典型铅锌矿流域土壤重金属生态风险评价及环境容量预测

Ecological Risk Assessment and Environmental Capacity of Soil Heavy Metals in Lead-zinc Area

为探究广西典型铅锌矿区重金属的生态风险及其环境容量,以广西阳朔铅锌矿流域思的村为例,采用内梅罗综合污染指数(Nemerow multi-factor index,NIPI)和环境容量综合指数PI对研究区内土壤重金属进行污染状况评价、环境容量评价与预测,并基于ArcGIS经验贝叶斯克里金空间插值法对其生态风险评价和环境容量水平进行分区。结果表明:Cu、Zn、Cd、Hg和Pb的含量均值超过广西土壤环境背景值的3.29~10.67倍,存在不同程度的富集;Zn、Cd、Hg和Pb超标较为严重,超标率为46.43%~77.98%,对环境及人类造成的风险危害较大。内梅罗综合指数评价结果显示在不同深度层集的中度-重度污染区域占比高达70%,存在Pb、Zn和Cd多种元素复合污染;环境综合指数结果显示:PI范围为-9.84~1.24,整体环境容量水平低,主控元素是Cd、Hg和Pb。综合评价研究区土壤重金属污染状况严重,整体存在复合污染,环境容量水平低,总体上污染程度和环境容量与思的河关系密切,呈现与思的河空间距离愈远,污染程度逐渐减轻、环境容量逐渐增加的趋势。相比居民区,农业活动区的土壤环境容量基本处于超载状态,存在着较大的环境风险,重金属污染程度更高,对农作物危害更大,间接危害人体健康。基于近百年的环境容量预测结果显示环境总容量在理想状态下有逐渐好转的趋势。

To reveal the ecological risks and the environmenial capacity of heavy metals in a typical lead-zinc mining area in Guangxi Province,taking the lead-zinc mine basin in the Village of Sidi of Yangshuo County,Guangxi as the research object,the content of Cr,Ni,Cu,Zn,As,Cd,Hg,and Pb in the surface soil of Sidi river were analyzed and determined.The Nemerow multi-factor index(NIPI)and comprehensive environmental capacity index(PI)were employed to evaluate the soil heavy metal pollution status and environmental capacity,and empirical Bayesian Kriging spatial interpolation method based on ArcGIS software was employed to divide the ecological risk assessment and environmental capacity level of soil heavy metals in the watershed.The results show that the average content of Mn,Cu,Zn,Cd,Sb,Hg,and Pb is 3.29~10.67 times higher than the environmental quality standards for soils in Guangxi,indicating that it has been differently enriched in topsoil.Zn,Cd,Hg,and Pb exceed the standard seriously,with the exceeding rate ranging from 46.43%to 77.98%,indicating that it has greater risks to the environment and humans.The results of NIPI show that there is compound pollution in the study area,with 70%of the proportion of moderately polluted and severely polluted areas in different depth layers and the main controlling elements are Pb,Zn,and Cd.The results of the PI show that the range of PI is-9.84~1.24,which is low environment capacity overall,and the main controlling elements are Cd,Hg,and Pb.The comprehensive evaluation shows that there is serious soil heavy metal pollution,low environmental capacity levels,and overall compound pollution in the study area.The degree of pollution shows a spatial distribution trend of gradually decreasing with increasing spatial distance from the Sidi River,while the opposite is true for environmental capacity.Compared with residential areas,the soil environmental capacity of agricultural activity areas is basically overloaded,and with greater environmental risks.Heavy metal pollution in agricultural activity areas is higher,which is more harmful to crops and indirectly endangers human health.The total environmental capacity of the study area has a trend of gradual improvement under the ideal condition based on the prediction results of environmental capacity in the last hundred years.