Distribution of different fractions of cadmium,zinc, lead,and copper in unpolluted and polluted soils

McLaren and Crawford's method for fractionating soil Cu was modified, and used to fractionate soil Cd, Zn, Pb, and Cu in 38 soil samples from 11 soil profiles from industrially polluted and nearby unpolluted areas. Pollutant metals, especially Cd and Zn, were more soluble than the native soil metals. On average, approximately 45% of Cd was present in the CaCl₂ soluble (CA) fraction, whereas corresponding values for the other metals were below 10%. The percentages of each metal in the CA fraction followed the order Cd > Zn > Pb > Cu. The same order was observed for the acetic acid soluble (AAC) fraction. Approximately 30% of total Pb and Cu were present in the pyrophosphate soluble (PYR) fraction, and only 10% of total Cd and Zn. Approximately 20% of total Zn or Pb and 10% of Cd or Cu were present in the free oxide (OX) fraction. Only 20% of Cd and between 40–50% of the other 3 metals were present in the residual (RES) fraction. The results show that Cd is more labile than the other 3 metals.     

Chemical pools of cadmium, nickel and zinc in polluted soils and some preliminary indications of their availability to plants

This study was conducted to determine the chemical distribution and plant availability of Cd, Zn and Ni in eight metal-polluted soils in southern Ontario, Canada. There were altogether 30 different soil samples because two of the soils had received various sewage sludge treatments. The soils were sequentially extracted with 1 m ammonium acetate to remove soluble plus exchangeable metals, with 0.125 m Cu(II) acetate to remove complexed metals, and with 1 m HNO₃ to dissolve chemisorbed or occluded metals and precipitates such as oxides and carbonates. Expressed as a percentage of the metal so extracted, exchangeable Cd and Zn and Ni; complexed Cd and Zn>Ni and Ni>Zn>Cd in the acid-soluble pool. With a few exceptions (soils with high organic matter content or low pH) at least 50 per cent of the extracted metal was in the acid-soluble pool. The percentage of metal complexed was significantly correlated with organic matter content. The percentage of metal in the acid-soluble fraction was significantly correlated with soil pH. Preliminary findings based on the results with two soils suggested that for Cd and Zn plant availability was correlated with the concentrations of exchangeable, complexed or acid-soluble pools of Cd and Zn.     

Speciation of cadmium,copper, lead,and zinc in contaminated soils

Abstract

To investigate the activity of free cadmium (Cd²⁺), copper (Cu²⁺), lead (Pb²⁺), and zinc (Zn²⁺) ions and analyze their dependence on pH and other soil properties, ten contaminated soils were sampled and analyzed for total contents of Cd, Cu, Pb, and Zn (Cd_T, Cu_T, Pb_T, and Zn_T, respectively), 0.43 MHNO₃‐extractable Cd, Cu, Pb, and Zn (Cd_N, Cu_N, Pb_N, and Zn_N, respectively), pH, dissolved organic matter (DOC), cation exchange capacity (CEC), ammonium oxalate extractable aluminum (Al) and iron (Fe), and dissolved calcium [Ca²⁺]. The activity of free Pb²⁺, Cd²⁺, Cu²⁺, and Zn²⁺ ions in soil solutions was determined using Donnan equilibrium/graphite furnace atomic absorption (DE/GFAA). The solubility of Cd in soils varied from 0.16 to 0.94 μg L^‐1, Cu from 3.43 to 7.42 μg L^‐1, Pb from 1.23 to 5.8 μg L^‐1, and Zn from 24.5 to 34.3 μg L^‐. In saturation soil extracts, the activity of free Cd²⁺ ions constituted 42 to 82% of the dissolved fraction, for Cu²⁺the range was 0.1 to 7.8%, for Pb²⁺ 0.1 to 5.1% and for Zn²⁺2 to 72%. The principal species of Cd, Cu, Pb, and Zn in the soil solution is free metal ions and hydrolyzed ions. Soil pH displayed a pronounced effect on the activity of free Cd²⁺, Cu^2t, Pb²⁺, and Zn²⁺ ions.     

Leaching of zinc,lead and cadmium in columns of calcareous soils

Leaching of zinc, lead and cadmium was studied in columns packed with soil differing in pH, clay, organic matter and calcium carbonate contents. Distribution of 1 N HCI extractable heavy metals in different layers of the columns as a function of the amount of water leached was the criteria for measuring leachability of the three metals. Leachates contained only traces of the metals. Movement of surface applied metals could be observed only upto 30mm depth. Cadmium, which was observed to be the most mobile element, was leached to a depth of 30–40mm in a pH 7.5, light textured soil with 0.9 % calcium carbonate. Presence of superphosphate at the soil surface reduced the extent of leaching to an appreciable extent.     

