Efficient Production of Reactive Oxidants by Atmospheric Bacterial-Derived Organic Matter in the Aqueous Phase

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

Abstract

Hydroxyl radicals (•OH), singlet oxygen (1O2*), and organic triplet excited states (3C*) play key roles as oxidants (“reactive intermediates (RIs)”) in forming and oxidizing aqueous organic aerosols. Bioaerosols are ubiquitous in the atmosphere, but little is known about their photochemical behavior and contributions to atmospheric photochemistry. We investigated the photochemical behavior of aqueous-phase cellular organic matter (COM) and extracellular polymeric substances (EPS) from cultured bacteria isolated from atmospheric PM2.5, focusing on their photochemical production of 3C*, 1O2*, and •OH. The molecular size and aromaticity of chromophores and fluorophores in COM and EPS increased with molecular weight (MW). Apparent quantum yields (ΦRI) of up to 10% and 5% were measured for 1O2* and 3C*, respectively, which are in the upper range of previously reported values. This indicated that COM and EPS contain photosensitizers that are highly efficient at producing 1O2* and 3C*. ΦRI and concentrations ([RI]ss) decreased with MW due to higher-MW molecules engaging in charge-transfer interactions that disrupt photochemical processes and oxidant production. Machine learning models were used to understand and predict oxidant production based on measurable optical and chemical properties of COM and EPS. This study provides new insights into the roles that bioaerosols can play in atmospheric aqueous photochemistry. © 2025 American Chemical Society.
Original languageEnglish
Pages (from-to)6757–6770
JournalEnvironmental Science and Technology
Volume59
Issue number13
Online published28 Mar 2025
DOIs
Publication statusPublished - 8 Apr 2025

Funding

This work was supported by the National Natural Science Foundation of China (project number 42005081) and the Research Grants Council of the Hong Kong Special Administrative Region, China (project number 11303720).

Research Keywords

  • atmospheric photochemistry
  • bacterial-derived organic matter
  • extracellular polymeric substances
  • hydroxyl radical
  • organic triplet excited states
  • singlet oxygen

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