rhizome tissues are the most conspicuous. Rarely bundles of leaves occur but mostly the herbaceous residues are not identifiable. In root residues the epidermis, endodermis and xylem are the most resistant tissues and the cells often filled with yellow, light brown, red or black substances. Organic matrix. The fine organic material can be divided into small plant residues, individual cells, homogeneous substances often associated with other components acting as cementing agent or highly humified material in soil layers, and very small microgranular particles. The microgranular matrix is probably originates from broken pellets. Bog iron. At about 5 cm a thin band of bog iron has precipitated indicating a change in the redox conditions. The bog iron is dominantly black and opaque with massive to granular structure. Some parts are dull red, microgranular breaking up in a blocky structure. Pyrite. Below about 150 cm depth pyrite appears and increases with depth. The pyrite occurs as small, black spheres 10-30 µm in diameter or as fused clusters up to a few hundred µm in diameter. The spheres and clusters are mainly in cavities within plant residues, in cell lumen but also in pores in the fine residues. The pyrite is of biological origin and the spheres are colonies of sulfitic bacteria. Coatings. These occur on both the small granular units as well as on linear pore surfaces at about 30 – 120 cm depth. The pore coatings are bright yellow to yellowish-brown, weakly anisotropic and have a dendritic structure or a fan-like form where the fans are formed from needles growing at right angel to the pore wall. These coatings are mainly associated with woody residues and have been observed in bog iron ores and identified as goethite (Stoops 1983). Volcanic glasses and other primary minerals. Three types of volcanic glasses occur. Firstly, there is light, greyish, fibrous, rhyolitic glass with large inner porosity. Secondly, there is brown glass forming glass shards often with sharp edges, and thirdly black basaltic glass. In the light coloured tephra layers the light coloured rhyolitic glass is dominant. Brown glasses are the most frequent in organic layers together with light coloured in the top part of the profile. An unidentified tephra layer at 168-171 cm depth consists dominantly of brown coloured glasses. Other primary minerals including plagioclase, augite and olivine are rare. References FitzPatrick, E.A., and Th. Gudmundsson. 1978. The impregnation of wet peat for the

production of thin sections. Journal of Soil Science 29: 585-7. Stoops, G. 1983. SEM and light microscopic observations of minerals in bog-ores of the

Belgian Campine. Geoderma 30: 179-86.

81

The effect of acid deposition on ion leaching and weathering rates of an Andosol and a Cambisol

Rannveig Guicharnaud1 and G.I. Paton2

Agricultural Research Institute, Iceland1, Aberdeen University, Scotland2

An evaluation of the respond of an Andosol and a Cambisol to acid deposition and weathering rates was studied by using a controlled laboratory leaching experiment. Both soils where derived from basic parent material, a Histic Andosol from Western Iceland and a Cambisol from North East Scotland. De-ionized water and water acidified with H2SO4 (pH 3) was leached through reconstructed soil columns to simulate 34 years of precipitation. Soil solution leachates where collected weekly for chemical analyses. Measured cations were Ca, Mg, Fe, Na, K, Mn and Si. Measured anions were SO2-

4, Cl- and NO3-. Cations from soil

solution samples were used to calculate wethering rates of both soil types. Acidic input increased cation and anion leaching in both soil types and reduced pH levels. The Andosol proved generally to have higher weathering rates, which were calculated according to Zulla & Billet (1994), leaching potential, ion exchange and buffering capacity. This was due to differences in parent material and mineral composition. The Andosol developed from volcanic tephra, which had higher dissolution rates due to its amorphous mineral structures. The Cambisol was developed from gabbro with more stable mineral structures. Towards the end of the experiment, after 26.6 equivalent years of acid deposition, the Andosol pH values decreased rapidly. At lower pH values SO4

-2 concentrations where higher in the output solution than the input solution. This was due to the Andosol sampling location, 300 m from a smelting factory. The Andosol was therefore receiving SO4

-2 input from the factory prior to the experiment, suggesting a build up of SO4

-2 in the soil. After intense acid leaching, pH values decreased due to a decline in the buffer capacity of the Andosol resulting in increased SO4

-2 concentrations in leachates. Andosol is a soil type known for its great capacity to retain pollution due to its variable charge surfaces and high cation exchange capacity. This experiment shows however that despite the Andosol great capacity to receive pollution, exchange sites can be fully occupied as a consequence of intense leaching of pollutants. This would lead to a decrease in the soil buffering capacity and leaching of pollutants to groundwater until a new equilibrium is reached. References Zulla, Y., and M.F. Billet. 1994. Long-Term Changes in Chemical-Weathering Rates between

1949-50 and 1987 in Forest Soils from Northeast Scotland. EJSS. 45:327-335.

82

Development and composition of surface coatings in volcanic soils

Herre A.1), Lang F.1), Siebe C.2) and M. Kaupenjohann1) 1) Institut für Ökologie, TU Berlin 2) Instituto de Geología, UNAM

Compared to crystalline minerals, volcanic glasses exhibit rather high dissolution rates. As a consequence, the ion activities in soil solution of Andosols can be high enough to allow the formation of amorphous secondary phases like allophane, ferrihydrite, silica or aluminium hydroxide. Besides, Andosols in the vicinity of active volcanoes receive rather large amounts of acid inputs, often in the form of H2SO4 or HF, which in turn accelerate mineral weathering. Also, the added S and F can form precipitates with Al. In the case that precipitates form on the surface of weathering minerals, they could exert a substantial influence on weathering kinetics. We hypothesize the formation of Al-S secondary mineral phases on the surface of primary minerals in volcanic ash soils in the vicinity of active volcanoes. In order to test this hypothesis we analysed samples of sand grains from selected soil horizons using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). Our results show the formation of amorphous silica and Al-S secondary mineral phases. Both seem to form coatings on the surface of weathering primary minerals as well as separate phases. In order to investigate which solid phases are thermodynamically favoured, we will analyse soil solution data using the geochemical model Minteqa2. Using this thermodynamic calculations, we will also test possible explanations for the differences observed between the analysed horizons on their plausibility. Results of these analysis will be shown.

In future research, this topic could be evaluated on a broader band of volcanic ash soils.

83

Application of diffuse reflectance spectroscopy to characterise volcanic soil color and mineralogy

M.V. Sellitto, G. Palumbo, A. Di Cerce, C. Colombo1,

1Dip. Scienze Animali Vegetali e dell’Ambiente, Unversità del Molise, Campobasso, Italy Soil color is an important soil property that has been related to organic matter content of surface horizons, soil moisture regime, and iron oxides content (Stoner and Baumgardner, 1981; Torrent et al., 1983). Color variation within a soil profile is related to its chemical, mineralogical and hydraulic properties although the nature and strength of the relationship has not been well defined (Baumgardner et al.,1985). Volcanic soils are generally very dark in the upper horizons and the for this reason they were named “Andosols” (from the Japanese “An-do”, which means An dark and do soil) while deep horizons consist of bright color varying with the type of volcanic parent material and composition of weathering products. Volcanic soils formed on fresh tephra show various colors ranging from white to black according of the chemical composition and mineralogy of the tephra and organic matter content. Well developed volcanic soils in temperate regions are yellow to reddish brown reflecting the formation of hematite, goethite or ferrihydrite according to the drainage conditions. Poor drainage is favourable to formation of goethite and lepidocrocite (with yellow color). Under well drained conditions, volcanic soils show reddish brown colors indicative of hematitic formation. Despite its pedological meaning, precise methods to measure soil color and soil reflectance properties, have not been extensively studied. The normal method of measuring soil color in the field requires visual matching of a sample with standard color chips (Soil Survey Division Staff, 1993). This method is at best semiquantitative. However, it is limited by the observer subjective knowledge and by the number of Munsell color chips (Baumgardner et al., 1985). Visual measurement in situ was influenced by the lighting condition that was related with geographic position. Direct full sunlight, sunlight filtered by trees, low-angle sunlight, and indoor lighting may result in severe inaccuracy. These limitations of visual measurement techniques result in poor correlation between soil color and soil properties and reduce the application of soil color criteria in soil classification. The specific objectives of this study are to compare field and laboratory soil color measurements and to assess significant correlation between spectral measurements and volcanic soil properties. Reflectance spectra were obtained using disturbed, < 2 mm, gently ground, air-dry soil. Soil spectra were acquired using a Jasco 560 UV-visible spectrophotometer equipped with an integrating sphere of 53 mm diameter, working in the 350-900 nm spectral range, and with a spectral resolution of 0.5 nm. Barium sulphate (Merck DIN 5033) was used as white standard, and CIE parameter (tristimulus coordinates) were calculated and converted to Munsell notation (Torrent and Barron, 1993.). All the whole volcanic soil samples show yellow color (form 0.1 to 3 Y and from 10YR to 7.5YR), with values ranging from 3.8 to 7.4, and chromas ranging from 1.5 to 5.4 according to the spectrophotometric measurements. The visual estimates of the Munsell color value and the spectrophotometer measurements are moderately correlated (Fig. 1a ). Discrepancies between the two measurements may originate by the different lighting conditions and also because the two measurements were taken under different moisture conditions. Visual estimates of Munsell value show more variation than the corresponding spectrophotometer measurements (Fig. 1a). For example, visual estimates of a Munsell value of 3 correspond to spectrophotometer Munsell values ranging between 3.5 to 7 . Munsell value decrease cuvilinearly as OM increased but different populations were observed (Fig. 1b). For example, Italian, Hungarian and Greek soils exhibit significant curvilinear trends while Spain and France soil shown Munsell values that decrease more

84

linearly. A general trend to darker colors was observed with increasing OM content also with the CIE parameter (Fig. 1d). The scatter of the Munsell values and CIE data could be partly correlated to the type of volcanic parent material, the texture and the chemical composition of organic matter (Humic /Fulvic acid ratio etc.). Significant correlation was observed between soil Fe (extracted by dithionite) and Munsell croma, indicating that the Fe bearing minerals are especially important to color development in volcanic soils (Fig. 1c). Soils with high croma contained higher amounts of crystalline Fe oxides and had undergone more intense weathering. Munsell hues of 7.5 YR and high chromas indicate that goethite and hematite were important products of weathering. Many B horizons are lighter. Among B horizons, there are strong differences according to the position in the landscape (redoximorphic features, kind of piroclastic deposit, etc.). These preliminarily results suggest that there was a close relationship between the Munsell parameters, organic matter content and type of iron oxides for volcanic soils; this occurs especially for the soil profiles in the same landscape.

References Baumgardner, M.F., Silva, L.R., Biehl, L.L., Stoner, E.R., 1985. Reflectance properties of

soils. Adv. Agron. 38, 1 –44. Soil Survey Staff, 1999. Soil taxonomy: a basic system of soil classification for making and

interpreting soil surveys, 2nd edition. Agriculture Handbook, vol. 435. USDA, US Government Printing Office, Washington DC.

Stoner, E.R., Baumgardner, M.F., 1981. Characteristic variations in reflectance of surface soils. Soil Sci. Soc. Am. J. 45, 1161– 1165.

Torrent, J., Barron, V., 1993. Laboratory measurement of soil color: theory and practice. In: Bigham, J.M., Ciolkosz, E.J. (Eds.), Soil Color. SSSA, Madison, WI, pp. 21–34.

Torrent, J., Schwertmann, U., Fechter, H., Alferez, F., 1983. Quantitative relationships between soil color and hematite content. Soil Sci. 136, 354– 358.

Munsell Value vs Organic Matter

3

3,5

4

4,5

5

5,5

6

6,5

7

7,5

8

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 40,00

Organic M atte r (%)

Mu

ns

ell

Val

ue

Italy Portugal Iceland Spain

Greece France Hungary

M unse ll Chroma v s Fe Dithionite

0

1

2

3

4

5

6

0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00

Fe Dithionite (g/kg)

Mu

nse

ll C

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ma

CIE Param eters X-Y-Z (tristim ulus) vs Organic Matter(Spectrophotom eter Measurem ent)

0

10

20

30

40

50

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0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 40,00

Organic Matter (%)

X-Y

-Z (

Tri

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mu

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)(S

pe

ctr

op

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tom

ete

r M

ea

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X (Tristimulus) Y (Tristimulus)

Z (Tristimulus)

Relationship betw een in situ and laboratory m easurem ent of Munsell value

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4 4,5 5 5,5 6 6,5 7 7,5

Munse ll va lue Laboratory mea sure me nt

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Soil solution composition and weathering rates of a Histic Andosol, Iceland.

B. Sigfusson1, S.R. Gislason1 and G.I. Paton2 1) Science Institute, University of Iceland, 2)University of Aberdeen, School of Biological Sciences,UK

Chemistry of soil solutions from a Histic Andosol profile in Western Iceland was studied in the field, in repacked laboratory microcosms and undisturbed outdoor mesocosms. The experimental setup allowed simulation of 50 equivalent years of precipitation in microcosms and 4.2 equivalent years in mesocosms. Arnalds (2004) reported that pedogenesis of Icelandic Andosols was governed by the deposition rates of aeolian-andic materials and drainage. Those factors where fixed in the current experimental setup, that is there was no aeolian-andic depostion and the soils drained freely in microcosms and mesocosms. Concentrations of main ionic components in the soil solution correlated with depth (water in contact with soil) rather than to pH values. Soil solution chemistry was controlled by three dominant processes:

a) Dissolution of volcanic tephra, mostly basaltic glass. b) Photosynthetic binding of carbon by surface vegetation and subsequent leaching of

dissolved organic and inorganic carbon into the soil profile. c) Incongruent reaction between allophane and imogolite.

Dissolution of volcanic tephra (in this case primarely basaltic glass) and turnover of carbon near the surface were the dominant processes in near surface horizons. However, incongruent reaction between allophane and imogolite controlled the composition of soil solution deeper than 50 cm in conjunction with dissolution of volcanic tephra. Aluminium released into soil solution from volcanic tephra was primarely complexed into organic complexes according to simulations in PHREEQC (Parkhurst & Appelo, 1999) and was therefore unavailable to form allophane or imogolite in surface horizons. Free aluminium was up to 30 % of total aluminium in horizons below 80 cm and was therefore available to form allophane rather than to precipate and from humus complexes. Fluxes of silicon, aluminium and base cations in soil horizons generally increased downwards as expected (table 1). Weathering rates of horizons in microcosms were on the same order of magnitude as weathering rates from river catchment studies in the vicinity of the research area (Gislason et al., 1996; Moulton et al., 2001; Stefansson and Gislason, 2001). Gislason et al. (1996) reported there was no correlation between vegetation cover and overall chemical denudation rates in river catchments in SW-Iceland. The influence of vegetation cover on weathering rates was clearly observed in current research and those by Moulton et al. (2001). The soil thickness could also be influential on the total denudation rates of river catchments as concentration of dissolved elements will increase downwards the soil profile and rivers draining areas with thin soil covers will therefore have a lower solute concentrations and consequently lower denudation rates.

