Characterization of submicron aerosols at a suburban site in central China

We have characterized the chemical composition and sources of submicron aerosol (PM1) at a suburban site in Xinzhou in central China using an Aerosol Chemical Speciation Monitor from July 17 to September 5, 2014. The average (±1σ) PM1 concentration was 35.4 (±20.8) μg/m3 for the entire study period, indicating that Xinzhou was less polluted compared to the megacities in the North China Plain (NCP). The PM1 was mainly composed of organic aerosol and sulfate, on average accounting for 33.1% and 32.4%, respectively, followed by nitrate (14.4%) and ammonium (11.8%). Higher sulfate and lower nitrate contributions than those in megacities in the NCP elucidated an important emission source of coal combustion in central China. Three organic aerosol (OA) factors, i.e., hydrocarbon-like OA (HOA), semi-volatile oxygenated OA (SV-OOA) and low-volatility OOA (LV-OOA), were identified using positive matrix factorization. Secondary OA (=SV-OOA + LV-OOA) dominated OA, on average accounting for 82%, indicating that OA at the Xinzhou site was overall oxidized. We also observed relatively similar aerosol bulk composition and OA composition at low and high mass loading periods, and also from the different source areas, indicating that aerosol species were homogeneously distributed over a regional scale near the site for most of the time during this study. Slightly higher mass concentrations and sulfate contributions from the southern air masses were likely due to the transport from the polluted cities, such as Taiyuan to the south. In addition, the daily variation of PM1 in Xinzhou resembled that observed in Beijing, indicating that the wide-scale regional haze pollution often influences both the NCP and the central China.