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dc.contributor.authorHolt, Amy D.
dc.contributor.authorKellerman, Anne M.
dc.contributor.authorLi, Wenbo
dc.contributor.authorStubbins, Aron
dc.contributor.authorWagner, Sasha
dc.contributor.authorMcKenna, Amy
dc.contributor.authorFellman, Jason B.
dc.contributor.authorHood, Eran
dc.contributor.authorSpencer, Robert G. M.
dc.date.accessioned2022-04-08T23:37:11Z
dc.date.available2022-04-08T23:37:11Z
dc.date.issued2021-11-04
dc.identifier.citationHolt, A. D., Kellerman, A. M., Li, W., Stubbins, A., Wagner, S., McKenna, A., et al. (2021). Assessing the role of photochemistry in driving the composition of dissolved organic matter in glacier runoff. Journal of Geophysical Research: Biogeosciences, 126, e2021JG006516. https://doi. org/10.1029/2021JG006516en_US
dc.identifier.urihttp://hdl.handle.net/11122/12858
dc.description.abstractDissolved organic matter (DOM) in glacier runoff is aliphatic-rich, yet studies have proposed that DOM originates mainly from allochthonous, aromatic, and often aged material. Allochthonous organic matter (OM) is exposed to ultraviolet radiation both in atmospheric transport and post-deposition on the glacier surface. Thus, we evaluate photochemistry as a mechanism to account for the compositional disconnect between allochthonous OM sources and glacier runoff DOM composition. Six endmember OM sources (including soils and diesel particulate matter) were leached and photo-irradiated for 28 days in a solar simulator, until >90% of initial chromophoric DOM was removed. Ultrahigh-resolution mass spectrometry was used to compare the molecular composition of endmember leachates pre- and post-irradiation to DOM in supraglacial and bulk runoff from the Greenland Ice Sheet and Juneau Icefield (Alaska), respectively. Photoirradiation drove molecular level convergence between the initially aromatic-rich leachates and aromatic-poor glacial samples, selectively removing aromatic compounds (−80 ± 19% relative abundance) and producing aliphatics (+75 ± 35% relative abundance). Molecular level glacier runoff DOM composition was statistically indistinguishable to post-irradiation leachates. Bray-Curtis analysis showed substantial similarity in the molecular formulae present between glacier samples and post-irradiation leachates. Post-irradiation leachates contained 84 ± 7.4% of the molecular formulae, including 72 ± 17% of the aliphatic formulae, detected in glacier samples. Our findings suggest that photodegradation, either in transit to or on glacier surfaces, could provide a mechanistic pathway to account for the disconnect between proposed aromatic, aged sources of OM and the aliphatic-rich fingerprint of glacial DOM.en_US
dc.description.sponsorshipMegan I. Behnke is thanked for collecting the Alaskan soil samples, Stephanie McColaugh for collecting the Russell Glacier samples, Casey Luzius for help with leachate preparations, and Sarah Ellen Johnston for assistance with DOC analyses. Funding Source: This study was supported by NSF, DEB 1145932 and OCE 1333157 to R. G. M. Spencer. Funding was provided by Alaska EPSCoR (OIA-1757348). A portion of this work was performed in the Ion Cyclotron Resonance User Facility at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation Division of Chemistry and Division of Materials Research through DMR 16-44779, and the State of Florida.en_US
dc.language.isoen_USen_US
dc.publisherAmerican Geophysical Unionen_US
dc.subjectDissolved organic matter (DOM)en_US
dc.subjectGlacier runoffen_US
dc.subjectPhotochemistryen_US
dc.subjectJuneau Icefielden_US
dc.subjectGreenland Ice Sheeten_US
dc.titleAssessing the Role of Photochemistry in Driving the Composition of Dissolved Organic Matter in Glacier Runoffen_US
dc.typeArticleen_US
dc.description.peerreviewYesen_US
refterms.dateFOA2022-04-08T23:37:11Z
dc.identifier.journalJournal of Geophysical Research: Biogeosciencesen_US


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