接种微生物对土壤中Cd、Pb、Zn生物有效性的影响

针对提高植物修复土壤重金属污染的效果,以印度芥菜作为重金属富集植物,通过盆栽试验研究了巨大芽胞杆菌和胶质芽胞杆菌的混合微生物制剂(A处理)和黑曲霉发酵液(B处理)对植物修复Cd、Pb、Zn污染土壤的作用效果。结果表明:巨大芽胞杆菌和胶质芽胞杆菌的混合微生物制剂,不仅可以促进富集植物的生长,使其印度芥菜的生物量提高24.73%,并且可促进土壤Cd、Pb、Zn的活化,使土壤Cd、Pb、Zn有效态含量分别提高15.02%、7.65%和2.23%,增强富集植物对土壤的Cd、Pb、Zn富集吸收,使印度芥菜对土壤Cd、Pb、Zn的提取量分别提高52%、121%和23%,显著提高其植物修复效果。从对植物生理生化指标的影响来看,A处理对植株的伤害程度要低于B处理,它是一种有助于植物修复Cd、Pb、Zn污染土壤的微生物制剂,在植物修复领域有较高的利用价值。然而,黑曲霉混合发酵液不适于促进植物修复应用。     

Effect of pH,and phosphorus and organic matter contents on zinc availability and distribution in two Zimbabwean soils

Abstract

Laboratory studies to assess the effects of pH, and phosphorus (P) and organic matter contents on zinc (Zn) distribution in various soil fractions were conducted. Soils were incubated with different levels of lime, P fertilization, and two types of added organic materials. Phosphorus and pH were found to influence Zn distribution in the different soil fractions. Increase in pH and P decreased available and organic Zn and increased unavailable forms. Where fresh Zn was applied, a greater proportion of Zn was retained in the available and organically‐bound Zn forms. Application of maize stover and cow manure had a temporal effect of reducing available zinc in both the Chiota and Gwebi soils. The organic Zn and other unavailable forms of Zn increased showing that Zn was being immobilised. The immobilization was a relatively rapid process occurring in the first two weeks. The release of Zn which had been immobilised increased with time of incubation.     

Effect of excess lead,cadmium, copper,and zinc on water relations in sunflower

The effect of excess concentrations of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) on water relations in young sunflower (Helianthus annuus L.) plants was studied in water culture under greenhouse conditions. The accumulation of the heavy metals was more intensive in the root than in the shoot. The rates of heavy metal accumulation in root were arranged in the following decreasing order: Cu, Cd, Zn, and Pb. Their transport into the above‐ground parts followed the order: Zn, Cu, Pb, and Cd. Transpiration and relative water content were significantly decreased by excess concentrations of the heavy metals. The number of stomata per unit leaf area was increased while the size of the stomata was decreased. The concentration of free proline significantly increased in the leaves of intact plants as well as in leaf discs incubated in the presence of heavy metals. The concentration of soluble proteins decreased as well, particularly when plants were exposed to high concentrations of the heavy metals. It was concluded that excess concentrations of the heavy metals significantly affected plant water status, causing water deficit and subsequent changes in the plants. The most intensive effect on the plants was exerted by Cd, less intensive by Cu and Zn and the least intensive by Pb.     

Radio-labile cadmium and zinc in soils as affected by pH and source of contamination

The determination of radio‐labile metals in soil has gained renewed interest for predicting metal availability. There is little information on to what extent the fraction of labile metal is affected by the soil properties and the source of metal contamination. The radio‐labile content (E value) of Cd and Zn was measured in field‐collected soils with Cd and Zn originating from different sources. The E values were erratic and sometimes even exceeded total metal content when the concentration in the soil extract was less than 8 μg Zn l^?1 or less than 3 μg Cd l^?1. Addition of EDTA (0.1 mm ) to the radio‐labelled soil suspension resulted in larger concentrations of Cd and Zn in solution and smaller E values for these soils. The E values were, however, unaffected by the presence of EDTA (0.1 mm ) in soils with larger concentrations of Cd and Zn in solution. The %E values (E value relative to metal soluble in aqua regia) ranged from 9% to 92% (mean 61%) for Cd and from 3% to 72% (mean 33%) for Zn. No correlation between soil properties and %E was observed for Cd, and the %E of Zn was negatively correlated with soil pH (r = ?0.65). There was a strong negative correlation between pH and %E in soils enriched with metals in soluble form (e.g. metal salts, corrosion of galvanized structures). In soils where Cd or Zn were added in a less soluble form, no such correlation was found, and %E values were generally less than in soils spiked with metal salts, suggesting that the source of the contamination controls mainly the labile fractions of Cd and Zn.     

