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Compost use in viticulture:Effect on heavy metallevels in soil and plantsFlavio Pinamonti b , Giorgio Nicolini a ,Alessandro Dalpiaz a , Gino Stringari a &Gianni Zorzi aa Istituto Agrario di San Michele all'Adige ,via E. Mach 1, San Michele all'Adige, 1–38010,Italyb Istituto Agrario di San Michele all'Adige ,via E. Mach 1, San Michele all'Adige, 1–38010,Italy E-mail:Published online: 11 Nov 2008.

To cite this article: Flavio Pinamonti , Giorgio Nicolini , Alessandro Dalpiaz ,Gino Stringari & Gianni Zorzi (1999) Compost use in viticulture: Effect onheavy metal levels in soil and plants, Communications in Soil Science and PlantAnalysis, 30:9-10, 1531-1549, DOI: 10.1080/00103629909370305

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COMMUN. SOIL SCI. PLANT ANAL., 30(9&10), 1531-1549 (1999)

Compost Use in Viticulture: Effect onHeavy Metal Levels in Soil and Plants

Flavio Pinamonti,1 Giorgio Nicolini, Alessandro Dalpiaz,Gino Stringari, and Gianni Zorzi

Istituto Agrario di San Michele all'Adige, via E. Mach 1, 1-38010 San Micheleall'Adige, Italy

ABSTRACT

The purpose of this study was to examine the long-term effect of compostapplication on the heavy metal content in soil, leaves, and fruit of grape (Vitisvinifera). Two types of compost were tested in a vineyard. One was compostwith a low heavy metal content, which was derived from sewage sludge andbark (SB compost). The other type was compost with a higher concentrationof metals, which was derived from municipal solid waste (MSW compost).For 6 years, the levels of zinc (Zn), copper (Cu), nickel (Ni), lead (Pb),cadmium (Cd), and chromium (Cr) in their total (aqua regia digestion), EDTA-extractable, and DTPA-extractable forms were monitored in soil, leaves,musts, and wines. The resulting data clearly demonstrate that SB compostdid not cause any significant increase in heavy metal levels in the soil and theplants. Thus, this type of compost can be used for soil fertilization with nodanger either to the environment or to crops. In contrast, the use of MSWcompost caused a significant accumulation of Ni, Pb, Cd, and Cr in the soil,

1Corresponding author (e-mail address: [email protected]).

1531

Copyright © 1999 by Marcel Dekker, Inc. www.dekker.com

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1532 PINAMONTIET AL.

in vegetation, and in musts. Skin-contact fermentation dramatically decreasedthe heavy metal content of the wines. The concentration of heavy metals inplant tissues was found to be positively correlated with the DTPA-extractableform of the metals in the soil, but not correlated with the total or the EDTA-extractable forms.

INTRODUCTION

The latest disposal laws passed by European countries offer incentives forselected collection of wastes into dry and wet fractions, as well as for thecomposting of the separately collected organic fractions. Thus, the production ofcompost is destined to increase substantially in the near future. For example, it isestimated that compost production in Italy will double (from 300,000 to 600,000tons per year) by the year 2000 (Zorzi et al., 1997). Even though the compostmarket is quite diversified and also involves non-agricultural uses such as gardeningand environmental recovery, the principal use of compost is still as a fertilizer intraditional full-field agriculture (USEPA, 1994; Garcia et al., 1995). Indeed, theuse of organic supplements remains an essential procedure in a valid agriculturalmodel offering a balance between the withdrawal of organic material from thebiosphere and its replacement (Press et al., 1996; Sequi et al., 1996), as well as thegradual restoration of organic material in agricultural soils. Many studies haveshown that the fertilizing power of compost is due to its content of stabilizedorganic matter and the amount of nutritive elements contained therein. An increasein soil organic matter and nutrient availability after compost application has beenobserved by many (Ferreira and Cruz, 1992; Bevacqua and Mellano, 1993;McConnel et al., 1993; Paino et al., 1996; Wen et al., 1997).

