Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

Cadmium accumulation and distribution in sunflower plant

Cadmium (Cd) accumulation and distribution was studied in sunflower (Helianthus annuus L., public line HA‐89) plant. From an uncontaminated sandy loam brown forest soil with 162 μg kg^‐1 HNO₃/H₂O₂ extractable Cd the HA‐89 sunflower public line accumulated 114 ug kg^‐1 Cd in its kernels under open field conditions. This value is rather low as compared to data found by others. Sandy loam brown forest soil was treated with 0, 1 or 10 mg kg^‐1 of Cd to study the interaction of this heavy metal with young sunflower plants in a greenhouse pot experiment. The fresh weight and dry matter accumulation of sunflower plant organs (roots, shoots, leaves or heads) was unaffected by cadmium treatment of soil. The nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), or zinc (Zn) uptake of sunflower plant organs was not influenced by lower or higher Cd‐doses, except sunflower heads where 10 mg kg^‐1 of Cd treatment of soil significantly reduced the uptake of Ca, Fe, and Mn. Although Cd reduced the Zn uptake of roots, its rate was statistically not significant. Cadmium was accumulated prevalently in roots (1.21 mg kg^‐1,4.97 mg kg^‐1, or 13.69 mg kg^‐1 depending on Cd‐dose), and its concentration increased also in shoots or leaves. In spite of the short interaction time, elevated concentrations of cadmium (0.78 mg kg^‐1, 1.34 mg kg^‐1, or 3.02 mg kg^‐1 depending on Cd‐dose) were detected in just emerged generative organs (heads) of young sunflower plants.     

Predicting heavy metal transfer from soil to plant: potential use of Freundlich‐type functions

Soil‐plant transfer of metals is a nonlinear process. We therefore aimed at evaluating the potential of Freundlich‐type functions (c_Plant = b × c_Soil^a) to predict Cd, Cu, Pb, and Zn concentrations in wheat (Triticum aestivum L.) grain and leaf (c_Plant) from soil concentrations (c_Soil). Wheat plants and soil A horizons, mainly developed from Holocene sediments, were sampled at 54 agricultural sites in Slovakia. Metals were extracted from soils with 0.025 M EDTA at pH 4.6 and concentrated HNO₃/HClO₄ (3:1); plant samples were digested with concentrated HNO₃. Total metal concentrations of soil samples were 0.07—25 mg Cd kg^—1, 9.3—220 mg Cu kg^—1, 14—1827 mg Pb kg^—1, and 34—1454 mg Zn kg^—1. On average, between 20 % (Zn) and 80 % (Cd) of the total concentrations were EDTA‐extractable. The total metal concentrations of grain samples were < 0.01—1.3 mg Cd kg^—1, 1.3—6.6 mg Cu kg^—1, < 0.05—0.30 mg Pb kg^—1, and 8—104 mg Zn kg^—1. The leaves contained up to 3.2 mg Cd kg^—1, 111 mg Cu kg^—1, 4.3 mg Pb kg^—1, and 177 mg Zn kg^—1. Linear regression without data transformation was precluded because of the nonnormal data distribution. The Freundlich‐type function was suitable to predict Cd (grain: r = 0.71, leaf: 0.86 for the log‐transformed data) and Zn concentrations (grain: 0.69, leaf: 0.68) in wheat grain and leaf from the EDTA‐extractable metal concentrations. The prediction of Cu and Pb concentrations in grain (Cu: r = 0.44, Pb: 0.41) was poorer and in leaf only possible for Pb (0.50). We suggest to use the Freundlich‐type function for defining threshold values instead of linear regression because it is more appropriate to simulate the nonlinear uptake processes and because it offers interpretation potential. The results suggest that the coefficient b of the Freundlich‐type function depends on the intensity of metal uptake, while the coefficient a reflects the plants' capability to control the heavy metal uptake. The latter is also sensitive to metal translocation in plants and atmospheric deposition.<?show $6#>     

Cadmium Uptake by Winter Wheat Seedlings in Response to Interactions Between Phosphorus and Zinc Supply in Soils

