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1.
This study evaluated cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) sorption characteristics of three tropical soils. Data obtained conformed to Freundlich sorption model and the S-shaped isotherm curve. Sorption efficiency of Zn and Pb were highest in alkaline soil while slightly acid soil had the highest Cd and Cu sorption efficiency for monometal sorption. In competitive sorption, metals were more sorbed in slightly acid soil while the least efficiency was recorded in acid soil. Distribution coefficient; Kd (average across soil types) in monometal sorption followed the order: Pb > Zn > Cd > Cu. For competitive sorption, the order was Zn > Pb > Cu > Cd. When in competition, Cd was preferentially sorbed in slightly acid and alkaline soils and Zn for acid soil. Conclusively, lead is more in equilibrium solution when in competition with Cd, Zn and Cu making it potential agent of soil and groundwater pollution.  相似文献   

2.
Abstract

Laboratory experiments were carried out to evaluate lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) sorption‐desorption by three soils of contrasting characteristics. Talamanca (silt loam, montmorillonite, Calcic Haploxeralfs), Mazowe (clay, kaolinite, Rhodic Kandiustalf), and Realejos (sandy silt loam, allophane, Typic Hapludands). A second objective was to study the effect of nitriloacetic acid (NTA) on the sorption process. The Talamanca soil, which had a native pH of 6.4 and presented the highest effective cation exchange capacity (ECEC), sorbed more of each of the metal tested than did the other two soils. When the other two soils were compared metal sorption was also related to pH and ECEC. The very low sorption capacity showed by Realejos may be attributed to the low net surface negative charge density of this soil, arising from its allophanic nature. A common feature of the three soils was the relative strong sorption of both Pb and Cu relative to Cd and Zn with Pb showing the highest sorption levels. The selectivity sequences of metals retention were Pb>Cu>Zn>Cd for Talamanca soil, Pb>Cu>Zn≈Cd for Mazowe, and Pb>Cu>Cd>Zn for Realejos. Metal desorption values were low. The order of metal desorption (Cd≈Zn>Cu>Pb) was the same for the three soils studied. Quantitative differences observed in the extractability of the sorbed metals between the soils (Realejos>Mazowe>Talamanca) indicated that soil properties which enhanced metal sorption contributed at the same time to slow down the backward reaction. The addition of NTA to the soil suspension significantly depressed metal sorption by the three soils investigated. Compared with the free ligand system Pb, Cu, Zn, and Cd sorption in the presence of NTA decreased roughly 50%.  相似文献   

3.

Purpose

Our main aim objective was to evaluate the transfer of Cd, Cr, Cu, Ni, Pb and Zn to barley (Hordeum vulgare) grown in various soils previously amended with two sewage sludges containing different concentrations of heavy metals. This allowed us to examine the transfer of heavv metals to barley roots and shoots and the occurrence of restriction mechanisms as function of soil type and for different heavy metal concentration scenarios.

Material and methods

A greenhouse experiment was performed to evaluate the transfer of heavy metals to barley grown in 36 agricultural soils from different parts of Spain previously amended with a single dose (equivalent to 50 t dry weight ha?1) of two sewage sludges with contrasting levels of heavy metals (common and spiked sludge: CS and SS).

Results and discussion

In soils amended with CS, heavy metals were transferred to roots in the order (mean values of the bio-concentration ratio in roots, BCFRoots, in brackets): Cu (2.4)?~?Ni (2.3)?>?Cd (2.1)?>?Zn (1.8)?>?Cr (0.7)?~?Pb (0.6); similar values were found for the soils amended with SS. The mean values of the soil-to-shoot ratio were: Cd (0.44)?~?Zn (0.39)?~?Cu (0.39)?>?Cr (0.20)?>?Ni (0.09)?>?Pb (0.01) for CS-amended soils; Zn (0.24)?>?Cu (0.15)?~?Cd (0.14)?>?Ni (0.05)?~?Cr (0.03)?>?Pb (0.006) for SS-amended soils. Heavy metals were transferred from roots to shoots in the following order (mean values of the ratio concentration of heavy metals in shoots to roots in brackets): Cr (0.33)?>?Zn (0.24)?~?Cd (0.22)?>?Cu (0.19)?>?Ni (0.04)?>?Pb (0.02) for CS-amended soils; Zn (0.14)?>?Cd (0.09)?~?Cu (0.08)?>?Cr (0.05)?>?Ni (0.02)?~?Pb (0.010) for SS-amended soils.

