北京平谷西部矿集区附近土壤重金属特征

文章以平谷西部金属矿山及矿集区为研究区,采集土壤样品169个,开展区域土壤的重金属污染研究。采用X荧光光谱法、等离子原子发射光谱法等现代测试技术,分析了土壤中重金属(As、Hg、Cd、Cr、Zn、Cu、Pb、Ni)的含量;采用ArcGIS反距离权重插值数学模型和SPSS多元统计方法对土壤重金属空间分布及污染特征进行综合研究;运用潜在生态危害指数法进行生态风险评价。结果表明,研究区域土壤中重金属含量与背景值倍数大小依次是CdPbAsZnCuHgNiCr;重金属危害程度由大到小依次为CdAsPbHgCuNiZnCr;8种重金属潜在生态危害指数RI值在52.11～32 875.38之间。综上所述,研究区域的土壤重金属存在不同程度的风险。     

A washoff model for stormwater pollutants

A washoff rate equation for stormwater pollutants is presented based on linear buildup of pollutant mass in the watershed. The expression was applied to residential and open land areas that have not previously been considered even though these areas are major sources of metals, nutrients, and bacteria in stormwater runoff. The transport coefficient c was determined from the nearly constant portion of the hydrograph at the peak of each runoff event. Values of c (cm(-1)) for seven metals, i.e., Zn, Cu, Cd, Ni, Pb, Hg, and Ag (3.03+/-1.34-6.10+/-2.55 cm(-1)), TSS, BOD(5), total phosphorus (TP), E. coli, and fecal coliform (2.12+/-0.907-7.16+/-2.72 cm(-1)) were estimated using this equation. The washoff rate was developed to reflect mixed land uses based on mass deposition and effective area. The order of transport coefficients for metals is Pb>Ag>Zn>Cu>Ni>Hg>Cd reflecting decreasing particle association. For all parameters this order is TSS>fecal coliform>E. coli>Pb>BOD(5) BOD(5)>Ag>Zn>Cu>Ni>Hg>Cd>TP. The washoff rate and a related pollutant concentration model are expected to be useful for the development of best management practices for stormwater.     

Health risk of Hg, Pb, Cd, Zn, and Cu to the inhabitants around Huludao Zinc Plant in China via consumption of vegetables

Huludao Zinc Plant in Huludao City, China is the largest zinc smelting plant in Asia. Heavy metals have contaminated its neighboring environment seriously. We collected 20 vegetables and the corresponding soil samples from eight sampling plots near Huludao Zinc Plant to investigate health risk of Hg, Pb, Cd, Zn, and Cu to the inhabitants around Huludao Zinc Plant in China via consumption of vegetables. Transfer factor (TF) values of Hg, Pb, Cd, Zn, and Cu from soil to vegetable and the target hazard quotients (THQs) to the possible health risks to local population through the food chain transfer were calculated accordingly. TF values of heavy metals from soil to vegetable decrease in the order of Cd>Zn>Cu>Pb>Hg. These TF values of leaves are higher than other tissues. Daily intakes of Hg, Pb, Cd, Zn, and Cu through the consumption of vegetables are 1.322, 574.3, 301.4, 5263, and 292.5 microg, respectively, for adults, and 1.029, 446.8, 234.5, 4095, and 227.6 microg, respectively, for children around Huludao Zinc Plant. This would lead to potential health risk, especially for children, since Cd or Pb individual THQ is high than 1. The total metal THQs (TTHQs) due to consumption of vegetables for adult and child are 5.79-9.90, 7.6-13.0, respectively. Comparing TTHQs in the sampling plots of different distances to Huludao Zinc Plant, it indicate that the health risks to inhabitants close to Huludao Zinc Plant (<500 m) is the highest, and at >1000 m distance is relatively higher than in 500-1000 m distance. However, the inhabitants who lived in 500-1000 m distance to Huludao Zinc Plant is also experiencing the adverse health risk due to TTHQ being higher than 1.     

