Distribution of Trace Elements in Soils from the Sudbury Smelting Area (Ontario,Canada)

The sequential extraction procedure proposed by the European Commission Measurement and Testing Programme, combined with Scanning Electron Microscopy and Energy Dispersive X-ray Analysis(SEM/EDS), was applied to identify and quantify the chemical andmineralogical forms of Cu, Ni, Fe, Mn, Zn, Pb, Cr and Cd presentin the topsoil from a mining and smelting area near Sudbury (Ontario, Canada). The possible mobility of the chemical forms was also assessed. The metal fractions: (1) soluble and exchangeable, (2) occluded in manganese oxides and in easily reducible iron oxides, (3) organically bound and in form of sulphides, (4) residual mainly present in the mineral lattice structures were separated. Cu and Ni were the major metallic contaminants, occurring in soils in broad ranges of concentrations: Cu 11–1890 and Ni 23–2150 mg kg^-1. Cu was uniformly distributed among allthe extracted fractions. Ni was found associated mainly withthe residual forms, accounting for 17–92%, with an averageof 64%, of the total Ni present in the soils. Fe, Mn, Zn,Pb, Cr and Cd, while occurring in most analysed samples innormal soil concentrations, were primarily held in theresidual mineral fraction (on average >50%). The solubleand exchangeable forms made a small contribution (≤8.1%)to the total content of metals extracted. At least 14% ofthe total Cd, Mn and Pb was mobilised from the reducibleforms. The oxidizable fraction assumed mean values higher than10% only for Pb and Zn. Statistical treatment of the experimental data showed significant correlations between totalmetal content of the soils, some soil properties such as pH value, clay and organic matter content, and metal concentrationsin the various fractions. SEM/EDS analysis showed Fe in form ofoxides and sulphides in soils and Cu, Ni, Mn, Zn and Cr in association with iron oxides. Numerous black carbonaceous particles and precipitates of aluminium fluoride salts, observedin the solid residue left after `total’ digestion, were found tocontain Fe, Ni and Cr.     

Fractionation and Distribution of Metals in Guadiamar River Sediments (SW Spain)

Traditionally, the Guadiamar River (Seville, Southwest Spain) has received pollution from two different sources, in its upper section, from a pyrite exploitation (Los Frailes mine) and, in its lower section, from untreated urban and industrial wastes and from intensive agricultural activities. In 1998, the accidental spillage of about 6 million m³ of acid water and sludge from mine tailings to Guadiamar River worsened the pollution of an already contaminated area. The main polluting agents of the spillage were heavy metals. The total concentration of a metal provides scarce information about the effects on environmental processes or about the toxicity of the sediment samples. A more sophisticated fractionation of the sediment samples based on a species distribution can help to understand the behaviour and fate of the metals. This article describes a distribution study of the metals Al, Cd, Cu, Fe, Mn, Pb and Zn by fractionation analysis of sediments from eleven sample sites alongside the Guadiamar Riverbed. The samples were collected in summer 2002, four years after the spillage and after the area had been cleaned. Sequential extraction analysis resulted in the definition of four fraction categories: exchangeable metal (the most available fraction), reducible metal (bound to hydrous oxides of Fe and Mn), oxidizable metal (bound to organic matter and sulphides) and a residual fraction (bound to minerals). Significant increases in the available fraction of several potentially toxic metal ions like Cd, Mn and Zn were found. The distribution pattern was variable along the River. At the site closest to the mineworks, the soluble forms of Cd, Mn and Zn were significantly more abundant that those downstream. Cu and Pb were present in the reducible fraction while Fe was present associated in the residual fraction.     

