Heavy metal contamination of soils in Northern Slovakia

Environmental damages like forest decline in Northern Slovakia could be a result of long-distance transport of pollutants with the dominating north-west winds. On 10 sites, primarily in the northbound upper slopes of west-east oriented mountain ranges in Northern Slovakia, the extent of the heavy metal contamination in soils along a north-south transect was examined. Oi, Oe, Oa, A, and B horizons were sampled and the total concentrations of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined. The ranges of heavy metal concentrations in the forest floor were higher than reported for comparable samples from Bavarian soils except for Zn (Cd: 0.65–1.77; Cr: 12–40; Cu: 19–41; Ni: 8–24; Pb: 70–187; Zn: 31–92 mg kg^?1), in the mineral soil the concentrations were lower. The depth distribution of the metal concentrations indicated a contamination with Cd, Cr, Cu, Ni, Pb, and Zn. The concentration differences between forest floor and mineral soil tended to be higher at the northern than at the southern sites for Cu, Ni, Pb, and Zn, indicating a long-distance transport from the north. Correlation and principal component analyses of the total metal concentrations revealed three groups: Cu, Pb, and Zn inputs mainly seemed to result from long-distance transport from the north, Cr and Ni inputs additionally from local sources. Cd probably had its origin mainly in local sources. This result was further confirmed by the grouping of the sites when clustered.     

包头市铜厂周边土壤中重金属垂直分布特征与形态分析

为了解包头市铜厂周边地区土壤剖面中重金属污染状况,采用火焰原子吸收分光光度法和Tessier连续提取法,对土壤中6种重金属（Cu,Zn,Mn,Ni,Pb和Cd）的垂直分布特征、形态及潜在生物可利用性进行了分析。结果表明:研究区土壤剖面各层土壤中6种重金属含量均超过内蒙古土壤背景值,Cu,Pb和Cd为主要污染物。随采样深度的增加,Cu,Zn,Pb和Mn的含量呈现下降趋势,且由相关性系数可知重金属Cu,Zn和Pb可能有相同人为或自然污染源;土壤剖面中6种重金属均主要以残渣态存在,含量均在50%以上,对生物危害较小;潜在生物可利用性分析结果为:Cu（32.61%） > Mn（31.85%） > Ni（24.90%） > Zn（16.60%） > Cd（15.23%） > Pb（14.87%）,Cu和Mn的潜在生物可利用性较大,其次为Ni,Zn,Cd和Pb潜在生物可利用性较小。     

新乡市大棚菜田土壤重金属积累特征及污染评价

采用微波消解-ICP-AES技术,测定不同种植年限大棚菜田土壤样品中As、Pb、Zn、Cd、Cr、Mn、Ni、Cu等重金属的含量,研究不同种植年限与大棚菜田土壤重金属累积的相关性以及大棚菜田土壤重金属累积特征,并利用地积累指数法进行污染评价。结果表明:大棚菜田土壤重金属Zn、Pb、Ni、Mn和Cu的含量与种植年限具有极显著相关性;大棚菜田土壤中重金属Cd和Cr的含量与种植年限不相关。重金属元素间相关性分析表明,Zn与Pb、Cd、Ni、Mn、Cr、Cu,Pb与Cd、Ni、Mn、Cr、Cu,Cd与Ni、Mn、Cr,Ni与Mn、Cr、Cu,Mn与Cr、Cu具有污染同源性,Cu与Cd、Cr不具有污染同源性。地积累指数法污染评价结果显示Cd的污染等级达到了6级,已构成了极严重污染;Zn和Cu的污染等级达到2级,已构成了中度污染;Pb、Mn的污染等级达到1级,已经构成了轻~中度污染;As、Ni、Cr均未构成污染。     

