Heavy metal contamination in vegetables grown around peri-urban and urban-industrial clusters in Ghaziabad,India

Heavy metal contamination of agricultural soils resulting from rapid industrialization and urbanization is of great concern because of potential health risk due to dietary intake of contaminated vegetables. The present study aims to evaluate the status of heavy metals contamination of agricultural soils and food crops around an urban-industrial region in India. Transfer factor values of Cu, Cr, Pb, Cd, Zn, and Ni from soil to vegetable was estimated. The mean heavy metal concentrations (mg/kg) in agricultural soils (Cu: 17.8, Cr: 27.3, Pb: 29.8, Cd: 0.43, Zn: 87, Mn: 306.6, Fe: 16984, and Ni: 53.8) were within allowable concentrations for Indian agricultural soil. The concentrations of Pb, Cd, Zn, and Ni in crops/vegetables exceeded the World Health Organization/Food and Agriculture Organization safe limits. Relative orders of transfer of metals from soil to edible parts of the crops/vegetables were Cd > Pb > Ni > Zn > Cu > Cr. The enrichment factors of heavy metals in soil indicated minor to moderately severe enrichment for Pb, Cd, and Ni; minor to moderate enrichment for Zn; no enrichment to minor enrichment for Mn; and no enrichment to moderate enrichment for Cu at different sites. Ecological risk index of soil showed considerable contamination in one of the wastewater irrigated sites.     

Sources and Ecological Risk Assessment of Heavy Metal(loid)s in Agricultural Soils of Huzhou,China

To identify sources of heavy metal(loid) (HM) contamination in agricultural soils of Huzhou, surface soil samples were sampled from 89 different agricultural regions in 2012. Concentrations of heavy metal(loid)s, along with pH, total phosphorus (TP), total nitrogen (TN), and soil organic matter (SOM), were determined. Ecological risk was then assessed using a modified Hakanson ecological risk index, and the sources of contamination were determined using principal component analysis (PCA). Mean concentrations of heavy metal(loid)s were 10.26, 23.21, 83.75, 22.81, 0.25, 61.86, 33.03, and 0.15 mg kg^?1 for As, Cu, Zn, Ni, Cd, Cr, Pb, and Hg, respectively. Cu, Zn, Ni, Cr, Cd, Hg, and Pb were correlated positively with TP and there were obvious positive correlations among Cu, Zn, Ni, Cr, and Cd. Risk index (RI) values varied from 39 to 1246 with a mean value of 137. Enrichment of Pb, Zn, Cu, and especially Cd can be attributed to excessive use of nitrogen and phosphorus fertilizers containing heavy metals, as well to surface irrigation and natural soil formation. While the ecological risk of most agricultural soils in Huzhou is low, it is recommended that the use of phosphate and nitrogen fertilizers be restricted and production technology be improved to reduce the heavy metal(loid) concentrations. Results suggest that the Chinese environmental quality standard for soil should be revised to better address heavy metal(loid) contamination.     

华南地区典型燃煤电厂周边土壤重金属分布、风险评估及来源分析

为了解华南地区典型燃煤电厂周边表层土壤重金属空间分布特征,对韶关市燃煤电厂周边20处农田表层土壤中7种重金属(镍(Ni)、铜(Cu)、锌(Zn)、镉(Cd)、铅(Pb)、铬(Cr)及砷(As))的总量进行检测,并分析了其相应的空间分布规律,同时评估了周边土壤重金属的生态风险并分析其来源。结果表明:该燃煤电厂周边土壤中重金属Ni、Cu、Zn、Cd、Pb、Cr及As的平均含量分别是17.79、19.59、159.08、3.14、111.01、96.61 mg/kg和21.48 mg/kg,Cd、Pb污染情况突出,重金属Zn、Cd、Pb、Cr的分布与盛行风向密切相关。综合污染指数法表明,Cd、Pb及Zn处于重污染状态;潜在生态风险指数法表明,Cd处于严重潜在生态风险状态;地累积指数法表明,Ni、Cu整体处于无污染状态,Cd整体处于高污染状态。多种统计方法表明,Zn、Cd、Pb及Cr受燃煤电厂影响明显,Cu、As的来源不仅受燃煤电厂等工业的影响,还与该地区农业灌溉用水密切相关,Ni的分布最为均匀,受自然因素影响明显。     