Trace metal composition and speciation in street sediment: Sault Ste. Marie,Canada

Street sediment collected in Sault Ste. Marie, Ontario was examined for trace element composition (As, Cd, Cr, Cu, Fe, Pb, Hg, Ni and Zn) and the metal partitioning to various sediment properties was determined by sequential extraction. Total Ni, Cu, Zn and Pb concentrations exceeded the lowest effect levels specified in the Ontario Provincial Sediment Quality Guidelines for Metals (Environment Ontario, 1992) and derived from bioassay studies. According to these Guidelines, the disposal of such sediment has to be guided by environmental considerations. A significant fraction of these metals was extractable in 0.5 N HCl over a 12-hour period and considered as potentially bioavailable. The major accumulative phases of toxic metals in this sediment are exchangeable, carbonate, Fe/Mn oxides and organic matter but the relative importance of each phase varied for individual metals. Approximately 20% of the total extractable Cd is found in each of these four fractions. Pb, Zn and Mn are predominantly bound to carbonates, Fe/Mn oxides and organic matter. Cu shows a high affinity for organic matter and to a lesser extent for carbonates. Elevated levels of Cd, Pb, Cu, Zn, Mn and Cr in the exchangeable and/or soluble phase suggest that sediment associated metals, mobilised from streets in Sault Ste. Marie during runoff and snowmelt, would adversely impact water quality in the receiving waters. However, large fractions of the total metal load are associated with coarser particles which are unlikely to be transported through the drainage system into receiving waters.     

受土壤类型和金属负荷量影响的重金属形态分布

Two series of soil subsamples, by spiking copper(Cu),lead(Pb),zinc(Zn)and cadmium(Cd)in an orthogonal design,were prepared using red soil and brown soil,respectively.The results indicated that heavy metal fractions in these soil subsamples depended not only on soil types,but also on metal loading quantity as well as on interactions among metals in soil.Lead and Cu in red soil appeared mostly in weakly specifically adsorbed(WSA),Fe and Mn oxides bound(OX),and residual(RES)fractions.Zine cxisted in all fractions except organic bound one,and Cd was major in water soluble plus exchangeable(SE)one.Different from the results of red soil,Pb and Cu was present in brown soil in all fractions except organic one,but over 75% of Zn and 90% of Cd existed only in SE fraction.Meanwhile,SE fraction for any metal in red soil was lower than that in brown soil and WSA and OX fractions were higher.It is in agreernent with low cation exchange capacity and large amounts of metal oxides included in red soil.Metal fractions in soil,especially for water soluble plus exchangeable one ,were obviously influenced by other coexisting metals.The SE fraction of heavy metals increased with increasing loading amounts of metals in red soil but not obviously in brown soil,which suggest that metal availability be easily affected by their total amounts spiked in red soil.In addition,more metals in red soil were extracted with 0.20 mol L^-1 NH4Cl（pH5.40）than that with 1.0 mol L^-1 Mg(NO3)2(pH7.0),but the reverse happened in brown soil,implicating significantly different mechanisms of metal desorption from red soil and brown soil.     

Relationships of Heavy Metals in Natural Lake Waters with Physico-chemical Characteristics of Waters and Different Chemical Fractions of Metals in Sediments

The relationships between heavy metal concentrations and physico-chemical properties of natural lake waters and also with chemical fractions of these metals in lake sediments were investigated in seven natural lakes of Kumaun region of Uttarakhand Province of India during 2003–2004 and 2004–2005. The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l^?1 and in sediments 14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9, 13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g^?1, respectively. The concentrations of all metals except Fe in waters were found well below the notified toxic limits. The concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were positively correlated with pH, electrical conductivity, biological oxygen demand, chemical oxygen demand and alkalinity of waters, but negatively correlated with dissolved oxygen. The concentrations of Cr, Ni, Zn, Cd and Pb in waters were positively correlated with water soluble + exchangeable fraction of these metals in lake sediments. The concentrations of Zn, Cd and Pb in waters were positively correlated with carbonate bound fraction of these metals in lake sediments. Except for Ni, Zn and Cd, the concentrations of rest of the heavy metals in waters were positively correlated with organically bound fraction of these metals in lake sediments. The concentrations of Cr, Mn, Ni, Cu and Zn in waters were positively correlated with reducible fraction of these metals in lake sediments. Except for Cd, the concentrations of rest of the metals in waters were positively correlated with residual fraction and total content of these heavy metals in lake sediments.     

