PM2.5 pollution episode and its contributors from 2011 to 2013 in urban Shanghai, China

Abstract

Abstract Shanghai has suffered from severe fine particle (PM 2.5 ) pollution in recent years. The characterization and formation mechanism of PM 2.5 pollution episodes were investigated in the present study based on 3-year on-line measurements of PM 2.5 chemical compositions with the temporal resolution of 1 h from 2011 to 2013 in Shanghai. Pollution episodes with PM 2.5 mass higher than 75 μg/m 3 occurred ∼1400 h annually, which inserted the annual extra PM 2.5 mass of 14 μg/m 3 into the level of 33 μg/m 3 without pollution episodes taken into account. Three kinds of typical episodes were identified as biomass burning events, suspended dust events, and fireworks events, which extra contributed ∼1.5 μg/m 3 relative to PM 2.5 mass of clean periods. Most of pollution episodes were attributed to multiple and complex mechanisms, characterized by high contribution of the secondary inorganic components (e.g. nitrate, sulfate and ammonium) and carbonaceous matters, which dominated the monthly variations of PM 2.5 mass. During the complex episodes, the increasing contribution of nitrate mass concentration to PM 2.5 burden was observed. The present study highlighted the necessity to pay more attention to the secondary pollution. The reduction of precursor gases emissions was essential to mediate the severe PM 2.5 pollution in Shanghai megacity.