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.     

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.     

Mikrosondenuntersuchungen an unterschiedlich stark mit Schwermetallen belasteten Böden. 2. Gehalte an Schwermetallen und anderen Elementen in Huminstoffaggregationen,Streustoffen und Holzkohlepartikeln

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.     

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.     

Source Identification and Speciation of Metals in the Topsoil of the Khli Ti Watershed, Thailand

The enrichment factor, multivariate analysis and metal speciation studies were used to identify degree, source and dispersal of metal contamination in Khli Ti watershed, Thailand. Topsoil samples were collected throughout the watershed, analyzed for total metal concentration. Sequential extraction was also carried out to determine geochemical phases of metals which were identified as exchangeable and bound to carbonates, Fe–Mn oxides, organic matter and residuals. Soil characteristics including pH, total organic carbon, redox potential, cation exchange capacity and texture were also analyzed. Principal component analysis yielded three metal groups which explained 83% of the variance. The concentrations of metals which were derived from lithogenic origin, such as Co, Cr, Fe, Ni and V were in natural background levels and were mostly bound to the residual phase. The remaining elements (i.e. Ba, Cd, Cu, Pb, Sb and Zn) were associated with the contamination from previous activities of the Pb-ore concentrator and Zn–Pb mining. Anthropogenic contamination mainly increased Pb and Zn bound to Fe–Mn oxides at the expense of residual fraction. Even though low exchangeable Pb contents in Khli Ti soils indicated low availability to plants, Pb bound to Fe–Mn oxides fraction might increase its mobility under reducing conditions.     

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.     

土壤可见光-近红外反射光谱与重金属含量之间的相关性

发展基于反射光谱技术的快速、简便、低成本的土壤重金属信息提取方法是区域土壤重金属污染治理所需要的。选择江西贵溪铜冶炼厂污染区,分析了9种重金属元素(Cu、Pb、Zn、Cd、Co、Ni、Fe、Mn及Cr)与土壤可见光-近红外反射光谱之间的相关性及其相关的原因。研究表明,研究区土壤中存在Cu(含量介于66.71~387 mg kg-1之间)和Cd(含量介于0.36~6.019 mg kg-1之间)的强烈富集。土壤重金属含量与反射光谱之间存在显著相关,污染元素Cu的最高相关系数为-0.87,Pb、Zn、Co、Ni、Fe的最高相关系数达到高度相关(|r|>0.80),Cr、Cd、Mn的最高相关系数达到显著相关(|r|>0.70)。微分光谱适于获取土壤中的重金属元素信息,利用组合波段能显著提高相关性。Cu与反射光谱之间的相关性主要受有机质的影响;Pb、Zn、Co、Ni主要受黏土矿物和铁锰氧化物的影响;Cr与反射光谱之间的相关性同时受有机质和黏土矿物的影响。     

Use of the BCR three-step sequential extraction procedure for the study of the partitioning of Cd, Pb and Zn in various soil samples

A slightly modified three-step sequential extraction procedure proposed by the Community Bureau of Reference (BCR) for analysis of sediments was successfully applied to soil samples. Contaminated soil samples from the lead and zinc mining area in the Mezica valley (Slovenia) and natural soils from a non-industrial area were analysed. The total concentrations of Cd, Pb and Zn and their concentrations in fractions after extraction were determined by flame or electrothermal atomic absorption spectrometry (FAAS, ETAAS). Total metal concentrations in natural soils ranged from 0.3 to 2.6 mg kg^-1 for Cd, from 20 to 45 mg kg^-1 for Pb and from 70 to 140 mg kg^-1 for Zn, while these concentrations ranged from 0.5 to 35 mg kg^-1 for Cd, from 200 to 10000 mg kg^-1 for Pb and from 140 to 1500 mg kg^-1 for Zn in soils from contaminated areas. The results of the partitioning study applying the slightly modified BCR three-step extraction procedure indicate that Cd, Pb and Zn in natural soils prevails mostly in sparingly soluble fractions. Cd in natural soils is bound mainly to Fe and Mn oxides and hydroxides, Pb to organic matter, sulphides and silicates, while Zn is predominantly bound to silicates. In contaminated soils, Cd, Pb and Zn are distributed between the easily and sparingly soluble fractions. Due to the high total Cd, Pb and Zn concentrations in contaminated soil close to the smelter, ! and their high proportions in the easily soluble fraction (80% of Cd, 50% of Pb and 70% of Zn), the soil around smelters represents an environmental hazard.     

