Spatial distribution and potential ecological and health risks associated with heavy metals in the Ijero-Ekiti mining site,Nigeria

Artisanal gold mining,a labor-intensive and antiquated technique,is a growing industry and the source of income for rural communities all over the world.However,artisanal gold mining has potential negative and long-term effects on economy,environment,and society.This study collected soil samples from 16 sample points including a control point to examine the pollution degrees and spatial distribution of heavy metals,as well as ecological and health risks associated with heavy metal pollution in the Ijero-Ekiti mining site,Nigeria.Geographical Information System(GIS)and remote sensing technologies were used to identify regions with high concentrations of heavy metals and assess the environmental impact of gold mining activities.The results show that the mean heavy metal concentrations of 16 soil pointa are 8.94(±5.97)mg/kg for As,0.18(±0.54)mg/kg for Cd,0.11(±1.06)mg/kg for Co,14.32(±3.43)mg/kg for Cr,6.89(±0.64)mg/kg for Cu,48.92(±11.77)mg/kg for Fe,135.81(±30.75)mg/kg for Mn,5.92(±0.96)mg/kg for Ni,5.72(±1.66)mg/kg for Pb,and 13.94(±1.38)mg/kg for Zn.The study reveals that heavy metal concentration in soils follows the order of Mn>Fe>Cr>Zn>As>Cu>Ni>Pb>Co>Cd.An analysis of soil samples indicates that 3 principal components(PCs)account for 70.008%of the total variance and there are strong positive correlations between various pairs of heavy metals.The total potential ecological risk index(309.599)in the study area is high.Non-carcinogenic risk suggests that there may be long-term health impacts on people who work in the mining areas due to chronic exposure to the environment.Based on the study,the hazard index of carcinogenic health risks associated with heavy metals through ingestion is 520.00×10^(–4).Dermal contact from As and Cr also increases the risk of cancer,with the highest hazard index value of 18.40×10^(–4).The lowest exposure pathway,with the hazard index value of 0.68×10^(–4),indicates that the inhalation of heavy metals has a comparatively low risk of cancer.This study recommends the formulation of policies to monitor the Ijero-Ekiti mining site and other regions in Nigeria where indiscriminate artisanal gold mining activities exist.

Ecological risk assessment of heavy metals in sediments of Xiawan Port based on modified potential ecological risk index

Modified potential ecological risk index （MRI） was proposed based on the potential ecological risk index （RI） and risk assessment code （RAC） by modifying an index. The modified index was relevant to the chemical speciation of heavy metals. Xiawan Port, a typical region contaminated by industrial production, was selected as a case study area. The total concentrations and chemical speciation of heavy metals in sediments of Xiawan Port were analyzed. The experimental data indicate that Xiawan Port is seriously polluted by heavy metals, especially by Cd. The risks of heavy metals are evaluated by RI, RAC and MRI, respectively. The resluts of MRI show that the risks of heavy metals are in the decreasing order of Cd〉Pb〉Cu〉Zn. Comparison of results by different methods reveals that MRI integrates the characters of RI and RAC. MRI is recognized to be useful for risk managemnt of heavy metals in sediments.

Environmental availability and ecological risk assessment of heavy metals in zinc leaching residue

Four different methods,namely mineralogical analysis,three-stage BCR sequential extraction procedure,dynamic leaching test and Hakanson Potential Ecological Risk Index Method were used to access the environmental activity and potential ecological risks of heavy metals in zinc leaching residue.The results demonstrate that the environmental activity of heavy metals declines in the following order：CdZnCuAsPb.Potential ecological risk indices for single heavy metal are CdZnCuAsPb.Cd has serious potential ecological risk to the ecological environment and contributes most to the potential toxicity response indices for various heavy metals in the residue.