ABSTRACT

Effects of application of zinc (Zn) (0, 1, 5, 10 mg kg^?1 soil) and phosphorus (P) (0, 10, 50, 100 mg kg^?1 soil) on growth and cadmium (Cd) accumulations in shoots and roots of winter wheat (Triticum aestivum L.) seedlings were investigated in a pot experiment. All soils were supplied with a constant concentration of Cd (6 mg kg^?1 soil). Phosphorus application resulted in a pronounced increase in shoot and root biomass. Effects of Zn on plant growth were not as marked as those of P. High Zn (10 mg kg^?1) decreased the biomass of both shoots and roots; this result may be ascribed to Zn toxicity. Phosphorus and Zn showed complicated interactions in uptake by plants within the ranges of P and Zn levels used. Cadmium in shoots decreased significantly with increasing Zn (P < 0.001) except at P addition of 10 mg kg^?1. In contrast, root Cd concentrations increased significantly except at Zn addition of 5 mg kg^?1 (P < 0.001). These results indicated that Zn might inhibit Cd translocation from roots to shoots. Cadmium concentrations increased in shoots (P < 0.001) but decreased in roots (P < 0.001) with increasing P supply. The interactions between Zn and P had a significant effect on Cd accumulation in both shoots (p = 0.002) and roots (P < 0.001).     

Cadmium and zinc accumulation in willow and poplar species grown on polluted soils

Woody plant species that produce high biomass have been proposed for use in phytoremediation technology. We investigated the accumulation of cadmium (Cd) and zinc (Zn) in Salix babylonica, S. caprea, S. dasyclados, S. matsudana × alba, S. purpurea, S. smithiana, Populus tremula, and P. nigra clones grown in a pot experiment on a Calcaric and a Eutric Cambisol (pH 7.2 and 6.4) of different levels of contamination (total metal concentrations in mg kg^–1 in soil A: 32.7 Cd, 1760 Zn; soil B: 4.34 Cd, 220 Zn). Generally, the tested clones tolerated large metal concentrations in soils and had larger Cd and Zn concentrations in leaves compared to the roots. The largest Cd concentrations in leaves were found in two clones of S. smithiana (440 mg kg^–1 on soil A; 70 mg kg^–1 on soil B). One of the S. smithiana clones had also the largest Zn concentrations (870 mg kg^–1) on soil B but accumulated slightly less Zn than a S. matsudana × alba clone (2430 mg kg^–1) on soil A. The Cd concentrations in leaves of both S. smithiana clones on soil A are the largest ever reported for soil‐grown willows. The bioconcentration factors of the best performing clone reached 15.9 for Cd and 3.93 for Zn on the less contaminated soil B. Also based on the metal contents in leaves, this clone was identified as the most promising for phytoextraction. The metal concentrations in leaves observed in the pot experiment do not reflect those found in a previous hydroponic study and the leaf‐to‐root ratios are clearly underestimated in hydroponic conditions. This demonstrates the need for testing candidates for phytoextraction crops on soils rather than in hydroponics. Our data also show that the phytoextraction potential should be tested on different soils to avoid misleading conclusions.     

Response of Lettuce and Rhizosphere Biota to Successive Additions of Zinc and Cadmium to a Tropical Entisol

Response of lettuce and rhizosphere biota to successive addition of zinc (Zn) and cadmium (Cd) was assessed in a pot experiment using limed and unlimed tropical Entisol. Cadmium (2.5 mg kg^?1 soil) and Zn (50 mg kg^?1 soil) were spiked to soil 1 month after germination, and successive applications were superimposed as 5 and 10 times the first dose. Plants were analyzed for metal uptake and mycorrhizal colonization 1 week after each metal application. Rhizosphere soils were assessed for extractable Zn and Cd as well as populations of bacteria, fungi, and metal-tolerant fungi. The greatest metal doses resulted in 84–88 mg Zn and 8–10 mg Cd kg^?1 soil and 5–7.5 mg Cd and 70–72 mg Zn kg^?1 dry matter. Metal-tolerant fungi population increased from 9–13% to 26–63%, but mycorrhizal colonization and bacterial population were inhibited by 88% and 96%, respectively. Liming had relieved metal stress on rhizosphere biota but did not affect metal uptake.     

