Applied Geochemistry 33 (2013) 1–12

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Applied Geochemistry

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Mercury in European agricultural and grazing land soils

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⇑ Corresponding author. Tel.: +47 99091744; fax: +47 73901620.E-mail addresses: rolf.ottesen@ngu.no (R.T. Ottesen), clemens.reimann@ngu.no

(C. Reimann).1 S. Albanese, M. Andersson, A. Arnoldussen, M.J. Batista, A. Bel-lan, D. Cicchella, A.

Demetriades, E. Dinelli, B. De Vivo, W. De Vos, M. Duris, A. Dusza, O.A. Eggen, M.Eklund, V. Ernstsen, P. Filzmoser, D. Flight, M. Fuchs, U. Fugedi, A. Gilucis, V.Gregorauskiene, A. Gulan, J. Halamic, E. Haslinger, P. Hayoz, R. Hoffmann, J.Hoogewerff, H. Hrvatovic, S. Husnjak, C.C. Johnson, G. Jordan, L. Kaste, B. Keilert, J.Kivisilla, V. Klos, F. Krone, P. Kwecko, L. Kuti, A. Ladenberger, A. Lima, D. P.Lucivjansky,D. Mackovych, B.I. Malyuk, R. Maquil, P. McDonnell, R.G. Meuli, N. Miosic, G. Mol, P.Négrel, P. O’Connor, A. Pasieczna, W. Petersell, M. Ponavic, S. Pramuka, C. Prazeres, U.Rauch, H. Reitner, M. Sadeghi, I.Salpeteur, N. Samardzic, A. Schedl, A. Scheib, I.Schoeters, P. Sefcik, F. Skopljak, I. Slaninka, A. Šorša, T. Stafilov, E. Sellersjö, V.Trendavilov, P. Valera, V. Verougstraete, D. Vidojevic, Z. Zomeni.

Rolf Tore Ottesen a, Manfred Birke b, Tor Erik Finne a, Mateja Gosar c, Juan Locutura d,Clemens Reimann a,⇑, Timo Tarvainen e, the GEMAS Project Team 1

a Geological Survey of Norway, P.O. Box 6315 Sluppen, N-7491 Trondheim, Norwayb Federal Institute for Geosciences and Natural Resources (BGR), Stilleweg 2, D-30655 Hannover, Germanyc Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana, Sloveniad Instituto Geologico y Minero de Espana, Rios Rosas, 23, 28003 Madrid, Spaine Geological Survey of Finland, P.O. Box 96, FI-02151 ESPOO, Finland

a r t i c l e i n f o

Article history:Received 22 August 2012Accepted 24 December 2012Available online 4 January 2013Editorial handling by R. Fuge

a b s t r a c t

Agricultural (Ap, Ap-horizon, 0–20 cm) and grazing land soil samples (Gr, 0–10 cm) were collected from alarge part of Europe (33 countries, 5.6 million km2) at an average density of 1 sample site/2500 km2. Theresulting more than 2 � 2000 soil samples were air dried, sieved to <2 mm and analysed for their Hg con-centrations following an aqua regia extraction. Median concentrations for Hg are 0.030 mg/kg (range:<0.003–1.56 mg/kg) for the Ap samples and 0.035 mg/kg (range: <0.003–3.12 mg/kg) for the Gr samples.Only 5 Ap and 10 Gr samples returned Hg concentrations above 1 mg/kg. In the geochemical maps thecontinental-scale distribution of the element is clearly dominated by geology. Climate exerts an impor-tant influence. Mercury accumulates in those areas of northern Europe where a wet and cold climatefavours the build-up of soil organic material. Typical anthropogenic sources like coal-fired power plants,waste incinerators, chlor-alkali plants, metal smelters and urban agglomerations are hardly visible atcontinental scales but can have a major impact at the local-scale.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

Over the last 30 years, there has been much concern regardingthe toxic impact of mercury (Hg) in the ecosystem due to its mobil-ity and volatility, and potential for methylation and bioaccumula-tion. For example, Hg in fish is a great problem in the Nordiccountries (Fjeld and Rognerud, 2009).

The EU repeatedly requested the UNEP Governing Council totake a decision on the opening of negotiations on a global legallybinding instrument on Hg. In February 2009, the Governing Coun-cil finally decided to establish an Intergovernmental NegotiatingCommittee (INC) mandated for developing a global legally binding

instrument covering most aspects of the Hg life cycle. The firstsession of the INC took place in Stockholm, 7–11 June 2010, withthe objective of concluding early in 2013. The European Strategyon Hg and its implementation aims at making a significantcontribution to this process. Despite all these discussions the dis-tribution and natural background of Hg in, e.g., agricultural andgrazing land soils, has never been mapped and documented atthe continental-scale and thus the base for guided political deci-sions is missing.

Major Hg mines in Europe were situated in Spain (Almaden),Slovenia (Idria) and Italy (Monte Amiata), however mining of Hgterminated in the EU in 2003. Global Hg supply to the markets isnow dominated by three nations that mine mercury for export:Kyrgyzstan, Algeria and China. China may be in the process of clos-ing their mines, especially as other sources of Hg appear to begrowing, and mercury remains inexpensive on the internationalmarket.

EuroGeoSurveys (EGS) is a forum for cooperation between the34 geological surveys of Europe. EGS, in cooperation with Euromet-aux, the association of the European metal producers, initiated in2008 a project to document metal concentrations in European agri-cultural and grazing land soils at the continental-scale. Samplingwas organised, conducted and financed by the local Geological Sur-veys and partner organisations while Eurometaux financed samplepreparation and the chemical analysis of about 60 chemical

2 R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12

elements, including Hg. The overall project management lies withthe Geological Survey of Norway (NGU).

This article presents the analytical results for Hg from >4000soil samples, evenly distributed over Europe and discusses theimportance of natural versus anthropogenic sources and processeson the regional distribution of this element in European topsoil.

