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1.
Barley (Hordeum vulgare L.) was grown on a sandy soil given different doses of cadmium carbonate (salt), copper carbonate (malachite), lead carbonate (cerussite), and zinc carbonate (smithsonite) in a pot experiment conducted in a greenhouse. The element compounds were added to the soil in amounts equivalent to the following levels of the metals: Cd 5, 10, 50 μq ?1; Cu and Pb 50, 100, 500 μg g?1; Zn 150, 300, 1500 μg g?1. Sequential extraction was used for partition these metals into five operationally-defined fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The residue was the most abundant fraction in the untreated soil for all the metals studied (43 to 61% of the total contents). The concentration of exchangeable Cd (0.2 μg g?1), Cu (0.01 μg g?1), Pb (0.1 μg g?1), and Zn (1.4 μg g?1) were relatively low in the untreated soil but increased markedly in the treated soils for Cd (up to 31 μg g?1) and Zn (up to 83 μg g?1), whereas only small changes were observed for Cu and Pb. The pot experiment showed a significant increase in the Cd and Zn contents of barley grown on the treated soils, but only small changes in Cu and Pb concentrations.  相似文献   

2.
The effect of increasing concentrations of Cd and Zn in a sandy soil on spring wheat (Triticum vulgare L.) yields and the metal contents of the plants was examined in a pot experiment to establish critical levels of these metals in soil. The metals were added (individually and jointly) to the soil as sulfates in the following doses (in μg g?1, dry wt.): Cd — 2, 3, 5,10, 15, 25, and 50; Zn ?200, 300, 500, 1000, 1500, 2500, and 5000. Cadmium added to soil did not affect yields of wheat. The Zn dose of 1000 μg g?1 strongly reduced crop yields; at 1500 μg g? Zn dose wheat did not produce grain. The metal contents of wheat increased with increasing concentrations of Cd and Zn in soil up to 10.3 and 1587 μ g? of Cd and Zn in straw, respectively. The concentrations of both metals were higher in straw than in grain by factors of 3–7 and 1.5–2 for Zn and Cd, respectively. The relationships between Cd and Zn contents of the plants and soils were best expressed by exponential equations. High concentrations of Zn in soils (1042 and 1542 μg g?1) enhanced uptake of Cd by plants. The tested threshold concentrations of the metals in soils (3 μg g?1 for Cd and 200–300 μg g?1 for Zn) are safe for Zn but are too high for Cd in terms of protecting plants from excessive metal uptake. The critical Cd content of sandy soil should not exceed 1.5 μg g?.  相似文献   

3.
Lettuce (Lactuca sativa L.) and dry beans (Phaseolus vulgaris L.) were grown in three Brazilian Red-Yellow Latossols (Oxisols) in greenhouse conditions with cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), and nickel (Ni) applied to soils in treatments arranged as a randomized complete block design. Plant metals were analyzed in lettuce shoots and dry beans roots, stems, leaves, and seeds. After plant growth, soil samples from the pots were extracted with Mehlich-3 (M-3) for metal availability evaluation. The release of Ni in the M-3 extraction was dependent on the soil exchangeable aluminum (Al3 +). Mehlich-3 was efficient for determination of availability of Cd, Pb, Cu, Zn, and Ni for dry beans and availability of Cd and Ni for lettuce. The dry bean leaves Cd, Pb, Cu, Zn, and Ni were highly correlated with their recovering from soils with M-3. The same was observed for Cd and Ni in lettuce shoots and the M-3 recovered metals from soils.  相似文献   

4.
Forms of Cu, Ni, and Zn in the contaminated soils of the Sudbury mining/smelting district were studied to assess metal mobility and plant availability. Soil, tufted grass (Deschampsia caespitosa (L.) Beauv.), tickle grass (Agrostis scabra Willd.), dwarf birch (Betula pumila L. var. glandulifera Regel) and white birch (Betula paprifera Marsh.) leaf and twig samples were taken from 20 locations around three Cu-Ni smelters. The sampling sites were collected to cover a wide range of soil pH and soil Cu and Ni concentrations. The water-soluble, exchangeable, sodium acetate-soluble, and total concentrations of the metals in the soils were analyzed. The soils were contaminated with Cu and Ni up to 2000 µg g?1. Zinc concentrations were also elevated in some samples above the normal soil level of 100 µg g?1. The mobility of Cu and Zn, expressed as the proportion of metals in Fl and F2 forms, increased with soil pH decrease. A strong positive correlation was found between the soil exchangeable (F2) Ni and the soil pH. Concentrations of Cu and Ni in birch twigs showed a good linear relationship with exchangeable forms of the metals in soils. A highly significant correlation was also found between total Ni in soils and the metal content of the twigs. No significant correlation was found between Zn concentrations in the soils and plants. Birch twigs are a good indicator (better than leaves) of Cu and Ni contamination of the Sudbury soils. The mobile forms of Cu and Ni and low pH seem to be the main factors that will control the success of revegetation. Strong variability of the soil metal mobility requires any reclamation effort be site-specific.  相似文献   

