非常规水源补给城市河流表层沉积物重金属污染及风险评价

非常规水源补给城市河流水环境问题日益严重.因此,本文采集了凉水河水系表层沉积物,分析了6种重金属元素的污染特征,并采用富集系数法和潜在生态危害指数法,分别进行了重金属的来源解析和风险评价,以期为非常规水源补给河流的治理提供参考.结果表明,凉水河水系表层沉积物中Cd、Cr、Cu、Ni、Pb和Zn含量的均值分别为0.65、65.68、49.73、24.23、24.63和120.36 mg·kg-1,大部分元素超过了背景值.其中,Cd和Cu在整个区域沉积物中的富集系数均值分别高达10.45和2.59,Zn在凉水河上游和中游沉积物中的富集系数分别达到2.54和2.27,Pb在凉水河中游沉积物中的富集系数为1.64,均存在明显的人为输入过程,可能主要来自污水处理厂出水及周边城市生活污水和农田退水.潜在生态危害指数表明,凉水河水系沉积物整体上达到了强生态危害(RI=302.46),尤其是干流中游河段(RI=395.66);而沉积物质量基准结果表明,除个别样点外,凉水河水系沉积物基本无毒性.

Characteristics and ecological risk assessment of heavy metal pollution in unconventional supply urban river

Urban rivers with unconventional water sources have more and more serious environmental problems. In this study, surface sediments were collected from Liangshui River System (LRS) to study the pollution characteristics, sources and risk of heavy metals using enrichment factor (EF) and potential ecological risk index (RI). The results showed that the mean contents of Cd, Cr, Cu, Ni, Pb and Zn in the sediment samples were 0.65, 65.68, 49.73, 24.23, 24.63 and 120.36 mg·kg^-1, respectively, and most of them were higher than the soil background values. EF values revealed that Cd and Cu in the sediments of whole LRS, Zn in the upstream and midstream, and Pb in the midstream were mainly from anthropogenic sources (effluent of sewage treatment plant, domestic sewage and irrigation return flow). The RI values due to Cd, Cr, Cu, Ni, Pb and Zn in the sediments of LRS showed high-grade degree (RI=302.46 on average), especially in the midstream of Liangshui River. In addition, except for two sampling sites, there is no toxicity in the sediments of LRS.