Characteristics and Health Risk Assessment of PM2.5-Bound PAHs during Heavy Air Pollution Episodes in Winter in Urban Area of Beijing, China

Abstract

PM_2.5 level has decreased significantly in Beijing in recent years due to the strict air quality control measures taken in Jingjinji Region and the surrounding areas. However, the variation characteristics of the concentrations of PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) in Beijing in recent years are still not so clear. In order to understand the pollution status of PM_2.5-bound PAHs in Beijing, fifteen PAHs were measured in a typical urban area of Beijing from 1 March to 20 March 2018. The average mass concentration of the 15 PAHs was 21 ng/m³ and higher in the nighttime than that in the daytime. The proportion of 4-ring PAHs in 15 PAHs was highest (43%), while 6-ring PAHs was lowest (10%). The levels of PAHs were higher during heavy pollution episodes than those in non-heavy pollution episodes, and the proportions of 5- and 6-ring PAHs were increased during a heavy pollution episode. PAHs posed obvious carcinogenic risks to the exposed populations, and the risk was higher during heavy pollution episodes than the average value of the whole monitoring period. The main sources of PAHs were traffic emissions and coal/biomass burning. Air masses from the south-southeast had a great influence on the PM_2.5 levels during a heavy pollution episode. It is recommended that not only the PM_2.5 levels but also the PAHs levels bounded in PM_2.5 should be controlled to protect human health in Beijing.