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Continuous measurements of ambient aerosols were performed with a single-particle aerosol mass spectrometer in Nanjing during all four seasons of 2015. Ambient particles were clustered into 11 classes, which included elemental carbon (EC) mainly with sulfate (EC-S); EC with nitrate and sulfate (EC-SN); EC with obvious organic signals (ECOC); organic carbon (OC); biomass/biofuel burning particles (Biomass); Ammonium; particles with obvious Na, K (NaK) and sulfate (NaK-S), NaK with nitrate and sulfate (NaK-SN); iron-containing particles (Fe-rich); miscellaneous metal-containing particles (MiscsMetals) and Dust. Seasonal local sources, dominated air masses and distinct atmospheric processes all affected the concentrations of various particles and caused different diurnal changes. EC-SN during summer slowly increased in the afternoon and NaK-SN had a peak at noon during winter. Differences in size distribution of each particle type between seasons were discussed. All types of particles showed unimodal number size distributions, their peak radius ranked as follows: fall < spring < summer ≤ winter. OC during fall had higher number fractions of between 0.2 and 0.5 μm (>20%) as a result from the decrease in temperature and increase in relative humidity (RH). The distributions of ECOC varied with seasons and were obviously influenced by EC and OC particles. Mixing states showed seasonal variations. In general, the fractions of particles mixed with secondary species were the highest/lowest in winter/fall. The effects of meteorological conditions on particles were investigated. With the increase of RH, the fractions of EC increased, and most particles mixed with more NH 4 + and less C 2 H 3 O + . Characteristics of precipitation, such as duration and total rainfall amount, influenced particles. Enhanced secondary organic/inorganic species were found in particles during long-/short-term precipitation with intensities <1 mm. Less NH 4 + , C 2 H 3 O + and HSO 4 − were found during precipitation compared with non-precipitation days. [ABSTRACT FROM AUTHOR]

The mixing state of aerosol particles were investigated using a single particle aerosol mass spectrometer (SPAMS) during a regional fog-haze episode in the Yangtze River Delta (YRD) on 16–28 Dec., 2015. The aerosols were analyzed and clustered into 12 classes: aged elemental carbon (Aged-EC), internally mixed organics and elemental carbon (ECOC), organic carbon (OC), Biomass, Amine, Ammonium, Na-K, V-rich, Pb-rich, Cu-rich, Fe-rich and Dust. Results showed that particles in short-term rainfalls mixed with more nitrate and oxidized organics, while they mixed with more ammonium and sulfate in long-term rainfall. Due to anthropogenic activities, stronger winds and solar radiation, the particle counts increased and the size ranges of particles broadened in haze. Carbonaceous particles and Na-K mixed with enhanced secondary species during haze, and obviously were more acidic, especially for the ones with a size range of 0.6–1.2 μm. For local and long-range transported pollution, OC had distinct size distributions while the changes of ECOC were uniform. The secondary formation of ECOC contributed significantly in local pollution and affected much smaller particles (as small as 0.5 μm) in long-range transported pollution. And long-range transported pollution was more helpful for the growth of OC. Particles mixed with more chloride and nitrate/sulfate in local/long-range transported pollution. [ABSTRACT FROM AUTHOR]