Heavy metal distribution in some French forest soils: evidence for atmospheric contamination

This study is one of very few dealing with the distribution and the origin of heavy metals in French soils from a priori non-polluted forest areas. The abundance of heavy metals measured in these soils decreases as follows: Cr>Zn>Pb>Ni>Cu>Co>Cd. Total concentrations of Pb, Cr and Ni in some soils exceed the European thresholds for non-polluted soils and even the French association of normalization critical values for sludge spreading. The lowest heavy metal contents are observed in acid soils while the highest concentrations are in the calcaric cambisol and in the mollic andosol, which is rather scarce as compared with the other French forest soils. With the exception of the podzol, Cr and Ni concentrations increase with depth in all soil profiles. The distribution pattern of Co, Cu, Zn depends on the soil characteristics. In some acid soils, however, Cu and Zn decrease with depth. Pb and Cd are accumulated in the upper soil horizons. Heavy metals accumulate in deep soil horizons in relation to important clay content in the dystric planosol and stagnic luvisol. The concentration of each heavy metal is always controlled by different parameters (soil pH, iron and aluminum oxide content, clay content, organic matter and cation exchange capacity), which are heavy metal specific. This study highlights the metal-trapping character of andosol and calcaric soil, the weak heavy metal retention in acid soils, the leaching and trapping character in leached clayed soils, and the migration of heavy metals in the podzol. Pb and Cr concentrations indicate a significant enrichment in surface horizons from various soils in areas which receive significant acid atmospheric pollution. Particularly, the highest Pb content is observed in a soil located in the N-NE part of France. Lead isotope ratios measured in the cambic podzol and the calcaric cambisol, exhibit the importance of the anthropogenic sources and particularly the influence of global atmospheric inputs from leaded gasoline compared to regional and local industrial emissions. The anthropogenic Pb contribution is estimated to 83, 30 and 11%, respectively, for surface, intermediate and deep horizons of the cambic podzol located in the northern part of France, and to 68% in surface horizon of the calcaric cambisol located in the Alps.     

污水处理厂脱水污泥中重金属的形态分布特征研究

研究了污水处理厂脱水污泥中重金属的形态及总量分布特征,对所采集的活性污泥和消化污泥样品的分析结果表明,镉、铜、铁和锌的主要分布形态为可还原态,在活性污泥中分别占各自总量的48.67%、83.74%、87.21%和64.90%,在消化污泥中则分别占各自总量的37.62%、83.44%、65.99%和61.64%;铬主要以残渣态存在,在活性污泥和消化污泥中分别占其总量的85.83%和67.64%;活性污泥中锰主要以弱酸提取态和可还原态存在,分别占47.16%和44.69%,在消化污泥中则主要以弱酸提取态存在,占61.69%;铅的5种形态分布比较均衡。活性污泥中7种重金属的总量呈现铁>铜>锌>锰>铬>铅>镉的趋势;消化污泥中7种重金属的含量排序则为铁>锰>锌>铜>铬>铅>镉。活性污泥中7种重金属的总量均高于消化污泥。     

Assessment of metal mobility in dredged harbour sediments from Barcelona, Spain

In order to assess heavy metal mobility in dredged harbour sediments, six superficial sediment samples covering a range of pollution levels and environments were collected in Barcelona Harbour. Samples were characterised in terms of major compounds (Al, Ca, Fe, Mn, Si, Ti, Mg, K and Na); total C, N and S contents; organic matter; and water content. Pseudo-total trace metal contents were assessed after aqua regia digestion (ISO 11466:1995). The modified BCR three-step sequential extraction procedure (BCR-SEP) was applied, and both major compounds (Al, Ca, Fe and Mn) and trace metals (Cd, Cr, Cu, Ni, Pb and Zn) were determined in the different extracts. Both the pseudo-total digestion method and the BCR-SEP were validated using two sediment certified materials from lakes (BCR CRM 701 and BCR CRM 601). The highest metal concentrations were observed in one of the sampling points which receives an urban discharge. The observed mobility order (percentage of metal extracted in the first step) of the six trace metals studied was Cd>Zn>Pb>Cu>Ni>Cr. The good agreement observed with the results obtained as the sum of the four steps (extractable+residue) and the pseudo-total content shows that laboratory working conditions were under control.     

