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1.
Abstract

The recovery of applied zinc (Zn) by plants is relatively small. Coupled with lack of leaching, this leads to accumulation of Zn in topsoil which may result in unfavorable growth conditions for the subsequent plants. Different extractants may be used for assessing the Zn status of soils previously treated with Zn sources. The extractability of retained Zn is influenced by soil properties. This experiment was conducted to study the influence of selected properties of calcareous soils on extractability of Zn by three popular Zn soil tests. Twenty samples from surface horizons (0–20 cm) of highly calcareous soils of southern Iran (pH 7.9 to 8.5; calcium carbonate equivalent 16 to 58%) previously treated with three levels of Zn (0, 10, and 20 mg Zn kg‐1 soil as ZnSO4#lb7H2O) in triplicate and under one crop of corn (Zea mays L.) were extracted with DTPA, EDTA‐(NH4)2CO3 and Na2‐EDTA. Extractability (EXT) in a particular extractant was defined as the slope of the regression line, relating extractable Zn of each soil to the rate of applied Zn, multiplied by 100. The EXT values of soils ranged from 24.9 to 73.0% for DTPA, 47.2 to 84.4% for EDTA‐(NH4)2CO3, and 28.2 to 56.7% for Na2‐EDTA. Stepwise regression equations showed that cation exchange capacity (CEC) and calcium carbonate equivalent (CCE) followed by clay content were the most influential soil properties in EXT of retained Zn of highly calcareous soils. The EXT values decreased with increase in CEC, and CCE but increased with increase in clay.  相似文献   

2.
Ethylendiamintetraacetic acid (EDTA) is persistent in the environment. The presence of EDTA in soil may alter the mobility and transport of Zn, Cd and Ni in soils because of the formation of water soluble chelates, thus increasing the potential for metal pollution of natural waters. Mobility of metals is related to their extractability. To investigate metal extractability affected by EDTA, Zn, Cd and Ni were added to Vertisol and Alluvial soil at rates of 50, 2 and 5 mg kg-1, respectively. Both natural and metal amended soils were treated with Na2EDTA at rates of 0; 0.2 and 0.5 mg kg-1. After five months of incubation soil samples were extracted with 0.1 N HCl, 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA (0.005 M Diethylenetriaminepentaacetic acid + 0.01 M Calcium cloride + 0.1 M Triethanolamine) and 1 M Mg(NO3)2, the latter of which extracts the exchangeable from of metald (Zn, Cd and Ni).

According to experiment results, Zn, Cd and Ni in all extraction increased with increasing rates of EDTA in the natural and metal amended soils.  相似文献   

3.
Total Zn in alluvial and calcareous soils (average 138 and 70 ppm respectively) was significantly related to their contents of CaCO3 (negatively), O.M. and clay (positively). Extracting Zn by Na2EDTA gave the highest values for both soil types. Total Cu contents varied widely from 26 to 111 ppm in alluvial and from 15 to 30 ppm in calcareous soils. They were negatively correlated with the CaCO3 contents. The pot experiments showed that EDTA(NH4)2CO3, Na2EDTA and DTPA are reasonable extractants for available Zn from both soil types. DTPA was efficient for all soils investigated, while Na2 EDTA and EDTA-citrate were specific for extracting Cu from calcareous soils.  相似文献   

