The effect of lead incorporation on the elemental composition of earthworm (Annelida,Oligochaeta) chloragosome granules

Summary The elemental compositions of chloragosome granules in the earthworm Lumbricus rubellus living in non-polluted (Dinas Powys) and heavily Pb-polluted (Wemyss) soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. High Pb concentrations were found in chloragosomes of Wemyss animals; Pb was not detected in chloragosomes of Dinas Powys animals. Partial correlation and regression analysis indicated that the in vivo accumulation of Pb by chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Pb is bound by P-containing ligand(s) in the chloragosome matrix. The sequestration of Pb by chloragosomes results in the detoxification of the metal by accumulative immobilization.     

The distribution of cadmium,copper, lead,zinc and calcium in the tissues of the earthworm Lumbricus rubellus sampled from one uncontaminated and four polluted soils

Summary The tissue distribution of Cu, Cd, Pb, Zn, and Ca in the earthworm Lumbricus rubellus living in non-polluted and heavy-metal polluted soils was investigated. Cd, Pb and Zn were primarily accumulated within the posterior alimentary canal. As the whole-worm Pb burden increased, the proportion of the metal accumulated within this tissue fraction increased. A similar pattern was found for Zn. By contrast, 70%–76% of the Cd burden was found in the posterior alimentary canal, irrespective of the whole-worm Cd content. The accumulation of Cd, Pb and Zn primarily in the posterior alimentary canal prevents dissemination of large concentrations of these metals into other earthworm tissues, and may thus represent a dextoxification strategy based on accumulative immobilisation. Cu was distributed fairly evenly in the tissue fractions investigated. There was no evidence of sequestration of this metal. The apparent lack of a detoxification strategy may contribute to the well-known susceptibility of earthworms to low environmental Cu concentrations. Indeed, earthworms from the site of highest soil Cu (Ecton) were markedly smaller than those from the other sites sampled. The highest Ca concentrations were found in the anterior alimentary canal, and were related to calciferous gland activity. A large proportion of Ca was also stored as a physiologically available pool in the posterior alimentary canal. Despite huge variations in soil Ca concentrations, the body wall Ca levels were fairly similar in L. rubellus from all the study sites. Thus, L. rubellus may become physiologically adapted to soils of exceptionally low Ca concentration. The observations are discussed in the context of the merits of analysing specific tissues, rather than whole organisms, for the purpose of monitoring metal bioaccumulation.     

Zinc sequestration by earthworm (Annelida: Oligochaeta) chloragocytes

Summary The elemental compositions of chloragosome granules in the earthworm Lumbricus rubellus living in non-polluted and heavily Zn-polluted soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. The in vivo accumulation of Zn by the chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Zn was apparently bound by at least two ligand pools (Pool 1=uncharacterised; Pool 2=P-containing ligands, binding approximately 45% and 55% of the Zn, respectively) in the control chloragosomes. In Zn-contaminated chloragosomes, most (70%) was bound by P-containing ligand(s) but some (<1%) was also bound by S-containing ligands. It is suggested that the sequestration of Zn in chloragosomes results in the detoxification of the metal by accumulative immobilisation.     

The effect of lead incorporation on the elemental composition of earthworm (Annelida, Oligochaeta) chloragosome granules

The elemental compositions of chloragosome 'granules' in the earthworm Lumbricus rubellus living in non-polluted (Dinas Powys) and heavily Pb-polluted (Wemyss) soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. High Pb concentrations were found in chloragosomes of Wemyss animals; Pb was not detected in chloragosomes of Dinas Powys animals. Partial correlation and regression analysis indicated that the in vivo accumulation of Pb by chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Pb is bound by P-containing ligand(s) in the chloragosome matrix. The sequestration of Pb by chloragosomes results in the detoxification of the metal by accumulative immobilization.     

