新河污灌区土壤中重金属的形态分布和生物有效性研究

Bioavailability and species distribution of heavy metals in sewage-irrigated soil from Xinhe

通过野外采样调查和实验分析,对北京市新河污灌区土壤中Cu、Pb、Zn、Cd4种重金属的含量、形态分布和生物有效性进行了研究.首次尝试运用体外消化法研究了土壤中重金属的生物有效性问题,并与经典的Tessier五步连续提取法的结果进行了对比.结果发现,新河污灌区土壤中,Cd的浓度超过国家二级标准,Cu、Pb、Zn的浓度未超标.土壤中Cu、Pb、Zn主要以残渣态存在,Cd主要以有机结合态存在,且Cd的可交换态比例最高,生物有效性也最高.体外消化法分析得到的重金属生物有效性成分的含量要比利用化学形态分析法分析得到的高,但Cu、Pb、Zn、Cd4种重金属的生物有效性排序是相同的,即Cd>Zn>Pb>Cu.两种方法提取的重金属含量之间有相关关系.

The in vitro digestion method, originally designed by Lawrence M. Mayer, was used to study the bioavailability of heavy metals in soil from the XINHE sewage irrigation region. In addition a five step sequential extraction method was used to determine the speciation of heavy metals in soil, including Cu,Pb,Zn and Cd. The resuhs of the biological method were compared with those of the chemical method. The bioavailability of the four heavy metals was higher by the biological method than by the chemical method, but both gave the same order： Cd 〉 Zn 〉 Pb 〉 Cu. The values of the extraction have correlation between the two methods.