5.
The monitoring of heavy metal deposition onto soils surrounding old Pb-Zn mines in two locations in the UK has shown that relatively large amounts of Cd, Pb, Zn and, in one case, Cu are entering the soil annually. Small particles of ore minerals in windblown mine tailings were found to be contributing up to 1.46 g m?2 yr?1 of Pb, 1.41 g m?2 yr?1 of Zn and 0.027 g m?2 yr?1 of Cd. However, when these inputs from bulk deposition are compared with the concentrations of the same metals within the soil profiles it is apparent that relatively little long-term accumulation is occurring. Metals are being lost from the soil profiles, probably through leaching. A calculated relative retention parameter gave values that ranged from 0.01 to 0.17 for Cd, 0.11 to 0.19 for Zn, 0.32 to 0.63 for Cu and over 1 for Pb. These relative retention values were found to follow the order of electronegativity of the elements concerned: Pb>Cu>Zn>Cd. Distribution coefficient (Kd) values quantifying the adsorptive capacity of the mine soils for Cd and Pb showed marked differences for the two metals (12 to 69 cm3 g?1 for Cd and 14 to 126 cm3 g?1 for Pb) and may, in part, account for the two to one hundred-fold variation in the relative retention parameter for the different metals within these soils.  相似文献   

6.
The relationships between heavy metal concentrations and physico-chemical properties of natural lake waters and also with chemical fractions of these metals in lake sediments were investigated in seven natural lakes of Kumaun region of Uttarakhand Province of India during 2003–2004 and 2004–2005. The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l?1 and in sediments 14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9, 13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g?1, respectively. The concentrations of all metals except Fe in waters were found well below the notified toxic limits. The concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were positively correlated with pH, electrical conductivity, biological oxygen demand, chemical oxygen demand and alkalinity of waters, but negatively correlated with dissolved oxygen. The concentrations of Cr, Ni, Zn, Cd and Pb in waters were positively correlated with water soluble + exchangeable fraction of these metals in lake sediments. The concentrations of Zn, Cd and Pb in waters were positively correlated with carbonate bound fraction of these metals in lake sediments. Except for Ni, Zn and Cd, the concentrations of rest of the heavy metals in waters were positively correlated with organically bound fraction of these metals in lake sediments. The concentrations of Cr, Mn, Ni, Cu and Zn in waters were positively correlated with reducible fraction of these metals in lake sediments. Except for Cd, the concentrations of rest of the metals in waters were positively correlated with residual fraction and total content of these heavy metals in lake sediments.  相似文献   

7.
The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg?1) > copper (Cu; 196 mg kg?1) > chromium (Cr; 175 mg kg?1) > lead (Pb; 131 mg kg?1) > nickel (Ni; 60 mg kg?1) > cadmium (Cd; 4 mg kg?1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions were oxide, organic, and residual for Ni, Pb, and Zn; organic and oxide for Cr; oxide for Cd; and organic for Cu. Leaching tests for water and acid indicated that the ratio of leached metal concentration to total metal concentration in the soil decreased in the order of Cd > Ni > Cr > Pb > Cu > Zn and in the order of Cd > Ni > Cr > Zn > Cu > Pb for the ethylenediaminetetraaceitc acid (EDTA) treatment. The EDTA treatment gave greater leachability than other treatments for most metal types. By leaching with water and acid, all heavy metals were fully released from the exchangeable fraction, and some heavy metals were fully released from carbonate and oxide fractions. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the vegetables exceeded the Vietnamese standards. The transfer coefficients for the metals were in the order of Zn > Ni > Cu > Cd = Cr > Pb.  相似文献   