新疆焉耆盆地辣椒地土壤重金属污染及生态风险预警

从新疆加工辣椒主产地(焉耆盆地)采集105个辣椒地典型土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量。采用污染负荷指数(Pollution load index,PLI)、潜在生态风险指数(Potential ecological risk index,RI)和生态风险预警指数(Ecological risk warning index,I_(ER))对辣椒地土壤重金属污染及生态风险进行评价。结果表明:(1)焉耆盆地辣椒地土壤Cd、Cr、Ni、Pb和Zn含量的平均值分别超出新疆灌耕土背景值的1.65、1.40、1.32、3.21、6.42倍。辣椒地土壤Pb和Zn呈现重度污染,Cd、Cr和Ni轻度污染,As、Mn和Cu无污染。(2)土壤PLI平均值为1.40,呈现轻度污染。各重金属元素单项生态风险指数从大到小依次为:Cd、Ni、As、Cu、Pb、Cr、Zn。土壤RI平均值为18.40,属于轻微生态风险态势,IER平均值为-4.78,属于无警态势;博湖县辣椒地污染水平、潜在生态风险程度与生态风险预警等级最高,焉耆县污染水平、潜在生态风险程度与生态风险预警等级最低。(3)辣椒地土壤As、Cd、Pb与Zn主要受到人类活动的影响,Cr、Cu、Mn和Ni主要受到土壤地球化学作用的控制。Cd是焉耆盆地辣椒地生态风险等级最高的重金属元素,研究区农业生产过程中要防范Cd的污染风险。     

Analysis of Spatial Variations and Sources of Heavy Metals in Farmland Soils of Beijing Suburbs

To understand the effect of intense human activities in suburbs on environmental quality, we obtained 758 measurements of the heavy metals in certain farmland soils of the Beijing suburbs. Multivariate statistical analysis and geostatistical analysis were used to conduct a basic analysis of the heavy metal concentrations, the distribution characteristics and the sources of pollution of the farmland soils in these suburbs. The results showed the presence of eight heavy metals in the agricultural soils at levels exceeding the background values for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. In particular, all the measured Cr concentrations exceeded the background value, while As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were present at 1.13, 1.68, 1.95, 1.43, 1.63, 0.79, 0.92 and 1.36 times their background values, respectively. The results of correlation, factor and spatial structure analyses showed that Cd, Cu, Pb and Zn were strongly homologous, whereas Cr and Hg showed a degree of heterogeneity. The analysis further indicated that in addition to natural factors, Cd, Cu, Pb and Zn in the soil were mainly associated with distribution from road traffic and land use status. Different agricultural production measures in the various areas were also important factors that affected the spatial distribution of the soil Cr concentration. The major sources of Hg pollution were landfills for industrial waste and urban domestic garbage, while the spatial distribution of As was more likely to be a result of composite pollution. The regional distribution of the heavy metals indicated that except for Cr and Hg, the high heavy metal levels occurred in districts and counties with higher organic matter concentrations, such as the northwestern and southeastern suburbs of Beijing. There was no significant Ni pollution in the agricultural soils of the Beijing suburbs.     

A human health risk assessment of heavy metals in agricultural soils of Yanqi Basin,Silk Road Economic Belt,China

A total of 195 farmland soil samples were collected in Yanqi Basin, Xinjiang, northwest China, and the concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were analyzed for their concentrations and pollution levels using the Nemerow comprehensive index. The health risk assessment model introduced by USEPA was utilized to evaluate the human health risks of heavy metals. Results indicated that the average concentrations of these seven metals were lower than the allowed soil environmental quality standards of China, while the average concentrations of Cd, Cr, Ni, Pb and Zn exceeded the background values of irrigation soils in Xinjiang. The average contamination factor (CF) for Pb indicated the heavy pollution, whereas the CF for Cd, Zn, Ni, Cu and Cr indicated the moderate pollution. The average PLI of heavy metals indicated the low pollution. The non-carcinogenic hazard index were below the threshold values, and the total carcinogenic risks due to As and Cr were within the acceptable range for both children and adults. As and Pb were the main non-carcinogenic factors, while As was the main carcinogenic factor in the study area. Special attentions should be paid to these priority control metals in order to target the lowest threats to human health.     