86

Table 1 Weathering rates of the soil at base of selected horizons and data from other studies. Non-vegetated Chemical weathering rate Precipitation

Microcosms /kmolc ha-1 year-1 /mm year-1 Si Al Ca Mg Na 15 cm 0,40 0,11 0,47 0,17 0,02 540 80 cm 2,28 0,08 0,41 0,23 0,05 540 115 cm 4,04 1,58 0,64 0,13 0,05 540 170 cm 7,05 2,91 4,42 0,93 0,26 540 Vegetated mesocosms: 15 cm 14,25 0,23 4,29 1,37 1,37 540 80 cm 46,20 0,56 6,70 4,18 3,46 540 115 cm 46,99 0,07 9,15 9,28 3,85 540 Drainage waters into Lake Skorradalsvatn, Iceland (Moulton et al., 2001): Soil with no vegetation 1,28 no data 0,25 0,10 0,14 ca. 1500 Soil with conifer cover 3,02 no data 0,48 0,31 0,22 ca. 1500 Chemical weathering of basalt catchments in Iceland (Gislason et al., 1996):

River Laxa, Vogatunga 10 no data 3,09 1,48 1,78 1731a) River Thorsa 17 0,16 3,54 2,14 6,05 1750a) River Ölvusa 23 0,09 3,94 2,06 5,61 2409a) Chemical weathering of basalt catchments in Iceland (Stefansson and Gislason, 2001):

River Bugda 29 0,03 7,42 3,36 no data 4930b) River Sanda 42 0,07 8,66 2,74 1,63 6220b) References Arnalds, O. 2004. Volcanic soils of Iceland. Catena, 36, 3-20. Gislason, S.R., Arnorsson, S. and Armannsson, H. 1996. Chemical weathering of basalt in

southwest Iceland: Effects of runoff, age of rocks and vegetative/glacial cover. American Journal of Science, 296, 837-907.

Moulton, K.L., West, J. & Berner, R.A. 2000. Solute flux and mineral mass balance approaches to the quantification of plant effects on silicate weathering. American Journal of Science, 300, 539-570.

Parkhurst, D.L., Appelo, C.A.J. 1999. User’s guide to PHREEQC (Version 2)- A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. 99-4259, 1-326.

Stefansson, A. & Gislason, S.R. 2001. Chemical weathering of basalts, Southwest Iceland: Effect of rock crystallinity and secondary minerals on chemical fluxes to the ocean. American Journal of Science, 301, 513-556.

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C and N mineralization rates of cultivated Icelandic Andosols

Rannveig Guicharnaud and Hólmgeir Björnsson Agricultural Research Institute, Iceland

Organic matter turnover plays a significant role in the functioning of ecosystems as a source of plant nutrients and as an energy source for decomposition. Organically complexed aluminum, non-crystalline hydroxide, allophane and imogolite have been reported to have a protective effect against biodegradation resulting in slower mineralization rates in andic soils (Boudot, 1992). Most studies of mineralization rates of soils with andic properties have primarily focused on soils formed under warmer climates. The present study aims to explain C and N mineralization in andic soils formed in sub- arctic climate giving this experiment soils a unique position in the Andosol taxonomy. Soils with andic properties were sampled (0-20 cm depth) at three sites in Iceland, Korpa (South West Iceland), Eyjafjörður (North Iceland) and Skagafjörður (North Iceland). At each site three fields with different cultivation history were sampled, a) un-ploughed, b) continuously ploughed for a short period of time, c) continuously ploughed for a longer period of time. However, results can not be used for direct comparison of the effect of cultivation history because of differences between the fields of the beginning the experiment. C and N mineralization was measured by incubation for 21 weeks at 15°C. For mineralized C, CO2 was measured by titration and for mineralized N, NO3

- and NH4+ was measured by the

Kjeldahl-method (Bremmer & Mulvaney, 1982). Incubation samples for mineralized C and N were collected and measured regularly. For studying the minerizable N pool, the function N = N0*(1 – exp(-kt)) was fitted to measured N mineralization patterns where N was the accumulated mineralized N (mg/kgsoil) at each time t (days) and k was the mineralization rate constant (days-1). Measured nitrate concentrations were highest initially during the incubation period due to easily decomposable organic N fractions (Korpa, Eyjafjörður and Skagafjörður). Measured NH4

+ concentrations were under detection limits. C mineralization rates, relative to N mineralization, were in general higher. The percentage of readily mineralizable organic N in the pool of total organic N is small in Andosols compared to that of non-andic soils. Saito (1990) compared the N mineralization potential (No) to the total organic N (Nt ) between Andosols and non-andic soils from North Eastern Japan which had experienced various soil management and cropping. When the Icelandic results were compared to Saito’s results from Japan (table 1) Icelandic rates constants k were greater than those obtained from Japanese andic-soils and comparable with rates constants obtained from Pálmason et al., (1996) (table 1). Andosols from Japan had a greater mineralization potential (No) than Icelandic soils. Furthermore the percentage of mineralizable N (No/ Nt values) were higher in Japanese andic soils. Andic soils from both countries had smaller percentage of mineralized N (No/ Nt values) than non-andic soils. This supports the theory that organic N and C in Andosol is resistant to microbial decomposition which is most likely due to Al bound in insoluble complexes, non-crystalline Al hydroxides, allophanes and imogolite (Boudot, 1992). In addition micro-structures are commonly observed in both surface and subsurface horizons of Andosols and have been reported to be unfavourable for enzymatic reactions with organic N compounds (Saito, 1990).

89

Table 1 A comparison between mineralization parameters of Andosols and non-andic soils from Japan (Saito, 1990) and Icelandic soils. Icelandic Years of k No total N No/Nt

Soils ploughing day-1 15°C mg/kg % % Korpa 0 0,019 32,7 0,49 0,7

2 0,070 39,78 0,51 0,9 7 0,017 58,20 0,57 1,5

Eyjafjörður 0 0,035 64,52 0,9 1,3 6 0,017 69,91 0,7 0,7 13 0,035 91,92 0,8 1,4

Skagafjörður 0 0,012 13,04 0,17 0,7 2 0,034 21,38 0,15 3,4 6 0,030 37,66 0,22 2,1 k

Pálmasson et al., (1996) day-1 20°C other soils 0,0380 1,2 0,21 6,1

andic soils 0,0376 0,9 0,0065 2,7 andic soils 0,0355 20,7 0,0205 3,4 Japanese k

Soils (Saito, 1990) day-1 25°C Andosols 0,0043 176 0,5 3,5

other soils 0,0059 100 0,28 8,2

k= rate constant

No= N mineralization potential

No / Nt = Mineralizable N

This is an ongoing research, and many factors are yet to be investigated in relation to mineralization in Icelandic Andodol’s. Those factors include microbial biomass, clay content and organo-metallic complexes as well as taking into account the affect of a cooler environment on the physiological status of Icelandic Andosols. References Boudot, J.P. 1992. Relative efficiency of complexed aluminum, noncrystalline Al hydroxide,

allophane and imogolite in retarding the biodegration of citric acid. Geoderma 52:29-39. Pálmason, F., H. Þorgeirsson, H. Sigurðardóttir, H. Björnsson, O. Arnalds. 1996. Níturlosun í

jarðvegi. Icel. Agr. Sci. 10:185:208. (in Icelandic, with English abstact). Bremmer, J. M. and C.S. Mulvaney. 1982. Method of Soil Analysis Part 2-Chemical and

Microbiological Properties. Second edition. Am. Soc. of Agro. Inc. 595-622. Saito, M. 1990. Nitrogen mineralization parameters and its availability indices of soils in

Tohuku district, their relationship. Japanese Journal of Soil Science and Plant Nutrition 61:265-272. (in Japanese, with English abstract).

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Soil carbon fluxes during leaching of a Histic Andosol, Iceland - evaluation of scale and sampling techniques.

B. Sigfusson1, G.I. Paton2 and S.R. Gislason1 1) Science Institute, University of Iceland, Reykjavik, Iceland

2)University of Aberdeen, School of Biological Sciences, Cruickshank Building, AB243UU, Aberdeen UK Soil pore water carbon from a Histic Andosol from Western Iceland was studied at three different scales; in the field, in undisturbed outdoor mesocosms and in laboratory repacked microcosms. Pore water was extracted using suction cup lysimeters and hollow-fibre tube sampler devices. There were significant differences in all measured variables, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and pH values between the scales of the experiment. Concentrations of DIC and pH values varied between sampling devices used. Gaseous constituents of soil solution and pH were more susceptible to changes in scale and the type of sampling devices used. DOC concentrations were significantly different near the surface but differences were diminished below 35 cm depth. Field studies considering long anthropogenic changes in pedogenesis require considerable experimental duration though more rapid experiments can be conducted with confidence in micro- and mesocosms as in this research. For the soils studied, nearly twenty percent of the organic carbon bound annually in the soil surface horizon under field conditions was lost by leaching of DOC and through decomposition forming DIC in disturbed non-vegetated microcosms. This percentage increased to 38 % in undisturbed vegetated mesocosms highlighting the importance of surface vegetation on the turnover of carbon in soils. Soils in Iceland become more fertile as aeolian-andic deposition rates increase. The aeolian-andic material partially dissolves at the soil’s surface therefore increasing soil pH values as well as the nutrient status. This results in increased microbial activity and decompostion of carbon. Furthermore allophane will form rather than metal humus complexes at pH above 5. As a consequence carbon is increasingly leached from the soil rather than sequestered at high pH values. Vegetation cover plays an important role in the soils carbon cycle. Vegetation at the soil’s surface binds carbon by photosynthesis. New unstable soil carbon is then leached to groundwater. When the vegetation cover is absent the primary process concerning carbon will be decomposition. Although leaching of carbon is much higher from soil with a vegetative cover, carbon is sequestered due to photosynthesis at the soils surface.

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Biophysical characterization of soils on the island of Santorini (Greece)

E. Vavoulidou1, M. Wood2 and E.J. Avramides1 1 NAGREF, Soil Science Institute of Athens, 2 University of Reading, Department of Soil Science

The island of Santorini is located in the southern part of the Cyclades islands and was formed by consecutive volcanic eruptions. The most recent eruption, approximately 3,500 years ago, resulted in the deposition of a layer of volcanic ash and pumice 30-40 m deep. This is the parent material for the soils of Santorini, which have developed in a Mediterranean climate with a mean annual precipitation of 375 mm and mean annual temperature of 17 oC. The soils have been characterized previously as Andisols, suborder Xerands mainly belonging to the large group Vitric Andisols (Misopolinos et al, 1994). Despite the dry summer, the soils are widely used to cultivate mainly vines and other crops such as tomato. It is believed that dew is trapped by the highly porous pumice thereby increasing the amount of water available for plants in the soil. No information is available on the biological characteristics of soils of Santorini, therefore the aim of this work was to obtain integrated physical and biological data on these soils using a combination of conventional parameters such as particle size analysis, organic matter content and earthworm population size, together with novel biological characterization based on enchytreid populations and hydrolytic enzyme activity. Enchytreids are small worms, 1-50 mm long, which feed upon microorganisms, nematodes and plant litter, and are likely to play a role in nutrient cycling. Hydrolytic enzymes such as cellulase and phosphatase are produced by organisms in soil in order to catalyse the decomposition of large organic molecules such as cellulose and inositol phosphate into smaller monomers such as glucose and phosphate. These enzymes are likely to control the rate of biogeochemical cycling of elements such as C, N, P and S in soil and are therefore good indicators of soil biological quality (Dick, 1994). 47 soil samples were taken from a number of sites which were divided into two categories (a) cultivated soils (vineyards and other crops such as tomato, faba bean, pistachio nuts) and (b) natural sites (Cost 622). Sampling was carried out using a riverside auger to a depth of 20-30 cm. Each sample consisted of five or ten well-mixed cores, which were collected from different points on the site. Sampling of earthworms (Lumbricidae) and enchytreids was performed in the most humid period (at the beginning of spring in 2000, 2001 and 2002). At each site, two areas 50 x 50 cm were treated with a 0.1 % formalin solution to extract the earthworms. A cylindrical core (100 cm3 volume) was used to collect samples for enchytreid abundance studies. Extraction was carried out in the laboratory after 5 weeks of incubation at 20 oC by means of a wet extraction method and their abundance measured using a stereomicroscope. Enzyme activity was measured according to the method of Marx et al. (2001), based on the use of fluorogenic MUB-substrates and microplates. The soil samples were analysed for cellobiohydrolase (EC 3.2.1.91), N-acetyl-β-glucosaminidase (EC 3.2.1.30), β-glucosidase (EC 3.2.1.21), acid phosphatase (EC 3.1.3.2), β-xylosidase (EC 3.2.2.27) and leucine-peptidase (EC 3.4.11.1) using 4-methylumbelliferone-β-D-cellobioside, 4-methylumbelliferone-N-acetyl-β-glucosaminide, 4-methylumbelliferone-β-D-glucoside, 4-methylumbelliferone-phosphate, 4-methylumbelliferone-7-β-D-xyloside and L-leucine-7-amino-4 methyl coumarin as substrates, respectively. All enzyme measurements were made under standard conditions of pH, temperature and soil preparation.

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In addition, soils were analysed for particle size distribution, organic carbon (Walkley Black method), CaCO3, total N, cation exchange capacity, exchangeable cations, Olsen P, pH (in a water-saturated soil paste), and mineral N (ammonium and nitrate). All soils were sandy loam to loamy sand in texture (SL-LS) and had an acid to slightly alkaline reaction. Free CaCO3 was very low except in one region with values up to 15%. This is probably explained by the presence of underlying non-volcanic rock formations. The organic matter content was very variable, ranging between 0.5 to 9.6%. All the agricultural soils contained ≥5 mg kg-1 of available P and two thirds contained > 20 mg kg-1. However, 3 of the 6 natural sites contained only trace amounts. Available K was in the range 0.2 to 0.6 cmol kg-1 soil for most soils. In general, the cation exchange capacity (CEC) was very low, less than 10 cmol kg-1. Total nitrogen (N) was relatively low, but the ratio of total organic carbon to total nitrogen (C: N) was in the normal range (2-14) for inorganic soils. In addition, the concentrations of the nitrate and ammonium ions were found to be at normal levels. No earthworms (Lumbricidae) were found at any of the sites on the island. Enchytreids were found at only 2 of the natural sites with very low abundance (800 and 1600 Ind m-2). A higher percentage (56%) of agricultural soils contained enchytreids, but again their abundance was generally low, with a mean population of 2700 Ind m-2. Hydrolytic enzyme activity was low in most soils sampled when compared to data for soils from wetter regimes (Marx et al, 2001). Enzyme activity is in general strongly related to soil biological activity, and in soils with low levels of organic matter the activity of hydrolytic enzymes such as cellulase is low. The few soil samples from Santorini that had higher levels of organic matter showed higher levels of enzyme activity. In conclusion, on the basis of the above data, the soils of Santorini do not show significant biological activity during the seasons in which the samples were taken. This is likely to be a reflection of the relatively young age of the soils, and the low levels of organic matter. However the situation is likely to be complicated by local factors such as micrometeorological conditions and the impact of parent material on soil water holding properties. It is important that investigations be extended to the wet period of the year in order to confirm these initial findings.

