北京道路尘土与土壤植物中重金属形态分析与评价

Speciation Analysis and Pollution Assessment of Heavy Metals in Road Dust,Soils and Plants in Beijing

以北京市航天桥道路尘土、附近道路土壤及绿化植物(大叶黄杨)叶片,玉渊潭公园土壤及绿化植物(大叶黄杨)叶片为研究对象,采用改进的BCR连续提取法、HCl-HNO3-HF-HClO4湿法消解和ICP-MS对Cr、Ni、Cu、Zn、As、Cd和Pb 7种重金属进行形态分析和含量测定。结果表明,样品中重金属Zn的总量最高,Cd的总量最低,细颗粒样品中的重金属含量除Cr和Cu均高于粗颗粒样品。7种重金属中Cr、Ni、Cu、Zn、As和Cd均以残渣态为主,Pb以可还原态和残渣态为主。样品的重金属总量相关性分析表明不同样品的重金属可能均来自交通污染源,总量与形态相关性分析表明总量与残渣态呈显著正相关性。内梅罗污染指数及风险评价法(RAC)结果均表明,道路尘土的重金属污染最为严重。植物对重金属Cd的富集效应最大(富集系数达0.962),路边植物对重金属的富集效应基本均大于公园植物。

With the modified BCR extraction, HCl-HNO3-HF-HClO4 digestion method and the analysis of ICP-MS, the concentration of chemical species of 7 heavy metals including Cr, Ni, Cu, Zn, As, Cd and Pb from road dust, roadside soil and plants leaves（Euonymus japonicus） around Hangtian Bridge, soil and plants leaves（Euonymus japonicus） in Yuyuantan Park were investigated. Results showed that all samples had the highest concentration of Zn and the lowest concentration of Cd. The concentration of heavy metals excluding Cr and Cu from fine particle samples was more than those from the coarse particle samples. Cr, Ni, Cu, Zn, As and Cd of 7 heavy metals mainly existed in residual species, while Pb mainly existed in Fe-Mn oxides and residual species. Correlation analysis of the total concentration indicated that the heavy metals in samples may nearly originate from traffic pollution. The correlation analysis of total concentration and various fractions showed that there was significant correlation between the total concentration and residual species. Evaluation result of Nemerow index method and risk assessment code （RAC） showed that the road dust was relatively severe. The enrichment effect of Cd in the plants samples was the biggest with enrichment coefficient as 0.962, and roadside plants sample had the bigger enrichment effect than that of the plants sample in park.