The use of compost is also beneficial to the physical properties of the soil.Such use has been shown to result in increased porosity, greater structural stability,ahigher content of available water and reduced erosion (Guidi et al., 1988; Ballifetal., 1991; He etal., 1992).

The phytonutritive capacity of compost has often been demonstrated to beanalogous to that of manure, since the same level of productivity both quantitativeand qualitative is reached when manure is replaced by compost (Del Zan, 1989;Beyea et al., 1993; Roe et al., 1993; Baldoni et al., 1994; Maynard, 1996; Abad-Berj6n et al., 1997). However, the principal factor that limits the agricultural useof compost is represented by the environmental and health risks associated withthe content of heavy metals in some composts. For this reason, many Europeancountries are gradually reducing the maximum levels of heavy metals allowed incompost (Accotto, 1996), and the US Environmental Protection Agency constantlymonitors heavy metal content to establish maximum cumulative loading rates forvarious types of soils (USEPA, 1993). Literature on the effect of compost use onenvironmental heavy metal levels shows it to vary according to soil type, plantspecies, and compost quality (Giusquinani et al., 1992; Woodbury, 1992).

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COMPOST USE IN VITICULTURE 1533

Increased Zn, Cu, and Pb levels have often been detected in the soil and plants,whereas other heavy metals, such as Cd, Ni, and Cr, are less consistently increased(Woodbury, 1992; Bevacqua and Mellano, 1993; Baldoni et al., 1994; Businelliand Gigliotti, 1994; Paino et al., 1996; Murillo et al., 1997).

In the long term, the use of sewage sludge can also cause a significantaccumulation of Zn, Cu, Pb, Ni, and Cd in soil and plants (Williams et al., 1980;Mulchi et al., 1991; McGrath and Cegarra, 1992; El-Demerdashe et al., 1995;Miner et al., 1997; Sloan et al., 1997). However, it has been shown that thecomposting process reduces the bio-availability of heavy metals contained in sludgeby favoring the formation of metal-humus complexes (Garcia et al., 1995;Pinamonti et al., 1997a).

Many studies indicate that the data necessary for proving the usefulness ofcompost as an organic fertilizer can be obtained only by conducting exhaustiveanalyses and experiments in specific areas and on specific crops. These testsmust also be aimed at evaluating the environmental impact of compost use bycarefully analyzing the behavior of the heavy metals which the compost contains(Shiralipour et al., 1992). To this end, the Istituto Agrario di San Michele all 'Adigedevised an experiment that examined the use of compost on grapevines. In Italy,grapevines are cultivated over a surface area of approximately one million hectares,and grapevine cultivation represents a particularly broad application of compostuse since the vines are often grown on hilly terrain with relatively infertile soilsthat contain little organic matter (Scienza et al., 1986; Carre, 1995).

According to recent studies, compost can be usefully applied in viticulture asmulching material, to increase soil fertility, to reduce rain and erosion damage ofsoils, to control weeds, to improve water balance, and to reduce large fluctuationsin soil temperature (Ballif, 1990;Ballifetal., 1991; Pinamonti etal., 1996). Thus,the authors decided to observe the effects of two types of compost (a relativelyclean compost and one which was strongly contaminated with heavy metals) whenused as mulching material and to compare their effects with more traditionaltechniques of managing soil in the rows. The goals were to monitor the effect ofcompost mulch on soil fertility and plant nutrition as well as to study the effect ofcompost on heavy metal content in soil and plants, since heavy metals arepotentially strong pollutants. In the study reported herein, our attention was limitedto heavy metals. For information on the agronomic aspects of compost use, seethe authors'previous publications (Pinamonti etal., 1991,1995,1996). The resultsof a similar test conducted on apple trees have appeared in this journal (Pinamontietal., 1997b).

MATERIALS AND METHODS

The trial was started in Spring 1991 on a Merlot vineyard, situated at the bottomof the Adige Valley (240 m ASL) on a minor slope (10%) with a southwestexposure. The calcareous soil, classified as Typic Udorthents (USDA, 1988), is

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1534 PINAMONTIET AL.