Short-term and long-term effects of cadmium,chromium, copper,nickel, lead and zinc on soil microbial respiration in relation to abiotic soil factors

Summary The inhibition of the respiration rate by the heavy metals, Cd, Cr, Cu, Pb, Ni and Zn was investigated in five Dutch soil types in relation to the length of time these heavy metals were present in the soil. The amounts of heavy metal added as chloride salts to the soils were 0, 55, 150, 400, 1000, 3000 and 8000 g·g^–1, respectively. The measurements were carried out both immediately after the addition of the heavy metals and approximately 18 months later. The inhibition during the first two to eight weeks was not obscured by an extra nutrient flush to drying. During the 18 months, the toxicity decreased but was still significant. Inhibition was greatest in the sandy soil and least in the clay soil. In a loam soil and in a sandy peat soil, the inhibiting effects were intermediate, but distinct. The main abiotic factors responsible for these different degrees of inhibition were the clay fraction for Cd, the Fe content for Cu, Pb and Zn and the pH for Ni. Although clay, Fe, and Mn together with the organic matter fraction, determine the total cation exchange capacity of soil, their contribution to the toxicity of heavy metals may be antagonistic. The latter may increase the mobility due to chelation and therefore possibly increase the toxicity, while the other factors may bind the heavy metals and therefore decrease the toxicity.     

EFFECTS OF INOCULATION WITH ARBUSCULAR MYCORRHIZAL FUNGI ON MAIZE GROWN IN MULTI-METAL CONTAMINATED SOILS

Pot culture experiments were established to determine the effects of colonization by arbuscular mycorrhizal fungi (AMF) (Glomus mosseae and G. sp) on maize (Zea mays L.) grown in Pb, Zn, and Cd complex contaminated soils. AMF and non-AMF inoculated maize were grown in sterilized substrates and subjected to different soil heavy metal (Pb, Zn, Cd) concentrations. The root and shoot biomasses of inoculated maize were significantly higher than those of non-inoculated maize. Pb, Zn, and Cd concentrations in roots were significantly higher than those in shoots in both the inoculated and non-inoculated maize, indicating the heavy metals mostly accumulated in the roots of maize. The translocation rates of Pb, Zn, and Cd from roots to shoots were not significantly difference between inoculated and non-inoculated maize. However, at high soil heavy metal concentrations, Pb, Zn, and Cd in the shoots and Pb in the roots of inoculated maize were significantly reduced by about 50% compared to the non-inoculated maize. These results indicated that AMF could promote maize growth and decrease the uptake of these heavy metals at higher soil concentrations, thus protecting their hosts from the toxicity of heavy metals in Pb, Zn, and Cd complex contaminated soils.     

Leaching of Zinc,Cadmium, and Lead in a Sandy Soil Due to Application of Poultry Litter

Dissolved organic matter in poultry litter could contribute organic ligands to form complexes with heavy metals in soil. The soluble complexes with heavy metals can be transported downward and possibly deteriorate groundwater quality. To better understand metal mobilization by soluble organic ligands in poultry litter, soil columns were employed to investigate the movement of zinc (Zn), cadmium (Cd), and lead (Pb). Uncontaminated soil was amended with Zn, Cd, and Pb at rates of 400, 8, and 200 mg kg ^{? 1} soil, respectively. Glass tubes, 4.9-cm-diameter and 40-cm-long, were packed with either natural or metal-amended soil. The resulting 20-cm-long column of soils had bulk density of about 1.58 g cm ^{? 3} . Columns repacked with natural or amended soil were leached with distilled water, 0.01 M EDTA, 0.01 M CaCl ₂ , or poultry litter extract (PLE) solutions. Low amounts of Zn, Cd, and Pb were leached from natural soil with the solutions. Leaching of Zn, Cd, or Pb was negligible with distilled water. In the metal-amended soil, EDTA solubilized more Zn, Cd, and Pb than CaCl ₂ and PLE. The breakthrough curves of Zn and Pb in the PLE and CaCl ₂ were similar, indicating they have similar ability to displace Zn and Pb from soils. Compared with Zn and Cd the PLE had a small ability to solubilize Pb from metal-amended soil. Thus, the application of poultry litter on metal-contaminated soils might enhance the mobility of Zn and Cd.     