References Dick, R. P. 1994. Soil enzyme activity as indicators of soil quality. In "Defining Soil Quality

for a Sustainable Environment" (J. W. Doran, D. C. Coleman, D. F. Bezdicek and B. A. Stewart, eds.), pp. 107-124. Soil Science Society of America, Madison, Wisconsin.

Marx, M.-C., Wood, M., and Jarvis, S. 2001. A microplate fluorimetric assay for the study of enzyme diversity in soils. Soil Biology & Biochemistry 33, 1633-1640.

Misopolinos, N., Syllaios, N., Prodromou, K. 1994. Physiographic and soil mapping of Santorini island. Edited by the Laboratories of Soil Science and Remote Sensing of the School of Agronomy, Aristotle University of Thessaloniki. pp110 (in Greek).

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Enchytreid reproduction test in volcanic material on Santorini.

E. Vavoulidou1, A. Oikonomou2 and F. Bartoli 1.NAGREF, Soil Science Institute of Athens, Greece, 2.NAGREF. Forest Research Institute of Athens, Greece

3INRA, Laboratoire Sols et Environnement, Nancy, France The aim of this study was to assess whether volcanic soils under Mediterranean climatic conditions can be a habitat for soil organisms such as enchytreids (family of Oligochaeta).

Soil samples were taken from different sites on Santorini Island in Greece. Five cylindrical cores (100 cm3 volume) per site were taken to collect samples for enchytreid abundance studies. These soil samples were transferred to the laboratory where part of each sample was used for counting the Enchytreid population using a stereoscope. The remaining soil from each sample was placed in a box for incubation at 20oC for 10 weeks under a favourable soil moisture regime (maximum water capacity 40-50%) for reproduction tests. The parent material of all the soils studied is pumice and volcanic ash and the soils are fairly young, very skeletic, with an extremely dry moisture regime.

The results were as follows: Enchytraeids population density in the Santorini cultivated volcanic soils was consistently

low (1945 Ind/m2) and its increase after incubation was not statistically significant (2576 Ind/m2). The highest abundances prior to and after the incubation (2571 and 4286 Ind/m2

respectively) were found in the samples taken from sites with faba bean and pistachio nut cultivations The mean lowest abundances prior to and after the incubation (0 and 330 Ind/m2

respectively) was found in samples taken from sites covered with natural vegetation. From the micromorphological analysis of the three natural sites included in the study, no

significant enchytreid activity was observed. A few casts of dipteral larva were present in one sample. This agrees with the complete lack of enchytreids in these three soils, which is in contrast to the cultivated soils of the island, particularly the soils located on lower ground.

The preliminary results show that in extremely dry Mediterranean conditions, the young volcanic soils do not enhance the soil fauna activities.

Further, more frequent, sampling needs to be performed in the “humid” period in order to ascertain whether the relatively limited abundance of soil organisms (enchytreids) in April, when this study was carried out, was due to the soil moisture regime at that time of year in this volcanic habitat or is a more general phenomenon.

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95

P adsorption and desorption capacities of andisols from European volcanic areas

E. Auxtero and M. Madeira

Departamento de Ciências do Ambiente, Instituto Superior de Agronomia, Tapada da Ajuda, Lisboa, Portugal

Most andisols contain large amounts of active Al and Fe, allophane, and organic C, which greatly influence the capacity of soils to adsorb and desorb P. Phosphorus deficiency has been identified as one of the limiting factors to crop production in andisols. Additionally, potential losses of P from agriculturally P enriched areas to nearby bodies of water may enhance eutrophication thereby degrading water quality. In order to provide insight for developing P management strategies, the ability of the soil to adsorb P and its relative desorptive characteristics should be studied. Having this in view, a study on surface (Ah or Ap ) and subsurface (Bw or BC) horizons of eighteen pedons of andisols selected from representative volcanic areas of Italy, Portugal, Iceland, Spain (Tenerife), Greece, France and Hungary was conducted to 1) determine the P adsorption capacity using Langmuir isotherm, 2) determine the P desorption capacity using eight successive extractions with 0.01 M CaCl2, and 3) assess the relationships between adsorption-desorption parameters and selected soil properties.

Phosphorus sorption data were determined by the method of Fox and Kamprath (1970). This was done by adding 20 ml of 0.01 M CaCl2 solutions containing various concentrations of phosphate as KH2PO4 to 2 g of soil in 50 ml plastic centrifuge tubes. The suspensions were shaken reciprocally for 30 min twice daily within 6 days at room temperature. Filtered P in the supernatant solution was determined by the ascorbic acid blue color method (AAB). Adsorbed P, Ads P (g kg-1) was estimated as Ads P = (Ci-Cf)V/W, where: Ads P: adsorbed P (g kg-1) Ci: initial P concentration added (µg mL-1) Cf: P concentration in supernatant solution after equilibration period (µg mL-1) V: volume of P added (mL-1) W: the oven-dried weight of the soil (g)

Calculated adsorption data were then fitted to the linear form of Langmuir equation as C/Ads P = C/Ads max + 1/k Ads max, where: C: equilibrium P concentration (µg mL-1) Ads P: amount of P sorbed (g kg-1) Ads max: Langmuir adsorption maximum (g kg-1) k: constant related to the P binding strength

The values of C/Ads P were plotted against C and a linear curve is fitted to the scattered points to obtain y = a + bC. The value of b obtained from this linear fit was calculated as 1/b, representing the Langmuir adsorption maximum (Ads max). The k was then estimated by multiplying the Ads max value with the intercept from the linear fit.

Phosphorus desorption isotherms were obtained by equilibrating duplicate 2 g of soil with 20 ml of 0.01 M CaCl2 solutions containing respective Langmuir Ads max concentration of phosphate as KH2PO4 in 50 ml plastic centrifuge tubes, for 6 days at room temperature. The suspensions were shaken for 30 min twice daily within the equilibration period using reciprocal shaker. Filtered P in the supernatant solution, determined by the AAB method represented the initial value for adsorbed P. P saturated soils were then subjected to sequential desorption. This was done by adding 20 ml of 0.01 M CaCl2 to these saturated soils, followed by 2 h of shaking using a reciprocal shaker. Samples were then centrifuged for 10 min and filtered. This procedure was repeated for eight successive extractions. Filtered P in the

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supernatant solution for each extraction was determined by the AAB method. Desorbable P was estimated as % of sorbed P remaining after 8 successive extractions.

Results showed that P adsorption isotherm patterns of the studied soils differ widely in relation to their extractable Al and Fe, and allophane contents. P adsorption values in the surface horizons from lowest to highest order were: 0.002-1.01 g P kg-1 (Greece), 0.39-2.08 g P kg-1 (Hungary), 0.19-6.70 g P kg-1 (Italy), 0.95-12.18 g P kg-1 (Tenerife), 4.22-16.88 g P kg-1

(Iceland), 6.80-18.31 g P kg-1 (France), 8.89-20.71 g P kg-1 (Portugal). Similar order was shown in the subsurface horizons with values: 0.01-0.04 g P kg-1 (Greece), 0.19-2.60 g P kg-1

(Hungary), 0.05-17.60 g P kg-1 (Italy), 1.02-10.57 g P kg-1 (Tenerife), 2.11-16.35 g P kg-1

(Iceland), 6.27-37.39 g P kg-1 (France), 9.52-48.43 g P kg-1 (Portugal). P sorption isotherms of studied soils fitted the Langmuir equation. Values of Langmuir P adsorption maxima (Ads max) were strongly correlated with Alo (r = 0.91, p < 0.05) and allophane (r = 0.86, p < 0.05) contents, and values of Alo + ½ Feo (r = 0.91, p < 0.05) and of ferrihydrite + allophane (r = 0.87, p < 0.05). Positive correlations between Ads max values and contents of Ald, Feo, (r = 0.77, p < 0.05) and Alp (r = 0.49, p < 0.05), and P retention (PR) (r = 0.73, p < 0.05) were also found. Ads max values in highest to lowest order were: 10.81-51.95 g P kg-1 (Portugal), 10.06-27.54 g P kg-1 (France), 4.59-15.29 g P kg-1 (Iceland), 3.17-13.23 g P kg-1 (Tenerife), 0.02-12.82 g P kg-1 (Italy), 1.61-2.27 g P kg-1 (Hungary) and 0.02-0.50 g P kg-1 (Greece). Within andisols, the highest Ads max were observed in Bw horizon of Acrudoxic Hydrudands and Alic Hapludands. The lowest were determined for Vitrixerands and non-andisols (Xeropsamments and Xerothents).

Percentage of P sorbed in the soil after eight successive extractions with 0.01 M CaCl2 showed strong negative correlation with both Feo and ferrihydrite (r = -0.61, p < 0.05), Alo + ½ Feo (r = -0.60, p < 0.05), ferrihydrite + allophane (r = -0.61, p < 0.05) contents and values of PR (r = -0.76, p < 0.05). They also showed weak negative correlation with Alo (r = -0.58, p < 0.05), Ald (r = -0.54, p < 0.05), Alp (r = -0.44, p < 0.05), Fep (r = -0.39, p < 0.05) and allophane (r = -0.58, p < 0.05) contents. Samples from Italy and Iceland (22-100% and 73-100%, respectively) showed the highest percentage of P desorbability. Other samples from Portugal (6%-75%), Spain (Tenerife) (16-77%), Hungary (29-42%), Iceland (7-24%) and France (13-20%) showed low percentage P desorbability. The lowest values were observed for Acrudoxic Hydrudands. Differences in the amounts of P desorbed by the soils suggested that the critical P levels needed for P management must be different.

We thank all members of COST ACTION 622 for the selection of the reference profiles, Otto Spaargaren for soil classification and Isabel Meireles for technical assistance. References Fox, R.L., and E.J. Kamprath. 1970. Phosphate sorption isotherms for evaluating the

phosphate requirements of soils. Soil Sci. Soc. Am. Proc. 34: 902-907. Villapando, R.R., and D.A. Graetz. 2001. Phosphorus sorption and desorption properties of

the spodic horizon from selected Florida spodosols. Soil Sci. Soc. Am. J. 65: 331-339.

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Distribution and bioavailability of heavy metals in Icelandic Soils.

Julian J.C. Dawson1, Olafur Arnalds2 and Graeme I. Paton1 1Soil Science Group, School of Biological Sciences, Cruickshank Building, University of Aberdeen

2Agricultural Research Institute, Reykjavík, Iceland Introduction Heavy metals perhaps pose their greatest threat when derived from anthropogenic sources. There is a wide distribution of these contaminants throughout the world derived from a wide range of sources including fuels, paints, cosmetics, tyres, sewage and animal wastes, piping and industrial effluents. However, metals and metalloids occur at elevated concentrations in a wide range of environments and are the focus for significant ecological monitoring. The minerals associated with Andolsols are known to contain elevated levels of a range of metals and metalloids. As the soils mature through weathering, these metals become distributed throughout the soil profile. To fully assess the presence of metals and their likely environmental impact an intense sample regime was undertaken. The correlation between target elements, Fe and Al can be used to assess if the source is geochemical or anthropogenic. Analysis of vegetation can be used to evaluate food chain transfer impacts and the burden that the metals impose upon plant responses. Aims and objectives The aims of this study were to-

• Assess the concentration of metals and metalloids in Icelandic soils and vegetation • Relate the doses of analytes to the soil types • Quantify the bioavailable fraction of the target metals and metalloids • Consider the likely source of these pollutants.

Materials and Methods Sampling An intense sampling regime was developed in Iceland in September 2000. Samples were collected from thirty four locations representing a range of soil types, topography, vegetation and altitude. Inert sampling procedures were used to avoid cross contamination of the soils and vegetation and the samples were taken back to Aberdeen under controlled conditions. Analysis Metal analysis was carried out using a standard Aqua Regia digestion followed by ICP-MS analysis. Confirmatory analysis was also carried out by hand-held XRF. The same techniques were used to analyse vegetation samples. Water extractions were also performed and correlated with the other measurements. Toxicity assessments Bioluminescence-based biosensors were used to assess the bioavailability of residual metal fractions in the samples (Tiensing et al., 2001; Flynn et al., 2003). Results and discussion Elevated levels of metals and metalloids were most prevalent in the Andosols. Although they were also detected in the Histosols, it was likely that the source was the ash deposits, visible in the profiles. The desert soils showed little evidence of elevated metal levels. In the soils,

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concentrations of Zn, As Ni and Cr all correlated closely with Fe and Al levels hence it may be assumed that these elements have come from geochemical sources. Pb, Cd and Cu showed close correlation for most of the data but the outliers could be related to localized anthropogenic sources either through land-use or nearby domestic, industrial or infrastructural activities. The relationship for the vegetation was quite different than for the soils. For Pb and Cu the metal levels in the plant rose with the Fe associated fraction. The converse observation was made for the other elements. In particular Cd and Ni had a dose response relationship. Metal accumulation in the vegetation closely correlated with the metal levels in the soil. The relationship, however, was better explained by introducing other soil parameters including SOM, pH and soil texture. An estimation of likely metal assimilation was made and could be related both to the plant dry matter and the plant species. Despite the relatively elevated metal loadings in the soil, there was little evidence to suggest that the elements were posing an acutely toxic effect. There was a degree of correlation between the sensor responses and the assimilation into plants though the ouliers could be explained by means of the source of the contaminants. Conclusions Most of the elevated levels of metals in the soils of Iceland can be explained by the presence of volcanic deposition in the pedosphere. Some metals and metalloids are associated with anthropogenic sources and these are visible as outliers in the correlations. Plant assimilation is related to the soil metal loadings. Although elevated, the metals and metalloids appear to have little acute toxicity. References Flynn HC, Meharg AA, Bowyer PK, Paton GI. 2003. Antimony bioavailability in mine soils.

Environmental Pollution 124, 93-100. Tiensing, T., Preston, S., Strachan, N., Paton, GI. 2001. Soil solution extraction techniques for

microbial ecotoxicity testing: a comparative evaluation. Journal of Environmental Monitoring 3, 91-96.

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Acid neutralizing capacity of Andosols: Effects of weathering stage and sulfur storage

T. Delfosse, P. Delmelle and B. Delvaux

Soil Science Unit, Université catholique de Louvain, Belgium Soil acidification remains an important environmental issue because it alters soil and water properties, and thus potentially modifies current processes in whole ecosystems. The capacity of a soil to neutralize acid inputs depends mainly on reactions involving mineral weathering and ion exchange, therefore the acid neutralizing capacity of the soil solid phase (ANCs) has been successfully used to evaluate the degree of soil acidification. However, despite their agronomical importance, the response of Andosols to increased atmospheric acid deposition has been poorly investigated.

Here, we report on the effects of (natural and experimental) elevated acid and sulfur depositions on ANCs in two distinct Andosols transects located downwind from Masaya volcano (Nicaragua), one of the world’s strongest sources of SO2. The first transect comprises Eutric Andosols rich in allophanic constituents, and the second involves Vitric Andosols rich in volcanic glass.

