Mobility and distribution of cadmium, nickel and zinc in contaminated soil profiles from Bangladesh

We investigated the mobility and distribution of cadmium (Cd), nickel (Ni) and zinc (Zn) in four contaminated soil profiles from Bangladesh. The sources of contamination of these profiles were tannery wastes, city sewage and the wastes of pharmaceutical and paper mill factories at different locations in Bangladesh. The samples were collected from the A-, B- and C-horizons of each profile: two sub-samples from the A-horizon at depths of 0–5 cm (A1) and >5 cm (A2), and one sample each from the B- and C-horizons. Soil samples were analysed for total metal content by dissolution in aqua regia followed by sequential extraction of the fractions based on their varying solubility. There were six operationally defined groups of extraction sequences: water soluble (F1), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6). The total concentration of Cd, Ni and Zn in the A-horizon (0–5 cm) ranged from 0.10 to 0.62, from 31 to 54 and from 85 to 838 mg kg⁻¹, respectively. In the B- and C-horizons, the concentrations of these metals decreased many fold, particularly in the city sewage profile where the decrease for Cd and Zn was approximately fourfold. The distribution of metals among the chemical fractions depended on their total concentrations. In the A1-horizon, Cd had the highest mobility factor [MF = (F1+F2+F3)/(F1+F2+F3+F4+F5+F6) × 100] at 41–43% and Ni had the lowest at 3–13%, while Zn, showed intermediate values at 8–25%. The MF decreased with depth in all soil profiles. Among the fractions, the residual fraction contained the lowest levels of Cd but the highest levels of Ni and Zn. This state affected their relative mobility and distribution in soil profiles. Of the soil profiles, the mobility of all metals was higher in the city sewage soil than in any of the other three soils investigated, suggesting that the former may create a health risk by contaminating agricultural products and ground water as it also contained higher amounts of Cd and Zn.     

Metal availability in contaminated soils: II. Uptake of Cd, Ni and Zn in rice plants grown under flooded culture with organic matter addition

Higher accumulation of toxic heavy metals in rice grown in contaminated soils may lead to health disorder in humans in tropical countries as rice is a staple diet. A pot experiment was conducted in a growth chamber to investigate the effect of flooding and non-flooding conditions in three soils added with4% organic matter on the concentration and uptake of Cd, Ni and Zn by rice plants (Oryza sativa L.). In flooding condition, the level of standing water was at a height of 2.5 ± 0.5 cm above the soil surface and in non-flooded culture80 ± 5% of water holding capacity was maintained. Flooding condition significantly(p < 0.05) reduced the concentration and uptake of Cd, Ni and Zn in rice grown in all three soils. The overall reduction of metal concentration in shoot at vegetative stage, and straw and polished rice at maturity, under flooding conditions was 84, 89, and 79% for Cd; 21,63and 65% for Ni; and 52, 78 and 16% for Zn, respectively. Organic matter addition significantly reduced the Ni concentration in plant parts but no such reduction was seen for Cd and Zn. Accumulation index of Cd and Zn was 82and 55% higher than that of Ni in the plant and the index of all three metals was higher in the tannery soil than the other two soils. Polished rice contained significantly lower amounts of Cd, Ni and Zn than shoot and straw. Cadmium and Ni uptake in polished rice was > 20% of the total uptake and thus it may be a concern for human health. This revised version was published online in August 2006 with corrections to the Cover Date.     

Zinc equilibria in submerged sodic soils as influenced by application of amendments