Response of ectomycorrhizalPinus banksiana andPicea glauca to heavy metals in soil

Pinus banksiana andPicea glauca inoculated or not with the ectomycorrhizal fungusSuillus luteus were grown in a sandy loam soil containing a range of Cd, Cu, Ni, Pb and Zn concentrations. Ectomycorrhizal colonization rates were significantly reduced on Pinus and Picea seedlings by the heavy metals, particularly Cd and Ni. Needle tissue metal concentrations were lower in ectomycorrhizal seedlings at low soil metal concentrations. However, at higher soil concentrations, heavy metal concentrations of needle tissue were similar in ectomycorrhizal and nonmycorrhizal plants. The growth of nonmycorrhizal seedlings exposed to heavy metals was reduced compared to those inoculated withSuillus luteus. Apparently ectomycorrhizal colonization can protect Pinus and Picea seedlings from heavy metal toxicity at low or intermediate soil concentrations of Cd, Cu, Ni, Pb and Zn.     

Effects of toxic heavy metals (Cd,Pb) on growth and mineral nutrition of beech (Fagus sylvatica L.)

The beech (Fagus sylvatica L.) is the dominant tree in Middle Europe under many different ecological conditions. But like other tree species, it is suffering in the last ten years increasingly by air pollutants including heavy metals which have been deposited and accumulated for decades in many forest soils. Increasingly mobilized by acidification processes, these metals may have toxic effects on trees.In autecological studies (dose-response-experiments) effects of root-applied Pb and Cd on various growth parameters, on uptake of mineral nutrients and on transpiration of young beech trees were evaluated, and critical concentrations (threshold levels) could be established. Significant leaf area reduction was found with 6 ppm Pb (0.3 ppm Cd) in the leaves (DW), but biomass reduction only with 18 ppm Pb (3.6 ppm Cd). Root elongation rates of seedlings were significantly reduced with 44 ppm plant-available Pb in the soil by about 30%, but only with 24 ppm Pb when combined with 2 ppm Cd, exhibiting synergistic effects. After treatments with 20 ppm Pb and 1 ppm Cd in sand culture, a considerable decrease in the contents of K, Ca, Mg, Fe, Mn, and Zn in roots and leaves of saplings was coincident with high (roots) and moderate (leaves) accumulation of Pb and Cd. A 20% reduction of transpiration rates was measured in ten-year-old beech trees after three months of exposure to a forest soil containing 2.5 ppm plant-available Cd.The data indicate that present-day concentrations mainly of Pb, but not yet of Cd, in acidified European forest soils are sufficiently high to affect germination, growth and mineral nutrition of natural rejuvenation of beech.The data published here are part of a doctoral and of various diploma theses: Mrs. Christiane Bertels, Barbara Buschmann, Martina Hücker, Gritli Noack, Ute Röder, Swantje von Oy and Mr. Rüdiger Ahrend, Peter Rüther and Frank Weisser.     

The use of indigenous plant species and calcium phosphate for the stabilization of highly metal-polluted sites in southern Poland