城郊菜地土壤重金属浓度及芦蒿吸收特征

A total of 222 surface soil samples and 40 plant samples were collected to investigate the spatial distribution and possible sources of soil heavy metals and to know the uptake and translocation of heavy metals from roots to different plant parts in a representative vegetable production area in the Baguazhou Island, a suburb of Nanjing City, East China. The arithmetic mean values of total Cd, Cr, Cu, Ni, Pb, and Zn concentrations in the soils were 0.314, 133, 41.0, 58.0, 31.8, and 114 mg kg^-1, respectively. All of these values were above the topsoil background values in the Nanjing area. Multivariate and geostatistical analyses showed that soil Cd contamination was derived mainly from agricultural practices. In contrast, Cu and Zn were derived mainly from soil parent materials and Pb from atmospheric deposition from highway gasoline stations. Artemisia selengensis, a locally important specialty vegetable, accumulated heavy metals primarily in the edible leaves. The general distribution of heavy metal concentrations in this plant species showed that the highest occurred in the leaves, intermediate in the stems and lowest in the roots. Cd had the highest concentration factor (root-to-soil ratio) and may pose increased health risks in the future to the local population through the consumption of contaminated vegetables.     

Immobilization of heavy metals in soils using inorganic amendments in a greenhouse study

The effect of red mud (10 g kg^–1), a by‐product of the alumina industry, zeolite (20 g kg^–1), a naturally‐occurring hydrous aluminosilicate, and lime (3 g kg^–1) on metal lability in soil and uptake by fescue (Festuca rubra L.) (FEST) and amaranthus (Amaranthus hybridus L.) (AMA) was investigated in four different soils from Austria. The soil collection locations were Untertiefenbach (UNT), Weyersdorf (WEY), Reisenberg (REI), and Arnoldstein (ARN). The latter was collected in the vicinity of a former Pb‐Zn smelter and was highly polluted with Pb (12300 mg kg^–1), Zn (2713 mg kg^–1), and Cd (19.7 mg kg^–1) by long‐term deposition. The other soils were spiked with Zn (700 mg kg^–1), Cu (250 mg kg^–1), Ni (100 mg kg^–1), V (100 mg kg^–1), and Cd (7 mg kg^–1) salts in 1987. The two plant species were cultivated for 15 months. Ammonium nitrate (1 M) extraction was used in a soil : solution ratio of 1:2.5 to assess the influence of the amendments on the labile metal pools. The reduction of metal extractability due to red mud was 70 % (Cd), 89 % (Zn), and 74 % (Ni) in the sandy soil (WEY). Plant uptake in this treatment was reduced by 38 to 87 % (Cd), 50 to 81 % (Zn), and 66 to 87 % (Ni) when compared to the control. Sequential extraction revealed relative enrichments of Fe‐oxide‐associated metal fractions at the expense of exchangeable metal fractions. Red mud was the only amendment that decreased lability in soil and plant uptake of Zn, Cd, and Ni consistently. Possible drawbacks of red mud application (e.g., As and Cr concentration) remain to be evaluated.     

Metal uptake in maize, willows and poplars on impoldered and freshwater tidal marshes in the Scheldt estuary

Foliar Cd and Zn concentrations in Salix, Populus and Zea mays grown on freshwater tidal marshes were assessed. Soil metal concentrations were elevated, averaging 9.7 mg Cd kg^?1 dry soil, 1100 mg Zn kg^?1 dry soil and 152 mg Cr kg^?1 dry soil. Cd (1.1–13.7 mg kg^?1) and Zn (192–1140 mg kg^?1) concentrations in willows and poplars were markedly higher than in maize on impoldered tidal marshes (0.8–4.8 mg Cd kg^?1 and 155–255 mg Zn kg^?1). Foliar samples of maize were collected on 90 plots on alluvial and sediment‐derived soils with variable degree of soil pollution. For soil Cd concentrations exceeding 7 mg Cd kg^?1 dry soil, there was a 50% probability that maize leaf concentrations exceeded public health standards for animal fodder. It was shown that analysis of foliar samples of maize taken in August can be used to predict foliar metal concentrations at harvest. These findings can therefore contribute to anticipating potential hazards arising from maize cultivation on soils with elevated metal contents.     

