应用化学提取法评价大气颗粒物中重金属的生物有效性

Application of chemical leaching tests to evaluate the bioavailability of heavy metals in atmospheric particles

以广州市楼顶降尘为研究对象，在分析其粒度分布和重金属总量的基础上，采用单一化学提取法（DWLP、TCLP）和多级化学提取法（SEP）研究了大气颗粒物中4种重金属元素的生物有效性。结果表明：样品中96％以上颗粒小于100μm，其中10μm和2．5μm以下颗粒分别占33％和11％。大气颗粒物中重金属含量很高，Cu、Pb、Zn和Cd的平均含量分别为362．43、1033．81、830．32和5．80mg／kg，是广东省环境土壤背景值的17～64倍。单一提取法中，TCLP的提取效率明显高于DWLP，表明pH值是影响大气颗粒物中重金属释放的主要因素。SEP法结果显示，Zn和Cd的生物可利用态比例远高于Cu和Pb。经DWLP和TCLP法提取后，颗粒物中重金属的总含量有不同程度的降低，生物可利用态所占比例明显增加。通过综合分析，发现SEP此其他两种方法更适用于评价大气颗粒物中重金属的生物有效性。

Panicle samples used in this study were collected from a building roof of Guangzhou and analyzed for size distribution and total concentration of heavy metals. Three chemical leaching tests, including DWLP, TCLP and SEP, were employed to investigate the bioavailability of heavy metals in the particles. Results showed that, the percentage of particles less than 100μm was 96%, while that less than 10μm and 2.5μm was 33% and 11% , respectively. The contents of heavy metals in particles were very high. The total concentration of Cu, Pb, Zn and Cd was 362.43, 1 033. 81, 830. 32 and 5. 80 mg/kg respectively, which were 17 - 62 times higher than the value of the environmental soil background of Guangdong Province. Results of single chemical leaching procedures indicated that heavy metal concentrations in the TCLP leachate were significantly higher than that of the DWLP. This is mainly due to the pH differences between the applied extraction fluids. According to the data of the SEP, the bioavailability of Zn and Cd in the particles is much higher than that of Cu and Pb. The contents of heavy metals in particles were decreased in some degrees after DWLP and TCLP leaching tests, While the relative percentages of bioavailable part were significantly increased. Comparing results obtained from above three methods, it is found that the SEP method is more suitable to evaluate the bioavailability of heavy metals in atmospheric particles.