1.1. The survey area

Fig. 1 provides a simplified geological map of Europe, showingthe main features discussed in this paper. Further maps coveringtopography and land use of Europe can be found in almost anyworld atlas. For Europe, an excellent source of land use informationis the CORINE land use map of Europe (GLC2000 Database, 2003). Adetailed geological map of Europe is provided by Asch (2003), con-cise descriptions of the geology of Europe can be found in Blundellet al. (1992) and McCann (2008). The soil atlas of Europe provides awealth of information about the soils of Europe, but also containsmaps of average precipitation, temperature, land use, populationdensity, extent of the last glaciation and soil texture (Jones et al.,2005). A number of maps covering different themes at about thescale of the GEMAS project (topography, geology, tectonics, faultand fracture zones, distribution of different rock types, distributionof the main sedimentary basins, precipitation and population den-sity) can be found in Reimann and Birke (2010).

Fig. 1. Simplified geological map of Europe (modified from Reimann et al. (2012d)), theactive volcanic centres of Europe.

2. Methods

2.1. Sampling

Two thousand one hundred and eight samples of agriculturalsoil (Ap-horizon, 0–20 cm, Ap samples) and 2024 samples of graz-ing land soil (0–10 cm, Gr samples) were collected during 2008from large parts of Europe, with some few last samples arrivingearly in 2009. No samples were taken in Albania, Belarus, Malta,Moldova, Rumania, and Russia. Each sample was a composite offive single samples taken about 10 m apart from a large ploughedfield or patch of grazing land. The average sample weight was3.5 kg. A duplicate sample, ca. 100 m removed from the originalsample site, was collected at a rate of 1 in 20. Details of the sam-pling procedure can be found in the field handbook (EGS, 2008).The average sample density is 1 sample site/2500 km2 (Fig. 2Aand B).

2.2. Sample preparation

All samples were prepared in a single laboratory (Slovakia). Thesamples were dried at room temperature and sieved to <2 mmusing nylon screening. For analysis and storage for future reference10 splits of each sample were prepared using a Jones Rifflesplitter.

location of the three former major Hg producers in Europe is shown as well as the

Fig. 2. (A) Sample locations for the agricultural soil (Ap-samples) and (B) samplelocations for the grazing land soil (Gr-samples), EuroGeoSurveys GEMAS project.

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2.3. Chemical analysis

The samples were extracted with aqua regia and the content ofmercury and 52 further elements (including S) determined by ICP-AES and ICP-MS techniques by ACME laboratories in Canada. ThepH of the soil samples was measured in 0.01 M CaCl2 at NGU’s lab-oratory in a slurry of 16 g soil and 40 ml 0.1 M CaCl2-solution (forvery organic samples 10 g soil and 50 ml 0.1 M CaCl2-solution wereused). The samples were placed for 1 h into an automatic shaker.Immediately after shaking, pH values of all prepared samples weremeasured within 2 h using a pH-meter (Mettler Toledo Seven EasypH-meter) equipped with a standard glass electrode. Calibrations,using standard buffer solutions, were carried out every 40 samples.Total organic carbon (TOC) was determined according to ISO stan-dard 10694 ‘‘Soil quality – determination of organic and total car-bon after dry combustion’’. The measurements were performed

using a carbon/sulphur analyser (ELTRA, Helios) by Fugro laborato-ries in Berlin. More detailed method descriptions can be found inReimann et al. (2009a, 2011).

2.4. Quality control

For quality control purposes a field duplicate was collected atevery 20th site, an analytical duplicate was prepared from eachfield duplicate and inserted near the original sample with a differ-ent sample number, a project standard was inserted at a rate of 1 in20 samples and all samples were randomised prior to submissionto the laboratory. In addition a standard (control reference mate-rial) from an Australian continental-scale mapping program andthe North American soil geochemical landscapes project were alsoinserted several times (Reimann et al., 2012a). The two projectstandards of the GEMAS project, Ap and Gr, underwent in additionan international round robin test to be able to estimate the true-ness (bias) of the results.

Complete QC results, including X-Charts, Thompson and Ho-warth plots and an analysis of variance can be found in Reimannet al. (2009a, 2011, 2012b). The analysis of variance returned 93%(Ap) and 96% (Gr) on the ‘‘regional-scale variability’’ level. The re-sults are thus well suited to produce regional distribution maps.Analytical precision for Hg is in the range of 15% for both materials.The proficiency test with the two GEMAS standards Ap and Grshowed that the results for both standards are within the tolerancelimits of the international ring test – though on the low side (Apstandard expected value: 0.125 mg/kg Hg, Ap standard mean value(N = 124): 0.100 mg/kg Hg in aqua regia extract; Gr standard ex-pected value: 0.149 mg/kg, Gr standard mean value (N = 118):0.120 mg/kg Hg in aqua regia extract).

2.5. Map production and statistical methods

Geochemical data are compositional (closed) data; elementconcentrations reported in wt.% or mg/kg sum up to a constantand are thus not free to vary independently of one another. Theinformation value of such data lies in the ratios between the vari-ables (Aitchinson, 1986; Filzmoser et al., 2009). Filzmoser et al.(2009) discuss problems and possibilities of univariate data analy-ses for compositional data. The solutions suggested in Filzmoseret al. (2009) for the univariate case (bivariate or multivariate anal-ysis is not considered here) are used throughout this paper. Interms of calculating statistical parameters such as mean or stan-dard deviation it is important to note that compositional data donot plot in the Euclidian space but rather on the Aitchison simplex.Statistics presented here are thus built around percentiles and thestandard deviation is replaced by the powers, the orders of magni-tude variation of the data ranges (Reimann et al., 2012c).

