22-6 Influence of Hydrology and Recent Wildfires on Dissolved Black Carbon Export Behavior in the Yukon River, Alaska

Session: Advances in characterizing groundwater, surface water, and their interactions (Posters)

Poster Booth No.: 14

Presenting Author:

Madelyn Miller

Authors:

Miller, Madelyn¹, Slentz, Alexis², Anderson, James³, Turner, Kyle⁴, Edmund, Augusta ⁵, Hamilton, Theodore⁶, Strongheart, Keira ⁷, Kellerman, Anne⁸, Tzortziou, Maria⁹, Spencer, Robert ¹⁰, Wagner, Sasha¹¹

(1) Earth and Environmental Science, Rensselaer Polytechnic Institute, Troy, , (2) Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, , (3) Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, , (4) Earth and Atmospheric Sciences, CUNY City College of New York, New York, , (5) IGAP Environmental Program of Alakanuk, Alakanuk, , (6) Alakanuk Traditional Council, IGAP, Alakanuk, , (7) Alakanuk Traditional Council, IGAP, Alakanuk, , (8) Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, , (9) Earth and Atmospheric Sciences, CUNY City College of New York, New York, , (10) Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, , (11) Earth and Environmental Science, Rensselaer Polytechnic Institute, Troy, ,

Abstract:

In the summer of 2022, Alaska (USA) experienced one of its largest fire years on record, with boreal forest and tundra wildfires alike contributing to over 2.5 million acres burned in the Yukon River watershed alone. While much of the organic carbon within biomass is converted to CO₂ upon combustion, roughly 12% is converted into black carbon, a class of environmentally persistent polycondensed aromatic molecules. Despite increasing fire activity at higher latitudes, little work has been done to characterize the impact of wildfires and hydrologic regime (i.e. spring freshets) on the export behavior of dissolved black carbon (DBC) in Arctic rivers. By comparing time series samples collected from the Yukon River Delta through the late spring and summer of 2022, 2023, and 2024, we present a longitudinal view of the evolving biogeochemistry within a major Arctic system during, and in the two years following, substantial fire activity. Preliminary findings show a strong seasonal distinction between late spring and summer, coinciding with the freshet in late May and falling limb of the hydrograph through the rest of the year. Dissolved organic carbon (DOC) and DBC concentrations were directly correlated with discharge while DBC:DOC and DBC stable carbon isotope values presented inverse relationships. DBC concentrations did not differ significantly between the three years, but the proportion of DBC in bulk DOC increased from 4.5% in 2022 to 6.6% in 2024. The degree of condensed aromaticity of DBC decreased immediately in 2022 at the onset of local tundra fires and remained low through 2023 before returning to pre-fire values in 2024. Our findings support previous studies that hydrology is the primary control on DBC concentrations and fluxes. However, recent fire activity and time since fire do influence the composition and proportional contributions of refractory organic carbon exported by fire-affected catchments.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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