城乡交错区土壤中镉的赋存形态及其生物有效性研究

采用连续形态分析方法研究了重庆市城乡交错区土壤中Cd的形态分布及其与莴笋吸收Cd量的关系.结果表明,研究区土壤和莴笋中Cd污染严重,土壤各形态Cd总体分布特征为:残渣态Cd＞有机质结合态Cd＞离子交换态Cd＞碳酸盐结合态Cd＞铁锰氧化物结合态Cd＞水溶态Cd,其中活性较强的交换态Cd(包括水溶态Cd和离子交换态Cd)比重较大.Cd在土壤中的分布与土壤中的物理性粘粒及粉粒含量密切相关.而在土壤各形态Cd中,离子交换态Cd具有较高的生物有效性.研究区土壤和蔬菜中Cd污染已经较严重,建议加强城乡交错区的环境综合管理.

Modes of occurrence and bioavailability of Cd in soils of the urban-rural integration area

Characteristics of chemical forms of Cd in soils of the Urban-Rural-Integration-Area (URIA) in Chongqing were studied by using the sequential extraction method. Relations between the forms of Cd and the extent of metal accumulation in the asparagus lettuce were analyzed. The results show that the soils and the asparagus lettuce in the study area have been heavily polluted, and that different forms of Cd in soils are distributed in order of RES ＞ ORG ＞ EXC ＞ CAB ＞ OXI＞ WS, with the active exchange state Cd accounting for a relatively large proportion. The major factors affecting the chemical forms of Cd in soils are physical clay and powder content. Regression analysis shows that Cd in the EXC form has relatively high bioavailability. The Cd pollution in soils and vegetables has become rather serious in the study area,and thus this paper suggests the strengthening of the environmental management in the URIA.