TABLE 1. Physical and chemical properties of thesoil before the start of the trial (1991).

Fraction >2mm(%)Sand 2000-20 urn (%)Silt 20-2 urn (%)Clay<2um(%)pH-H,0CaC0,(%DM)Organic matter (% DM)N-KjeIdhal(%DM)C/NP-Olsen (mg kg1 DM)CEC (cmol+ kg1)Kex.(mgkg'DM)Mgex.(mgkg'DM)Cacx.(mgkg'DM)totalZn(mgkg'DM)total Cu (mg kg1 DM)total Ni (mg kg*' DM)total Pb (mg kg" DM)total Cd(mgkg-'DM)total Cr (mg kg"1 DM)

28.260.529.010.57.7037.82.250.149.3210.015.3125186

19801021949.2111<3

17.5

Analytical methods, GU (1992).

formed from dolomitic limestone parent material and has a medium-sandy texturewith stones (Table 1). The heavy metals content of the soil is well within theaccepted normal range of values (Adriano, 1986; Abollino et al., 1996). Thevineyard, planted in April 1991 with a spacing of 2.0x1.0 m, is grafted on 3309Couderc and trained with a guyot system.

The experiment entailed the use of two composts as mulching materials: 1) SBcompost—produced at the Trento plant through the treatment of a mixture ofurban waste water purification sludge and poplar bark (ratio 1:2 vol/vol) and 2)MSW compost—from the Schio (Vicenza) plant from the composting of theorganic fraction of unseparated municipal solid waste, mechanically selected atthe plant.

These two different composts were used because they were representative ofthe two types of compost produced in Italy at the present time; organic wasteobtained from separated waste collection with the possible addition of sewagesludge occurs in 69 facilities (Zorzi et al., 1997); unseparated municipal solidwaste treatment occurs in 42 facilities (Zorzi et al., 1995). The mean analyticalcharacteristics of the two composts used in the trial are listed in Table 2.

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COMPOST USE IN VITICULTURE

TABLE 2. Analytical characteristics of the composts used.

1535

Moisture (%)pH-H2O(l/5)Ash(%DM)Organic matter (% DM)C/NN-Kjeldahl(%DM)P A (%DM)K2O (%DM)total Zn (mg kg1 DM)total Cu (mg kg'1 DM)total Ni (mg kg ' DM)total Pb (mg kg1 DM)total Cd (mg kg1 DM)total Cr (mg kg1 DM)

SB Compost

199154.07.4535.461.418.61.911.650.47

4991352073

1.0042

199451.17.4846.751.518.41.621.930.61

54112621

1041.37

61

MSW Compost

1991.37.17.8230.863.422.21.660.660.7012124111666981.75328

199433.37.6526.661.228.91.230.440.699865101376323.20271

Italian standard

Law 748/1984<50<8.5

>43<25

-

-<500<150<50

< 140<1.5

-Analytical methods, IPLA (1992).

The trial design was a randomized block of three treatments repeated four times.Each plot consisted of 108 m2 with three rows for a total of 54 vines. The threetreatments were 1) Control: mechanical cultivation in the first year and chemicalweed control with glyphosate in the following years (two sprayings per year); 2)SB: a 5-cm thick layer of SB compost was applied immediately after vine plantingand reapplied again in Spring 1994, the quantity of compost applied during eachapplication was 631 ha1 ; and 3) MSW: a 5-cm thick layer of MSW compost wasapplied immediately after vine planting and reapplied again in Spring 1994, thequantity of compost applied during each application was 541 ha"1.

