Journal
WATER RESEARCH
Volume 160, Issue -, Pages 97-106Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2019.05.052
Keywords
dissolved organic matter; EEM-PARAFAC; FT-ICR-MS; Alpine rivers; Anthropogenic effects; Himalayan-Tibetan plateau
Funding
- Guangdong Technion-Israel Institute of Technology, National Natural Science Foundation of China [41761144078]
- Strategic Priority Research Program of Chinese Academy of Sciences, Pan-Third Pole Environment Study for a Green Silk Road (Pan-TPE) [XDA20040501]
- State Key Laboratory of Cryospheric Science [SKLCS-ZZ-2017]
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The Tibetan Plateau is a critical ecosystem that sensitively responds to ongoing glacier shrinkage and permafrost thaw. Dissolved organic matter (DOM) in Tibetan Alpine rivers plays pivotal roles in the biogeochemical cycling of elements and nutrients at regional and even global scales, impacting water quality, downstream environments, and climate. However, little is known about the characteristics and dynamics of DOM in these watersheds. We investigated five major Himalayan rivers in the southern Tibetan Plateau, utilizing bulk dissolved organic carbon (DOC), optical properties, and molecular formulas. We found extremely low DOC and fluorescent DOM (FDOM) levels in the rivers (average DOC: 0.25-0.87 mg L-1, FDOM: 0.02-0.05 RU) with a highly degraded molecular signature, which was enriched with heteroatomic molecular formulas (S-containing: 58-72%, N-containing: 61-86%) and condensed aromatics (31-39% vs. similar to 11% in world major rivers). Further, 81-99% of the condensed aromatics was identified as dissolved black nitrogen (DBN) with multiple nitrogen atoms, typical for grassy biomass combustion. The findings highlighted potentially fast DOM remineralization leading to the release of CO2 and enriched apparently anthropogenic condensed aromatics and heteroatomic formulas in what have been considered pristine Tibetan rivers. These findings should be considered in future biogeochemical models and ecosystem management. (C) 2019 Elsevier Ltd. All rights reserved.
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