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1.
We assessed cadmium (Cd) and zinc (Zn) availability when applying reactive phosphate rock (RPR) in combination with lime and chicken manure on Indonesian acidic upland soils. Maize plants were grown on unamended soil and soils treated with several combinations of 2 tons dolomite ha–1, 2 tons of chicken manure ha–1, 1 ton ha–1 of RPRL (reactive phosphate rock containing 4 mg Cd kg–1 and 224 mg Zn kg–1), and 1 ton ha–1 of RPRH (RPR containing 69 mg Cd kg–1 and 745 mg Zn kg–1). In addition to its positive effect on plant yield, application of RPR in combination with chicken manure did not result in toxic Cd concentrations. Although liming is effective to reduce plant Cd concentrations, it results in more soil Cd accumulation and more plant Zn deficiency. Cadmium and Zn concentrations in shoots and grains can be predicted well from amounts extracted from the soil by 0.5 M ammonium (NH4) acetate + 0.02 M ethylenediaminetetraacetic acid (EDTA) at pH 4.65.  相似文献   

2.
A pot experiment was conducted to study the contribution of reactive phosphate rocks (RPRs) on the accumulation of Cd and Zn in 10 acid upland soils in Indonesia and shoots of Zea mays plants grown on these soils. Two types of RPR were used at a rate of 0.5 g (kg soil)–1: RPRL containing 4 mg Cd kg–1 and 224 mg Zn kg–1, and RPRH containing 69 mg Cd kg–1 and 745 mg Zn kg–1. Zea mays was harvested at 6 weeks after planting. The application of RPRH significantly increased the concentrations of Cd in the shoots. The application of this RPR also increased the amount of Cd which could be extracted by 0.5 M NH4‐acetate + 0.02 M EDTA pH 4.65 from the soils. More than 90% of the added Cd remained in the soil. As Zn is an essential element and the studied acid upland soils are Zn‐deficient, increased plant growth upon RPR application might be partly attributed to Zn present in the phosphate rock. However, more experiments are needed to confirm this hypothesis. The Cd and Zn concentrations and CEC of the soils were important soil factors influencing the concentrations of Cd and Zn in the shoots of maize plants grown on these soils.  相似文献   

3.
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   

4.
Abstract

Bell pepper (Capsicum annuum cv. Urfa Isoto) and cucumber (Cucumis sativus cv. Beith Alpha F1) were grown in pots containing field soil to investigate the effects of supplementary potassium phosphate applied to the root zone of salt‐stressed plants. Treatments were (1) control: soil alone (C); (2) salt treatment: C plus 3.5 g NaCl kg?1 soil (C + S); and (3) supplementary potassium phosphate: C + S plus supplementary 136 or 272 mg KH2PO4 kg?1 soil (C + S + KP). Plants grown in saline treatment produced less dry matter, fruit yield, and chlorophyll than those in the control. Supplementary 136 or 272 mg KH2PO4 kg?1 soil resulted in increases in dry matter, fruit yield, and chlorophyll concentrations compared to salt‐stressed (C + S) treatment. Membrane permeability in leaf cells (as assessed by electrolyte leakage from leaves) was impaired by NaCl application. Supplementary KH2PO4 reduced electrolyte leakage especially at the higher rate. Sodium (Na) concentration in plant tissues increased in leaves and roots in the NaCl treatment. Concentrations of potassium (K) and Phosphorus (P) in leaves were lowered in salt treatment and almost fully restored by supplementary KH2PO4 at 272 mg kg?1 soil. These results clearly show that supplementary KH2PO4 can partly mitigate the adverse effects of high salinity on both fruit yield and whole plant biomass in pepper and cucumber plants.  相似文献   

