海河流域西部地区水库沉积物重金属潜在生态风险评价

Potential ecological risks assessment of heavy metals in the reservoir sediment of the western Haihe River basin

海河流域西部地区水库是下游平原区重要的水源地,水库沉积物重金属的潜在生态风险受到关注.运用Hakanson潜在生态风险评价方法对海河流域西部10座水库沉积物重金属的潜在生态风险进行评价,并采集水库上下游河流沉积物与水库作对比分析.结果表明:海河流域西部水库沉积物中Cd超标严重,平均含量是背景值的1.67倍,最高达2.77倍;超过半数水库的Pb超出背景值.结合毒性系数,计算了沉积物重金属的潜在生态风险,依次为Cd>As>Pb>Ni>Cu>Cr>Zn.多数水库的Cd生态风险危害等级均在中等危害及以上,承担保定市和北京市供水功能的西大洋水库Cd生态风险等级为"强".水库上、下游河流沉积物重金属中Cd的生态风险显著高于水库自身,水库上游河流沉积物Pb、Cu、Ni的生态风险也高于水库,Zn和Cr的生态风险在水库上下游差异不显著.

The reservoirs distributed in the western part of Haihe River basin play a key role in drinking water supply in the densely populated region. The potential ecological risk of heavy metals stored in the reservoir sediments has drawn more attention during recent decades. In this study,a total of 10 reservoirs in the western Haihe River basin were sampled. The sediment samples were assessed by the Hakanson potential ecological risk evaluation index. The sediments of upstream and downstream rivers were also sampled for comparative analysis with those of the reservoirs. The results indicated the concentration of Cd was significantly higher than the background value in this region,it was 1. 67 times of the background value on average and the highest was 2. 77 times. The concentration of Pb was higher than the background value for more than half of the reservoirs. The potential ecological risk was evaluated by the toxic coefficient. The ecological risk level was decreased in the order of Cd〉As〉Pb〉Ni〉Cu〉Cr〉Zn. The ecological risk of Cd in most reservoir sediments belonged to a moderate harm. Xidayang Reservior,which supplied the drinking water for Beijing and Baoding,had the highest level of Cd pollution. The ecological risk of Cd in the upstream and downstream rivers was significantly higher than that of the reservoirs. In addition,the ecological risks of Pb,Cu and Ni in the upstream rivers were also higher than the reservoirs. The difference of ecological risks of Zn and Cr was not significant between reservoirs and rivers.