The control plots were fertilized yearly with 500 kg ha 1 of an N-P-K fertilizerwhich supplied 60 kg N ha1 , 37 kg P ha1 , and 71 kg K ha 1 . This treatmentrepresents a typical fertilization procedure practiced in the Province of Trento.Soil treated with compost mulch received no fertilizer. The two applications ofSB compost supplied a total of 1,051 kg ha 1 of organic N, 467 kg P ha1 , and 269kg K ha"1. The two applications of MSW compost supplied a total of 1,007 kg ha 1

of organic N, 1 6 8 k g P h a 1 , a n d 4 0 4 k g K h a 1 . The main farming operations werecarried out in the same way in all the plots: grass covering on the alleys (betweenthe rows); sprinkler irrigation; phytosanitary treatments to meet the normal cropprotection requirements. A mixture of Lolium perenne var. Elka (40%), Festucarubra var. Dawson (30%) and Poapratensis var. Baron (30%) was sown on thealleys in Spring 1991 (50 kg ha1) .

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1536 PINAMONTIETAL.

The levels of Zn, Cu, Ni, Pb, Cd, and Cr in the soils, leaves, and musts weremonitored in all the plots beginning with the third year after the vineyard wasplanted. Soil samples were taken from the Ap horizon at a depth of 10-30 cm inOctober of the years 1993, 1994,1995, and 1996. During these same years, leafsamples were taken at veraison, in the middle of August, and samples of mustwere collected at harvest-time. The leaf samples were taken according to theprocedure described by Martin-Prevel et al. (1987).

In 1994 and 1996, the heavy metal content was measured also in samples ofwines obtained from all the plots. Sixty kg of grapes from each plot were processedwith crushing-destemming, sulphating (50 mg L"1), yeasting (20 g hi1 of selectedyeast), 7-day skin contact and 10 punching of the cap, wash pressing (at 3.5 bar),free-run and press-wine collected simultaneously, spontaneous malolacticfermentation, filtration and bottling. To prevent the heavy metal content of thewines from being altered, no fining product (bentonite, charcoal, etc.) was added.During processing, the wines were stored in stainless steel tanks or glass tanks.

Soil analyses were carried out following the methods known in Italy as theMetodi ufficiali di anal is i del suolo (GU, 1992). The composts were analyzedusing IPLA methods (1992). The "total" content of heavy metals in the soil andin the composts was determined by digestion in boiling aqua regia (3:1 HNO3 :HC1),and extractions with 0.05 A/EDTA (ethylene-diamine-tetraacetic-acid) and 0.005M DTPA (diethylene-triamine-pentaacetic-acid) were carried out to obtain theEDTA-extractable and DTPA-extractable fractions. The Zn, Cu, Ni, Cd, and Crlevels in the resulting solutions were determined by inductively coupled plasma(ICP) emission spectrometry, and Pb was measured by atomic absorptionspectrometry (AAS) during flaming. For the analysis of leaves, musts, and wines,the heavy metals were dissolved in 2 N HNO, after the organic matter was ashedin a muffle furnace at 480°C (Martin-Prevel et al., 1987). Zinc and Cu weremeasured by ICP emission spectrometry, and the other metals were measured byAAS using a graphite furnace. The ANOVA and CORRELATION proceduresand the Duncan Test on the Statistical Analysis System package (SAS, 1995)were used to perform a statistical analysis on the data.

RESULTS AND DISCUSSION

To simplify presentation and discussion of the results, means are calculated fordata obtained during 1993-1996 trial period (Tables 3-9). None of the treatmentsexamined had any significant influence on the pH (H2O) of the soil. The meanvalues were as follows: control=7.73, SB=7.75, MSW=7.68. However, the useof either type of compost did lead to a significant increase in the content of organicmatter as compared with the control, organic matter content was 2.47% in theControl, 2.92% in SB and 2.88% in MSW treated-plots.

The heavy metal content of the two composts differed considerably (Table 2).The concentration of each heavy metal examined was higher in MSW compost

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TABLE 3. Mean (1993-1996) total heavy metals concentration in soil, as affectedby the different treatments.

