20 Dec 2022
20 Dec 2022
Status: this preprint is currently under review for the journal ACP.

Enhanced behaviors of optical properties and the radiative effects of molecular-specific brown carbon from dung combustion in the Tibetan Plateau

Qian Zhang1,2, Yujie Zhang1, Zhichun Wu1, Bin Zhang2, Yaling Zeng3, Jian Sun2, Hongmei Xu2, Qiyuan Wang4, Zhihua Li1, Junji Cao4, and Zhenxing Shen2 Qian Zhang et al.
  • 1Key Laboratory of Northwest Resource, Environment and Ecology, MOE, Xi’an University of Architecture and Technology, Xi’an 710055, China
  • 2Department of Environmental Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China
  • 3School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
  • 4Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China

Abstract. Traditional animal dung fuel use is a prominent source of brown carbon (BrC) in the Tibetan Plateau (TPL) region. Changes in burning conditions, fuel types, and uses of dung fuels in Plateau areas can lead to considerable uncertainties about molecular absorption properties and their radiative forcing influence on BrC. Here, the constituents of BrC’s chromophoric molecules emitted from residential heating and cooking scenarios using dung fuels were proposed using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry in the TPL region, China. Our results show that dung fuels in this study can release abundant BrC emissions with substantial high BrC absorption when compared with those observed in bitumite. Particularly, the linkage between BrC molecules and their absorption properties was quantified by partial least squares regression. Among detected BrC’s molecular groups, above 70 % of N-containing compounds (CHON and CHONS) with low-oxygen-containing and unsaturated aromatic bonds and 20.9–27.5 % of CHO compounds measured from the dung combustion samples were lies in the potential BrC chromophores regions. Further, a significantly enhanced contribution of molecular absorption coefficient (Mbabs) to total Mbabs (up to 99.7 %) was observed in the presence of both CHO and CHON (N2+N4) with distinctive characteristics of long carbon chains and high levels of unsaturation. Interestingly, the identified CHONS markers were highly oxygenated with abundant unsaturated double-bonds and high Mbabs, but were rarely produced under insufficient oxygen conditions at the high-altitude plateau. Meanwhile, the incomplete combustion of dung produced high values of integrated simple forcing efficiency and thus destroyed the radiation balance over the TPL region.

Qian Zhang et al.

Status: open (until 23 Feb 2023)

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  • RC1: 'Comment on acp-2022-801', Anonymous Referee #1, 12 Jan 2023 reply

Qian Zhang et al.


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Short summary
We identified the brown carbon (BrC) molecules and their absorbing abilities on a molecular level from animal dung fuel combustion over the Tibetan Plateau region in China. The ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometer coupled with the partial least squares regression were precisely applied to characterize the molecular absorptions, key molecular markers, and radiative effects of BrC from household combustion scenarios at the high-altitude area.