太湖贡湖湾主要河流表层沉积物重金属污染及其生态风险评价

Heavy metal pollution in sediments of rivers around Gonghu Bay and assessment of its potential ecological risk

太湖贡湖湾是无锡和苏州重要的水源地,对其周边主要入湖河流的重金属含量进行调研,并对生态风险进行评价十分必要。通过分析环贡湖湾主要河流表层沉积物中Cu、Zn、Pb、Cr、Cd、Ni金属元素的含量特征,利用Hakanson潜在生态危害指数法评价其生态危害,同时考察了重金属间的相关性,旨在为预防和治理贡湖湾重金属污染提供科学依据。研究结果表明,各重金属元素含量平均值为w(Cu):(36.26±1.21)mg/kg,w(Zn):(116.53±7.01)mg/kg,w(Pb):(90.76±2.39)mg/kg,w(Cr):(76.46±3.48)mg/kg,w(Cd):(3.22±0.11)mg/kg,w(Ni):(34.04±2.19)mg/kg,通过对比《土壤环境质量标准》(GB 15618-1995)和沉积物重金属环境背景值,发现贡湖湾周边河流的主要污染是元素Cd和Pb。由潜在生态危害指数RI可知,4号点位(小溪港河口)污染最重,达到强生态危害。单因子潜在危害系数值表明各点位表层沉积物主要生态风险因子是元素Cd,达到中等危害程度。各元素生态风险影响程度从高到低依次为:Cd>Pb>Cu>Ni>Zn>Cr。生态修复工程对重金属生态危害降低起到了一定的作用,但是小溪港流域的变化较小;重金属相关分析表明,Cu-Cr,Zn-Pb之间呈极显著正相关的关系(R2<0.01),具有较好的同源性。

Gonghu Bay is an important source of water for Wuxi and Suzhou cities. It is thus indispensable to monitor the heavy metal levels in the main inflows of these rivers and assess the potential ecological risks. To provide basic information for controlling heavy metal pollution in Gonghu Bay,the concentrations of six heavy metals（ Cu,Zn,Pb,Cr,Cd and Ni） in surface sediments were analyzed,and the potential ecological risks associated with these heavy metals were assessed using the Hakanson ecological risk index. The correlation coefficients among the heavy metals were also calculated. The results showed the average content of heavy metals as follows w（ Cu） ：（ 36. 26 ± 1. 21） mg / kg,w（ Zn） ：（ 116. 53 ± 7. 01） mg / kg,w（ Pb） ：（ 90. 76 ± 2. 39） mg / kg,w（ Cr） ：（ 76. 46 ± 3. 48） mg /kg,w（ Cd） ：（ 3. 22 ± 0. 11） mg /kg,w（ Ni） ：（ 34. 04 ± 2. 19） mg /kg. Based on the Environmental Quality Standard for Soil（ GB 15618-1995） and the background reference values of heavy metals,Cd and Pb were found to be the major polluting elements in the main inflows surrounding the bay. Based on the potential ecological risk index（ RI）,No. 4 point（ Xiaoxi Gang） was the most polluted,indicating extensive ecological harm. The potential ecological risk factor（ Eir） indicated that Cd was the major risk factor in surface sediments for all the points with a moderate level of harm to the ecological environment. The ecological risks associated with different heavy metals varied in the descending order of Cd,Pb,Cu,Ni,Zn and Cr. The ecological restoration project was found to have played some role in reducing the ecological risk levels in comparison to the reported levels from previous studies. However,small changes occurred in the Xiaoxigang River. The heavy metal correlation analysis showed that Cu-Cr and Zn-Pb had a significant positive correlation（ R^2〈 0. 01）,which indicated a good homology between them.