As biomass-burning smoke is transported thousands of miles, the soluble and reactive organic gases present in the smoke react with liquid water contained in fine particles and clouds in the atmosphere. These chemical reactions produce secondary organic aerosol particles that contribute to brown haze.
Newswise — Wildfires continue to increase in frequency and severity, transporting smoke for thousands of miles. The smoke contains soluble organic gases. The reactions of these gases, which form aqueous-phase secondary organic aerosols (SOA) in aerosols and clouds, might be important for understanding global and regional climate modeling. So far, a quantitative and predictive understanding of the cloud chemistry of biomass-burning organic gases has been missing from such models. Using mechanisms derived from laboratory measurements, a multi-institutional team of researchers simulated the multiphase chemistry of water-soluble organic gases emitted by biomass burning, and that includes their dissolution within aerosol and cloud liquid water followed by their aqueous-phase reactions to form SOA. Within cloud layers, they found that highly soluble and reactive multifunctional phenols are almost entirely dissolved and react in cloud water, causing SOA formation that greatly exceeds their previously known formation due to gas-phase chemistry within these layers. Even near the surface in the absence of clouds, these highly soluble phenols form significant amounts of SOA in aqueous aerosols because they can be easily dissolved in aerosol liquid water and are available for aqueous aerosol chemistry. The team’s research is expected to open new frontiers in the understanding of how cloud chemistry increases SOA loadings in the atmosphere and its ability to seed clouds and to scatter and absorb the sun’s radiation. In addition, this work will aid in the design of laboratory-based cloud chamber measurements that aim to understand how SOA cloud chemistry causes detectable changes in cloud droplet residuals and aerosols that serve as cloud condensation nuclei.
RSS