Components and optical properties of submicron aerosol during the lasting haze period in Nanjing

A lasting haze pollution event occurred in the Central and East China in January 2013. In this study, Aerodyne Aerosol Chemical Speciation Monitor (ACSM), Photoacoustic Extinctiometer (PAX), and Aethalometer were deployed for real-time and lasting monitoring of non-refractory submicron aerosol (NR-PM 1 ) components (i.e. organics, sulfate, nitrate, ammonium, and chloride), atmospheric aerosol extinction properties, and black carbon (BC) in Nanjing, respectively. During the measuring period, the contribution of PM 1 (NR-PM 1 +BC) species, i.e., organics, nitrate, sulfate, ammonium, chloride, and BC were 32.3%, 26.0%, 17.9%, 13.2%, 2.8%, and 7.8%, respectively. Positive matrix factorization (PMF) analysis indicates that hydrocarbon-like (HOA), semi-volatile oxygenated organic aerosol (SV-OOA), low-volatile oxygenated organic aerosol (LV-OOA) were the major sources for PM 1 . HOA, SV-OOA, and LV-OOA on average accounted for 27.4%, 32.2%, and 40.4% of organic aerosol, respectively, which means that PM 1 consisted mostly of the secondary species. Because of local cooking and traffic emissions, HOA loading dynamically increased at the nighttime, which resulted in a significant variation of organics. Generally, the mass concentrations, the mass fractions of secondary components (i.e. nitrate, sulfate, SV-OOA, and LV-OOA), as well as aerosol signal scattering albedo increased with increasing relative humidity (RH), respectively, implying that the increase in RH was beneficial to the continual formation of secondary aerosol. Furthermore, atmospheric visibility decreased with the increasing of RH and secondary species contents, indicating that there is a synergistic effect between the RH and the secondary species of PM 1 on the atmospheric visibility during the haze period.