Assessment of Fe,Zn, Cd,Hg, and Pb in the Jordan and Yarmouk River Sediments in Relation to Their Physicochemical Properties and Sequential Extraction Characterization

Forty-six surface sediment samples taken along the beds of boththe Jordan and Yarmouk Rivers were analysed for Pb, Cd, Zn, Fe andHg by atomic absorption spectrophotometer. Extraction techniqueswere used to establish the association of the total concentrations of Pb, Cd, Zn and Fe in the sediment samples withtheir contents in the exchangeable, carbonate, Fe/Mn oxides, organic and residual fractions.In the sediments of the Jordan River the recorded heavy metalsconcentrations were as follow: 8.1 ppm for Pb, 0.63 ppm for Cd, 20.3 ppm for Zn, 6 ppm for Hg and 1265.6 ppm for Fe; whereas in the sediment of Yarmouk River were 8.4 ppm for Pb, 0.67 ppm for Cd, 26.4 ppm for Zn, 6.2 ppm for Hg and 1370 ppmfor Fe. Pb, Cd, Zn, and Fe concentrations in the sediments ofboth rivers reflect the natural background value in shale, whereas Hg is moderately enriched. I-geo (geo-accumulation index) of metals in the sediments under study indicates thatthey are uncontaminated with Pb, Zn and Fe; contaminated tomoderately contaminated with Cd; and strongly contaminated with Hg. Heavy metal content in the sediments were found to be significantly influenced by different physico-chemical parameters. The effect of these physico-chemical parameters canbe arranged in the following order: clay fraction > organicmatter fractions > carbonate fraction > silt fraction. As sequential extraction procedure shows that the total concentration of the heavy metals are largely bound to the residual phase (retained 79.5% of Pb, 38% of Cd, 54.4% of Zn and 51.6% of Fe in Jordan River Sediments; and 88.6% of Pb, 48.2% of Cd, 37.6% of Zn and 59.5% of Fe in the YarmoukRiver sediments). The following sequence of mobility are suggested: Fe > Cd > Zn > Pb in Jordan River sediments, and Fe > Zn > Cd > Pb. in Yarmouk River sediments.     

Heavy metal characterization of river sediment in Hanoi,Vietnam

Abstract

Industrial and municipal waste water is directly discharged to rivers in Hanoi, Vietnam. Sediments were collected from different sites of three rivers in the industrialized and densely‐populated area of Hanoi City and examined for total heavy metals and metal fractions using sequential extraction. Concentration of the total heavy metals ranged from the background levels to over the maximum permissible levels to crop growth. Concentrations of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) ranged from 0.27 to 4.50,78 to 517, 37 to 309, 37 to 174, 43 to 361, and 93 to 4,950 mg kg^‐1, respectively. Total concentration of heavy metals varied from site to site and tended to be higher in the site where manufacturing companies are located. Heavy metals were accumulated in the site and were not moved away to be redistributed in the whole area. Distribution of heavy metals in different chemical forms in the air‐dry state depended on their total concentration. In the low concentration range, Cr, Cu, Ni, and Zn were for the most part concentrated in the residual fraction. When concentration is equal to or above the maximum permissible level to crop growth, Cr, Ni, and Zn were mostly concentrated in the iron‐manganese (Fe‐Mn) oxides fraction and Cu was in the organic fraction. Irrespective of the total concentration, Cd was highly associated with the exchangeable and carbonate fractions, while the sum of the Fe‐Mn oxides and residual fractions accounted for 80 to 96% of total Pb.     