杭州市城市土壤中重金属、磷和其它元素的特征

Health implications of inhaling and/or ingesting dust particles with high concentrations of heavy metals from urban soils are a subject of intense concern. Understanding the geochemistry of these metals is key to their effective management. Total concentrations of heavy metals, phosphorus (P) and 8 other elements from topsoil samples collected at 82 locations in Hangzhou City were measured to: a) assess their distribution in urban environments; and b) understand their differentiation as related to land use. Metal mobility was also studied using a three-step sequential chemical fractionation procedure. About 8.5%, 1.2%, 3.6%, 11.0% and 30.3% of the soil samples had Cd, Cr, Cu, Pb, and Zn concentrations, respectively, above their allowable limits for public and private green areas and residential use. However, in commercial and industrial areas, most samples had metal concentrations below their allowable limits. Statistical analyses revealed that the 16 measured elements in urban soils could be divided into four groups based on natural or anthropic sources using a hierarchical cluster analysis. Additionally, Cu, Pb, and P showed similar spatial distributions with significant pollution in commercial zones, suggesting vehicle traffic or commercial activities as dominant pollutant sources. Also, Cd, Co, Cr, Ni, Zn, Mn and Fe had the highest concentrations in industrial locations, signifying that industrial activities were the main sources of these seven metals. Moreover, the data highlighted land-use as a major influence on heavy metal concentrations and forms found in topsoils with large proportions of soil Cd, Co, Cr, and Ni found in residual fractions and soil Cu, Pb and Zn mainly as extractable fractions.     

博斯腾湖湿地边缘带农田土壤重金属的污染风险评价

对新疆博斯腾湖湿地边缘带农田土壤中8种重金属元素(As、Cd、Cr、Cu、Mn、Ni、Pb和Zn)地球化学特征进行分析。采用污染负荷指数(PLI)、潜在生态风险指数(RI)和生态风险预警指数(IER)对农田土壤重金属污染与环境风险进行评价。结果表明:(1)湿地边缘带农田土壤Pb和Zn呈现重度污染,As、Cd、Cr和Ni轻度污染,Cu轻微污染,Mn无污染。土壤As、Cd、Cr、Cu、Ni、Pb和Zn平均含量处于轻微风险水平。Cd是污染程度与生态风险等级最高的重金属元素;(2)湿地边缘带农田土壤PLI平均值为1.43,呈现轻度污染,RI平均值为20.62,呈现轻微生态风险状态,IER的平均值为–4.53,呈现无警态势。湿地边缘带PLI、RI与IER空间分布格局基本一致;(3)湿地边缘带农田土壤Pb与Zn来源主要受到人类活动的影响,Cr、Cu、Mn与Ni来源主要受到土壤地球化学作用的控制,As与Cd受自然因素和人为因素共同影响。     

Pollution and Ecological Risk Assessment of Heavy Metals in Farmland Soils in Yanqi County,Xinjiang, Northwest China

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

太原市污灌区土壤重金属污染现状评价

对太原市污灌区土壤重金属分布特征进行了分析评价,结果表明重金属Pb、Zn、Cu、Ni、Mn、Cr、As、Hg、Cd含量均值均未超过土壤环境质量标准（GB15618—1995）,但其平均值均显著高于太原市土壤背景值。各重金属间的相关分析表明,Pb、Zn、Cu、Ni、Mn、Cr、As、Cd之间呈极显著相关,说明这8种元素污染源可能相同。Hg是本区表层土壤重金属污染的主要因子,重金属元素的污染程度依次为Hg〉Cd〉Pb〉As〉Cu〉Zn〉Cr〉Mn〉Ni。土壤重金属单项污染指数均值均大于1,综合污染指数为2.81,总体上,污染水平为中度及其以上。各种重金属单因子污染指数和综合指数在研究区有相似的空间分布格局,总体分布趋势为东南部小店地区和中南部晋源区相对较高,南部清徐县相对较小;通过因子分析并结合污灌区污染源调查,表明Hg除受污水灌溉的影响外,燃煤释放的Hg可能是重要来源之一,Cd、Zn、Pb和Cu可能来自污水灌溉和大气沉降,以污水灌溉的贡献为主,Ni、Mn、As、Cr来自污水灌溉。Hg、Cd是太原市污灌区土壤中需要优先控制的重金属。     

Heavy Metals in Freshly Deposited Stream Sediments of Rivers Associated with Urbanisation of the Ganga Plain,India

