成都市郊区域农田中土壤镉形态研究

农田土壤是镉生态循环的重要介质，所含镉对人体健康的危害不可忽视。镉在土壤中以多种形态存在．可划分为水溶态、离子交换态，碳酸盐结合态、Fe及Mn氧化物结合态，有机结合态、残留态。不同存在形态镉的生物有效性各不相同，因而对环境和人体健康造成的影响也存在差异。水溶态镉，离子交换态镉具有很高的生物有效性。碳酸盐结合态镉在弱酸性条件下生物有效性较高，Fe及Mn氧化物结合态镉、有机结合态镉、残留态镉生物有效性很低。本研究采用连续提取法和原子吸收法对成都市某郊区基本农田的35份土壤样品中各形态镉进行了提取和测定。结果表明。成都市某郊区农田土壤的镉污染状况较为严重，37．14％的土壤含高生物有效性的水溶态镉或离子交换态镉。土壤中水溶态镉、离子交换态镉的存在与环境污染有密切联系。Fe及Mn氧化物结合态镉，有机结合态镉、残留态镉的存在受耕作因素和成土母质影响较大。

A Study on Cadmium Forms in Farmland Soil in the Suburb of Chengdu

Farmland soil is an important medium of the ecological circulation of cadmium, which does harm to human health that cannot be neglected. Cadmium exists in several forms in soil as classified into WS, Exc, Carb, FeMnOx, O.M, Res. As different forms have different biological validity, their influences to the environment and human health are also different. Cadmium in WS or Exc form has very high biological validity, and so has in Carb form in the condition of weak acid whilst that in O.M or Res form has fairly low biological validity. A sequential extraction technique and atomic absorption spectrometry were used in the study to extract and determine the cadmium forms in 35 farmland soil samples in the suburb of Chengdu. The results indicated that farmland soil in the suburb of Chengdu has seriously been contaminated, and 37.14% of the soil samples contained cadmium in WS or Exc form with very high biological validity. The existence of cadmium in WS or Exc form in soil is closely related to the environment pollution whilst that of cadmium in FeMnOx, O.M or Res form is more influenced by farming and parent rocks.