5.
The purpose of this study was to use zero‐valent iron nanoparticles (nZVI) and cellulosic wastes to reduce bioavailability of lead (Pb) and cadmium (Cd), and to establish Persian maple seedlings (Acer velutinum Bioss.) in contaminated soil. One‐year‐old seedlings were planted in pots filled with unpolluted soil. Lead [Pb(NO3)2] and Cd [Cd(NO3)2] were added with concentrations of 0 (Control), 100 (Pb100), 200 (Pb200), and 300 (Pb300) mg kg−1 and 10 (Cd10), 20 (Cd20), and 30 (Cd30) mg kg−1. Cellulosic wastes were mixed with soil at the same time of planting [four levels: 0, 10 (W1), 20 (W2), 30 (W3) g 100 g−1 soil]. The nZVI was prepared by reducing Fe3+ to Fe0 and injected to pots [four levels: 0, 1 (N1), 2 (N2), and 3 (N3) mg kg−1]. Height, diameter, biomass, tolerance index of seedlings, bioavailability of heavy metals in soil, and removal efficiency of amendments were measured. The highest values of seedling characteristics were observed in N3. The highest removal efficiency of Pb (Pb100: 81.95%, Pb200: 75.5%, Pb300: 69.9%) and Cd (Cd10: 92%, Cd20: 73.7%, Cd30: 68.5%) was also observed in N3. The use of nZVI and cellulosic waste could be a proper approach for seedling establishment in forests contaminated with heavy metals.  相似文献   

6.
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   

7.
A greenhouse experiment was designed to determine the cadmium (Cd) and lead (Pb) distribution and accumulation in parsley plants grown on soil amended with Cd and Pb. The soil was amended with 0, 5, 10 20, 40, 60, 80, and 100 mg Cd kg?1 in the form of cadmium nitrate [Cd(NO3)2] and 0, 5, 10, 50 and 100 mg Pb kg?1 in the form of lead nitrate [Pb(NO3)2]. The main soil properties; concentrations of the diethylenetriaminepentaacetic acid (DTPA)–extractable metals lead (Pb), Cd, copper (Cu), iron (Fe), zinc (Zn), and manganese (Mn) in soil; plant growth; and total contents of metals in shoots and roots were measured. The DTPA-extractable Cd was increased significantly by the addition of Cd. Despite the fact that Pb was not applied, its availability was significantly greater in treatments 40–100 mg Cd kg?1 compared with the control. Fresh biomass was increased significantly in treatments of 5 and 10 mg Cd kg?1 as compared to the control. Further addition of Cd reduced fresh weight but not significantly, although Cd concentration in shoots reached 26.5 mg kg?1. Although Pb was not applied with Cd, its concentration in parsley increased significantly in treatments with 60, 80, and 100 mg Cd g?1 compared with the others. Available soil Pb was increased significantly with Pb levels; nevertheless, the increase was small compared to the additions of Pb to soil. There were no significant differences in shoot and root fresh weights between treatments, although metal contents reached 20.0 mg Pb kg?1 and 16.4 mg Pb kg?1 respectively. Lead accumulation was enhanced by Pb treatments, but the positive effect on its uptake was not relative to the increase of Pb rates. Cadmium was not applied, and yet considerable uptake of Cd by control plants was evident. The interactive effects of Pb and Cd on their availability in soil and plants and their relation to other metals are also discussed.  相似文献   

8.
A pot experiment was conducted to investigate the influence of phosphate (P) application on diethylene triamine pentaacetic acid (DTPA)–extractable cadmium (Cd) in soil and on growth and uptake of Cd by spinach (Spinacia oleracea L.). Two soils varying in texture were contaminated by application of five levels of Cd (NO3)2 (0, 20, 30, 40, and 60 mg Cd kg–1). Three levels of KH2PO4 (0, 12, and 24 mg P kg–1) were applied to determine immobilization of Cd by P. Spinach was grown for 60 d after seeding. Progressive contamination of soils through application of Cd affected dry‐matter yield (DMY) of spinach shoot differently in the two soils, with 67% reduction of DMY in the sandy soil and 34% in the silty‐loam soil. The application of P increased DMY of spinach from 4.53 to 6.06 g pot–1 (34%) in silty‐loam soil and from 3.54 to 5.12 g pot–1 (45%) in sandy soil. The contamination of soils increased Cd concentration in spinach shoots by 34 times in the sandy soil and 18 times in the silty‐loam soil. The application of P decreased Cd concentration in shoot. The decrease of Cd concentration was higher in the sandy soil in comparison to the silty‐loam soil. Phosphorus application enhanced DMY of spinach by decreasing Cd concentration in soil as well as in plants. The results indicate that Cd toxicity in soil can be alleviated by P application.  相似文献   