Trace metals in Valencia lake (Venezuela) sediments

An exploratory study of the trace metals Cd, Cu, Mn, Ni, Pb, and Zn in sediments of lake Valencia (Venezuela), South America, 10° 10′N, 68°68′W, gave the following results: (A) Total amounts of Cu, Ni, Pb, and Zn were within the normal range reported by the literature. (B) No consistent pattern of variation with depth was found. A and B could be taken as lack of evidence for contamination by Cu, Ni, Pb, and Zn of the studied sediments. Absence of Cu, Ni, Pb, and Zn pollution after more than 40 yr of anthropogenic discharges on this lake, was attributed mainly to the exploratory nature (limited sampling) of this work, together with some possible dilution effects due to the high CaCO₃ content of these lake sediments. (C) Manganese was above normal values in most samples, but in absence of known anthropogenic sources of this metal, the results found could not be clearly ascribed to metal pollution. (D) Cadmium showed enrichment factors of 10 to 30 indicating pollution of the lake sediments by this metal (probably by urban effluents, runoff, and electroplating industries). (E) The proportion of exchangeable metals was nil in most cases. Exceptions (Ni and Mn) had very low exchangeable fractions (<1.22%). (F) The most abundant fraction (except for Mn) was the residual one (59.7–97.8% of total metal). Other fractions (carbonates, oxides, and organic) showed intermediate values. The general pattern was that the bulk of trace metals studied were present in non-mobile, slightly or non-reactive, poorly or non-available forms.     

Chemical Speciation of Heavy Metals in the Fractionated Rhizosphere Soils of Sunflower Cultivated in a Humic Andosol

Chemical speciation and bioaccumulation factor of iron (Fe), manganese (Mn), and zinc (Zn) were investigated in the fractionated rhizosphere soils and tissues of sunflower plants grown in a humic Andosol. The experiment was conducted for a period of 35 days in the greenhouse, and at harvest the soil system was differentiated into bulk, rhizosphere, and rhizoplane soils based on the collection of root-attaching soil aggregates. The chemical speciations of heavy metals in the soil samples were determined after extraction sequentially into fractions classified as exchangeable, carbonate bound, metal–organic complex bound, easily reducible metal oxide bound, hydrogen peroxide (H₂O₂)–extractable organically bound, amorphous mineral colloid bound, and crystalline Fe oxide bound. Iron and Zn were predominantly crystalline Fe oxide bound in the initial bulk soils whereas Mn was mainly organically bound. Heavy metals in the exchangeable form accumulated in the rhizosphere and rhizoplane soils, comprising <4% of the total content, suggesting their relatively low availability in humic Andosol. Concentrations of organically bound Fe and Mn in soils decreased with the proximity to roots, suggesting that organic fraction is the main source for plant uptake. Concentrations of Mn and Zn in the metal–organic complex also decreased, indicating a greater ability of sunflower to access Mn from more soil pools. Sunflower showed bioaccumulation factors for Zn, Fe, and Mn as large as 0.39, 0.05, and 0.04 respectively, defining the plant as a metal excluder species. This result suggests that access to multiple metal pools in soil is not necessarily a major factor that governs metal accumulation in the plant.     

Laboratory Investigation of the Geochemical Behavior of Metals in Paddy Soils Contaminated with Mine Tailings

The geochemical behavior of metals, including Fe, Mn, Pb and Zn, in contaminated paddy soils was investigated during the cultivation of rice crops through laboratory microcosm experiments. From the two paddy fields contaminated by mine tailings, Siheung and Deokeum in Korea, paddy soils were collected and analyzed for their geochemical characteristics. The Siheung paddy soil showed higher levels of heavy metals, whereas the higher potential for the release of metals was anticipated due to the extremely acidic conditions at Deokeum. In microcosm experiments of flooded paddy soils over 18 weeks, Fe and Mn were released in subsurface pore waters by reductive dissolution, and Pb and Zn were dissolved in high amounts at the surface by oxidation of sulfides. Although amorphous Fe oxide-rich layers were formed at the surface of both paddy soils, the release of Pb and Zn were controlled at the surface by these layers only under slightly alkaline conditions at Siheung. Lead and Zn were associated with the reducible and carbonate fractions at the surface paddy soil of Siheung from the sequential extraction on core samples collected during the flooded period. In the acidic conditions at Deokeum, Pb and Zn were continuously released until the late stage of flooding. A great increase in the exchangeable fraction of metals was observed after the soils had drained. The bioavailability of metals for rice crops would be high under acidic conditions at Deokeum, despite the lower levels of heavy metal contamination.     

