Polycyclic aromatic compounds (PAHs, oxygenated PAHs, nitrated PAHs, and azaarenes) in air from four climate zones of China: Occurrence, gas/particle partitioning, and health risks

Polycyclic aromatic compounds (PACs) such as polycyclic aromatic hydrocarbons (PAHs) and their derivatives [oxygenated PAHs (OPAHs), nitrated PAHs (NPAHs), and azaarenes (AZAs)] are toxic and ubiquitous air pollutants. In this study, the concentrations of these PACs were determined in air obtained in spring and autumn of 2012 from urban and rural areas of the Tibetan Plateau, temperate, subtropical, and tropical climate zones in China. Average concentrations (gaseous + particulate) of Sigma 29PAHs, Sigma 15OPAHs, Sigma 11NPAHs, and Sigma 4AZAs were 928 +/- 658, 54 +/- 45, 5.3 +/- 4.4, 14 +/- 11 ngm(-3) and 995 +/- 635, 67 +/- 38, 8.4 +/- 6.1, 24 +/- 16 ngm-3 in spring and autumn, respectively. Various C fractions and latitude correlated significantly with the concentrations and ratios of PACs. The slopes of the regression of gas-particle partition coefficients (K-p) of PACs on their subcooled liquid vapor pressures (P-L(0)), indicated both adsorption and absorption to total suspended particles (TSP) for PAHs, OPAHs, and NPAHs in the four studied climatic zones. This result was further supported by comparing the fractions of PACs in TSP calculated fromfield data with those predicted by the Junge-Pankow adsorption and KOA absorption models. The concentration ratios of most OPAHs or NPAHs to their parent PAHs and of benzo[e] pyrene/benzo[a]pyrenewere higher in autumn than in spring and increasedwith remoteness frompoint sources. This suggests enhanced secondary formation of PAH derivatives due to the elevated photochemical activity in autumn and longer ageing of air and associated transformation of PACs during their long-distance transport from source regions (urban sites) to rural sites. Lifetime lung cancer risk estimated from PACs ranged from 0.8 +/- 0.6 to 3.1 +/- 1.0 (x10(-3)), exceeding the value (10(-5)) recommended by the WHO. Gaseous PACs contributed substantially to the estimated cancer risks and their contributions increased with decreasing latitude in China. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the concentrations of PACs in different climate regions in China during spring and autumn of 2012, finding significant seasonal and geographical variations in the concentrations of PAHs, OPAHs, NPAHs, and AZAs in both gaseous and particulate forms. Across the four climate zones, PACs were primarily adsorbed and absorbed into total suspended particles. In autumn, there was an increase in the concentration of PAH derivatives with increasing distance from the source region.