04 Oct 2022
04 Oct 2022
Status: this preprint is currently under review for the journal ACP.

Impacts of biomass burning and photochemical processing on the light absorption of brown carbon in the southeastern Tibetan Plateau

Jie Tian1,2, Qiyuan Wang1,2, Yongyong Ma3, Jin Wang1, Yongming Han1,2, and Junji Cao1,4 Jie Tian et al.
  • 1Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
  • 2CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
  • 3Meteorological Institute of Shaanxi Province, Xi’an 710015,
  • 4Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Abstract. Brown carbon (BrC) in the atmosphere can greatly influence aerosol’s radiative forcing over the Tibetan Plateau (TP), because it has the non-negligible capacity of light absorption as well as black carbon (BC); however, our understanding of optical properties, sources, atmospheric processes of BrC in this region remains limited. In this study, a multiple-wavelength Aethalometer coupled with a quadrupole aerosol chemical speciation monitor were deployed to investigate the highly time resolved BrC in the submicron aerosol in the southeastern edge of the TP during the pre-monsoon season. The result showed that BrC had the substantial contributions (20.0–40.2 %) to the light absorption of submicron aerosol from 370 to 660 nm. Organic aerosol (OA), an alternative to BrC, was split into a biomass burning OA (BBOA) with aging process and a photochemical-oxidation processed oxygenated OA (po-OOA) by a hybrid environmental receptor model analysis. Combined with light absorption coefficient of BrC (babs-BrC), the source-specific mass absorption cross section of BBOA (0.50−1.75 m2 g-1) and po-OOA (0.38−2.15 m2 g-1) at 370−660 nm were retrieved. On average, babs-BrC from po-OOA (1.1−6.3 Mm-1) was higher than that from BBOA (0.7−2.3 Mm-1) at all wavelengths. The concentration weighted trajectory analysis showed that the most important potential source regions for babs-BrC values from BBOA and po-OOA were located in the northern Myanmar and along the China-Myanmar border, indicating the cross-border transport of BrC from Southeast Asia. A "simple forcing efficiency" evaluation further illustrated the importance of BrC radiative effect with the high fractional radiative forcing by two OAs relative to BC (50.6 ± 18.7 %). This study highlighted a significant influence of BrC from biomass burning emissions and secondary formation on climate change over the TP region during the pre-monsoon season.

Jie Tian et al.

Status: open (until 03 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-618', Anonymous Referee #1, 26 Oct 2022 reply
  • RC2: 'Comment on acp-2022-618', Anonymous Referee #2, 18 Nov 2022 reply

Jie Tian et al.

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Impacts of biomass burning and photochemical processing on the light absorption of brown carbon in the southeastern Tibetan Plateau Tian, Jie; Wang, Qiyuan; Ma, Yongyong; Wang, Jin; Han, Yongming; Cao, Junji

Jie Tian et al.


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Short summary
We investigated the light absorption properties of brown carbon (BrC) in the Tibetan Plateau. BrC had the substantial contribution to the submicron aerosol absorption, which is related to the cross-border transport of biomass burning emission and secondary aerosol from Southeast Asia. The radiative effect of BrC was half that of black carbon. In particular, BrC formed from photochemical processing contributed significantly to radiative forcing, twice as much as that of BrC from biomass burning.