ENVIRONMENTAL RESTORATION of METALSCONTAMINATED SOILS - CHAPTER 13 potx

Considering the above facts the objectives of our study were to evaluate 1 concentration of heavy metals in a soil contaminated with galvanic mud, 2 phytoavailability, transport, and dis

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13

Effects of Natural Zeolite and Bentonite on the Phytoavailability of Heavy Metals in Chicory

László Simon

CONTENTS

13.1 Introduction 261

13.2 Materials and Methods 262

13.2.1 Soil Sample Collection and Characterization 262

13.2.2 Characterization of Natural Zeolites and Bentonite Used in the Experiment 262

13.2.3 Growth Chamber Pot Experiments with Chicory 263

13.2.4 Elemental Analysis of Soil and Plant Samples 264

13.2.5 Statistics 264

13.3 Results and Discussion 264

13.3.1 Phytoavailability of Heavy Metals in a Galvanic Mud-Contaminated Soil 264

13.3.2 Immobilization of Heavy Metals with Natural Zeolites and Bentonite 265

13.4 Conclusions 270

Acknowledgments 270

References 270

13.1 Introduction

Clay minerals have high cation sorption and cation exchange capacity and large surface area (Adriano, 1986; Alloway, 1990; Kabata-Pendias and Pendias, 1992) Natural and syn-thetic zeolites (sodium aluminum calcium silicates) have high affinity to sorb and to com-plex trace elements, particularly heavy metals (Mineyev et al., 1990; Baidina, 1991; Gworek,

1992, 1994; Obukhov and Plekhanova, 1995; Chlopecka and Adriano, 1996; Shanableh and Kharabsheh, 1996) and caesium (Campbell and Davies, 1997) Similar properties of bento-nite (montmorillobento-nite, sodium aluminum magnesium hydrosilicate) were observed by Krebs and Gupta (1994) Besides other soil additives (e.g., lime, phosphate, apatite, iron oxide, manganese oxide, organic matter) natural zeolites and bentonites have the potenti-ality of immobilizing heavy metals in contaminated soils and of preventing their accumu-lation in agricultural plants (Mench et al., 1998)

During recent decades the environmental consequences of industrialization were neglected in Hungary In many cases the environmental pollution was not revealed, e.g., the contamination of kitchen garden soil with heavy metals in the neighborhood of a former galvanization plant in the city of Nyíregyháza (Northeastern Hungary) was discovered only

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262 Environmental Restoration of Metals–Contaminated Soils

in 1991 The transition to a market economy is pressing a clean-up of the most critical con-taminated sites of the country The Hungarian government therefore initiated a new envi-ronmental remediation program in 1996 Hungary is rich in natural zeolites and bentonites, therefore these relatively cheap clay minerals may play an important role in the soil remedi-ation program

Considering the above facts the objectives of our study were to evaluate (1) concentration

of heavy metals in a soil contaminated with galvanic mud, (2) phytoavailability, transport, and distribution of heavy metals in chicory plant grown in this contaminated soil, (3) heavy metal immobilization capacity of three different natural zeolites and a bentonite with the help of chicory indicator plant

13.2 Materials and Methods 13.2.1 Soil Sample Collection and Characterization

The uncontaminated (control) soil used in this experiment originated from the demonstra-tion garden of College of Agriculture, Nyíregyháza The soil samples contaminated with heavy metals were collected in a kitchen garden located near a former galvanization plant (Nyíregyháza, Vasgyár Street) Several basic characteristics of the soils (pHKCl, clay + silt [<0.02 mm particles] content, organic matter %, cation exchange capacity [CEC], macro-element concentrations) were determined according to Hungarian standards Basic charac-teristics of the uncontaminated soil used in the experiment were the following: pHKCl: 6.6; clay + silt content: 15.8%; organic matter: 1.3%; CEC: 18.1 meq/100 g, P 0.9 g/kg, K 4.3 g/kg,

