Preprints
https://doi.org/10.5194/bg-2017-507
https://doi.org/10.5194/bg-2017-507

  18 Dec 2017

18 Dec 2017

Review status: this preprint was under review for the journal BG but the revision was not accepted.

Physical and chemical evolution of dissolved organic matter across the ablation season on a glacier in the central Tibetan Plateau

Lin Feng1,3, Yanqing An1, Jianzhong Xu1, Shichang Kang1,2,3, Xiaofei Li1,2, Yongqiang Zhou4, Yunlin Zhang4, Bin Jiang5, and Yuhong Liao5 Lin Feng et al.
  • 1State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
  • 2CAS Center for Excellence inTibetan Plateau Earth Sciences
  • 3University of Chinese Academy of Sciences, Beijing 100049, China, CAS Center for Excellence in Tibetan Plateau Earth Sciences
  • 4State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China
  • 5State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640, PR China

Abstract. The physical evolution (metamorphism) of snow is known to affect the chemical composition of dissolved organic matter (DOM) within it. Here, we present a comprehensive study on the Dongkemadi glacier in the central Tibetan Plateau by analyzing surface snow/ice samples collected from May to October 2015. Based on their physical descriptions, these samples were grouped into four categories, i.e., fresh snow, fine firn, coarse firn, and granular ice that represented the different stages of snowmelt. The concentrations of dissolved organic carbon (DOC) decreased from fresh snow (26.8 μmol L−1) to fine firn (15.0 μmol L−1) and then increased from fine firn to coarse firn (26.1 μmol L−1) and granular ice (34.4 μmol L−1). This reflected the dynamic variations in DOC observed during snowmelt. The use of excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC) identified three protein-like components (C1, C2 and C4) and one microbial humic-like component (C3), which reflected the presence of significant amounts of microbially derived DOM in surface snow/ice. The molecular level compositions of DOM identified using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) also showed the presence of molecules that were newly produced during snowmelt. These results suggest that snowmelt not only induced a loss of DOM but also intensified the in situ microbial activities that enriched and modified it. These findings are important for understanding the evolution of the physical and chemical characteristics of DOM during the ablation season and can also shed some light on the nature of biogeochemical cycles in cryospheric regions.

Lin Feng et al.

 
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Lin Feng et al.

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