Low photolability of yedoma permafrost dissolved organic carbon

Aron Stubbins, Paul Mann, Leanne Powers, Thais Bittar, Thorsten Dittmar, Cameron McIntyre, Timothy Eglinton, Nikita Zimov, Robert Soencer

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)

Abstract

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.
Original languageEnglish
JournalJournal of Geophysical Research: Biogeosciences
Early online date27 Dec 2016
DOIs
Publication statusPublished - 31 Jan 2017

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