污染黑土中重金属的形态分布与生物活性研究

通过对污染和清洁黑土的耕层、非耕层分层采样分析,比较了Cd,Pb,Cu和Zn等在同一土壤耕层和非耕层以及不同采样点土壤中的形态分布和生物活性.结果表明,无污染黑土中这些重金属的形态分布一般为:残渣态>有机结合态>铁锰结合态>碳酸盐结合态>可交换态,外源污染则使可交换态重金属的含量增加.以生物有效性系数和迁移系数进行重金属生物活性评价,其在黑土中生物活性大小的顺序为:Cd>Cu>Zn>Pb.污染愈严重的土壤,重金属的生物活性和自身的淋溶能力相对较强,在非耕层中也表现出较高的生物活性.综合重金属在土壤中的含量和生物活性,发现2个污染点的黑土中Cd和Pb对当地农业生产和地下水安全已构成潜在的威胁.

SPECIATION DISTRIBUTION AND BIOACTIVITY OF HEAVY METALS IN CONTAMINATED PHAIOZEM

After sequential extraction of the surface and subsurface soil of contaminated and clean phaiozem, the speciation distribution and bioactivity of heavy metals in surface-subsurface of different sites were studied. Results indicated that the species distribution of heavy metals in clean phaiozem was residue > bound to organic matters > bound to Fe-Mn oxides > bound to carbonates > exchangeable fraction. Pollution occurring would change the general distribution trend and increase the exchangeable fraction percentage. The bioactivity of four heavy metals based on assessment of bioavailability and mobility index were cadmium > copper > zinc > lead. The ingravescence pollution would increase metal bioactivity and soil leachability. Down movement and high bioavailability of metals would appear in the subsurface soil. Considering with the increasing concentration and bioactivity, cadmium and lead in the two contaminated sites had threatened safety of agricultural production and groundwater.