In a pot culture experiment, the effect of gypsum (50% of soil requirement), pyrites (equivalent to gypsum), farmyard manure (0.5 g per 100g soil) and Zn (10mg Zn kg^–1 soil) on Zn equilibria in Ghabdan and Langrian series of sodic soils was studied. The equilibrium soil solutions collected anaerobically after 1, 14, 28, 42, 56, 70 and 84 days of submergence were analysed for pH, EC, HCO₃ and Zn. Submergence markedly decreased soil solution pH and Zn up to 14 days and thereafter, the former slightly increased and the latter continued to decrease. Addition of amendments decreased soil solution pH in the order gypsum, pyrites and farmyard manure (FYM) and increased Zn concentration in the order FYM, gypsum and pyrites. The values of Zn potential (pZn + 2pOH) were within the range of pKsp for Zn(OH)₂-Zn²⁺ (aq) from 16 to 84 days of submergence in Ghabdan soil and from 9 to 42 days of submergence in Langrian soil, where later it shifted to ZnCO₃-Zn²⁺ (aq) system. Addition of FYM, pyrites and gypsum shortened the period of predominant existence of Zn(OH)₂-Zn²⁺ (aq) system to 40, 30 and 12 days in Ghabdan soil and 30, 20 and 6 days in Langrian soil respectively. After these periods the system was saturated with respect to ZnCO₃-Zn²⁺ (aq) except gypsum treatment where Zn-soil (unknown solid phases) -Zn²⁺ (aq) system controlled the solubility of Zn after 38 and 28 days of submergence of Ghabdan and Langrian soil respectively.     

The effect of fertilizer additions on the solubility and plant-availability of Cd, Ni and Zn in soil

We conducted a pot experiment to investigate the effect of fertilizer additions on the solubility of Cd, Ni and Zn in soil solution and their uptake by plants. Radish (Raphanus sativus cv. Crystal Ball), oat (Avena sativa cv. Thule) and water spinach (Ipomoea aquatica cv. Kangkon) were grown in a naturally metal-rich soil. From day 7 after planting, fertilizers were added daily to each pot. Additions of fertilizer nutrients affected the pH of soil and soil solution, soluble and tissue concentrations of Ca, Mg, K, Cd, Ni and Zn differently in three plant species. The trend of soil and solution pH was in the order: water spinach < radish < oats, that resulted highest soluble and plant tissue concentrations of Cd and Zn in the water spinach followed by radish and then oats. However, Ni concentration in the soil solution increased in all pots and was not affected by pH changes. Soil solution pH increased by more than 1unit in the pots with radish and oats, indicating that mechanisms other than acidification, such as ion exchange and root exudation, may be responsible for the increased heavy metal uptake in these two plant species. Paired t-test showed significantly higher uptake of Cd and Zn in the radish plants resulting in lower concentrations of these elements in the solution. The contribution of mass flow to the supply of major cations and heavy metals varied among elements and plant species. Cadmium, Zn and K were taken up rapidly by all plant species in response to the amount supplied by mass flow. In contrast, the supply of Ni was in excess of its uptake by radish and water spinach. The uptake of all elements was positively correlated (p<0.0001) with mass flow and the transpiration rate in individual plant species. The study suggests that fertilizer cations increased the uptake of metals by improving growth conditions, but the magnitude of increase depended on plant species. This revised version was published online in November 2006 with corrections to the Cover Date.     

Précipitations sélectives des métaux solubilisés biologiquement de boues aérobies d'épuration

The selective and successive precipitation resulting from the biological solubilization (Thiobacillus ferrooxidans) of sewage sludge metals was studied. At the same time, theoretical diagrams representing the solubility of hydroxides and metal carbonates (Ca, Mg, Fe, Al, Cu, Zn, Ni, Cd, Mn) and their complexes are compared to the experimental values. The pH was progressively increased by means of Ca(OH)₂- The iron hydroxide precipitate, which was the least contaminated, was obtained at pH of 3.5. The theoretical pH's for acceptable metal precipitation were identified as: Fe⁺³ at pH 3.2, Al⁺³ at pH 4.7, Cu⁺² at pH 6.9, Zn⁺² at pH 8.15, Ni⁺² at pH 8.4 and Mn⁺² at pH 9.1, and were closed to theoretical values. The hydroxide ion controls Ca, Mg and Cu solubilities. A precipitate with about 20% of Cu can be obtained at a pH of 7 after iron hydroxide was precipitated. Recovery of other metals than iron is thus possible.     

