成都经济生态区大气降尘中镉赋存形态的研究

A Research for Existent Forms of Cadmium in Dustfall in Chengdu Region

重金属的生物毒性不仅与其总量有关,更大程度上由其形态分布所决定,不同的形态产生不同的环境效应。为了解城市大气降尘中的镉污染,采用 Tessier 连续提取法对成都经济生态区内不同区域的24个大气降尘样中镉的赋存形态进行了研究。结果表明,大气降尘中的镉主要以残留态存在;各形态镉在总镉中所占的平均百分比含量的排列顺序依次为:残留态〉碳酸盐结合态〉交换态〉铁锰结合态〉有机结合态(78.907%,8.917%、6.420%、3.419%、2.365%);交换态镉、碳酸盐结合态镉具有较高生物有效性,铁锰氧化物结合态、有机结合态、残留态这3种形态镉的生物有效性很低。分析得出:汽油和煤的燃烧,以及工厂排放镉能加大城市大气降尘的镉污染。

The existent forms of cadmium in 24 dustfall samples from different sections of Chengdu Economic Region have been studied by Tessier extraction method. Results indicated that the average contents of various cadmium forms existing in the dustfall could be arranged in descending order as residual, bound to carbonates, exchangeable fraction, bound to Fe-Mn oxides, and bound to organic matters in terms of percentage 78.907%, 8.917%, 6.420%, 3.419% and 2.365% respectively. The cadmium in exchangeable fraction and bound to carbonates had much higher bioactivity than in the rest three forms. According to the observed data, petrol and coal combustion as well as industrial emission were found to more contribute to cadmium pollution in the urban dustfall.