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 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.

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.

Source analysis and risk evaluation of heavy metal in the river sediment of polymetallic mining area:Taking the Tonglüshan skarn type Cu-Fe-Au deposit as an example,Hubei section of the Yangtze River Basin,China

In this paper,25 sampling points of overlying deposits in Tonglushan mining area,Daye City,Hubei Province,China were tested for heavy metal content to explore pollution characteristics,pollution sources and ecological risks of heavy metals in sediments.A geo-accumulation index method was used to evaluate the degree of heavy metal pollution in the sediment.The mean sediment quality guideline quotient was used for evaluating the ecological risk level of heavy metal in the sediment.And a method of correlation analysis,clustering analysis,and principal component analysis was used for preliminary analysis on the source of heavy metal in the sediment.It was indicated that there was extremely heavy metal pollution in the sediment,among which Cd was extremely polluted,Cu strongly contaminated,Zn,As,and Hg moderately contaminated,and Pb,Cr,and Ni were slightly contaminated.It was also indicated by the mean sediment quality guideline-quotient result that there was a high ecological risk of heavy metals in the sediment,and 64%of the sample sites had extremely high hidden biotoxic effects.For distribution,the contamination of branches was worse than that of the main channel of Daye Dagang,and the deposition of each heavy metal was mainly influenced by the distance from this sample site to the sewage draining exit of a tailings pond.The source analysis showed that the heavy metals in the sediment come from pollution discharging of mining and beneficiation companies,tailings ponds,smelting companies,and transport vehicles.In the study area,due to the influence of heavy metal discharging from these sources,the ecotoxicity of heavy metals in the sediment was extremely high,and Cd was the most toxic pollutant.The research figured out the key restoration area and elements for ecological restoration in the sediment of the Tonglüshan mining area,which could be referenced by monitoring and governance of heavy metal pollution in the sediment of the polymetallic mining area.

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.

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。

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。

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。

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。

基于改进主成分分析法的水环境中重金属污染流域水质生态评价方法研究

为了准确掌握水环境中的重金属污染情况,提高水质生态防治效果,提出了基于改进主成分分析法的水环境中重金属污染流域水质生态评价方法研究。选取研究污染流域水质区域,收集4个区域地表水,测定金属元素含量,通过四类分析与评价法,实现对水环境中重金属污染状况及潜在危害的生态评价,得出评价的B区域和C区域水质综合重金属污染较高,铁元素在四个区域均在第一主成分,是污染程度最高的,整体生态评价为及格。评价结果表明所提方法可以对水环境中重金属污染状况进行精确的评价,辅助保护人民身体健康与生态环境。

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。

农耕表层土壤重金属污染生态风险预警研究

重金属污染是造成生态环境污染的主要因素,为此研究农耕表层土壤重金属污染生态风险预警方法,旨在提高生态环境和农产品的质量安全。以济宁市某农耕区域为预警评估对象,对其实施采样、处理和样品分析。根据重金属元素含量统计分布,利用综合污染指数法(Pi)与潜在生态风险评价法(RI)划分各重金属元素污染等级和潜在生态风险指数。通过生态风险指数法(I_(ER))实现农耕表层土壤重金属生态风险预警评估。通过对研究区测试,得出所提方法能够准确实现农耕表层土壤重金属污染生态风险预警。

某关停铅蓄电池企业土壤重金属污染特征及生态风险评价

为探明江苏省某铅蓄电池企业生产6年关停后对该地块土壤是否造成污染,对土壤中Pb、Cu、Zn、Hg、As、Cd、Ni、Cr这8种重金属采样分析,基于主成分分析和径向基函数(RBF)插值法分析地块土壤重金属的污染分布特征。利用单因子指数法和Nemerow综合指数法对污染地块土壤环境质量分析,对于涉及人体健康生态风险评价采用Hakanson潜在生态危害指数法开展综合评价。结果表明:研究区域土壤已遭受明显的人为外源重金属污染,且局部重金属富集程度较高,纵向污染区域主要集中在100cm以上土壤中,区域整体污染程度达到轻度污染,其中危废库局部土壤受污染程度已为中度污染,建议对该单元土壤开展进一步风险评估和修复;研究区域土壤尚不存在潜在生态风险,但是需重点关注危废库构筑物单元的土壤环境质量,主要威胁来自土壤中的镉,其EiCd潜在生态风险指数等级已达到强的级别。建议该地块后续开发利用时不作为农用地使用或进行局部区域土壤修复治理。

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.

延河底泥的重金属分布特征和生态风险评价

为了评估延河底泥的重金属分布特征和污染风险,以延河为研究对象,采集底泥样品,测定延河流域9个代表性断面中Cr、Pb、Cu、Zn、Ni、As、Cd和Hg等8种重金属的含量。运用潜在生态风险指数法和地累积指数法计算延河底泥重金属的生态风险,并通过Pearson相关系数甄别底泥中重金属的来源。结果表明:延河底泥中Cr、Pb、Cu、Zn、Ni、As、Cd和Hg平均含量分别为124.56、98.21、66.00、46.20、22.64、4.45、0.14、0.11 mg·kg^(-1),其中Pb、Hg、Cu、Cr、Cd分别超过陕西省环境背景值5.8、4.4、3.2、1.8、1.4倍,Ni、As和Zn低于陕西省环境背景值;延河底泥重金属的潜在生态风险指数平均值为303.14,从高到低依次为S8>S1>S5>S7>S2>S3>S6>S9>S4,中等生态风险和强生态风险为11.1%和88.9%,主要由Hg导致;同时,底泥中的Cr、Pb、Hg和Cu的地累积指数大于0,属于轻度-中度污染,Cd的地累积指数在-0.37~0.11之间,属于无-轻度污染,Ni、Zn和As的地累积指数小于0,属于无污染;延河底泥Ni、Cd和Cu呈现高度相似性,产业布局、道路交通和地质活动是其主要污染源。