Binding of cadmium,copper, and zinc to humic substances originating from municipal solid waste compost

The application of municipal solid waste (MSW) compost increases both the trace metal loading and the organic matter in the soil. To characterize the quality and metal-binding capacity of the compost OM, we extracted humic acid (HA) and fulvic acid (FA) from mature MSW compost and analyzed them for elemental composition, acid-titratable functional groups, total metal content, and structural components (by ¹³C NMR). HA constituted 67% of all extracted humic substances and differed significantly from HAs of cultivated lands: The compost HA exhibited smaller molecular size, a higher N content, and lower aromaticity due to large amounts of saturated aliphatic components. Metal complexation studies of the extracted HA and FA were performed by equilibrium dialysis titration. The complexing capacity (CC) was highest for Cu: CC_HA = 3357 and CC_FA = 5221 μmol Cu g⁻¹ of dissolved organic carbon (DOC) at pH 5. Zn and Cd were bound (at pH 7) in smaller concentrations: CC_HA(Zn) = 2167, CC_FA(Zn) = 2809, CC_HA(Cd) = 2386, and CC_FA(Cd) = 2468 μmol metal g⁻¹ of DOC. Stability constants for binding on the strongest sites (pK_int) were determined as pK_intHA = 6.6 and pK_intFA = 7.3 for Cu at pH 5; and pK_intHA = 8.0 and pK_intFA = 6.4 for Cd at pH 7. Since these measured parameters fall within the ranges of values obtained for soil humic substances, we conclude that in soils with little organic matter, compost addition will significantly increase the amount of highly reactive organic complexing agents for trace metals in the soil.     

黑龙江省典型蔬菜大棚土壤重金属污染评价

为探索黑龙江省典型大棚土壤中重金属Cu、Zn、Cd的污染状况,采用单因子与限值比较、综合因子指数法和相关系数法对污染情况进行综合评价。结果表明:除肇东2a、肇东6a棚龄无污染外,其他大棚均有不同程度的污染;五常8a、肇东11a棚龄属轻度污染,其他棚龄均达中污染程度,而且五常大棚综合污染程度较肇东严重。Cu、Zn、Cd与棚龄之间的相关系数显示,各元素与棚龄之间存在着相关关系。五常大棚Cu、Zn、Cd与棚龄呈显著相关(P<0.05),相关程度Cu>Cd>Zn;肇东大棚Cu、Zn、Cd与棚龄之间达极显著相关(P<0.01)。     

Concentration of trace elements in arable soil after long-term application of organic and inorganic fertilizers

The Ruzyně Fertilizer Experiment (RFE, the Czech Republic) was established on a permanent arable field (illimerized Luvisol) in 1955. The effects of long-term application of several organic fertilizers (dung water, farmyard manure, poultry litter) and mineral N, P and K fertilizers on plant-available (extracted by CaCl₂), easily mobilizable (extracted by EDTA), potentially mobilizable (extracted by HNO₃) and total concentrations of trace elements were investigated in 2008. Concentrations of all analyzed trace elements in the applied fertilizers did not exceed the limits permitted by Czech national legislation. Concentrations of As, Cd and Cr were highest in single superphosphate, those of Cu, Mn and Ni were highest in poultry litter and those of Pb and Zn were highest in dung water. Poultry litter had the second highest concentration of As and Zn. Poultry litter supplied the soils with considerable amounts of Cu, Mn and Zn and increased their concentrations in the soil. There was also a significant increase in plant availability of Mn, Ni and Zn and a decrease in soil pH. Although all fertilizers were applied for five decades, total concentrations of As, Cr, Cu, Ni, Pb and Zn in soil remained far below Czech legislation limits. For Cu and Zn this was probably due to the relatively low mean annual application rates of poultry litter. Total Cd concentrations in soil exceeded the legislative limit even in the control (without any fertilizer inputs) and the effect of treatment was not significant. This indicates that fertilizers were not the main source of Cd in the experimental area. Therefore, common cropping practices do not induce soil contamination by trace elements even if they have been applied for more than 50 years.     

