通州区河流沉积物重金属污染评价

Assessment of Heavy Metal Pollution in Surface Sediment of Rivers in Tongzhou District

为了解通州区河流沉积物重金属污染现状,保障区域水生态安全,采集了11条主要河流25个沉积物样品,测定了重金属Hg、As、Pb、Cr、Cd和Cu的含量,采用地累积指数法、潜在生态风险指数法对重金属污染程度及潜在生态风险进行了评价。结果表明:(1)全区沉积物重金属Hg、As、Pb、Cr、Cd、Cu平均含量为0.673、6.27、24.40、78.60、0.25、45.80 mg/kg,总体高于中国水系沉积物平均值;(2)全区重金属平均地累积指数为Hg(1.53)>Cr(0.75)>Cu(0.38)>Cd(0.11)>Pb(-0.77)>As(-0.90),沉积物主要受Hg、Cr、Cu、Cd污染;北运河污染最为严重,主要来源于工业废水及城市污水的排放;(3)全区重金属平均潜在生态风险系数为Hg(336)>Cd(63)>Cu(12)>As(9)>Cr(5)≈Pb(5),Hg具有极强生态危害;通州全区潜在生态风险指数RI=430,其中北京城市副中心RI=633,重金属生态危害更为严重。研究结果能够为通州区的河流底泥治理及生态修复提供科学依据。

Tongzhou district serves as a sub-center of Beijing and is the primary flood and domestic water discharge district of Beijing.There are two river systems(Chaobai and Beiyun)in the district and comprehensive treatment and improvement of the water environment and local ecology is an important issue for the district.In this study,we evaluated the pollution status and ecological risk of heavy metals in the surface sediments of rivers in Tongzhou district using the geoaccumulation index and potential ecological risk index.The objectives were to provide a scientific basis for improving water quality in the area.In September and October of 2016,samples of surface sediments were collected at 25 locations in 11 primary rivers in Tongzhou district and the sediments were analyzed for Hg,As,Pb,Cr,Cd and Cu.The average content of Hg,As,Pb,Cr,Cd and Cu in surface sediments were,respectively,0.673 mg/kg,6.27 mg/kg,24.40 mg/kg,78.60 mg/kg,0.25 mg/kg and 45.80 mg/kg,higher than the national average in China.The average geoaccumulation index of each heavy metal followed the order:Hg(1.53)>Cr(0.75)>Cu(0.38)>Cd(0.11)>Pb(-0.77)>As(-0.90),indicating that Cr,Cu and Cd pollution is light and Hg pollution is moderate.The Beiyun River is seriously polluted due to discharge of industrial waste water and municipal sewage to the river.The average potential ecological risk index of each heavy metal followed the order:Hg(336)>Cd(63)>Cu(12)>As(9)>Cr(5)≈Pb(5),indicating that Cd,Cu,As,Cr and Pb pose only a slight ecological risk while Hg poses a high ecological risk.The average potential ecological risk index of heavy metals for the whole of Tongzhou district was 430,but the risk index was 633 for the core sub-center area,suggesting that the pollution and ecological risk are concentrated in the core sub-center area of Beijing.This study provides scientific evidence for controlling pollution and remediating sediments in rivers of Tongzhou district.