Highly metal-polluted (Pb, Cd, Zn) soil from a non-ferrous mine and smelter site in southern Poland, further referred to as Waryski soil, was used to test indigenous plant species for stabilization effectiveness of heavy metals in soils. Results of pilot investigations with commercially available cultivars of plant species showed that these cultivars could not grow on this highly polluted soil even with the application of soil amendments to stabilize the heavy metals. Based on these results, mesocosm and field experiments with an indigenous, metal-tolerant ecotype of Deschampsia cespitosa from the Waryñski site were carried out. The mesocosm experiment showed that applications of calcium phosphate (3.8% w/w) as a heavy metal-stabilizing amendment decreased Cd and Zn concentrations 2 and 3-fold respectively in leachates, whereas lead content was not significantly changed. This decrease in the concentration of heavy metals in leachates was correlated with a lower accumulation of Pb, Cd and Zn in the roots and shoots of D. cespitosa, ecotype Waryñski. In the field experiment, lower accumulations of Cd in roots and shoots and Zn in shoots in the amendment added plot were observed during the second year of investigations. In the first growing season, D. cespitosa plant cover in the amendment enriched mesocosms ranged from 95 to 100%, compared to 10% in mesocosms without calcium phosphate. In the second year of the experiment, in non-amendment enriched mesocosms D. cespitosa was substituted with Cardaminopsis arenosa(95% cover). C. arenosa is an undesirable species for phytostabilization, as it accumulates high amounts of zinc and cadmium in its shoots, even thought it provided better growth cover in not amended soils. However, in amended mesocosms, soil surface cover by D. cespitosa was still very high (90%). Similar results were obtained in field experiments. Addition of calcium phosphate to the soil also resulted in excellent D. cespitosa root system development when compared to soils without amendment. In amended mesocosms, high plant cover and root system development significantly decreased the volume of leachates and improved water retention. These results indicate that the use of D. cespitosa, ecotype Waryski in combination with calcium phosphate as a heavy metals immobilizing agent is sufficient to restore a dense vegetative cover to highly heavy metal-polluted soil.     

新疆焉耆盆地辣椒地土壤重金属污染及生态风险预警

从新疆加工辣椒主产地(焉耆盆地)采集105个辣椒地典型土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量。采用污染负荷指数(Pollution load index,PLI)、潜在生态风险指数(Potential ecological risk index,RI)和生态风险预警指数(Ecological risk warning index,I_(ER))对辣椒地土壤重金属污染及生态风险进行评价。结果表明:(1)焉耆盆地辣椒地土壤Cd、Cr、Ni、Pb和Zn含量的平均值分别超出新疆灌耕土背景值的1.65、1.40、1.32、3.21、6.42倍。辣椒地土壤Pb和Zn呈现重度污染,Cd、Cr和Ni轻度污染,As、Mn和Cu无污染。(2)土壤PLI平均值为1.40,呈现轻度污染。各重金属元素单项生态风险指数从大到小依次为:Cd、Ni、As、Cu、Pb、Cr、Zn。土壤RI平均值为18.40,属于轻微生态风险态势,IER平均值为-4.78,属于无警态势;博湖县辣椒地污染水平、潜在生态风险程度与生态风险预警等级最高,焉耆县污染水平、潜在生态风险程度与生态风险预警等级最低。(3)辣椒地土壤As、Cd、Pb与Zn主要受到人类活动的影响,Cr、Cu、Mn和Ni主要受到土壤地球化学作用的控制。Cd是焉耆盆地辣椒地生态风险等级最高的重金属元素,研究区农业生产过程中要防范Cd的污染风险。     

土壤重金属污染对蚯蚓的急性毒性效应研究

测定了草甸棕壤条件下 ,Cu、Zn、Pb、Cd单一 /复合污染对蚯蚓的急性致死及亚致死效应 .结果表明 ,Cu、Pb浓度与蚯蚓死亡率显著相关 (α=0 .0 5 ,RCu=0 .86 ,RPb=0 .87) ,Cu浓度与生长抑制率显著相关 (α=0 .0 5 ,RCu=0 .84) ,其他供试重金属浓度与蚯蚓死亡率和生长抑制率相关性不显著 .蚯蚓个体对重金属毒性的耐受程度差别较大 .其毒性阈值 (引起个体蚯蚓死亡浓度 )分别为 :Cu 30 0mg·kg-1,Zn 130 0mg·kg-1,Pb 170 0mg·kg-1,Cd 30 0mg·kg-1.LC50 分别为 :Cu 40 0～ 45 0mg·kg-1,Zn15 0 0～ 190 0mg·kg-1,Pb2 35 0～ 2 40 0mg·kg-1,Cd 90 0mg·kg-1.在Cu、Zn、Pb、Cd单一污染引起 >10 %蚯蚓死亡的浓度下 ,复合污染导致 10 0 %蚯蚓死亡 ,表明复合污染极强的协同效应 .     