Content and Ecological Risk Assessment of Heavy Metals in Surface Sediment in Weishan Lake

[Objective] The aim was to analyze the content of heavy metals in surface sediment in Weishan Lake and further assess its ecological risk.[Method] Heavy metal pollution in surface sediment in Weishan Lake was studied,and the pollution indices and potential ecological risk indices of Cu,Zn,Pb,Cd and Cr were calculated to assess the potential ecological risk of heavy metal pollution.[Result] In surface sediment in Weishan Lake,the average contents of Cu,Zn,Pb,Cd,Cr and Ni were 64.78,185.05,78.76,0.17,37.76 and 46.84mg/kg respectively.Cr and Cd weren’t beyond standards in all stations,while Cu and Pb exceeded standards in all stations,with average super-standard multiple of 0.85 and 0.31,respectively,and Zn content wasn’t beyond standard in S2 station,with average super-standard multiple of 0.24.The average pollution indices of Cu,Zn,Pb,Cd and Cr were 1.85,1.23,1.31,0.34 and 0.47 respectively,with average comprehensive pollution index of 5.21,which showed that heavy metal pollution was light.In addition,heavy metal pollution in entryway portion and sea-route portion were more serious than that of breeding portion.Potential ecological risk assessment showed that the average potential ecological risk indices of Cu,Zn,Pb,Cd and Cr were 9.25,1.23,6.56,10.34 and 0.94 respectively,with average comprehensive potential ecological risk index of 28.33,and it revealed that potential ecological risk of heavy metals was slight.Besides,the potential ecological risk order of heavy metal pollution was sea-route portion>entryway portion>breeding portion.[Conclusion] The study could provide references for the regulation and improvement of ecological environment in Weishan Lake in the east route of south-to-north water transfer project.

Ecological risk assessment of heavy metals in surface seawater and sediment near the outlet of a zinc factory in Huludao City, Liaoning Province, China

At present, the methods widely applied to assess ecological risk of heavy metals are essentially single-point estimates in which exposure and toxicity data cannot be fully used and probabilities of adverse biological effects cannot be achieved. In this study, based on investigation of concentrations of six heavy metals(As, Hg, Pb, Cd, Cu, and Zn) in the surface seawater and sediment near the outlet of a zinc factory, located in Huludao City, Liaoning Province, China, a tiered approach consisting of several probabilistic options was used to refi ne ecological risk assessment for the individuals. A mixture of various heavy metals was detected in the surface seawater, and potential ecological risk index(PERI) was adopted to assess the potential ecological risk of heavy metals in the surface sediment. The results from all levels of aquatic ecological risk assessment in the tiered framework, ranging from comparison of single effects and exposure values to the use of distribution-based Hazard Quotient obtained through Monte Carlo simulation, are consistent with each other. Briefl y, aquatic Zn and Cu posed a clear ecological risk, while Cd, Pb, Hg, and As in the water column posed potential risk. As expected, combined ecological risk of heavy metal mixture in the surface seawater was proved signifi cantly higher than the risk caused by any individual heavy metal, calculated using the concept of total equivalent concentration. According to PERI, the severity of pollution by the six heavy metals in the surface sediment decreased in the following sequence: Cd>Hg>As>Pb>Cu>Zn, and the total heavy metals in the sediment posed a very high risk to the marine environment. This study provides a useful mathematical framework for ecological risk assessment of heavy metals.

Fractional distribution and risk assessment of heavy metal contaminated soil in vicinity of a lead/zinc mine

The pollution characteristics of Pb, Cd, Zn, Cu and Ni in soil of lead-zinc mining area were studied. The results indicate that the contamination degree followed the sequence of Cd〉Pb〉Zn〉Ni〉Cu and concentrations of Pb, Cd and Zn exceeded corresponding limits of the Chinese National Soil Environmental Quality Standard III. The soil was extremely polluted by Cd（Iego=5.26）, moderately to heavily polluted by Zn（Iego=2.38）, heavily to extremely polluted by Pb（Iego=4.13）. The results of BCR three-step sequential extraction procedure show that the active Cd, Pb and Zn were relatively high and might exert adverse effects on the plants grown in the soil, while Cu and Ni existed in soil with a relatively stable form. Potential ecological risk results indicate that soils were engaging in a high potential ecological risk by pollution of Cd and should be given rise to concern.