4.
The bioavailability and plant uptake of heavy metals (HM), as well as finding the most reliable methods for the prediction of availability, continues to be one of the most crucial problems in agricultural and environmental studies. In agricultural soils from two regions in Kosovo, known for its metal pollution, we collected 60 soil and plant samples (wheat, corn, potatoes, and grass). Heavy metals were extracted from soil with aqua regia (pseudototal concentration), NH4OAc‐EDTA (potential bioavailable), and NH4NO3 (mobile fraction), plant samples were digested with HNO3/H2O2 (microwave assisted extraction). The pseudo total content of Cd, Pb, and Zn showed high value in Mitrovice (mean: Cd–2.92, Pb–570.15, and Zn–522.86 mg kg?1), whereas in Drenas region Ni and Cr showed high value with a mean 258.54 and 203.22 mg kg?1. Also, the potential bioavailability and mobile form of these metals were increased in Mitrovice (mean: Cd–1.59, Pb–217.05, Zn–522.86 mg kg?1, respectively Cd–0.17, Pb–0.64, and Zn–15.45 mg kg?1), compared to Drenas. Cd and Pb were elevated in potato tubers (mean Cd–0.48 and Pb–0.85 mg kg?1). The TF was higher for micronutrients (Zn and Cu) than for non‐essential metals (Cd and Pb). Multiple regression analysis showed a good model for prediction of Cd, Pb and Zn content in plant with significance 99.9%, whereas this model was not significant for Cu, Cr, and Ni. Soil pH played a significant role in the content of Cd and Zn in wheat and potato plants. Clay content also showed significance in Cd concentration in wheat and potato plants, while carbon content was significant for Cd in grass plants, as well as for Zn in wheat and grass plants.  相似文献   

5.
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   

6.
Soil‐plant transfer of metals is a nonlinear process. We therefore aimed at evaluating the potential of Freundlich‐type functions (cPlant = b × cSoila) to predict Cd, Cu, Pb, and Zn concentrations in wheat (Triticum aestivum L.) grain and leaf (cPlant) from soil concentrations (cSoil). 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#>  相似文献   

7.

Background, aim, and scope  

Various metals such as cationic metals (Cu, Pb, Zn) and anionic metals (As, Cr) often coexist in real soils, and normal soil washing techniques for the removal of cationic metals with a single-washing reagent make it rather difficult to simultaneously remove all of them. Oxalate could effectively remove anionic As and EDTA could effectively remove the cationic metals, so it was possible to remove all coexisting cationic and anionic metals by washing with the combination of Na2EDTA and oxalate. The objective of this study was to (1) discuss the possibility of removing five metals, As, Cd, Cu, Pb, and Zn, effectively from the soil by washing with Na2EDTA-combined oxalate; (2) optimized through the consecutive washing.  相似文献   

8.
Selection of appropriate plant species and rhizosphere manipulation to enhance metal uptake are considered key factors in the development of phytoextraction technologies. A pot trial was conducted with two contaminated soils to investigate the effect of EDTA and ammonium sulfate on the accumulation of heavy metals into shoots of the low‐biomass hyperaccumlator Thlaspi goesingense Hálácsy (Brassicaceae) and the high‐biomass non‐hyperaccumulating plant Amaranthus hybridus (Amaranthaceae). Upon application of 1 g EDTA (kg soil)—1 metal extractability with 1 M NH4NO3 increased substantially, whereas the application of (NH4)2SO4 was less effective. The EDTA treatment increased the heavy metal concentrations in both plant species, however, the difference to the control was larger for A. hybridus. EDTA enhanced shoot concentrations in A. hybridus grown on soil Arnoldstein from 32.7 mg kg—1 to 1140 mg kg—1 for Pb and from 3.80 mg kg—1 to 10.3 mg kg—1 for Cd. Cd concentrations in shoots of T. goesingense were also increased by EDTA application, however, a slight decrease was observed for Pb. T. goesingense accumulated 2840 mg Pb kg—1 without any treatment. This is the first report of Pb hyperacumulation by T. goesingense. A decrease of shoot Pb concentration was observed in T. goesingense upon treatment with ammonium sulfate. Although metal concentrations in the shoots were rather large and significantly increased upon application of EDTA, plant growth and heavy metal removal were still too small to obtain reasonable extraction rates in soils heavily polluted by metals. It should be also noted that metal lability largely increased in EDTA‐treated soils and this lability persisted for several weeks after the application of the chelating agent, which is likely to be associated with the risk of groundwater contamination.  相似文献   

