包头某稀土尾矿库周边土壤重金属污染特征与生态风险评价

为了解包头某稀土尾矿库周边表层土壤中重金属元素As、Cd、Cr、Cu、Ni、Pb和Zn的富集特征及污染程度和生态风险状况,以尾矿库南侧湿地和西侧农田为研究样点,以相对无污染的小白河黄河湿地自然保护区和尾矿库西侧8 km的农田为对照样地,利用国标方法进行重金属含量测定,并利用综合污染指数、污染负荷指数、地积累指数和生态风险指数法进行污染程度和生态风险评价。结果显示:各样点土壤重金属含量均高于国家和内蒙古土壤背景值,其中以Cd和As污染最为严重,且As超过国家二级标准(GB15618—1995)。尾矿库周边土壤的重金属污染程度和生态风险均显著高于对照样地。湿地土壤污染程度显著高于农田,且随着与尾矿库距离的增大而减轻。该稀土尾矿库是造成周边土壤重金属污染的根本原因。研究揭示了该地区的重金属污染特征和生态风险,可作为当地土地资源保护与生态恢复的科学依据。

Pollution Characteristic and Ecological Risk Assessment of Heavy Metals in Soils around Rare Tailings in Baotou

In order to assess the enrichment characteristics，and pollution levels and ecological risks，ecological pollution risks of heavy metals (As,Cd,Cr,Cu,Ni,Pb,and Zn) in the topsoil around rare tailings in Baotou region，the wetland located on the southern rim,and farmlands located on the west side of tailings were chosen as study plots.While the relatively non-polluted Xiaobaihe Yellow River wetlands,and the farmland soil about eight kilometers apart from the western tailing dam were chosen as control plots.All of the heavy metal contents were measured using the National Standard Methods.Their pollution levels and ecological risks were assessed using Comprehensive Pollution Index,Pollution Load Index,Geoaccumulation Index,and Ecological Risk Index.The result showed that all of those heavy metal contents were higher than the background values of China and Inner Mongolia.Among them,Cd and As showed the most serious pollution,and the As contents exceeded the National Standard II (GB15618-1995).Both the heavy metal pollution levels and the potential ecological risks in soils around the tailings were significantly higher than that in the control plots.The pollution levels of wetland soils were significantly higher than that of farmland soils,and decreased with the distances of tailings.It was concluded that this rare tailing was the root cause of heavy metal pollution in the surrounding soils.This study explicated the pollution levels and ecological risks of heavy metals in this area,which could provide a scientific basis for the local land resources protection and ecological restoration.