9.
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   

10.
The geochemical reactivity of single superphosphate (SSP), triple superphosphate (TSP), phosphate rock (PR), partially acidulated phosphate rock (PAPR) and potassium dihydrogen phosphate (KH2PO4) was evaluated in an incubation trial. The soil was Anthrosols, Ap horizon (Sandy loam). Solubility equilibrium of phosphates was calculated by phosphate (PPot = logH2PO4 – pH) and calcium (CaPot = logCa + 2pH) potentials. Next, activity ratio (AR°) and Woodruff potential (ΔF) were considered for estimating phosphate dynamics in the soil. Data showed that phosphate potentials stressed on significant solubility process and varied accordingly to the rates of the fertilizers: ?5.50, ?4.81, ?4.47 and ?4.09 for 0, 50, 100 and 150 kg P ha?1. The values of the Woodruff potential (ΔF) varied widely from ?1929 to 8573 cal mol?1, i.e., from marginal supplying power in the case of the control treatment to very high supplying power for the TSP (Triple superphosphate). These findings are of practical value for the following reasons: TSP and KH2PO4 are recommended for quick and high P supply to plants; SSP and PAPR for moderate supply and finally PR for slow and low supply. Phosphorus efficiency should be treated with priority particularly for areas with intensive cropping and susceptibility to runoffs.  相似文献   

11.
《Journal of plant nutrition》2013,36(9):1635-1651
Abstract

Most agricultural soils in Iran are usually low in organic matter (OM). Therefore, increasing OM in these soils is of great concern. Environmental pollution caused by chemical fertilizers has created an interest in the integrated use of organic wastes with inorganic fertilizers. The main purpose of this greenhouse study was to evaluate the impact of two organic wastes and phosphorus (P) on the growth, and elemental composition of spinach (Spinacia oleracea L.) and soil chemical properties. Treatments consisted of four levels of municipal waste compost, MWC (0, 1, 2, and 4%), five rates of poultry manure, PM (0, 1, 2, 3, and 4%), and three P levels (0, 25, and 50 mg kg?1 as KH2PO4). Application of P and MWC alone or in combination significantly increased the top dry weight of spinach. However, spinach growth was markedly increased up to 3% PM and suppressed with the higher rate, probably due to an excess of soluble salts in the soil. Moreover, the enhancing influence of P on spinach seedling growth was more pronounced at lower levels of MWC and PM. Plant P concentration tended to increase with increasing P, MWC, and PM application rates, whereas nitrogen (N) concentration was only affected by the two organic wastes treatment. Manganese (Mn) concentrations decreased, and copper (Cu), lead (Pb), and cadmium (Cd) increased by soil P application. However, P addition significantly decreased zinc (Zn) concentration only in MWC-treated spinach. Spinach plants enriched with either of the two biosolids accumulated more Mn, Zn, Pb, Cd, chloride (Cl), and sodium (Na) than control plants. Furthermore, spinach grown on MWC-amended soil contained higher Mn, Zn, Cu, and Pb and lower N, Cl, and Na than those raised on PM-treated soil. Postharvest soil sampling indicated that application of the two biosolids significantly increased concentration of soluble salts, (ECe), OM, TN, NaHCO3-extractable P, and DTPA-extractable iron (Fe), Mn, Zn, Cu, Pb, and Cd.  相似文献   

12.
The activity of zinc (Zn) ions in the soil solution bathing plant roots is controlled by the simultaneous equilibrium of several competing reactions, such as surface exchange, specific bonding, lattice penetration, precipitation reactions, and the processes leading to the desorption of surface and lattice-bound ions. Desorption of Zn in 15 calcareous soils from southern Iran, treated with 10 mg Zn kg?1 soil as zinc sulfate (ZnSO4·7H2O) and 100 mg phosphorus (P) kg?1 soil as calcium phosphate [Ca(H2PO4)2H2O] and then equilibrated and extracted with diethylentriaminepentaacetic acid (DTPA), was studied in this experiment. The results were fitted to zero-order, first-order, second-order, third-order, parabolic diffusion, two-constant rate, Elovich, and simple Elovich kinetic models. Two-constant rate, simple Elovich, and parabolic diffusion models were determined to best describe Zn-desorption kinetics. Zinc desorption increased as Zn was applied but decreased with applied P.  相似文献   