Ca 34.3 g/kg, and Mg 7.6 g/kg The soil contaminated with heavy metals had the following basic properties: pHKCl: 6.8; clay + silt content: 16.0%; organic matter: 1.1%; CEC: 8.2 meq/100 g,

P 1.4 g/kg, K 2.4 g/kg, Ca 53.3 g/kg, and Mg 4.8 g/kg (all elements were determined in HNO3/H2O2 extracts) Both soils were slightly acidic loamy sands and had brown forest soil character

The plots were sampled with stainless steel gauge auger Two parallel soil samples were taken from 0 to 25 cm depth combining 20 subsamples After air drying the soil samples were screened on a 2-mm sieve To determine exchangeable or “plant available” fraction of heavy metals 5 g of soil samples were extracted with 50 cm3 of 0.01 M CaCl2 or Lakanen-Erviö solution (0.02 M H4EDTA in ammonium acetate buffer, pH 4.65), respectively To extract “total” amount of heavy metals 2-g samples were digested with cc HNO3 and H2O2 (3:1 v/v) prior to elemental analysis Samples were shaken for 2 h

13.2.2 Characterization of Natural Zeolites and Bentonite Used in the Experiment

Three different types of natural zeolites (RBZ clinoptilolitic rhyolite tuff, MHZ mordenite rhy-olite tuff, and MSC clay mixed clinoptilrhy-olite [clinoptilrhy-olite altogether with H-montmorillonite] and a bentonite (MHB montmorillonite) sample originated from Healing Minerals Geoproduct Ltd (Mád, Hungary) and were mined in Zemplén Hills, Hungary

The RBZ type is a medium-hard microporous zeolite Composition: clinoptilolite ≈50%, mordenite 0-10%, altered volcanic glass 20-30%, montmorillonite 10-15%, quartz 0-5%, feldspar 0-5%, and limonite 1-2% Characteristics: density ≈2.05 g/cm3, wet surface pH: 7.8,

NH4+-ion exchange capacity: 118 meq/100 g, Ag+-ion binding capacity: 177 meq/100 g The

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Effects of Natural Zeolite and Bentonite on the Phytoavailability of Heavy Metals in Chicory 263

MHZ type is a hard porous light zeolite Composition: mordenite 40-60%, altered volcanic glass 20-30%, montmorillonite 10-15%, quartz 0-5%, feldspar 0-5%, and limonite 1-2% Characteristics: density ≈1.82 g/cm3, wet surface pH: 7, NH4+-ion exchange capacity:

70 meq/100 g, Ag+-ion binding capacity: 176 meq/100 g The MSC type is a rare and worldwide unique soft zeolite formation The main components are clinoptilolite and H-montmorillonite which are present at the same ratio Characteristics: density ≈1.50 g/cm3, wet surface pH: 5-6, NH4+-ion exchange capacity: 65 meq/100 g, Ag+-ion binding capacity:

52 meq/100g The MHB type bentonite is a gray, wet, soft, and plastic clay It contains, besides calcium potassium montmorillonite, illite, crystoballite, kaolinite, and amorphous volcanic glass Physicochemical properties: swelling in water, absorption and ion-exchange of Na+-cations, tixotrophy, formation of stabile suspension-gel (characterization and analytical data are courtesy of Tibor Mátyás from Healing Minerals Geoproduct Ltd., Mád, Hungary)

13.2.3 Growth Chamber Pot Experiments with Chicory

Growth chamber pot experiments were conducted with chicory (Cichorium intybus L., var

contaminated soil (Experiment 1), and their immobilization with zeolites and a bentonite (Experiment 2) Larger amounts of uncontaminated and contaminated soil were collected during 1995 and 1996 as described above; the soils were air dried, homogenized, and screened on a 2-mm sieve before utilization

0, 10, 25, 50, 75, or 100% (m/m) of heavy metal contaminated soil (collected in 1995) in a growth chamber experiment A completely randomized experimental design with six replications was used In one plastic pot (16 cm diameter) with 1500 g of soil three uniformly sized 4-week-old seedlings were planted After 8 weeks of growth (temperature:

25 ± 2°C, illumination: 5000 lux for 8 h daily, watering: regularly with distilled water to maintain constant field capacity moisture content) the plants were harvested and separated into underground parts (roots and rhizomes) and shoots Plant samples were washed in tap water and rinsed in three-times-changed deionized water After the determination of dry weights (70°C, 14 h) the samples were ground (<1 mm) and digested with cc HNO3 and

H2O2 (3:1 v/v) prior to elemental analysis The experiment was done between February and April 1995

soil (collected in 1996) The heavy metal-contaminated soil was amended with 5% (m/m)

of three different types of zeolite (RBZ clinoptilolite; MHZ mordenite; MSC clinoptilolite altogether with H-montmorillonite) or MHB montmorillonite (bentonite), respectively The zeolite and bentonite samples were dried (105°C, 3 h), ground, and sieved The <0.25-mm fraction was thoroughly mixed with heavy metal-contaminated soil and moisturized with distilled water After 14 days of soil incubation three plants (6-week-old seedlings with three to five true leaves) were planted in one pot containing 1500 g of soil–zeolite/bentonite mixture All other growth conditions were as described in Experiment 1; the plants were processed after 8 weeks of growth After harvesting of plants the soil-zeolite/bentonite growth medium was sampled in three replicates from every pot The samples were sieved (<0.5 mm) to remove root debris, air dried, and extracted with CaCl2, EDTA in ammonium acetate buffer, or cc HNO3 and H2O2 (3:1 v/v) to determine the exchangeable, “plant available,” and “total” concentration of heavy metals in growth medium at the end of the experiment The experiment was done between February and June 1996

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13.2.4 Elemental Analysis of Soil and Plant Samples

The elemental composition of soil and plant samples was determined by the inductively coupled argon plasma emission spectrometry (ICAP, model Labtam 8440M, Australia) technique in triplicate at the Central Chemical Laboratory, Debrecen University of Agricul-tural Sciences, Debrecen, Hungary For validation of plant analysis CRM 281 rye grass (Commission of the European Communities, Community Bureau of Reference, Brussels) certified reference material was used

13.2.5 Statistics

Statistical analysis of the experimental data was done by Student’s t-test using Statistix 4.0 software (Statistix, 1992)

13.3 Results and Discussion

13.3.1 Phytoavailability of Heavy Metals in a Galvanic Mud-Contaminated Soil

Careless handling of galvanic mud resulted in contamination of the kitchen garden soil with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn) (Table 13.1) The heavy metal concentrations in the uncontaminated control soil were in common range The Cd, Cr, and Ni concentrations in the contaminated soil exceeded the Hungarian and international regulatory values (Kádár, 1995; Adriano, 1986; Alloway, 1990; Kabata-Pendias and Pendias, 1992) The regulatory limits for heavy metal concentrations in arable soils are

1 to 3 mg/kg for Cd, 75 to 100 mg/kg for Cr, 75 to 100 mg/kg for Cu, 50 mg/kg for Ni, and

200 to 300 mg/kg for Zn in Hungary, depending on soil properties (Kádár, 1995)

Chicory has been demonstrated as an indicator plant for Cd contamination in soils or nutrient solution (Simon et al., 1996), and chicory indicated the excess of Cd, Mn, and Zn

in municipal sewage sludge compost used as a soil amendment (Simon et al., 1997) This sensitive indicator plant was grown in the contaminated soil to study the phytoavailability, accumulation, and distribution of the above heavy metals With increasing ratio of the con-taminated soil vs unconcon-taminated soil, linearly increasing amounts of Cd, Cr, Cu, and Zn were detected in chicory roots and rhizomes and shoots (Figures 13.1 and 13.2)