Effects and optimization of initial pH and sewage sludge compost content on leaching of lead and zinc in contaminated soil

We investigated the effects of initial pH (2≤pH₀≤6) and sewage sludge compost content (5≤[SSC]≤25 g/kg) on leaching characteristics of lead (Pb) and zinc (Zn) in contaminated field soil. pH₀ and [SSC] significantly affected the leaching of Pb and Zn in soils contaminated with them. The pH in the solution increased as reaction time and [SSC] increased. The leached amounts of Pb and Zn were highest at pH₀=2 and increased with reaction time. As [SSC] increased, the leached amount of Pb decreased (50.4 mg/kg at control condition ([SSC]=0 g/kg); 22.9 mg/kg at [SSC]=25 g/kg at pH₀=2) and the leached amount of Zn increased (20.1 mg/kg at [SSC]=0 g/kg; 31.7 mg/kg at [SSC]=25 g/kg at pH₀=2). The change increased as pH₀ decreased. Within the design boundaries, minimum leaching of Pb (14.7 mg/kg) occurred at pH₀=5.1 and [SSC]=25 g/kg, and minimum leaching of Zn (5.0 mg/kg) occurred at pH₀=5.1 and [SSC]=5 g/kg.     

The effect of soil pH and chemical form of nitrogen fertilizer on heavy-metal contents in ryegrass

Ryegrass was grown in pots containing metal-enriched soil which was adjusted to different pH levels with acid or lime, and supplied with either ammonium sulphate or calcium nitrate as the N fertilizer.Concentrations of heavy metals in the grass tops increased with decreasing soil pH to an extent diminishing in the order: Mn, Ni, Cd, Zn, Pb, Cu, Cr.Nitrate application was the more appropriate treatment for the production of lower concentrations of heavy metals in the grass because its use by the grass increased the pH of the soil, whereas added ammonium sulphate released acid to the soil during nitrification and plant uptake of ammonium. After three successive cuttings and repeated dressings, soil pH (H₂O) was 3 units higher with nitrate than with ammonium, resulting in a marked reduction in the uptake of the more pH-sensitive metals in soils where nitrate was applied     

Heavy metal pollution in the territory of Chelyabinsk upon coal combustion

The pollution of the territory of Chelyabinsk by heavy metals (Cu, Co, Ni, Zn, Pb, Cd, Cr, Mo, and Hg) upon coal combustion is evaluated. The concentrations of Zn, Pb, Cd, and Hg in the soils of this territory and the concentrations of Cd and Hg in water were found higher than health standard values (approximate permissible concentrations and maximum permissible concentrations) by factors of 1.5–20, 6, and 2, respectively.     

Effect of different treatments on electrokinetic remediation of Zn,Pb and Cd from a contaminated calcareous soil

Electrokinetic remediation is a promising method to decontamination of the heavy metals from soils.In this paper,the remediation of a contaminated calcareous soil with Zn,Cd and Pb sampled from around Zanjan province of Iran,was investigated using electrokinetic method.In this paper,the soil contain a high concentration of Zn (1400 mg·kg-1),Cd (15 mg·kg-1) and Pb (250 mg·kg-1).Electrokinetic decon-tamination consists of two series of experiments as follows:(1) the effect of five treatments including the use of distilled water,acetic acid and EDTA electrolyte solutions,and approaching anodes systems,and the circulation flow of electrolyte at two different voltage gradient (i.e.1.33 and 2.66 V·cm-1),and(2) the effect of moisture content (saturated,FC and 0.7FC,FC indicated soil moisture at "Field Capacity") with a voltage gradient of 1.33 V·cm-1.After applying electric current for 5 days,the results of experiments indicated that the removal efficiency of heavy metals can be increased by raising the volt-age gradient.In this matter,the highest remediation can be observed among different treatments in EDTA(Ethylene diamine tetra acetic acid) treatment (40.11％,43.10％ and 24.7％ for Zn,Cd and Pb,respectively).Moreover,the heavy metals removal at the saturated moisture was at the highest level so that 32.62％cadmium,31.33％ zinc and 18.82％ lead being removed after 120 h of electric current application.By decreasing moisture to 0.7FC,the removal percentage for the three heavy metals obtained 20.97％,18.44％ and 12.25％,respectively.Furthermore,Cd had the highest removal,and Zn and Pb were next among the three heavy metals in question.     