泉州走马埭典型土壤重金属的赋存形态分析

采用改进的Tessier连续萃取方法研究了泉州走马埭国家农田示范保护区典型土壤中重金属(Cr、Ni、Cu、Zn、Cd、Pb)的化学形态分布,通过土壤重金属的赋存形态分析比较了6种重金属的生物可利用性。研究结果表明,土壤中不同重金属元素化学形态分布具有不同的特点:Cr和Ni主要以残渣态存在,其余形态所占的比例很小;Cu以残渣态含量最高,碳酸盐结合态含量最低;Zn以残渣态为主,可交换态含量最低;Cd以可交换态和碳酸盐结合态为主,水溶态含量最低;Pb以残渣态和铁锰氧化物结合态为主,水溶态含量最低。土壤中除Cd外,Zn、Cu、Cr、Pb、Ni在正常自然条件下相对比较稳定。     

Copper,Zinc, and Lead Fractions in Soils Long-Term Irrigated with Municipal Wastewater

Long-term irrigation with municipal wastewater may lead, even in spite of intense farming, to an accumulation of organic matter, nutrient elements, and trace metals in soils. Excessive increases of heavy metals may pose a potential risk to the food chain and provoke restrictions for the further cultivation of sensitive crops. Copper (Cu), zinc (Zn), and lead (Pb) forms in soils under long-term irrigation (for 100–120 years) with treated wastewater of Wroclaw were investigated by using selective seven-step sequential extraction (procedure of Zeien-Bruemmer) for partitioning the metals into operationally defined fractions, likely to be released in solution under various environmental conditions. The largest fraction of Cu, Pb, and particularly Zn in nonirrigated (control) soils was strongly bound in a residual form, while the percentage of exchangeable and the most labile fractions were negligible. Total concentration of metals in irrigated soils was elevated, and significant redistribution of metals among phases was observed. Percentages of residual fraction of Cu and Pb were no more than 25% (Zn < 40%), while significantly increased contribution of fractions occluded on iron (Fe) oxides and organically bound Cu. Exchangeable and readily mobile forms of Zn are predominant zinc fractions in soils irrigated with wastewater.     

Small Scale Heterogeneity of Soil Chemical Properties. II. Fractions of Aluminum and Heavy Metals

Soil aggregates from nine horizons of five forest sites in Bavaria were mechanically separated into an aggregate surface fraction and an aggregate core fraction. Seven operationally defined fractions of AI, Cd, Cu, Cr, Ni, Pb, and Zn were determined by a sequential extraction procedure within both aggregate fractions. The CEC, C_org, and oxides of Mn and Fe also were measured. The differences in metal concentrations between surface and core fractions were small but consistent: mainly lithogenic metals (Al, and, within a serpentine derived soil, Ni and Cr) showed lower total concentrations in the surface than in the core fraction. Metals originating primarily from atmospheric deposition form two groups. Cadmium, Pb, and Zn usually showed higher total concentrations in the surface fraction whereas Cu, Cr, and Ni showed no uniform trends. In general, lower proportions of the total metal concentration could be extracted by the residual extraction step (mainly bound within silicates) in the surface than in the core fraction. Accordingly, higher proportions could be extracted by the sum of all other steps (bound to cation exchangers, organic matter, and oxides) in the surface fraction, although in the aggregate surface fraction the concentrations of organic matter and oxides as well as the CEC were lower than in the core fraction. The fact that the sorption capacity of the surface is lower than of the core fraction has to be considered for the identification of external metal inputs. Based on these results, a new method to identify external inputs is proposed.     

