Biomass-burning organic aerosols as a pool of atmospheric reactive triplets to drive multiphase sulfate formation.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39671187.
- Also identified by DOI 10.1073/pnas.2416803121 and PMC identifier 11665901.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Biomass-burning organic aerosol(s) (BBOA) are rich in brown carbon, which significantly absorbs solar irradiation and potentially accelerates global warming. Despite its importance, the multiphase photochemistry of BBOA after light absorption remains poorly understood due to challenges in determining the oxidant concentrations and the reaction kinetics within aerosol particles. In this study, we explored the photochemical reactivity of BBOA particles in multiphase S(IV) oxidation to sulfate. We found that sulfate formation in BBOA particles under light is predominantly driven by photosensitization involving the triplet excited states (<sup>3</sup>BBOA<sup>*</sup>) instead of iron, nitrate, and S(IV) photochemistry. Rates in BBOA particles are three orders of magnitude higher than those observed in the bulk solution, primarily due to the fast interfacial reactions. Our results highlight that the chemistry of <sup>3</sup>BBOA<sup>*</sup> in particles can greatly contribute to the formation of sulfate, as an example of the secondary pollutants. Photosensitization of BBOA will likely become increasingly crucial due to the intensified global wildfires.