苏南某些水稻土中Cu Pb Hg As的剖面分布及其影响因素

Profile Distribution of Total Cu,Pb,Hg,As in Some Paddy Soils from the Southern Jiangsu,China and the Influencing Factors

采用田间深度间隔采样法,分析了苏南6个处于不同环境影响下的水稻土剖面中Cu、Pb、As和Hg全量深度分布。结果表明,4种元素在土壤剖面中的移动能力均较差;在工业环境下田块的土壤中的Hg、Cu、Pb的表层富集和垂直分异较为明显,而在非工业环境下,重金属纵向分异不明显;个别田块存在较严重的As污染,耕层As达56.93 mg.kg-1,超出国家土壤环境质量二级标准;重金属元素在稻田土壤中表层富集系数大于果园利用下的旱地土壤。工业化进程中污染物的输入是影响供试土壤中重金属元素含量的主导因素,土壤的基本性质也在一定程度上影响了重金属的纵向迁移。重金属剖面分布特征可以在一定程度上反映水稻土的重金属污染积累程度。

Seven profiles （6 paddy soils plus 1 reference dry cropland soil） from southern Jiangsu were chosen to study the profile distribution of total contents of Cu, Pb, Hg and As under different environmental impacts. All the analyzed metals showed weak migration down to deep soil, possibly due to the impermeability of the plowpan layer in the paddy soils. However, remarkable vertical variation of Hg, Cu and Pb was found under industrial impact with sharper peak contents at the surface layer compared to that under non-industrial impact. Particularly, as high as 56.93 mg·kg^-1 of total As was found at surface with a sharp decreasing trend down profile in a paddy soil adjacent to a smelter factory in Yixing city, beyond the guideline limit of the State Soil Environmental Quality Category Ⅱ . Compared to the profile of a sandy dry cropland, the surface enrichment coefficients of the 4 elements were significantly higher in the paddy soils, partially attributed to the limited water percolation due to the plowpan and intense retention by clay and organic matter. The topsoil contents of the heavy metals and their vertical distributions in the paddy soils seemed to be primarily governed by the pollution input under industry development. On the other hand, soil physical and chemical properties could play a considerable role in their migration down to profile. The profile distribution can he indicative of soil heavy metal pollution in the paddy soils.