Prolonged acid inputs have led to a general pH decrease and a reduction in exchangeable base cation concentrations. However, the ANCs was not significantly affected by the volcanogenic acid inputs. Non-exchangeable (mineral reserve) and exchangeable cations, total contents of sulfur and phosphorus dictate most of the ANCs variation. In the Vitric Andosols, mineral reserves contributed up to 97 % to these four additive pools, whereas the exchangeable cations accounted for 1-4 %. In the Eutric Andosols, the contribution of mineral reserves was comparatively smaller (71-92 %), but the content of exchangeable cations was larger (1-20 %), whereas the contribution of soil sulfur was substantial (1-15 %). Acid leaching column experiments indicate preferential Al and Si lixiviation in Vitric Andosols, and preferential base cation lixiviation concomitantly with anion accumulation in Eutric Andosols. These results indicate that the main process involved in neutralization of acid inputs is mineral weathering in Vitric Andosols, and cation and anion exchange in Eutric Andosols.

Despite higher ANCs of Vitric compared to Eutric Andosols, soil pH was smaller in Vitric than in Eutric Andosols because the reactions involved in the regulation of volcanic acid flux are kinetically different, ion exchange being much faster than mineral weathering. This observation emphasizes the importance of the acid-buffering capacity compared to mineral weathering of soils to resist rapidly to acid deposition.

Prolonged addition of volcanogenic S increased the inorganic sulfate content of the Andosols up to 5.5 g S kg-1, one of world’s largest soil S content. Inorganic sulfate was stored mainly in the clay fraction, and composed of three pools: adsorbed on short-range ordered minerals, occluded SO4

2- in ferrihydrite, and precipitated in Alx(OH)y(SO4)z mineral. The fate of inorganic sulfate in soils may thus have two conflicting effects: SO4

2- retention contributes to acid-buffering through OH- release or H+ consumption, but also results in ANCs depletion because it stores SO3, the release of which would lead ultimately to sulfuric acid production.

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Phosphate sorption of European volcanic soils

Gy. Füleky Szent István University Gödöll� Hungary

Hypothesis: The P adsorption isoterms give more information about the soils developed on volcanic material than the phosphate retention percent. Method: 1 g soil was equilibrated with 0; 50; 100; 500; 1000; 3000; 5000 and 10 000 mgkg-1

respectively, for 24 hours. Data analysis: P isotherms

Langmuir equation ck

ckPadsPads

⋅+⋅⋅

=1

max

The P ads max, the maximum amount of phosphate could be sorbed, can be used as a soil characteristic in further statistical calculations. Soils:19 European volcanic soil profiles and other Hungarian, Rumanian and Slovakian volcanic soils (n = 126). Fig.1. demonstrates the shape of soil phosphate adsorption isoterms of low and high phosphate adsorption capacity. Some soils of high phosphate fixing capacity can adsorb much more phosphate than 5000 mgkg-1, the applied concentration at Pret% determination. At the same time k value, which is in correlation with the bonding energy, could explain the uncovered relationships. That is the soils of No5; 6; 10 and 15 which bond the phosphate more strongly.

Figure 1 P adsorption isotherms of some European volcanic soils Table 1. Linear relationship between some soil characteristics and P adsorption maxima Soil characteristic R2 Soil characteristic R2 Soil characteristic R2 Alp/Alo No Bases 0,1543 Feo % 0,651 Feo/Fed No CEC 0,3998 Ald % 0,711 Base saturation % No P retention % 0,449 Alo % 0,724 pHH2O No Fed % 0,479 Alo% + ½ Feo % 0,724 Exchangeable Ca No Allophane (Parfitt) 0,633 Alo % + Alp % 0,732 Total organic C% 0,139

10 Bw2b 6 ABw 5 Bwc1 6 A1 16 Ah2 5 Ah1 8 Bw1

4 2Bw2 HG O

8 4c 1 Ap 2 2BC2 0 200 400 600 P mgdm-3

Pads max mgkg-1

9000

5000

1000

101

0

2000

4000

6000

8000

10000

12000

0 2 4 6 8 10 12 14

AlO+1/2FeO %

P ads.max mgkg -1

62A

B

62B

W

62BW

262B

W1

6AB

15Ah3

15BW

6A1

5BW/

52B

10BW

10B

10BW3

4Ah2

16Ah3

16BW

1 52Ah

15Ah2

7A2

162B

w

7BW

3

16Ah2

15Ah

1

4A7BW2

9H1

KhlBW

15R7

O

4

O

G

52C18A27A

92H3Ah1

16Ah

1KhlA/B

W

12A

2

12A1

12B

W102BW

h122A1b 11A

112b

w

82bw

WA

W2Bb/

C

9A42BW

83BW/4C3Ah

11C1

84C

9C

2A1 112BC

W2BW

32AB

17Ah2

10BW3b♦

Figure 2 Linear relationship between Alo % + 1/2 Feo % and the P adsorption maxima of European volcanic soils Conclusions:

• The Langmuir isotherms describes well the phosphate adsorption phenomena in a large interval (0 and more then 10 000 mg kg-1).

• Allophane content (Alo+1/2 Feo %) explains in 72 percent the phosphate sorption capacity of soils (Fig.2). In some cases the bases could be the possible further explanation for some part of the remaining 28 percent. There is a hyperbolic relationship between the bases and P adsorption maxima. The very low bases correlate well with high P adsorption maxima (No5; No6 and No10).

• Oxalate soluble Al alone explains the P adsorption the same rate as allophane, Feo alone somewhat less.

• In some cases Alo+1/2Feo over estimate the P adsorption maximum (No6 B and No15 A and B horizons) and in some cases underestimate it (No5, No10).

• In the case of No10 Bw3b horizon the extremely high dithionite soluble Fe responsible for the discrepancy.

• Adding pirophosphate soluble Al to the Alo values the increase of R2 is very small. References Füleky Gy., and Tolner L. Gemeinsames Modell der P-Adsorption und P-Desorption in

Boden. Tagungsbericht Nr.289 Justus von Liebigs Werk - Wegbereiter der wissensachaftlich begründeten Düngung, Adl Berlin, pp 291-298 (1990)

Mizota C., and L. P. van Reewirjk. Clay mineralogy and chemistry of soils formed in volcanic material in diverse climatic regions. ISRIC, Wageningen 1989

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Characterization of reactive components using selective dissolution methods, and their relation to soil properties in European Volcanic Soils

E. García-Rodeja1, J.C. Nóvoa1, X. Pontevedra1, A. Martínez1 and P. Buurman2

1Dept. de Edafología y Química Agrícola. Facultad de Biología. Universidad de Santiago de Compostela. 2Laboratory of Soil Science and Geology. Wageningen University.

Soils developed from pyroclastic materials are characterized by a mixture of short range order components such as allophane, imogolite, ferrihydrite, opaline silica and/or Al(Fe)–humus complexes, in addition to the crystalline minerals halloysite, gibbsite, goethite, and aluminised 2:1 phyllosilicates. The accumulation of highly reactive components formed upon rapid weathering of volcanic rocks is the main cause for the unique physical and chemical properties of Andosols. Different selective dissolution methods (SDM) are used to quantify and characterize some of these components, but it’s the specificity of such methods is limited by the existence of a continuum between very short-range ordered to crystalline components. After a previous study on the fractionation of Al and Si in some volcanic soils (García-Rodeja et al., 2004), we evaluate several selective dissolution methods (SDM) for Al, Fe, Si and Mn, their use in the characterization of soil components and their relation to some of the characteristic properties of these soils. The soils, formed under different environmental conditions and with contrasting properties, were 20 COST Action 622 European reference volcanic soils from Italy (EUR01-04), Portugal (Azores, EUR05, 06), Iceland (EUR07-09), Spain (Tenerife, EUR10-12), Greece (EUR13-15), France (EUR16, 17) and Hungary (EUR18-20). The SDM and the elements measured were: i) 0.5 M NaOH (Aln, Sin): (Borggaard, 1985); ii) 0.2 M NH4 oxalate-oxalic acid at pH 3 (Alo, Feo, Sio, Mno) (Buurman et al., 1996), iii) Na citrate-dithionite (Fed, Mnd,

Ald, Sid) (Holmgren, 1967; iv) 0.1 M Na–pyrophosphate (pH 10) (Alp, Fep) (Buurman et al., 1996) and v) 0.5 M CuCl2 (pH 2.8) (AlCu) (Juo and Kamprath, 1979). Total contents of these elements were determined by XRF. NaOH dissolved less than 5% of total Al (Alt) from the soils from Greece, Hungary and EUR01 and EUR02 from Italy. In the remaining soils, Aln represented >10% and frequently >20% of Alt (in soils from France and Azores the dissolved fraction was 25-55% of the total). Since oxalate and NaOH extracted approximately the same quantity of Al (r2=0.96, slope 0.96), the origin of the extracted Al is allophane, imogolite and/or Al-humus complexes. Main exceptions are some horizons from the soil EUR2 where the relatively higher Aln values are attributed to the dissolution of gibbsite and possibly some halloysite. The extractable fraction of Si was very small: <10% was extracted by NaOH or oxalate extracted <10% of total Si from most soils, and even less (<4%) from the soils from Greece, Hungary and EUR01 and EUR02 from Italy. Higher amounts were found in some horizons of EUR16 from France, EUR10 from Tenerife and EUR5 and 6 from Azores. NaOH and oxalate exctracted similar amounts of Si: r2=0.82, slope 1.12. Free iron (Fed) represented a small fraction of total Fe content (Fet) in the soils from Greece (<10% of Fet), followed by the soils EUR09 and EUR11 (11-24%). In the other soils Fed represented between 25-70% of Fet, with the highest relative amounts in EUR06 (>70% in all horizons). Crystalline Fe oxides are dominant (Feo/Fed<0.5) in the soils from Hungary, Greece, EUR01-03from Italy, EUR10 and especially in EUR12 (Feo/Fed<0.2) from Tenerife, together with some horizons of EUR05 and 06 from Azores, and EUR07 and 08 from Iceland. In the other soils Feo/Fed is >0.5 indicating the dominance of non-crystalline Fe components, which predominate in the soil EUR17 from France (Feo/Fed>0.8). The effect of oxalate extraction on minerals as magnetite and the need of more than one extraction to dissolve all

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Fe oxides must be taken into account to interpret these results (see Buurman et al., this volume). The Alp/Alo ratio was <0.5 in most samples, indicating that the reactive Al pool is dominated by inorganic constituents. The content in allophane, estimated according to Mizota & van Reeuwijk (1989), which is well-correlated with allophane contents estimated from Sio (r2=0.93), ranged from negligible in the soils from Greece, Hungary and Italy (EUR01 and 02) to more than 20% in some horizons from France and Azores. In general, the higher allophane contents occur in horizons with pHwater between 5.5-6.5. The average Al/Si molar ratio ranged from 1.7 in the soils from Iceland to 2.7 in those from Azores, with intermediate values in the other soils (1.9, in Italy; 2.1, in France; 2.6, in Tenerife). In spite of the dominance of the inorganic Al-pool, Al-humus complexes are an important component in many soils. Their proportion increases with carbon content (Alp/Alo vs C content r2=0.76, excluding the soils with very low Alp). In most horizons, CuCl2 extracted about of 35% of Alp (r2=0.96), suggesting that it constitutes a specific fraction of organically-complexed Al (García-Rodeja et al., 2004). In many mineral horizons with allophane, AlCu is highly correlated to CEC (r2=0.76), which suggests that Al dominates the adsorption complex. The content in ferrihydrite (calculated from Feo) is usually less than 2%, although it exceeds 4% in some horizons from Azores and France. As with allophane, the higher ferrihydrite contents occur in the pH range 5.5-6.5. Calculating ferrihydrite directly from Feo suggests that there is no extractable Fe in humus complexes. Because pyrophosphate extracts quantities equal to 5-100% of Feo, this assumption is irrealistic. Fep clearly increases with C content in soils EUR03 and 04 from Italy (r2=0.99) and in those from Azores, Iceland and France (r2 0.73-0.75, excluding horizons with very high C contents). Extractable manganese is clearly more abundant in the surface horizons of the soil EUR07. Citrate-dithionite extracted from >80% (soil EUR20) to <10% (soil EUR09) of Mnt. Mno was close to Mnd in the soils from Hungary or France, but clearly lower in EUR10 and 12. Good correlations of Mnt with Mnd (r2=0.96) and of Mnd with Mno (r2=0.97) were found for the whole data set, but r2 decreases if the 3 horizons richer in Mn are excluded from the regression analysis. References García-Rodeja, E., Nóvoa, J.C., Pontevedra, X., Martínez, and A., Buurman, P. 2004.

Aluminium fractionation of European volcanic soils by selective dissolution techniques. Catena 56:155-183.

Borggaard, O.K. 1985. Organic matter and silicon in relation to the crystallinity of soil iron oxides. Acta Agriculturae Scandinavica 35, 398– 406.

Buurman, P., van Lagen, B., and Velthorst, E.J. (Eds.) 1996. Manual for Soil and Water Analysis. Backhuys Publishers, Leiden, The Netherlands. 314 pp.

Buurman, P., Meijer, E.L., Fraser, A., and García-Rodeja, E. 2004. Extractability and FTIR characteristics of poorly-ordered minerals in a collection of volcanic ash soils. This volume.

Juo, A.S., and Kamprath, E.J. 1979. Copper chloride as an extractant for estimating the potentially reactive aluminium pool in acid soils. Soil Sci. Soc. Amer. J. 43:35–38.

Holmgren, G.G.S. 1967. A rapid citrate-dithionite extractable iron procedure. Soil Sci. Soc. Amer. Proc. 31:210-211.

Mizota, C., and van Reeuwijk, L.P. 1989. Clay mineralogy and chemistry of soils formed in volcaic material in diverse climatic regions. International Soil Reference and Information Centre, Soil Monograph 2, Wageningen.

104

GIS for the geochemistry of surface waters in Northeastern Iceland

Marin Ivanov Kardjilov1, Sigurður Reynir Gíslasson2, Guðrún Gísladóttir1 and Árni Snorrason3.

1Department of Geology and Geography, University of Iceland. 2Science Institute, University of Iceland. 3Hydrological Service of the National Energy Authority, Iceland.

Land surface hydrologic processes play an important role in the global water cycle. Besides the study of the precipitation, the definition of the water dissolved and suspended fluxes and water chemical composition has recently meteorology, digital weather and flood prediction models, mitigation of the hydro- geological risks and studies of climate dynamics. gained increasing attention in hydrology, agronomy,

The overall goal of this study is to use GIS (Geographic Information Science) to distribute spatially and to visualise the geochemistry of the surface waters of selected rivers in Northeastern Iceland. These rivers were chosen because: 1) enormous database for the dissolved constituents exists (Gislason et al. 2003) 2) they drain almost exclusively basalt/basaltic glass catchments, 3) they experience limited but variable biological activity, 4) they drain catchments of variable glacier cover and 5) they are unpolluted.