8.
Toxicity of heavy metals (Zn,Cu, Cd,Pb) to vascular plants   总被引：1，自引：0，他引：1  
The literature on heavy metal toxicity to vascular plants is reviewed. Special attention is given to forest plant species, especially trees, and effects at low metal concentrations, including growth, physiological, biochemical and cytological responses. Interactions between the metals in toxicity are considered and the role of mycorrhizal infection as well. Of the metals reviewed, Zn is the least toxic. Generally plant growth is affected at 1000 μg Zn L?1 or more in a nutrient solution, though 100 to 200 µg L?1 may give cytological disorders. At concentrations of 100 to 200 μg L?1, Cu and Cd disturb metabolic processes and growth, whereas the phytotoxicity of Pb generally is lower. Although a great variation between plant species, critical leaf tissue concentrations affecting growth in most species being 200 to 300 μg Zn g?1 dry weight, 15 to 20 μg Cu g?1 and 8–12 μg Cd g?1. With our present knowledge it is difficult to propose a limit for toxic concentrations of Zn, Cu, Cd and Pb in soils. Besides time of exposure, the degree of toxicity is influenced by biological availability of the metals and interactions with other metals in the soil, nutritional status, age and mycorrhizal infection of the plant.  相似文献   

9.
A field study was conducted to determine the plant uptake of metals in soils amended with 500 Mg ha?1 of municopal sewage sludge applied 16 yr previously. Results showed that metals were available for plan uptake after 16 yr, but that liming greatly reduced the plant availability of most metals. The application of sludge also resulted in high rates nitrification and subsequent lowering of the soil pH before the uptake study was started. The sludge-amended soil (a mesic Dystric Xerochrept) was adjusted with lime one month prior to planting from an unlimed pH of 4.6 to pH 5.8, 6.5 and 6.9. Food crops grown were: (i) bush bean (Phaseolus vulgaris L. cv. Seafarer), (ii) cabbage (Brassica oleracea L. v. capitata L. cv. Copenhagen market), (iii) maize (Zea mays L. cv. FR37), (iv) lettuce (Lactuca sativa L. cv. Parris Island, (v) (Solanum tuberosum L. cv. (vi) tomato (Lycopersicum esculentum L. cv. Burpee VF). With the exception of maize, yields were significantly reduced in the unlimed sludge-amended soil. However, liming increased yields above the growth level of the unlimed untreated soil for cabbage, maize, lettuce, potato tuber and tomato fruit. Soluble and exchangeable of Cd. Ni and Zn were also reduced after liming the sludge-amended soil. In both limed and unlimed soils, the majority of the soil Cu was found in insoluble and unavailable soil fractions. To evaluate trace metal uptake, the edible portion of each crop was analyzed for Cd, Cu, ni and Zn. Liming redoced uptake of Cd, Ni and Zn in most crops, but generally did not change Cu, This study shows the benefit of pH adjustment in reducing relative solubility and plant uptake of metals as well as increasing crop yield in acid soils.  相似文献   

10.
Abstract: The fraction distributions of heavy metals have attracted more attention because of the relationship between the toxicity and their speciation. Heavy‐metal fraction distributions in soil contaminated with mine tailings (soil A) and in soil irrigated with mine wastewater (soil B), before and after treatment with disodium ethylenediaminetetraacetic acid (EDTA), were analyzed with Tessier's sequential extraction procedures. The total contents of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) exceeded the maximum permissible levels by 5.1, 33.3, 3.1, and 8.0 times in soil A and by 2.6, 12.0, 0.2, and 1.9 times in soil B, respectively. The results showed that both soils had high levels of heavy‐metal pollution. Although the fractions were found in different distribution before extraction, the residual fraction was found to be the predominant fraction of the four heavy metals. There was a small amount of exchangeable fraction of heavy metals in both contaminated soils. Furthermore, in this study, the extraction efficiencies of Pb, Cd, and Cu were higher than those of Zn. After extraction, the concentrations of exchangeable Pb, Cd, Cu, and Zn increased 84.7 mg·kg?1, 0.3 mg·kg?1, 4.1 mg·kg?1, and 39.9 mg·kg?1 in soil A and 48.7 mg·kg?1, 0.6 mg·kg?1, 2.7 mg·kg?1, and 44.1 mg·kg?1 in soil B, respectively. The concentrations of carbonate, iron and manganese oxides, organic matter, and residue of heavy metals decreased. This implies that EDTA increased metal mobility and bioavailability and may lead to groundwater contamination.  相似文献   