浙江油茶产地土壤和果实金属元素含量特征

为探讨油茶(Camellia oleifera)产地土壤和油茶果实中金属元素分布和富集特征,在油茶果实成熟期,对浙江5个油茶产地土壤及油茶果实中金属元素进行污染分析和富集能力评价。结果表明,浙江油茶产地土壤中Pb、Cr、Cd、As、Hg、Ni、Cu和Zn含量低于农用地土壤污染风险筛选值,综合污染等级为安全。个别产区常山县土壤中As、Ni、Cu和江山县土壤中Pb、Cr、Fe含量显著高于其他产地;常山和建德土壤中Cd单因子污染指数分别为0.93和0.81,处于污染警戒线。Cr、Ni、Cu、Zn主要分布在油茶籽中,Hg主要分布在壳中,Pb、Cd、As、Fe和Mn主要分布在青皮中。油茶籽中Cu、Fe、Mn的富集系数大于0.4,吸收能力强,Ni、Zn的富集系数小于0.4,具有一定吸收能力,Pb、Cr、Cd、As和Hg的富集系数小于0.1,吸收能力低;壳中Cu、Mn的富集系数大于0.4,吸收能力强,Fe的富集系数小于0.4,具有一定吸收能力,Pb、Cr、Cd、As、Hg、Ni、Zn的富集系数小于0.1,吸收能力低;青皮中Cu、Fe、Mn的富集系数大于0.4,吸收能力强,Pb、Cr、Cd、As、Hg、Ni、Zn的富集系数小于0.1,吸收能力低。浙江油茶主产区土壤质量安全,适合油茶种植。油茶果实对Cu、Fe、Mn有一定富集能力,对Pb、Cr、Cd、As和Hg无富集能力。     

贵州兴仁煤矿区农田土壤重金属化学形态及风险评估

为了解煤矿区周边农田土壤重金属污染状况,采集了贵州省兴仁县某典型煤矿区农田土壤样品64份,测定了土样中重金属(As、Cr、Pb、Zn、Cd、Hg、Cu、Ni)总量及各形态含量,采用单因子指数法、潜在生态风险指数法(Hkanson法)和风险评估编码法(RAC)对研究区主要土壤利用类型(水稻土、薏米地、植烟土和菜园土)中重金属进行潜在生态风险评估和环境风险评价.结果表明： 不同利用类型土壤中重金属含量除Zn外,其他元素均明显超过贵州省背景值.单因子指数法评价结果表明,As、Pb、Hg和Cu污染较为严重,均属重度污染.形态分析表明,土壤中重金属形态构成差异明显,酸可提取态As、酸可提取态Cd所占比例较高;Cr、Zn、Cu、Ni主要以残渣态为主;Pb主要以可还原态和残渣态为主;而Hg的酸可提取态、可还原态、可氧化态均占有相当比例,三者之和大于55%.重金属可利用度大小顺序为:As(63.6%)>Hg(57.3%)>Cd(56.4%)>Pb(52.5%)>Cu(45.7%)>Zn(32.8%)>Ni(26.2%)>Cr(13.2%).潜在生态风险指数表明,各类型土壤潜在生态风险(RI)〖JP2〗为:菜园土(505.19)>薏米地(486.06)>植烟土(475.33)>水稻土(446.86),均处于较高风险.风险评估编码法结果显示,As在水稻土、薏米地及植烟土中均处于高风险,在菜园土中处于中等风险;Cd、Hg均处于中等风险,Cr、Pb、Zn、Cu和Ni均处于低风险.因此,对该区域农田土壤进行管控时应重点考虑As、Cd和Hg污染.     