铅锌矿区分离丛枝菌根真菌对万寿菊生长与吸镉的影响

盆栽试验研究了土壤不同施Cd水平(0、20、50 mg kg-1)下,接种矿区污染土壤中丛枝菌根真菌对万寿菊根系侵染率、植株生物量及Cd吸收与分配的影响。结果表明:接种丛枝菌根真菌显著提高了Cd胁迫下万寿菊的根系侵染率和植株生物量;随着施Cd水平提高,各处理植株Cd浓度和Cd吸收量显著增加。各施Cd水平下万寿菊地上部Cd吸收量远远高于根系Cd吸收量,尤其在20 mg kg-1施Cd水平下,接种处理地上部Cd吸收量是根系的3.90倍,对照处理地上部Cd吸收量是根系的2.33倍;同一施Cd水平下接种处理地上部Cd吸收量要显著高于对照。总体上,试验条件下污染土壤中分离的丛枝菌根真菌促进了万寿菊对土壤中Cd的吸收,并增加了Cd向地上部分的运转,表现出植物提取的应用潜力。     

Selection of cultivars to reduce the concentration of cadmium and thallium in food and fodder plants

Pot and field experiments were carried out from 1994 to 1997 to investigate Cd and Tl uptake by various genotypes of maize, spring rape and kale on soils contaminated with i) Cd by the addition of river sediments (aqua regia-extractable Cd: 24 mg kg^—1 soil) and ii) with Tl by deposits from a cement plant (HNO₃-extractable Tl:1.4 mg kg^—1 soil). In field experiments on the Cd-contaminated soil, Cd concentrations in shoots and kernels of fifty maize inbred lines differed by a factor of about twenty (from < 1 to 15 mg Cd kg^—1 DM in shoots and from 0.02 to 0.5 mg Cd kg^—1 DM in kernels). After crossing inbred lines having high and low Cd concentration, Cd concentration of the resulting hybrids decreased, mainly as a result of a higher dry matter production (a dilution effect). In pot and field experiments on the Tl-contaminated soil, the selected cultivars of spring rape showed only small differences in Tl uptake, whereas Tl concentration in shoots of the kale cultivars differed more than twenty-fold (in the pot experiment from < 1 to 24 mg Tl kg^—1 DM and in the field experiment from 0.5 to 11.7 mg Tl kg^—1 shoot DM). Two groups of cultivars with low and high Tl concentrations could be distinguished. A nutrient solution experiment with radioactively labeled Tl showed that higher Tl concentration of kale in comparison to white cabbage can be attributed mainly to a higher uptake rate in kale (about 30-fold) with subsequent root-to-shoot translocation. The results show that, depending on plant species, selection and growing of cultivars with low heavy metal uptake on contaminated soils can substantially contribute to reduce the concentration of Cd and Tl in food and fodder plants.     

Depth distribution of aluminum and heavy metals in soils of Costa Rican coffee cultivation areas

Depth distributions of metals in soil profiles are indicative of weathering and soil genesis and anthropogenic pollution. We studied the depth distribution of total Al, Cd, Cu, Fe, Mn, Pb, and Zn concentrations in 8 Oxisols, 5 Andisols, 2 Mollisols, and 2 Alfisols of coffee plantation areas in Costa Rica. The concentrations of the mainly geo‐/pedogenic Al (means of 76 g kg^—1 in the A horizons and of 106 g kg^—1 in the lowermost sampled B horizons) and Fe (A: 56 g kg^—1, B: 66 g kg^—1) generally increased with profile depth. In spite of the regular application of Cu‐containing fungicides, Cu (A: 135 mg kg^—1, B: 158 mg kg^—1) showed accumulations in the A horizons of only three profiles. Higher Cd (A: 0.14 mg kg^—1, B: 0.09 mg kg^—1) and Pb concentrations (A: 7.3 mg kg^—1, B: 5.5 mg kg^—1) in most topsoils compared to the subsoils indicated anthropogenic inputs. The mean Mn (A: 1190 mg kg^—1, B: 1150 mg kg^—1) and Zn (A: 59 mg kg^—1, B: 66 mg kg^—1) concentrations varied little with depth. In general, the metal depth distribution in the studied tropical soils was similar to that of temperate soils although the weathering regime is quite different.     

