Water–soluble inorganic ions and PAHs of summer PM10 samples in Mongolia during 2005–2010

Aerosol samples were collected in the atmosphere of Mongolia (Sainshand, Baruun–Urt, Ulaanbaatar, and Sukhbaatar) during the summer periods of 2005–2010. The samples were analyzed for water–soluble inorganic ions, elemental composition of atmospheric aerosol and polycyclic aromatic hydrocarbons. We found that the local emissions play an important role in the formation of the aerosol composition in Ulaanbaatar and Sukhbaatar. Polluting anthropogenic components arrive in Mongolia primarily from the southern and southeastern directions, originating in China. This observation is supported by simulations of the air mass pathways with the HYSPLIT model. The major ions in the aerosol particles in Sainshand and Baruun–Urt are SO42-, NO3-, and NH4+ and, in certain cases, HCO3- and Ca2+ ions as well. The concentration of water-soluble ions in particulate matter with diameters less than 10 μm (PM10) at these points in the absence of transport from the southern direction does not exceed 10 μg m-3. The concentration of ions in PM10 aerosols in Sainshand and Baruun–Urt increases to 20.3 μg m-3 under the influence of the southern transport pathways, a level comparable to the concentration of aerosols in the industrial cities of Mongolia, such as Ulaanbaatar. In Ulaanbaatar and Sukhbaatar the SO42-, NO3-, HCO3-, Ca2+, and NH4+ ions are the main components of PM10. This study was the first to investigate the polycyclic aromatic hydrocarbon (PAH) content of atmospheric aerosols from the Mongolian Gobi. The results showed that all aerosol samples were dominated by PAHs with five or six benzene rings, and the total concentration of PAHs in the aerosol particles was less than 3 ng m-3. The concentration of PAHs in the Mongolian Gobi is several times higher than that in the air near the Baikal Lake due to the transport of anthropogenic emissions from China to Mongolia.