Relationship between soil physical and chemical characteristics and ear-leaf concentration of P,K, Mg,Zn, Fe,Cu, Mn and relative yield of maize in soils derived from sedimentary rocks of South-Western Nigeria

In a four-season field experiment conducted in 18 locations covering two different ecological zones of the sedimentary forest soils of South-Western Nigeria, relationships were established by simple correlation between the ear-leaf content of P, K, Mg, Zn, Fe, Cu, Mn, relative yield of maize (RY), soil physical characteristics and soil nutrient status. Soil pH was strongly related to the relative yield, soil clay, available P, exchangeable Ca, K, Zn, and Mn in soils, P and Cu concentration in the ear-leaf.Organic matter did not appear to play a very significant role in nutrient supply or relate to nutrient element concentration in the ear-leaf and relative yield in soils that are relatively low in soil organic matter.Nitrogen was not determined. Phosphorus among all the elements determined seemed to have a high significant effect on Ca, K, Zn, Mn and RY. However, the effect on RY was negative. Manganese in both soil and ear-leaf had the highest negative significant relationship with yield in the zone.The multiple regression analysis indicated a relationship meaning that the soil physical and chemical properties and ear-leaf content of the elements P, K, Mg, Zn, Fe, Cu, Mn are important to maize cultivation in this zone. Hence consideration of a combination of soils and plant factors are essential before meaningful fertilizer recommendation can be made for maize in the zone under study.     

温岭农业土壤中重金属的分布、来源及生态风险评价

采用电感耦合等离子体发射光谱法(ICP-AES)定量分析了温岭37个土壤样品中的Cu、Pb、Ni、Ag、As、Cd、Zn、Sn、Sb和Hg,并对其分布、来源及生态风险进行了评价。土壤中10种重金属的浓度范围在193.1～603.4 mg/kg之间,平均值为265.2 mg/kg。通过对照荷兰土壤标准限值和国家土壤质量二级标准,表明温岭地区土壤已经受到重金属的普遍污染。来源分析表明,温岭土壤中金属主要来源于工业活动、污水灌溉和农药施用等人类活动。对金属的生态风险评价表明,温岭为中等生态危害,对单个污染物的生态风险评价表明,Hg和Cd是主要的生态危害因子,应该受到重视。     

Zinc diffusion and extractability as affected by zinc carrier and soil chemical properties

This work was carried out to evaluate the effect of soil chemical properties, Zn carrier and time elapsed after fertilizer application on the diffusion and extractability of Zn. A soil block technique was used to study zinc diffusion and DTPA extractability from ZnEDTA and ZnSO₄ fertilizers in three soils that varied in texture, CaCO₃ content, organic matter content, and pH using Zn⁶⁵ tracer. ZnEDTA diffused readily in all soils, moving 20–25 mm from the fertilizer layer after three days. The rate of Zn diffusion and the extractability of Zn, however, varied among the soils and were lowest in Baha soil with the highest clay content, organic matter, and CEC despite its lower pH. The high pH and CaCO₃ content in Dirab soil did not restrict the diffusion or reduce the extractability of ZnEDTA in this soil. On the other hand, the diffusion of Zn from ZnSO₄ fertilizer was largely restricted in all soils and was confined to 5 mm from the fertilizer layer after 13 d. The extractability of ZnSO₄ fertilizer was largely affected by soil pH and CaCO₃ content and was lowest in Dirab calcareous soil. Organic matter amendment at 5% (as alfalfa) considerably reduced the diffusion and the extractability of ZnSO₄ in both Dirab calcareous and Bakyria noncalcareous soils. The application of 1% (w/w) elemental S reduced soil pH and increased Zn diffusion from ZnSO₄ fertilizer in Bakyria soil but had slight effect on Dirab calcareous soil.     

Assessing long-term changes in cadmium availability from Cd-enriched fertilizers at different pH by isotopic dilution

The application of commercial phosphate fertilizers containing Cd as an impurity is an important source of Cd to agricultural soils. The changes in the Cd status and its bioavailability in soils taken from a field trial were investigated after several years of application of fertilizers with a range of Cd contamination levels to soils. Various soil pH regimes were achieved by liming. The isotopic dilution technique was used to determine both the plant available (L-value) and isotopically exchangeable (E-value) Cd pools in soils. Firstly, we found that the L-values after 10 year of application were significantly higher at pH 5.0 than at pH 6.0, and this was reflected in the increased Cd uptake by wheat at the lower pH. There was no significant effect of the rate of soil Cd application on the L-values. Although long-term use of Cd enriched P-fertilizers increased the total concentration of Cd in soil, the impact on wheat production was insignificant. Most cultivated soils in Norway are maintained at soil pH between 5.5 and 6.5 by frequent liming. That brings up the second interesting finding, the possible impurity of lime used in this experiment. The lime was not analysed, as it was unexpected that liming might raise the total content of soil Cd substantially. That seems, however, to have been the case for this experiment since we find increase of total Cd even in the low-Cd input blocks of the trial.     

