261 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 (montmorillonite, 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 4131/frame/C13 Page 261 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 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 (pH KCl , 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: pH KCl : 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: pH KCl : 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 HNO 3 /H 2 O 2 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 cm 3 of 0.01 M CaCl 2 or Lakanen- Erviö solution (0.02 M H 4 EDTA in ammonium acetate buffer, pH 4.65), respectively. To extract “total” amount of heavy metals 2-g samples were digested with cc. HNO 3 and H 2 O 2 (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 clinoptilolite [clinoptilolite 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/cm 3 , wet surface pH: 7.8, NH 4 + -ion exchange capacity: 118 meq/100 g, Ag + -ion binding capacity: 177 meq/100 g. The 4131/frame/C13 Page 262 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 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/cm 3 , wet surface pH: 7, NH 4 + -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/cm 3 , wet surface pH: 5-6, NH 4 + -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. foliosum Hegi, cv. Wild) to study the phytoavailability of heavy metals in the galvanic mud 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. Experiment 1 : Chicory was grown in uncontaminated basic soil mixed (or replaced) with 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. HNO 3 and H 2 O 2 (3:1 v/v) prior to elemental analysis. The experiment was done between February and April 1995. Experiment 2 : Chicory was grown in uncontaminated soil or in heavy metal-contaminated 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 CaCl 2 , EDTA in ammonium acetate buffer, or cc. HNO 3 and H 2 O 2 (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. 4131/frame/C13 Page 263 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 264 Environmental Restoration of Metals–Contaminated Soils 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. uncontaminated 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 cc. HNO 3 –H 2 O 2 extracts, Nyíregyháza, Hungary, 1995) Element ( µ g/g) Cd Cr Cu Ni Zn Uncontaminated soil 0.3 12.2 15.0 14.9 41.0 Contaminated soil 10.1* 228.5* 119.0* 56.2* 107.0* Note: Student’s t-test. Data are means of three replications. Statistically significant at * P <0.001 level. 4131/frame/C13 Page 264 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC Effects of Natural Zeolite and Bentonite on the Phytoavailability of Heavy Metals in Chicory 265 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 Heavy metal contaminated soil (%) Heavy metal contaminated soil (%) 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 Cadmium (µg/g) 10 8 6 4 2 0 0 20 40 60 80 100 Cadmium (µg/g) Heavy metal contaminated soil (%) 20 18 16 14 12 10 8 6 4 2 0 0 20 40 60 80 100 Heavy metal contaminated soil (%) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 20 40 60 80 100 Chromium (µg/g) Chromium (µg/g) 4131/frame/C13 Page 265 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 266 Environmental Restoration of Metals–Contaminated Soils 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 Heavy metal contaminated soil (%) Copper (µg/g) 50 45 40 35 30 25 20 15 10 5 0 0 20 40 60 80 100 Heavy metal contaminated soil (%) Copper (µg/g) 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 Heavy metal contaminated soil (%) Zinc (µg/g) ROOT and RHIZOME Linear regression: 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 X 80 70 60 50 40 30 20 10 0 0 20 40 60 80 100 Heavy metal contaminated soil (%) Zinc (µg/g) SHOOT Linear regression: y=32.3+0.2x R=0.80 SD=6.33 P<0.05 X X X X X X X X X X 4131/frame/C13 Page 266 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC Effects of Natural Zeolite and Bentonite on the Phytoavailability of Heavy Metals in Chicory 267 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 Cd Cr Cu Ni Zn µg/g Extractant CaCl 2 Uncontaminated soil <0.01 <0.01 0.07 <0.01 <0.01 Contaminated soil 0.10* <0.01 0.20* 0.14* <0.01 Extractant H 4 EDTA in ammonium acetate buffer (Lakanen-Erviö) Uncontaminated soil 0.6 0.9 8.6 0.9 14.7 Contaminated soil 48.9* 36.7* 93.7* 25.0* 77.7* Extractant cc. HNO 3 – H 2 O 2 Uncontaminated soil 0.9 28.3 17.4 19.9 55.7 Contaminated soil 53.5* 327.3* 125.0* 95.3* 139.7* Note: Student’s t-test. Data are means of 3 replications. Statistically significant at * P <0.05 level. 