Permafrost is soil that has been frozen for two or more consecutive years. Discontinuous permafrost is dramatically thawing, allowing organic matter (OM) to be released from the permafrost into the surrounding hydrologic system. Characterizing dissolved organic matter (DOM) chemical composition from leached permafrost offers insight into the quality and extent of the permafrost carbon pool that may mobilize and transform upon thaw. The chemical and functional group composition of permafrost organic matter largely remains unknown, especially in discontinuous permafrost. In addition, the heterogeneity of permafrost organic matter with respect to geography is largely unresolved. 48” cores comprising both permafrost and active layer were sampled from three locations in interior Alaska in the summer of 2015 and spring of 2016. Each core was freeze-dried and homogenized prior to extraction. Permafrost OM was extracted using a variety of media (18 MΩ water at pH = 7, pH = 10, 0.5 M K<sub>2</sub>SO<sub>4</sub>, and methanol). Cores were leached for seven days at 4°C in the dark to allow for capture of both long and short term kinetic OM. Leaching media was filtered and the collected via solid phase extraction with PPL cartridges and subsequently freeze-dried. Efficiency of extraction was monitored by total organic carbon analysis. Further characterization of extracted DOM from both permafrost and active layer leachates was conducted via nuclear magnetic resonance (NMR), inductive coupled plasma mass spectrometry (ICP-MS), UV-Vis, and fluorescence excitation emission matrices (EEMs). PARAFAC analysis was also performed to resolve fluorescent component differences between permafrost and active layer, as well as sampling location. Reactivity of DOM was assessed through addition of reactive oxygen species probes in the presence of a solar simulator. Both photolyzed and unphotolyzed DOM were characterized through the above methods.

Permafrost dissolved organic matter leachability and reactivity in the presence of various solutions from an Alaskan Sub-Arctic watershed

253rd National Meeting (2017)

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