Effects of Soil Amendments on Growth and Metal Uptake by Ocimum gratissimum Grown in Cd/Zn-Contaminated Soil

Hydroponic and pot experiments were conducted to assess the uptake of heavy metals (Cd and Zn) by a common crop plant, African basil, Ocimum gratissimum. In addition, the effects of soil amendments, hydroxyapatite (HA) and cow manure on plant growth and metal accumulations were compared. In the hydroponic study, plants were exposed to various concentrations of Cd (2.5 and 5 mg L^?1) and Zn (10 and 20 mg L^?1) for 15 days. O. gratissimum was shown to be a Cd accumulator more than a Zn accumulator. Cadmium concentration in its shoots exceeded 100 mg kg^?1. In the pot experiments, soils from a heavily Cd-contaminated site (Cd 67.9 mg kg^?1 and Zn 2,886.8 mg kg^?1) were treated with cow manure and HA at the rates of 10% and 20% (w/w), and 0.75 and 1.5% (w/w), respectively. Plants were grown in the greenhouse for 3 months. The addition of cow manure resulted in the highest biomass production and the lowest accumulations of Cd in plant parts, while HA was more efficient than cow manure in reducing Zn uptake. Leaves of African basil showed a decreased Cd concentration from 1.5 to 0.3 mg kg^?1 (cow manure) and decreased Zn concentration from 69.3 to 34 mg kg^?1 (HA). This clearly demonstrates the efficiency of HA and cow manure in reducing metal content in leaves of plants grown on high metal-contaminated soil to acceptable or close to acceptable values (0.2 mg kg^?1 for Cd, 99.4 mg kg^?1 for Zn).     

A Laboratory Study on Revegetation and Metal Uptake in Native Plant Species from Neutral Mine Tailings

Lygeum spartum, Zygophyllum fabago and Piptatherum miliaceum are typical plant species that grow in mine tailings in semiarid Mediterranean areas. The aim of this work was to investigate metal uptake of these species growing on neutral mine tailings under controlled conditions and their response to fertilizer additions. A neutral mine tailing (pH of soil solution of 7.1–7.2) with high total metal concentrations (9,100 and 5,200 mg kg^?1 Zn and Pb, respectively) from Southern Spain was used. Soluble Zn and Pb were low (0.5 and <0.1 mg l^?1, respectively) but the major cations and anions reached relatively high levels (e.g. 2,600 and 1,400 mg l^?1 Cl and Na). Fertilization caused a significant increase of the plant weight for the three species and decreased metal accumulation with the exception of Cd. Roots accumulated much higher metal concentrations for the three plants than shoots, except Cd in L. spartum. Shoot concentrations for the three plants were 3–14 mg kg^?1 Cd, 150–300 mg kg^?1 Zn, 4–11 mg kg^?1 Cu, and 1–10 mg kg^?1 As, and 6–110 mg kg^?1 Pb. The results indicate that neutral pH mine tailings present a suitable substrate for establishment of these native plants species and fertilizer favors this establishment. Metal accumulation in plants is relatively low despite high total soil concentrations.     

Genotypic differences in uptake and translocation of cadmium in bean and maize inbred lines

For better understanding of mechanisms responsible for genotypic differences in uptake and translocation of cadmium (Cd) in different plant species, two maize (Zea mays L.) inbred lines (B37 and F2) and a bean (Phaseolus vulgaris L.) cultivar (Saxa) were grown in a complete nutrient solution with additional 0.5 μM Cd and 250 μM buthionine sulfoximine (BSO), an inhibitor of PC synthesis, alone or in combination. The maize line B37 had a much higher Cd content in shoots (116.2 mg Cd kg^?1 dry wt.) than F2 (32.7 mg Cd kg^?1 dry wt.) and bean (1.83 in leaves, and 2.85 mg Cd kg^?1 dry wt. in stems), whereas in roots the Cd content was much higher in bean (602.6 mg Cd kg^?1 dry wt.) than in maize (427.1 mg Cd kg^?1 dry wt. in B37, and 428.2 mg Cd kg^?1 dry wt. in F2). Application of BSO markedly decreased Cd contents in roots of bean and maize lines, and also Cd contents in shoots and stem basis of both maize lines, while Cd contents in leaves, stems and stem basis of bean were not reduced by BSO. In root extracts (Tris-HCl buffer, pH 8.0) the proportion of Cd in the soluble fraction was much lower in bean (29.6%) than in the maize lines B37 (58.6%) and F2 (60.1%). Compared with the whole root tissue, Cd contents in the stele of the roots were much lower, especially in bean, and decreased by BSO in both maize lines, but not in bean. Gel-chromatography of root extracts strongly suggested that in the soluble fraction about 80% of the Cd was present as Cd-phytochelatin (PC) complexes in B37, whereas in F2 this Cd fraction accounted for about 50%, and in bean only for a few percent in the soluble fraction, Our results suggest that Cd-PC complexes constitute a mobile form in plants. The lower proportion of Cd in the soluble fraction as well as lower PC production in roots of bean compared to maize lines may be the main reasons for the very low Cd translocation from roots to shoots in bean plants.     

