于桥水库表层沉积物重金属分布特征及其与底栖动物的关系

Distribution of Heavy Metals in Surface Sediment of Yuqiao Reservoir and Its Relationship with Macroinvertebrate Community

对重金属生态风险分布特征及其与底栖动物群落结构及多样性分布特征之间的相关关系进行分析,为于桥水库生态系统重金属污染监测与治理提供技术支持。2015年7月至2016年6月,在于桥水库内布设11个采样点,采集水下表层15 cm的沉积物样品测定Zn、Cr、Cu、Pb、As、Hg和Cd浓度,潜在生态指数法评价污染风险;采集底栖动物鉴定种类、计算生物量和多样性指数。结果表明:于桥水库表层沉积物中重金属元素平均含量大小顺序为Zn>Cr>Cu>Pb>As>Hg>Cd,各重金属平均含量均低于背景值,但Cu、Zn、Cr、Cd、Hg的最高值均高于背景值;表层沉积物中重金属元素的平均潜在生态风险指数为66.13,整体处于轻微风险水平,各重金属元素的单项潜在生态风险从高到低的顺序为Hg>Cd>Cu>As>Cr>Pb>Zn;底栖动物腹足纲密度、底栖动物Shannon-Wiener指数与ECd、EHg、RI均具有明显的负相关关系;底栖动物Margalef指数与ECu、EPb、ECd具有明显的负相关关系。于桥水库内重金属元素浓度高值区主要集中于库中心、水库入口、水库出口及水库北岸,应重点加强上游引水污染物控制。

Yuqiao Reservoir is one of the most important drinking water sources of Tianjin City and its ecological environment is directly related to drinking water safety.As an integral part of the reservoir ecology,the sediment has attracted increasing attention.In this study,we analyzed the distribution of heavy metals in the surface sediment of Yuqiao Reservoir and its relationships with the structure and biodiversity of the macroinvertebrate community.In July and November of 2015 and April and June of 2016,seasonal monitoring of heavy metals and macroinvertebrates in Yuqiao Reservoir was carried out at 11 sites,evenly distributed in Yuqiao Reservoir.Parameters included Zn,Cr,Cu,Pb,As,Hg and Cd,and macroinvertebrate species composition and biomass.Based on the monitoring data,we calculated the potential ecological risk index(RI)of heavy metals and the macroinvertebrate community biodiversity including Shannon-Wiener diversity(H),Margalef richness(d)and Pielou evenness(J)indices.The potential ecological risk index was used to evaluate the risk posed by heavy metals and correlation was used to analyze the relationship between macroinvertebrate biodiversity and the risk index.The average concentration of heavy metals in surface sediment followed the order,Zn>Cr>Cu>Pb>As>Hg>Cd,and all were below the background value,indicating a low human contribution to heavy metals in the surface sediment.However,the highest concentrations of Cu,Zn,Cr,Cd and Hg did exceed background values,indicating large spatial differences in heavy metal distribution.The highest index value(84.17)of the average comprehensive potential ecological risk for heavy metals occurred in June 2016 and the lowest(55.43)was in April 2016,indicating temporal differences in the distribution of heavy metals.The average value(66.13)indicates a low overall ecological risk.The potential ecological risk of the different heavy metals followed the order Hg>Cd>Cu>As>Cr>Pb>Zn,with the primary ecological risk posed by Hg,Cd and Cu.The density of Gastropoda and the Shannon-Wiener diversity index(H)of the macroinvertebrate community both displayed significantly negative correlations with ECd,EHg,and RI.The negative correlations of the Margalef richness index(d)with ECu,EPb,and ECd were also significant.The high heavy metal concentrations were mainly in the center,inlet,outlet and north bank of Yuqiao Reservoir and strengthening pollution control upstream of the reservoir is therefore recommended.