Atmospheric accessions of heavy metals to some New Zealand pastoral soils

Total heavy metal deposition was monitored at seven rural sites across New Zealand to determine the rate of atmospheric deposition of heavy metals to soils and to evaluate any regional and temporal variations in metal deposition. Heavy metal deposition was collected monthly in Warren Spring Laboratory type inverted frisbees. The rate of heavy metal deposition followed the order Zn>Cu>Cr>Pb>Ni>Cd. There were no obvious trends with regards to either seasonal or spatial deposition for any of the heavy metals measured. With the exception of Zn, heavy metal deposition in New Zealand was generally lower than rates measured in other countries. This reflects the general lack of high temperature industrial processes from urban-based industrial processes that are an important source of heavy metal aerosols in other industrialised regions worldwide. The inverted frisbee technique used provides a reliable indication of the magnitude of deposition of heavy metals from the atmosphere at a reasonable cost and with manageable logistical effort for a national survey.     

Geographical variation and partition of metals in tissues of Octopus vulgaris along the Portuguese coast

Zinc, Cu, Cd, Pb and Hg were determined in mantle, arm and digestive gland of 59 individuals of Octopus vulgaris captured at six sites along the Portuguese coast. Metal concentrations in tissues did not vary significantly (P<0.05) with size/weight, sex or sexual stage. The abundance of metals in each analysed tissue was: Zn>Cu>Cd>Pb>Hg. Concentrations in the digestive gland reached one (Pb, Hg) and two (Zn, Cu, Cd) orders of magnitude higher than those found in arm and mantle, which indicates that the digestive gland contains the major storage sites for these elements, acting as a detoxification organ. However, concentrations in the digestive gland showed contrasting geographic patterns: Zn, Pb, Cu and Hg were higher in the Southern stations, while Cd levels increased drastically in Northern stations. This increase is in line with the contrasting Cd distribution in coastal waters. The lack of relations between metal concentration in tissues and biological parameters facilitates the recognition of those spatial patterns. The geographical contrast of Cd is extended to the accumulation in mantle and arm. A possible explanation for these enhanced values is that threshold level for Cd accumulation in digestive gland was attained and detoxification processes eventually modified.     

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study

Contents of total and extractable heavy metals, carbonates, MnO and Fe₂O₃, organic matter, and matrix components such as SiO₂, Al₂O₃, CaO, Na₂O, MgO, TiO₂, K₂O and P₂O₅ are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were taken along the beds of the river course. Total metal concentrations were obtained after microwave-assisted digestion whilst extractable metal contents were obtained following a three-stage sequential extraction scheme (i.e. soluble, reducible and oxidisable fractions). Loading plots of heavy metals bound to carbonates, Fe–Mn oxides, organic matter and aluminosilicates allowed determination of binding behaviour. Correlations found indicate that Pb and Cu are mainly discharged from urban wastes, whereas Cr and Ni are from electroplating and galvanizing industries. The occurrence of diffuse pollution sources along the river can account for the binding behaviour of Cd. Metal mobility decreased in the order: Cd>Pb>Cu>Ni>Cr. Despite total contents indicating moderate-to-high heavy metal pollution in this river, metals are mostly distributed in the residual fraction, hence showing a low risk of mobility.     

皖北某矿区中层地下水微量元素健康风险评价

为研究皖北某矿区松散层中部地下水中微量元素含量特征及其对人体产生的潜在健康危害风险,对该矿区的水质进行了监测分析,并采用中国环保部《污染场地健康风险评价导则》(HJ25.3-2014)推荐的健康风险评价模型分析了该矿区中层地下水中微量元素经饮水途径所引起的健康风险。结果表明:所监测的微量元素浓度为Zn>Ni>Cu>Cd>Cr,其中,Cd、Cr、Cu和Zn浓度都在《地下水质量标准》(GB/T 14848-93)中Ⅲ类水质标准的规定范围内,仅Ni有一个水样超过相应的标准限值,对该矿区的中层地下水水质无明显的影响;5种微量元素中仅Cr存在潜在致癌风险,风险均值为1.55×10^-6,超过了该模型推荐的评价标准(10^-6),但是与国内已报道的其他地区的致癌风险度无明显差异;5种微量元素虽有非致癌风险,但危害商远小于1,不会对人体产生明显的非致癌健康危害。     