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 20 40 60 80 100 Heavy metal-contaminated soil (%) Nickel (µg/g) ROOT and RHIZOME Linear regression: 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 (%) Nickel (µg/g) SHOOT Linear regression: y=1.16+0.005x R=0.55 SD=0.33 P<0.26 4131/frame/C13 Page 267 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 268 Environmental Restoration of Metals–Contaminated Soils 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 Root and rhizome Shoot (g/plant) Uncontaminated soil (1) 0.12 0.42 Contaminated soil (2) 0.13 ns 0.39 ns 2 + 5% RBZ clinoptilolite 0.10 ns 0.39 ns 2 + 5% MHZ mordenite 0.17 ns 0.39 ns 2 + 5% MSC clinoptilolite with H-montmorillonite 0.10 ns 0.38 ns 2 + 5% MHB montmorillonite (bentonite) 0.16 ns 0.38 ns Note: Student’s t-test. Data are means of six replications. 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 Cd Cr Cu Ni Zn ( µ g/g) Root and Rhizome 1 1.4 6.1 17.3 4.2 43.8 2 27.6 109.7 59.5 11.0 43.9 3 25.3 79.5 48.5 8.6 27.1 x 3 23.1 90.9 53.7 9.0 30.2 5 21.1 66.5 38.6 17.4 32.7 x 6 22.3 92.3 50.0 8.2 28.9* Shoot 1 2.0 1.8 9.3 2.2 29.9 2 40.8 5.2 13.2 4.0 34.9 3 39.7 4.6 13.4 3.8 36.2 4 43.1 3.0 13.3 3.5 36.5 5 41.0 3.6 14.2 4.3 34.9 6 41.4 2.9 11.7 2.5 34.4 Note: 1: control uncontaminated soil 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 x P <0.1. * P <0.05 level as compared to treatment 2. 4131/frame/C13 Page 268 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC Effects of Natural Zeolite and Bentonite on the Phytoavailability of Heavy Metals in Chicory 269 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 (CaCl 2 extractable) Zn content in the contaminated soil. “Plant available” (Lakanen-Erviö solution extractable) or “total” (cc. HNO 3 – H 2 O 2 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 Cd Cr Cu Ni Zn ( µ g/g) Extractant CaCl 2 1 <0.01 <0.03 0.05 <0.02 <0.01 2 <0.01 <0.03 0.1 <0.02 0.05 3 <0.01 <0.03 0.23* <0.02 <0.01* 4 <0.01 <0.03 0.24* <0.02 <0.01* 5 <0.01 <0.03 0.08 <0.02 <0.01* 6 <0.01 <0.03 0.03* <0.02 <0.01* Extractant H 4 EDTA in ammonium acetate buffer (Lakanen-Erviö) 1 0.3 0.1 9.7 2.3 9.8 2 35.7 11.0 68 15.2 41.2 3 33.0 11.8* 68 16.6* 41.9 4 32.9 11.8* 68 16.0* 41.9 5 32.6 12.0* 74* 16.2* 43.2 6 32.4 11.5* 68 15.2 40.9 Extractant cc. HNO 3 – H 2 O 2 1 1.1 21.9 17.6 16.9 47.3 2 35.5 218 103 90 112 3 33.4 218 103 91 116 4 36.8 241* 113* 98 119 5 35.0 223 126* 91 116 6 37.0 230 105 87 108 Note: 1: control uncontaminated soil 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. 4131/frame/C13 Page 269 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 270 Environmental Restoration of Metals–Contaminated Soils 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 Adriano, D.C., Trace Elements in the Terrestrial Environment , Springer-Verlag, New York, 1986, 1–95. Alloway, B.J., Ed., Heavy Metals in Soils , Blackie & Son, Ltd., Glasgow and London, 1990, 29–39. Baidina, N.L., The use of zeolites as heavy metal absorbents in technogenically contaminated soils (in Russian), Izvestiya Sibirskogo Otdeleniya Akademii Nauk SSSR. , Seriya Biologicheskikh Nauk, 6, 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. 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Pollution, 91, 351, 1996 Shanableh, A and A Kharabsheh, Stabilization of Cd, Ni, and Pb in soil using natural zeolite, Journal of Hazardous Material, 45, 207, 1996 Statistix 4.0, User’s Manual, Analytical Software, St Paul, MN, 1992 © 2001 by CRC Press LLC . treatment 2. 4131 /frame/C13 Page 269 Friday, July 21, 2000 4:48 PM © 2001 by CRC Press LLC 270 Environmental Restoration of Metals–Contaminated Soils 13. 4 Conclusions The soil of a kitchen. 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. medium-hard microporous zeolite. Composition: clinoptilolite ≈ 50%, mordenite 0-1 0%, altered volcanic glass 2 0-3 0%, montmorillonite 1 0-1 5%, quartz 0-5 %, feldspar 0-5 %, and limonite 1-2 %.