Treatment

ControlSBMSWSig.FAccounted variability quote (%)YearTreatmentsBlocksYear x TreatmentsError

Metal concentration, mg kg'1 DM

Zn106 b116 b136 a

•*

4.045.80.29.1

40.9

Cu217222233

ns

13.91.1

12.25.8

69.0

Ni9.0 b9.1b

13.0 a•*

5.650.43.5

14.227.3

Pb108 b107 b127 a

• •

4.450.14.1

13.927.5

Cd< 3< 3< 3

ns

00000

Cr18.6 b19.4 b29.9 a

• •

6.746.38.8

15.123.1

*, **, ns=significant with P<0.05, <0.01, and not significant, respectively.Means followed by the same letter or no letter are not statistically different

(Duncan's Multiple Range Test, P<0.05).

than in the SB composts and even exceeded the Italian standards (GU, 1984; GU,1998). On the other hand, the concentrations of heavy metals in SB composts wasbelow legal limits, with a single exception: the quantity of Zn in the SB compostapplied in 1994 slightly exceeded the limit of 500 mg kg1 DM.

Heavy Metals in the Soil

Copper content was quite high as a direct result of the numerous fungicidetreatments which had been carried out using products containing this metal. In

TABLE 4. Heavy metal natural presence in the soil (0-30 cm) beforethe treatments and heavy metal amounts introduced by the differenttreatments.

Natural presenceAmounts addedControlSBMSW

Zn295.8

031.176.7

MeCu

562.6

07.8

32.4

talpreseNi

26.68

01.23

10.57

nee, kglPb

321.9

05.3

46.5

ia''Cd2.90

00.070.18

Cr50.75

03.09

21.00

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1538 PINAMONTIETAL.

TABLE 5. Mean (1993-1996) EDTA extractable heavy metals content in soil, asaffected by the different treatments.

Treatment


Zn31.2 b38.5 b51.4 a

**

5.740.95.3

12.835.3

Metal concentration, mg kg'' DM

Cu133136134ns

25.50.10.31.8

72.3

Ni1.05 b1.08 b1.47 a

•*

6.440.48.5

11.233.5

Pb19.2 b19.7 b26.4 a

•*

1.462.35.0

12.718.6

Cd0.25 b0.24 b0.36 a

* •

4.240.37.7

15.532.3

!

Cr0.34 b0.38 b0.57 a

»•

0.442.714.82.0

40.1

*, **, ns=significant with P<0.05, <0.01 and not significant, respectively.Means followed by the same letter or no letter are not statistically different (Duncan's

Multiple Range Test, P<0.05).

viticulture, these products release an annual quantity of 15 to 20 kg Cu ha"1. Becauseviticulture has been practiced for centuries in this type of soil, its total Cu contenthas risen from an original value of approximately 30 to 50 mg kg"1 DM due toparent materials (Corradini et al., 1989) to 200 mg kg"1 DM. In any event, thedifferent compost treatments under study did not affect total Cu content or thecontent of EDTA-extractable Cu (Tables 3 and 5). Both types of compost, on theother hand, brought about a significant decrease in DTPA-extractable Cu (Table6). This result can be attributed to an increase in the content of organic matter inthe soil and to the increased stability of the Cu-humus complexes.

With regard to the total Cd content in the soil, since it was always below theanalytical sensitivity (3 mg kg"1 DM), no considerations can be drawn.

Application of SB compost resulted in slight increases in the various forms ofZn in the soil; however, increases were significant only for the DTPA-extractableform of Zn. With regard to the various forms of the other heavy metals considered(Tables 3, 5, and 6), application of SB compost did not result in significantdifferences compared with the control.

Application of MS W compost, on the other hand, resulted in significant increasesin the concentrations of the total, EDTA-extractable, and DTPA-extractable formsof all the metals. The effects of the various treatments studied on the total levelsof heavy metals in the soil may be related to the actual amounts of individualelements introduced by the different soil conditioners (Table 4). In fact, theincreases measured in the soil analyses correspond to the increases which can be

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TABLE 6. Mean (1993-1996) DTPA extractable heavy metals content in soil, as affectedby the different treatments.

