涨渡湖水系沉积物重金属分布及生态风险浅析

Distribution and Ecological Risk of Heavy Metals in Sediments of the Zhangdu Lake Water System

了解涨渡湖重金属污染状况及对环境的影响,为长江中下游湖泊重金属风险评价和污染防治提供基础数据。2022年7月在涨渡湖水系设置11个采样点采集沉积物样品,并测定样品中Cr、Mn、As、Ni、Cu、Zn、Cd和Pb共8种重金属的含量,同时分析样品沉积物中微塑料吸附重金属的种类,并评估了重金属生态风险。结果显示:涨渡湖水系不同研究区域沉积物中重金属含量分布不同,表现为邻近干支流>连通水道>阻隔湖泊;沉积物中微塑料表面吸附重金属包括Zn、Ag和Sn,其中,Zn和Ag占微塑料表面吸附元素百分比较高,分别为20.01%和8.49%。生态风险评估结果显示,涨渡湖水系沉积物中重金属污染负荷指数I_(PL)平均值为1.15,处于中等污染水平;潜在生态风险指数I_(R)平均值为78.96,处于低度污染水平。综合结果表明,涨渡湖水系沉积物重金属总体处于低-中等污染水平,其中长江干支流江段重金属污染程度和生态风险高于连通水道和阻隔湖泊,这种重金属分布和污染格局主要受研究区域周围环境、人类活动和水文条件的影响。

Zhangdu Lake is the epitome of lake evolution in the middle and lower reaches of the Yangtze River.Understanding heavy metal pollution in Zhangdu Lake and the environmental risks they pose provides basic data for risk assessment and the prevention and control of heavy metal pollution in Zhangdu Lake and other lakes in the middle and lower reaches of Yangtze River.In this study,we determined the concentrations of eight heavy metals(Cr,Mn,As,Ni,Cu,Zn,Cd and Pb)in sediments from the Zhangdu Lake system and identified the heavy metals adsorbed by microplastics.The pollution status and ecological risk of heavy metals in sediments were then evaluated using the pollution load index(I_(PL))and potential ecological risk index(I_(R)).In July 2022,sediments in the Zhangdu Lake system were collected for the determination of the eight heavy metals and the analysis of heavy metals adsorbed by microplastics at 11 sampling sites,located in the isolated lakes,connecting waterways and the adjacent Yangtze mainstream and tributaries.Results show that the heavy metal concentrations in sediments varied according to aquatic system type in the Zhangdu Lake system,decreasing in the following order:Yangtze mainstream and tributaries>connecting waterways>isolated lakes.The heavy metals mainly adsorbed by microplastic surfaces included Zn,Ag,and Sn,and the concentrations of Zn and Ag were much higher,comprising 20.01% and 8.49% of the adsorbed metals.Ecological risk assessment revealed that the average value of I_(PL) for the Zhangdu Lake system was 1.15,indicating a moderate pollution level,and the average value of I_(R) was 78.96,indicating a low pollution level.The comprehensive evaluation results indicated that heavy metal pollution in the sediments of the Zhangdu Lake water system was at a low-moderate level.In addition,the pollution degree and ecological risk in the mainstream and tributaries of Yangtze River were higher than those in connecting waterways and isolated lakes.The distribution and pollution pattern of heavy metals were primarily affected by the surrounding environment,human activities and hydrological conditions in the study area.