Variation tendency of pollution characterization, sources, and health risks of PM2.5-bound polycyclic aromatic hydrocarbons in an emerging megacity in China: Based on three-year data

Abstract

In this study, a total of 180 PM2.5 samples were collected from December 3, 2013 to October 20, 2016 in an urban area in Zhengzhou, China, and 16 polycyclic aromatic hydrocarbons (PAHs) in PM2.5 were analyzed. Diagnostic ratio and positive matrix factorization (PMF) were used for annual PAH source identification, and health risks and source regions of PM2.5-bound PAHs were also investigated. Results showed high pollution levels of PM2.5, in which all annual average concentrations substantially exceeded the Chinese standard. Although the PAH concentrations exhibited an evident decreasing trend, PAH pollution remained serious, especially in winter. Combustion, particularly coal combustion and vehicle emission, which were relative sources of 4–5-ring PAHs, played important roles in PAH pollution associated with PM2.5 by diagnostic ratios. PMF results showed that coal combustion had the highest contribution to PM2.5-bound PAHs at 39.6%, 39.6%, and 42.6% and traffic at 29.3%, 25.4%, and 27.9% in 2014–2016, respectively. Biomass burning and coking plants were also important sources of PAHs in PM2.5, with an average contribution of 16.4% ± 1.3% and 15.4% ± 3.5%, respectively. The surrounding region in Henan Province was the key potential source area for PM2.5. However, the northwest and adjoining regions of Zhengzhou were the vital potential sources for PAHs during the entire study period. The concentration levels of benzo[a]pyrene (BaP), ∑16PAHsTEQ, and carcinogenic PAHs remained high, especially for BaP, which had an annual concentration (1.9–5.5 ng/m3) that was considerably higher than the Chinese standard. Carcinogenic risks existed in the order of ingestion > dermal absorption > inhalation and adults > children > seniors > adolescents (except for naphthalene). The risk for females was slightly high, and no remarkable non-carcinogenic risk from PAHs were found.