Patterns of metal bioaccumulation in two filter-feeding macroinvertebrates: Exposure distribution, inter-species differences and variability across developmental stages

This study focused on the metal bioaccumulation of two aquatic insects (Ephoron virgo and Hydropsyche spp.) in order to evaluate the spatial distribution of metals, the interspecific differences between both filter-feeders and the bioaccumulation dynamics during E. virgo development stages. Hg, Cd, Ni, Cr, As, Pb, Cu, Ti, Zn and Mn were quantified in insects and in suspended particulate matter (SPM) sampled downstream and upstream of a chemical plant, where more than 300,000 t of polluted sediments are deposited. Hg concentrations were one order of magnitude higher downstream of the sediment dump, which showed that the Hg pollution originated in the chemical plant. Cd, Ni, Cr, Pb, Ti, Zn and Mn in invertebrates revealed that metal pollution was present upstream in other parts of the river. Interspecific differences were observed for all metals but Mn; significantly higher concentrations were observed in E. virgo over Hydropsyche exocellata, except for Cd, which showed 10-fold higher values. Hg and Cd increased until E. virgo nymphs reached 11 mm and decreased afterwards in late instars when nymphs were about to emerge. Cr, Pb, Ti and Mn decreased along early instars followed by a steady state in late instars. Similar values were obtained for Cu, As and Zn along all instars. Sexual differences between males and females of E. virgo were observed for Cd, Cu and Mn. Hg and Cd persistence was strong across developmental stages since high concentrations were found in eggs and emerging adults. Because the behavior of different metals varied for the two species and during the developmental stages of E. virgo, care should be taken in the interpretation of insect metal concentrations when analyzing the food chain transfer of metals in river ecosystems.     

Health risks of heavy metals to the general public in Tianjin, China via consumption of vegetables and fish

Consumption of vegetables and fish contaminated with the heavy metals Cu, Zn, Pb, Cd, Hg, and Cr is the most likely route for human exposure in Tianjin, China. Health risks associated with these heavy metals were assessed based on the target hazard quotients (THQs), which can be derived from concentrations of heavy metals in vegetables and fish consumed in four districts (Dong Li, Xi Qing, Jin Nan, and Bei Chen) and the urban area of Tianjin, China. Individual metal THQ (<1) values indicate the relative absence of health risks associated with intake of a single heavy metal through consumption of either contaminated vegetables or fish only. However, consumption of both vegetables and fish would lead to potential health risks especially for children, since individual THQs for vegetables and fish would sum up to almost 1. If individual THQs resulting from crops consumption are considered, the health risks would be greater for children since the THQ values will always be >1. Risk contribution from Cr is minimal compared to the other elements. Hg is the major risk contributor for children in Bei Chen since the THQ contribution amounts to about 45% of the total THQ values due to vegetables and fish consumption. The health risk to adults in Ding Li is ascribed mainly to the intake of Cd by vegetables and fish consumption, which contributes a substantial fraction to the total THQ (about 51%).     

Health risk assessment of heavy metal exposure to street dust in the zinc smelting district, Northeast of China

Heavy metal contamination in the street dust due to metal smelting in the industrial district of Huludao city was investigated. Spatial distribution of Hg, Pb, Cd, Zn and Cu in the street dust was elucidated. Meanwhile, noncancer effect and cancer effect of children and adults due to exposure to the street dust were estimated. The maximum Hg, Pb, Cd, Zn and Cu contents in the street dust are 5.212, 3903, 726.2, 79,869, and 1532 mg kg^− 1, and respectively 141, 181, 6724, 1257 and 77.4 times as high as the background values in soil. The trends for Hg, Pb, Cd, Zn and Cu are similar with higher concentrations trending Huludao zinc plant (HZP). The exponential equation fits quite well for the variations of Pb, Cd, Zn and Cu contents with distance from the pollution sources, but not for Hg. The biggest contribution to street dust is atmospheric deposition due to metal smelting, but traffic density makes slight contribution to heavy metal contamination. According to the calculation on Hazard Index (HI), in the case of noncancer effect, the ingestion of dust particles of children and adults in Huludao city appears to be the route of exposure to street dust that results in a higher risk for heavy metals, followed by dermal contact. The inhalation of resuspended particles through the mouth and nose is almost negligible. The inhalation of Hg vapour as the fourth exposure pathway to street dust is accounting for the main exposure. Children are experiencing the potential health risk due to HI for Pb larger than safe level (1) and Cd close to 1. Besides, cancer risk of Cd due to inhalation exposure is low.     