13.
Along a heavy metal deposition gradient, caused by a Cu smelter, heavy metal concentrations, partitioning, and storage in forest and arable soils were examined. We sampled organic and mineral soil horizons (0—50 cm) at ten pairs of forest and arable sites derived from the same parent material. A-horizons were extracted with a seven-step sequence; O- and subsoil horizons were digested with strong acids (HNO3/HClO4). We found high concentrations of Cd (up to 17.38 mg kg—1 in the O horizons/up to 2.44 mg kg—1 in the A horizons), Cu (8437/415), Pb (3343/126), and Zn (1482/637) which decreased exponentially with distance from the smelter and with soil depth. The metal concentrations in the organic layers indicate that the average transport distance decreases in the order Cd > Zn > Pb > Cu. With regard to metal partitioning, NH4NO3- + NH4OAc-extractable forms in the A horizons were most affected by the deposition being more pronounced under forest. In the uppermost 50 cm of the four soils nearest to the smelter two to four times higher Cd, Cu, Pb, and Zn storages were found in forest than in arable soils. At greater distance, the higher deposition onto forest soils due to the scavenging effect of the canopy obviously was compensated by stronger leaching.  相似文献   

14.
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   

15.
A greenhouse experiment was conducted to investigate the immediate effect of application of mono‐ammonium phosphate (MAP), single superphosphate (SSP), and triple superphosphate (TSP) fertilizers containing varying concentrations of Cd on (1) chemical speciation of Cd and Zn in soil solution by chemical‐equilibrium calculations (MINEQL+4.6 model), (2) growth of barley plants, (3) concentrations of Cd, P, and Zn in soil solution and plant tissue, as well as total plant accumulation of Cd, P, and Zn, and (4) monitoring pH and element changes during incubation periods following phosphate application. Results show that, in general, the pH of soil solution increased during the first 40 d of incubation, then declined. Also, at the end of incubation period, pH of soil solution was affected by fertilization source and fertilization rate. The concentration of Cd in soil solution changed with time. Phosphate fertilization (p < 0.05) or fertilizer source (p < 0.05) showed consistent effects. Also, the application of phosphate fertilizers with three rates significantly increased Zn concentrations in soil solution during the first half (0–30 d) of incubation period and then decreased but still more than in the control. In general, application of different sources of phosphate at 100 g kg–1 did not change the dominant forms of Cd in soil solution during all incubation time intervals. Speciation of Zn in the control after 30 d of incubation had changed, in comparison to 10 d of incubation, and the dominant forms were Zn2+, ZnOH+, ZnHCO3, ZnCO3(aq), and Zn(OH)2(aq). Adding phosphate fertilizer significantly increased both shoot and root dry weight compared to control, indicating P was a growth‐limiting factor in the control plants. The Zn concentrations in shoot and root were lower in the TSP‐ and SSP‐fertilizers treatment than those in the MAP and fertilizer treatments at all rates of fertilization. Adding phosphate increased the Cd : Zn and P : Zn ratios in the shoot and root tissue, with the effect being greater with increasing fertilization rate. Phosphate fertilization greatly increased the total accumulation of Cd of barley compared with the control plants (p < 0.001), with the effect being greater with increasing fertilization rate. Source and rate of fertilizers, and their interactions had significant effect (p < 0.05) on Cd accumulation in the whole plant.  相似文献   

16.

Purpose

The present research aimed to assess the influence of two phosphorous (P) amendments on metal speciation in rhizosphere soil and the soil–plant transfer of metals.

Materials and methods

Complementary experiments were performed: field experiments on a contaminated cultivated soil and laboratory experiments on an uncultivated contaminated soil to highlight the mechanisms involved in metal-phosphorous interactions. In laboratory experiment, P amendments were added at 120 mg P/kg of soluble KH2PO4 amendment and 9,000 mg P/kg of solid Ca5(PO4)3OH amendment.

Results and discussion

Field-culture results showed the possible food-chain contamination due to Pb, Cd, Cu, and Zn phytoaccumulation by pea and mustard plants from a cultivated agricultural soil. Moreover, P-metal complexes were observed by microscopy in the rhizosphere soil. In laboratory experiments, the application of P amendments significantly increased Pb and Zn level in rhizosphere soil compared to control. Phosphate amendments significantly increased metal-P fraction and decreased “oxides” and “organic matter” fractions of Pb and Zn. Soluble-P amendment was more effective than solid P amendment in changing Pb and Zn speciation. The changes in metal speciation are higher in the rhizosphere soil of pea than tomato. Application of P amendments increased Pb and Zn TF root/soil but decreased TF shoot/root.

