Slow bleaching of water-insoluble brown carbon from biomass burning: Implication for direct radiative effect.

Authors

Wenli Liu, Xinchun Xie, Lijuan Li, Rui Wang, Xin Zhang, Xinye Luo, Yuemei Han, Yuzhong Zhang, Mikinori Kuwata

Published in

Science advances. Volume 12. Issue 34. Pages eaef9320. Aug 21, 2026. Epub Aug 21, 2026.

Abstract

Biomass burning organic aerosol (BBOA) is a major source of atmospheric brown carbon (BrC), which contributes to climate through solar radiation absorption. Chemical aging (bleaching) of BrC diminishes light absorption over time. Although recent modeling studies have emphasized the need to account for bleaching when assessing BrC's climate impacts, a parameterization representing the entire BBOA matrix has been lacking. Here, we develop a bleaching parameterization for the whole BrC in BBOA based on laboratory experiments that systematically varied temperature and relative humidity. The bleaching timescale increases under low-humidity and low-temperature conditions, likely due to enhanced aerosol viscosity. Implementing this parameterization in a global model increases the simulated direct radiative effect (DRE) of BrC by 1.5 to 2 times relative to previous estimates, with associated uncertainties exceeding 10% of the total organic aerosol DRE. The present scheme particularly shows elevated fresh BrC concentrations in boreal regions, suggesting that bleaching dynamics may influence not only radiative forcing but also snow darkening effects.

PMID:
42627893
Bibliographic data and abstract were imported from PubMed on 22 Aug 2026.

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