Open AccessSpatiotemporal variability in peatland subsurface methane dynamics
Author(s) -
Strack M.,
Waddington J. M.
Publication year - 2008
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jg000472
Subject(s) - peat , water table , environmental science , atmospheric sciences , residence time (fluid dynamics) , methane , flux (metallurgy) , hydrology (agriculture) , volume (thermodynamics) , environmental chemistry , soil science , groundwater , chemistry , geology , ecology , physics , geotechnical engineering , organic chemistry , quantum mechanics , biology
Peatlands are large natural sources of atmospheric methane (CH 4 ). While many studies have measured CH 4 emissions to the atmosphere, less is known about the stock and residence time of subsurface CH 4 . In this study we examined dissolved CH 4 concentration in near‐surface peatland pore waters of a poor fen near Québec City, Canada, in order to (1) investigate the variability in and potential controls on these concentrations and (2) combine measured dissolved CH 4 concentration with estimated bubble CH 4 stock and measured CH 4 fluxes to estimate the mean residence time of subsurface CH 4 . Concentrations ranged from 1 to 450 μ M during both study seasons. Depth profiles were generally consistent at one location within the peatland throughout the sampling period but varied between locations. Patterns with depth were not well correlated to pore water pH or EC; however, changes in CH 4 concentration through time in the upper 30 cm were related to temperature and water table at some locations. Depth profiles taken at 2‐ to 5‐cm intervals revealed discrete concentration “spikes” which were often maintained throughout the season and are likely related to bubble CH 4 dynamics. Estimated subsurface CH 4 stocks indicate that even when relatively low bubble volume (5% of peat volume) is assumed, bubble CH 4 accounted for greater than half of total stocks. Calculated mean residence times were 28–120 days. This implies that CH 4 flux may lag changes in water table and temperature which happen on shorter timescales (hours or days). To improve our description of subsurface CH 4 stocks, links between dissolved and bubble CH 4 stocks and peatland CH 4 residence time, coincident measurement of pore water CH 4 concentrations, entrapped gas content and composition, diffusive CH 4 flux, and ebullition are required.