Comparing the cadmium, chromium, copper, and zinc concentrations in roots and rhi-zomes with shoots a close correlation was found in their accumulation (Figures 13.1 and 13.2) It means that roots and rhizomes of this species do not act as a “barrier” against the accumulation of these trace metals in shoots This phenomenon could useful when chicory (cultivated or wild form) is used as a phytoindicator of heavy metal contamination in soils

TABLE 13.1

Heavy Metal Concentrations in Uncontaminated (Control) and Contaminated Soil (determined in

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The accumulation of nickel was negligible and its concentrations in chicory roots and rhizomes

or shoots did not reflect the level of soil contamination (Figure 13.3) Although 5 to 10 mg/kg

Cd, 1 to 2 mg/kg Cr or 15 to 20 mg/kg Cu in shoots may cause phytotoxicity in sensitive plant species (Kabata-Pendias and Pendias, 1992), no phytotoxicity symptoms were observed in chicory and the dry matter accumulation of plants was undisturbed (data not shown)

13.3.2 Immobilization of Heavy Metals with Natural Zeolites and Bentonite

Heavy metal concentrations in different extracts of the uncontaminated and contaminated soils are shown in Table 13.2 Elevated levels of heavy metals were detected in the

FIGURE 13.1

Cadmium and chromium accumulation in roots and rhizomes and in shoots of chicory grown in a galvanic mud-contaminated soil (pot experiment, Nyíregyháza, Hungary, 1995).

25

20

15

10

5

0

0 20 40 60 80 100

ROOT and RHIZOME Linear regression Y=0.07+0.16x R=0.99 SD=0.87 P<0.001

ROOT and RHIZOME Linear regression Y=0.45+0.016x R=0.98 SD=0.12 P<0.01

SHOOT Linear regression Y=0.25+0.06x R=0.99 SD=0.25 P<0.001

SHOOT Linear regression Y=4.2+0.09x R=0.81 SD=2.9 P<0.05

10

8

6

4

2

0

0 20 40 60 80 100

Heavy metal contaminated soil (%)

20

18

16

14

12

10

8

6

4

2

0

0 20 40 60 80 100

3.0

2.5

2.0

1.5

1.0

0.5

0.0

0 20 40 60 80 100

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exchangeable and “plant available” fractions of the contaminated soil; this predicts the danger of entering these heavy metals into the biosphere (Table 13 2) The heavy metal concen-trations were higher in samples collected in 1995 than in 1996 (compare Tables 13.1 and 13.2); this indicates the heterogeneity of soil contamination in the kitchen garden

Dry matter accumulation of chicory was unaffected by heavy metal contamination of the soil or by zeolite or bentonite treatment of this soil (Table 13.3) No visible phytotoxicity symptoms were observed The water absorption or macronutrient (P, K, Ca, Mg) uptake of plants was undisturbed by zeolite or bentonite application (data not shown)

FIGURE 13.2

Copper and zinc accumulation in roots and rhizomes and in shoots of chicory grown in a galvanic mud-contaminated soil (pot experiment, Nyíregyháza, Hungary, 1995).

24

22

20

18

16

14

12

10

8

6

4

2

0

0 20 40 60 80 100

50 45 40 35 30 25 20 15 10 5 0

0 20 40 60 80 100

ROOT and RHIZOME Linear regression:

y=10.2+0.07x R=0.98 SD=0.69 P<0.001

80

70

60

50

40

30

20

10

0

0 20 40 60 80 100

y=31+0.312x R=0.98 SD=2.93 P<0.001

SHOOT Lineat regression:

y=15.9+0.22x R=0.9 SD=4.7 P<0.05

X

80

70

60

50

40

30

20

10

0

0 20 40 60 80 100

SHOOT Linear regression:

y=32.3+0.2x R=0.80 SD=6.33 P<0.05

X

X X

X

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The zeolite and bentonite additives reduced the accumulation of zinc in chicory roots (Table 13.4) A slight reduction in Ni, Cr, and Cu accumulation was also observed in several cases but the rate of this has not proved to be statistically significant (Table 13.4) Consider-ing the heavy metal concentrations in the whole plants (roots and rhizomes + shoots) a sim-ilar tendency was observed; in the zeolite- or bentonite-treated cultures 16 to 25% less Cr,

