[Ecological and Health Risks of Trace Heavy Metals in Atmospheric PM_2.5 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.