The Status Assessment and Preliminary Risk Assessment of Total Mercury in Sediments from Middle and Lower Reaches of the Yarlung Zangbo River

The occurrence and accumulation of total mercury (T-Hg) in sediments collected from the Yarlung Zangbo River (YLZB),the Lhasa River,the Niyang River and the Palongzangbu River were analyzed and the soil samples simultaneously collected from the bank were employed as control.Meanwhile,pollution status and potential ecological risk of Hg were calculated and assessed using index of geoaccumulation ( I geo ) and potential ecological risk assessment method (Er) in this study.The results showed that the T-Hg concentrations in sediments at eight sections of YLZB ranged from 4.23 to 48.1 μg/kg with mean concentration of 25.1 μg/kg,which was higher than background Hg value of soils in Tibet.T-Hg concentrations in sediments at three typical segments of YLZB were all significantly higher than those in soils collected from its bank (P<0.05).The Igeo and E r indexes revealed that the T-Hg pollution levels were slight pollution in two sections and moderate ecological risk in six sections of YLZB.Hg pollution risks also existed in the sediments of partial sections of the Lhasa River and the Niyang River,and slightly moderate Hg contamination with high ecological risk was presented in Lhasa urban district.The level of Hg in sediments of YLZB showed a notable spatial distribution characteristic with a trend of increasing firstly and then declining.Human activities played an important role in increasing Hg content in sediments of the river.

Risk Factor Assessment of Coal Mine Drainage Water on Surrounding Agricultural Soil: A Case Study at Barapukuria in Bangladesh

This study is performed to know the contamination level of heavy metals on the surrounding agricultural soils at the site of Barapukuria Coal Mine Company Limited (BCMCL). Total concentrations of eight heavy metals (Cu, As, Cd, Zn, Pb, Cr, Ni and Mn) were measured in that soil. To calculate the contamination level, the enrichment factor (EF), geoaccumulation index (Igeo) and Hakanson potential ecological risk index were done. Igeo values indicated that the study areas at all stations were suffering from moderate contamination with As. The results of enrichment factor revealed that soils in all stations were in extremely high enrichment condition by As metal. Under Hakanson potential ecological risk index, the contamination coefficient () and potential ecological risk index () were calculated. The degree of contamination at BCMCL area reflects moderate contamination. By considering the ecological risk index of a particular heavy metal, the order is as follows: Cd > As > Cu > Pb > Ni > Cr > Zn and Cd has the highest risk index and poses the greatest damage to the BCMCL area’s soil. EF, Igeo values and potential ecological risk index indicate that there is considerable As and Cd pollution, mainly caused by coal mine drainage water.

大连市农地土壤重金属污染及潜在风险评价

我国的耕地土壤重金属污染越来越严重,进行区域土壤重金属污染评价对于制定土壤重金属污染防治政策具有重要意义.旨在探究大连市典型农地土壤重金属污染状况,调查大连市农地表层土壤中的镍(Ni)、铬(Cr)、锌(Zn)、铜(Cu)、铅(Pb)、汞(Hg)和锰(Mn)7种重金属元素的含量,并定量评价研究区土壤重金属污染水平.研究选择大连市典型农地样地,等间距采集土壤表层样品,采用单因子指数法、内梅罗指数法和潜在生态风险指数法对研究区土壤样品进行污染状况评价和环境风险评价,以期为大连市农地土壤重金属污染的有效防治和农产品的安全健康生产提供科学依据.结果显示:①土壤样品中镍(Ni)、铬(Cr)、锌(Zn)、铜(Cu)、铅(Pb)的元素含量平均值分别为84.74、156.56、89.71、46.74和53.23mg/kg,均符合《土壤环境质量标准》(GB15618—1995)二级标准;②Hg的变异系数>0.5,污染源为点源污染,推测为人类活动导致;③单因子指数法表明Ni的富集作用最为严重,结合研究区实际情况推测其来源为人为源.内梅罗指数表明大连市土壤存在轻度污染.潜在生态风险指数表明大连市农地土壤存在轻微危害.④大连市农地土壤污染状况相对较轻,土壤质量总体水平较高,但仍需要采取相关措施防止重金属的富集,减少重金属对大连市农地土壤的负面影响.