The solid solution equilibria of lead and cadmium in polluted soils

A method for the measurement of Pb and Cd in equilibrium soil solutions involving soil equilibration with a dilute Ca electrolyte, centrifugation and filtration to <0.2 μm was evaluated. The procedure was subsequently used for the analysis of 100 Pb- and 30 Cd-contaminated soils. Solutions were analysed for Pb- and Cd using graphite-furnace AAS and the concentrations of Pb²⁺ and Cd²⁺ were estimated using standard speciation calculations. The concentrations of Pb and Cd found in the soil solutions were in the range 3.5–3600 μg dmp ^?3 and 2.7–1278 μg dm ^?3 respectively; both ranges represented less than 0.1% of the total metal concentration in the soils. Depending on solution pH, Pb ⁺² accounted for between 42–78% of Pb in solution while about 65% of Cd in solution was present as Cd⁺². The concentrations of Pb²⁺ and Cd²⁺ in solution suggested that the soil solutions were undersaturated with respect to the solid phases PbC0₃ and CdC0₃ but supersaturated with respect to Pb₅(P0₄)₃Cl and, for some samples, Cd₃(P0₄)₂ respectively. However, for both metals, a good empirical relationship was obtained between the total metal concentration in soil (mol kg^?1), free metal concentration in solution (mol dm^?3) and solution pH. The relationships took the general form of a pH-dependent Freundlich adsorption equation: For both lead and cadmium relationships, the values ofn and K₁ were close to unity, so that the distribution coefficient could be estimated from pH and a single metal-dependent constant, K₂. The algorithms appeared to be valid over a metal concentration range of four logarithmic units and pH range of 3.5–7.5.     

Effect of zeolite application and soil pH on cadmium sorption in soils

Abstract

In this study the influence of zeolite application and soil liming on cadmium (Cd) sorption by soils in Greece was investigated. The zeolite was natural and consisted mainly of clinoptilolite. The soil samples were strongly acid surface horizons of an Alfisol limed from a pH of 4.0 to 8.5, and a neutral Bt horizon. The result showed that liming and zeolite application substantially increased sorption of Cd in the soils. Cadmium sorption was described adequately by the Freundlich equation whereas the Langmuir model failed to describe Cd sorption in the soils. The Freundlich constant K increased in value by zeolite application as well as by soil liming. A strong relationship was observed between this parameter and soil pH. A high percentage of cadmium sorbed was released in the desorption procedure. The amount of Cd released was reduced by zeolite application as well as by soil liming. It is concluded that zeolite application as well as soil liming increased Cd sorption by the soils.     

Relative toxicity of cadmium,lead, and zinc on barley

Abstract

The relative toxicity of cadmium (Cd), lead (Pb), and zinc (Zn) on the growth performance of barley (Hordeum vulgare L.) was measured. Lead and Zn resulted in an increase in dry matter production at the lower additions. All the Cd and the higher Pb and Zn additions resulted in significant decreases in growth over the controls, the roots showing a greater decrease in dry matter accumulation than did shoots. Roots accumulated higher amounts of Cd, Pb, and Zn in direct proportion to that soil‐applied. A significant inverse relationship between relative yield and tissue element concentration was observed. Toxicity occurred in the following order: Cd > Pb > Zn. Threshold concentration, critical tissue concentrations, and loading rates to produce a 10% yield reduction were also calculated. Our study indicates the possibility of estimating barley yield based on plant tissue Cd, Pb, and Zn concentrations.     

