PERMAFROST THAW INFLUENCE ON SURFACE WATER DISSOLVED ORGANIC MATTER IN SUB-ARCTIC ALASKA

In the Northern hemisphere, 24% of exposed ground is underlain by permafrost, located in arctic and sub-arctic regions. Permafrost soils contain significant amounts of older carbon that may be mobilized or transformed upon thaw. The chemical composition of dissolved organic matter (DOM) is dependent upon the origin of the matter, terrestrial and microbial. However, the chemical and functional group composition of permafrost organic matter remains largely unknown indicating a lack of understanding of the DOM origin in past ecosystem. Characterizing DOM chemical composition has the potential to serve as a proxy to better understand the areas historic ecological background, and offer insight into the quality and extent of permafrost organic matter that may chemically or biologically transform upon mobilization. Permafrost, active layer, and surface water DOM chemical composition were compared across varying watersheds in central interior Alaska, inhabited and uninhabited by humans. Thaw was mimicked in the laboratory to identify leached organic moieties compared to the complete permafrost carbon pool and surrounding groundwater. Extracted isolates of DOM collected from cores containing both permafrost and active layer were characterized by several analytical techniques (3D excitation-emission fluorescence, UV-vis spectroscopy, SPR-W5-WATERGATE ¹H- NMR, total organic carbon, inductively coupled plasma mass spectroscopy, and ion chromatography), coupled with photolysis experiments. Such analysis provides insight into the specific moieties within permafrost compared to the active layer, and those moieties capable of being leached upon thaw. Sampling throughout the year aims to reveal seasonal variability of leaching and associated trends in DOM composition. A molecular level characterization of permafrost carbon composition and reactivity of is thus essential for assessing its impact on biogeochemical cycling and other ecological functions as it becomes incorporated into a warming landscape.