Heavy metal contamination in vegetables grown around peri-urban and urban-industrial clusters in Ghaziabad,India

Heavy metal contamination of agricultural soils resulting from rapid industrialization and urbanization is of great concern because of potential health risk due to dietary intake of contaminated vegetables. The present study aims to evaluate the status of heavy metals contamination of agricultural soils and food crops around an urban-industrial region in India. Transfer factor values of Cu, Cr, Pb, Cd, Zn, and Ni from soil to vegetable was estimated. The mean heavy metal concentrations (mg/kg) in agricultural soils (Cu: 17.8, Cr: 27.3, Pb: 29.8, Cd: 0.43, Zn: 87, Mn: 306.6, Fe: 16984, and Ni: 53.8) were within allowable concentrations for Indian agricultural soil. The concentrations of Pb, Cd, Zn, and Ni in crops/vegetables exceeded the World Health Organization/Food and Agriculture Organization safe limits. Relative orders of transfer of metals from soil to edible parts of the crops/vegetables were Cd > Pb > Ni > Zn > Cu > Cr. The enrichment factors of heavy metals in soil indicated minor to moderately severe enrichment for Pb, Cd, and Ni; minor to moderate enrichment for Zn; no enrichment to minor enrichment for Mn; and no enrichment to moderate enrichment for Cu at different sites. Ecological risk index of soil showed considerable contamination in one of the wastewater irrigated sites.     

Accumulation and subcellular distribution of heavy metal in Paulownia fortunei cultivated in lead-zinc slag amended with peat

Abstract

The contamination of toxic heavy metals was a major issue of concern in the last century. A fast-growing metal-accumulating woody plant is a promising approach for the remediation of toxic heavy metal. In this study, the transportation of heavy metals (Pb, Zn, Cu, and Cd) in Paulownia fortunei cultivated in lead-zinc slag amended with different mass ratios of peat (CK: 0; T1: 10%; T2: 20%; T3: 30%) was investigated, as well as the subcellular distribution of Pb, Zn, Cu, and Cd in Paulownia fortunei. The results showed that the accumulation content of Pb, Zn, Cu, and Cd in Paulownia fortunei were increased with peat amendment, which was in the range of 4.216?～?6.853, 20.905?～?23.017, 1.898?～?2.572, and 0.530?～?0.616?mg/pot, respectivly. The experimental group with 30% dose of peat showed the best performance on the accumulation content of Pb, Zn, Cu, and Cd, with increase rates (compared to control) of 4.088, 10.573, 1.360, and 0.294?mg/pot, respectively. The bioconcentration, translocation and transfer quantity factor of Pb, Zn, Cu, and Cd were less than 1. Fixation of cell wall and compartmentalization of vacuolar appeared to play an important role in reducing the toxicity of Pb, Zn, Cu, and Cd.     

Molecular rearrangements of thylakoids after heavy metal poisoning, as seen by Fourier transform infrared (FTIR) and electron spin resonance (ESR) spectroscopy

The specific effects exerted by different heavy metals on both the function and the structure of the photosynthetic apparatus were addressed. The functional analysis performed via the fluorescence induction kinetics revealed that the applied toxic heavy metals can be classified into two groups: Cd and Ni had no significant effect on the photosynthetic electron transport, while Cu, Pb and Zn strongly inhibited the Photosystem II (PS II) activity, as evidenced by the dramatic decreases in both the variable (F_v) and the maximal (F_m) fluorescence. The structural effects of the heavy metal ions on the thylakoid membranes were considered in three relations: (1) lipids, (2) proteins — studied by Fourier transform infrared (FTIR) spectroscopy, and (3) lipid—protein interactions — investigated by electron spin resonance (ESR) spectroscopy using spin-labeled probe molecules. The studied heavy metal ions had only a non-specific rigidifying effect on the thylakoid lipids. As regards proteins, Cd and Ni had no effect on the course of their heat denaturation. The heat denaturation of the proteins was accompanied by a decrease in the -helix content (1656 cm^-1), a parallel increase in the disordered segments (1651 cm^-1), a decrease in the intramolecular -sheet (1636 cm^-1) content and the concomitant appearance of an intermolecular -structure (1621 cm^-1). In contrast with Cd and Ni, Cu and Zn blocked the appearance of the intermolecular -structure. Pb represented an intermediate case. It seems that these heavy metals alter the native membrane structure in such a way that heat-induced aggregation becomes more limited. The ESR data revealed that certain heavy metals also affect the lipid—protein interactions. While Cd and Ni had hardly any effect on the solvation fraction of thylakoid lipids, Cu, Pb and Zn increased the fraction of lipids solvating the proteins. On the basis of the FTIR and ESR data, it seems that Cu, Pb, and Zn increase the surfaces available for lipid—protein interactions by dissociating membrane protein complexes, and that these lipidated proteins have a smaller chance to aggregate upon heat denaturation. The data presented here indicate that the damaging effects of poisonous heavy metals are element-specific, Cu, Pb and Zn interact directly with the thylakoid membranes of the photosynthetic apparatus, while Cd and Ni interfere rather with other metabolic processes of plants.     

