![]() In addition, the ρ eff of most particles increased with the increases in pollution levels and relative humidity, yet they varied differently for different types of particles, highlighting the impacts of aging and formation processes on the changes of particle density and mixing state.Ītmospheric aerosols from both natural and anthropogenic sources exert strong influences on radiative forcing and human health (Buseck and Posfai, 1999 Anderson et al., 2003 Ramanathan et al., 2001 Prather, 2009), and the impacts depend strongly on their chemical and physical properties, e.g., composition, mixing state, and density. The average effective density ( ρ eff) of aerosol particles (150–300 nm) was 1.15 g cm −3 during the non-Olympic Winter Games (nOWG), with higher values during OWG (1.26 g cm −3) due to the increase in secondary particle contribution. ![]() This result indicates that emission controls during OWG reduced the mixing of EC with inorganic aerosol species and amines yet increased the mixing of EC with organic aerosol. The composition of carbonaceous particles also changed significantly which was characterized by the decreases in EC mixed with nitrate and sulfate (EC-NS), EC mixed with potassium nitrate (KEC-N), and amine-containing particles and increase in ECOC mixed with nitrate and sulfate (ECOC-NS). Particularly, the particles containing organic carbon and sulfate were enhanced significantly during OWG, although those from primary emissions decreased. Our results show the dominance of carbonaceous particles comprising mainly total elemental carbon (Total-EC, 13.4 %), total organic carbon (Total-OC, 10.5 %) and Total-ECOC (47.1 %). Here a single-particle aerosol mass spectrometer in tandem with a differential mobility analyzer and an aerodynamic aerosol classifier was deployed during the Beijing 2022 Olympic Winter Games (OWG) to investigate the impacts of emission controls on particle mixing state and density. Mixing state and density are two key parameters of aerosol particles affecting their impacts on radiative forcing and human health.
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