Fractional composition of nickel,copper, zinc,and lead compounds in soils polluted by oxides and soluble metal salts

The transformation of technogenic compounds of nickel, copper, zinc, and lead entering the soil as nitrates and oxides has been studied in a model experiment. It has been shown that the results of the determination of the fractional composition of the heavy metals strongly depend on the fractionating method used. The fractional composition of heavy metals that entered the soil as the readily soluble compounds mainly depends on the affinity of ions with the reaction centers of the soil components. When soils are polluted by such weakly soluble compounds of heavy metals as oxides, their transformation and, consequently, the fractional composition formed are determined, in the first place, by the solubility of these compounds and only afterwards by the interaction of the products of the dissolution with the soil. The transformation of the technogenictechnogenic zinc and lead oxides in the soils is more complete than that of copper and nickel oxides. This leads to a strong increase in the portion of the residual fraction of these elements under fractionating. The 1 N nitric acid almost does not extract copper and nickel oxides from the soil. This can be a reason for the erroneous estimation of the extent of soil pollution.     

Sorption of lead,copper, zinc,and cadmium by soils: effect of nitriloacetic acid on metal retention

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%.     

在法国前铅和锌冶炼厂附近的城市土壤重金属的污染、分离和利用

smelters in Northern France were studied by analysing the chemical forms of these metals and evaluating their phytoavailability. These metals were determined using flame or electrothermal absorption atomic spectrometry （FAAS or ETAAS）, depending on their concentration levels. After optimisation of the ETAAS method, characteristic mass of In in water and aqua regia were 9.9 and 18 pg, respectively, showing the high sensitivity of the analytical Soil contamination by metals from anthropogenic activities （e.g., mining and smelting） is a major concern for the environment and human health. Environmental availability of cadmium （Cd）, lead （Pb）, zinc （Zn）, copper （Cu）, and indium （In） in 27 urban soils located around two former Pb and Zn smelters in Northern France were studied by analysing the chemical forms of these metals and evaluating their phytoavailability. These metals were determined using flame or electrothermal absorption atomic spectrometry （FAAS or ETAAS）, depending on their concentration levels. After optimisation of the ETAAS method, characteristic mass of In in water and aqua regia were 9.9 and 18 pg, respectively, showing the high sensitivity of the analytical procedure. Metal partitioning was conducted using a four-step sequential extraction procedure. The results showed that Cd and Zn were mainly in the acid-extractable and reducible forms in the urban soils studied. In contrast, Pb and In were largely in the reducible fraction. However, in some samples, the amount of In extracted in the residual or exchangeable fraction was higher than that in the reducible fraction. Copper was mainly found in the reducible and residual fractions. A pot experiment was conducted in a glasshouse with seven soils （six contaminated and one uncontaminated） and two plant species, ryegrass and lettuce. The results showed transfer of metals from the contaminated soils to the shoots of ryegrass and the edible part of lettuce. The metal bioconcentration factor was in the order of Cd Cu > In > Zn Pb for lettuce leaves, whereas for ryegrass shoots, three orders were found, Cd > Zn > Cu In > Pb, Cd ≥ In > Zn > Cu Pb, and Zn > Cd > Cu > In > Pb, depending on the physico-chemical properties of the soils, such as pH, cation exchange capacity, carbonates, and organic matter. It was established that the metal toxicity was related to the contamination levels and the physico-chemical properties, including pH, organic matter, and in a lesser extent, Ca, Mg, and phosphorus contents, of the soils. However, it was shown that lettuce could grow on soils having high Cd and CaCO₃ contents. Cadmium was one of the most available metals while Pb was always the least available in the soils studied.     

Plant availability of lead,cadmium, and boron in amended coal ash

Reclamation and revegetation of coal combustion products (ash) are often complicated by high concentrations of metals. The effects of manure and soil additions on the extractability and plant availability of Pb, Cd, and B were examined in ash reclamation plots located in eastern Kansas. Concentrations extracted from the ash by ammonium bicarbonate DTPA were strongly affected by ash type and amendment, but were unaffected by crops. Plant uptake was affected by ash type and plant species and, to a smaller extent, by amendment. Extractable and plant concentrations were very high in some of the material, which was consistent with observed toxicity symptoms. Plant concentrations showed strong, positive correlations with extractable for Cd and B (r values 0.7 to 0.9), but plant Pb was negatively correlated with extractable concentrations (r = –0.66). Correlations were similar for plant uptake vs extractable for Cd and Pb but were much poorer for B.     

硫酸盐对锌和镉在可变电荷土壤上吸附的影响

SO4^2- and Zn^2 or Cd^2 were added to three variable charge soils in different sequences.In one sequence sulfate was added first ,and in the other,Zn^2 or Cd^2 first.The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added,with the effect more remarkable whn the soil reacted with the sulfate prior to the metal.the shift in pH50 for both Zn and Cd adsorption was aslo comparatively larger in the first sequence of reactions .It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd,and the formaiton of the ternary surface complex-S-SO4-M might also play a role in the effect.     