Trace metal concentrations are higher in cartilage than in bones of scaup and pochard wintering in Poland

Bones and cartilage of two species of diving ducks: the scaup Aythya marila (n=24) and the pochard A. ferina (n=24) were studied. Scaup is protected in Poland where it spends only the winter, while pochard is a game bird, abundant and breeding in Poland. In winter, the two species form large flocks off the southern coast of the Baltic, particularly in the Szczecin Lagoon where they were collected for this study. The bones and cartilage (trachea) were assayed for concentrations (dry weight-based) of three essential metals: iron (Fe), copper (Cu), and zinc (Zn); concentrations of the two toxic metals: lead (Pb) and cadmium (Cd) were assayed as well. These hard tissues of the two species showed the following order of metal concentrations Zn>Fe>Pb>Cu>Cd. In scaup and pochard bones, the respective geometric mean concentrations of Zn, Fe, Pb, Cu, and Cd were 94.4 and 102.0; 20.2 and 24.7; 6.2 and 9.6; 0.19 and 0.26; 0.114 and 0.162 mg/kg. The levels of all the metals in cartilage (Zn 149.1 and 165.8; Fe 58.4 and 116.3; Pb 10.6 and 14.9; Cu 1.41 and 3.31; Cd 0.144 and 0.175 mg/kg, respectively) were higher than in the bones of A. marila and A. ferina. However, statistically significant differences were found in respect to the essential metals only (Zn, Fe, Cu). The inter-species comparisons showed the two species to differ in their cartilage concentrations of Fe, Cu, Zn, and Cd and in their bone concentrations of Pb and Cd. In each case, the pochard exhibited higher concentrations of metals. This study showed distinct differences between trace element accumulation by two heavily mineralised avian body parts: leg bones (tarsometatarsus) and cartilage (trachea). The results are in agreement with data reported by other workers who analysed trace metals in cartilaginous and bone components of the femoral head in homoiotherm vertebrates, including humans. Therefore it is important that intra- and inter-species comparisons of hard biological components be based on corresponding body parts, and that relevant biochemical and ecotoxicological research be pursued.     

Heavy metal behaviour during the activated sludge process I. Extent of soluble and insoluble metal removal

The extent of removal of Ag, Bi, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Tl and Zn and their distribution between the soluble and insoluble phases in the influent, and effluent of the activated sludge process has been studied using a pilot-scale plant operated at sludge ages of 3, 6, 9 and 12 days. Molybdenum, Tl, Co, Mn and Ni were >50% soluble in the influent settled sewage. The mean removals of the former two metals were <3% and the latter three were 35 and 50%. Silver, Bi, Cd, Cr, Cu, Pb and Zn were all <35% soluble in the influent and had substantial removals of >75%. Solubilities were greater in the effluent than the influent with the exception of Mn. The observed overall removals of Ag, Bi, Co, Ni, Pb, Tl and Zn were almost entirely due to insoluble metal removal; Cd, Cr and Cu removals had a significant contribution from soluble metal removal. Overall Mn removal appeared to be solely due to soluble metal removal.     

