Low photolability of yedoma permafrost dissolved organic carbon

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• 作者：Aron Stubbins ; Paul J. Mann ; Leanne Powers ; Thais B. Bittar ; Thorsten Dittmar ; Cameron P. McIntyre ; Timothy I. Eglinton ; Nikita Zimov ; Robert G. M. Spencer
• 刊名：Journal of Geophysical Research: Biogeosciences
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：122
• 期：1
• 页码：200-211
• 全文大小：998.6KB
• ISSN：2169-8961

文摘

Vast stores of arctic permafrost carbon that have remained frozen for millennia are thawing, releasing ancient dissolved organic carbon (DOC) to arctic inland waters. Once in arctic waters, DOC can be converted to CO₂ and emitted to the atmosphere, accelerating climate change. Sunlight-driven photoreactions oxidize DOC, converting a portion to CO₂ and leaving behind a photomodified pool of dissolved organic matter (DOM). Samples from the Kolyma River, its tributaries, and streams draining thawing yedoma permafrost were collected. Irradiation experiments and radiocarbon dating were employed to assess the photolability of ancient permafrost-DOC in natural and laboratory generated samples containing a mix of modern and ancient DOC. Photolabile DOC was always modern, with no measurable photochemical loss of ancient permafrost-DOC. However, optical and ultrahigh resolution mass spectrometric measurements revealed that both modern river DOM and ancient permafrost-DOM were photomodified during the irradiations, converting aromatic compounds to less conjugated compounds. These findings suggest that although sunlight-driven photoreactions do not directly mineralize permafrost-DOC, photomodification of permafrost-DOM chemistry may influence its fate and ecological functions in aquatic systems.