Colour surface maps are generated from gridded data. A basicproblem in producing colour surface maps is that the measure-ments are irregularly distributed across the mapped area, whereasthe pixels form a regular grid. Kriging was used to convert the val-ues from irregularly distributed sampling sites to a regular grid forrepresentation of the geochemical data on a map. The parametersof the kriging function are based on variogram analysis.

3. Results

3.1. Mercury concentrations in European agricultural and grazing landsoils

Table 1 summarises the Hg results for the European Ap and Grsamples. Fig. 3 shows the Hg distribution of the Ap and Gr soil sam-ples in the form of a combined histogram, density trace, boxplot

Table 1Statistical summary of the analytical results for Hg in an aqua regia extraction of agricultural soils (Ap, 0–20 cm, <2 mm) and grazing land soil (Gr, 0–10 cm, <2 mm) from Europe.n: number of samples; DL: detection limit; Min.: minimum; Q: quantile of the distribution (Q50 = median); Max.: maximum. Powers: orders of magnitude variation.

Element Material n Unit DL %<DL Min. Q2 Q5 Q10 Q25 Q50 Q75 Q90 Q95 Q98 Max. Powers

Hg Ap 2108 mg/kg 0.003 0.76 <0.003 0.0056 0.0085 0.012 0.018 0.030 0.048 0.076 0.10 0.19 1.6 3Hg Gr 2024 mg/kg 0.003 0.35 <0.003 0.0072 0.0099 0.013 0.020 0.035 0.059 0.094 0.13 0.21 3.1 3.3

Fig. 3. The Hg data distribution of agricultural (Ap) and grazing land (Gr) soils of Europe displayed in a combination of histogram, density trace, one-dimensional scattergramand boxplot.

Fig. 4. Boxplots comparing Hg in agricultural and grazing land soils in the countries participating in this survey. The countries are sorting according to decreasing medianconcentrations. AUS: Austria, BEL: Belgium, BOS: Bosnia and Herzegovina, BUL: Bulgaria, CRO: Croatia, CYP: Cyprus, CZR: Czech Republic, DEN: Denmark, EST: Estonia, FIN:Finland, FOM: Former Yugoslavian Republic of Macedonia (FYROM), FRA: France, GER: Germany, HEL: Hellas, HUN: Hungary, IRL: Republic of Ireland, ITA: Italy, LAV: Latvia,LIT: Lithuania, LUX: Luxemburg, MON: Montenegro, NEL: The Netherlands, NOR: Norway, POL: Poland, PTG: Portugal, SIL: Switzerland, SKA: Slovakia, SLO: Slovenia, SPA:Spain, SRB: Serbia, SWE: Sweden, UKR: Ukraine, UNK: United Kingdom.

4 R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12

and one-dimensional scattergram. Both plots demonstrate thatthere is a small group of samples below detection (0.76% for theAp samples and 0.35% for the Gr samples, see Table 1). The boxplotand one-dimensional scattergram indicate the presence of a lim-ited number of upper and lower outliers (Fig. 3). The distributionof the main body of data is for both sample materials very symmet-rical in the log scale. Table 1 suggests that the Hg concentrations in

the Gr samples are slightly higher than those of the Ap samples, aWilcoxon rank sum test for equality of the medians (Reimann et al.,2008) returns a p-value of <0.05, the observed difference is thusstatistically significant.

When comparing the median values of the different countriesusing boxplots in Fig. 4 a more than 6-fold difference in the Hgmedian values becomes visible at the European-scale – Slovenia

R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12 5

(followed by Ireland and Austria) shows the highest median value(Ap Slovenia: 0.084 mg/kg, Gr Slovenia: 0.091 mg/kg), Bulgaria, fol-lowed by Ukraine and Cyprus (Ap Cyprus: 0.011 mg/kg, Gr Cyprus:0.014 mg/kg) the lowest.

The Hg concentrations reported here for European soils com-pare well with results reported from other parts of the world(see, e.g., Reimann and Caritat, 1998). In terms of action levels de-fined for sensitive land use in various countries, which vary be-tween 1 and 23 mg/kg (Provost et al., 2006), the mercuryconcentrations reported here are generally low. Only seven sam-ples (2 Ap, 5 Gr) reported Hg concentrations above 1 mg/kg.

3.2. Geographical distribution of mercury in agricultural- and grazingland soils

The maps for the Ap and Gr samples are almost identical andthus only the Ap-map, with the spatially more extensive coverage(almost no Gr samples were collected in Finland) is shown here(Fig. 5). The most pronounced pattern on the map of Hg in agricul-tural soils (Fig. 5) is the visible difference in Hg concentrations

Fig. 5. Geochemical map of mercury in European agricultural soils (Ap). Anomalies are

between northern (low, median 0.024 mg/kg) and southern (high-er, median: 0.036 mg/kg) Europe. A band of coarse grained quartzrich glacial sediments in northern Central Europe is clearly markedby particularly low Hg concentrations and the border betweennorthern Europe with overall lower Hg concentrations and south-ern Europe with overall higher Hg concentrations outlines exactlythe southern limit of the last glaciation (see Fig. 1). In contrast tomany other elements (e.g., Pb – Reimann et al., 2012d; or As – Tar-vainen et al., 2013) mercury concentrations do not remain lowthrough all of northern Europe, instead quite a number of well de-fined local Hg anomalies are observed in Scandinavia. In generalthe map shows a striking number of locally restricted Hg anoma-lies throughout all of Europe. In order to understand the sourceof the anomalies, all important Hg anomalies were numbered onthe Ap map (Fig. 5). An attempt to provide an explanation for eachof these anomalies is presented in the accompanying Table 2.

Based on the map one can actually divide the dataset into 4large consistent regional zones with distinctly different Hg concen-trations and variation: (1) Scandinavia (Norway, Sweden, Finland),(2) Balticum (Denmark, Poland, Latvia, Lithuania, Estonia and

numbered and an explanation for the numbered anomalies is provided in Table 2.