The runoff map of Iceland by Haukur Tómasson (1982) was used for spatial modelling. The dissolved river water data for the period of 1998-2003 was taken form Gíslason et al

(2003). There is a conspicuous relationship between the concentration of most dissolved constituent and the discharge of the rivers, and the relationship changes from one catchment to another. This reflects probably the age of rock, glacier cover, vegetation etc. This relationship has been described by power functions (Gíslason et al. 2003). In the present study, the concentration versus discharge relationship is cast in terms of runoff rather than discharge. Runoff is simply the discharge at the sampling spots divided by the catchment area above the sampling spot. Within each catchment, runoff is the dominant variable for the variation in chemical concentration. This provides the opportunity to use runoff maps, to spatially distribute river water concentration data, and makes it possible to predict surface water concentration anywhere within the catchment. The first dissolved constituents distributed spatially, are the one that stem only from weathering of rock; alkalinity and silica. Other dissolved major constituents, such as Na, Ca, Mg, S and K originate both from weathering of rock and precipitation. Before they are spatially distributed, they are corrected for what was brought in with precipitation, using their Cl-ratio and assuming that all dissolved Cl in the river water is brought in by precipitation.

The spatially distributed values provide opportunity to study relationships between the geochemistry of the surface water and the geographic distributed phenomena such as age, slope, vegetation cover etc.

This study is the first attempt to use GIS to distribute spatially and to visualise dissolved constituents within the river catchments in Iceland. Later, this approach can be used to create atlas of geochemistry of surface waters in Iceland. Furthermore, user-friendly Internet based GIS has been developed for these catchments. This GIS approach makes it possible to create limitless number of maps and spatial queries.

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References Tómasson, H. 1982. Vattenkraft i Island och dess hydrologiska förutsätningar. Orkustofnun,

Skýrsla OS-82059/VOD-10. Gíslason, S.R., Árni Snorrason, E.S. Eiríksdóttir, B. Sigfússon, S.Ó. Elefsen, J. Harðardóttir,

Á. Gunnarsson, E.Ö. Hreinsson, P. Torsander, M.I. Kardjilov and N.Ö. Óskarsson. 2003. Efnasamsetning, rennsli og aurburður straumvatna á Austurlandi, IV. Gagnagrunnur Raunvísindastofnunar og Orkustofnnunar. Raunvísindastofnun, RH-04-2003.

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Mercury accumulation in European volcanic soils with special reference to the role of the properties of andic horizons

J.C. Nóvoa; X. Pontevedra; A. Martínez-Cortizas and E. García-Rodeja

Dep. de Edafoloxía e Q. Agrícola, Fac. Bioloxía, Univ. de Santiago de Compostela. Galicia, España. Mercury is considered to be a global pollutant due to its ability to undergo long distance transportation in the atmosphere and because is able to promote adverse effects on environment and human health. Volcanoes represent a significant natural source of Hg in the atmosphere and some estimates range from 20 to 2000 t of Hg per year for global flux (Nriagu & Becker, 2003). Mercury emitted from volcanoes reaches the atmosphere through cataclysmic eruptions, supplying enough volatile Hg to change the global and regional cycle of Hg in a few years (Coffey, 1996), and through passive degassing and moderate eruptions which can have long-term effects on the local environments. In both cases volcanogenic Hg can readily enter into the ecosystem and thus, can constitute a hazard to the environment and to human health. More than 90% of the released Hg enters the terrestrial ecosystems (Lindqvist et al., 1991) being the soils the largest Hg sink. Nevertheless, the Hg content of volcanic soils cannot be used as an indirect estimate of the amount of Hg emitted for volcanoes. Hg accumulation in volcanic soils results from complexes interactions between atmospheric deposition, soil retention and Hg released from soil (Gustin et al., 2002). In Europe, the volcanic activity is or was present in different areas like the Mediterranean Sea (Italy and Greece), the Atlantic Ocean (Azores Islands, Portugal; Iceland and Canary Islands, Spain) and in continental areas (France and Hungary). Twenty COST 622 reference soil profiles (94 soil horizons) were selected in these volcanic regions to determine the total Hg content, the degree of soil Hg accumulation using enrichment factors and the relationships between total Hg and outstanding volcanic soil properties, in order to provide an insight on Hg geochemistry in these soils in Europe. Mercury concentrations were measured, by duplicate, in air dried and ground soil samples of the fine earth fraction using an LECO-ALTEC AMA-254 Hg Analyzer (detection limit: 0,05 ng; working range: 0,05-600 ng of Hg g-1 dry matter). Standard reference materials (NIST 1547 and NIST 1633b) were run within each set of analysis and the values obtained were in the precision range for each standard. Differences between soil replicates are less than 1 %. The highest total Hg values were found in soils from Italy (profile N1), Azores Islands (profiles N5 and N6) and Canary Islands (profile N10). Most of the horizons of these soils have Hg concentrations above 200 ng g-1 of dry soil. The lowest values were measured in horizons from Iceland (N7, N8 and N9), Greece (N13, N14 and N14a) and Hungary (N17, N18 and N19) soils, for which total Hg content is below to 100 ng g-1 of dry soil. These results show that a clear trend between total soil Hg content and the volcanic activity for different geographical areas (Atlantic Ocean, Mediterranean basin or continental Europe) cannot be established. Regarding to Hg content, some of the horizons presented values higher than those recently published by Tomiyasu et al (2003) for Japanese volcanic soils, although most of them are in the range published by these authors (6.5-229 ng g-1 dry matter). Vertical profiles of total Hg in the soils revealed a strong Hg accumulation in the upper horizons (O and A horizons). This trend in Hg distribution with depth is probably associated to soil organic matter, which has been considered a strong Hg adsorbant (Lindqvist, 1991; Tomiyasu et al., 2003).

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Mercury enrichment factors (HgFE), which were calculated by normalizing to total Al content in the deepest mineral horizon, showed values above 10 in upper horizons of the profiles N-2, N-3 and N-4 (Italy), N-5 (Azores Islands), N-7 (Iceland), N10 (Canary Islands), N-14 (Greece) and N-15 (France). It is in the latest soil where HgFE reach the highest value, 30. On the other hand, HgFE lower than 5 were found in soils from Hungary (N-17, N18 and N-19), Canary Islands (N-12), Greece (N-13 and N-14a), Iceland (N-9) and France (N-16). The mean value of HgFE for upper horizons of all the studied profiles is 7.4 ±6.8 and the vertical profile of HgFE is quite similar to the vertical distribution of total Hg content, according with the strong Hg accumulation that was observed. The maximum concentrations of total Hg found in upper horizons can be related to a higher degree of soil evolution. It means that, during long periods without significant volcanic activity, the pedogenetic processes can lead the soil towards an increase of soil organic matter content as a consequence of the establishment and development of vegetation. This idea was exposed by Tomiyasu et al. (2003) to explain the similarities between total Hg and soil organic matter distribution in volcanic soil from Japan. In addition, other properties of soils developed from volcanic materials, as the presence of components like Al(Fe)-humus complexes, allophane and/or imogolite, can also promote Hg accumulation. However in periods with important volcanic activity, new erupted inorganic material (sand, pumice, volcanic ash, etc.) could be deposited over the old soil given a new pedogenetic cycle. In these new conditions, the lower degree of soil evolution may explain the lower total Hg values observed in some of the studied soils. For all soil significant correlations (p<0.01) between total Hg content and several Al and Fe extractions were found (0.62 for Al extracted with CuCl2; 0.50 and 0.47 for Al and Fe extracted with Na-pyrophosphate; 0.42 and 0.34 for Al and Fe extracted using ammonium-oxalate, and 0.49 and 0.46 for Al and Fe extracted with NaOH and Na-dithionite respectively). Correlation coefficients showed a small increase when andic horizons (as defined by García-Rodeja et al, 2004) were considered separately. Stepwise regression analysis was performed to identify the most significant properties of andic horizons related to total Hg content. The model obtained, which includes reactive Al and Fe forms, explains 90% of the variance. The results of this statistical approach suggests that, in addition to soil organic matter, the presence of amorphous (organic and/or inorganic) Al and Fe components may be important for Hg accumulation in volcanic soils. References Lindqvist, O. 1991. Mercury in the Swedish environment. Water Air and Soil Pollut. 55:23-

32. Nriagu, J., and C. Becker. 2003. Volcanic emissions of mercury to the atmosphere: global and

regional inventories. The Sci. Tot. Environm. 304:3-12. Tomiyasu, T., M. Okada, R. Imura, and H. Sakamoto. 2003. Vertical variations in the

concentratoion of mercury in soils around Sakarajima Volcano, Southern Kyushu, Japan. The Sci. Tot. Environm. 304:221-230.

Coffey, M.T. 1996. Observations of the impactt of volcanic activity on stratospheric chemistry. J. Geophys. Res. 101:6767-6780.

Gustin, M.S., H. Biester, and C.S. Kim. 2002. Investigation of the light-enhanced emission of mercury from naturally enriched substrate. Atmos. Environm. 36:3241-3254.

García-Rodeja, E., J.C. Nóvoa, X. Pontevedra, A. Martínez-Cortizas, and P. Buurman. 2004. Catena 56:155-183.

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Distribution, bioavailability and behavior of persistent organic pollutants in Andosols: with specific reference to Iceland.

Graeme I. Paton1, C.J. Paterson1, Alan Winton1, Tinnakorn Tiensing1, Olafur Arnalds2

and Julian J.C. Dawson 1 1Soil Science Group, School of Biological Sciences, Cruickshank Building, University of Aberdeen

2Agricultural Research Institute, Reykjavík, Iceland Introduction Higher latitude soils are known to be the repositories for a wide range of persistent organic pollutants (POPs). Studies in Greenland, Alaska and Spitzbergen have all revealed elevated levels of POPs. In particular, highly chlorinated PCBs, dioxins, furans, OC pesticides and, in some studies, PAHs have been found. Iceland is quite different from the afore mentioned environments in that the milder climate and rich soils mean that terrestrial carbon sequestration into the biosphere and pedosphere is considerable. While Icelandic studies have considered the impact of POPs on fishing and the marine habitat, there has been no studies of the fate of these compound in the soil environment. Iceland, a country that has little association with these POPs, may be vulnerable to their deposition which could impact on soil functionality. Of even more concern is the risk that if bioavailable these POPs could be bioaccumulated and transferred through the food chain causing significant harm both to humans and the ecology of Iceland. Aims and objectives The aims of this study were to-

• Assess the concentration and distribution of POPs in Icelandic soils. • Consider the likely source of these pollutants. • Develop techniques to assess the relative binding behavior of POPs in Andosols.

Materials and Methods Sampling An intense sampling regime was developed in Iceland in September 2000. Samples were collected from thirty four locations representing a range of soil types, topography, vegetation and altitude. Inert sampling procedures were used to avoid cross contamination of the soils and vegetation and the samples were taken back to Aberdeen under controlled conditions. Analysis Three different groups of compounds were analysed. Full details of analytical procedures can be found in Strachan et al. (2002) and Dawson et al. (2004). In summary: For halogenated compounds, a hexane extract of soil was analysed after clean-up by GC-ECD. Other non-halogenated POPs were analysed by GC-FID using a similar extraction. ID was verified by GC-MS and suitable internal standards. PAH levels were measured by HPLC using a uv/vis detector or DAD at a predefined or scanning wavelength. Detected pollutants were compared with library data to verify source. Assessment of bioavailability Exhaustive extraction methods tell us little about the behaviour of POPs in the soils. To assess this component more readily, Andosols from Napoli and Iceland were amended with a range of concentrations of three PAHs- naphthalene, phenanthrene and pyrene. The PAHs

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were extracted using γHPCD (a cyclodextrin molecule) and XAD (a polymeric absorbent) (Puglisi et al., 2003; Semple et al., 2003). In addition to this the soils were also amended with a range of concentrations of dichlorophenol and pentachlorophenol (CPs). A range of semi-solvent extractions were used to elucidate the bioavailable fraction. Analysis was carried out for the PAHs and CPs using HPLC and bioluminescent-based biosensors (Tiensing et al. 2002). Results and discussion The levels of POPs in the areas studied were in most cases just above the detection limits. Elevated levels that were detected were a consequence of land-use and there was little evidence to suggest that the accumulation of POPs is as significant as proposed for the High Arctic. Andosols and Histosols are likely to actively sequester atmospherically derived POPs rendering them unavailable. Seasonal deposition may be of more concern and merits further focused investigation. Andosols caused considerable challenges in terms of analysis and the traditional techniques required a level of modification to best suit the trace detection required. Nevertheless, Andosol-specific techniques have been developed yielding highly satisfactory results. When Andsosols were amended with pollutant doses, as expected, they sequestered a significant proportion of the contaminants. For PAHs, the hydrophobic nature of the compounds rendered them sparingly soluble when extracted by non-exhaustive techniques. In the case of the CPs, they were also found to become tightly bound to the organic fractions within the Andosols. Comparative studies with Scottish soils suggest that Andosols have binding affinity values perhaps several orders of magnitude greater. Hence, even if POPs were being deposited in this environment, the sequestration efficiency of the soils may render their environmental impact to be significantly less than that associated with skeletal soils. Conclusions POPs are ubiquitous in the environment even though they have little recorded use in Iceland. Point source contaminants are probably a more significant environmental threat, but are easier to monitor. Snowfall and certain weather conditions may explain incidents of elevated diffuse contamination. Andosols are however resilient and are able to render these pollutants biologically unavailable. References Dawson, J.J.C., Maciel, H., Semple, K.T. and Paton, G.I. 2003. Analysis of organic pollutants

in environmental samples in Methods of Soil Analysis (ed. Cresser, M.S and Smith K.) Marcel Dekker, New York.

Puglisi E, Patterson CJ, Paton GI., 2003. Non-exhaustive extraction techniques (NEETs) for bioavailability assessment of organic hydrophobic compounds in soils. Agronomie 23, 755-756.

Semple KT, Morriss AWJ, Paton GI., 2003. Bioavailability of hydrophobic organic contaminants in soils: fundamental concepts and techniques for analysis. European Journal of Soil Science 54, 809-818.

Strachan, G., Capel,S., Maciel, H., Porter, A.J.R. and Paton, G.I.2002 Application of cellular and immuno biosensor techniques to assess herbicide toxicity in soils. European Journal of Soil Science 53, 37-44.

Tiensing T, Strachan N, Paton G.I. 2002. Evaluation of interactive toxicity of chlorophenols in water and soil using lux-marked biosensors. Journal of Environmental Monitoring 4, 482-289.

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Water properties of volcanic ash soils rich in high charge halloysite

Grégoire Pochet and Bruno Delvaux Unité Sciences du Sol, Department of Environmental Sciences and Land Use Planning, Université catholique de

Louvain (UCL), Belgium

Highly weathered soils rich in low charge 1:1 clay minerals and iron oxides usually exhibit high water infiltration rates. Their hydraulic conductivity at water saturation (Ksat) may range between 10 and 50 cm h-1. Since these clayey soils are also characterized by low available water, they behave like sands at moisture tension (MT) below 1500 kPa (pF 2.5), and like clays above this MT value. This well-known behaviour is caused by a strong micro-aggregation involving kaolinite and iron oxide.