Investigation of Heavy Metal Ion Adsorption Characteristics of Poly(N,N Dimethylamino Ethylmethacrylate) Hydrogels

Abstract

In this study, Poly(N,N dimethyl‐amino ethylmethacrylate) (Poly(DMAEMA)) hydrogels with varying compositions were prepared in the form of rods by irradiating ternary mixtures of N,N‐dimethylamino ethylmethacrylate/ethyleneglycoldimethacrylate/water with gamma rays at ambient temperature. Swelling studies of poly (DMAEMA) hydrogels were performed at different pH values and maximum swelling values reached at pH 2. The adsorption characteristics of Pb(II), Cd(II), Ni(II), Zn(II), Cu(II), and Co(II) ions to poly(N,N dimethylamino ethylmethacrylate) hydrogels were investigated by a batch process. The order of affinity based on amount of metal ion uptake was found as follows: Cu(II)>Zn(II)?Co(II)>Pb(II) >> Ni(II)>Cd(II). In the adsorption studies of Cu(II), Zn(II), Co(II), Pb(II), Ni(II), and Cd(II) ions the Langmuir type adsorption isotherms were observed for all gel systems.     

Soil effects due to sewage sludge application in agriculture

Field trials show that increased nutrients (mainly P) and heavy metals in soil due to agricultural use of sewage sludge have mainly to be expected when sludge is applied in too high amounts. The biological effects of heavy metals on plants are determined by their solubility which is increased by pH decrease and degradation of organic matter. Normally, it should be expected that the microbial activity in soil would increase with the application of organic matter in sewage sludge. But, also negative effects on the microflora by simultaneous enrichment of organic matter or inorganic and organic pollutants were found. The most important deleterious effects on soil microorganisms are the reduction in size of the total biomass, a reduced nitrogen fixing activity and changes in the composition of microbial populations of the soil. At what stage heavy metal toxicity to soil microorganisms or to microbial processes in soil is likely to become evident is unfortunately still uncertain. Again, the soluble fraction of heavy metals (also of organic pollutants) is a determing factor. To minimize the shown environmental risks an adequate sludge management is proposed.     

城市污泥中重金属稳定性的化学形态分析

以城市污水厂剩余污泥为研究对象,以连续提取法对其中8种主要重金属元素的化学存在形态进行了分析,结果表明:污泥中除Ni、Zn、Cd有超标和潜在的超标危险外,其它各金属的含量均低于国家标准的最高要求;污泥Ni、Cd具有相当的生物毒性,其余的元素生物有效部分较少,稳定性较好。总体来看城市污泥可通过降低超标重金属含量来实现农用的目的。     

Soil deterioration as influenced by land disposal of reject brine from Salbukh water desalination plant at Riyadh, Saudi Arabia

Impact of reject brine chemical composition on soils in Riyadh Saudi Arabia, was evaluated. Soil samples at three depths along transect on both sides of the pond were taken, in addition to, water samples from feed, product, reject and pond. Results showed that, the salinity of the brine reached up to, 5500 mg l^− 1. The concentrations of soluble ions were exceeding the allowable limits in most water samples. The ratio of major ions and concentration factor was higher. The concentrations of heavy metals were in the allowable limits for drinking water standards especially, in the feed, and product waters. Results pertaining soil properties indicated that the soil pH, EC_e values and, the concentrations of soluble ions were higher in soils closed to the pond. Also, the concentrations of heavy metals were negatively correlated with CaCO₃ content and soil pH (expect for Pb; Zn; Cd and Cr), while it was highly correlated with clay content of the soil. Generally, higher ESP and EC_e values in the studied soils can lead to lower permeability, poor aeration and consequently soil deterioration.