基于化学形态分析的城市道路灰尘重金属健康风险评价与人为来源解析

Health Risk Assessment and Anthropogenic Source Identification of Heavy Metals in Urban Road Dusts Based on Chemical Fraction Analysis

环境中重金属的生物可利用性与其化学形态分布密切相关。借助化学形态分析可以更好地评价道路灰尘中各重金属的人体健康风险,但目前已有的研究主要集中在重金属的总量分析。通过采集临沂市城区主要街道灰尘样品,基于改进的BCR形态分析开展了Pb、Cd、Cu、Zn、Cr、Ni 6种重金属的健康风险评价与人为来源解析研究,以期为当地有关部门采取更加合理有效的污染防护措施提供理论支持。结果表明,临沂城区道路灰尘中Pb、Cd、Cu、Zn、Cr、Ni 6种重金属呈现出明显的累积特征,其平均含量分别是山东省土壤背景值的6.78倍、55.12倍、7.91倍、6.09倍、1.32倍、2.78倍。与国内其它城市相比,临沂市道路灰尘中重金属含量水平整体偏高。根据BCR形态分析结果,残渣态仍是临沂城区道路灰尘中各重金属的主要赋存形态(64.52%～85.21%),表明它们具有较低的生物可利用性。各重金属的生物可利用性顺序为Zn>Cu>Pb>Cd>Ni>Cr。应用人体暴露模型进行分析,发现临沂市道路灰尘中生物可利用态重金属的非致癌与致癌风险水平整体较低,但儿童的非致癌暴露量明显高于成人,手-口摄入是最主要的暴露途径。相关性分析和主成分分析表明,临沂城区道路灰尘中重金属有着不同的人为来源,其中,汽车轮胎磨损与燃油泄漏等交通活动是Cd、Cu、Zn 3种重金属的主要人为来源,而人为Pb、Cr、Ni污染主要来自居民生活燃煤排放。

The bioavailability of heavy metals is closely related with their chemical fractions,chemical fractionation can therefore help to better assess the human health risk posed by heavy metals in road dust.However,previous studies were still focused on the analysis of total metal concentration.In this paper,a total of 36 road dust samples were collected from the urban area of Linyi city,China.The health risk assessment and anthropogenic source identification were carried out for six heavy metals(Pb,Cd,Cu,Zn,Cr and Ni)in the road dusts,according to a modified BCR chemical fractionation procedure.Results showed that Pb,Cd,Cu,Zn,Cr and Ni has accumulated in the road dusts,with the average contents of 6.78,55.12,7.91,6.09,1.32 and 2.78 times higher than the soil background values in Shandong Province,respectively.When compared to other cities in China,Linyi city generally had higher concentrations of heavy metals in road dust.However,the residual fraction was still the predominant chemical fraction for all heavy metals(64.52%-85.21%),which implied a low bioavailability.The bioavailability decreased in the order of Zn,Cu,Pb,Cd,Ni and Cr.By applying a human exposure model,it was found that the bioavailable heavy metals generally posed low non-carcinogenic and carcinogenic risks in the road dusts of Linyi city.By comparison,the children suffered from more non-carcinogenic exposure dose than the adults,and the oral ingestion was the primary exposure way.Correlation analysis suggested that heavy metals in the road dusts of Linyi city had different anthropogenic sources,which was in agreement with the results of principal component analysis.Traffic activities including tyre wearing and fuel leakage were the major anthropogenic sources of Cd,Cu and Zn,while the anthropogenic Pb,Cr,Ni mainly came from coal combustion.