9.
A screen-house experiment was conducted to study cadmium (Cd) and lead (Pb) phytoextraction using mustard and fenugreek as test crops. Cadmium was applied at a rate of 20 mg kg?1 soil for both crops, and Pb was applied at 160 and 80 mg kg?1 soil for mustard and fenugreek, respectively. The disodium salt of ethylenediamine tetraacetic acid (EDTA) was applied at 0, 0.5, 1.0, and 1.5 g kg?1 soil. Dry-matter yield (DMY) of both crops decreased with increasing rates of EDTA application. Application of 1.5 g EDTA kg?1 soil caused 23% and 70% declines in DMY of mustard and fenugreek shoots, respectively, in the soils receiving 20 mg Cd kg?1 soil. Similarly, in soil with 160 mg Pb kg?1 soil, application of 1.5 g EDTA kg?1 resulted in 25.4% decrease in DMY of mustard shoot, whereas this decrease was 55.4% in fenugreek grown on a soil that had received 80 mg Pb kg?1 soil. The EDTA application increased the plant Cd and Pb concentrations as well as shoot/root ratios of these metals in both the crops. Application of 1.5 g kg?1 EDTA resulted in a 1.50-fold increase in Cd accumulation and a 3-fold increase in Pb accumulation by mustard compared to the control treatment. EDTA application caused mobilization of Cd and Pb from carbonate, manganese oxide, and amorphous iron oxide fractions, which was evident from decrease in these fractions in the presence of EDTA as compared to the control treatment (no EDTA).  相似文献   

10.
Six fertilizer trials on calcareous soils in Saudi Arabia were conducted for the prediction of Zn deficiency in soybean (Glycine max L., var Merr). Zinc level before planting was tested by using 3 different extractants, i.e. DTPA, AB-DTPA and EDTA. Zinc was applied in the form of ZnSO4 · 7H2O at 0, 5, 10, 15, 20 and 40 kg Zn ha?1. Plant samples were taken at early bloom and tissue was analysed for Zn. Two methods were used to judge the critical deficiency level of Zn: Cate-Nelson and chisquare models. The critical level estimated according to the Cate-Nelson method for DTPA extractable soil Zn was 0.43 mg kg?1 in the growing season 1991. EDTA gave a much higher level (1.80 mg kg?1) and AB-DTPA gave an intermediate level (0.68 mg kg?1). Chi-square statistical procedure gave a very similar critical level of 0.66 mg kg?1 for AB-DTPA but lower for either DTPA (0.38 mg kg?1) or EDTA (1.32 mg kg?1). The critical level based for three growing seasons ranged from 0.25 to 0.68, 0.32 to 0.82 and 1.12 to 3.4 mg Zn kg?1 for DTPA, AB-DTPA and EDTA extractants, respectively. The values obtained by the linear regression equation with soybean leaf concentration were 0.45 and 0.70 mg Zn kg?1 for DTPA and AB-DTPA, respectively. Such values are very close to those determined by using the Cate-Nelson method. On the other hand, the value obtained for EDTA (1.15 mg Zn kg?1) was comparatively lower than that calculated by applying the Cate-Nelson method.  相似文献   

11.
Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate sodium ethylene diamine tetra acetic acid (Na2-EDTA) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) to determinate the relationships between extractable P and its uptake by crop in calcareous soils. Na2-EDTA and AB-DTPA was compared by the amounts of extracted P by analyzing soil samples collected from agricultural production areas. There were significant correlations between Na2-EDTA and AB-DTPA for soil test P based on soils collected from the agricultural field. Soil test P by both extractants was significantly correlated with plant P concentration. Na2-EDTA was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.  相似文献   