湖南某锡矿尾矿库周边土壤重金属污染特征及其来源分析

文章采用地质统计分析、污染指数法、地质累积指数法及潜在生态风险指数法对锡矿尾矿库周边表层土壤中Cd、Pb、As、Zn、Cu含量、分布及污染程度进行统计与分析,并采用相关性分析及主成分分析法对重金属来源进行定性描述。结果显示:(1)重金属平均值为Pb 398.70 mg/kg、Cd 5.97 mg/kg、As 1135.68 mg/kg、Cu 77.04 mg/kg、Zn 545.63 mg/kg,所有样品重金属含量均超过背景值;(2)尾矿库周边土壤为重污染,周边区域污染程度为西北>北侧>东侧>南侧>西侧,5种重金属均具有累积性,Igeo均值显示Cd>As>Pb>Zn>Cu;(3)地块综合潜在风险为极强风险,单项生态风险指数为Cd>As>Pb>Cu>Zn;(4)As、Pb、Cu、Zn存在极显著相关性,Cd与Zn极显著相关,与As、Pb显著相关。研究区土壤污染原因主要为干滩扬尘、地表漫流、废水泄露及渗漏,以及周边历史上尾砂及尾砂填埋影响等。

热水解对鸡粪和牛粪厌氧消化及重金属风险的影响

为探究热水解预处理对鸡粪和牛粪在厌氧消化过程中产气效率的提升作用以及对消化残渣中重金属形态变化及潜在生态风险的影响。该研究以鸡粪和牛粪为处理对象,采用热水解处理技术,开展了连续中温厌氧消化试验。考察了热水解对畜禽粪污可生化性和重金属迁移风险。该研究还评估了连续施用厌氧消化鸡粪和牛粪15 a后土壤中重金属的积累量和Hakanson潜在生态风险指数。试验发现,鸡粪中木质纤维素含量占干固体总量的25%,牛粪为57.7%。热水解处理能够增强牛粪中木质纤维素的水解,热水解后木质纤维素的降解率为19.2%;但热水解对鸡粪的木质纤维素水解影响不明显,降解率仅为5.3%。鸡粪挥发性固体(volatile solid,VS)产气率为482 L/kg,热水解后产气率提升了12.4%;牛粪产气率为321 L/kg,热水解后产气率提升了31.2%。仅通过热水解不能降低鸡粪中重金属的迁移风险;而经过厌氧消化后,除Hg和Ni外,其他重金属迁移风险均降低到了低风险水平。牛粪经过热水解和厌氧消化处理后重金属向残渣态转换,但迁移风险没有明显改善。连续施用鸡粪和牛粪15 a后,土壤未出现的重金属积累,且15 a内总潜在生态风险等级处于低风险。该研究结果可为鸡粪和牛粪的能源化、无害化处理以及土地利用应用提供了理论依据和数据指导。