Conclusions

The effectiveness of in situ metal immobilization technique varies with the type and quantity of applied P amendment as well as plant and metal type.  相似文献   

17.
Abstract

Heavy‐metal inhibition of nitrification in soils treated with reformulated nitrapyrin was investigated. Clarion and Okoboji soils were treated with ammonium sulfate [(NH4)2SO4] and a nitrification inhibitor. Copper(II) (Cu), Zinc(II) (Zn), Cadmium(II) (Cd), or Lead(II) (Pb) were added to each soil. A first‐order equation was used to calculate the maximum nitrification rate (K max), duration of lag period (t′), period of maximum nitrification (Δt), and the termination period of nitrification (t s). In the Clarion soil, the K max decreased from 12 mg kg?1 d?1 without the nitrification inhibitor to 4, 0.25, 0.86, and 0.27 mg kg?1 d?1, respectively, when the inhibitor and Cu, Zn, Pb, or Cd were applied. In the Okoboji soil, K max decreased from 22 mg kg?1 d?1 with no inhibitor to 6, 3, 4, and 2 mg kg?1 d?1, respectively, when an inhibitor and Cu, Zn, Pb, or Cd were added. The t′ varied from 8 to 25 d in the Clarion soil and from 5 to 25 d in the Okoboji soil, due to addition of Cu, Zn, Pb, or Cd and the inhibitor.  相似文献   

18.

Purpose

The combined contamination of Pb, Zn, Cu, Cd, and As in the soils near lead/zinc mine waste posed a potential threat to the surrounding environment. Mitigation methods are needed to reduce the environmental risk. The aims of this paper were to evaluate the feasibility and efficiency of different forms of phosphates in remediating combined contamination caused by multi-metals and arsenic near the lead/zinc mining tailings.

Materials and methods

The tested soil was taken from a clayey illitic thermic typic epiaquepts soil (depth of 0–20 cm) near a lead and zinc mine tailing, located in Shaoxing, Zhejiang Province, China. Four pure chemical reagents, K2HPO4, Ca(H2PO4)2.2H2O, Ca3(PO4)2, and Ca5(PO4)3OH, were added to the soil in solution form as the trace metal stabilizing additives at a P application rate equivalent to 2,283 mg P/kg-soil and P/Pb molar ratio of 1. Shifts in trace metal speciation were determined using sequential extraction procedures and relative toxicities were evaluated using the standard EPA toxicity characteristic leaching procedure (TCLP).

Results and discussion

The addition of K2HPO4, Ca3(PO4)2, Ca5(PO4)3OH, and Ca(H2PO4)2.2H2O in the contaminated soil at the phosphorus application rate 2,283 mg P/kg-soil reduced Pb concentrations in TCLP extraction solution from 90.47 to 56.05, 83.80, 67.78, and 86.32 mg/kg (38.0, 7.36, 25.1, and 4.59% reduction), respectively. Sequential extraction analysis showed that phosphate treatments caused the transformation of easily available trace metal species to more stable forms. However, TCLP As in the soil increased from its initial value of 0.23 to 2.1, 0.70, 0.67, and 0.77 mg/kg, respectively, for the four treatments. The TCLP leachable As concentration of the K2HPO4-treated soil was about nine times of that from the untreated soil.

Conclusions

The addition of K2HPO4, Ca3(PO4)2, Ca5(PO4)3OH, and Ca(H2PO4)2.2H2O were effective in reducing water soluble and exchangeable Pb, Zn, Cu, and Cd, and minimizing TCLP-extractable Pb, Zn, and Cu. The sequential extraction test and the TCLP indicate that Ca5(PO4)3OH treatment has a higher potential in immobilizing Pb, Zn, Cu, and Cd, though a slight enhancement of As mobility, comparing with other phosphate treatments.  相似文献   

19.
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   

20.
A greenhouse experiment was conducted to examine whether foliarly applied potassium + phosphorus (K + P) in the form of monopotassium phosphate (KH2PO4) could mitigate the adverse effects of salt stress on sunflower plants. There were two levels of root-applied salt [0 and 150 mM of sodium chloride (NaCl)], and varying levels of KH2PO4 [(NS (no spray), WS (spray of water), 5 + 4, 10 + 8, 15 + 12, and 20 + 16 mg g?1 K + P, pH 6.5] applied foliarly to 18-day old non-stressed and salt stressed sunflower plants. Salt stress adversely affected the growth, yield, photosynthetic capacity, and accumulation of mineral nutrients in the sunflower plants. However, varying levels of foliar applied KH2PO4 proved to be effective in improving growth and yield of sunflower under salt stress. The KH2PO4 induced growth in sunflower was found to be associated with enhanced photosynthetic capacity, water use efficiency and relative water contents.  相似文献   

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