In Tonga island (South Pacific, humid tropical climate), fine clayey soils (70-95% clay) derived from basaltic ash are widespread. They are rich in organic carbon (1-5% in the top 50 cm), which significantly accumulated in the clay fraction. Their clay fraction is largely dominated by halloysite and free iron (~ 9 %), with a large proportion of poorly crystallized Fe oxide. The cation exchange capacity of the clay fraction (CECclay) ranges between 15 and 90 cmolc kg-1 clay. In some clay fractions, swelling 2:1 silicates were detected by X-ray diffraction. The intensity of the XRD features of these 2:1 swelling clays was, however, not correlated to the magnitude of CECclay. The soils exhibited low bulk density (0.9-1.2 g.cm-3), and high hydraulic conductivity (Ksat) at water saturation in all horizons (10-90 cm h-1). Their porosity and water properties, as measured through the water retention curve, showed low available water despite a very high moisture content at wilting point (>30%). These hydric and hydrodynamic properties suggest a strong micro-aggregation.

Micro-aggregation in halloysitic soils is poorly documented and may seems paradoxical because of the CEC of the clay fraction which is typical for high activity clays (HAC), rather than for low activity clays.

Our results suggest that the combination of a large proportion of poorly crystallized iron oxide and the accumulation of humic substances in the clay fraction may provide a strong basis for micro-aggregation in HAC soils. This hypothesis underlines current research

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Solute transfert in an andisol of the French West Indies after application of KNO3 : from the agreggate to the field experiment

Sansoulet J.1, Cabidoche Y.M.1, Cattan P.2, Clermont Dauphin C.1, Desfontaines L.1,

Malaval C.3 1. INRA, Institut National de Recherche Agronomique, Unité AgroPédoClimatique

2. CIRAD, Centre de coopération Internationale en Recherche Agronomique pour le Développement, Département productions Fruitières et Horticoles

3. CNEARC, Centre National d’Etudes Agronomiques des Régions Chaudes Since 30 years, fertilizer supply on banana cropped on andosol in the French West Indies, takes into account a high leaching of potassium and nitrates, that had been measured on oxisol and some andosol by Godefroy et al (1975) and Godefroy and Dormoy (1988). The nitrogen and potassium supply can reach respectively more than 400 kg N ha-1 year-1 and 800 kg K ha-1 year-1. Both fertilizers are supplied around the bottom of the banana pseudo-stems. On one hand, the banana canopy by-passes the incident rainwater into a main streamflow around the pseudo-stem (stemflow) and a lower dripping flow under leave borders. On the other hand, andosol allophanes exhibit pH dependent electric charges. The diversity of cropping systems, including liming, induces a diversity of physico-chemical status. Ranges of observed pH are frequently under the Zero Point of Charge (ZPC) and these andosol could then develop Anion Exchange Capacity (AEC) in deep layers which are likely to retain anions as NO3

-. With such characteristics, understanding distributed water flows and consecutive solute leachings under banana cropping on andosol can help to improve fertilizer supply by minimising solute losses. We performed 3 types of experimentations : (i) The AEC and the capacity of the andisol to retain NO3

- and K+ have been measured using the batch method of Wada and Okamura (1980) under different pH conditions. (ii) Undisturbed soil columns of 1.5 dm3 allowed to study the anion and cation elutions. An initial amount of solid KNO3 or LiBr has been spread on the top face of the columns, which has been immediately dissolved during the first V/V0 elution. Discrete elutions were applied every two days, until 8 V/V0. (iii) Wick lysimeters, set up at 0.75 m depth, allowed to estimate in situ drainage distribution and the associated solute leachings, through both high infiltrability layers A (Ksat > 150 mm h-1) and B (Ksat = 30 +/- 7 mm h-1). The type and length of the wicks have been chosen in order to collect the same average flow in lysimeters than the flow in undisturbed wet soil ; the HYDRUS 2D model allowed to verify that lysimeters minimized bias. Five replicates of four positions in respect to the stem positions were set up. The banana cropping received homegeneous KNO3 supplies – 70 kgN(NO3) ha-1, 200 kgK ha-1 – each 3 months. The breakthrough curves of the B layer for pointed out that 2 phases occured during elutions: the first one resulted from quick solute elution and the second one from the slow lixiviation of a sorbed fraction of the NO3

- input. K+ showed a similar behaviour. For Li+, only the first phase occured, without evidence for sorption (fig.1.). The A layer showed usual behaviour of K+ and Li+ which was characterized by immediate sorption. Nevertheless NO3

- exhibited the same two phase behaviour than in the B layer. In both layers, the final sorbed Br-/Li+ ratio strongly increased while pH decreasing, according to AEC increasing. The batch experiment confirmed those trends.

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Fig. 1 Elutions of Li/Br through an undisturbed column of andosol (layers A and B)

The lysimeter outflow clearly showed the impact of the stemflow on over-supplied drainage bellow the pseudo-stems (a) and on their downstream neighbourings (b), and the umbrella effect of leave covers (c). Under a banana cover which LAI was 4, the resulting apparent drainage / incident rainfall volume ratio were respectively 1.2, 1.6, and 0.3, while the bare soil (d) exhibited a ratio of 0.5. The associated solute leachings were consistent with a high sorptivity of NO3

- and a low sorptivity of K+ (fig. 2) : for NO3-, immediate moderate

leaching during the three first rainfall events after supply was followed by a low leaching ; finally, the total leaching reached 30 % of the input. For K+, a strong leaching occured until 200 mm of drainage, followed by a desorption phase whose slope was moderate. The total leaching of K+ reached 80% of the input.

Fig. 2 Water and solute leaching under banana tree after application of KNO3. Five replicates of four positions in respect to the stem positions were set up(a, b, c, d).

Finaly, localised over-supplied drainage downstream to the banana stemflow result in high losses of K+, whose supply have to be sustained, avoiding the bottom of banana. On the contrary, despite this strong local drainage, nitrate sorption allows only small losses. Further research have to integrate distributed flows and coupling solute transports, taking into account variable charges status. References Godefroy J., Roose E. J., Muller M. 1975. Estimation of fertilizer losses by run-off and drainage in a banana soil

in the south of the Ivory Coast. Fruits. 30(4):223-235. Godefroy J., Dormoy M. 1988. Mineral fertilizer element dynamics in the “soil-banana-climate” complex.

Application to the programming of fertilization. III. The case of andosols. 43(5):263-267. Wada K., Okamura Y. 1980. Electric charge characteristics of Ando A, and buried A horizon soils. J. Soil Sci.

31:307-314.

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Aluminum solubility in nonallophanic Andosols from northeastern Japan

T. Takahashi and M. Nanzyo Graduate School of Agricultural Science, Tohoku University, Japan

Introduction Andosols are divided into two major groups on the basis of their colloidal compositions: “allophanic” Andosols dominated by allophanic clay materials and “nonallophanic” Andosols dominated by aluminum (Al) - humus complexes and 2:1 type aluminosilicates. Both groups of Andosols show unique properties characteristic of volcanic ash derived soils, such as high reactivity with phosphate and fluoride ions and a low bulk density. However, there are large differences in soil acidity and Al toxicity between the two groups of Andosols. Allophanic Andosols are moderate to slightly acid even when the base saturation is very low and rarely contain toxic levels of KCl-extractable Al. In contrast, nonallophanic Andosols are strongly acid when the base saturation is low and possess a high KCl-extractable Al that shows toxicity to plant roots. The origin and status of the toxic Al are not yet clear. In this study, we analyzed Al solubility of A horizons of nonallophanic Andosols from northeastern Japan. Then, we investigated the relationship between 1 M KCl-extractable Al and organically complexed Al that is a major Al pool in nonallophanic Andosols. Finally, we examined the effects of liming (CaCO3 treatment) on Al-humus complexes. Materials and methods A horizon samples of nonallophanic Andosols were collected from northeastern Japan. Sampling points were distributed in Aomori, Akita, Iwate and Miyagi Prefectures. As comparisons, we used some allophanic Andosols and a Bhs horizon of a Spodosol.

An equilibrium study was conducted to determine the solubility of Al as a function of pH. A 0.01 M CaCl2 solution was added to soil samples and HCl or NaOH was added to provide a pH range from 3 to 5. After 30 d incubation at 25oC, monomeric Al concentrations were determined and Al3+ activity was estimated.

Extractable Al (1 M KCl and sodium pyrophosphate (Alp)) was determined to characterize soil aluminum pools. The relationship between Al saturation (KCl-extractable Al / effective CEC) and Alp was examined.

Based on the lime requirement with respect to a pH of 6.5, the mixture of soil samples and CaCO3 was incubated at field water capacity for 30 d. After air drying, the limed and unlimed samples were used for determination of 1 M KCl-extractable Al, Alp, and so on. Results and discussion It is generally assumed that Al solubility of mineral soils is regulated by a solid Al(OH)3 mineral phase (e.g. gibbsite). However, aqueous Al concentrations in humus-rich soil horizons are considered to be regulated also by humic substances. Figure 1 shows pH – pAl relations obtained by the equilibrium study. Al solubility of the allophanic Andosol was nearly identical with that of synthetic gibbsite. The saturation index (SI) of imogolite for the soil calculated from H+, Al3+ and H4SiO4 activities showed +0.4 to +1.0, indicating slight oversaturation with respect to imogolite. Thus, the allophanic Andosol horizon appears to be in near equilibrium with both Al(OH)3 and imogolite. On the other hand, Al solubility of the nonallophanic Andosol A horizon and the Spodosol Bhs horizon was lower than gibbsite in the lower pH range and show oversaturation in the higher pH range. These results strongly suggest that the Al concentration is controlled by ion exchange reaction of H+ and Al3+ ions on negative charges of humus and that Al solubility is regulated by Al-humus complexes.

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Thus, it is considered that organically complexed Al controls Al concentration in soil solution of nonallophanic Andosols. Exchangeable Al estimated by 1 M KCl extraction is thought to be easily released into soil solution. Therefore, exchangeable Al should be related to organically complexed Al. To confirm this hypothesis, we investigated the relationship between Al saturation (exchangeable Al / effective CEC) and Alp contents of nonallophanic Andosol A horizons from Noshiro City, Akita Prefecture. A significant, positive correlation was observed between Al saturation and Alp content (r = 0.714, p < 0.001) (Fig. 2). In these soil horizons, aqueous Al is considered to be equilibrated as follows: humus complexed Al ⇔ aqueous Al ⇔ exchangeable Al.

The above results indicate that a portion of Al-humus complexes are labile and are easily altered by rather simple chemical treatment such as liming. Figure 3 shows the pyrophosphate extractable Al (Alp) of limed and unlimed soil samples. A large decrease of Alp value with liming was observed (decrease rate of 9 – 43%). The decrease of Alp values cannot be explained only by the disappearance of the KCl extractable Al. It is strongly indicated that liming reduces significant amounts of organically complexed Al as well as exchangeable Al. The increase in the cation exchange capacity at pH 7 after liming further suggested that the carboxyl group was partly liberated from Al complexation.

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The solubility of synthetic gibbsite is indicated by the dotted line.

y = 57.696Ln(x) + 70.916

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Noshiro soils from Akita Prefecture.

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Proton/Al3+ exchange reaction as a precursor of the hydrolysis of volcanic glasses

D. Wolff-Boenisch1, S. R. Gíslason1 and E. H. Oelkers2

1Science Institute, University of Iceland, Reykjavik, Iceland 2 Géochimie: Transferts et Mécanismes, CNRS/URM 5563--Université Paul Sabatier, 31400 Toulouse, France

Oelkers and Gislason (2001) and Gislason and Oelkers (2003) have proposed a mechanism and rate equation for basaltic glass dissolution. This equation has two straightforward implications:

1) The logarithm of the forward dissolution rate (r+) is proportional to the logarithm of the quotient (a3

H+/aAl

3+). This relationship has been validated now not only for basaltic but also for more acid volcanic glasses up to rhyolites. It follows that, under acid conditions, natural glasses obey the same dissolution mechanism regardless of their chemical composition. Caution must be applied as experimental results from a previous study (Wolff-Boenisch et al., 2004a) indicate that glass dissolution rates are only proportional to geometric than BET derived surface areas.

2) A reduction in the activity of Al3+ at fixed pH will inevitably lead to an increase in r+. This assumption has been tested by mixed flow reactor experiments with volcanic glasses where far from equilibrium steady state dissolution rates were measured at 25° C and pH = 4 as a function of aqueous fluoride concentration. The additional fluoride is expected to lower the aqueous Al3+ activity due to aqueous Al-F complex formation. Indeed, natural glass dissolution rates increase dramatically with increasing aqueous fluoride concentration by more than one order of magnitude in response to a rise in aqueous fluoride concentration from 0 to 3.8 ppm.

The observed enhancement of volcanic glass dissolution rates with aqueous fluoride concentration has numerous implications for major and trace element mobility in volcanic terrains. For example, aqueous fluoride concentration of melted snow in contact with pristine volcanic ash can vary from less than one ppm to more than 1200 ppm. Glass dissolution rates in these natural systems may be far faster than previously estimated (Wolff-Boenisch et al. 2004b). References Gislason S.R. and Oelkers E.H. (2003) The mechanism, rates, and consequences of basaltic

glass dissolution: II. An experimental study of the dissolution rates of basaltic glass as a function of pH at temperatures from 6°C to 150°C. Geochim. Cosmochim. Acta 67, 3817-3832.

Oelkers E.H. and Gislason S.R. (2001) The mechanism, rates, and consequences of basaltic glass dissolution: I. An experimental study of the dissolution rates of basaltic glass as a function of aqueous Al, Si, and oxalic acid concentration at 25° C and pH = 3 and 11. Geochim. Cosmochim. Acta 65, 3671-3681.

Wolff-Boenisch D., Gislason S.R., Oelkers E.H., and Putnis C.V. (2004a) The dissolution rates of natural glasses as a function of their composition at pH 4 and 10.6, and temperatures from 25 to 74°C. Geochim. Cosmochim. Acta, in press.

Wolff-Boenisch D., Gislason S.R., and Oelkers E.H. (2004b) The effect of fluoride on the geometric surface area normalized dissolution rates of natural volcanic glasses at pH 4 and 25°C. Geochim. Cosmochim. Acta, in press.

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Response of physical properties of Andisols and andic soils from Tenerife to saline and sodic treatments

S. Armas-Espinel1, C.M. Regalado2 and J.M. Hernández-Moreno1

1 Dept. Edafología-Geología, Universidad de La Laguna (ULL) 2 Dept. Suelos y Riegos, Instituto Canario Investigaciones Agrarias (ICIA).

Although the stabilising effect of variable-charge minerals on soil structure is well known, calibration studies using accepted methodologies are scarce, especially in the case of andic materials coexisting with layer silicates. In previous field work on soils from Tenerife, the authors found that under certain combinations of exchangeable cations distribution, salinity, and clay mineralogy, the aggregating effect of the non-crystalline materials could not counterbalance soil structure deterioration for certain threshold values of the andic parameters (Armas-Espinel et al., 2003). Therefore, further investigation is needed to calibrate the combined effect of electrolyte concentration and exchangeable Na (Mg) on soil structural stability in soils with a range of andic properties. To this end, an experiment was set up to study the influence of sodicity and electrolyte level (C) on soil saturated hydraulic conductivity (Ks), moisture retention and shrinkage behaviour.