Freshly deposited stream sediments from six urban centres of the Ganga Plain were collected and analysed for heavy metals to obtain a general scenery of sediment quality. The concentrations of heavy metals varied within a wide range for Cr (115–817), Mn (440–1 750), Fe (28 700–61 100), Co (11.7–29.0), Ni (35–538), Cu (33–1 204), Zn (90–1 974), Pb (14–856) and Cd (0.14–114.8) in mg kg^-1. Metal enrichment factors for the stream sediments were <1.5 for Mn, Fe and Co; 1.5–4.1 for Cr, Ni, Cu, Zn and Pb; and 34 for Cd. The anthropogenic source in metals concentrations contributes to 59% Cr, 49% Cu, 52% Zn, 51% Pb and 77% Cd. High positive correlation between concentrations of Cr/Ni, Cr/Cu, Cr/Zn, Ni/Zn, Ni/Cu, Cu/Zn, Cu/Cd, Cu/Pb, Fe/Co, Mn/Co, Zn/Cd, Zn/Pb and Cd/Pb indicate either their common urban origin or their common sink in the stream sediments. The binding capacity of selected metals to sediment carbon and sulphur decreases in order of Zn > Cu > Cr > Ni and Cu > Zn > Cr > Ni, respectively. Stream sediments from Lucknow, Kanpur, Delhi and Agra urban centres have been classified by the proposed Sediment Pollution Index as highly polluted to dangerous sediments. Heavy metal analysis in the <20-μm-fraction of stream sediments appears to be an adequate method for the environmental assessment of urbanisation activities on alluvial rivers. The present study reveals that urban centres act as sources of Cr, Ni, Cu, Zn, Pb and Cd and cause metallic sediment pollution in rivers of the Ganga Plain.     

Heavy Metals, Phosphorus and Some Other Elements in UrbanSoils of Hangzhou City, China

Health implications of inhaling and/or ingesting dust particles with high concentrations of heavy metals from urbansoils are a subject of intense concern. Understanding the geochemistry of these metals is key to their effective management. Total concentrations of heavy metals, phosphorus (P) and 8 other elements from topsoil samples collected at 82locations in Hangzhou City were measured to:a) assess their distribution in urban environments;and b) understand theirdifferentiation as related to land use. Metal mobility was also studied using a three-step sequential chemical fractionationprocedure. About 8.5%, 1.2%, 3.6%, 11.0% and 30.3% of the soil samples had Cd, Cr, Cu, Pb, and Zn concentrations,respectively, above their allowable limits for public and private green areas and residential use. However, in commercialand industrial areas, most samples had metal concentrations below their allowable limits. Statistical analyses revealedthat the 16 measured elements in urban soils could be divided into four groups based on natural or anthropic sourcesusing a hierarchical cluster analysis. Additionally, Cu, Pb, and P showed similar spatial distributions with significantpollution in commercial zones, suggesting vehicle traffic or commercial activities as dominant pollutant sources. Also, Cd,Co, Cr, Ni, Zn, Mn and Fe had the highest concentrations in industrial locations, signifying that industrial activities werethe main sources of these seven metals. Moreover, the data highlighted land-use as a major influence on heavy metalconcentrations and forms found in topsoils with large proportions of soil Cd, Co, Cr, and Ni found in residual fractionsand soil Cu, Pb and Zn mainly as extractable fractions.     

Changes of Al and Heavy Metal Concentrations in Slovak Soils During the Last 25 Years

The objective of this study was to investigate changes of total concentrations and various extract-defined Al and heavy metal fractions in Slovak agricultural soils during the last 25 years. We compared 7 stored soil samples collected between 1966 and 1970 with samples collected in 1994 at the same sites. Seven fractions of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined with a sequential extraction procedure in all samples. Total concentrations of Cd, Zn, Mn, Ni, and Cu were lower in the 1994 samples; those of Al, Fe, Pb, and Cr were higher. Based on the initial concentrations, the average total concentration changes were: Cd(-10,3%)<Zn(-7,2%)<Mn(-4,8%)<Ni(-2,3%)<Cu(-1,4%)<Al(+2,1%)<Fe(+2,9%)<Cr(+7,4%)<Pb(+8,3%). This row is consistent with the decrease in metal mobility. The differences in salt-extractable metals showed the same pattern; however, changes were more pronounced than for total concentrations. The results suggest that decreases during the last 25 years are caused by higher leaching than deposition rates and increases vice versa. The highest increase in Cr and Pb concentrations is observed in the EDTA-extractable fraction, which mainly characterizes organically bound metals.     