水稻子实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属(Cd、Cr、Pb、Cu、Zn)全量、各形态含量及相应点位种植的水稻子实重金属含量的基础上,通过统计分析、空间插值及线性回归方程的模拟,研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征,以及水稻子实对重金属各形态的累积差异及其影响因素。结果表明,成都平原水稻土重金属污染较轻,除Cd外,均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低,Cd主要以铁锰氧化态存在,Cr、Cu、Zn、Pb主要以残渣态存在。水稻子实对5种重金属的累积效应顺序为:Cd>Zn>Cu>Pb>Cr。与水稻重金属累积关系密切的重金属活性形态(可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态)主要有:Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量;Zn各活性形态对水稻子实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响;活性态Cr与pH、有机质、CEC和容重密切相关;活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系;Cu的活性主要受粘粒、有机质含量的影响;Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来,对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重,而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

华中黄棕壤和黄褐土粘粒胶膜的微量元素地球化学特征

The relationships between the basic properties and trace elementsin soil argillans and corresponding matrix soils were studied by sampling from the B horizons of 26 Alfisols in croplands of the subtropical area in Central China. The soil elements (K, Na, Ca, Mg, Mn, Co, Cu, Cr, Cd, Li, Mo, Ni, Pb, Ti, V, and Zn) were extracted by acid digestion and their contents were measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The mean contents of clay and organic matter in the argillans were approximately 1.1 and 1.3 times greater than those in the matrix soils, respectively. The pH values and the contents of P₂O₅ and bases (K₂O, Na₂O, CaO, and MgO) in the argillans were higher than those in the corresponding matrix soils. Cu, Cd, Ti, and V were enriched in the argillans. Correlation coefficients and factor analyses showed that Co, Cu, Li, and Zn were bound with phyllosilicates and manganese oxides (Mn-oxides) in the argillans. Cr and Pb were mainly associated with iron oxides (Fe-oxides), while Ni was bound with Mn-oxides. Cd, Ti, and V were chiefly associated with phyllosilicates, but Cr and Mo were rarely enriched in the argillans. In contrast, in the matrix soils, Co and Zn were associated with organic matter and Fe-oxides, Cr existed in phyllosilicates, and Mo was bound to Fe-oxides. Cd, Ti, and V were associated with organic matter. The results of this study suggest that clays, organic matter, and minerals in the argillans dominate the illuviation of trace elements in Alfisols. Argillans might be the active interfaces of elemental exchange and nutrient supply in cropland soils in Central China.     

Trace metal content of the forest floor in the green mountains of Vermont: Spatial and temporal patterns

The organic horizons of forest soils in eleven stands along an elevational gradient on Camels Hump Mountain, Vermont, were analyzed for Pb, Cu, Zn, Ni, Cd, organic matter and organic C. Lead concentration and amount increased with elevation. Vertical profiles of forest floor in the boreal forest showed that highest concentrations for most metals occurred in the upper F horizon. Comparison with 1966 and 1977 samples from the same stands showed that concentrations of Pb, Cu, and Zn and percent organic matter increased by as much as 148% in the intervening 14 yr. Estimates of 1966 amounts of Pb, Cu, and Zn indicated that increases in trace metal amounts over the 14 yr period are consistent with annual deposition rates reported in the literature.     

Forms of Iron and Their Association with Soil Properties in Four Soil Taxonomic Orders of Arid and Semi‐arid Soils of Punjab,India

Profiles of arid and semi‐arid zones soils of Punjab, northwestern India, were investigated for different forms of iron (Fe): total Fe, diethylenetriamine penta‐acetic acid (DTPA)–extractable Fe, soil solution plus exchangeable Fe, Fe adsorbed onto inorganic sites and oxide surfaces, and Fe bound by organic sites. Irrespective of the different fractions of Fe present, its content was higher in the fine‐textured Alfisols and Inceptisols than in the coarse‐textured Entisols and Aridisols. Lower content of total Fe was observed in the surface horizon and then increased in the subsurface horizons, whereas no set pattern was observed in Entisols. Also, irrespective of the soil orders, the contents of different forms of Fe were higher in the surface horizon and then decreased by depth. None of the forms of Fe exhibited any consistent pattern of distribution.

