Seasonal variation, sources and health risk assessment of polycyclic aromatic hydrocarbons in different particle fractions of PM(2.5 )in Beijing, China

The ratio of SO2/NO2 together with PM2.5/CO was applied to explain the source of particulate matters (PM) pollution in Beijing. Polycyclic aromatic hydrocarbons (PAHs) bounded with ultrafine particles were investigated as well. A total of 188 graded PM in four-stage size segregated aerosol particles were collected and analyzed by GC-MS in 2016 to investigate the sources and distribution patterns of PAHs in metropolis-Beijing. A significant seasonal variation of 16 PAHs in PM2.5 around in Beijing was observed with 32.93 +/- 15.19 ng m(-3), 17.77 +/- 8.08 ng m(-3), 31.61 +/- 12.67 ng m(-3) and 78.06 +/- 40.97 ng m(-3) in spring, summer, autumn and winter, respectively. The ratio of SO2/NO2 demonstrated that vehicle emissions significantly contributed to air pollution. On the contrary, the lower ratio of PM2.5/CO showed high direct discharge from combustion. Seasonal distribution patterns of PM0.2/PM2.5 suggested that abundant secondary aerosols were produced in the autumn and winter. The spread of pollutants was not significant in winter. Both the combustion of fuel and coal were the primary sources of PM2.5-bound PAHs. A health risk assessment was represented by benzo [a] pyrene equivalent (BaPeq) indicating potential cancer risk in Beijing. Furthermore, the lifetime excess cancer risk (ECR) was 3.00 x 10(-4), which was higher than the guidelines of USEPA and European Commission, indicating high carcinogenic risk of PM2.5 in Beijing. Therefore, more strictly control measures should be taken to reduce PAHs emissions from coal and vehicle.