山西省武乡县城大气PM2.5痕量重金属的生态和健康风险分析

为了解山西省武乡县城大气PM_(2.5)污染特征及PM_(2.5)中痕量重金属的生态和健康风险,在分析县城环境空气质量状况的基础上,分别于秋季(2014-10-22~2014-11-19)和冬季(2015-01-12~2015-02-13)在武乡县环境保护局楼顶用中流量采样器采集大气PM_(2.5)样品,每天换膜一次,利用称重法计算PM_(2.5)浓度,运用电感耦合等离子体原子发射光谱仪(ICP-AES)测定样品中As、Cd、Cr、Cu、Ni、Pb、Zn 7种元素含量,运用地累积指数法、生态风险指数法、相关性分析和主成分分析、美国环保署暴露模型等表征痕量重金属的污染程度、来源、潜在的生态和健康风险等.结果表明,冬季大气PM_(2.5)浓度是秋季的3倍左右,有65%的天数超过国家环境空气质量二级标准(GB 3095-2012);PM_(2.5)中痕量重金属来源主要包括燃煤和交通等人为源,贡献率分别为58.38%和18.73%,所测重金属浓度顺序为CuZnPbCrAsNiCd,其中Cd、Cu的生态风险指数、Cr的非致癌和致癌暴露风险大于其它金属.冬季燃煤增加和大气扩散条件差是武乡县城大气PM_(2.5)浓度超标以及造成痕量重金属生态和健康风险增大的主要原因.

Ecological and Health Risks of Trace Heavy Metals in Atmospheric PM2.5 Collected in Wuxiang Town, Shanxi Province

The pollution of atmospheric PM_2.5 and ambient air quality were investigated in Wuxiang Town, Shanxi Province, China, and the ecological and health risks of the trace heavy metals in PM_2.5 were analyzed. The PM_2.5 samples were collected every day using a medium-volume PM_2.5 sampler in autumn (from Oct. 22 to Nov. 19, 2014) and in winter (from Jan. 12 to Feb. 13, 2015) on the roof of a building at the Wuxiang Environmental Protection Agency (EPA). The mass concentrations of PM_2.5 were determined gravimetrically, and the contents of seven trace heavy metals (i. e., As, Cd, Cr, Cu, Ni, Pb, and Zn) in PM_2.5 were obtained using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The pollution extent, sources, and potential ecological and health risks of the trace heavy metals in PM_2.5 were identified and assessed using the geo-accumulation index, ecological risk index, a correlation and principle component analysis, and the exposure risk models of US EPA. Results showed that the average concentration of PM_2.5 in winter, approximately three times higher than that in autumn, exceeded the national secondary standard of ambient air quality (GB 3095-2012) on 65% of the sampling days. The heavy metals in PM_2.5 mainly originated from anthropogenic activities, with contributions of 58.38% and 18.73% from coal combustion and vehicular emission, respectively. In general, the levels of the heavy metals in PM_2.5 followed the order of Cu > Zn > Pb > Cr > As > Ni > Cd, with higher ecological risks from Cd and Cu and higher non-carcinogenic and carcinogenic risks from Cr compared with other metals. It is suggested that greater coal combustion in winter under the adverse geographical conditions for air diffusion in Wuxiang Town were responsible for the increased atmospheric PM_2.5 concentration and their ecological and health risks in heavy metals.