污染土壤中有机质结合态重金属的研究

用物理与化学相结合的方法研究了2个污染土壤剖面中有机质结合重金属（Cd、Cu、Pb和Zn）的分布，把有机质相结合态重金属分为颗粒状有机质（POM）结合的重金属和与细土腐殖质结合的重金属。结果表明，土壤POM对重金属有明品的富集作用，其中〉2mmPOM重金属Cd、Cu、Pb和Zn的富集系数分别在1．4～3．2、2．5～2．6、2．8—3．9和3．0～3．9之间；而0．05～2mmPOM重金属Cd、Cu、Pb和Zn的富集系数分别在2．7～7．8、3．2～6．4、3．2～9．3和3．2～5．6之间，0．05～2mmPOM组分中重金属的平均富集高于〉2mmPOM组分。POM中重金属的富集程度与土壤重金属的积累呈正相关。有机质结合态重金属占土壤重金属总最的比例随土壤有机质积累而增高，表土层约40％以上的重金属以有机质结合态存在。

Organic matter associated heavy metals in polluted soils

The distribution of heavy metals in different size fractions of soils affects bioavailability of the metals. Understanding distribution of heavy metals in soils can provide useful information for evaluating environmental risk of the metals. In this study, both physical and chemical methods were applied to characterize organic matter-associated heavy metals in two metal-contaminated soil profiles. The results found that heavy metals, including Cd, Cu, Pb and Zn, in the soils were significantly enriched in particulate organic mater fractions (POM). The enrichment factor of Cd, Cu, Pb and Zn in >2mm POM fractions were 1.4~3.2, 2.5~2.6, 2.8~3.9 and 3.0~3.9, respectively, those in 0.05~1 mm POM fractions were 2.7~7.8, 3.2~6.4, 3.2~9.3 and 3.2~5.6, respectively. The enrich- ment was more significant in the 0.05~2 mm POM fractions than the >2 mm POM fractions. The enrichment of metals in the POM fractions was positively correlated with accumulation of the metals in the soils. The proportions of total heavy metals as organic matter-bound forms in the soils increased with increasing soil organic matter content. More than 40% of heavy metals in the surface soils were presented in organic matter bound forms.