Formation of highly absorptive secondary brown carbon through nighttime multiphase chemistry of biomass burning emissions

Formation of highly absorptive secondary brown carbon through nighttime multiphase chemistry of biomass burning emissions

Blog Article

Biomass burning is a major global source of both primary brown carbon (BrC) and reactive trace gases in the atmosphere and thus has a significant impact on global climate and regional atmospheric chemistry.However, a substantial gap remains in our understanding of the nighttime evolution of biomass burning emissions.Here we present prominent nighttime formation of secondary organic aerosol (Night-OA) with strong absorptivity but markedly different spectral dependence from that of primary biomass burning organic aerosols, which was observed during autumn in 15-eg2373cl the Pearl River Delta region of China when biomass burning plumes prevailed.

Our results demonstrate that the formation of Night-OA appeared to have high dependence on both the magnitudes of biomass burning emissions at nightfall and available oxidants of NO2 and O3.Active nighttime NO3 radical chemistry was characterized by quick O3 depletion and almost zero concentration of NO.The rapid decrease in NO2 coincident with the quick nitrate formation suggests that the rapid NO2 consumption supplied the NO3 and N2O5 reaction chains.

However, the quickest Night-OA formation occurred when nitrate formation ceased and relative humidity reached maximum, and it mainly added mass to aerosol water-abundant diameter ranges.This co-variation suggests that gas-phase reactions of biomass burning precursors, along with aqueous-phase chemistry involving preexisting hygroscopic aerosols in the diluted plume, likely work in concert to promote the rapid nighttime formation of Night-OA.Preexisting background aerosols are generally much more hygroscopic than the aerosols directly emitted from biomass burning.

Incorporating the important role of background aerosols in the aging of diluted biomass burning plumes would be valuable in future laboratory and model simulation studies.The proposed mechanisms for caruso milk thistle secondary BrC formation have broad implications for the climate and air quality impacts of biomass burning, including the interaction between biomass burning plumes and background aerosols in humid regions, as well as with water-abundant pyroconvection clouds.