Soil Heavy Metal Pollution Assessment Near the Largest Landfill of China

To assess the extent and potential hazards of heavy metal pollution at Shanghai Laogang Landfill, the largest landfill in China, surface soil samples were collected near the landfill and concentrations of Cu, Zn, Cd, Pb, and Cr were determined. The results revealed that the concentrations of heavy metals, except Pb, were higher in the surface soil near the landfill than in the background soil. Principal component analysis and hierarchical cluster analysis suggested that the enrichment of Cu in soil was probably related to agricultural activities and Cd and Pb to landfill leachates, whereas Zn and Cr concentrations were probably controlled by soil matrix characteristics. The pollution indices (PIs) of the metals were: Cd > Cu > Cr > Zn > Pb. Among the five measured metals, Cd showed the largest toxic response and might cause higher ecological hazards than other metals. The integrated potential eco-risk index (RI) of the five metals ranged from 26.0 to 104.9, suggesting a low-level eco-risk potential. This study indicated the accumulations of Cu, Zn, Cd, Pb, and Cr did not reach high pollution levels, and therefore posed a low eco-risk potential in surface soil near the landfill.     

Heavy-metal accumulation in crops grown on sewage sludge amended with metal salts

Poplar (Populus euramericana Robusta), oats (Avena sativa L. Leander), maize (Zea mays L. Ona 36), English ryegrass (Lolium perenne L.), butter head lettuce (Lactuca sativa L. Reskia), spinach (Spinacia oleracea L. Subito) and French beans (Phaseolus vulgaris Prelude), were grown in pots with pure sewage sludge (pH 6.7), amended with Cd, Cr, Cu, Ni, Pb and Zn acetates, either added singly or in combination, to study metal effects on plant growth and metal uptake. Phytotoxic metal doses varied with metal and plant species, increasing in the order Cd<Ni<Cu<Zn<Cr and Pb. The threshold dose of toxic metals applied in combination was generally lower than that of metals given singly. Addition of Cd, Ni and Zn was clearly reflected in the respective plant concentrations. This was much less so for Cu, whereas Cr and Pb concentrations were not affected in most plant species. Critical plant (leaf) metal concentrations were lower for metals applied in combination than for single metals. Because of such phenomena the use of critical levels as a diagnostic tool for determining potential multiple metal toxicity is limited.     

Metals and phosphate in the chloragosomes of Lumbricus terrestris and their possible physiological significance