Conclusions

Soils weakly restricted the mobility of heavy metals to roots, plant physiology restricted the transfer of heavy metals from roots to shoots, observing further restriction at high heavy metal loadings, and the transfer of Cd, Cu and Zn from soils to shoots was greater than for Cr, Ni and Pb. Stepwise multiple linear regressions revealed that soils with high sand content allowed greater soil-plant transfer of Cr, Cu, Pb and Zn. For Cd and Ni, soils with low pH and soil organic C, respectively, posed the highest risk.  相似文献   

4.
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   

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.
Batch experiments were performed to study metal sorption by pine bark and algae-treated bark. The biosorption of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), cobalt (Co), and nickel (Ni) in synthetic multimetal aqueous solutions was studied as a function of metal content in solution, and amount and size of bark particles used for sorption. Influence of water hardness (Ca2+ only was tested) on the metal sorption process was also evaluated. Metal uptake from solutions with high heavy metal content (i.e. 10× the limit for leachate from landfills) was found to be independent of Ca2+ concentration. At low metal content in solution (i.e. 1× the limit for leachate from landfills), uptake of Cu, Zn, Ni, and Cd decreased with increasing Ca2+ content in water. Microalgae-treated bark was found to increase the metal sorption efficiency. Air-drying of bark-entrapped algae was shown to be the best method for sorbent drying. In general, the green algae, Chlorella sp. and Pseudokirchneriella subcapitata showed the best results in metal uptake. Sorption of Co, Zn, Ni, and Cd from solution with high levels of both heavy metals and calcium increased by almost 50% with algae treatment of bark was applied. At low levels of metals and calcium content, 100% uptake of Cu and Pb in water was observed. Uptake of other metals from solution with low metal and Ca content was relatively high (50–60%). Low pH (pH 3.0) had no influence on metal sorption from solutions with high metal content. For solutions with low metal content a decrease of metal uptake by 10–15% was observed for all the metals but Pb. Thus, the treatment of bark with microalgae was successful and influenced positively the uptake capacity of the bark.  相似文献   

7.
Heavy metal content of roots and shoots of vines (Vitis vinifera L.) after fertilization with garbage-sewage-sludge-compost The enrichment of Zn, Cu, Pb, Cd, Co, Ni and Cr from garbage-sewage-sludge-compost in vineyard soils, vines and must was studied in field-and pot-experiments. The following results were obtained: 1. In a field experiment, in which garbage-sewage-sludge-compost was applied, a marked soil enrichment of Zn, Cu, Pb, Cd and Cr was found. It was most evident at the 0–20 cm depth but also obvious at the 40–60 cm depth thus indicating downward migration. The soil was not enriched with Co and Ni. The heavy metal content of leaves, berries and must of riesling vines did not increase on the plots treated with garbage-sewage-sludge-compost. 2. In a pot trial, using an acid and an alkaline soil each mixed with garbage-sewage-sludge-compost, it was observed that only the uptake of Zn and Cu increased into the leaves, tendrils and wood of the riesling cuttings. In relation to the content of the substrate, the heavy metals were detected in the roots percentually in the following order: Cu, Cd > Zn > > Pb, Co, Ni, Cr The root contents were mostly substantially higher than those of the shoot. The migration from root to shoot decreased in the following percentual order: Zn > Cu > Cd, Pb 3. The heavy metal content decreased considerably from the roots to the upper plant organs. This was reflected in low concentrations of heavy metals in the vine must.  相似文献   