Soil samples (2 mm-sieved) were packed at field bulk density in 100 cm3 columns (5 cm i.d.) and percolated through with the highest concentrated solutions with different SAR values until equilibrium was reached (three replicates each). Next, Ks was determined at decreasing electrolyte concentrations for each SAR value in a constant head laboratory permeameter, until reductions in permeability and dispersed clay in the percolate were observed. Finally, of the three replicates, first one was used for water retention measurement, second for soil shrinkage determination (remoulded samples), and third for soil analysis.

This work presents the first results obtained for selected high SAR values with natural and cultivated soils from Tenerife with a range of andic properties. For the selected soils, the parameter (Alo + 1/2Feo) decreased in the order: 6 % (soil AV, Andisol), 3 % (soil X), 2.1 % (soil F) and 2 % (soil B). To describe the results, we shall use the following definitions:

Threshold concentration CTH (meq/L) = 0.56· SAR+0.6 (Eq. 1). Concentration causing a 15% decrease of permeability (Quirk, 1971).

Turbidity concentration CTU (meq/L) = 0.16·SAR+0.2 (Eq. 2). Concentration when the percolating solution is reduced to about one-quarter of the CTH and dispersed clay appeared in the percolate (Quirk, 1984).

The relative change in hydraulic conductivity is defined as the ratio of Ks for a given solution to the respective Ks calculated for the initial solution.

At the SAR value studied no influence of C was observed in the structural stability of the Andisol. In the case of the andic soils, the Ks values were unaffected until concentrations of about 0.02-0.0013 mol/L (soil F), 0.01-0.015 mol/L (soil B) and 0.01 mol/L (soil X), in which a 15% Ks reduction occurred (Fig. 1). Therefore, these concentrations represent the CTH values. In the case of soil F this value agreed with that predicted by Eq. 1, while soils B and F were more stable than predicted. Clay dispersion (CTU) appeared from 0.005M for the less andic soils (B and F) and no turbidity was observed for the more andic soil (X) up to the more diluted solution studied (0.001M). These values were in agreement with Eq. 2 for soils B and F.

In conclusion, at SAR 25, the main mechanism of Ks reduction up to 0.005 mol/L seems to be swelling by layer silicates, since structural stability in allophanic material is little affected by the nature of exchangeable cation (Warkentin and Maeda, 1980). In spite of the sharp reduction of the relative Ks, it still presented high (soils F and X) to moderate values (soil B).

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These results agree with the field behaviour of these soils. Further research may contribute to establish critical concentration values related to andic properties.

Fig. 1 Relative change in hydraulic conductivity values as a function of the percolating solution concentration (C) at SAR 25, for the studied andic soils. References Armas-Espinel S., J.M. Hernandez-Moreno, C. Muñoz-Carpena, C.M. Regalado. 2003.

Physical properties of “sorriba” cultivated volcanic soils from Tenerife in relation to andic diagnostic parameters. Geoderma 117: 297-311.

Quirk, J.P. 1971. Chemistry of saline soils and their physical properties. p.79-91. In T Talsma, JR Philip (ed.) Salinity and water use. McMillan Press: London.

Quirk, J.P. 1984. Soil permeability in relation to sodicity and salinity. Philosophical Transactions of the Royal Soc. (London) A316: 297-317.

Warkentin, B.P., Maeda, T., 1980. Physical and mechanical characteristics of Andisols. p. 303-323. In B. K. G. Theng (ed.) Soils with variable charge. New Zealand Society of Soil Science.

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Solute and water fluxes in andisol fertilized with pig manure: soil columns experimentation

Frédéric Feder1 and Antoine Findeling2

1 CIRAD – RELIERA team – station de La Bretagne, F-97 408 Saint Denis messag. CEDEX 9 – France 2 CIRAD – RELIERA team, TA 40/01 – F-34 398 Montpellier CEDEX 5 – France

Introduction Waste production is dramatically increasing in Réunion island and valorisation becomes an important scientific, technologic and economic challenge for the future. Among different recycling techniques, spreading is suitable for many wastes (especially for organic wastes) and permits to enhance soil fertility and to use soil purification power. In contrast, with the rich literature found for temperate conditions, few studies tackle risk estimation and management of waste spreading under tropical conditions with specific climatic and agro-pedologic features. This work aims at studying the physical and chemical transformations and the solutes transfer related to pig manure spreading on a volcanic andisol of Réunion island. Materials and methods The experimental layout was based on three columns of disturbed soil (C1, C2 and C3) of one meter height and forty centimetres diameter (figure 1). Spreading was carried out on C1 and C2 whereas C3 was used as the reference. Columns were kept at 25°C and supplied with calibrated amounts of water corresponding to measured rainfall. Each soil layer (0-20, 20-40 and 40-100 cm) was equipped with a TDR probe to follow water regime and a pH electrode and redox electrode to monitorate chemical properties. A limnigraph stored the water flow at the outler of the columns. All these sensors were connected to a datalogger operating at a ten minutes time step. Micro-samplers were inserted at the same levels and at 7.5 cm to analyze the changes in soil solution chemical composition. Results and discussion The chemical composition of the pig manure used in this study is reported in table 1. By comparing the two replications (C1 and C2) with reference column (C3), we observed several agronomical consequences of pig manure spreading: 1/ Nitrification of the pig manure (i. e. the conversion in the soil of ammonium into nitrate with the release of H+ ions: NH4

+ + 2 O2 � NO3- + 2 H+ + H2O). In the soil solution, at

7.5 cm depth, nitrate production was correlated with ammonium disparition. After one month and 500 mm of cumulated water amounts, nitrification was over and corresponding nitrate was leached. At 15 cm depth, we never observed ammonium from the pig manure and leaching of the nitrate, all coming from nitrification in the upper part of the soil, was completed after 750 mm of cumulated water amounts. Acidification of the soil solution was measured at 7.5 and 15 cm depth. At 15 cm depth, the acidification could not result from nitrification because no ammonium was observed at this depth. However, it may come from the leaching of H+ ions from above. 2/ Vertical transfer of major chemical elements. We observed similar results for calcium, magnesium, sodium and nitrate: the maximum concentration of elution peak was measured after 600 mm of cumulated water amounts at 35 cm depth, and after 1200 mm of cumulated water amounts at the column outlet. 3/ Saturation of soil exchange complex by potassium. Conversely, potassium concentration in soil solution did not reveal the high concentration of the pig manure. A large part of potassium ions probably participated to the saturation of soil exchange complex.

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4/ Two kinds of pollution by trace metal elements. Copper and zinc are two metals frequently observed with high concentrations in pig manure (due to the veterinary treatments). Each one had a specific behaviour in the soil. Copper was accumulated in topsoil layer and created a local pollution source whereas a deep transfer of zinc induced a risk of groundwater pollution. Conclusions The first objective of this study was to create an experimental device in order to evaluate the pollution risk related to agronomical valorization of organic wastes in Réunion andisol under tropical climatic conditions. We used representative conditions (waste, soil, water supply) and followed water fluxes and chemical composition of soil solution at different depths. Results permitted to quantify pollution transfer (especially nitrate and metal elements) through the soil without the perturbation of plant uptake. For the farmer, these results emphasized kinetics and depth influence of pig manure nitrogen impact (nitrification and transfer). The plant will be accounted for in a following step. Table 1 Chemical composition (milimoles/l) of the pig manure used in the soil columns C1 and C2.

Ca

mM/l Mg

mM/l K

mM/l Na

mM/l Al

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mM/l P

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mM/l Cl

mM/l NO3

- mM/l

NH4+

mM/l 1.23 0.92 50.1 15.7 0.01 0.001 4.66 1.58 0.004 0.007 1.87 39.49 0 100.59

Figure 1 Soil columns experimentation.

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Land use changes of traditional vine-growing areas in volcanic regions of Hungary.

O. Fehér1, B. Madarász2, Á. Kertész2 and G. Füleky1

1Szent István University, Department of Soil Science and Agrochemistry, Gödöll�, Hungary; 2Department for Physical Geography, Geographical Research Institute, Hungarian Academy of Sciences

The Neogene to Pleistocene volcanism of the Carpathian-Basin can be divided into two types:

1) Calc-alkaline, and within this, silicic and intermediate volcanism: includes the territories of Northern Hungary.Silicic volcanic activity can be characterised by high proportion of rhyolitic and dacitic rocks. The main products of this activity are ignimbrites (pumiceous pyroclastic flow deposits), pyroclastic fall deposits and reworked material.The products of intermediate volcanism are predominantly andesites, dacites, basalt andesites.

2)Alkali basalt volcanism: occured predominantly in the western part of Hungary in the Pannonian Basin. Tuff rings, maars and shield volcanoes were formed about 3-7 million years ago. Neogene basaltic volcanic rocks occur also at the northern and eastern rim of the Pannonian Basin close to the 16 to 1 million years old calc-alkaline volcanic complexes (PANNON ENCYCLOPAEDIA, 1999).

During our field surveys (years 2000-2002) we tried to look to main characteristics of soils in these regions and also tried to answer: why the soil mantle of these vine-growing areas is so special? Why production of wine is so successful since the Middle Ages? Was it really only due to special microclimate, fortunate choice of variety of vine-plant and wine treatment?

Or is it something related with the special harmony of the vine with the soil/ substratum below? In different handbooks for vineyard establishment one would find that one of the conditions of successful vine–growing is to have a soil at least 100 cm deep. According to effective soil depth we could differentiate two types:

• Shallow (less than 60-70cm). These soils are developed in situ from the underlying parent rock. Clear examples we could find only in the areas of silicic volcanism (Andornaktálya, Erd�bénye, Avastet�).

• Deep soils (� 70 cm depending on the slope position and degree of erosion): these viticultural soils are mainly formed on loose slope deposits with significant input of fallen dust and addition of the volcanic debris of the area (Somló, Badacsony, Tihany, Kopaszhegy).

But the effective rooting depth in all cases was more than 150 cm and the other striking feature was the interaction of vine-roots with the mineral part:

• in most cases it was more dense around the volcanic debris in case of deep soils • and in the shallow soils the rooting system became relatively denser in the parent rock.

This interaction of roots with volcanic material would determine the so called “mineral taste”, which brought the fame of wine produced in these regions. To understand better the economical and social background of land-use changes our further analysis were based on the interpretation of maps and written historical records. From data integration we found several similarities in trends of development and decline:

All of these territories as mentioned earlier are having relevant vine-producing areas with history since Middle Ages. In case of the Pannonian territories-wine producing dates back to the Romans. Certain declines of these territories were related with wars, loosing foreign markets, damage from frost or drought from what were able to renew. Except one, this was the vine-pest (phylloxera) at the end of the 19th century which transformed dramatically not only the slopes, but also tradition and culture of production of high quality wine. Between the

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two World Wars territories still reduced- as wine producers were hit by the economic crisis and by breaking up of the Austro-Hungarian Monarchy. Also in the early 1960’s organization of collective farms developed large-scale vine-growing, so it extension of vineyards moved bit down to the direction of foothills due to high rate of mechanisation.

On the basis of data gained from the written records we made an attempt to connect the described land-use changes with the available cartographic material. For this purpose we have been using military maps as sources: 1st-2nd-3rd military surveys of the Hapsburg Empire from 1764-1785, 1819-1866, 1869-1880 respectively (scales 1:28800 and for the last one 1:25 000); the 1:25 000 scale military maps from the 1950’s and the last and freshest updated from the 1990’s made by the Honvéd (Hungarian soldier) Mapping Institute. For the identification of land-use changes since the 1990’s we were using the CORINE Land Cover database from the 1998-99 survey of scale 1:50 000.

To our surprise the cartographic data for the chosen sights did not reflect the dramatic damage caused by the vine-pest. There are two possibilities why we did not find it on the maps: firstly, the chosen areas are the most valuable ones, this is why an enormous effort were taken to protect them from the pest and also to renew it among the first ones. Secondly, the interval of mapping was too big to record the changes and also, since these are military maps-it was out of interest to map the vineyards as for example old/ dead or new plantations.

There is an interesting correlation in between the woodland and viticultural areas: with the relative expansion of vineyards during the early 19th century there is a visible decrease in woodland territories in the upper part of the vine-hill, and in fact in our field surveys, especially in Badacsony,-in the profiles of present-day forest we have found traces of human activity (pottery dating back to the 15th century). From the written records we also know that cultivation of those slopes became steady with establishing of vine-hills (Promontorium) with special taxation privileges in the 14th century (LICHTNECKERT, 1990, FEHÉR, 1999). The golden-age of the vine–hills can be dated back to 17th-19th century and this is clearly visible from the 1st and 2nd military surveys, when we get the highest percentages of vineyards.

The picture on the maps stays almost similar until the 1960s, when there is a tendency of woodland expansion, which is related with the afforestation program on steep slopes. This is causing a relative decrease in vineyards on steep-slopes (special case in Kopaszhegy).Sometimes instead of forest fruit tree- plantations are established on the former vine-growing areas (Andornaktálya, Erd�bénye).

On the foothill areas, there is a striking correlation between the meadow/pasture-lands and plough-lands. In the Pannonian-basin, especially in the Tapolca basin as often mentioned in the documents of the 18th century marshy areas were drained and used as meadows. Later in the middle of the end of the 19th century in close relationship with the emancipation of serfs there is a visible increase of plough-lands on the territories of former meadows.

The approach to follow changes in wine-production allows present-day land-use to be identified as a result of long-term development- as the process of adoption to soil features (determined by the volcanic parent material and unique microclimate of studied territories) and an extended understanding of present landscape as a result of adoption and work of past societies. References Encyclopaedia, P. 1999. The land that is Hungary. CD-ROM: ARCANUM Adatbázis Ltd. András, L. 1990. The history of Balatonfüred-Csopak wine-region. (in Hungarian) Veszprém Fehér, O., G. Füleky. 1999. Landscape of the Balaton Lake in the 19th century. In: Branis, M.

eds.: Acta Universitas Carolinae Environmentalica Vol.13 .Nos 1-2 pp. 51-57.