Total content and extractable fraction of cadmium,cobalt, copper,nickel, lead,and zinc in calcareous orchard soils

Abstract

The levels and availability of six heavy metals cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in calcareous orchard soils were measured in an investigation of a method for the determination of total content and extractable fraction of these metals by atomic absorption spectrometry. The digestion step was performed comparatively using two different types of heating. Cadmium, Cu, Ni, Pb, and Zn were determined by flame atomic absorption spectrometry (F‐AAS) and Cd was determined by electrothermal or graphite furnace atomic absorption spectrometry (GF‐AAS) using the method of standard addition. The detection limits, precision values, and accuracy (recovery assays) show the reliability of the method. The conditions for the determination of the extractable fraction of the metals were also optimized. Extraction time for Cd and Zn was studied, and the application of two hours of shaking was selected. The tested method was applied to real samples corresponding to highly calcareous orchard soils characteristic of the Mediterranean area. Only Zn, Cu and Pb showed high levels in their extractable forms, whereas Cd and Co had highest levels in their total contents. An important bio‐availability was observed in all the studied metals, but mainly for Cd and Pb.     

Nitrogen fixation by white clover (Trifolium repens) in grasslands on soils contaminated with cadmium, lead and zinc

The nitrogenase activity (potential nitrogen fixation) of a mixed white clover-grass sward growing on a range of soils containing up to 216 μg g^?1 Cd, 30 000μg g^?1 Pb and 20 000 μg g^?1 Zn was determined using the acetylene-reduction assay. The plants were incubated in situ using an intact soil-core technique. Little change in the rate of C₂H₂ reduction was observed during the daylight hours although a marked seasonal fluctuation was found, the maximum activity during the spring and declining to 20% of this by the autumn. Some reductions of nodule and plant size, and in nitrogenase activity, was observed in the most heavily contaminated sites. These effects were small; the plants and nodules otherwise appeared healthy. The potential for nitrogen fixation was equally high in all the sites at up to 80 g N ha^?1 h^?1 in the spring.     

Mobility of heavy metals in polluted soils near zinc smelters

The distribution and the availability of Cd, Zn, Cu, and Pb along the entire profile of two highly polluted soils located near Zn smelters have been related to the chemical and mineralogical composition of the soil. Lead and Cu deposits always remain in the surface layers and their availability measured by neutral ammonium acetate extraction was very weak. The behavior of Cd and Zn appears different in sandy acidic podzolic soils and in neutral loamy soils. These metals are associated with the organic matter migration in podzolic soils, while they remain in the upper layers in loamy soils provided that the pH is higher than 6. When the pH drops below 6, the mobility of Cd increases while that of Zn increases only below pH 5. The availability of heavy metals is lower in neutral loamy soils than in sandy acidic soils due to precipitation of carbonates and phosphates. With increasing depth, Cd and Zn are more available if the soil is acid; but, if the soil is neutral and loamy the availability is kept low by adsorption on clays and free oxides. The results of the complex trace metals interactions with the soil components show a higher accumulation capacity for loamy soils than for sandy soils notwithstanding the fact that their CEC is similar.     

施用污泥后石灰性土壤中铜、锌、镉的植物有效性

The toxicity of trace elements (TEs), such as copper (Cu), zinc (Zn), and cadmium (Cd), often restrict land application of sewage sludge (SS) and there was little information about soil-plant transfer of TEs in SS from field experiments in China. In this study pot and field experiments were carried out for 2 years to investigate the phytoavailability of TEs in calcareous soils amended with SS. The results of the pot experiment showed that the phytoavailability of Zn and Cu in the SS was equal to 53.4%-80.9% and 54.8%-91.1% of corresponding water-soluble metal salts, respectively. The results from the field experiment showed that the contents of total Zn, Cu, and Cd in the soils increased linearly with SS application rates. With increasing SS application rates, the contents of Zn and Cu in the wheat grains initially increased and then reached a plateau, while there was no significant change of Cd content in the maize grains. The bioconcentration factors of the metals in the grains of wheat and maize were found to be in the order of Zn > Cu > Cd, but for the straw the order was Cd > Cu > Zn. It was also found that wheat grains could accumulate more metals compared with maize grains. The results will be helpful in developing the critical loads of sewage sludge applied to calcareous soils.