12.
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   

13.
Plants grown in salt‐affected soils may suffer from limited available water, ion toxicity, and essential plant nutrient deficiency, leading to reduced growth. The present experiment was initiated to evaluate how salinity and soil zinc (Zn) fertilization would affects growth and chemical and biochemical composition of broad bean grown in a calcareous soil low in available Zn. The broad bean was subjected to five sodium chloride (NaCl) levels (0, 10, 20, 30, and 40 m mol kg?1 soil) and three Zn rates [0, 5, and 10 mg kg?1 as Zn sulfate (ZnSO4) or Zn ethylenediaminetetraaceticacid (EDTA)] under greenhouse conditions. The experiment was arranged in a factorial manner in a completely randomized design with three replications. Sodium chloride significantly decreased shoot dry weight, leaf area, and chlorophyll concentration, whereas Zn treatment strongly increased these plant growth parameters. The suppressing effect of soil salinity on the shoot dry weight and leaf area were alleviated by soil Zn fertilization, but the stimulating effect became less pronounced at higher NaCl levels. Moreover, rice seedlings treated with ZnSO4 produced more shoot dry weight and had greater leaf area and chlorophyll concentration than those treated with Zn EDTA. In the present study, plant chloride and sodium accumulations were significantly increased and those of potassium (K), calcium (Ca), and magnesium (Mg) strongly decreased as NaCl concentrations in the soil were increased. Moreover, changes in rice shoot Cl?, Na+, and K+ concentrations were primarily affected by the changes in NaCl rate and to a lesser degree were related to Zn levels. The concentrations of Cl? and Na+ associated with 50% shoot growth suppression were greater with Zn‐treated plants than untreated ones, suggesting that Zn fertilization might increase the plant tolerance to high Cl? and Na+ accumulations in rice shoot. Zinc application markedly increased Zn concentration of broad bean shoots, whereas plants grown on NaCl‐treated soil contained significantly less Zn than those grown on NaCl‐untreated soil. Our study showed a consistent increase in praline content and a significant decrease in reducing sugar concentration with increasing salinity and Zn rates. However, Zn‐treated broad bean contained less proline and reducing sugars than Zn‐untreated plants, and the depressing impact of applied Zn as Zn EDTA on reducing sugar concentration was greater than that of ZnSO4. In conclusion, it appears that when broad bean is to be grown in salt‐affected soils, it is highly advisable to supply plants with adequate available Zn.  相似文献   

14.
High levels of phosphorus (P) often induce zinc (Zn) deficiency in plants grown on Zn-poor soils. We investigated P-induced Zn deficiency in durum wheat (Triticum durum L. ‘Carpio’) grown on 16 noncalcareous and 31 calcareous soils differing in levels of available (Olsen) P and available (diethylenetriaminepentaacetic acid (DTPA)-extractable) Zn using micropots. A completely randomized factorial design with two levels of P (0 and 40 mg P kg?1 soil) and Zn (0 and 3 mg Zn kg?1 soil), i.e. four treatments (‘control’, + P, + Zn, and + PZn), were used. Grain yield of control plants depended mainly on the Olsen P level. Phosphorus had a negative effect on yield in 6 soils with Olsen P/ZnDTPA > 25, and Zn a positive one in 5 soils with Olsen P/ZnDTPA > 50; and the + PZn treatment generally resulted in the highest yield. Grain Zn concentration of control plants was negatively correlated with growth and Olsen P. Calcareous soils were less sensitive to P-induced Zn deficiency than noncalcareous soils because phosphate is sorbed by calcite rather than being co-adsorbed with Zn on the Fe oxides. Co-application of P and Zn to soil at low and application of Zn at high Olsen P ensured both maximum yield and grain Zn bioavailability.  相似文献   

15.
Sulfuric acid leaching is a promising technique to extract toxic metals from polluted soils. The objective of this study was to define the optimum sulfuric acid leaching conditions for decontamination of the fine particle fraction (<125???m) of an industrial soil polluted by Cd (16.8?mg?kg?1), Cu (3,350?mg?kg?1), Pb (631?mg?kg?1) and Zn (3,010?mg?kg?1). Batch leaching tests in Erlenmeyer shake flasks showed that a soil pulp pH between 1.5 and 2.0 using a solid concentration (SC) ranging from 5 to 20?% is adequate to efficiently solubilize toxic metals. Leaching tests performed at different temperatures (20, 40, 60 and 80?°C) also revealed that it is not beneficial to heat the soil suspension during the leaching treatment. The application in a 1-L stirred tank reactor of five consecutive 1-h leaching steps at 10?% SC and ambient temperature, followed by three water washings steps resulted in the following metal extraction yields: 30?% As, 90?% Cd, 43?% Co, 7?% Cr, 88?% Cu, 75?% Mn, 26?% Ni, 18?% Pb and 86?% Zn. The decontaminated soil conformed to Quebec norms for commercial and industrial use of soil.  相似文献   