Table 2Explanation of the anomalies observed and numbered in Fig. 5.

Country Name Likely source, remarks

Mercury anomalies in European agricultural soil1 Sweden Östersund (S), Wilhelmina

(N)Geology/mineralisation

2 Finland North Karelia Climate, soil formation; enrichment in organic rich samples3 Finland Alajärvi Climate, soil formation; enrichment in organic rich samples4 Finland South Savo Climate, soil formation; enrichment in organic rich samples5 Finland Hämeenlinna Enrichment in organic rich samples6 Norway Bergen area Climatic/contamination; high rainfall along coast, build up of organic material; the Odda Zn smelter is located

within the anomaly7 UK N Scotland Climate, soil formation; enrichment in organic rich samples, anomaly cuts across regional geology8 UK Midland Valley Contamination/mining; coal burning, coal mining9 UK Unknown; upland area, granite intrusion in greywacke minor basemetal mineralisation, possibly effect of

accumulation in organic rich soils10 UK Combination of anthropogenic and natural factors; urban contamination, coal burning, mining/ash disposal but also

organic rich soils and a coalfield11 Ireland Mineralisation; associated with Zn–Pb mineralisation in Carboniferous rocks12 Ireland Dublin Contamination/Mineralisaton; Dublin city and widespread Zn–Pb mineralisation to the north of Dublin in

Carboniferous rocks13 UK Birmingham Contamination14 UK Unknown, the area shows in general an unusual geochemical signal15 UK London Contamination, greater London area16 Netherland Contamination (?); no likely geological/natural source17 Netherland Amsterdam/Rotterdam Contamination; greater Rotterdam area18 Belgium Oedelem Spurious contamination (?); no likely geological source, no industry19 Germany Geology/mineralisation: eastern part: Thuringian-Vogtland Slate Mts. (incl. structurally controlled Sb–(Au)

mineralisations); western part: Vogelsberg20 Germany/

Czech Rep.Lusatian mountains, Oremountains

Geology/contamination; fault zones, anthropogenic contribution from brown coal mining and burning in the CZRepublic likely but note that the brown coal contains elevated Hg background concentrations

21 Poland Western Sudetes Mineralisation22 Ukraine Contamination – no likely geological source23 Belgium Kortessem spurious contamination (?); no likely geological source, no industry24 France Paris Contamination, greater Paris area25 France Verdun Contamination (?) – WW1? – this is also the site of an unexplained Pb anomaly26 Slovakia Krompachy Mineralisation/mining /contaminatio; Fe and Cu mineralisation zone with Hg as minor component, old mining area,

contamination by emissions from ores processing27 Hungary28 Ukraine Carpathians Geology; sedimentary rocks with anomalous concentrations of Hg, Ba, Cd and F related to alpine orogenesis29 France Vosges Mineralisation(?)/Contamination (?) – there is known sulphide mineralsation in the area but also several waste

incinerators30 Austria/

GermanyTirol Mineralisation/Mining/Geology; Western Greywacke Zone (e.g. ore deposits Schwaz-Brixlegg, Kitzbuehel area),

Mineralisations in Silvretta Complex, Werfen Slate Formation31 Austria Steiermark Mineralisation/Mining in the Eastern Greywacke Zone (e.g. Erzberg ore deposit)32 Austria/

HungaryBurgenland Geology (tertiary volcanism, hot springs) or agriculture(?) – this is one of the most intensively cultivated areas in

Austria33 Switzerland Mineralisation/contamination – cannot be decided at scale of this study, there are known sulphide mineralisations

in this area as well as an Al-smelter34 Slovenia Unknown source/agriculture(?) – the anomaly is too far east to be related to Idrija35 Spain Santander, Cantabria/

AsturiasMineralisation/mining/ore processing; vein mineralisation in limestones, MVT Zn deposits with Hg-rich Zn ore

36 Spain Sierra de la Demanda Mineralisation; base metal vein mineralisation with trace of Hg37 Italy Larderello-Travale-Monte

Amiata areasMineralisation/mining/geology; Acid Tuscan magmatism with associated geothermal fields

38 Bosnia Sarajevo-Vareš Mineralisation/mining/ore processing; Zn,Pb deposit with Hg and mining and ore processing related contamination39 Serbia Geology/mineralisaton/contamination: Serbian–Macedonian metallogenic province40 Italy Sabatini, Albano Hills

(Rome)Geology/contamination (?); potassic and ultrapotassic lavas and pyroclastics, fumaroles, but also Rome as a likelyanthropogenic source

41 Serbia Geology/mineralisaton/contamination; Serbian–Macedonian metallogenic province and Dinaric metallogenicprovince

42 Italy Phlegrean Fields, Vesuvius Geology/contamination(?); potassic and ultrapotassic lavas and pyroclastics , fumaroles and springs but also Naplesas possible anthropogenic source

43 Spain Almaden Mineralisation/mining/ore processing; southern part: vein mineralisation at fringes of Pedroches batholith

6 R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12

Ukraine), (3) Central Europe (Ireland, United Kingdom, The Nether-lands, Belgium, Germany, Austria, Switzerland, Czech Republic,Slovakia, Slovenia, Hungary, Serbia, Bosnia, Luxembourg) and (4)Southern Europe (Portugal, Spain, France, Italy, FYROM, Hellas

and Cyprus). Table 3 shows statistics for Hg, TOC, pH and S in these4 subsets and the observed differences are indeed substantial (forHg: median Central Europe� Scandinavia > Southern Europe >Balticum).

