Pollution and transport of atmospheric PAHs in Xinjiang: Observation at a high-altitude background site combined with numerical simulation

Abstract

As an essential energy production base in China, the pollution of PAHs in Xinjiang cannot be ignored. However, this region has limited studies on the overall distribution and transport characteristics of polycyclic aromatic hydrocarbons (PAHs). This study used a combination of high-altitude background site (MTtian) observations and Community Multiscale Air Quality simulations for systematic investigation. The simulation results revealed that the distribution of PAHs in Xinjiang was high in the north and low in the south, primarily associated with emissions. Moreover, the observed concentration of PAHs in the MTtian was 1.37 ng/m3, which lies between the clean and polluted background sites, emphasizing the importance of regional anthropogenic emissions. The observed PAH concentrations at MTtian was 32.2% higher when the air mass was from Urumqi than those at other places. This is related to mountain-valley winds, as shown by the simulations. In addition, the transport of high-altitude PAHs in Xinjiang is primarily affected by westerly winds. This mechanism can explain the highly simulated PAHs at high altitudes in the Tarim Basin. The PAHs emitted from Xinjiang were transported eastward downstream, with Mongolia being the most affected region, contributing to 7.33% of the total PAHs.