Treatment


Zn11.9 c14.6 b18.6 a

*»

18.030.117.35.7

28.9

Metal concentration, mg kg"' DM

Cu75.161.863.0

*

12.525.66.45.3

50.2

Ni0.31b0.31b0.48 a

**

4.850.07.6

12.125.5

Pb4.62 b4.55 b8.41a

• *

4.143.18.7

15.228.9

Cd0.080 b0.087 b0.132 a

**

7.350.33.8

14.124.5

Cr0.022 b0.022 b0.030 a

**

8.932.613.814.030.7



expected after application of such soil conditioners. These results seem to confirmthat all of these heavy metals remain immobile on the surface of calcareous sub-alkaline soil (Emmerich etal., 1982;Giusquinanietal., 1992). The MSW compostcontributed a far greater amount of all the heavy metals examined and broughtabout significant increases in the content of their total forms in the soil.

For MSW compost, the percentage increase of Zn and Pb over the control washigher for the EDTA-extractable and DTPA-extractable forms than for the totalform. For example, MSW treatment resulted in a 65% increase in EDTA-extractable Zn and a 28% increase in total Zn, as well as an 82% increase inDTPA-extractable Pb and an 18% increase in total Pb. Unlike treatment with SBcompost, which did not significantly affect the quantities of these metals, theapplication of MSW compost led to a significant increase in the extractability ofthe metals from the soil (the ratio of the EDTA-extractable and DTPA-extractableforms to the total form). This result highlights the difference between the twocomposts in quantitative and qualitative terms. The application of MSW compostresulted in a redistribution of the heavy metals (especially those with greatermobility) among the various chemical forms present in the soil.

Variance analysis reveals how the effects of compost treatment can explain thehigher levels of variability for the various forms of all the metals, except in thecase of Cu. Even the levels of variability explained by the interaction of year-x-treatment proved to be quite large for all the chemical forms of the metals and, inany case, were always higher than the levels of variability explained by the year

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1540 PINAMONTIETAL.

TABLE 7. Mean (1993-1996) heavy metals concentration in vine leaves, as affectedby the different treatments.

Treatment


Zn25.926.726.5

ns

69.21.80.41.0

27.6

Metal concentration, mg kg'1 DM

Cu276264279

ns

95.90.20.90.42.6

Ni0.99 b1.00 b1.42 a

*«

53.114.84.66.1

21.4

Pb2.22 b2.18 b2.96 a

**

58.015.08.24.6

14.2

Cd0.050 b0.051 b0.078 a

» •

66.617.4

1.93.8

10.3

Cr0.47 b0.52 ab0.59 a

**

63.710.15.90.8

19.5



effect. This result must be considered in relation to the diverse behavior of thethree treatments under study: the control and the SB composts did not result inany significant trend over time, while MSW treatment brought about a sharp trendof increasing values over the years under study (data not shown). Thus, based onthe results obtained in the trial, it can safely be concluded that when MSW compostis repeatedly applied over time, heavy metals tend to accumulate in the soil, bothin their total forms and in their extractable forms.

Heavy Metal Content in Leaves and Musts

The various treatments did not affect the levels of Zn and Cu in the leaves(Table 7) and musts (Table 8). With regard to Cu, this result can be attributed thefact that the Cu content in the underlying soil was unvaried, as mentioned above.The content of Zn in the plants, on the other hand, was unchanged even whensignificant increases were measured in the soil. This result conflicts with theinformation commonly found in the literature (Woodbury, 1992; Paino et al.,1996; Murillo et al., 1997), which highlights the ease with which plants accumulateZn. The discrepancy may be explained by the fact that numerous Zn-basedfungicide treatments were applied, which may have masked additional Znaccumulation in the leaves and musts. Indeed, in the normal practice of growinggrapevines, 2 to 3 kgZn ha"1 are distributed annually on the foliage to protect thecrops.

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TABLE 8. Mean (1993-1996) heavy metals concentration in musts, as affected by thedifferent treatments.