R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12 7

4. Discussion

4.1. General patterns in the maps

When studying the map (Fig. 5) it is at first glance tempting toassign the almost double as high median Hg concentration in Cen-tral Europe to an overall higher level of contamination of CentralEuropean agricultural soils with Hg. However, the patterns onthe map cannot really be explained by the impact on the soils ofanthropogenic activities or long (or even short) range transportof Hg via the atmosphere. The concentration break along the glacialboundary is clearly related to geology and soil type. The lowest Hgconcentrations in Europe occur in northern central Europe in soilsdeveloped on the sediments from the last glaciation in an area thatis densely populated and where many coal fired power stations –according to Weem (2011) the main source of anthropogenic Hgemissions in Europe – are situated. In that respect the big differ-ence in Hg concentrations and number of anomalies between Po-land and Germany and between Germany and France (Fig. 5) isnoteworthy. While the difference between France and Germanycould be explained by differences in power generation, this expla-nation does not hold for Poland with large coal fired power plants,where especially low Hg concentrations are found in the agricul-tural soils. The central European Hg anomaly thus cannot be sim-ply explained by a major difference in Hg emissions. Accordingto Table 2 many anomalies on the map can actually be linked toknown sources, often geology and/or known ore deposits. For allanomalies, independent of source, a steep concentration declineis visible with distance from source.

4.2. Anomalies related to mineralisation

Three famous and large Hg deposits have been mined in Europefor hundreds of years: Almaden in Spain, Monte Amiata in Italy,and Idrija in Slovenia. On first glance it appears that all three areindicated by high Hg values in the agricultural soils in their widersurroundings (anomalies 43, 37 and 34 in Fig. 5, Table 2). The mer-cury distribution in soils of the Almadén mercury district (size: ap-prox. 300 km2) are regarded as the largest geochemical anomaly ofmercury on Earth, detailed investigations at a high sampling den-sity revealed mercury contents of 6–8889 mg/kg (Higueras et al.,2006), much higher than any value detected at the GEMAS sampledensity.

On close scrutiny anomaly 34 occurs more than 60 km to thesouth-east of Idrija in a rural area without any industry and cannotbe associated with the mine or ore processing plant. Yet, one of themost important districts influenced by mercury mining and oreprocessing in Europe is the area around the Idrija mercury mine.When carrying out more detailed geochemical surveys in the sur-roundings of the mine, half a millennium of mercury production isreflected in increased mercury contents in all environmental com-partments (Gosar and Šajn, 2001, 2003; Gosar et al., 2006; Gosarand Teršic, 2012). Systematic detailed investigations of mercuryconcentrations and its spatial distribution during 2000–2001 cov-ering an area of 160 km2 around the Idrija mercury mine showedvery high values in the Idrijca River valley near the contaminationsource (smokestack) (Gosar and Šajn, 2001, 2003; Gosar et al.,2006). However, mercury concentrations decreased exponentiallywith distance from the source. The research area was divided intothree parts. The first part (Area 1; 8.8 km2) included the towns ofIdrija, Spodnja Idrija and the Idrijca River valley between them;the Area 2 (51 km2) included the area in the vicinity of the townsof Idrija and Spodnja Idrija and the Area 3 (108.7 km2) included awider area around both towns. The highest median mercury con-centrations occurred in Area 1 (47 mg/kg for soil). The median

for Area 2 was 3.2 mg/kg and for Area 3 it was ‘‘only’’ 1.0 mg/kg(Gosar et al., 2006). The New Dutchlist of intervention and targetvalues for Hg (10 mg/kg; MHSPE (Ministry of Housing and theEnvironment), 1994 was exceeded across 19 km2 of the studiedarea (Gosar et al., 2006). The Hg distribution in soil samples dem-onstrated that the influence of atmospheric emissions caused bythe Idrija roasting plant resulted in severe environmental impactson a local to sub-regional scale (Gosar et al., 2006). Recently, inter-esting and extremely contaminated locations (Hg concentrations insoil samples up to 19,900 mg/kg) of historical small productionroasting sites were discovered in the Idrija surroundings (Teršicand Gosar, 2009; Teršic et al., 2011a,b). Furthermore, systematicmonitoring of mercury levels in stream sediments draining theIdrija area has demonstrated that mercury-rich material is depos-ited during floods on the floodplains in the lower part of the Idrijcaand Soca River valley. This process leads to mercury-accumulationsover large areas (Gosar et al., 1997; Biester et al., 2000; Zibret andGosar, 2006; Gosar, 2008; Gosar and Zibret, 2011). It is thus inter-esting that Idrija is not marked in the GEMAS results as a clearanomaly. The reason is that the samples for the GEMAS projectwere taken at a considerable distance from the Idrija district. Theclosest sampling site for GEMAS was 24 km removed in the SWdirection, which is not the main wind direction because the IdrijcaRiver valley follows an overall NW direction. The next closest GE-MAS sampling point is at a distance of more than 35 km from Idri-ja. Although a severe Idrija influence on the local-scale was proven(Gosar et al., 2006) it is clear that the sampling density for the GE-MAS project was not dense enough to detect a Hg anomaly in thearea of the Idrija mercury mine. It is, however, remarkable that theSlovenian Hg median values in agricultural soil (0.084 for Ap and0.091 for Gr) are the highest in Europe. The unusually high Hgmedian value for Slovenia must be interpreted as influenced eitherby regional-scale processes that led to the formation of the Idrijadeposit or by contamination due to hundreds of years of Hg miningand smelting at a country-wide-scale.

According to Table 2 many further Hg anomalies on the map aredirectly related to known ore occurrences or districts. Most ofthese have been mined at some time in the past and a metal pro-cessing industry has developed in these same areas. At the resolu-tion of a continental-scale map (Fig. 5) it is thus difficult toimpossible to differentiate the natural versus the anthropogenicorigin of the Hg signal. Such differentiation will require geochem-ical mapping at a much more detailed scale (as described above forIdrija, several samples per km2), typical for local studies, e.g., urbangeochemical investigations (Johnson et al., 2011) or mineral explo-ration projects (Reimann et al., 2009b, 2010; Cohen et al., 2011).

