重污染感潮河道底泥重金属污染评价及释放规律研究

Evaluation of heavy metal pollution and release from sediment in a heavily polluted tidal river

以珠江流域重污染感潮河道为研究对象,采用地累积指数、变异系数、相关性分析和潜在生态风险指数对底泥中重金属的污染状况进行了评价,并考察了静态条件和模拟感潮条件下重金属的释放规律.结果表明:河道底泥的重金属污染严重,Cu、Zn、Cr、Cd和Pb的平均含量分别为2083.96、1791.60、117.84、1662.92和3.71mg·kg-1,均大大超过广州市土壤背景值;各金属的富集程度为Cu>Zn>Cr>Cd>Pb,其中Cu的富集程度已经达到6级,为极强污染;各重金属元素在底泥中的变异系数较小,沿程分布比较平缓,Cu与Cr、Cd与Cr之间的相关性良好.以广州市土壤背景值为参比值进行评价,郭村涌底泥中的重金属生态危害顺序为Cd>Cu>Cr>Zn>Pb,总体表现为极强的生态危害程度.与静态释放相比,感潮作用可明显加速底泥重金属的释放,其平均释放速率提高了0.77～4.20倍,释放量增加了0.32～1.78倍,同时涨退潮过程低水位时段较之高水位时段底泥重金属释放平均速率增加0.48～3.33倍.

A heavily polluted tidal river of the Pearl River Basin,the Guocun River,was studied to evaluate the contamination status of heavy metals in sediment based on the geoaccumulation index,variation coefficient,correlative coefficient and potential ecological risk index.The release of heavy metals was also studied under static and simulated tidal conditions.The experimental sediment was severely polluted by heavy metals, the average content of Cu、Zn、Cr、Cd and Pb were 2083.96、1791.60、117.84、1662.92 and 3.71 mg·kg^-1 respectively,which were much higher than the background soil values in Guangzhou.The heavy metals were enriched in the order Cu〉Zn〉Cr〉Cd〉Pb.Cu pollution reached grade 6,making it the most serious pollution factor.The distribution of heavy metals in sediments was flat because the variation coefficients of heavy metals were small.The correlation between Cu and Cr was satisfactory,as was that between Cd and Cr.Compared to soil background values of Guangzhou,the heavy metals in Guocun River showed very strong ecological risk,and the order of potential ecological risk of the five heavy metals was Cd〉Cu〉Cr〉Zn〉Pb.The tidal process sped up the release of contaminants from surface sediment greatly in comparison with static release.The average release rate of heavy metals was 0.77-4.20 times faster under tidal conditions than under static conditions,and the quantity released increased 0.32-1.78 times.At the same time,the average release rate of heavy metals was 0.48-3.33 times faster during low-water periods than during high-water periods under flood and tide conditions.