Cu, and Zn was measured than in controls Observations of other authors based on similar pot experiments are controversial, indicating in most cases zinc immobilization by zeolites

in contaminated soils Baidina (1991) found that zeolite application decreased Zn and Pb

FIGURE 13.3

Nickel accumulation in roots and rhizomes and in shoots of chicory grown in a galvanic mud-contaminated soil (pot experiment, Nyíregyháza, Hungary, 1995).

TABLE 13.2

Heavy Metal Concentrations in Different Extracts of an Uncontaminated (Control) and Contaminated Soil in Nyíregyháza, Hungary, 1996

µg/g

3.0

2.5

2.0

1.5

1.0

0.5

0.0

0 20 40 60 80 100

Heavy metal-contaminated soil (%)

y=1.5+0.002x R=0.35 SD=0.23 P<0.48

4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

0 20 40 60 80 100

Heavy metal-contaminated soil (%)

SHOOT Linear regression:

y=1.16+0.005x R=0.55 SD=0.33 P<0.26

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mobility in a zinc-smelter contaminated soil, but heavy metal accumulation of beet was not diminished Mineyev et al (1990) found that natural zeolite decreased the concentration of mobile zinc in Zn, Cd, and Pb contaminated soil, but the negative effects of heavy metals were not reduced in barley In another pot study natural zeolite (clinoptilolite) significantly reduced the Zn concentration in maize and barley grown in soil artificially contaminated with Zn (Chlopecka and Adriano, 1996) Obukhov and Plekhanova (1995) got similar results; application of zeolite reduced the mobility of Pb and Zn in a contaminated soil, and their uptake in maize and barley Synthetic zeolite introduction to a contaminated soil reduced the Zn content of lettuce leaves by 36 to 65% (Gworek, 1994) In a sewage sludge

or heavy metal salts-contaminated soil, however, zeolite application had no effect on heavy

TABLE 13.3

Dry Matter Accumulation in Chicory Grown in Heavy-Metal Contaminated Soil Treated with Zeolite and Bentonite (pot experiment, Nyíregyháza, Hungary, 1996)

Treatment

(g/plant)

2 + 5% MSC clinoptilolite with H-montmorillonite 0.10 ns 0.38 ns

ns: Statistically not significant as compared to treatment 1.

TABLE 13.4

Heavy Metal Accumulation in Chicory Grown in Galvanic Mud-Contaminated Soil Treated with Zeolites and Bentonite (pot experiment, Nyíregyháza, Hungary, 1996)

Treatment

(µg/g) Root and Rhizome

Shoot

2: contaminated soil

3: 2 and 5% clinoptilolite

4: 2 and 5% mordenite

5: 2 and 5% clinoptilolite with H-montmorillonite

6: 2 and 5% montmorillonite (bentonite)

Student’s t-test Data are means of three replications Statistically significant at xP<0.1.

*P <0.05 level as compared to treatment 2.

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metal concentrations in chicory (Scotti et al., 1995) Sodium montmorillonite mixed with

zinc contaminated soil reduced zinc-concentration in plants without causing physiological

deficiency of this element (Krebs and Gupta, 1994)

In Table 13.5 heavy metal concentrations are shown in different extracts of zeolite or

bentonite-treated contaminated soil after 8 weeks of chicory growth Zeolite or bentonite

amendments significantly reduced the exchangeable (CaCl2 extractable) Zn content in the

contaminated soil “Plant available” (Lakanen-Erviö solution extractable) or “total”