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Influence of land use changes in the soil temperature regime of Andisols

C. Jiménez, M. Tejedor and M. Rodríguez University La Laguna, Tenerife, Canary Islands

Soil temperature is a parameter that influences various processes occurring in soils. Some of these processes are related to the formation of the soil, while others have to do with biological activity and crop development. The fact that some soil classification systems, particularly those in which greater importance is attached to soil use, the choice of this parameter, in the form of soil temperature regime, as a taxonomy criterion illustrates its importance. One such case is the Soil Taxonomy (Soil Survey Staff, 1999), which takes temperature into account at virtually all levels of hierarchy, either directly or indirectly through, for example, soil moisture regimes. In this system, regimes are defined on the basis of the mean annual temperature of the soil at 50 cm. The present paper examines how changes in land use can affect the soil temperature regime. In the case studied, vegetation was modified on three Andisols on the island of Tenerife (Canary Islands, Spain). The island, which is located near the Tropic of Cancer and has a maximum height of 3,718 m.a.s.l., has a wide range of microclimates depending on factors such as altitude, orientation, the influence of the trade winds, etc. The following altitudinal sequence has been described provisionally for the north side of the island (Tejedor et al., 2003): hyperthermic (0-80 m.a.s.l.), isothermic/thermic (800 m.a.s.l.), isomesic (800-1400 m.a.s.l.), mesic (1400-3200 m.a.s.l.), frigid (> 3.200 m.a.s.l.). The altitudinal strip between 800-1400 m.a.s.l. is influenced by the trade winds, which discharge their moisture and thus add to the amount of water obtained through rainfall (which is approximately 650 mm/year). This extra water can be quite substantial, according to some authors. The corresponding surface soils, formed on volcanic materials, are Andisols of different types. Three sites were chosen in a zone where the original vegetation was modified such that in each there were plots with natural plant cover and others where the cover had been altered. In each plot, temperature was measured monthly over a period of three years (2001-2003) at 50 cm, using thermistors. Between four and six measurements were taken each time. The site 1 soils, located at 870 m.a.s.l., are Ultic Fulvudands, non-allophanic andisols with an abundance of organic matter (10%) which is well incorporated in the profile, where halloysites were dominant. The natural vegetation entirely covering the soil is cloud forest - “Laurisilva” -, the main species being Laurus azorica, Erica arborea, Erica scoparia and Myrica faya, which reach varying heights between 1-8 metres. One zone was cleared and replanted in the 1970s with Pinus radiata, which have grown to around 15-20 metres. The soils of site 2, also at 870 m.a.s.l. but at the opposite end of the same face of the island, are Hapludands. These too are rich in organic matter (7 %) and have a predominance of allophane in the fine fraction. The original vegetation was gradually modified to allow cropping. Coexisting here are plots of natural tree-heath woodland: Erica arborea, with Chamaecytisus proliferus, Cystus symphytifolius, with a covering of 60-80% all years and reaching 3-4 m height; plots with herbaceous plants: Pteridium aquilinum, Cystus symphytifolius, Rumex maderensis, Rubus ulmifolius, with a covering of over 80% in summer and less than 20% in winter, reaching 0.8-1m in height; and cultivated plots (no irrigation): Solanum tuberosum. In site 3, located at 1370 m.a.s.l., the natural soils are Hapludands, again with abundant organic matter and short-range-order products. The natural vegetation is Pinus canariensis with little undergrowth. During the 1960s, in one of the plots the pine trees were replaced by eucalyptus trees. However, these were cut down at approximately the same time as our study commenced and, during the course of the study, herbaceous plants, especially ferns, have grown there.

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Table 1 gives the mean annual soil temperature, the mean summer and winter temperatures and the isotivity (difference between summer and winter temperature) for each plot. Although all the soils under natural vegetation are located within the same climate strip, the higher altitude of site 3 is reflected in the lower (2ºC) mean annual soil temperature. Despite this, in all three cases the soil temperature regime is isomesic, although the isotivity being much more pronounced in the site 1. Modification of the plant cover has led to a notable change in the soil temperature regime of sites 2 and 3, which became thermic under the ferns and in the cultivated area of site 2, and mesic in the deforested area of site 3. In both sites the change of use has led to an increase of over 2 ºC in the mean annual soil temperature and also to a greater seasonal contrast (increase of 2.2 ºC). Conversely, in site 1 the different temperatures and the soil temperature regime remain constant despite the change in vegetation.

Table 1 Seasonal and annual soil temperature (º C) for the study plots

We attribute these results to the influence exerted by the different types of vegetation in creating a special microclimate, which is formed as a result of the action of the trade winds. The ‘laurisilva’ and pine forests and, to a lesser extent, the woodland have a high capacity to draw the moisture from the winds. This occurs throughout the year, particularly in summer, and leads to very homogenous environmental conditions, which determine the isomesic regime and the isotivity of these natural zones. The crops and the herbaceous plants that emerged after the trees were cleared do not have the aforementioned capacity and hence the temperatures are higher and the contrasts greater. The differences between the natural plots on the three sites may also be due to their location. The modifications to the soil temperature regime brought about by the change in land use will also have repercussions, in some cases, on the characterisation of the soil moisture regimes and, consequently, on the classification of the soils. References Soil Survey Staff. 1999. Soil Taxonomy. Second ed. Nat. Resour. Conserv. Serv., USDA

Agric. Handb. 436, Washington, DC. Tejedor, M., Jiménez, C., Rodríguez-Paz, M., and Hernández-Moreno, J.M. 2003. Soil

temperatura regimes in the island of Tenerife. Altitudinal sequence. ASA-CSSA-SSSA Annual Meetings. Changing Sciences for a Changing World Building a Broader Vision. Denver.

Site Site 1 Site 2 Site 3 Land use Cloud

forest Pine

forest Woodland

(heath) Herbaceous Crop Pine

forest Deforested

Mean annual 14.1 14.5 14.4 15.5 16.8 11.6 13.7 Mean summer 15.3 15.6 17.3 18.5 20.8 14.2 17.6 Mean winter 13.0 13.4 12.0 12.8 13.3 9.4 10.6

Isotivity 2.3 2.2 5.3 5.7 7.5 4.8 7.0

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Soils developed on volcanic material and their erodibility in Hungary

B. Madarász, Á. Kertész Department for Physical Geography, Geographical Research Institute, Hungarian Academy of Sciences

Volcanic activity took place in two main phases in the Carpathian Basin. The older phase occured in the Middle Miocene approximately 20 to 10 million years ago. This phase can be characterised by calc-alcaline silicic pumice and ash flow deposits (ignimbrites), and andesite-dacite lavas. The Pliocene-Pleistocene phase produced alcaline basalt lavas and tuff. This phase began some 7 million years ago and finished only about 500 thousand years ago. The absence of typical Andosols in Hungary can be explained by the relatively old volcanic material in the region. In the framework of the COST 622 action in Hungary three soil profiles were selected for detailed analyses. These profiles represent different types of volcanic bedrock because of the large variety of soils developed on volcanic rocks. Brown earth (Cambisol) can be found in the lower areas, mostly on pumice-and-ash flow deposits. Forests soils are present in the mountainous region, where the parent material of the soil is mainly lava or block-and-ash flow deposit. The most common forest soil is the lessivated brown forest soil (Luvisol). The soil type closest to the Andosols in Hungary developed either in hilltop or in pediment position. The hungarian soil-classification system calls this soil erubáz. People call it black wet soil, which refers to its dark colour and high clay (mostly smectite) content. The erubáz soils are caracterised with an intense humification, almost neutral pH values, friable or polygone structure and they are weakly leached. Their water retention capacity is very low and their heat-regime is extreme. In springtime their water content is high, which decreases rapidly in the first part of the summer. Majority of the Hungarian wine-regions are situated in volcanic areas with erubáz or erubáz-like soils, therefore the cultural and economic significance of this soil is considerable. According to the COST 622 analyses, these soils proved to be similar humic Umbrisols. On hillsopes and pediment surfaces these soils can be significant by erodid. The erodibility, or K-factor is determined according to the USLE method (WISCHMEIER and SMITH 1978) by Copecki rings. The results of these measurements are expected for May 2004.

References Wischmeier, W.H., and D.D. Smith. 1978. Predicting rainfall erosion losses. A guide to

conservation planning. USDA Agriculture Handbook. No. 537. Washington Stefanovits, P. 1992. Soil Sience (in Hungarian, Talajtan), Mez�gazda Kiadó

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Soil P status and eutrophication on volcanic watershads of the Azores

J. Madruga, J. Pinheiro, and L. Matos

Departamento de Ciencas Agrarias, Universdade dos Açores Angra do Heroismo, Azores, Portugal Soil P status of Furnas watershed of S. Miguel island (the Azores) was studied, based on P Olsen and P saturation index (PSI) referred as the saturation degree of the sorption-precipitation capacity of a soil to P, estimated from an acid-ammonium oxalate (pH 3) extraction of Fe, Al and P associated with non-crystalline Fe and Al constituents. Both methods were used in Typic Udivitrands under an intensive pasture management, which as involved a P overfertilization process and consequent eutrophication of the adjacent lake.

Soil test P Olsen was in general above the agronomic sufficiency, and in some cases above 150 mg kg-1, 5 times above the considered agronomic requirements as referred to the Olsen method.

ISP was also very high in some areas of the watershed, above the threshold value of 25%, mentioned in the literature as the environmental critical limit.

Soil P Olsen was highly correlated with PSI (R2= 0.82). In accordance to the regression equation to the ISP critical value of 25% corresponds a P Olsen of 78 mg kg-1.

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Use of volcanic mulch for saline-sodic rehabilitation: short and long term experiences in the Canary Islands

M. Tejedor, C. Jiménez and F. Díaz University La Laguna, Tenerife, Canary Islands

Soil salinisation and sodification, both of which are frequent processes in arid regions, lead to degradation of the land and are a major obstacle to land use. When the degradation is highly advanced, desertification can result. The use of mulch to rehabilitate saline-sodic soil in dry farming conditions has merited relatively little attention in the literature. In a previous work, (Tejedor et al., 2003a) we compared the salinity and sodicity of the arable layer of soils which had been covered with 10-15 cm of basaltic tephra more than 20 years ago and adjacent uncovered soils. The results demonstrated the important reduction in the salinity and sodicity of the mulched soils. What rate did/do these processes occur at? In this paper we present preliminary results of monitoring of the evolution of the saline profile in a clay-loam soil since it was covered with 12 cm of coarse grain basaltic tephra (with dominant grain size 2-8 mm, 77 %). The results are compared with those obtained in an adjacent uncovered soil. The study zone was located in Fuerteventura, an island with annual rainfall of less than 100 mm. A 100 m2 plot was covered with tephra in May 2001. Sampling has been carried out since then in the covered and uncovered soil after each dry and wet period. In each case, samples were taken every 10 cm to a depth of 1 m in 10 profiles (5 in the mulched soil and 5 in the uncovered soil) and the electrical conductivity (EC) was measured in 1:1 extract. The salt profiles obtained in this short experience (after only two years of tephra cover) were compared with those of adjacent soils which have been under mulch for over 20 years. The non-parametric Mann-Whitney U test was used for statistical analysis, with differences considered statistically significant at p<0.05. Figure 1 shows the evolution of the saline profile in the recently-covered soil and the uncovered adjacent soil, during the first year of the study. The initial sample (May 2001, figure 1a) -prior to covering the soil- was taken at the beginning of the dry period, when the soil had not yet reached its highest salinity levels. Following the first rainy season (83.5 mm, April 2002, figure 1b) considerable leaching of the salts was already evident in the top 30 cm of the tephra-covered soil, the EC falling to below 7 dS m-1. Subsequent accumulation of salts was seen at around 50 cm, with a maximum value of 28 dS m-1. In the soil without tephra the saline profile after the wet period was similar to the initial one. The differences between the covered and uncovered soils were statistically significant at 0, 10, 20 and 30 cm. After the dry period, (0 mm rain since the previous sample, October 2002, figure 1c), as expected, the flow was reversed and the salts rose again in the mulched soil, even though EC values were still low in the first 20-30 cm. At the same time, less salts were present in the zone in which it had accumulated during the wet period. No significant differences were found between the covered and uncovered soils. After the second period of rainfall (115.3 mm since the previous sampling) the leaching was considerably deeper although the saline profiles were similar to those of the first period,. Figure 2 shows the profiles after the second dry period (0 mm of rain between the two sampling periods, August 2003). The salts rise in the covered soil was lower than in the first dry period and the maximum accumulation threshold had reached 60-70 cm. Differences between the covered and uncovered soil were significant at 50, 60, 70 and 80 cm. The results obtained in this short and long term experience show that soils under tephra undergo a rapid leaching process, with subsequent accumulation. A comparison between this tendency and the saline profile of soils covered over 20 years ago (Figure 2) enables us to

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conclude that the leaching will continue, the accumulation zone will become deeper, albeit probably more slowly with the salt eventually disappearing from the first 100 cm of soil. The efficacy of this farming practice for rehabilitating saline soils is, we think, connected to moisture changes undergone by the soils when covered (Tejedor et al., 2003b). The reduction of salt in the root zone permits crop growth within one or two rainfall periods after the soils is covered.

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under mulch after second dry period

References Tejedor, M., C.C. Jiménez, and F. Díaz. 2003a. Use of Volcanic Mulch to Rehabilitate Saline-

Sodic Soils. Soil Sci. Soc. Am. J. 67:1856-1861. Tejedor, M., C.C. Jiménez, and F. Díaz. 2003b. Volcanic materials as mulches for water

conservation. Geoderma 117:283-295.

Weathering and allophane neoformation in soils on volcanic ash from the Azores.

M.Gerard 1, S.Caquineau 1, J.Pinheiro 2 and G.Stoops 3

1UR Geotrope, Institut de Recherche pour le Developpement, Bondy, France; 2Departamento de Ciencas Agrarias, Universitade dos Acores do Heroismo, Azores, Portugal; 3Laboratorium voor Mineralogie, Petrologie

en Micropedologie. Universiteit Gent, Belgium Two profiles of the Azores, respectively on the islands of Faial and Pico are studied from the point of view of petrography, micropedology and mineralogy. They consist of 150 cm thick sequences of paleosols developed on dominantly basaltic pyroclastic material, essentially of explosive origin, submitted to mesic-udic moisture regime. Attention is focused on the weathering of lapilli and ashes, and the neoformation of allophane. Combination of optical studies and in situ microprobe chemical analyses on thin section, X-ray diffraction analyses and selective extraction techniques on bulk samples revealed that allophane is present in the micromass of the groundmass, in the alteromorphs after lapilli or pumice and in clay coatings. As alteromorph after lapilli or pumice, allophane is the end product of the glass alteration in those samples. It is highly hydrated and related to in situ alteration. In the case of pseudo-alteromorph after feldspar, a dissolution-precipitation process creates large allophane coatings less hydrated. A grading alteration is observed trough three steps: 10% hydration of the glass associated to strong cations and Si leaching, allophane coatings, allophane alteromorphs with development of intra-grains bridges. Al/Si ratio of allophanes ranges between 1.3 and 2.5. Their chemical signature as determined by microprobe, varies from a pure alumino-silicate pole to an alumino-silicate Fe-Ti enriched pole (Fe/Al around 1). These ratios partly correlate with the ratios obtained during repetitive oxalate extractions. The Fe enriched allophane phase is proposed as a mixture of allophane and Fe oxyhydroxides at nanometric scale. Within the allophane bridges, micrometric zonations with Fe and Mn oxyhydroxides were also observed. In the Pico profile, an Al rich allophane is rather homogeneously distributed associated to gibbsite formation, especially important at the base of the pedon. In the base of the Faial profile, a Si rich allophane is associated to halloysite suggesting pedogenic environmental changes. This paragenesis Si rich allophane – halloysite - gibbsite characterizes a paleosol on olivine basalt. The two profiles are also controlled by a strong iron segregation visible at different scales with various secondary phases (ferrihydrite, hematite, iddingsite) that suggest also variations of the paleo-environment. A complex weathering pattern characterizes the Faial paleosols (weathering and hydrothermalism) within the horizons developed on 0 to 5500 years old pyroclastic deposits. The weathering pattern of the older Pico paleosols (over 10000 years old), is more simple but affected in the topsoil by huge humus content. The age of the soils seems to be the major factor for weathering differentiation but a climatic change is suspected around 10000 years ago.