某冶炼厂附近土壤中Hg的时空变化及风险评价

测定了2005年、2011年和2021年某冶炼厂土壤中Hg的质量分数,并采用地累积指数法、潜在生态风险指数、非致癌风险评估法对冶炼厂附近土壤进行污染评价。结果表明:冶炼厂各采样点土壤中Hg的质量分数时空分布差异性较大,整体呈现出以冶炼厂为中心的扩散现象,距离冶炼厂最近的S4和S5采样点的Hg污染最为严重;冶炼厂附近的S2、S4、S5、S6、S7采样点Hg的污染,处于极重程度,具有极强的潜在生态风险;距离冶金厂最近的S4和S5采样点土壤中Hg的非致癌健康危害指数相对较高;儿童接触Hg的非致癌健康危害指数高于成人,对于Hg的暴露更为敏感。

生态修复后某矿区下游农田土壤金属污染特征与风险评价

为研究广东省某矿区开展生态修复多年后下游农田土壤的金属污染状况,选取该矿区下游某村周边农田土壤及灌溉水渠作为研究对象,对该区域采集了40个土壤表层样本和8个水体样本,利用Arcgis软件对农田土壤样品中As、Cu、Cd、Pb、Zn、Mn和Fe_(2)O_(3)的质量分数进行克里金空间插值,解析该区域农田土壤金属的空间分布特征;采用综合污染指数法和潜在生态风险指数法对该区域耕作层土壤中As、Cu、Cd、Pb、Zn和Mn进行风险评价。结果表明,40个土壤样品中As、Cd、Cu、Zn和Pb的超标率分别为77.5%、70%、87.5%、27.5%和67.5%,说明调查区域农田土壤污染属于多金属复合污染,且对农作物的生产和安全产生巨大的威胁。部分土壤样品中As、Pb和Cd含量超过了中国农用地土壤污染风险管制值,需采取严格管控措施。通过分析土壤金属的空间分布,发现土壤金属含量超标点位主要位于灌溉口与受污染河流周边,且含量与离灌溉口距离成反比。结合目前灌溉水样中的金属均未超标的情况,得出该区域农田土壤污染是由该矿区生态环境修复前所产生的含金属灌溉水导致土壤中金属的积累引起的。土壤中金属的综合污染指数平均值为1.89,属于轻微污染;潜在生态风险指数平均值为277.63,潜在生态风险程度为中。调查区的农田土壤存在系统性风险,应当加强土壤环境监测与修复。

湖南某石煤矿区重金属污染现状及生态风险评价

为研究湖南某石煤矿区重金属污染现状,采用ICP法测定了水体和土壤中多种重金属含量,并分别采用内梅罗污染指数法和潜在生态危害指数法进行风险评价。结果表明,水中Cd、Cr(Ⅵ)、Zn、Fe和Mn平均浓度分别为1.935 5、0.025 3、6.024 9、16.222 0和4.214 9 mg/L,污染指数分别为387.10、5.06、3.01、54.07和42.15,污染程度从大到小排序为:Cd>Fe>Mn>Cr(Ⅵ)>Zn;土壤中Pb、Zn、Cr、As、Hg和Cd平均含量分别为8.51、38.59、18.65、10.01、0.18和3.41 mg/kg,平均生态风险系数分别为2.13、0.98、0.85、18.00、28.55和339.80,污染程度从大到小排序为:Cd>Hg>As>Pb>Zn>Cr,整个矿区的综合潜在生态风险指数为390.31,污染程度为较高生态危险。矿区受到多种重金属复合污染,废石堆和沉淀池的排水口下游区域较严重。

城市湖泊底泥污染分析及生态风险评价——以沅江市中心城区为例

近年来,随着经济的快速发展和城市化进程的加快,城区污水排放量增加,城市湖泊底泥污染问题变得十分突出。采用营养盐有机指数法、重金属内梅罗指数法和潜在生态风险指数法,分析沅江市中心城区湖泊底泥的污染状况和风险水平,以期为城市湖泊底泥污染治理和水环境系统的可持续发展提供科学依据。结果显示:各湖泊底泥污染风险水平受人类活动和工业企业污染影响的程度由大到小排序为X湖>S湖>L湖>H湖;H湖底泥营养盐和重金属整体处于尚清洁水平;L湖L1#、L7#、L8#点位浮泥层底泥存在不同程度营养盐或重金属超标情况,L1#过渡层底泥重金属潜在生态风险指数达到了中等风险水平;S湖S7#、S12#点位浮泥层底泥重金属潜在生态风险指数达到了中等及以上污染风险水平,S3#点位浮泥层底泥重金属潜在生态风险指数达到了强风险水平;X湖X3#、X4#点位浮泥层底泥重金属内梅罗指数最高达到了重度污染水平,与潜在生态风险指数的极强风险水平相吻合,建议进一步核实后结合实际情况对污染湖泊开展内源污染治理工作。