Removal of Lead from Contaminated Soils by Typha Angustifolia

A greenhouse study was demonstrated for removal of lead (Pb) from contaminated soil by the narrow — leaved cattail, Typha angustifolia. The plants were grown in sandy loam soil containing various concentrations of Pb(NO₃)₂ (53.3, 106.7, 160, 213.3, and 266.7 mg Pb kg^-1 soil). Most lead was accumulated in roots and then transported to leaves. In soil contaminated with 266.7 mg kg^-1 of lead, the plants accumulated 7492.6 mg Pb kg^-1 dry weight in the roots and 167 mg Pb kg^-1 dry weight in the leaves. Yet, no growth retardation from lead was detected. T. angustifolia has high potential as a plant to clean up lead contaminated soil due to its vigorous growth, high biomass productivity, and because it is a perennial in nature. Further work is required to study on the iron plaque formation and its role in metal immobilization.     

Use of the BCR three-step sequential extraction procedure for the study of the partitioning of Cd, Pb and Zn in various soil samples

A slightly modified three-step sequential extraction procedure proposed by the Community Bureau of Reference (BCR) for analysis of sediments was successfully applied to soil samples. Contaminated soil samples from the lead and zinc mining area in the Mezica valley (Slovenia) and natural soils from a non-industrial area were analysed. The total concentrations of Cd, Pb and Zn and their concentrations in fractions after extraction were determined by flame or electrothermal atomic absorption spectrometry (FAAS, ETAAS). Total metal concentrations in natural soils ranged from 0.3 to 2.6 mg kg^-1 for Cd, from 20 to 45 mg kg^-1 for Pb and from 70 to 140 mg kg^-1 for Zn, while these concentrations ranged from 0.5 to 35 mg kg^-1 for Cd, from 200 to 10000 mg kg^-1 for Pb and from 140 to 1500 mg kg^-1 for Zn in soils from contaminated areas. The results of the partitioning study applying the slightly modified BCR three-step extraction procedure indicate that Cd, Pb and Zn in natural soils prevails mostly in sparingly soluble fractions. Cd in natural soils is bound mainly to Fe and Mn oxides and hydroxides, Pb to organic matter, sulphides and silicates, while Zn is predominantly bound to silicates. In contaminated soils, Cd, Pb and Zn are distributed between the easily and sparingly soluble fractions. Due to the high total Cd, Pb and Zn concentrations in contaminated soil close to the smelter, ! and their high proportions in the easily soluble fraction (80% of Cd, 50% of Pb and 70% of Zn), the soil around smelters represents an environmental hazard.     

Relationship Between Extractable Metals in Acid Soils and Metals Taken Up by Tea Plants

