重金属复合污染河道底泥淋洗动力学特征

Characteristics of Leaching Kinetics for River Sediments with Compound Contamination of Heavy Metals

文中以上海市崇明某河道底泥为研究对象,研究在不同pH、温度条件下,底泥中Cd、Cu、Pb的淋洗动力学特征(淋洗液为纯水),通过Tessier连续提取法分析底泥淋洗前后的重金属形态变化。结果表明:重金属淋洗量随时间增长呈上升趋势,且分为快反应、慢反应及淋洗平衡3个阶段,Elovich方程可以较好地描述该淋洗过程(R^(2)=0.670~0.983,SE=3.296×10^(-14)~1.130×10^(-6)),略优于双常数方程(R^(2)=0.653~0.982,SE=3.366×10^(-14)~1.381×10^(-6)),说明该淋洗过程为非均相扩散过程;pH降低(pH值=5~9)、温度升高(15~35℃),重金属淋洗量均有增加;淋洗脱除的重金属主要为不稳定形态,有机结合态重金属的去除与底泥中富里酸含量有较强相关性,淋洗脱除率表现为Cd>Pb>Cu,即31.34%>23.85%>22.86%,重金属的环境危害性有所下降。

In this research,taking the sediments of a river in Chongming Shanghai as the research object,the leaching kinetics characteristics of Cd,Cu and Pb in the sediments under different pH value and temperature conditions were studied(pure water used for eluent).The occurrence form changes of heavy metals before and after leaching were analyzed by Tessier sequential extraction procedures.The results showed that,the leaching amount of heavy metals increased with the increase of time,and was divided into three stages:fast reaction,slow reaction and equilibrium leaching.Elovich equation could describe the leaching process well(R^(2)=0.670~0.983,SE=3.296×10^(-14)~1.13×10^(-6)).It was slightly better than the double constant equation(R^(2)=0.653~0.982,SE=3.366×10^(-14)~1.381×10^(-6)),indicating that the leaching process was heterogeneous diffusion process.The leaching amount of heavy metals increased when pH value decreased(pH value=5~9)and temperature increased(15~35℃).The heavy metals removed by leaching mainly were unstable forms,there was a strong correlation between the removal of organic bound heavy metals and the content of fulvic acid in sediment,the removal rates were Cd>Pb>Cu(31.34%>23.85%>22.86%),and the environmental harm of heavy metals decreased.