Concentration and atmospheric transport of PM2.5-bound polycyclic aromatic hydrocarbons at Mount Tai, China

Atmospheric PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) pose a major threat to human health. At present, studies on PAHs in the atmosphere have mostly focused on their concentration levels and source apportionment, whereas studies on the vertical transport of PAHs in the atmosphere are limited. However, the vertical transport of PAHs is important for their diffusion near the ground and their long-range transport at higher altitude. In this study, PM2.5 samples were collected simultaneously at the summit and foot of Mount Tai (MTsummit and MTfoot, respectively) from May to June 2017, and the concentrations of 18 PAHs in the samples were determined. The total concentration of PAHs at MTsummit was 2.406 ngm(-3), which waswell below the pollution levels of domestic cities, whereas that at MTfoot was as high as 9.068 ng m(-3), which was within the range of pollution levels in domestic cities. The total carcinogenic risk for both MTsummit and MTfoot was within the potential risk range. Given the source of PAHs and the diurnal variation of the planetary boundary layer, the PAHs showed opposite diurnal trends at MTsummit and MTfoot. Vertical transport was an important source of daytime PAHs at MTsummit, and the vertical transport efficiency of PAHs decreased with an increasing ring number; this may be due to the combined effects of gas-particle partitioning and chemical reactions. Furthermore, PAHs originating in the surrounding high-emission provinces can affect the Mount Tai area via atmospheric trans-regional transport, and the BaP/BeP ratio is a useful indicator of the transport distance of PAHs. (C) 2021 Elsevier B.V. All rights reserved.