11.
泉州走马埭典型土壤重金属的赋存形态分析   总被引：5，自引：3，他引：2  
何园  王宪  陈丽丹  郑盛华  蔡真珍 《土壤》2007,39(2):257-262
采用改进的Tessier连续萃取方法研究了泉州走马埭国家农田示范保护区典型土壤中重金属(Cr、Ni、Cu、Zn、Cd、Pb)的化学形态分布,通过土壤重金属的赋存形态分析比较了6种重金属的生物可利用性。研究结果表明,土壤中不同重金属元素化学形态分布具有不同的特点:Cr和Ni主要以残渣态存在,其余形态所占的比例很小;Cu以残渣态含量最高,碳酸盐结合态含量最低;Zn以残渣态为主,可交换态含量最低;Cd以可交换态和碳酸盐结合态为主,水溶态含量最低;Pb以残渣态和铁锰氧化物结合态为主,水溶态含量最低。土壤中除Cd外,Zn、Cu、Cr、Pb、Ni在正常自然条件下相对比较稳定。  相似文献   

12.
广东大宝山矿区土壤重金属污染   总被引：28，自引：0，他引：28  
Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determi- nation of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels （P ≤ 0.05） of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1486, 2516, 6.42, and 429 mg kg^-1, respectively. These metals were continuously dispersed downstream from the tallings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1 140, 2.48, and 191 mg kg^-1, respectively, being significantly higher （P ≤ 0.05） as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.  相似文献   

13.
水稻子实对不同形态重金属的累积差异及其影响因素分析   总被引：3，自引：0，他引：3  
在分析成都平原核心区土壤重金属(Cd、Cr、Pb、Cu、Zn)全量、各形态含量及相应点位种植的水稻子实重金属含量的基础上,通过统计分析、空间插值及线性回归方程的模拟,研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征,以及水稻子实对重金属各形态的累积差异及其影响因素。结果表明,成都平原水稻土重金属污染较轻,除Cd外,均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低,Cd主要以铁锰氧化态存在,Cr、Cu、Zn、Pb主要以残渣态存在。水稻子实对5种重金属的累积效应顺序为:Cd>Zn>Cu>Pb>Cr。与水稻重金属累积关系密切的重金属活性形态(可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态)主要有:Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量;Zn各活性形态对水稻子实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响;活性态Cr与pH、有机质、CEC和容重密切相关;活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系;Cu的活性主要受粘粒、有机质含量的影响;Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来,对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重,而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。  相似文献   

14.
重金属高污染农田土壤EDTA淋洗条件初探   总被引：7，自引：1，他引：6  
通过室内振荡淋洗试验研究了乙二胺四乙酸二钠(EDTA)浓度、淋洗时间、液固比、淋洗次数对甘肃省白银市某高污染农田土壤中重金属去除效果的影响,并测定了EDTA淋洗前后土壤中重金属形态的变化。结果表明：淋洗剂浓度和液固比越高、淋洗时间越长、淋洗次数越多,对重金属的去除效果越好。在EDTA浓度为5 mmol/L、液固比为2.5、连续振荡淋洗3次、每次1 h时,对土壤中Cd、Cu、Pb、Zn 4种重金属的总去除率分别为 55.2%、21.9%、19.3% 和20.9%,其中Cd 淋洗效率最高。EDTA对土壤中交换态、碳酸盐结合态和铁锰氧化物结合态重金属的去除效果明显,但不能有效去除有机及硫化物态和残余态土壤重金属。  相似文献   

15.
Used with one of two surfactants (SDS, an anionic surfactant, and Triton X-100, a nonionic surfactant), the ligand, I? was evaluated as a washing agent for the desorption of Cd from naturally and artificially contaminated soils. Increasing amounts of the ligand, I?, with a surfactant, specifically removes higher levels of Cd but not Cu, Zn and Pb. After seven washings, the ligand, I? with the nonionic surfactant, Triton X-100, removed 65 and 90% of the Cd from soils I and II, containing respectively, to 15 and 1275 mg of Cd/kg. The ligand, I?, and the anionic surfactant, SDS, removed 35 and 70% of the Cd from soils I and II, respectively. Before washing, the carbonate fraction of soil I contained the most Cd (48%) while the exchangeable and carbonate fractions of soil II contained 29 and 33% of the total Cd, respectively. For soil I, SDS with/ without the ligand desorbed Cd mainly from the carbonate and oxide fractions, while only Triton X-100 with ligand I? could remove Cd from the exchangeable fraction. For soil II, Cd was desorbed from the exchangeable fraction only when either surfactant was used in combination with the ligand. Thus, a surfactant with ligand can extract specific heavy metals from soils and selective sequential extraction is useful in identifying which fraction can be targeted by the surfactant – ligand agent.  相似文献   