(cc HNO3 – H2O2 extractable) concentrations of zinc, however, remained unaffected by

zeolite or bentonite application Since the exchangeable form of Zn in soil is considered as

the most bioavailable to plants (Kabata-Pendias and Pendias, 1992), the definitively lower

exchangeable Zn in zeolite or bentonite-treated soils may explain the lower Zn uptake in

chicory roots Our results confirm the findings of Chlopecka and Adriano (1996); zeolite

(clinoptilolite) ameliorant significantly reduced the exchangeable form of Zn in a flue

dust-contaminated soil, and Zn uptake in maize or barley test plants

TABLE 13.5

Heavy Metal Concentrations in Different Extracts of Uncontaminated (Control) Soil and of

Zeolite/Bentonite Treated Contaminated Soil after 8 Weeks of Chicory Growth (pot experiment,

Nyíregyháza, Hungary, 1996)

Treatments

(µg/g)

2: contaminated soil

3: 2 and 5% clinoptilolite

4: 2 and 5% mordenite

5: 2 and 5% clinoptilolite with H-montmorillonite

6: 2 and 5% montmorillonite (bentonite)

Student’s t-test Data are means of three replications.

Statistically significant at *P <0.05 level as compared to treatment 2.

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13.4 Conclusions

The soil of a kitchen garden located near a former galvanization plant was found to be

con-taminated with Cd, Cr, Ni, Cu, and Zn Chicory indicator plant grown in this soil

accumu-lated elevated levels of Cd, Zn, Cu, and Cr in its roots and rhizomes and in shoots Dry

matter accumulation of chicory was unaffected by heavy metal contamination of soil or by

zeolite or bentonite application Natural zeolites and bentonite reduced the accumulation

of Zn in chicory roots and rhizomes, and a slight decrease was also detected in Ni, Cr, and

Cu uptake of the test plants The decrease in Zn uptake of chicory may be related to

decrease in exchangeable (bioavailable) form of zinc in contaminated soil after zeolite or

bentonite application We plan open-field experiments with crop plants to study and verify

the long-term heavy metal immobilization effects of Hungarian natural zeolites and

bento-nites in contaminated soils

Acknowledgments

This research was supported by the Hungarian Scientific Research Fund (project F016906),

the Foundation for the Hungarian Higher Education and Research (project 681/96), and

Hungarian Soros Foundation Valuable help was provided by Prof Dr Zoltán Györi

(Central Chemical Laboratory, Debrecen University of Agricultural Sciences, Debrecen,

Hungary) and his co-workers, Drs József Prokisch and Béla Kovács, in elemental analysis

The help of Tibor Mátyás (Healing Minerals Geoproduct Ltd., Mád, Hungary) in zeolite

and bentonite characterization is gratefully acknowledged

References

Baidina, N.L., The use of zeolites as heavy metal absorbents in technogenically contaminated soils

32, 1991.

Campbell, L.S and B.E Davies, Experimental investigation of plant uptake of caesium from soils

amended with clinoptilolite and calcium carbonate, Plant and Soil, 189(1), 65, 1997.

Chlopecka, A and D.C Adriano, Mimicked in situ stabilization of metals in a cropped soil:

bioavail-ability and chemical form of zinc, Environmental Science and Technology, 30(11), 3294, 1996.

Gworek, B., Lead inactivation by zeolites, Plant and Soil, 143, 71, 1992.

Gworek, B., Zeolites of the 3A and 5A type as factors inactivating zinc in soils contaminated with

this metal, Roczniki Gleboznawcze, 44 (Suppl.), 95, 1994.

Kabata-Pendias, A and H Pendias, Trace Elements in Soils and Plants, CRC Press, Boca Raton, FL,

1992, 3–66.

Kádár, I., Contamination of the Soil-Plant-Animal-Man Food Chain with Chemical Elements in Hungary

(in Hungarian), KTM, MTA-TAKI, Budapest, 1995, 86–371.

Krebs, R and S.K Gupta, Mild remediation techniques for heavy metal contaminated soils

(in German), Agrarforschung, 1(8), 349, 1994.

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