Treatment


Zn0.380.410.39

ns

80.42.00.71.7

15.2

Metal concentration,

Cu4.744.65S.08

ns

53.12.18.60.1

36.1

Ni0.047 b0.048 b0.065 a

**

76.08.60.92.2

12.3

Pb0.058 b0.060 b0.086 a

**

68.111.71.04.1

15.1

ing I1

Cd0.012 b0.009 b0.017 a

**

70.311.14.06.08.6

•

Cr0.053 b0.047 b0.084 a

»•

50.119.62.66.1

21.6



It clearly emerged that application of SB compost did not bring about anysignificant variation in the accumulation of Ni, Pb, Cd, and Cr by the grapevine;this compost had no effect on the transfer of these metals from the soil into thegrowth systems of the plants (Tables 7 and 8). Application of MSW compost, onthe other hand, did bring about significant variations in the quantities of these 4metals in the epigeous organs. After MSW compost was applied, there was asignificant increase in Ni and Cr, which are generally described as having limitedmobility and are thus are difficult to assimilate (Dean and Suess, 1985; Petruzzelliet al., 1989), in the leaves and the musts. Furthermore, MSW compost markedlyenriched the soil in EDTA-extractable and DTPA-extractable Cd and Pb, so theiraccumulation by the plants greatly increased. This finding amply confirms theevidence found in the literature on Cd, which is believed to be the heavy metalthat presents the greatest danger to human health. The metal has no biologicalfunction and is readily absorbed by plants, where it accumulates (Davis et al.,1983; Dean and Suess, 1987; Korcak, 1989; Cieslinski et al., 1995,1996a, 1996b;Oliver, 1997).

An examination of the data produced by variance analysis highlights the factthat, unlike what was found for the soil, the effect of the year is responsible for therather high levels of variability that were found. In other words, the uptake ofheavy metals by grapevines was more strongly influenced by climatic trends duringthe various years than by the effective presence of the metals in the soil, aphenomenon which was also observed for the absorption of macroelements (Failla

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1542 PINAMONTIETAL.

TABLE 9. Mean (1993-1996) heavy metals concentration in wines, as affected by thedifferent treatments.

Treatment

ControlSBMSWSig.FAccounted variability quote (%)YearTreatmentsBlocksYear x TreatmentsErrorItalian standard(Law 29/12/86)Standard CSHPF. 1996

Zn0.400.370.37

ns

60.21.01.75.5

32.6

< 5-

Metal concentration.

Cu0.0760.0700.073

ns

64.40.64.15.0

25.9

< 1-

Ni0.0190.0260.021

ns

14.36.62.2

14.562.4

--

Pb0.0240.0200.023

ns

26.64.28.13.5

57.6

<0.30<0.25

mgl '

Cd0.00150.00160.0016

ns

10.510.41.6

17.260.3

-<0.02

Cr0.0210.0220.021

ns

27.30.8

10.28.5

53.2

--



et al., 1992). Furthermore, in the case of the leaves and musts, the levels ofvariability due to the interaction of year with treatment always proved to be low,and no interference whatsoever was demonstrated between these two factors. Thus,it may be concluded that although the application of MSW compost results in asignificant increase in the concentration of heavy metals in leaves and musts, noclear trend in this regard occurs over time; that is, the increases recorded after 3years were of the same magnitude as those recorded after 6 years (data not shown).

Heavy Metal Content in the Wines

None of the treatments studied had a statistically significant influence on theamount of heavy metals contained in the wines (Table 9). Vinification of redwine sharply reduced the levels of all the heavy metals found in the musts (98%for Cu, 58% for Ni, 66% for Cr, 68% for Pb, 88% for Cd), with the exception ofZn. A skin-contact effect that reduces the level of Cu (but is ineffective on Zn)has been observed in other studies (Nicolini et al., 1996). Biological absorptionof heavy metals by yeast biomasses having sequestering mechanisms that aredifferent for live and dead Saccharomyces cerevisiae cells has been reported(Volesky and May-Phillips, 1995). In any event, the content of heavy metals inthe wines obtained during the experimental trial was much lower than both the

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TABLE 10. Simple correlation indices between the heavy metal content in soil, leavesand fruit.