8.
Retention of Cd, Cu, Pb and Zn by Wood Ash, Lime and Fume Dust   总被引：2，自引：0，他引：2  
Heavy metals are of interest due to their deleterious impacts on both human and ecosystem health. This study investigated the effectiveness of wood ash in immobilizing the heavy metals Pb, Cd, Cu and Zn from aqueous solutions. The effects of initial metal concentrations, solution pH, ash dose and reaction time on metal sorption, as well as the metal sorption mechanisms were studied. To investigate the effect of initial metal concentrations, solutions containing Cd, Zn (25, 50, 75, 100 or 125 mg L?1), Cu (25, 50, 75, 100, 125, 150 or 175 mg L?1) or Pb (250, 500, 750, 1000, 1250, or 1500 mg L?1) were reacted with 10 g L?1 ash for two hours. For the effect of pH, solutions containing 100 mg L?1 of Cd, Cu or Zn or 1500 mg L?1 of Pb were reacted with 15 g L?1 ash over a pH range of 4 to 7. The wood ash was effective in immobilizing the four metals with a sorption range of 41–100 %. The amounts of metals retained by the ash followed the order of Pb > Cu > Cd > Zn. As expected, absolute metal retention increased with increasing initial metal concentrations, solution pH and ash dose. Metal retention by the ash exhibited a two-phase step: an initial rapid uptake of the metal followed by a period of relatively slow removal of metal from solution. Metal retention by the ash could be described by the Langmuir and Freundlich isotherms, with the latter providing a better fit for the data. Dissolution of calcite /gypsum minerals and precipitation of metal carbonate/sulfate like minerals were probably responsible for metal immobilization by the ash in addition to adsorption.  相似文献   

9.
Interaction between an acidic mine water and an agricultural soil material   总被引：1，自引：0，他引：1  
A. Chen  W. Lu  Y. Ma  Y. Bai  H. Chen  J. Li 《Geoderma》2008,148(2):213-219
A column filtering experiment was conducted to investigate interaction between an acidic mine water and an agricultural soil material during percolation of the mine water through the soil column. The results show that the mine water-borne mineral acid, Cu, Pb, Zn and Cd was markedly held by the soil during the earlier stage of the experiment. Approximately 1/3 of the retained acid was only physically held by the soil while the remaining 2/3 of the retained acid was either physiochemically or chemically bound to soil colloids. There was a tendency that the retained acid decreased with increasing depth of the soil column. Except for Cd, the capacity of soil to remove these heavy metals from the mine water persisted longer, compared to mineral acid. In contrast with mineral acid, the concentration of retained heavy metals increased with increasing depth, suggesting that these metal ions are less competitive than major acidic cations such as Al3+, H+ and Fe3+ for available adsorption sites in the upper soil layers. Mine water-borne Cu, Cd and Pb were immobilized predominantly in exchangeable and oxide-bound forms while mine water-borne Zn was immobilized mainly in carbonate- and organic-bound forms. During mine water infiltration, some soil-borne metals were mobilized and leached out of the soil under acidic conditions during the latter stage of filtration operations. Unlike Cu, Pb, Zn and Cd, mine water-borne Fe was transformed into colloidal Fe oxides/hydroxides which were carried by the downflowing water. A large proportion of mine water-borne Mn was only physically held, probably not necessarily in soluble forms but in colloidal forms.  相似文献   