黔中磷矿区土壤重金属污染及其生态风险评价

为评价黔中磷矿区土壤重金属污染风险,采用梅花布点法在磷矿区周边区域和无矿区不同地层天然土壤采集24件表层土壤样品,测定Cu、Pb、Zn、As、Hg、Se、Cd、和Cr含量,并采用内梅罗综合污染指数(NPI)、地累积指数(I_(geo))以及Hankanson潜在生态危害指数(RI)对磷矿区土壤重金属的污染程度和潜在生态风险进行评价。结果表明,黔中磷矿区土壤中Hg、Se、Cd、As、Pb、Zn和Cr等元素平均含量分别为贵州土壤背景值的37.58倍、24.40倍、19.26倍、18.09倍、2.67倍、2.17倍和1.78倍,各重金属富集特征明显,Cu元素平均含量未超过贵州省土壤背景值。研究区土壤中Hg、Se、Cd、As、Pb、Zn和Cr等元素NPI平均值介于4.59~69.32之间,处于重度污染水平,而Cr和Cu元素NPI平均值分别为1.89和1.21,处于轻度污染水平。研究区Hg元素I_(geo)平均值为4.45,处于严重至极重污染;As、Se和Cd元素I_(geo)平均值介于3.35~3.65之间,处于重度污染;Pb、Zn和Cr元素I_(geo)平均值0.21~0.44之间,处于未污染至中度污染水平,而Cu元素I_(geo)平均值为-0.83,显示其未受到污染。潜在生态风险评价结果表明,研究区土壤Hg元素处于极强生态风险水平,Cd处于强生态风险水平,Ad处于中等生态风险水平,而Cu、Pb、Zn和Cr均处于轻微风险水平。黔中磷矿区土壤RI平均值为2285.50,显示出极强生态风险,Hg是最主要的生态风险元素,应引起高度重视。

基于生物可利用性与宽浓度范围的Hakanson潜在生态风险指数法的创建——以小秦岭金矿区农田土壤为例

Hakanson潜在生态风险指数法是土壤重金属潜在生态风险评价的一种常用方法,研究与实践证明其有效性的同时,也发现了其不足之处:忽略了土壤重金属不同形态之间潜在生态风险的差异,且只重视重金属含量高于参考值时的生态风险,而对低于参考值时的情况没有给予考虑,以致特定情况下的评价结果不能很好地反映实际生态风险,因而有必要创建适用性更广的Hakanson潜在生态风险指数法。为此,基于全过程控制优化的思想,引入了生物可利用性毒性系数,并将修正浓度与参考值差值引入计算公式,创建了基于生物可利用性与宽浓度范围的Hakanson潜在生态风险指数法,实现了对重金属不同形态风险贡献的差异及重金属浓度低于参考值情况下潜在生态风险的准确把握。以小秦岭金矿区为典型区域,辅以对采集土样重金属总量及5种形态含量的分析,开展案例研究。结果表明,基于生物可利用性与宽浓度范围的Hakanson潜在生态风险指数法能客观地揭示土壤重金属的潜在生态风险,具有更大的适应性,是一种有效的潜在生态风险评价方法。

黄河口国家公园湿地土壤重金属污染评价

为了研究黄河口国家公园湿地土壤污染状况和生态风险,沿黄河故道东营段、黄河入海口以及沿海处共设20个采样点进行土壤采集,对铅、镉、铬、铜、锌、镍、汞、砷8种重金属含量进行检测,并利用综合污染指数法、地累积指数法和潜在生态风险指数法进行土壤污染评价。结果表明:研究区铅、镉、铬、铜、锌、镍、汞、砷元素的质量比分别为16.4、0.11、57.3、14.0、46.9、20.0、0.014、7.71 mg/kg,均符合农用地土壤污染风险管控标准要求;研究区土壤综合污染指数为0.57,地累积指数为-0.23,潜在生态风险指数为65.54,表明研究区属于无污染土壤,存在轻微潜在生态风险。

Hakanson指数法评价水体沉积物重金属生态风险的应用进展

介绍了Hakanson指数法的基本原理和近些年来在监测水体沉积物重金属生态风险评价中的应用情况。

巢湖北岸烔炀河流域池塘沉积物中重金属污染特征

在巢湖北岸烔炀河流域,选择不同利用类型的池塘钻取了沉积物柱状样,分析了沉积物重金属元素浓度,并剖析了重金属在水平、垂向上的分布特征和污染程度。结果表明,池塘表层沉积物中Cr、As、Hg、Cd、Cu、Pb、Ni、Zn浓度分别为56.5~91.0、6.4~10.1、0.06~0.11、0.10~0.25、18.07~28.77、11.58~17.60、15.94~19.0、42.26~68.07 mg/kg;垂向上随着沉积物深度增加,重金属浓度总体呈下降趋势。烔炀镇老镇区池塘(S1)表层沉积物中重金属浓度高于其他池塘。烔炀河流域池塘沉积物中重金属Cr、Hg、Cu、Zn、As等5种重金属元素具有同源性,受成土母质影响,而Ni、Pb、Cd 3种重金属受人类活动影响;池塘表层沉积物重金属综合潜在生态风险指数处于轻微生态风险。