对矿区和冶炼区土壤重金属污染进行化学和矿物学特征分析

The binding of metallic contaminants （Pb, Cd, and Zn） and As on soil constituents was studied on four highly contaxninated alluvial soil profiles from the mining/smelting district of Pribram （Czech Republic） using a combination of mineralogical and chemical methods. Sequential extraction analysis （SEA） was supplemented by mineralogical investigation of both bulk samples and heavy mineral fractions using X-ray diffraction analysis （XRD） and scanning electron microscopy with an energy dispersive X-ray spectrometer （SEM/EDS）. The mineralogy of Fe and Mn oxides was studied by voltammetry of microparticles （VMP） and diffuse reflectance spectrometry （DRS）. Zinc and Pb were predominantly bound in the reducible fraction attributed to Fe oxides and Mn oxides （mainly birnessite, Na4Mn14O27.9H2O）, which were detected in soils by XRD and SEM/EDS. In contrast, Cd was the most mobile contaminant and was predominantly present in the exchangeable fraction. Arsenic was bound to the residual and reducible fractions （corresponding to Fe oxides or to unidentified Fe-Pb arsenates）. SEM/EDS observations indicate the predominant affinity of Pb for Mn oxides, and to a lesser extent, for Fe oxides. Thus, a more suitable SEA procedure should be used for these mining-affected soils to distinguish between the contaminant fraction bound to Mn oxides and Fe oxides.     

Assessment of Metal Availability in a Contaminated Soil by Sequential Extraction

A contaminated soil from Pieve Vergonte (Piedmont, Italy) has been investigated in order to point out the availability and extractability of a series of metal ions and consequently their potential release into other environmental compartments. A sequential extraction procedure has been adopted in order to subdivide total concentrations into five operational fractions with different potential toxicity. A chemometric analysis has been used for the characterization of similarities or differences of behaviour. High concentrations of the main pollutants, namely Cu, Pb and Zn, were extracted into the exchangeable, carbonate-bound/specifically adsorbed and Fe-Mn oxide bound fractions, showing the risk of release of these metals into the environment. A remobilization of Cr, Mn and Ni could also take place, but to a lesser extent. The other investigated metals (Al, Fe, La, Sc, V, Ti and Y) were mainly bound to the residual and, in some samples, to the Fe-Mn oxide bound fractions. The high availability of several potentially toxic metals shows that the soil needs remediation.     

Heavy metal pollution of soil from industrial and municipal wastes in Chittagong,Bangladesh

Heavy metal pollution was assessed in soils collected from 0–15, 15–30 and 30–45-cm depths of three industrial (FMC, PMC and CMC), and two municipal (BSD and MLF) waste disposal sites around Chittagong city in 2008. Soils were analysed for pH, organic carbon, total nitrogen, available P, exchangeable Ca, Mg, K and Na, and total Cd, Pb, Cu, Mn and Zn. The pH, organic C, total N, available P, total Cd, Pb, Cu and Mn, and contamination indices for Cd and Pb varied significantly among sites. Mean Cd, Pb, Cu, Mn and Zn were in the range 0.5–1.9, 54–86, 25–50, 261–624 and 204–330 mg kg^?1, respectively. Contamination indinces for Cd, Pb, Zn and Cu were estimated by comparison with respective threshold values. Contamination indices showed that the sites MLF and FMC had low Cu contamination. Other sites were not contaminated with thisheavy metal. All sites except PMC were highly contaminated with Cd, FMC was moderately contaminated and the others had low Pb contamination. FMC was highly contaminated, but the others were moderately contaminated with Zn. The integrated contamination index revealed that PMC had low contamination and the other sites were highly contaminated with heavy metals.     

Creation of Technosols to Decrease Metal Availability in Pyritic Tailings with Addition of Biochar and Marble Waste

Creation of Technosols with the use of different materials is a sustainable strategy to reclaim mine tailings and reduce metal mobility. For this purpose, a short‐term incubation experiment was designed with biochars derived from pig manure, crop residues and municipal solid waste added to tailings alone or in combination with marble waste. We aimed to assess the efficiency of the different amendments to decrease Cd, Pb and Zn availability in the Technosols and the fractions where metals were retained. Results showed that all amendments reduced metal mobility, directly related to increases in pH. Those materials with higher content of carbonates were more effective to immobilize metals (~99%). Municipal solid waste was highly effective to decrease metal mobility owing to the higher carbonate content, but addition of marble waste was needed to enhance metal immobilization with pig manure and crop residue. Decreases in Cd mobility were related to retention by the carbonate, Mn/Fe oxides and oxidizable (organic compounds) fractions. Decreases in Pb mobility were related to retention in the Mn/Fe oxides and residual fractions, while decreases in Zn mobility were related to retention in Mn/Fe oxides and oxidizable fractions. Association of Zn and Pb with the oxidizable fraction was also related to the recalcitrance of the organic compounds and so dependent on biochar type. Scanning electron microscopy coupled with energy dispersive X‐ray showed that biochar showed great affinity to interact with iron oxides, calcium sulfates and phyllosilicates. Copyright © 2017 John Wiley & Sons, Ltd.     

