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279-9 Characterizing peat decomposition and methane ebullition at discrete edges of a northern peatland pool

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

Presenting Author:

Raymond Hess

Authors:

Hess, Raymond J.¹, Moore, Henry E.², Comas, Xavier³, Reeve, Andrew S.⁴, Ntarlagiannis, Dimitrios⁵, Slater, Lee D.⁶

(1) Department of Earth and Environmental Sciences, Rutgers University, Newark, New Jersey, USA, (2) Faculty of Geosciences, University of Bremen, Bremen, Germany, (3) Department of Earth and Environment, Florida International University, Miami, Florida, USA, (4) School of Earth and Climate Sciences, University of Maine, Orono, Maine, USA, (5) Department of Earth and Environmental Sciences, Rutgers University, Newark, New Jersey, USA, (6) Department of Earth and Environmental Sciences, Rutgers University, Newark, New Jersey, USA; Earth Systems Science Division, Pacific Northwest National Laboratory, Richland, Washington, USA,

Abstract:

Patterned pools commonly found on the surface of northern raised peat bogs have been recognized as hot spots for carbon cycling. Previous hydrogeophysical studies of pools in a raised northern bog near Bangor, Maine, USA, identified variations in permeability of the bounding mineral sediments, along with distinct temperature and specific conductance contrasts, indicative of groundwater upwelling. Within this system, we examined two locations along the edges of a single pool, characterized by variations in the underlying sedimentary structure, to better understand the hydrogeologic processes influencing localized carbon cycling. Peat cores were collected at both locations and visually inspected at 10 cm intervals using the von Post humification index. In the soil column above more permeable mineral sediments, these tests revealed highly decomposed peat in the upper one meter of the profile. For the second soil column, which sits above hydraulically confining mineral sediments, the upper one meter consisted of partially decomposed mosses and more fibrous peat. Loss on ignition showed near complete combustion of organic material from both profiles, 96 to 99%, with sharp reductions in loss to less than 12% at peat–mineral sediment interfaces. Over a 10-day period, ebullition was continuously monitored and collected using timelapse cameras and waterborne gas traps. On average, 119 mg m^-2 d^-1 of methane was collected from the pool’s edge above hydraulically conductive mineral sediments, compared to 21 mg m^-2 d^-1 collected from the water column above confining sediments. Gas chromatography analysis for ebullition samples showed headspace equilibrium concentrations of methane ranging from 105 to 1542 ppm. In surface waters, headspace equilibrium concentrations of carbon dioxide and methane indicated supersaturated conditions (relative to atmospheric equilibrium), with average values exceeding 2500 ppm for both gases. Studies of this kind aim to better quantify gas fluxes in heterogeneous environments, for which extensive datasets don't exist.

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

doi: 10.1130/abs/2025AM-5793

Characterizing peat decomposition and methane ebullition at discrete edges of a northern peatland pool

Description

Session Format: Oral

Presentation Date: 10/22/2025

Presentation Start Time: 04:05 PM

Presentation Room: HBGCC, 214A

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