佛山城市典型森林群落土壤重金属分布、流通及枯落物富集特征

富集重金属的枯落物分解可能提高重金属暴露率,增加人体接触健康风险。为了解南方城市土壤重金属在森林生态系统中的分布及流转情况,通过调查研究了佛山市8个典型森林群落土壤及枯落物重金属含量,分析了各森林群落枯落物对不同重金属的富集效应及重金属随枯落物回归土壤流通量。结果表明：1）城市森林各土壤重金属含量在不同典型群落间差异显著（P<0.05）,差异最大为Pb、Cr、Zn,As、Cu、Ni次之,Hg、Cd最小;土层深度（0-20,20-40,40-60 cm）对重金属含量影响显著（P<0.05）,差异最大为Cd、Hg,其次为As、Cu,最小为Zn、Ni、Pb、Cr。整体上,Cd、Hg、As、Pb、Zn在0-20 cm最高,表层富集特征明显,Cr和Ni在40-60 cm最高。2）8个森林群落中阴香-白楸-醉香含笑群落（CMMC）枯落物对8种重金属的综合富集系数（TBCF,66.76）最高,其中以Cd的富集效果最突出,富集系数为44.45,且对Pb、Cu、Zn也相对富集;最低的为黧蒴锥-香椿-樟树群落（CTCC）,综合富集系数（TBCF）为8.09,仅对Cd、Cr、Cu相对富集,对其余重金属富集效应不明显。3）相关分析显示,群落重金属枯落物流通量与0-60 cm土壤重金属平均含量（Cr和Ni除外）无显著相关性。本研究对城市森林建设管理及筛选重金属富集植物及群落具有较强理论及实践意义。     

Assessment of Heavy Metal Pollution in Urban Agricultural Soils of Jilin City,China

Due to rapid industrialization and urbanization during the last two decades, contamination of urban agricultural soils by heavy metals is on an increase all over China. In this study, fifty soil samples were collected from urban vegetable fields in a chemical industrial area and non chemical industrial area in Jilin City to investigate the heavy metal pollution level. The mean Pb, Cr, Cu, Ni, Zn, and Cd contents (30.84, 65.65, 26.41, 23.07, 135.14, and 0.1434 mg kg^?1 dry weight, respectively) in the urban vegetable soils were higher than their corresponding natural background values. The principal component analysis (PCA) was performed to identify the possible sources of metal contamination in the study area. The results indicated that Cu and Zn were mainly from industrial activities, while Pb and Cd were derived from traffic activities and agricultural activities, and Cr and Ni tended to be from parent material. The distribution of comprehensive pollution index values showed that Pb, Cr, Cu, Ni, Zn, and Cd concentrations in most of the agricultural fields did not exceed the baseline values affecting the safety of agricultural production and human health according to the soil environmental quality standard of China, indicating an insignificant contamination of these metals in Jilin City.     

Contamination features and health risk of heavy metals in suburban vegetable soils,Yanbian, Northeast China

In recent years, heavy metal contamination in suburban vegetable soils calls for significant concerns due to the rapid urbanization and industrialization. In present study, 110 suburban vegetable soil samples from Yanbian, Northeast China, were collected. Concentration characteristics, pollution level, health risk, and source identification were evaluated by using different quantitative indices. Concentrations of Pb, Cr, Cu, Ni, Zn, Cd, and As in suburban soils were measured. Mean concentrations of Pb, Cr, Cu, Ni, Zn Cd, and As were 34.9 ± 10.5, 73.5 ± 44.4, 29.6 ± 19.4, 23.4 ± 12.0, 88.5 ± 26.7, 0.16 ± 0.16, and 9.24 ± 3.79 mg/kg, which were showed significantly higher than corresponding background values of Jilin province, respectively. The soils were moderately heavy polluted by Cu and Cd based on the results of geo-accumulated index and pollution indices. The pollution load index indicated that almost all of the study area were middle or heavy polluted, especially in Antu County and Helong City. Children in Yanbian may pose non-carcinogenic and carcinogenic risks with the major exposure pathway of ingestion. Principle component analysis results suggested that Pb, Cu, Zn, and Cd were mainly associated with agricultural activities, Ni and Cr were defined as combined source (lithogenic and anthropogenic), and As was tended to be from excessive application of pesticides and industrial activities.     