Soil "total" x Leaves

Soil EDTA x Leaves

Soil DTP A x Leaves

Soil "total" x Musts

Soil EDTA x Musts

Soil DTPA x Musts

Zn

-0.06 ns

0.17 ns

0.24 ns

-0.03 ns

0.21ns

0.25 ns

Cu

0.29 ns

-0.23 ns

0.09 ns

0.18 ns

-0.24 ns

-0.08 ns

Ni

0.32 ns

•0.14 ns

0.52 ••

0.14 ns

0.18 ns

0.33 ns

Pb

0.32 ns

0.31ns

0.40*

0.32 ns

0.24 ns

0.42 •*

Cd

0.09 ns

0.52 •*

0.06 ns

0.36*

Cr

0.29 ns

0.08 ns

0.39*

0.27 ns

0.28 ns

0.48 **

*, **, ns=significant with P<0.05, <0.01 and not significant, respectively.

legal limits in Italy and the values set by the Direction Generate de la Sante inFrance (CSHPF, 1996).

Correlation Between the Concentrations of Heavy Metals in Soil, Leaves,and Musts

Certain observations must be made regarding the correlations that were notedbetween the forms of the metals present in the soil and their concentrations in theplants. To this end, simple correlation indices were calculated between theconcentration of each metal (in the "total", EDTA-extractable and DTPA-extractable forms) in the soil, leaves and musts (Table 10).

No significant correlation emerged between the various chemical forms of Znand Cu in the soil and their concentrations in the epigeous organs. This fact canbe explained by the numerous treatments applied for improving plant health, whichuse materials containing Zn and Cu in their active ingredients. These treatmentsmay have masked possible variations due to the modified concentrations of thetwo elements in the soil.

With regard to the other four heavy metals, it was found that the quantities ofthe "total" and EDTA-extractable forms were not significantly correlated withtheir effective assimilation by the plants. Although the total and EDTA-extractableforms proved to be suitable for quantifying the environmental impact of compostswith different levels of contamination by heavy metals, they were not effectivefor determining the actual levels of heavy metals that were accumulated by theplants. For this purpose, a milder extractant such as DTPA may be more suitable(Mulchi et al., 1991; Miner etal., 1997). In fact, higher indices of correlation thatare statistically significant have been obtained between DTPA-extractable Ni,Pb, Cd, and Cr and their concentrations in plant tissues. Recent work (Houba etal., 1996) has shown that CaCl2 extracts only those forms of the metal that are

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1544 PINAMONTIETAL.

actually available to the plant, and can provide information that is more useful fordetermining the environmental threat posed by metals introduced by composts.Finally, it must be noted that the absorption of nutritional elements and heavymetals by plants is more strongly influenced by the chemical characteristics ofthe terrain, pH, CEC, organic matter, and by seasonal trends (Woodbury, 1992;Miner et al., 1997, Oliver, 1997) than by the external addition of the elements andheavy metals, such as through the use of compost.

CONCLUSIONS

This experiment clearly demonstrates that the use of municipal solid waste(MSW) compost over a six-year period increased the concentrations of Ni, Pb,Cd, and Cr in soils, grapevine leaves, and musts. However, no symptoms ofphytotoxicity from these metals were observed in the trial. The plant concentrationsof Zn and Cu, on the other hand, was greatly influenced by treatments that arenormally applied as fungicides. Since sewage sludge and bark (SB) compostcontains a much smaller amount of heavy metals than MSW compost, use of SBcompost over a six-year period resulted in significant increases only in DTPA-extractable Zn in the soil and did not lead to any variations in concentrations ofother heavy metals examined. Thus, SB compost can be considered to be a validalternative to traditional commercial soil conditioners (manure). If this type ofcompost is high quality, it safeguards the environment and promotes healthy crops.

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