New characteristics of submicron aerosols and factor analysis of combined organic and inorganic aerosol mass spectra during winter in Beijing

Abstract

© Author(s) 2015. In recent years, an increasing amount of attention has been paid to heavy haze pollution in Beijing, China. In addition to Beijing's population of approximately 20 million and its 5 million vehicles, nearby cities and provinces are host to hundreds of heavily polluting industries. In this study, a comparison between observations in January 2013 and January 2014 showed that non-refractory PM1 (NR-PM1) pollution was weaker in January 2014, which was primarily caused by variations in meteorological conditions. For the first time, positive matrix factorization (PMF) was applied to the merged high-resolution mass spectra of organic and inorganic aerosols from aerosol mass spectrometer measurements in Beijing, and the sources and evolution of NR-PM1 in January 2014 were investigated. The two factors, NO 3 -OA1 and NO 3 -OA2, were primarily composed of ammonium nitrate, and each showed a different degree of oxidation and diurnal variation. The organic fraction of SO 4 -OA showed the highest degree of oxidation of all PMF factors. The hydrocarbon-like organic aerosol (OA) and cooking OA factors contained negligible amounts of inorganic species. The coal combust ion OA factor contained a high contribution from chloride in its mass spectrum. The NR-PM1 composition showed significant variations in January 2014, in which the contribution of nitrate clearly increased during heavy pollution events. The most effective way to control fine particle pollution in Beijing is through joint prevention and control measures at the regional level, rather than a focus on an individual city, especially for severe haze events.