4.3. Anomalies related to regional geology

Mercury is a very rare chalcophile heavy metal. The principalmineral is cinnabar (HgS). The large size of the Hg2+ ion (1.10 Å)hinders incorporation into many rock forming minerals (Wed-epohl, 1978). The Hg-concentrations in igneous rocks are thuslow. Mercury is often enriched in shale, especially in black shalesand in coal. Volcanic hot springs and sedimentary rocks alteredby phreatic activities are the main sources of Hg-mineralisations(De Vos and Tarviainen, 2006). Natural sources of mercury releasesto the atmosphere include volcanoes, evaporation from soil andwater surfaces, degradation of minerals and forest fires (e.g., Ras-mussen, 1996). In the maps one natural source of Hg appears tobe the Phlegrean fields and Vesuvius (anomaly 42 in Table 2,Fig. 5), but note that there is also a major city in the same area (Na-ples), which is also a likely source for unusually high Hg values insurrounding agricultural soils. Note that none of the other activevolcanic areas in Europe is indicated by an Hg anomaly. Severalshale areas in Europe are indicated by enhanced Hg values

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(>75th percentile, yellow colors in the map), e.g., in Sweden, Nor-way (Oslo area with occurrences of black shale), Germany and Aus-tria. A major feature on the map directly related to geology are nothigh Hg values but rather the unusually low concentrations of Hgin the coarse grained young soils developed on glacial sedimentsin central northern Europe.

4.4. Anomalies related to climate and soil formation

Several other elements where the regional distribution is mostcommonly associated with human activities (e.g., As, Pb – Tarvai-nen et al., 2013; Reimann et al., 2012d) show a distinct break inconcentration between southern (high) and northern (low) Euro-pean soils. In contrast, Table 3 demonstrates that at the continen-tal-scale the second highest Hg concentrations occur in theScandinavian soils. Some low level anomalies can be directly re-lated to known mineralisation (e.g., Area 1 in Sweden, Fig. 5).The major anomaly in Scandinavia, however, is observed inNorway, along the west coast in the Bergen area (Fig. 5). This areareceives some of the highest rainfall in all of Europe: 2800–4000 mm/year annual average precipitation. A wet and cold cli-mate leads to the development and build-up of soils that areunusually rich in organic material. Mercury has a strong tendencyto bind to organic material and a strong affinity to sulphur (see TOCand S in Table 3) and consequently it is enriched in such areas. Thesame observation has for example been reported for Se, anotherelement with a strong tendency to organic binding from this loca-tion in forest soils (Låg and Steinnes, 1978). The general associationof Hg to total organic carbon is depicted in Fig. 6; the association isstrongest in the Scandinavian countries where especially organic-rich soils occur due to the climatic conditions. The high Hg back-ground in Scandinavia is thus due to climate and related soil types.Another such Hg anomaly that is due to climatic conditions and the

Table 3Summary statistics of Hg concentrations in an aqua regia extraction, total organic carbon (TBaltic countries, (3) Central Europe and (4) Southern Europe.

Subarea Material (N) Hg (mg/kg)

Minimum Median

Scandinavia Ap (453) <0.003 0.030Gr (350) <0.003 0.037

Baltic Countries Ap (373) <0.003 0.019Gr (374) <0.003 0.020

Central Europe Ap (578) <0.003 0.050Gr (591) <0.003 0.058

Southern Europe Ap (714) <0.003 0.025Gr (709) <0.003 0.027

Fig. 6. Scattergram of TOC versus Hg in the Ap and Gr sample

related accumulation of organic material in the soils occurs in N-Scotland (Area 7 in Fig. 5).

Samples that fall outside the general TOC/Hg trend in Fig. 6 andtend towards unusually high Hg values are either directly relatedto mineralisation or contamination. The majority of these samplesoriginate in central Europe.

The strong dependency of Hg concentrations on soil type areespecially apparent when studying results from just one remotenorthern country with a comparatively low population densityand few local Hg emission sources like Finland. In Finland the soilparent material (clay, sand, till and peat) was reported from eachsample location. When encoding soil parent material into a scatter-gram of TOC versus Hg concentration, the diagram (Fig. 7) showsimmediately that the peat soils are strongly enriched in Hg, inde-pendent of sample location (note the distribution of the Hg anom-alies in the map – Fig. 5). The high Hg concentrations are not due tocontamination, long range atmospheric transport or any other hu-man influence, Hg builds up by purely natural processes in organicsoils. Note that clay-rich soils are the second group of samplesshowing elevated Hg concentrations when compared to till-de-rived or sandy soils (Fig. 7). This is likely due to the greater numberof adsorption sites on clay-rich soils relative to sandier soils.

4.5. Anomalies related to contamination

4.5.1. Combustion of coal in power plantsAccording to Weem (2011) coal fired power plants (CFPP) are

the largest anthropogenic stationary source of mercury emissionsin Europe. 193 major coal fired power plants are currently in oper-ation in Europe. The mercury content of coal is typical in the rangeof 0.05–0.2 g/ton (USGS, 1995; see: http://pubs.usgs.gov/fs/fs095-01/fs095-01.html). Coal consumption in Europe is about 1 billiontons per year (Weem, 2011).

OC), pH in a CaCl2 extraction and S (aqua regia extraction) for (1) Scandinavia, (2) the

TOC (wt.%) pH_CaCl2 S (mg/kg)

Maximum Median Median Median

0.28 2.6 4.9 2842.21 4.6 4.5 4330.91 1.5 5.9 1630.21 2 5.6 2171.56 1.9 6.1 2473.12 3.3 5.5 3971.15 1.3 6.9 1582.31 1.9 6.7 214

s, symbols according to the four areas defined in Table 3.

Fig. 7. Scattergram of TOC versus Hg for the Ap samples from Finland with soilparent material additionally encoded in the symbols.