16.
Maintaining the quality of groundwater is a major consideration when developing management practices to effectively use cow dung manure (CDM) as a nutrient source and soil conditioner in agricultural production systems. This study examines the effect of CDM on the solubility of copper (Cu), lead (Pb), and zinc (Zn) in urban garden fields from Kaduna under long-term vegetable production. Soil samples were collected from Kakau, Kakuri, Trikaniya, and Romi in Kaduna metropolis in northern Nigeria. Soil–manure mixtures at the rate of 100 g CDM kg?1 soil were incubated for 2 weeks and analyzed for exchangeable [0.1 M calcium chloride (CaCl2)–extractable], mobile [1 M ammonium nitrate (NH4NO3)–extractable], and potentially labile [0.05 M ethylenediaminetetraacetic acid (EDTA)–extractable] copper (Cu), lead (Pb), and zinc (Zn). Addition of CDM increased exchangeable Cu in Kakuri and Romi and exchangeable Pb in Kakau and Kakuri, but decreased exchangeable Zn across the sites. The addition of CDM increased mobile Cu and Pb in all the sites. Although there was a decrease in mobile Zn in Kakau and Romi after the soil–manure incubation period, mobile Zn increased in Trikaniya and Kakuri. Furthermore, CDM decreased potentially labile Cu, Pb, and Zn in all the sites except for Romi, which increased labile Cu. To sustain the quality of soil and minimize groundwater pollution and food chain contamination, use of CDM in urban garden soils polluted with Cu, Pb, and Zn should be regulated or discouraged entirely to reduce the mobility of these metals.  相似文献   

17.
Total topsoil 50th percentile Cu, Pb and Zn concentrations (n?=?491) in the Sydney estuary catchment were 23 ??g?g?1, 60 ??g?g?1 and 108 ??g?g?1, respectively. Nine percent, 6% and 25% of samples were above soil quality guidelines, respectively and mean enrichment was 14, 35 and 29 times above background, respectively. Soils in the south-eastern region of the catchment exhibited highest metal concentrations. The close relationship between soil metal and road network distributions and outcomes of vehicular emissions modelling, strongly suggested vehicular traffic was the primary source of metals to catchment soils. Catchment soil and road dust probably make an important contribution to contamination of the adjacent estuary. The concentration of soil metals followed the land use trend: industrial?>?urban?>?undeveloped areas. A high proportion (mean 45%, 62% and 42%, for Cu, Pb and Zn, respectively) of metals in the soils may be bioavailable.  相似文献   

18.
A sequential extraction procedure was used to fractionate Cu, Cd, Pb and Zn in 4 soil profiles into the designated forms of water soluble + exchangeable, organically bound, carbonate and Mn oxides bound. Soil profiles were obtained from the Rural Development District 063, State of Hidalgo, which have been irrigated with wastewater coming out of the basin of Mexico. The total heavy metal contents range as follows: Cu, 8.9 to 86.5 mg kg-1 Cd, 0.86 to 5.07 mg kg-1 Pb, 18.1 to 131.7 mg kg-1 and Zn, 101 to 235.5 mg kg-1. The highest concentrations of total heavy metals were found in the surface layers at all soil profiles. Sequential chemical fractionation indicated that the four metals were predominantly associated with the organic fraction at most soil samples. The contents in all fractions of the four metals showed a decrease with depth which has been explained by the variations in the organic matter and CaCO3 contents in the different layers of soils. These soil properties were also the most important variables in the biological availability of the metals in these soils.  相似文献   

19.
Trace metals such as Pb, Zn, Cu, Ni, Cd and Fe were determined in sewage sludge produced at a sewage treatment plant in Bahrain (Tubli) and soils. The soils, both untreated and treated with the sludge, are used for agricultural purposes in Bahrain. The Trace-metals level showed the following range (μg g?1 dry weight); Pb, 242 to 609; Zn, 704 to 836, Cu, 329 to 512; Ni, 23 to 41; Cd, 1.8 to 3.9 and Fe, 1867 to 4284. The data show the degree to which untreated soils have already been contaminated with trace elements. The level of trace-elements found in sludge showed the following range (μg g?1 dry weight); Pb, 140 to 186; Zn, 597 to 836; Cu, 348 to 449; Ni, 47 to 53; Cd 5.7 to 9.2 and Fe, 5950 to 8520. Mean levels were generally close or lower than mean concentration reported in the United Kingdom and the United States for sludge. They were also lower than the suggested concentration limits for application of sludge on agricultural land, which is one of the most cost effective and attractive techniques for sludge disposal. Soils treated with this sludge (after 1 yr) were also analyzed and showed substantial enhancement of the available level of trace elements in the soil. This eventually will lead to an increase in the trace-element level in plants grown for human or animal consumption. This could have phytotoxic effects, and the possibility of toxic effects on live-stocks and human beings.  相似文献   

20.
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.  相似文献   

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