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Selective Leaching of Dissolved Organic Matter From Alpine Permafrost Soils on the Qinghai‐Tibetan Plateau
Author(s) -
Wang Yinghui,
Xu Yunping,
Spencer Robert G. M.,
Zito Phoebe,
Kellerman Anne,
Podgorski David,
Xiao Wenjie,
Wei Dandan,
Rashid Harunur,
Yang Yuanhe
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2017jg004343
Subject(s) - permafrost , soil water , dissolved organic carbon , environmental chemistry , leaching (pedology) , organic matter , plateau (mathematics) , soil organic matter , environmental science , total organic carbon , soil science , geology , chemistry , oceanography , mathematical analysis , mathematics , organic chemistry
Ongoing global temperature rise has caused significant thaw and degradation of permafrost soils on the Qinghai‐Tibetan Plateau (QTP). Leaching of organic matter from permafrost soils to aquatic systems is highly complex and difficult to reproduce in a laboratory setting. We collected samples from natural seeps of active and permafrost layers in an alpine swamp meadow on the QTP to shed light on the composition of mobilized dissolved organic matter (DOM) by combining optical measurements, ultrahigh‐resolution Fourier transform ion cyclotron resonance mass spectrometry, radiocarbon ( 14 C), and solid‐state 13 C nuclear magnetic resonance spectroscopy. Our results show that even though the active layer soils contain large amounts of proteins and carbohydrates, there is a selective release of aromatic components, whereas in the deep permafrost layer, carbohydrate and protein components are preferentially leached during the thawing process. Given these different chemical characteristics of mobilized DOM, we hypothesize that photomineralization contributes significantly to the loss of DOM that is leached from the seasonally thawed surface layer. However, with continued warming, biodegradation will become more important since biolabile materials such as protein and carbohydrate are preferentially released from deep‐layer permafrost soils. This transition in DOM leachate source and associated chemical composition has ramifications for downstream fluvial networks on the QTP particularly in terms of processing of carbon and associated fluxes.