Source apportionment and health risk quantification for heavy metal sources in soils near aluminum-plastic manufacturing facilities in northeast China

Abstract

Identifying the source effect on heavy metals to human health risk is essential for devising and implementing restoration policies for polluted soils. For this purpose, eight heavy metals (As, Cd, Hg, Cr, Cu, Ni, Pb, and Zn) in soil profile samples (0–10, 10–20, 20–30, and 30–40?cm) collected in the area around aluminum-plastic manufacturing facilities (APMF) were determined. An absolute principal component score multiple linear regression (APCS-MLR) model supported by a health risk assessment (HRA) model was developed to determine the source apportionment of soil heavy metals and contribution rate of pollution sources to human health risk. Results showed significant accumulations of eight metals in the topsoil (0–20?cm), parent material, transportation, APMF, and agricultural practices were the four major contributing sources for heavy metals in soils, with average contribution percentages of 21.69%, 24.99%, 29.60%, and 14.25%, respectively. Carcinogenic risk factors for adults (1.23E-04) and children (1.32E-04) were found to be above the acceptable level (1E-06 to 1E-04). The health risk quantification results indicated that parent material, APMF, transportation, agricultural practices, and unidentified factors accounted for 55.76%, 14.48%, 12.09%, 10.13%, and 7.54% of the carcinogenic risk for children and adults. The adverse impacts of Cd, Zn, and Pb accumulations in soil coming from APMF activities were significant and need to receive more attention.     

Investigation of the Effects of Phosphate Fertilizer Application on the Heavy Metal Content in Agricultural Soils with Different Cultivation Patterns

The use of phosphate fertilizers is essential in agriculture, because they supply farmland with nutrients for growing plants. However, heavy metals might be included as impurities in natural materials and minerals, so heavy metals can also be present in phosphate fertilizers or other chemical fertilizers. The aim of this work was to assess the heavy metal content and contamination status of agricultural soils in the Hamadan province of Iran used for the cultivation of different crops, including cucumber, potatoes, and sugar beet. Surface soil samples were collected and analyzed to determine the total concentration of specific elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), before the pollution index was calculated for each element. Soils used for the cultivation of the three types of crop were not contaminated with As, Cr, Cu, Pb, or Zn. However, the pollution indices for Cd were 1.1, 4.4, and 3.8 in cucumber, potato, and sugar beet fields, respectively, which indicated moderate, high, and high levels of contamination, respectively. Soils from potato and sugar beet fields were heavily contaminated with Cd, which may have resulted from long-term overuse of phosphate fertilizers.     

某农药工业园区周边土壤重金属含量与风险评价

以苏南某农药工业园区周边30km2区域为研究区,采用同心圆法采集土壤样品183个,分析了农药工业园区周边土壤Cd、Cr、Cu、Ni、Pb、Zn、Hg和As8种重金属含量、空间变异性、来源及潜在风险.结果表明:以自然背景值为评价标准,研究区表层土壤Hg、Cu、Cd和Pb平均含量超过自然背景值,其中Hg和Cu含量最高;以国标二级标准为评价标准,土壤Cd、Cr、Ni、Pb、Zn、As6种重金属的单项污染指数平均值均小于1,Hg和Cu分别为1.59和1.05.在农药工业园区周边土壤重金属污染较重的东南方向和西北方向,随着与园区距离的增加,土壤Cd、Ni、Pb、Cr、As、Hg、Zn和Cu含量先上升、后下降、再趋于平稳.通过分析农药工业园区周边土壤重金属综合污染指数发现,距离园区约200～1000m周边土壤污染的风险较大,而1000m以外逐渐达到安全范围.利用地统计学和GIS相结合进行分析发现,8种重金属污染指数有明显的空间变异.依据相关分析与主成分分析结果推测,Zn、Ni、Cr、Pb和As主要来源于成土母质,而Hg、Cu和Cd主要与人类活动有关.     