Summary The chloragog cells of the earthworm Lumbricus terrestris contain numerous granules, chloragosomes, which were analyzed for metals and phosphate by histochemistry, by use of an electron microscope X-ray microprobe (EMMA), and by chemical analysis of chloragosome preparations. Inorganic and organic phosphate each accounts for about 3% of the chloragosome dry mass, Ca for 2–3%, Zn for 1–3% and Mg for 0.2–0.4%. Carbonate is not present in chloragosomes. The average molar ratios CaMgZntotal PO₄ are 10.10.31. The CaPO₄ ratio is fairly constant (correlation coefficient 0.99), while the ZnPO₄ ratio varies considerably. It is concluded that Ca is bound in the form of inorganic CaHPO₄ and organic ROPO ₃Ca (or possibly Ca-polyphosphate complexes). Mg may also be phosphate-bound, while Zn probably is not. Chemical analysis of the calciferous glands revealed a high concentration of Ca, small amounts of Mg and phosphate, but no Zn. It is concluded that Zn is not excreted through the calciferous gland.Storage of Ca in the chloragocytes and excretion of CaCO₃ by the calciferous gland may be physiologically linked. Regulation of the concentrations of Ca and HCO₃ ^–ions in the blood and coelomic fluid may assist in equalization of osmotic pressures during dehydration and rehydration. This regulation may be a major function of the chloragosomes.The chloragosomes were discussed in relation to the spherites of various arthropods and molluscs and to the cytosomes of anoxia-tolerating molluscs.I wish to thank Theodore A. Hall for the use of the EMMA-4 microprobe facility, T.C. Norrnann for help in performing the microprobe analysis, Bruno Hansen for the improved zinc determination method and Annette Prentø for performing the chemical analyses. This work was supported by the Danish Natural Science Research Council (grant 511-3522). The EMMA-4 facility is supported by a grant from the British Science Research Council     

Risk Element (As,Cd, Cu,Pb, and Zn) Contamination of Soils and Edible Vegetables in the Vicinity of Guixi Smelter,South China

Risk element (As, Cd, Cu, Pb, and Zn) contamination in soils and in two edible vegetables (Solanum melongena L. and Capsicum annum L.) was investigated in the vicinity of Guixi Smelter, South China. Soil As concentrations averaged 23.9 mg/kg. Sites near the smelter tailings recorded the highest levels of As and heavy metals in soils. The concentration order of heavy metals in soils was Cd < Pb < Zn < Cu. Cu and Cd in soils were abundant in the exchangeable and bound to carbonate fraction, while Pb and Zn were in the residual fraction, limiting their potential toxicity as pollutants. The proportions of the metals in the mobile fraction followed the order Pb < Zn < Cu < Cd. In Solanum melongena L. and Capsicum annum L., Zn concentration was the highest, followed by Cu, Cd, and Pb, different from that in soils and in the mobile fraction. Concentrations of heavy metals in the labile fractions in soils and in vegetables presented significant correlation (p < 0.05). Both of the two vegetables are not the Cu and Zn accumulators. As for Cd and As, Capsicum annum L. poses a higher risk to animal and human health than Solanum melongena L., with soil-plant transfer coefficients more than three. Root-stem is the main barrier for most of the heavy metals and As in the two vegetables, resulting in higher metal concentrations in roots relative to other plant tissues. The low stem-fruit transfer coefficients for Zn in Solanum melongena L. and for Pb in Capsicum annum L. suggested that very few of them could reach the fruits.     

Effects of Cadmium,Chromium and Lead on Growth,Metal Uptake and Antioxidative Capacity in <Emphasis Type="Italic">Typha angustifolia</Emphasis>

This study investigates the modulation of antioxidant defence system of Typha angustifolia after 30 days exposure of 1 mM chromium (Cr), cadmium (Cd), or lead (Pb). T. angustifolia showed high tolerance to heavy metal toxicity with no visual toxic symptom when exposed to metal stress, and Cd/Pb addition also increased plant height and biomass especially in Pb treatment. Along with increased Cr, Cd, and Pb uptake in metal treatments, there was enhanced uptake of plant nutrients including Ca and Fe, and Zn in Pb treatment. A significant increase in malondialdehyde (MDA) content and superoxide dismutase (SOD) and peroxidase (POD) activities were recorded in plants subjected to Cr, Cd, or Pb stress. Furthermore, Pb stress also improved catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX) activities; whereas Cr stress depressed APX and GPX. The results indicate that enzymatic antioxidants and Ca/Fe uptake were important for heavy metal detoxification in T. angustifolia, stimulated antioxidative enzymes, and Ca, Fe, and Zn uptake could partially explain its hyper-Pb tolerance.