固城湖退圩还湖区沉积物重金属特征及生态风险评价

Distribution characteristics and ecological risk assessment of heavy metals in surface sediments of Guchenghu Lake and its retreating and returning lake area

为探讨退圩还湖对固城湖表层沉积物重金属污染特征、空间分布和生态风险的影响,对退圩区和湖区表层沉积物重金属(Fe、Mn、As、Zn、Cr、Co、Ni、Cu、Cd和Pb)含量进行对比分析,采用地累积指数法和潜在生态风险指数法评价沉积物重金属污染现状和潜在生态风险程度,利用相关性和聚类分析法解析重金属主要污染物的潜在来源.结果表明,退圩区沉积物重金属中Cd(0.21mg/kg)和湖区沉积物重金属中Cd(0.56mg/kg)和Zn(145.33mg/kg)和Pb(41.17mg/kg)含量的平均值分别达到江苏省土壤背景值的2.45、6.55、2.24和1.87倍.湖区表层沉积物重金属Cd、Zn、Cu和Pb含量显著高于退圩区.地累积指数法评价显示退圩区中Cd为轻度污染;湖区中Cd为中度污染,Zn、As、Cu和Pb为轻度污染.潜在生态风险指数表明,湖区表层沉积物生态风险高于退圩区;Cd是湖区与退圩区最主要的生态风险贡献因子,可能与水产养殖活动以及工业废水排放有关.固城湖退圩还湖对于降低固城湖重金属生态风险有着积极作用.

In order to explore the impact of returning from the polder to the lake on the pollution characteristics,spatial distribution and ecological risks of heavy metals in the surface sediments of Guchenghu Lake,the heavy metals(Fe,Mn,As,Zn,Cr,Co,Ni,Cu,Cd and Pb)contents were compared and analyzed,using the geo-accumulation index method and the potential ecological risk index method to evaluate the status of heavy metal pollution in sediments and the degree of potential ecological risk,using correlation and cluster analysis to analyze the potential sources of major heavy metal pollutants.The mean values of Cd(0.21mg/kg)in sediments of polders and Cd(0.56mg/kg),Zn(145.33mg/kg)and Pb(41.17mg/kg)in sediments of lakes were 2.45,6.55,2.24 and 1.87 times the background value of Jiangsu Province soil,respectively.The contents of heavy metals Cd,Zn,Cu and Pb in the surface sediments of the lake area were significantly higher than those of the retreating polder area.The evaluation by geoaccumulation index method showed that Cd in the retreat area was slightly polluted;Cd in the lake area was moderately polluted,and Zn,As,Cu,Pb were mildly polluted.The potential ecological risk index showed that the ecological risk of surface sediments in the lake area was higher than that in the retreat area;Cd was the most important contributor to ecological risk in the lake area and the retreat area,which may come from aquaculture activities and industrial wastewater discharge.The return polder land to Guchenghu lake plays a positive role in reducing the ecological risk of heavy metals in Guchenghu Lake.