Metal contamination of soils and crops affected by the Chenzhou lead/zinc mine spill (Hunan, China)

In 1985, the collapse of the tailing dam in Chenzhou lead/zinc mine (Hunan, southern China) led to the spread of mining waste spills on the farmland along the Dong River. After the accident, an urgent soil cleaning up was carried out in some places. Seventeen years later, cereal (rice, maize, and sorghum), pulses (soybean, Adzuki bean, mung bean and peanut), vegetables (ipomoea, capsicum, taro and string bean) and the rooted soils were sampled at four sites: (1) the mining area (SZY), (2) the area still covered with the mining tailing spills (GYB), (3) the cleaned area from mining tailing spills (JTC), and (4) a background site (REF). Metal concentrations in the crops and soils were analyzed to evaluate the long-term effects of the spilled waste on the soil and the potential human exposure through food chains. The results showed that the physical-chemical properties of the soils obviously changed due to the different farming styles used by each individual farmer. Leaching effects and plant extraction of metals from some soils were quite weak. Certain soils were still heavily polluted with As, Cd, Zn, Pb and Cu. The contamination levels were in the order of GYB>SZY>JTC showing that the clean-up treatment was effective. The maximum allowable concentration (MAC) levels for Chinese agricultural soils were still highly exceeded, particularly for As and Cd (followed by Zn, Pb and Cu), with mean concentrations of 709 and 7.6 mg kg(-1), respectively. These concentrations exceed the MAC levels by 24 times for As and 13 times for Cd at GYB. Generally, the edible leaves or stems of crops were more heavily contaminated than seeds or fruits. Ipomoea was the most severely contaminated crop. The concentrations of Cd and Pb were 3.30 and 76.9 mg kg(-1) in ipomoea leaves at GYB, which exceeded the maximum permit levels (0.5 mg kg(-1) for Cd and 9 mg kg(-1) for Pb) by 6.6 and 8.5 times, respectively. Taro (+skin) could accumulate high concentrations of Zn and Cd in the edible stem, and rice and capsicum had high Cd concentration in the edible parts. However, the toxic element concentrations in maize, sorghum, Adzuki bean, soybean and mung bean remained lower than the threshold levels. The bio-accumulation factors (BAFs) of crops were in the order: Cd>Zn>Cu>Pb>As. BAF was typically lower in the edible seeds or fruits than in stems and leaves. The accumulation effect strongly depends on the crop's physiological properties, the mobility, of the metals, and the availability of metals in soils but not entirely on the total element concentrations in the soils. Even so, the estimated daily intake amount of Cu, Zn, Cd, and Pb from the crops grown in the affected three sites and arsenic at SZY and GYB exceeded the RDA (Recommended dietary allowance) levels. Subsequently, the crops grown in Chenzhou Pb/Zn mine waste affected area might have a hazardous effect on the consumer's health. This area still needs effective measures to cure the As, Cd, Pb, Zn and Cu contamination.     

Heavy metals in urban soils: a case study from the city of Palermo (Sicily), Italy

Concentrations of V, Mn, Cd, Zn, Ni, Cr, Co, Cu, Pb, Hg and Sb were measured on 70 topsoil samples collected from green areas and parks in the city of Palermo (Sicily) in order to: (1) assess the distribution of these heavy metals in the urban environment; (2) discriminate natural and anthropic contributions; and (3) identify possible sources of pollution. Mineralogy, physico-chemical parameters, and major element contents of the topsoils were determined to highlight the influence of 'natural' features on the heavy metal concentrations and their distribution. Medians of Pb, Zn, Cu and Hg concentrations of the investigated urban soils are 202, 138, 63 and 0.68 mgkg(-1), respectively. These values are higher, in some case by different orders of size, than those of unpolluted soils in Sicily that average 44, 122, 34 and 0.07 mg kg(-1). An ensemble of basic and multivariate statistical analyses (cluster analysis and principal component analysis) was performed to reduce the multidimensional space of variables and samples, thus defining two sets of heavy metals as tracers of natural and anthropic influences. Results demonstrate that Pb, Zn, Cu, Sb and Hg can be inferred to be tracers of anthropic pollution, whereas Mn, Ni, Co, Cr, V and Cd were interpreted to be mainly inherited from parent materials. Maps of pollutant distribution were constructed for the whole urban area pointing to vehicle traffic as the main source of diffuse pollution and also showing the contribution of point sources of pollution to urban topsoils.     

