Landfill cover soils: variable moisture and temperature effects on methane oxidation
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Date
2023-05-15
Authors
Lam, Christina
Slowinski, Stephanie
Willms, N
Hug, L
Van Cappellen, Philippe
Rezanezhad, Fereidoun
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
Landfills are one of the largest anthropogenic sources of methane (CH4), comprising over 20% of
Canada’s CH4 emissions. Hot-spots of CH4 emissions in landfill cover soils have shown an enrichment of
microbes that consume CH4 and produce carbon dioxide (CO2) through CH4 oxidation, which can act as
a natural solution to reduce CH4 emissions. CH4 oxidation is affected by soil moisture and temperature,
although their simultaneous effects on CH4 oxidation rates have not been well-studied. Here, we
conducted a closed-headspace batch experiment with cover soil from a former landfill in Waterloo,
Ontario, to measure CH4 oxidation and CO2 efflux rates associated with variations in soil moisture and
temperature simultaneously. The soil samples were prepared under 5 soil moisture contents (% WFPS;
water-filled pore space), ranging from 11 to 47% WFPS, and incubated following a regime whereby
temperatures increased from 1 to 35°C (Phase I) then decreased from 35 to 1°C (Phase II). Every 2 days,
the temperature was adjusted to the next value for a 24-hour acclimation period while open to the
atmosphere, then the headspace was closed and spiked with CH4 (150 ppm). Headspace CH4 and CO2
concentrations were measured over 2 hours to calculate apparent CH4 oxidation and CO2 efflux rates.
The maximum CO2 efflux rate was observed at the maximal WFPS and temperature conditions of this
experiment (91.5 nmol h-1 g dry wt.-1 at 47% WFPS and 35°C). In contrast, the maximum CH4 oxidation
rates were observed at intermediate WFPS and temperature conditions (1.86 nmol h-1 g dry wt.-1 at
25% WFPS and 25°C). These experimental results provide insight into favourable WFPS and temperature
conditions for CH4 oxidation, and therefore into how seasonal changes in WFPS and temperature could
impact CH4 oxidation.
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GWF AOSM 2023