Laboratory Insights into the Diel Cycle of Optical and Chemical Transformations of Biomass Burning Brown Carbon Aerosols.
Environ Sci Technol
; 54(19): 11827-11837, 2020 10 06.
Article
in En
| MEDLINE
| ID: mdl-32870663
ABSTRACT
Transformations of biomass burning brown carbon aerosols (BB-BrC) over their diurnal lifecycle are currently not well studied. In this study, the aging of BB tar proxy aerosols processed by NO3⢠under dark conditions followed by the photochemical OH⢠reaction and photolysis were investigated in tandem flow reactors. The results show that O3 oxidation in the dark diminishes light absorption of wood tar aerosols, resulting in higher particle single-scattering albedo (SSA). NO3⢠reactions augment the mass absorption coefficient (MAC) of the aerosols by a factor of 2-3 by forming secondary chromophores, such as nitroaromatic compounds (NACs) and organonitrates. Subsequent OH⢠oxidation and direct photolysis both decompose the organic nitrates (ONs, representing bulk functionalities of NACs and organonitrates) in the NO3â¢-aged wood tar aerosols, thus decreasing particle absorption. Moreover, NACs degrade faster than organonitrates by photochemical aging. The NO3â¢-aged wood tar aerosols are more susceptible to photolysis than to OH⢠reactions. The photolysis lifetimes for the ONs and for the absorbance of the NO3â¢-aged aerosols are on the order of hours under typical solar irradiation, while the absorption and ON lifetimes toward OH⢠oxidation are substantially longer. Overall, nighttime aging via NO3⢠reactions increases the light absorption of wood tar aerosols and shortens their absorption lifetime under daytime conditions.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Carbon
/
Air Pollutants
Language:
En
Journal:
Environ Sci Technol
Year:
2020
Type:
Article
Affiliation country:
Israel