Assessing risk to human health from tropical leafy vegetables grown on contaminated urban soils

Fifteen tropical leafy vegetable types were sampled from farmers' gardens situated on nine contaminated sites used to grow vegetables for commercial or subsistence consumption in and around Kampala City, Uganda. Trace metal concentrations in soils were highly variable and originated from irrigation with wastewater, effluent discharge from industry and dumping of solid waste. Metal concentrations in the edible shoots of vegetables also differed greatly between, and within, sites. Gynandropsis gynandra consistently accumulated the highest Cd, Pb and Cu concentrations, while Amaranthus dubius accumulated the highest Zn concentration. Cadmium uptake from soils with contrasting sources and severity of contamination was consistently lowest in Cucurbita maxima and Vigna unguiculata, suggesting these species were most able to restrict Cd uptake from contaminated soil. Concentrations of Pb and Cr were consistently greater in unwashed, than in washed, vegetables, in marked contrast to Cd, Ni and Zn. The risk to human health, expressed as a ‘hazard quotient’ (HQ_M), was generally greatest for Cd, followed successively by Pb, Zn, Ni and Cu. Nevertheless, it was apparent that urban cultivation of leafy vegetables could be safely pursued on most sites, subject to site-specific assessment of soil metal burden, judicious choice of vegetable types and adoption of washing in clean water prior to cooking.     

Heavy metals in wild rice from northern Wisconsin

Wild rice grain samples from various parts of the world have been found to have elevated concentrations of heavy metals, raising concern for potential effects on human health. It was hypothesized that wild rice from north-central Wisconsin could potentially have elevated concentrations of some heavy metals because of possible exposure to these elements from the atmosphere or from water and sediments. In addition, no studies of heavy metals in wild rice from Wisconsin had been performed, and a baseline study was needed for future comparisons. Wild rice plants were collected from four areas in Bayfield, Forest, Langlade, Oneida, Sawyer and Wood Counties in September, 1997 and 1998 and divided into four plant parts for elemental analyses: roots, stems, leaves and seeds. A total of 194 samples from 51 plants were analyzed across the localities, with an average of 49 samples per part depending on the element. Samples were cleaned of soil, wet digested, and analyzed by ICP for Ag, As, Cd, Cr, Cu, Hg, Mg, Pb, Se and Zn. Roots contained the highest concentrations of Ag, As, Cd, Cr, Hg, Pb, and Se. Copper was highest in both roots and seeds, while Zn was highest just in seeds. Magnesium was highest in leaves. Seed baseline ranges for the 10 elements were established using the 95% confidence intervals of the medians. Wild rice plants from northern Wisconsin had normal levels of the nutritional elements Cu, Mg and Zn in the seeds. Silver, Cd, Hg, Cr, and Se were very low in concentration or within normal limits for food plants. Arsenic and Pb, however, were elevated and could pose a problem for human health. The pathway for As, Hg and Pb to the plants could be atmospheric.     

Seasonal and time variability of heavy metal content and of its chemical forms in sewage sludges from different wastewater treatment plants

Sewage sludges obtained from seven wastewater treatment plants from the province of Salamanca, Spain, were periodically sampled to determine seasonal and time variation of their elemental composition over 2000 to 2002. The aim of this paper was to provide additional insight to evaluate the potential environmental impact following soil incorporation of these materials as amendments. Aqua regia extractable metals (pseudo total content) of Cd, Cr, Cu, Ni, Pb and Zn were determined and furthermore, the main chemical forms of metals within the sludge were evaluated using a five-step fractionation procedure. All the studied sludges displayed high fertility properties due to their richness of OC, P and K. Total mean concentrations of Cd, Cr, Cu, Ni, Pb and Zn in the sludges were within the regulation of the Spanish legislation. Using an multifactor analysis of variance, significant differences between Cr, Cu, Ni, Pb and Zn pseudo total contents (p<0.01) of sludges at different sites were found while the Cd content was statistically similar. Also significant differences were found between these pseudo total contents of heavy metals in samples collected along the time after three years (0.001相似文献