Abstract

The accumulation of heavy metals in plants is related to concentrations andchemical fractions of the metals in soils. Understanding chemical fractions and availabilities of the metals in soils is necessary for management of the soils. In this study, the concentrations of copper (Cu), cadmium (Cd), lead (Pb), and zinc (Zn) in tea leaves were compared with the total and extractable contents of these heavy metals in 32 surface soil samples collected from different tea plantations in Zhejiang province, China. The five chemical fractions (exchangeable, carbonate‐bound, organic matter‐bound, oxides‐bound, and residual forms) of the metals in the soils were characterized. Five different extraction methods were also used to extract soil labile metals. Total heavy metal contents of the soils ranged from 17.0 to 84.0 mgCukg^?1, 0.03 to 1.09 mg Cd kg^?1, 3.43 to 31.2 mg Pb kg^?1, and 31.0 to 132.0 mg Zn kg^?1. The concentrations of exchangeable and carbonate‐bound fractions of the metals depended mainly on the pH, and those of organic matter‐bound, oxides‐bound, and residual forms of the metals were clearly controlled by their total concentrations in the soils. Extractable fractions may be preferable to total metal content as a predictor of bioconcentrations of the metals in both old and mature tea leaves. The metals in the tea leaves appeared to be mostly from the exchangeable fractions. The amount of available metals extracted by 0.01 mol L^?1 CaCl₂, NH₄OAc, and DTPA‐TEA is appropriate extractants for the prediction of metals uptake into tea plants. The results indicate that long‐term plantation of tea can cause sol acidification and elevated concentrations of bioavailable heavy metals in the soil and, hence, aggravate the risk of heavy metals to tea plants.     

Einfluß der VA-Mykorrhiza auf die Schwermetallaufnahme von Hafer (Avena sativa L.) in Abhängigkeit vom Kontaminationsgrad der Böden

Influence of VA-mycorrhiza on heavy metal uptake of oat (Avena sativa L.) from soils differing in heavy metal contamination The heavy metal uptake of mycorrhizal oat-plants (Avena sativa L.) was evaluated in pot experiments with two soils differing in heavy metal accumulation. The effect of the fungal isolates on the uptake of the immobile metals Zn and Cu differed between the two soils: In the soil “Kleinlinden” mycorrhizal colonization increased heavy metal uptake by up to 37%. In the highly contaminated soil “München”, mycorrhizal infection lead to a higher uptake (max. 59 %) in roots but to a reduced translocation to the aerial plant fractions. The higher uptake of Zn and Cu into the roots was related to the higher heavy metal concentrations in this soil. The Cd uptake showed no difference between the two soils, but was increased in the roots by VAM together with a lower translocation into the shoots. VAM-formation changed the root architecture by increasing the specific root length (m g^?1 root dry matter) and the total root length (km per pot). This increased absorbing surface of the roots was a major, but not the only cause for the differences in heavy metal uptake.     

干旱与Cd双重胁迫对土壤-小麦-蚜虫系统Cd转移规律影响的研究

为探究干旱和重金属双重胁迫对土壤-小麦-蚜虫系统内Cd转移规律的影响,为小麦蚜虫的生态调节提供理论依据,本研究以麦长管蚜[Sitobionavenae(Fabricius)]为研究对象,用原子吸收分光光度法分别测定不同土壤Cd含量(100 mg?kg-1、200 mg?kg-1)及不同程度干旱胁迫(无胁迫、中度胁迫、重度胁迫)处理下小麦根茎叶及蚜虫体内的Cd含量。结果表明:土壤Cd含量及干旱单一胁迫均对小麦及蚜虫体内的Cd含量造成了显著影响(P0.05)。两者交互作用对小麦根部及叶部的Cd含量影响显著,而对小麦茎部及蚜虫体内Cd含量影响不显著。在相同胁迫条件下, Cd在小麦中的积累分布为根茎叶。随着干旱胁迫程度增大,小麦根部Cd含量及土壤-根转移系数降低,茎部Cd含量及根-茎转移系数升高,麦长管蚜Cd含量在土壤Cd含量100mg?kg-1下高于土壤Cd含量200 mg?kg-1;中度干旱胁迫增加了麦长管蚜体内Cd累积量,而重度干旱胁迫则降低了其体内Cd累积量。叶-蚜虫的Cd转移系数明显大于土壤-根、根-茎和茎-叶转移系数且大于1,说明Cd在麦长管蚜体内产生了生物富集作用。综上所述,干旱胁迫促进了Cd从土壤向小麦茎部转移和根部Cd累积,但抑制了Cd从根部到茎部转移和茎部Cd累积;中度干旱胁迫促进了麦长管蚜体内Cd的积累,而重度干旱胁迫抑制了麦长管蚜体内Cd的积累。