Singlet Oxygen and Triplet Excited State Organics Produced by Primary Biomass Burning Organic Aerosol from Wood, Dung, Straw, and Plastic Fuels: Role of Solvent-Dependent Photochemistry
Year: 2026
Type: article
Abstract: Biomass burning organic aerosol (BBOA) is a significant source of brown carbon (BrC), a class of light-absorbing organic compounds that influence climate and atmospheric oxidation chemistry. Certain BrC chromophores act as photosensitizers by producing reactive oxidants such as singlet oxygen (SO) and triplet excited states (TP) upon solar irradiation, but we still cannot predict which functional groups drive the production of these excited state oxidants. We hypothesized that since the major sink for SO is solvent deactivation, water-based extractions of chromophores may (1) underestimate SO production in BBOA, as well as (2) overlook water insoluble chromophores potentially important in hydrophobic aerosol phases. To better represent the multiphase nature of atmospheric aerosols in this work, we employed a co-solvent extraction using acetonitrile and water to extract the hydrophobic fraction of BrC chromophores. Primary organic aerosol (POA) filters from the combustion of beechwood, cow dung, straw, and plastic were collected during the BAMBE campaign, and subsequently analyzed using a two-probe photochemical method with furfuryl alcohol and syringol as probes to quantify SO and TP steady-state concentrations and quantum yields, respectively, under UVA irradiation. The acetonitrile-water mixture enhanced chromophores recovery and modulated the quenching of the excited state of SO back to O2, leading to up to a six-fold increase in SO concentrations. Fuel type significantly influenced oxidant yields; beechwood and plastic extracts showed the highest SO and TP production, up to 4.9 ±0.1% for SO and 4.2 ±0.2% for TP. Complementary FIGAERO-CIMS analysis revealed compositional differences between fuels and combustion conditions, suggesting nitrogen-containing species drove the variability in sensitization efficiency. Our findings underscore the importance of solvent selection and fuel source in assessing BrC photochemical activity and offer new insights into the oxidative potential of BBOA in atmospheric multiphase environments.
Source: ACS ES&T Air
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7124289971