第二松花江下游稻田土壤重金属含量特征及来源分析

于2008年秋季,在长期引用第二松花江（二松）江水进行灌溉的前郭灌区,采集了具有不同灌溉历史的稻田耕层土壤样品65个,测定了土壤中7种重金属含量,分析重金属在表层土壤中的累积特征,探讨发生累积的重金属的输入途径和来源.结果表明：稻田土壤中Cu、Pb、Zn、Cd、Ni、As、Hg的含量分别为14.1～28.4、37.6～57.4、53.3～84.4、0.044～0.367、18.4～37.0、3.25～12.11、0.031～0.155 mg·kg^-1.Pb、Hg、Cd表现出明显的累积趋势,其含量超过基线值的比例分别为100.0%、38.7%和66.1%,其余重金属元素未出现累积现象.随着灌溉历史的增长,稻田土壤中Pb含量呈逐渐降低趋势,Hg含量呈逐渐升高趋势.Cd含量与灌溉历史的关系不明显.稻田土壤中累积的Pb主要与过去使用含Pb汽油产生的废气沉降有关;Hg主要来源于曾受污染的二松江水,随引水灌溉输入;Cd主要来源于化肥、农药等农用化学品的施用.尽管本区稻田土壤中Pb、Hg、Cd出现明显累积现象,但其生态风险水平很低,不会对当地农业生产及粮食安全构成威胁.     

Heavy metal contamination and health risk assessment in soil-rice system near Xinqiao mine in Tongling city,Anhui province,China

In this study, paddy soil and rice grain samples were collected from the vicinity around the Xinqiao mine in Tongling, China to test for the presence of heavy metals (Cd, Ni, Cr, Cu, Zn, and Pb) in soil-rice system. Results indicated that the soil samples were primarily contaminated with Cd and Cu and followed with Zn and Pb. In rice grains, Cd, Cu, and Cr concentrations exceeded recommended guidelines. However, the regional distribution of heavy metals in rice grains and soil was inconsistent. The bioaccumulation factor of heavy metals in rice grains decreased in the order of Cd > Zn > Cu > Ni > Cr > Pb. The BAF was significantly positively correlated with TCLP-extractable metals and significantly negatively correlated with soil pH. However, the relationship between soil organic matter and the BAF in rice grains was complex. Health risk assessment through rice intake showed that hazard quotients of Cu and Cd were greater than 1 and could pose a considerable non-cancer health risk to adults and children; meanwhile, Cr, Ni, and Cd could pose an unacceptable cancer risk. The results indicated that the government must take measures to reduce heavy metal contents in paddy soil and rice.     

成都平原北部水稻土重金属含量状况及其潜在生态风险评价

为了解成都平原水稻土重金属含量状况和潜在的生态风险,选取成都平原北部水稻土典型区域为研究对象,采集了158个表层土壤样品,分析了土壤中pH值和Cd、Cu、As、Hg、Pb、Cr、Ni 7种重金属元素含量,以20世纪80年代测定的成都平原土壤重金属元素背景值为评价标准,采用Hakanson潜在生态危害指数法对研究区域的重金属潜在生态风险进行了评价。结果表明:研究区域水稻土Cd、Hg、Ni、Cu、Pb、Cr和As平均含量分别为0.709、0.187、32.08、34.12、31.52、82.13 mg/kg和7.25 mg/kg;Cd、Ni、Cu和Hg 4种重金属超过《土壤环境质量标准》(GB15618-1995) Ⅱ级标准值样本比例分别为87.34%、8.23%、3.80%和3.80%,Cd含量超标严重。7种重金属元素变异系数幅度为18.35%-49.03%,由大到小依次为Cd、Hg、Cu、As、Ni、Cr、Pb。75.32%的样本达到中度或较强重金属潜在生态风险,区域整体表现为中度潜在生态风险(RI平均值为198.65),Cd和Hg为高生态风险元素,对潜在生态风险贡献率分别为62.27%和20.78%,As、Pb、Cu、Ni、Cr为低生态风险元素;风险概率图显示城区周边和绵远河沿线的潜在生态风险等级较高。因此,成都平原水稻土农业生产中应采取一定的措施防控农产品Cd和Hg污染。     

Pollution Assessment and Potential Sources of Heavy Metals in Agricultural Soils around Four Pb/Zn Mines of Shaoguan City,China