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。     

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.     

Flüssebilanzen und aktuelle Änderungsraten der Schwermetall-Vorräte in Wald-Ökosystemen des Soiling

Flux balances and current rates of change of heavy metal stores in forest ecosystems of the Soiling The inventory of the heavy metals Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb is calculated for a beech and a spruce forest ecosystem in the Soiling mountains on the basis of measured concentrations in the vegetation and soil compartments and their dry mass per hectare. The inventory is compared with measured heavy metal fluxes coupled with precipitation above and below the canopy, with seepage water fluxes below the rooting zone (50 cm depth), with litterfall, and with the current increment to biomass. The ratios between heavy metal stores in the forest floor layers (table 3) and the annual flux with litterfall (table 4) show decreasing tendency for liberation of the elements by decomposition of organic matter (OM) in the following order: Mn>OM>Ni>Cd>Cu>Cr ≈? Zn>Co ≈? Fe ≈? Pb Manganese is set free faster than total organic matter. The flux balances for the total ecosystems (table 4) show input > output in the case of Cr, Fe, Cu, Cd, and Pb; input ≈? output for Ni and Zn; input < output for Mn and Co. Heavy metal stores in mineral soil are decreasing by percolation losses and increment to biomass (mainly wood) in the case of all elements investigated, except Zn (under beech), Cd and Pb (table 4). The concentrations of Cu and Pb in the forest floor layers have reached levels at which deleterious effects on microorganisms and litter decomposition are to be expected.     

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.     

Behavior of heavy metals from sewage sludge in a Chernozem of the dry belt in Saxony‐Anhalt/Germany

In a small‐plot trial different doses of sewage sludge (equivalent 82‐330 tons of dry matter per hectare) were incorporated in 0—25 cm depth (1982—1985). The aim of the investigations was to study the fate of the heavy metals Zn, Cd, Cu, Ni, Pb, and Cr, to determine their concentration in different soil fractions using a sequential extraction method and to ascertain their uptake by Zea mays L. plants. Eleven years after the last application the metals supplied with the sludge had moved as far as 50 cm in depth. The concentrations of Zn, Cd, Cu, Ni, and Cr in the saturation extract of the sampled soil layers were closely correlated with the concentrations of dissolved organic carbon (DOC). This result suggests that the heavy metal displacement was partly connected with the DOC movement in the soil. Considerable amounts of Zn and Cd coming from sewage sludge were found in the mobile fractions of the soil. Cu, Ni, and Pb were located especially in organic particles, and Cr was obviously bound by Fe‐oxides. Nine years after the last application the binding species of heavy metals were still different compared with those in the untreated soil. The whole withdrawal of heavy metals by plants yielded <1 % of the applied amounts. In the case of Zn the uptake from the sludge amended soil decreased during the experimental period. No similar tendency was observed for the other elements. In any case their annual variations of uptake exceeded the effect of sludge application.     

Die räumliche Variabilität von Schwermetall-Konzentrationen in Niederschlägen und Sickerwasser von Waldstandorten des Sollings

Local variability in the heavy metal concentrations of precipitation and seepage water from forest sites in the Solling Concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in precipitation and seepage water have been measured continuously with local replicates during a 6-months period at a beech and a spruce forest site. Variation coefficients of the avarage concentrations were, in most cases, well below 30 %, being mainly caused by local differences. Comparison of means showed a significant increase of heavy metal concentration in the canopy drip of beech (Mn, Fe, Pb) and spruce (Cr, Mn, Fe, Ni, Zn, Pb) compared to bulk precipitation measured in the open field. Concentration of Mn, Co, Ni, Zn and Cd in the seepage water is significantly higher under spruce compared to beech. These results point at higher filter efficiency of the spruce canopy, compared with beech, for air pollutants, but a smaller retention capacity of the soil under spruce for heavy metals.     