Organic matter and the content of clay and silt fractions had a strong bearing on the distribution of forms of Fe. Based on a linear coefficient of correlation, the soil solution plus exchangeable Fe adsorbed onto inorganic sites and DTPA‐extractable Fe increased with increase in soil organic carbon but decreased with increase in soil pH and calcium carbonate content. Total Fe increased with increase in cation exchange capacity (CEC) and clay and silt content. The results also revealed that there was equilibrium in different fractions of this element. Among the different Fe forms, Fe bound by organic sites, water‐soluble plus exchangeable Fe, and Fe adsorbed onto oxides (amorphous surfaces) were positively correlated with the DTPA‐extractable Fe. Though some forms are interrelated, none of the forms had any relationship with the total Fe.     

Spurenelemente in Bodensequenzen II. Zwei Pararendzina – Pseudogley – Sequenzen aus Löß

Trace elements in pedosequences II. Two Pararendzina-Pseudogley-sequences on loess Total amounts and fractions of Cu, Zn, Pb, Cd, Co and Ni extractable in boiling oxalate (replacing dithionite for analytical reasons), oxalate at room temperature and EDTA were determined in two hydro-pedosequences on loess ranging between Pararendzina-Braunerde-Parabraunerde-Pseudogley. The pedogenic influence on the depth functions of these trace elements was much weaker in the loess soils than in those on slates of part I of this study. With a few exceptions external additions seem to be masked by soil cultivation. Clay movement (Alfisols) produced maxima of Fe and Cu in the B_t horizon. Carbonates of the parent loess contain trace elements which are released into the soil during solum formation. As long as they exist in carbonates they are hardly extractable with oxalate but with EDTA. In contrast, after pedogenic decomposition of the carbonates in the B horizon their trace elements are now oxalate but no longer EDTA extractable. In the A horizon, where organic matter is involved the trace elements are again EDTA extractable. As in the soils from slate (part I) Cd behaves more similarly to Pb than to Zn. The total element balance indicates a slight gain of Pb and loss of Zn whereas the total amount of the other elements was essentially unchanged. Generally, the more mobile fractions increased during soil formation.     

Forms of Cu (II), Zn (II), and Pb (II) compounds in technogenically transformed soils adjacent to the Karabashmed copper smelter

Purpose

The aim was to study Cu (II), Zn (II), and Pb (II) forms in technogenically transformed soils adjacent to the Karabashmed copper smelter.

Materials and methods

Studies were performed in the plume zone of the Karabash smelter and in the floodplains of Ryzhii Brook and Sak-Egla River. Geomorphological and geochemical migration processes prevail in technogenic landscapes. The differentiation of landscape-geochemical conditions plays the dominant role, which determines the localization of metals. The total Mn, Cr, Ni, Cu, Zn, Pb, Cd, and As contents and the macroelement compositions of soils were determined by X-ray fluorescence. The composition of Cu, Pb, and Zn compounds in soils was determined by the Tessier sequential fractionation. The determination of the geochemical fractions of heavy metals in soils is a key issue in the study of their mobility. The metals were fractionated into the following five fractions: exchangeable, bound to carbonates, bound to Fe and Mn oxides, bound to organic matter, and residual fractions.

Results and discussion

It is shown that the total Zn and As contents in the 0- to 5-cm layer of soils on monitoring plots exceed their lithosphere clarks in hundreds of times, and the total Cu, Pb, and Cr contents exceed their lithosphere clarks in tens of times. Factors and processes controlling the distribution and transport of Cu, Pb, and Zn forms in soils were determined. According to landscape-geochemical differentiation, the eluvial (automorphic) catena (plot T4) takes the main technogenic load of dust fallouts from the Karabash copper smelter. The accumulation of material brought from above and the geochemical precipitation of discharges from tailings dumps occur in superaqual catenas (plots T1, T2, and T3). In the technogenically transformed soils, the basic stabilizers of the mobility of Cu is organic matter, for Pb it is Fe-Mn (hydro) oxides, and for Zn - it is clay minerals.

Conclusions

The distributions of Cu, Zn, and Pb forms in the studied technogenically transformed soils are due to a number of factors: First, these are the composition of technogenic pollutants contaminating ecosystems and the time during which the contamination occurred, and second, this is the combination of physicochemical properties controlling the buffer properties of the polydisperse system of soils and parent materials.