16.
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   

17.
Land pollution due to past mining activities is a major environmental issue in many European countries. The Aljustrel mine (SW Portugal), located in the western sector of the Iberian Pyrite Belt (IBP) presents a negative visual and environmental impact as a consequence of the mining activity that has developed since the Roman era. Its impacts are also a restraint on the life quality of the population. The exposure of pyrite and other sulphides to air are responsible for the pollution observed in soils, surface water and stream sediments. This paper investigates the pollution load of potential toxic elements in soil samples collected around the Aljustrel mining area. The aim is to assess the levels of soil contamination with respect to average concentrations of toxic elements in the region and to understand the partitioning and availability of pollutants in the area. The results showed severe soil contamination (mainly As, Cd, Cu, Pb and Zn). The concentrations of As (up to 3936 mg kg−1) and certain heavy metals (up to 5414 mg kg−1 Cu, 61·6 mg kg−1 Cd, 20 000 mg kg−1 Pb and 20 000 mg kg−1 Zn) are two orders of magnitude above the regional South Portuguese Zone (SPZ) background values. The median concentrations of As, Cd, Cu, Pb and Zn exceed the values established for world soils, the European Union, Portugal and Andalusia. The results suggest that the distribution patterns of Co, Cr and Ni element concentrations in the Aljustrel area are primarily influenced by the lithology and geochemistry nature of bedrock. The soil background of this geological domain is characterized by relatively high heavy metal contents, essentially derived from the parent rocks. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

18.
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.  相似文献   

19.
ABSTRACT

We studied (i) the pH buffer capacity (pHBC) of calcareous soils varied widely in calcite and texture, (ii) the contribution of soil properties to pHBC and (iii) the significance of using a model based on calcite dissolution to estimate the pHBC of calcareous soils. The pHBC of soils was measured by adding several rates of HCl to soils (100–6500 mM H+ kg–1), in a 0.01 M CaCl2 background and an equilibration time of 24 h. The pHBC (mM H+ kg–1 pH?1) varied from 55 to 3383, with the mean of 1073. The pHBC of the soils was strongly correlated with soil CaCO3 equivalent (calcite) (r = 0.94), sand (r = ?0.72), silt (r = 0.60), EC (r = 0.63), pH (r = 0.55), and weakly (r = 0.37) but significantly with clay content. The attained pHBC values indicated that calcite was probably the main buffer system in these soils. The chemical equilibrium model successfully predicted pH titration curves based on calcite dissolution, indicating buffering of acid inputs in the calcareous soils is dominated by calcite dissolution. The model can be used to simulate acidification of calcareous soils and to provide information for making environmental management decisions.  相似文献   

20.
A tri-state mining region, including parts of Missouri, Oklahoma, and Kansas, was the site of intense lead and zinc mining and smelting activity until the 1950's. A study was initiated to characterize the heavy-metal contamination of soils in this area. Water-soluble, an index of plantavailable, total, and sequentially extractable metals; organic, and total carbon; and saturated paste pH were determined for mine tailings and soil samples. Mine tailings contained 81 to 89 mg kg?1 total Cd, 1 150 to 1 370 mg kg?1 total Pb, and 11 400 to 13 700 mg kg?1 total Zn. Total concentrations in soil samples were 15 to 86 mg kg?1 Cd, 35 to 1 620 mg kg?1 Pb, and 99 to 18 500 mg kg?1 Zn; and, DTPA extractable concentrations ranged from 0.6 to 10 mg kg?1 Cd, 7.8 to 68 mg kg?1 Pb, and 33 to 715 mg kg?1 Zn. Samples were sequentially extracted to approximate the proportions of the metals in the sulfide, carbonate, organic, sorbed, and exchangeable fractions. For Zn and Cd, concentrations were greatest in the sulfide fraction followed by carbonate, organic, sorbed, and exchangeable. Lead followed the same pattern, except higher concentrations were observed in the sorbed than the organic fractions.  相似文献   

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