[Concentrations, Sources, and Health Risks of PM_2.5 Carrier Metals in the Beijing Urban Area and Suburbs]

To explore the differences in pollution characteristics, sources, and health risks of PM_2.5 carrier metals in urban and suburban areas in Beijing, daily PM_2.5 samples were collected from Haidian and Daxing from June to November 2017 and the concentration of PM_2.5 and 13 constituent metals were analyzed. The sources of these 13 metal elements were analyzed by positive matrix factorization (PMF), and the health hazards of a subset of 9 metals were evaluated using health risk assessment. The results showed that the concentrations of PM_2.5 and 10 metal concentrations in the urban area including Cr, Co, Mn, and Ni were significantly different from those in suburban areas (P<0.05). The source analysis results show four key sources, although their relative contributions vary slightly between urban and rural areas. In urban areas, the main sources are motor vehicles (51.2%), coal burning (19.1%), dust (19.3%), and fuel oil (10.4%); in the suburbs, sources are motor vehicles (47.9%), coal burning (22.6%), dust (20.2%), and electroplating (9.3%). The results of the health risk assessment showed that all metal HQ values in the suburbs were less than 1, and there was no non-carcinogenic risk. Ni and Pb in urban areas, and Cd, Co, Ni, and Pb in suburban areas, do not present a cancer risk, while the R values of As (2.77×10^-5), Cd (2×10^-6), Co (1.76×10^-6), and Cr(Ⅵ) (7.88×10^-6) in urban areas and As (8.34×10^-6) and Cr(Ⅵ) (4.94×10^-6) in suburban areas present some risk of cancer.