10.
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   

11.
Behaviour of heavy metals in soils. 2. Extraction of mobile heavy metals with CaCl2 and NH4NO3 156 soil samples from arable fields, grassland and forest stands were analysed for the CaCl2? and NH4NO3? extractable contents of Cd, Zn, Mn, Cu and Pb. The average amounts of Cd, Zn, Cu and Pb extracted with CaCl2 are higher compared with NH4NO3 whereas the relation for Mn is vice versa. The proportion of the NH4NO3? extractable contents in percent of the CaCl2? extractable contents of Cd, Zn and Pb decrease with increasing pH, whereas the contents of Mn and Cu increase. Inspite of a differing extraction behaviour of the two salt solutions the CaCl2? and NH4NO3? extractable amounts of Cd, Mn, Zn und Pb are highly correlated and can be converted one into another. The mobile (CaCl2, NH4NO3) proportion of the corresponding total, EDTA and DTPA heavy metal contents is in close relation to the pH of the soils. Using CaCl2 solution the threshold pH values for an increasing mobility decrease in the order Cd > Mn > Zn > Cu > Pb, using NH4NO3 as extractant the order is Mn > Cd > Zn > Cu > Pb. In the case of CaCl2 as extractant soluble chloro-Cd-complexes will be formed so that the Cd mobility in soils will be overestimated in most cases.  相似文献   

12.
A total of 50 farmland soil samples were collected from the Yanqi County, Xinjiang, China, and the concentrations of eight heavy metal elements (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) were determined by standard methods. The spatial distribution, pollution level and ecological risk status of heavy metals were analyzed based on GIS technology, the Geo-accumulation Index (Igeo), the Pollution Load Index (PLI) and the Potential Ecological Risk Index (RI). Results indicated that: (1) The average contents of Cd, Cr, Ni, Pb, and Zn of farmland soils exceeded the background values of irrigation soils in Xinjiang by 1.5, 1.40, 1.33, 2.63, and 4.92 times, respectively. Cd showed a no-pollution level, Zn showed a partially moderate pollution level, Pb showed a slight pollution level, and Cr, Cu, As, Mn, and Ni showed no-pollution level, compared to the classification standard. The PLI values of heavy metal elements of farmland soils varied from 0.83 to 1.89, with an average value of 1.29, at the moderate pollution level. (2) The Individual Potential Ecological Risk Index for heavy metals in the study area was ranked in the order of: As > Ni > Cu > Cd > Pb > Cr> Zn. The RI values of heavy metals of farmland soils varied from 3.45 to 11.34, with an average value of 6.13, at the low ecological risk level. (3) Cu and Mn of farmland soils were mainly originated from the soil parent material and topography of the study area. As, Cd, Ni and Pb were mainly originated from human activities, and Cr and Zn may originated from both natural and anthropogenic factors in the study area.  相似文献   

13.

Purpose

Heavy metal distribution in soils is affected by soil aggregate fractionation. This study aimed to demons trate the aggregate-associated heavy metal concentrations and fractionations in “sandy,” “normal,” and “mud” soils from the restored brackish tidal marsh, oil exploitation zone, and tidal mudflat of the Yellow River Delta (YRD), China.

Materials and methods

Soil samples were sieved into the aggregates of >2, 0.25–2, 0.053–0.25, and <0.053 mm to determine the concentrations of exchangeable (F1), carbonate-bound (F2), reducible (F3), organic-bound (F4), and residual fraction (F5) of Cd, Cr, Cu, Ni, Pb, and Zn.

Results and discussion

The 0.25–2 mm aggregates presented the highest concentrations but the lowest mass loadings (4.23–12.18 %) for most metal fractions due to low percentages of 0.25–2 mm aggregates (1.85–3.12 %) in soils. Aggregates <0.053 mm took majority mass loadings of metals in sandy and normal soils (62.04–86.95 %). Most soil aggregates had residual Cr, Cu, Ni, Zn, and reducible Cd, Pb dominated in the total Cd, Cr, Cu, Ni, Pb, and Zn concentrations. Sandy soil contained relatively high F4, especially of Cu (F4) in 0.25–2 mm aggregates (10.22 mg kg?1), which may relate to significantly high organic carbon contents (23.92 g kg?1, P?<?0.05). Normal soil had the highest total concentrations of metals, especially of Cu, Ni, and Pb, which was attributed to the high F3 and F5 in the <0.053 mm aggregates. Although mud soil showed low total concentrations of heavy metals, the relatively high concentrations of bioavailable Cd and Cu resulted from the relatively high Cd (F2) and Cu (F2) in the >2 mm aggregates indicated contribution of carbonates to soil aggregation and metal adsorption in tidal mud flat.