R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12 9

Mercury is volatilised during the combustion and converted togaseous elemental mercury Hg(0). Subsequent cooling of the fluegas and interaction of Hg(0) with other flue gas constituents, suchas chlorine and unburned carbon, results in partial oxidation of theHg(0) to gaseous oxidised forms of mercury Hg(2+) and particu-late-bound mercury Hg(P). As a result, coal combustion flue gascontains varying percentages of Hg(P), Hg(2+), and Hg(0). Interest-ingly, with very few exceptions (e.g., Area 35 in Fig. 5 in N-Spain)the anomalies in the maps do not show a direct relation to the loca-tion of coal fired power plants. Quite to the contrary, Poland, withan abundance of coal fired power plants, shows exceptionally lowHg levels in its agricultural soils. Many other locations with majorcoal fired power plants throughout Europe do not show a relatedHg anomaly. At a more detailed scale covering a few km2 insteadof a continent the Hg emissions of these power plants could cer-tainly be demonstrated. Fig. 8 shows the intensity of CO2 emissionsthroughout Europe and the location of major CO2 emission sites,including all coal fired power plants based on the CARMA database(Wheeler and Ummel, 2008). It is clear that this map has little rela-tion to the distribution of Hg in agricultural and grazing land soilsof Europe. One can conclude that combustion is not a major, oreven important, source of Hg in agricultural and grazing land soilsat the European-scale.

4.5.2. Chlor-alkali plantsDuring 2004 in the European Union 53 chlor-alkali plants

employing mercury were in operation (Winalsky et al., 2005). Theyheld 12,000 tons of pure mercury (Maxson, 2004). In line with theEuro Chlor commitment, these plants will be decommissioned and/or converted to use an alternative mercury free process by 2020(Euro Chlor, 2010).

In the last 15 years at least 34 chlor-alkali plants in the Nether-lands, Germany, United Kingdom, Finland, France, Sweden, Nor-way, Italy, Portugal, Belgium, Spain, Austria and Denmark wereshut down either completely, or the part employing a mercury-based process, with some of these plants having been convertedto the Hg-free membrane technology (Maxson, 2004). The twochlor-alkali plants in Norway were closed in 1987 and 1998,respectively. Official statistics show that chlor-alkali plants arethe second most important mercury emission source in Europe

with 1 metric ton in 2001 (Pirrone et al., 2010). However, againthe Hg distribution maps show no relation to the distribution ofchlor-alkali plants in Europe, hardly any of the observed anomaliescan be directly linked to the presence of a chlorine factory in themaps. The reason is again the continental-scale of thisinvestigation.

One example is the Borregaard chlor-alkali plant near Sarps-borg, in Norway, which was opened in 1949 (Ottesen, 1989). Theproduction was based upon the amalgam-method in which a con-siderable quantity of mercury is used. The total amount used at anyone time was about 100 tons. In the period 1949–1987 a quantityof 130 tons of mercury was lost from the factory. Some of the losswas directly to the atmosphere by vapour through the ventilationsystem and chimneys. The mercury also found its way into theground through cracks in the floor or via leaking sewage pipes.The Geological Survey of Norway carried out a detailed investiga-tion of the site. Very high mercury levels, 1.17–1000 mg/kg witha mean value of 148 mg/kg Hg based on 17 samples, were found in-side the plant. However, normal mercury contents in top soils of<0.05 mg/kg were found at a distance of just 1 km from the plant.It is thus no surprise that such sources are not exhibited in a Euro-pean-scale map. As significant as the impact of these sources is atthe local scale (see also above, Idrija), it will be very difficult toimpossible to prove the anthropogenic impact at the continental-scale, against a high natural variability of Hg in soils developedon different substrates and under differing climatic conditions.

4.5.3. Metal smeltersMetal smelters can also be an important source of mercury

emissions to the surrounding local soils. An illustrative exampleis the Odda zinc-smelter in western Norway where detailed soilmapping has proven that local soils are Hg-contaminated (Jartunet al., 2004). Two hundred and seventy soil samples taken in thesurroundings of the smelter returned a median Hg concentrationof 0.15 mg/kg and a maximum value of 270 mg/kg, compared toa median value of 0.03 mg/kg Hg for the Ap horizon at the Euro-pean-scale. A sample collected at some km distance from the Oddasmelter is part of the Hg anomaly in Area 6 on the map (Fig 5).

In Kiev (Ukraine) a Hg (cinnabar) processing plant is situatedright in the city centre. This source causes anomaly 22 on themap (Fig. 5) and provides a nice example of the scale of contami-nation from a major industrial source, probably the largest stillin existence in Europe.

4.5.4. Urban agglomerationsThe Geological Surveys of Europe have a long tradition of carry-

ing out geochemical investigations of urban areas (a summary isprovided in Johnson et al. (2011)). One of the elements that is typ-ically found strongly enriched in urban soils is Hg. However, again,Hg concentrations decline fast with distance from source, and lowEuropean background levels are usual found at a distance of somefew km from the city boundaries. This is demonstrated in Birkeet al. (2011) for the German capital, Berlin. The inner city soils(N = 2182) returned a median Hg concentration of 0.19 mg/kg (ob-served maximum value 71.2 mg/kg), while the soil samples takenin the surroundings of Berlin (N = 1564) show a median value of0.05 mg/kg Hg. The latter is already quite well in agreement withthe European median value of 0.03 mg/kg Hg reported here andit is thus no surprise that Berlin is not visible as an Hg anomalyat the scale of the European map (Fig. 5). The detailed Hg citymap of Berlin presented in Birke et al. (2011) is a good examplefor ‘‘the scale of contamination’’. Many distinct local anomaliesare identified that can be linked to chemical industry productionfacilities, hospitals, waste incinerators, crematoria, etc., while themain Hg anomalies in the Berlin area are due to sewage disposalareas. Parks where sewage has been used as fertilizer can also be

Fig. 8. Map of powerplant CO2 emissions in Europe for the year 2007 – data from the CARMA database (Wheeler and Ummel, 2008).

