Detailed dissolved organic matter composition for different permafrost types across the western Canadian Arctic

Borehole sites were initially selected by the Government of Northwest Territories to assess ground conditions prior to building a road, the Inuvik-Tuktoyaktuk Highway (ITH). The borehole samples presented the opportunity to quantify the geochemical and geotechnical characteristics and variability of the substrate, which could then be entered into the Northwest Territories Geotechnical Database. In collaboration with scientists at the Northwest Territories Geological Survey, and other scientists at the University of Alberta, we sought to further expand the geochemical characterization by completing a detailed compositional analysis for leachates derived from different permafrost types. The compositional analyses of the leachates were completed using a combination of ITH borehole sample material, collected in the winter of 2017, as well as more shallow samples from the same sites, collected in the summer of 2018. Additionally, samples were collected from one site in the Klondike region, Yukon. The specific objectives of the leachate compositional analyses were to assess (1) how DOM composition may vary across permafrost end-members that have contrasting formational histories and have been subject to varying degrees of thaw modification, and (2) how contemporary active layer samples from multiple terrain types compares to those from permafrost end-members. We used a highly detailed technique to characterize dissolved organic matter composition for the water-extractable fraction leached from diverse permafrost end-member types, including tills, diamicton, lacustrine, peat, and Yedoma deposits, as well as from contemporary active layer samples from multiple landscape types (peatland, riparian and hilltop). These data accompany a manuscript that will soon be submitted for consideration at Environmental Research Letters (citation forthcoming). Further geotechnical characterization of the borehole samples can be found in Ensom et al. (2020). Ensom, T., Morse, P.D., Kokelj, S.V., MacDonald, E., Young, J., Tank, S., Subedi, R., Grozic, E., and Castagner, A., 2020. Permafrost Geotechnical Borehole Data Synthesis: 2013 2017 Inuvik-Tuktoyaktuk region, Northwest Territories; Northwest Territories Geological Survey, NWT Open Report 2019-012; Geological Survey of Canada, Open File 8652, 78 pages, geotechnical data, and appendices. https://doi.org/10.4095/321869