261-1 The role of subsurface architecture for methane gas distribution and dynamics in two northern peatlands in Maine.

Session: The Current Understanding of the Role of Wetland Hydrology in the Cycling of Elements and other Substances: A Technical Session in Memory of Paul H. Glaser (Posters)

Poster Booth No.: 59

Presenting Author:

Md Rajeun Islam

Authors:

Islam, Md Rajeun¹, Peirce, Shelley², Newton, Imani³, Adams, Samuel H.⁴, Nering, Danielle⁵, Slater, Lee⁶, Reeve, Andrew S.⁷, Comas, Xavier⁸

(1) Department of Geosciences, Florida Atlantic University, Boca Raton, Florida, USA, (2) Department of Geosciences, Florida Atlantic University, Boca Raton, Florida, USA, (3) Department of Geosciences, Florida Atlantic University, Boca Raton, Florida, USA, (4) Department of Earth and Environment, Florida International University, Miami, Florida, USA, (5) Department of Earth and Environment, Florida International University, Miami, Florida, USA, (6) Department of Earth and Environmental Sciences, Rutgers University, Newark, New Jersey, USA, (7) Earth and Climate Sciences, University of Maine, Orono, ME, USA, (8) Department of Earth and Environment, Florida International University, Miami, Florida, USA,

Abstract:

Northern peatlands play a significant role in the global carbon cycle, acting as long-term carbon sinks while releasing greenhouse gases such as methane (CH₄) and carbon dioxide (CO₂) to the atmosphere. Quantification of gas fluxes from peatlands is critical for properly assessing their potential impacts on climate change and establishing mitigation strategies, however, gas fluxes are highly heterogeneous with reported values ranging over several orders of magnitude. These differences are typically attributed to factors such as peat matrix, microbial activity, vegetation, soil temperature, or water table that may vary depending on peatland type and latitude. Intrinsic factors such as soil matrix structure are considered to have an important role in dictating the spatial distribution of gases in the soil. Furthermore, previous studies in boreal systems have suggested that permeable subsurface geological materials (such as glacial eskers) may create conditions that control gas distribution and fluxes. In this study, we investigated five sites across two northern peatlands in Maine (Meddybemps and Sawtelle Heath) to assess differences in CH₄ gas accumulation and release associated with subsurface architecture (i.e., peat thickness, proximity to eskers). Measurements included time-lapse ground-penetrating radar (GPR) transects collected during five field campaigns (Aug 2022–Aug 2024) to generate both one and two-dimensional profiles of gas content with depth. Results were constrained using soil moisture and temperature probes for continuous in situ monitoring, gas traps for determining CH₄ fluxes, and analysis of peat cores for porosity and hydraulic conductivity. Preliminary results showed that sites with higher in-situ gas content (10-13% in total volume) also showed higher CH₄ fluxes (40-67 mg CH₄/m²/day), are independent of peat thickness (ranging between 3-10 m), but share close proximity to outcropping esker deposits (<200 m). These results support previous studies showing that permeable units beneath peatlands may influence groundwater movement and redox conditions, creating favorable conditions for methanogenic activity and gas production. Our integrated hydrogeophysical approach advances understanding of how peatland basin architecture might influence CH₄ hot spot development, supporting efforts for upscaling flux estimates.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7560

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