Influence of prolonged use of sewage effluent in irrigation on heavy metal accumulation in soils and plants

Total content of Fe, Mn, Zn, Cu, Pb, Cd, Ni and Co in soils irrigated with sewage effluent increased with increasing years of using sewage effluent in irrigation. Iron and Co applied to the soil from sewage effluent were immobilized mainly in unavailable form; Pb, Cd, and Ni in moderately available form; and Mn, Zn, and Cu in highly available form. The concentrations of Fe, Mn, Zn and Cu in tops of alfalfa and leaves of corn grown on these soils increased substantially with increased levels of available metal content of the soil, while those of other metals were little affected. As for orange, continuous increase in leaves metal content with time was found for Fe, Mn, Zn, Co and Cd. The concentrations of Cd, Co, Ni and Pb in corn grains and orange fruits were several times higher than normal, and this reduces their suitability for human consumption.     

The content of microelements and iron in soils and plants in the basin of lake Kotokel’ in Western Transbaikalia

The content of microelements (Mn, Zn, Cu, Co, Ni, Cr, Pb, and Cd) and Fe is determined in the soils and plants of the Lake Kotokel’ basin. Their content in the soils is proved not to exceed the regional background and the existing MPC and APC. The content of Cd is revealed to exceed its clarke value for the world soils, which is related to the natural origin of this element. The concentrations of Mn, Co, and Pb are close to their clarke values, and those of Zn, Cu, Ni, and Cr are lower than their clarkes. The studied soils are specified by the maximal amount of the mobile forms of microelements. The profile distribution of the microelements differs depending on the genetic soil type. For Mn, Zn, and Cu, a significant biogenic accumulation is pronounced in the organic soil horizons. The content of microelements in the aboveground phytomass exceeds the maximal permissible levels for Mn, Co, Cr, and Fe. The intensity of the microelements absorption by the plants varies widely, being specified by the high coefficient of the biological adsorption (except for Fe). Mn, Zn, and Cu are accumulated in the plant phytomass the most intensely.     

Increasing the Knowledge of Heavy Metal Contents and Sources in Agricultural Soils of the European Mediterranean Region

This paper contributes to increase the knowledge of the contents and sources of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) to agricultural soils in Castellón province (Spain), a representative area of the European Mediterranean region. The surface horizons of 77 agricultural soils under vegetable crops were sampled and heavy metals were analysed by atomic absorption spectroscopy (AAS) after microwave extraction using the USEPA 3051A method. Mean heavy metal contents were similar to those obtained in other areas of this region. However, heavy metal contents (e.g. Cr, Pb) in some soils were above the maximum limit set in the 86/278/CEE Directive. Multivariate analysis (correlation analysis and principal component analysis – PCA) was performed so as to identify the sources of heavy metals to soils. Co, Fe and Ni were highly correlated amongst them (r?>?0.800; p?<?0.01), whereas Cr and Mn were less correlated with Co, Fe and Ni (r?>?0.500; p?<?0.01). Other relationships among heavy metals (i.e. Cu, Pb and Zn) were also identified, although correlation coefficients were not so high as those among Co, Fe and Ni (r?<?0.500; p?<?0.01). Contents of Co, Fe, Mn and Ni were interpreted to be mainly associated with parent rocks corresponding to the first principal component (PC1). On the other hand, Cd, Cu, Pb and Zn were interpreted to be mainly related to anthropogenic activities and comprised the second (Pb and Zn) and the third (Cd and Cu) principal components (PC2 and PC3, respectively), designated as anthropogenic components. Remarkably, Cr appears to be related in the study area to both the lithogenic and the anthropogenic components. Lithogenic elements were highly correlated with soil properties. Positive relationships with CEC (r?>?0.200; p?<?0.05) and clay (r?>?0.400; p?<?0.01), and negative relationships with carbonates (r?>??0.400; p?<?0.01) and sand (r?>??0.300; p?<?0.01) were observed. Anthropogenic elements were less correlated with soils properties, since these elements are generally more mobile because they form more soluble chemical species associated to anthropogenic sources. Particularly, no correlation was found between Cd and Zn and soil properties. These findings extend results achieved in other parts of the region, highlighting the need to set soil quality standards in order to declare soils affected by anthropogenic pollution, particularly in the case of anthropogenic metals such as Cd, Cu and Pb, and also Cr and Zn in some areas. Further knowledge from other areas in this region would improve the basis for proposing such standards at regional level, which is a priority objective in Europe according to the European Thematic Strategy for Soil Protection.     

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.