     

Bulk sediment bioassays with five species of fresh-water oligochaetes

The fluxes of metals (Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Pb, Cd, Cr, and Ni) in two spruce forest soils in S. Sweden were quantified using the lysimeter technique. Amounts in precipitation (dry and wet), throughfall, litterfall and annual accumulation in biomass were also quantified, as well as stores in soil and biomass. The metal concentrations of the soil solutions varied greatly according to season. The leaching of some metals (Fe, Cu, Pb, Cr, and organic forms of Al) was associated with the leaching of organic matter. These complexes were leached from the A horizon in considerable amounts. They were precipitated in the upper B horizon and only small amounts were transported further downward. By contrast, the leaching of Na, Mg, Ca, Mn, Cd, Zn, Ni, and inorganic forms of Al increased with increasing soil depth. The concentrations of these metals also increased with increasing soil solution acidity. The highest concentrations were often found at the transition to the C horizon. The amounts of Na, K, Mg, Ca, Mn, Al, Zn, Cd, Cr, and Ni leached from the rooting zone were found to be larger than the amounts deposited from the atmosphere, the main source of these metals being the mineral soil. The reverse was true of Ph, Cu, and Fe, the sink being the upper part of the B horizon.     

Spurenelemente in Bodensequenzen I. Zwei Braunerde-Podsol-Sequenzen aus Tonschieferschutt

Trace elements in pedosequences I. Two Braunerde-Podsol-sequences on slate Total amounts and fractions of Fe, Cu, Zn, Pb, Cd, Co and Ni extractable in boiling oxalate (replacing dithionite for analytical reasons), oxalate at room temperature and EDTA were determined in two pedosequences on slates ranging between Braunerde (Ochrept) and Podsol (Spodosol). The total amounts lay within the normal range of these elements in slates except a few samples much higher in Zn and Cd due to sulphides in the rock. In surface soil horizons rich in organic carbon the trace elements are accumulated in the order Cu < Zn < Cd < Pb. This accumulation increased with increasing degree of podsolization but is also partly due to atmospheric input. The relative accumulation of the various fractions in the surface soil increased in the order: boiling oxalate < room temperature oxalate < EDTA. Along the same order the depth function is determined to increasing extent by pedogenic processes rather than by lithogenic differences. In contrast to Fe, no minima in the podsol A₂ nor definite maxima in the B were noticed for Cu, Zn, Pb and Cd. With regard to the affinity towards organic matter Cd appears to behave more similarly to Pb than to Zn. Co and, even more so, Ni were lost during podsolization. The significance of the fractionation procedure which was very useful with Fe was not satisfying with the trace elements. Relationships between single element fractions and various soil components were generally poor except for that between the EDTA fraction and organic matter content. The total element balance is complicated by the heterogenity of the parent rock, but an increase in the mobile fractions in the solum during podsolization is generally indicated. There was a loss in the total amount of Fe, Cu, Zn, Co and Ni due to podsolization whereas a gain for Pb and Cd was noticed most probably through atmospheric intake.     

新乡市寺庄顶污灌区土壤中重金属的形态分布及生物有效性研究

对长期电池废水灌溉的新乡市寺庄顶污灌区和对照区土壤重金属进行取样分析,结果表明,对照区土壤中Cd,Ni,Zn,Cu和Cr含量都能达标,污灌区土壤中Cr含量能达标,Cd,Ni,Zn和Cu的含量超标,其平均含量分别为65.31,1 196.64,2 799.25,145.78 mg/kg,是国家土壤环境质量二级标准的108.85,19.94,9.33和1.46倍。形态分析结果表明,污灌区污染最严重的Cd主要以铁-锰氧化物结合态存在,所占比例平均为56.84%;Ni主要以铁-锰氧化物结合态和残余态存在,所占比例平均为37.44%和39.55%;Zn主要以残余态存在,所占比例平均为78.24%;Cu主要以有机结合态存在,所占比例平均为57.70%;Cr主要以有机结合态和残余态存在,所占比例平均为45.55%和34.18%。与对照相比,污灌降低了Cd,Ni,Zn,Cu和Cr残余态所占比例,提高了重金属迁移能力和生物有效性。在4种超标重金属中Cd可交换态所占比例最高,平均为24.54%,由于其生物有效性最高,Cd迁移能力和植物毒性最值得关注。     

Contents and chemical forms of heavy metals in school and roadside topsoils and road-surface dust of Beijing

Purpose

The concentration of human activities in urban systems generally leads to urban environmental contamination. Beijing is one of ancient and biggest cities on the world. However, information is limited on Beijing’s soil contamination, especially for roadside and campus soils. Thus, the aims of this study were to investigate the contents and chemical forms of toxic heavy metals Cd, Cr, Cu, Ni, Pb, and Zn in the road-surface dust, roadside soils, and school campus soils of Beijing. In addition, enrichment and spatial variation of these toxic heavy metals in the soils and dust were assessed.

