Biogeochemical cycling in an organic-rich coastal marine basin—I. Methane sediment-water exchange processes

Methane emissions from beaver ponds: Rates, patterns, and transport mechanisms

“…This is not the first time that a relationship between pressure changes and methane release patterns has been reported. Several studies have indicated that in marine sediments, changes in hydrostatic pressure that were associated with diurnal tidal changes had a profound impact on gas bubble release rates [Martens and Klump, 1980;Chanton and Martens, 1988]. In the tidal freshwater sediments of North Carolina, for example, maximum bubble release occurred during ebb fides when the hydrostatic pressure was lowest.…”

“…However, the data suggest that these relatively small fluctuations in atmospheric pressure were sufficient to directly affect the formation and release of gas bubbles from the beaver pond sediments. This can be explained by the fact that gas bubbles in the sediments generally occupy vertical tubes, ranging in diameter from a few millimeters to > 2 cm [Martens and Klump, 1980]. Decreases in atmospheric pressure would result in an expansion of the gas bubble volume in the sediments which, as a result of the vertical tube structure, would be favored in the vertical direction.…”

“…The net amount of methane released to the atmosphere depends on the ratio of methane production versus methane consumption, which in turn is largely dependent on the release mechanism of methane from the sediments (i.e., molecular diffusion versus gas bubble flux). Larger bubble flux to diffusive flux ratios result in a higher proportion of the produced methane reaching the water-atmosphere interface, since gas bubbles are known to "bypass" the oxidizing effect of the sediments and overlying water column [Martens and Klump, 1980;Crill et al, 1988a;Chanton et al, 1989]. The ratio of methane emissions in the form of gas bubbles to diffusive methane flux is therefore expected to govern the portion of the produced methane that eventually will be released from a wetland system.…”

Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

“…In open oceans, CH 4 sources in shallow water depths are provided by microbial subsurface CH 4 generation taking place in zooplankton guts, the oxygen-deficient interior of particles, or under phosphate-limiting conditions (Karl et al, 2008;Damm et al, 2010). In waters overlying continental shelves, however, the organic-rich sediment serves as a major source of CH 4 in the water column compared to net production in the mixed layer (Martens and Berner, 1974;Martens and Klump, 1980;Reeburgh, 2007). The shallow-water [CH 4 ] can also be elevated due to gas seepages and/or oil spills (Bernard et al, 1976;Reed and Kaplan, 1977;Rehder et al, 1998Rehder et al, , 2002Kessler et al, 2011;Gülzow et al, 2013) and advection of CH 4 -rich freshwaters (Sackett and Brooks, 1975;Cline et al, 1986;Zhang et al, 2008).…”

Leakage and Sepage of CO2 from Geologic Carbon SequestrationSites: CO2 Migration into Surface Water

“…Within this larger area, ~120 bubble plumes within a 6500 m 2 area have been observed. At Cape Lookout Bight, a marine basin on the Outer Banks of North Carolina, USA, shallow sediment pore waters become saturated with methane during the summer and ebullition occurs during low tide due to reduction in hydrostatic pressure (Martens and Klump, 1980). Martens and Klump (1980) estimated that ~15% of the methane in the Rev.…”