贵阳市土壤中镉的赋存形态及其环境效应

CHEMICAL SPECIATION OF CADMIUM IN SOIL OF GUIYANG CITY AND ITS ENVIRONMENTAL EFFECTS

对贵阳市镉异常区土壤镉的化学形态进行分析和研究,结合农作物、水体污染现状和地方病调查,评价贵阳市土壤高背景值镉对周围环境及人体健康的影响。研究结果表明:贵阳市土壤镉的赋存形态以离子交换态、铁锰氧化物结合态、残渣态为主,弱有机结合态和碳酸盐结合态次之,强有机结合态较低,水溶态镉最低;垂向剖面上,土壤镉含量随土壤深度的增加而降低,镉在土壤表层更为富集,深层土壤中镉的形态分布与表层土壤类似;土壤异常区的水体未受到镉的污染,但稻谷、辣椒、烟草等农作物已出现镉超标现象,且部分地区出现了因镉引起的地方病症状。贵阳市土壤镉背景值高,且镉的生物有效性较强,已对农作物、人畜健康造成了一定危害,潜在威胁较大。

In order to evaluate environmental effects of the chemical speeiation of cadmium, the authors studied soils with high content of cadmium in Guiyang, and investigated the crop, water pollution and endermic diseases. Some conclusions have been reached： Cad- mium is existent mainly in exchangeable fraction, residual phase, and Fe-Mn oxide phase, subordinately in weak organic combinational state and carbonate phase, and very lowly in water soluble phase. In vertical profile of soil, cadmium content decreases with increasing soil depth, cadmium is more concentrated in surface soil, and the distribution of chemical speciation of cadmium in deep soil is similar to that of surface soil. The water has not been polluted by cadmium in abnormal areas, and cadmium in such crops as rice, pepper and tobacco has exceed the state standard. In addition, local disease symptoms induced by cadmium has appeared in some areas. There- fore, the crops and human health are adversely affected by the high soil background values of cadmium in Guiyang, and the potential threat is serious.