贵州草海沉积物重金属时空分布特征与生态风险评价

Spatiotemporal distribution and potential ecological risk assessment of heavy metals in the sediments of Lake Caohai,Guizhou,China

在草海选取代表性点位采集表层沉积物和沉积物柱芯,测定沉积物Cr、Ni、Cd、Co、Pb、Zn和Sb等重金属含量,研究草海沉积物重金属时空变化特征、来源及潜在生态危害。结果表明：草海表层沉积物中Cd、Pb、Zn和Sb在湖泊北部、湖心及西南湖区含量较高,且由北向西南方向呈扇形分布,主要来源于周边矿产资源的开发;Cr、Ni和Co在湖泊最西端区域含量较高,主要受城镇生产生活污水排放影响;草海沉积物中Cd和Sb污染最严重,其地质累积指数分别为1.50-4.62（平均值3.10）和1.63-3.45（平均值2.61）;潜在生态危害指数显示,草海沉积物Cd的生态风险较高,且湖心区域最严重。草海沉积物柱芯中重金属的垂直剖面分布正好对应了草海流域的矿产开采历史。尽管流域矿产资源开采活动已经停止,但以往矿产资源开采及冶炼过程中产生的重金属仍是目前草海重金属污染的主要来源。因此,应制定合理措施,严格控制重金属污染来源,并建立有效的沉积物重金属污染治理措施,恢复草海生态环境。

A total of 19 surface sediments and 5 sediment cores were collected at typical sites in Lake Caohai, located in Guizhou Province. The spatiotemporal distribution and sources of seven heavy metals （Cr, Ni, Cd, Co, Pb, Zn and Sb） in the sediments were investigated, and the potential ecological risks of those heavy metals were assessed. The results showed that the concentrations of Cd, Pb, Zn and Sb in the surface sediments were relatively higher in the north, central and southwest areas of the lake; these pollutants mainly resulted from the mineral exploitation in the catchment. The concentrations of Cr, Ni and Co were relatively higher in the most west area, mainly due to urban sewage discharge （westernmost areas）. Based on the geoaccumulation index （Igeo）, Cd and Sb were obviously enriched in the sediments of Lake Caohai. The potential ecological risk of Cd was higher in the lake sediments, especially in the sediments from the central part of the lake. The profiles of the variations of heavy metals contents in the sediment cores corresponded well to the history of the mineral exploitation in the catchment of Lake Caohai. Although the mineral exploitation was ended, its remaining problems are still the main cause of heavy metal pollution in Caohai Lake. Therefore, it is necessary to adopt reasonable methods to strictly control the heavy metal pollution and to establish suitable measures to effectively treat the heavy metal pollution, recovering the ecological environment of Lake Caohai.