嘉兴北部湖荡沉积物氮磷和重金属分布及评价

Distribution Characteristics of Pollution from Nitrogen, Phosphorus and Heavy Metals in Surface Sediments in Northern Lake Area of Jiaxing

文章以嘉兴市北部湖荡区表层沉积物为研究对象,采用有机指数对研究区域表层沉积物氮磷进行评价,采用地累积指数法和潜在生态危害指数法评价重金属污染状况。结果表明,研究区的有机氮、总氮、总磷平均含量分别为3.57%、0.77 mg/g和0.73mg/g,根据有机指数评价结果,研究区88.89%的区域属于Ⅲ级尚清洁状态。重金属中Cr、Ni、Zn和Cd平均含量分别为89.09、36.88、149.75和2.37 mg/kg,均超过嘉兴市嘉善县土壤背景值,特别是Cd超49.5倍。相关性分析结果显示这7种重金属元素中Cr、Ni、Pb、Zn、Cu和As两两呈极显著相关或显著相关,说明这6种重金属污染来源相近。而Cd不与其他元素具有相关性,表明其来源与其他几种元素都不同。综合2种评价方法的结果,嘉兴市北部湖荡区表层沉积物中Cd为最主要的污染元素,且具有很强的生态危害。

The concentrations and spatial distribution of TN,TP,Cr,Ni,Cu,Zn,As,Cd and Pb in the sediment of northern lake area of Jiaxing were determined.The contamination and potential ecological risk of TN and TP were determined by organic index method.The heavy metal elements were evaluated by geoaccumulation index and potential ecological risk index.The results indicated that average contents of organic matters(OM),total nitrogen(TN),total phosphorus(TP)in surface sediments were 3.57%,0.77 mg/g,0.73 mg/g,respectively.Average contents of Cr,Ni,Zn and Cd were 89.09,36.88,149.75,and 2.37 mg/kg,which were much higher than the background values of Jiashan County,Jiaxing.Cd in particular was49.5 times exceeding the value.The correlation analysis demonstrated that there were significant correlations among Cr,Ni,Pb,Zn,Cu and As,indicating that the pollution sources of the six heavy metals were similar.Cd,however,was not related to other elements,which means its source was different from other elements.The results of the two evaluation methods showed that Cd was the most important pollution element in surface sediments of the northern lake area of Jiaxing City,and it has a strong ecological hazard.