北京市平谷应急水源地周边农业土壤中重金属分布及风险评价

采用ArcGIS空间分析技术和多元统计方法研究了北京市平谷应急水源地周边农业土壤中重金属空间分布及来源,并基于潜在生态危害指数法进行了生态风险评价.结果表明,土壤中重金属含量均值由大到小为Mn >Pb >Cr >As >Hg >Cd,所有重金属含量均值都高于北京市土壤背景值.Pb、Cd和As污染较为严重,含量均值分别为96.78、0.25、28.40 mg·kg^-1,且主要是人为来源;Mn和Cr元素平均含量稍高于北京市土壤背景值,主要来源为自然源;Hg元素的平均含量也稍高于北京市土壤背景值,是自然源和人为源共同作用的结果.重金属元素单项污染潜在生态风险系数从大到小依次为Cd >Hg >As >Pb >Cr >Mn,6种重金属综合潜在生态风险指数RI值为169.29,为中等生态危害,东南方向土壤重金属生态危害高于西北方向.综上所述,该水源地的土壤已经受到重金属的潜在威胁,其生态风险不容忽视.

Distribution and Ecological Risk Assessment of Heavy Metals in Agricultural Soils Surrounding a Contingency Water Source, Beijing

Heavy metals in soils surrounding water source area pose direct risks to the water safety. Here the spatial distribution and sources of heavy metals in agricultural soils around a contingency water source of Pinggu, Beijing, were elucidated by ArcGIS and multivariate analysis. The ecological risk assessment of soil heavy metals was also performed using potential ecological risk index(RI). The mean concentrations of heavy metals in soils were in order of [Mn] >[Pb] >[Cr] >[As] >[Hg] >[Cd], all exceeding the soil background values of Beijing. The soils were seriously polluted by Pb, Cd and As, with the mean concentrations of 96.78, 0.25 and 28.40 mg·kg^-1, respectively. These metals mainly came from the human activities via mineral exploitation and transportation. The concentrations of Mn, Cr and Hg were slightly higher than the soil background values. Manganese and Cr were derived from the natural sources by weathering of rock and soil parent materials, and Hg from both human activities and natural sources. The potential ecological risk factor(E_rⁱ) for heavy metals decreased in order of [Cd] >[Hg] >[As] >[Pb] >[Cr] >[Mn]. The total potential ecological risk index of heavy metals in soils was 169.29, belonging to moderate potential ecological risk. There was higher potential ecological risk in the southeast than in the northwest areas. These results indicate that soils around the contingency water source of Pinggu, Beijing, is threatened deeply by heavy metals and that more attention should be paid to the potential ecological risk assessment.