FORMATION AND SOURCES OF ATMOSPHERIC BROWN CARBON IN TROPICAL ENVIRONMENTS

Abstract

Impacts of brown carbon (BrC), the light absorbing fraction of organic aerosols, on global and regional climate are subject to large uncertainties that stem from the lack of understanding on the sources, formation processes and atmospheric evolution of BrC. This study contributes to this growing area of research by quantifying light absorbing properties of primary and secondary BrC in urban and biomass burning-impacted tropical environments that can potentially be utilized in future climate models and provides important insight into atmospheric processes that can transform the absorptivity of BrC in regional biomass burning episodes. The study also investigates the role of relative humidity (RH) on BrC formation in aqueous-phase reactions that are ubiquitous in tropical environments and provides fresh insight to potential factors that govern this behavior in evaporating droplets. The study further highlights the potential effects of anthropogenic-biogenic interactions that can affect BrC formation via aqueous-phase processing.