中国北方某湖泊底泥污染分析及重金属潜在生态风险评价

Analysis of sediment pollution and evaluation of potential ecological risk of heavy metals in a lake,northern China

以中国北方某湖泊(以下称A湖)为例,开展了底泥中氮磷污染及重金属生态风险评价研究,探讨多种评价方法的相关性,并分析底泥中氮磷元素向上覆水迁移造成水体富营养化的风险。选取A湖中心区域的10个底泥监测点位数据,对其总氮、总磷及重金属(Pb、Cr、As、Cd、Ni)含量进行分析,并采用有机污染指数法评价总氮污染,单因子指数法评价总磷污染,SEM/AVS比值法、地累积指数法与潜在生态风险指数法综合评价重金属潜在生态风险。结果表明:10个底泥监测点位的有机氮指数介于0.0037~0.1116之间,平均值为0.0674,总氮污染程度为中度污染;磷污染指数介于0.86~1.64之间,平均值为1.24,总磷污染程度为中度污染;底泥中氮磷元素较为丰富,造成水体富营养化的风险较大;SEM/AVS值均<1,地累积指数值均<0,潜在生态风险指数值均<150,SEM/AVS比值法与地累积指数法显示无重金属污染,潜在生态风险指数法显示重金属潜在生态风险程度为最低级。

Taking a lake(short for Lake A)in northern China as an example,the authors studied the ecological risk assessment of nitrogen and phosphorus pollution and heavy metals in sediment,discussed the correlation of various evaluation methods and analyzed the risk of water eutrophication caused by the migration of nitrogen and phosphorus from sediment to overlying water.Ten sediment monitoring points in the center of Lake A were selected to analyze the contents of total nitrogen,total phosphorus,and heavy metals(Pb,Cr,As,Cd,and Ni).The organic index method was used to evaluate the total nitrogen pollution,and the single factor index method was used to evaluate the total phosphorus pollution.The potential ecological risk of heavy metals was evaluated comprehensively by SEM/AVS ratio,geo-accumulation index and potential ecological risk index.The results show that the organic nitrogen index of the 10 sediment monitoring points ranges from 0.0037 to 0.1116,with an average value of 0.0674.The degree of total nitrogen pollution is medium.The total phosphorus pollution index is between 0.86 and 1.64,with an average of 1.24,the pollution level of total phosphorus is moderate pollution.The sediment are rich in nitrogen and phosphorus,which causes a great risk of water eutrophication.The research results show that the SEM/AVS values are all less than 1,the geo-accumulation index values are all less than 0,and the potential ecological risk index values are all less than 150.The SEM/AVS ratio method and geo-accumulation index method show that there is no heavy metal pollution.The potential ecological risk index method shows that heavy metals of this region are in the lowest level of potential ecological risk.