Molecular compositions, optical properties, and implications of dissolved brown carbon in snow/ice on the Tibetan Plateau glaciers

Xiaofei Li; Pingqing Fu; Lekhendra Tripathee; Fangping Yan; Zhaofu Hu; Feng Yu; Qian Chen; Jinwen Li; Qingcai Chen; Junji Cao; Shichang Kang

doi:10.1016/j.envint.2022.107276

Molecular compositions, optical properties, and implications of dissolved brown carbon in snow/ice on the Tibetan Plateau glaciers

Environ Int. 2022 Jun:164:107276. doi: 10.1016/j.envint.2022.107276. Epub 2022 May 7.

Authors

Xiaofei Li¹, Pingqing Fu², Lekhendra Tripathee³, Fangping Yan³, Zhaofu Hu³, Feng Yu⁴, Qian Chen⁴, Jinwen Li⁴, Qingcai Chen⁴, Junji Cao⁵, Shichang Kang⁶

Affiliations

¹ School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an 710021, China; Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China; State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
² Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
³ State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁴ School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an 710021, China.
⁵ Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China; Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Electronic address: jjcao@mail.iap.ac.cn.
⁶ State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: shichang.kang@lzb.ac.cn.

PMID: 35537366
DOI: 10.1016/j.envint.2022.107276

Abstract

Brown carbon (BrC)/water-soluble organic carbon (WSOC) plays a crucial role in glacier melting. A quantitative evaluation of the light absorption characteristics of WSOC on glacier melting is urgently needed, as the WSOC release from glaciers potentially affects the hydrological cycle, downstream ecological balance, and the global carbon cycle. In this work, the optical properties and composition of WSOC in surface snow/ice on four Tibetan Plateau (TP) glaciers were investigated using a three-dimensional fluorescence spectrometer and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The total light-absorption of WSOC in snow/ice at 250-400 nm (ultraviolet region) and 400-600 nm (visible region) accounted for about 60.42% and 27.17% of the light absorption by the total organics, respectively. Two protein-like substances (PRLIS), one humic-like substance (HULIS), and one undefined species of chromophores in snow/ice on the TP glacier surfaces were identified. The lignins and lipids were the main compounds in the TP glaciers and were presented as CHO and CHNO molecules, while CHNOS molecules were only observed in the southeast TP glacier. The light absorption capacity of WSOC in snow/ice was mainly affected by their oxidizing properties. PRLIS and undefined species were closely linked to microbial sources and the local environment of the glaciers (lignins and lipids), while HULIS was significantly affected by anthropogenic emissions (protein/amino sugars). Radiative forcing (RF)-induced by WSOC relative to black carbon were accounted for about 11.62 ± 12.07% and 8.40 ± 10.37% in surface snow and granular ice, respectively. The RF was estimated to be 1.14 and 6.36 W m^-2 in surface snow and granular ice, respectively, during the melt season in the central TP glacier. These findings contribute to our understanding of WSOC's impact on glaciers and could serve as a baseline for WSOC research in cryospheric science.

Keywords: Dissolved brown carbon; Glacier melt; Molecular compositions; Optical properties; Tibetan Plateau.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Carbon / analysis
Environmental Monitoring / methods
Humic Substances / analysis
Ice Cover* / chemistry
Lignin
Lipids
Snow*
Tibet
Water / analysis

Substances

Humic Substances
Lipids
Water
Carbon
Lignin