A total of 455 agricultural soil samples from four nonferrous mines/smelting sites in Shaoguan City, China, were investigated for concentrations of 10 heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Zn). The mean concentrations of the metals were 72.4, 5.16, 13.3, 54.8, 84.5, 1.52, 425, 28.2, 529, and 722 mg kg^?1, respectively. The values for As, Cd, Hg, Pb, and Zn were more than 8 and 1.5 times higher than their background values in this region and the limit values of Grade II soil quality standard in China, respectively. Estimated ecological risks based on contamination factors and potential ecological risk factors were also high or very high for As, Cd, Hg, and Pb. Multivariate analysis (Pearson's correlation analysis, hierarchical cluster analysis, and principal component analysis) strongly implied three distinct groups; i.e., As/Cu/Hg/Zn, Co/Cr/Mn/Ni, and Cd/Pb. Local anomalies for As, Cu, Hg, and Zn by a probably anthropogenic source (identified as mining activity), Co, Cr, Mn, and Ni by natural contribution, and a mixed source for Cd and Pb, were identified. This is one of the few studies with a focus on potential sources of heavy metals in agricultural topsoil around mining/smelting sites, providing evidence for establishing priorities in the reduction of ecological risks posed by heavy metals in Southern China and elsewhere.     

The spatial distribution,contamination, and ecological risk assessment of heavy metals of farmland soils in Karashahar–Baghrash oasis,northwest China

The issue of heavy metal pollution is of high concern due to its potential health risks and detrimental effects on human beings, animals, and plants. In this study, farmland soil samples from 79 sampling sites were collected in Karashahar–Baghrash oasis, northwest China, and the contents of eight heavy metal elements (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) were determined by standard methods. The spatial distribution, pollution, and ecological risks of heavy metals were analyzed based on Geographical Information System (GIS) technology, contamination factor (CF), pollution load index (PLI), and potential ecological risk index (RI). Results indicated that: (1) The average contents of Cd, Cr, Ni, Pb, and Zn exceeded the background values of irrigation soils of Xinjiang by 54.0, 1.34, 1.39, 3.44, and 5.01 times, respectively. The average contents of Cd exceeded the national standard of China by 10.80 times; (2) The pollution order of CF was ranked as Cd > Zn > Pb > Ni > Cr > Cu > As > Mn, and the ecological risk order of E_rⁱ was ranked as Cd > Ni > As > Cu > Ni > Pb > Cr > Zn. The average PLI of the study area showed heavy pollution level, and the average RI of the study area fell into considerable risk; (3) The moderately polluted areas with moderate potential ecological risks distributed in the northern parts, whereas heavily polluted areas with considerable potential ecological risks distributed in the southern parts of the study area; (4) Cr, Cu, and Mn of farmland soils were mainly originated from natural factors. Cd, Ni, and Pb were mainly originated from anthropogenic factors. As and Zn may be associated with both natural and anthropogenic factors. Cd contributed most to the PLI and RI of the farmland soils in the study area.     

城市绿化树种香樟不同器官对土壤重金属的富集特征

为了了解不同土壤重金属浓度梯度及污染梯度下香樟不同器官的富集特征,测定了香樟树叶、树枝、树干和根际土壤中6种重金属元素(Cu、Zn、Pb、Cr、Mn、Ni)的含量.结果表明: 香樟地上部分重金属含量因器官、元素种类、根际土壤重金属浓度的不同而存在差异.香樟树叶和树枝重金属含量的大小顺序均为:Mn＞Zn＞Cu＞Cr＞Pb＞Ni,树干重金属含量为:Mn＞Zn＞Cr＞Pb＞Ni＞Cu.树叶对Mn的富集系数较高,为2.409;树干对Ni的富集系数较高,分别为树叶、树枝的8.6和17倍,且在不同土壤重金属浓度梯度下,香樟树干对Cu、Zn、Pb、Cr、Ni的富集系数均明显高于其他器官.香樟地上部分器官对Cu、Zn、Pb、Cr、Mn、Ni 6种重金属元素的综合富集能力大小顺序为:树叶＞树干＞树枝.随着土壤重金属污染等级的增加,香樟地上部分各器官的富集系数均逐渐降低.研究区域平均胸径为22 cm的单株香樟对重金属元素富集效能的大小顺序为:树叶＞树干＞树枝,其中树干对Cu、Zn、Pb、Cr、Ni的积累量均显著高于树叶和树枝.表明香樟对6种重金属元素均有一定的富集能力,并且树干对Pb和Ni的富集效能明显,分别占地上部分总积累量的82.7%和91.9%,能很好地富集并稳固土壤中的Pb和Ni,可作为修复治理土壤重金属污染的备选树种.