Composition and sources of PM2.5 around the heating periods of 2013 and 2014 in Beijing: Implications for efficient mitigation measures

The diurnal variations of the water soluble organic and inorganic components as well as six selected metals in PM2.5 around the heating periods of 2013 and 2014 in Beijing were analyzed in this study to investigate the contributions of secondary aerosols and primary pollutants to PM2.5 and the effects of domestic heating and mitigation measures. The before-heating sampling period in 2014 (from Nov. 1st to Nov. 15th) was characterized with reinforced short-term mitigation measures for the 2014 Asia-Pacific Economic Cooperation (APEC) meeting. As a result, the average mass concentrations of PM2.5 and most of the measured species except for Cu, Al, and Ca2+ were greatly reduced during the APEC meeting period. The domestic heating activity alone resulted in a 17.7% increase of PM2.5 in 2013, exerting lesser effects on the increase of PM2.5 than before. Water soluble organic carbon was the most abundant water soluble species in PM2.5, followed by NO3−, SO42−, and NH4+. According to the PMF model calculation, secondary aerosols, coal combustion, biomass/waste burning, traffic related pollution, long-range transport, and fugitive soil and sand dust were identified as the main sources of PM2.5 in Beijing, among which secondary formation of aerosols was the dominant source of PM2.5 during the non-APEC period while biomass/waste burning dominated during the APEC period. As a timely feedback on the effects of the mitigation measures adopted by the government, the results of this study provide knowledge necessary for a sustainable urban management.