Conclusions

Soil type and aggregate distribution were important factors controlling heavy metal concentration and fractionation in YRD wetland soil. Compared with mud soil, normal soil contained increased concentrations of F5 and F3 of metals in the 0.053–0.25 mm aggregate, and sandy soil contained increased concentrations of bioavailable and total Cr, Ni, and Zn with great contribution of mass loadings in the <0.053 mm aggregate. The results of this study suggested that oil exploitation and wetland restoration activities may influence the retention characteristics of heavy metals in tidal soils through variation of soil type and aggregate fractions.
  相似文献   

14.
Phosphorus （P） is necessary for growth and nitrogen fixation, and thus its deficiency is a major factor limiting legume production in most agricultural soils. The effect of phosphorus supply on nodule development and its role in soybeans （Glycine max L.） was studied in a nutrient solution. Plants were inoculated with Bradyrhizobium japonicum and grown for 35 days in a glasshouse at a day and night temperature of 25℃ and 15℃, respectively. Although increasing P supply increased the concentrations of P and N in the shoots and roots, the external P supply did not significantly affect the P concentration in the nodules, and the N fixed per unit nodule biomass decreased with increasing P supply. The nitrogen content in the shoots correlated well with the P content （r=0.92＊＊）. At an inoculation level of 10^2 cells mL^-1, the P supply did not affect the number of nodules; however, at inoculation levels of 10^3.5 and 10^5 cells mL^-1, increasing P supply increased both the number and size of nodules. Irrespective of the inoculation level, increasing P supply increased the nodule biomass relative to the biomass of the host plant. It is suggested that the P deficiency specifically inhibited the nodule development and thereby the total N2 fixation.  相似文献   

15.
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   

16.
The amount of sorbed metal ion released from CaC03 by 16 different extractants was found to vary with the chemical nature of the solution and the metal ion involved. In general, acid solutions dissolved a high proportion of both substrate and Cu, Ph, Cd coatings; complexing agents dissolved the same coatings but left most of the calcite; and competing cations (e.g. NH4 +, Ca2+) displaced primarily chemisorbed Cd and Cu. In Zn studies, little metal ion was retrieved by any extractant due to the limited solubility of the coatings formed at pH < 7.7. The diverse behavior observed in the sorption studies has been interpreted in terms of solubility and absorption equilibria. The pH of the CaC03 suspensions was high enough to precipitate all added Pb as hydroxy species, and excess Cu tended to precipitate at pH > 6.4 if one increased the soluble carbonate level (e.g. by adding acid). Unlike Cd and Cu, Zn was not chemisorbed; it formed sparingly soluble compounds such as ZnC03.2Zn(OH)2, with excess coming out as Zn(OH)2 at pH > 7.7. The significance of the results in respect to the mobility of metal ions in calcareous soils, and the evaluation of available levels, has been considered.  相似文献   

17.
The ecological dose (ED50) of Cd on alkaline and acid phosphatase activity and the ATP content of three contrasting forest soils was measured with or without Cu and Zn to assess the additive toxic effects of these two metals. Soils polluted with Cu and/or Zn were treated with increasing Cd concentrations to give the following metal combinations: Cd, Cd+Cu, Cd+Zn and Cd+Cu+Zn. Alkaline and acid phosphatase activities and ATP content of the three soils were analysed 4 h, 7 and 28 days after the metal additions. The ED50 values were obtained by interpolating the enzyme activities or ATP data with a kinetic model and the goodness of fit was satisfactory.Generally, the ED50 values of both acid and alkaline phosphatase activities for Cd were lower (higher toxicity) with than without Cu and Zn and the effect of Cu and Zn was particularly adverse when these two metals were both added to soils. The alkaline phosphatase was more sensitive in the acid and neutral soil whereas the acid phosphatase was more sensitive in the alkaline soil. Both phosphatase activities and the ATP content were more sensitive in the sandy than in the finer textured soils. The ATP content was less sensitive to the additive effects. Increasing toxicity was observed during the incubation.Analysis of 1 M NH4NO3-extractable Cd, Cu and Zn revealed that Cd competed with Zn for the adsorption sites but not with Cu. However, the lower ED50 values for Cd of the two phosphatase activities and of the ATP content in the presence of heavy metal combinations could be not explained by the heavy metal solubility data. It is concluded that the ED50 may be a sensitive tool for assessing additve toxic effects to soil biochemical parameters.  相似文献   