10 R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12

identified by enhanced Hg concentrations in their soils. All theseanomalies have a scale of some hundreds of metres at most. How-ever, several Hg anomalies in the European scale maps are relatedto urban agglomerations and do not have any likely natural sourceof Hg, typical examples are areas 15 (London), 17 (Rotterdam), and24 (Paris) in Fig. 5 which are all most likely due to contaminationin the surroundings of major cities. The Paris anomaly has alsobeen reported by Baize et al. (2001) and was interpreted as relatedto waste incineration. Several of the Hg anomalies in France occurnear waste incinerators and at the scale of this study it is oftenquite difficult to come to a conclusion about the real source ofthe Hg seen in the soil samples.

4.5.5. Seed dressing/fertilizers/agricultureIn agriculture, mercury has been used for seed dressing as anti-

microbial and fungicidal chemical prior to planting. Although this

use of mercury on agricultural soils was prohibited many yearsago, one might still expect to find some enhanced Hg values asan inheritance in intensively farmed agricultural areas. Further-more, sewage sludge, as noted above has been used as fertilizeron agricultural soils, is notorious for enhanced Hg concentrations.However, in the maps at the European-scale presented here thereare no clear indications of enhanced mercury levels due to agricul-tural practice (note that Area 32 in Fig. 5 may be an example aswell as the generally somewhat enhanced Hg levels in CentralEurope).

5. Conclusions

Overall Hg levels in European agricultural soils are low (medianagricultural soil (Ap) 0.030 mg/kg, median grazing land soil (Gr)0.035 mg/kg). The statistically significantly higher median in the

R.T. Ottesen et al. / Applied Geochemistry 33 (2013) 1–12 11

grazing land soil samples is related to the substantially higheramount of organic material in the grazing land soils (median TOCGr: 2.7 wt.% versus median TOC Ap: 1.8 wt.%).

The strong link of Hg with organic material is also visible in therelatively high Hg levels in the Scandinavian soils. Here many localanomalies are related to the occurrence of peat soils and in generalto high organic matter content in soils developing in wet and coldlocations, climatic conditions that favour the development of or-ganic-rich soils (e.g., west coast of Norway, N-Scotland).

In general the regional distribution of Hg in the European-scalemaps is dominated by natural sources and processes. For example,a main break in Hg concentrations is visible in northern centralEurope, where the sediments of the last glaciation are marked bylow Hg concentrations over vast areas. This concentration breakdoes not coincide with the established distribution maps of Euro-pean Hg contamination sources and proves that the majority ofHg in the agricultural and grazing land soils is still of natural origin.The majority of Hg anomalies can be linked to geological sourcessuch as sulphide mineral deposits, volcanic activity, and shale/slatebelts. In the case of mineralisation, it is quite likely that the pat-terns have an anthropogenic overprint due to mining and the re-lated metals industry that has usually developed in the sameareas. The proportion of such anomalies that is geogenic andhow much is due to contamination cannot be answered whenmapping at the European-scale, to answer this question detailedgeochemical investigations, often requiring several samples perkm2, are needed. Such studies show that in the surroundings ofall established Hg contamination sources Hg concentrations in soilsamples decline rapidly (usually exponential) with distance fromthe source.

Low density (1 site/2500 km2) geochemical mapping of Hg inagricultural and grazing land soils of Europe has demonstratedthat: (1) low density mapping is a valid approach, the statisticaland spatial distributions of Hg in two different sample materialsare comparable; (2) geology is the main factor determining the ob-served Hg concentrations in the soils; (3) climate and soil type playan important role in influencing the observed Hg levels; (4) whendealing with a continent, large areas with different patterns ofbackground variation must be expected, there is not just one valueidentifying ‘‘the background’’ or ‘‘good soil quality’’; and (5) serioussoil contamination is hardly detectable at the European-scale. Topinpoint contamination sources local scale mapping (several sam-ples/km2) is needed. Indeed, continental-scale maps of all chemicalelements are needed to document the present status of soil qualityas well as for any discussion of human impact on the environment.Mapping such large areas does not need to be excessively expen-sive when using a low density sampling approach. In terms ofmonitoring it is much cheaper to use regional maps as presentedhere to choose a few monitoring sites at places, where a problemor a large gradient is observed rather than doing detailed-scale soilmonitoring of a whole continent. Finally, observations made at thelocal or site-related scale should not be extrapolated to the conti-nental- or the global-scale.

Acknowledgements

The GEMAS project is a cooperation project of the EuroGeoSur-veys Geochemistry Expert Group with a number of outside organ-isations (e.g., Alterra in The Netherlands, the Norwegian Forest andLandscape Institute, several Ministries of the Environment andUniversity Departments of Geosciences in a number of Europeancountries, CSIRO Land and Water in Adelaide, Australia) and Euro-metaux. The analytical work was co-financed by the followingorganisations: Eurometaux, Cobalt Development Institute (CDI),European Copper Institute (ECI), Nickel Institute, Europe, EuropeanPrecious Metals Federation (EPMF), International Antimony

Association (i2a), International Manganese Institute (IMnI), Inter-national Molybdenum Association (IMoA), ITRI Ltd. (on behalf ofthe REACH Tin Metal Consortium), International Zinc Association(IZA), International Lead Association-Europe (ILA-Europe), Euro-pean Borates Association (EBA), the (REACH) Vanadium Consor-tium (VC) and the (REACH) Selenium and Tellurium Consortium.Finally, the Directors of the European Geological Surveys and theadditional participating organisations, are thanked for makingsampling of almost all of Europe in a tight time schedule possible.

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