玛曲高寒退化草甸土壤重金属污染风险评价

为了分析玛曲高寒草甸土壤重金属含量分布及重金属污染风险,采集玛曲高寒退化草甸土壤样品,分析研究区表层土壤(0—20 cm)中Cr、Ni、Cu、Zn、As、Cd、Hg、Pb等八种重金属含量,描述玛曲高寒草甸土壤重金属的空间分布特征,采用单因子污染指数、内梅罗污染指数、地累积指数评价重金属污染程度并分析重金属污染潜在生态风险,以相关性分析、主成分分析和聚类分析表征同源性重金属。结果表明:(1)研究区内As、Cd的质量分数高于背景值,Ni的质量分数偏低,变异系数大小为Cr>Hg>Cd>Cu>As>Ni>Zn>Pb;(2)Cd单因子污染指数为轻微污染,地累积指数反映As属于未受污染与轻微污染之间,各重金属元素均无潜在生态风险;以国标和土壤背景值为标准,内梅罗综合污染指数表明玛曲未受到重金属污染;(3)主成分和相关性分析表明玛曲土壤中Ni、Cu、Zn、As、Cd、Pb等元素具有相同或相似的来源,Ni和Pb的来源优先顺序最大,Cr和Hg含量呈现弱相关。

污泥中重金属赋存形态与生态风险评价

为掌握生活污水污泥中重金属的污染状况与生态风险,以南方某城市27座生活污水厂的污泥为研究对象,分析了污泥中Hg、As、Zn、Cr、Cd、Ni的总量及赋存形态,采用潜在生态风险指数法(RI)和风险评价编码法(RAC)评价了污泥中各重金属的生态风险。结果表明,因评价对象不同,每种方法其结果可能会产生较大差异,但综合各方法评价结果可知,南方某城市生活污水厂污泥中Cd应作为首要关注的重金属污染物。

煤炭产区周边土壤重金属污染特征和风险评估

以长治市襄垣县为研究区域,探究村庄、电厂、化工、煤矿及选煤厂周边土壤中Cr、Zn、As、Cd、Pb、Hg、Ni及Cu等8种重金属的差异性累积特征,采用Hakanson潜在生态风险指数法评价煤炭产业园区周边土壤重金属的污染程度和生态风险。结果表明:As在村庄周边土壤中的含量显著高于电厂、化工、煤矿及选煤厂;Hg在选煤厂周边土壤中的含量显著高于化工和煤矿;Hg和Cd的潜在风险指数均为最高,大体达到中等潜在生态风险水平以上。

长江上游河流底泥沉积物重金属及生态风险评价——以滇中大姚县主要河流为例

重金属在底泥沉积物中的扩散和积累决定了水体的环境质量。为了解长江流域水生态系统状况,以长江上游金沙江流域大姚县主要河流底泥沉积物为研究对象,研究其中重金属含量特征和污染情况,利用修正内梅罗指数法、潜在生态危害指数法、聚类分析法和主成分分析法评价重金属污染现状,并对重金属污染物来源进行探讨。结果表明,主要河流底泥沉积物pH值为8.0,呈弱碱性。各重金属元素潜在生态风险指数和各流域综合潜在生态风险指数均为轻微级,总体处于清洁水平。全区各主要河流RI值中主要贡献者均为Cd、Hg元素,两者贡献率各占30%左右,说明重金属Cd、Hg是底泥潜在生态风险的主要来源。江底河Cu平均含量为372.35 mg/kg,是云南土壤背景值的9.3倍,长江水系沉积物背景值的10.6倍,其内梅罗污染指数达3.72,为重度污染,说明局部需关注矿业开采导致的Cu污染。