Fractionation of Cu, Pb, Cr, and Zn in a Soil Column Amended with an Anaerobic Municipal Sewage Sludge

The objective of this study was to investigate the changes in the chemical partitioning of Cu, Pb, Cr and Zn within a column of soil incubated with an anaerobic sewage sludge (ANSS) for 2.5 months. The soil was irrigated during the incubation period. A sequential extraction method was used to fractionate these metals into exchangeable, weakly adsorbed, organic, Al oxide, Fe–Mn oxide, and residual, respectively. ANSS was applied at a loading rate of 69 Mg ha^?1. The soil is a Dystric Cambisol with low pH (<3.8), low CEC [<10 cmol(+) kg^?1 below the first 4 cm depth], and low base saturation (<7%). The addition of the ANSS caused a decrease in concentrations of Cu, Pb, and Cr in the A1 horizon, and an increase in the concentrations with depth. Below the A1 horizon, concentrations of Cu increased uniformly (~1 mg cm^?1), and the greatest increases were observed in the residual, Fe–Mn oxides, and weakly adsorbed fractions. Maximum increases in Pb occurred at 4–9 cm of depth (1.6 mg cm^?1), and mainly affected the weakly adsorbed fraction. Chromium essentially accumulated at the limit between the A2 and the Bw horizons (1.1–1.5 mg cm^?1) as residual and organic bound forms, probably through particulate transport. Zinc mainly accumulated in the A1 horizon (2.9 mg cm^?1) as exchangeable Zn. At depth, Zn increments were predominantly observed in the residual fraction. The results of this study thus demonstrate the redistribution of contaminants into different chemical pools and soil layers after sludge amendment.     

Metal composition of soil,sediments, and urban dust and dirt samples from the Menomonee River Watershed,Wisconsin, U.S.A.

The Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents of the sand, silt, and clay fractions were determined for soils, urban street dust and bottom- and suspended-sediments sampled in the Menomonee River watershed, Wisconsin. The samples were dispersed by ultrasound prior to fractionation. The ultrasound dispersion avoids chemical contamination or alteration resulting from use of chemical dispersants and insures the dispersion of aggregates present in mechanically-sieved samples. Chemical analyses of fractionated samples were more precise than analyses of unfractionated samples in identifying areas in the watershed receiving pollutant inputs. Higher levels of Cr, Cu, Fe, and Ni were found in the coarser particles than in the finer particles of urban street dust samples. The Cd, Pb and Zn contents of some bottom and suspended sediments were greater than in the soils of the watershed. Contents of these metals were correlated significantly with each other in the clay-sized fraction of sediments but not in soils. The metal contents of sediments were largely controlled by vehicular emission.     

外源铜和镍在土壤中的化学形态及其老化研究

采用连续提取法测定了外源铜和镍进入田间土壤后的化学形态分布,比较研究了这2种重金属在3种不同类型土壤(红壤,水稻土和潮土)中随老化时间的形态转化和分布.结果表明,外源铜以残留态(40%～60%)和EDTA可提取态(40%)为主;随老化时间,EDTA可提取态、易还原锰结合态及铁铝氧化态向残留态转化;外源镍在酸性红壤中以可交换态(40%)和残留态(30%～50%)为主,在中性水稻土中以EDTA可提取态(30%)和残留态(30%～50%)为主,在碱性潮土中以铁铝氧化态(20%)和残留态(40%)为主.随老化时间,水溶态、可交换态、EDTA可提取态等向残留态转化.土壤pH较低时水溶态和可交换态含量较高,但是同时随老化时间的降低量也明显;pH较高时有利于易还原锰结合态和有机质结合态的转化.