PM2.5samples were collected in a northern suburb of Nanjing during the winter of 2015. Water soluble ions and carbonaceous substances under different air quality levels were analyzed by an 850 professional IC-type ion chromatograph produced by Metrohm and a Model 2001A carbon analyzer. The results show that the average mass concentration of PM2.5, SO42-, NO3-, and NH4+ during heavy pollution days was 4.0, 6.4, 3.1, and 3.9 times higher than on clear days, respectively. Three main secondary ions were all in the form of (NH4)2SO4 and NH4NO3 on all days. Two kinds of acid pollution days were mainly affected by the flow source. The proportion of fixed sources on the heavy pollution days was greater than on the light/moderate pollution days. The highest mass concentrations of organic carbon (OC) and elemental carbon (EC) were 49.8 μg·m-3 and 10.3 μg·m-3, respectively. The average concentration of SOC on clear days was the lowest (4.28 μg·m-3). The proportion of secondary organic carbon (SOC) in the OC on clear days was more than on the other two pollution days (41.14%). Coal combustion and motor vehicle exhaust emissions were the main contributors to carbonaceous substances by abundances of carbonaceous components.
Keywords: Nanjing; PM2.5; element carbon; organic carbon; water-soluble ions.