Materials and methods

Topsoil samples were collected from the schools and roadside adjacent to main ring roads, and dust samples were collected from the surface of the main ring roads of Beijing. These samples were analyzed for total contents and chemical forms of Cd, Cr, Cu, Ni, Pb, Sc, Zn, Al, and Fe. Enrichment factors (EFs, relative to the background content) were calculated to evaluate the effect of human activities on the toxic heavy metals in soils.

Results and discussion

Heavy metal contents in the road dust ranged from 0.16 to 0.80, 52.2 to 180.7, 18.4 to 182.8, 11.9 to 47.4, 23.0 to 268.3, and 85.7 to 980.9 mg kg^?1 for Cd, Cr, Cu, Ni, Pb, and Zn, respectively. In the roadside soil and school soil, Cd, Cr, Cu, Ni, Pb, and Zn contents ranged from 0.13 to 0.42, 46.1 to 82.4, 22.7 to 71.6, 20.7 to 29.2, 23.2 to 180.7, and 64.5 to 217.3 mg kg^?1, respectively. The average EF values of these metals were significantly higher in the dust than in the soils. In addition, the average EF values of Cd, Cu, Pb, and Zn in the soils near second ring road were significantly higher than those near third, fourth, and fifth ring roads. Anthropogenic Cd, Pb, and Zn were mainly bound to the carbonates and soil organic matter, while anthropogenic Cu was mainly bound to oxides. The mobility and bioavailability of these metals in the urban soils of Beijing generally decreased in the following order: Cd?>?Zn?>?Pb?>?Cu?>?Ni?>?Cr; while in the dust, they decreased in the following order: Zn, Cu, and Cd?>?Pb?>?Ni?>?Cr.

Conclusions

Both EF and chemical forms documented that Cr and Ni in the soils and dust mainly originated from native sources, while Cd, Cu, Pb, and Zn partially originated from anthropogenic sources. In overall, Beijing’s road dust was significantly contaminated by Cd and Cu and moderately contaminated by Cr, Pb, and Zn, while Beijing’s roadside soil and school soil were moderately contaminated by Cd and Pb. However, the maximal hazard quotients (HQs) for individual Cd, Cr, Cu, Ni, Pb, and Zn and comprehensive hazard index (HI) of these metals in the dust and soil were less than 1, indicating that the heavy metals in the dust and soil generally do not pose potential health effects to children, sensitive population.     

The relationship between copper accumulated in vineyard calcareous soils and soil organic matter and iron

The intensive use for over 100 years of copper sulphate (Bordeaux mixture) to fight mildew in vineyards has led to a substantial accumulation of copper (Cu) in surface soils. To assess the effects of such large concentrations, the surface soils of 10 Burgundy vineyards were sampled and analysed for total organic matter (carbon and nitrogen) and metal (copper and iron) contents. Physical (i.e. size fractionation) and chemical (sequential extraction) methods were used to determine the distribution of these elements. The most Cu‐contaminated plots showed the largest accumulation of organic carbon and Cu in the coarse sand and fine sand fractions. Copper was strongly correlated with organic carbon and organic nitrogen in the coarse sand fraction and with organic nitrogen in the fine sand fraction. Copper was also highly correlated with both Fe and organic nitrogen in the clay fraction but not significantly with organic carbon. The sequential extraction showed that Cu was bound mainly to the Fe oxides. However, in the most Cu‐contaminated plots, a part of added Cu was bound to organic matter. This study suggests that Cu protected indirectly the organic matter present in the coarse fractions against biodegradation, and therefore modified the distribution of organic carbon among the particle‐size fractions. Iron appeared as the main factor responsible for Cu accumulation in the clay fraction, mainly through inclusion of Cu in Fe oxyhydroxides and possibly in clay–humus complexes.