18.
Abstract

Agricultural use of sewage sludges can be limited by heavy metal accumulations in soils and crops. Information on background levels of total heavy metals in soils and changes in soil metal content due to sludge application are; therefore, critical aspects of long‐term sludge monitoring programs. As soil testing laboratories routinely, and rapidly, determine, in a wide variety of agricultural soils, the levels of some heavy metals and soil properties related to plant availability of these metals (e.g. Cu, Fe, Mn, Zn, pH, organic matter, texture), these labs could participate actively in the development and monitoring of environmentally sound sludge application programs. Consequently, the objective of this study was to compare three soil tests (Mehlich 1, Mehlich 3, and DTP A) and an USEPA approved method for measuring heavy metals in soils (EPA Method 3050), as extractants for Cd, Cu, Ni, Pb and Zn in representative agricultural soils of Delaware and in soils from five sites involved in a state‐monitored sludge application program.

Soil tests extracted less than 30% of total (EPA 3050) metals from most soils, with average percentages of total metal extracted (across all soils and metals) of 15%, 32%, and 11% for the Mehlich 1, Mehlich 3, and DTPA, respectively. Statistically significant correlations between total and soil test extractable metal content were obtained with all extractants for Cu, Pb, and Zn, but not Cd and Ni. The Mehlich 1 soil test was best correlated with total Cu and Zn (r=0.78***, 0.60***, respectively), while the chelate‐based extractants (DTPA and Mehlich 3) were better correlated with total Pb (r=0.85***, 0.63***). Multiple regression equations for the prediction of total Cu, Ni, Pb, and Zn, from soil test extractable metal in combination with easily measured soil properties (pH, organic matter by loss on ignition, soil volume weight) had R2 values ranging from 0.41*** to 0.85***, suggesting that it may be possible to monitor, with reasonable success, heavy metal accumulations in soils using the results of a routine soil test.  相似文献   

19.
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20.
Electron microprobe studies on soil samples with varying heavy metal contamination. 2. Contents of heavy metals and other elements in aggregations of humic substances, litter residues and charcoal particles EMA point analysis show that the organic matter constituents of heavy metal contaminated soils are highly enriched with heavy metals. The maximal trace element accumulation were for Cu up to 13,000 mg/kg, for Zn up to 48,000 mg/kg, for Cd up to 2,100 mg/kg and for Pb up to 193,000 mg/kg. The affinity for the accumulation of the different heavy metals in aggregations of humic substances can be described by the sequence Cu > Pb ? Cd > Zn ? Ni > Co. In very strongly acidified humic top soil horizons the Pb and Cd accumulation in the organic matter constituents is in competition with the accumulation in Fe and Mn oxides. The heavy metal contents (especially of Cu) of the organic matter are often correlated with the content of organically bound calcium. The EMA results also show that high heavy metal amounts occur in combination with Ca-accumulations in the epidermis and the outer bark parenchym of decayed roots. EMA point analysis of the interior of fungus sclerotias show that sclerotias can contain high amounts of heavy metals, in particular lead (up to 49,700 mg Pb/kg). From statistical results of EMA point analysis follows that lead and other heavy metals attached to humic substances are not only bound as metal organic complexes but also as organic metal phosphate complexes. Also charcoal particles of polluted soils contain high amounts of heay metals. The accumulation affinity is quite similar to that of humic substances.  相似文献   

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