Soils as sources and sinks for atmospheric methane

Abstract

1997. Soils as sources and sinks for atmospheric methane. Can. J. Soil Sci. 77: 167-178. Methane is considered to be a significant greenhouse gas. Methane is produced in soils as the end product of the anaerobic decomposition of organic matter. In the absence of oxygen, methane is very stable, but under aerobic conditions it is mineralized to carbon dioxide by methanotrophic bacteria. Soil methane emissions, primarily from natural wetlands, landfills and rice paddies, are estimated to represent about half of the annual global methane production. Oxidation of atmospheric methane by well-drained soils accounts for about 10% of the global methane sink. Whether a soil is a net source or sink for methane depends on the relative rates of methanogenic and methanotrophic activity. A number of factors including pH, Eh, temperature and moisture content influence methane transforming bacterial populations and soil fluxes. Several techniques are available for measuring methane fluxes. Flux estimation is complicated by spatial and temporal variability. Soil management can impact methane transformations. For example, landfilling of organic matter can result in significant methane emissions, whereas some cultural practices such as nitrogen fertilization inhibit methane oxidation by agricultural soils.Key words: Methane, methanogenesis, methane oxidation, soil, flux measurement Topp, E. et Pattey, E. 1997. Le sol considéré comme source d'émission de méthane dans l'atmosphère. Can. J. Soil Sci. 77: 167-178. Le méthane est considéré comme gaz à effet de serre important : c'est le produit terminal de la décomposition de la matière organique en conditions anaérobies. En l'absence d'oxygène, il est très stable, mais en aérobiose, il est minéralisé en gaz carbonique par les bactéries méthanotrophes. Les émissions de méthane provenant surtout des terres humides naturelles, des décharges et des rizières représenteraient environ la moitié de la production annuelle de méthane dans la planète. Par ailleurs l'oxydation de méthane de l'atmosphère par les sols bien drainés compteraient pour environ 10 % du méthane stocké. Que le sol soit une source ou un puits d'accumulation nette de méthane, dépend des taux relatifs des activités méthanogéniques et méthan-otrophiques. Un certain nombre de facteurs, notamment, pH, Eh, la température et le niveau hydrique du sol, influent sur les populations bactériennes qui transforment le méthane ainsi que sur le flux de méthane dans le sol. On dispose de plusieurs techniques pour mesurer le flux de méthane, mais l'estimation de ces flux est compliquée par leur variabilité dans le temps et dans l'espace. Il y a aussi le mode de conduite du sol : ainsi par exemple, la mise en décharge des matières organiques peut provoquer d'importantes émissions de méthane, mais l'inverse quelques pratiques culturales comme le fumier et la fumure azotée entravent l'oxydation du méthane par les terres agricoles.

Atmospheric methane uptake by tropical montane forest soils and the contribution of organic layers

“…Methane (CH 4 ) is a trace gas with a global warming potential 21 times greater than that of carbon dioxide (CO 2 ) and participates in chemical reactions producing tropospheric ozone (Forster et al 2007;Topp and Pattey 1997). Oxidation processes are the main sink of atmospheric CH 4 , with the reaction of hydroxylradicals (OH) in the troposphere accounting for approximately 90% of annual CH 4 removal (Prather et al 2001).…”

“…Gas diffusivity is considered the primary regulating factor for CH 4 consumption in soils, as the potential consumption of atmospheric CH 4 by high affinity methanotrophs generally exceeds the rate of CH 4 to diffuse from the atmosphere into the soil (Striegl 1993). Soil texture and soil moisture mainly control diffusivity in soils by regulating permeability and gas transport resistance, as CH 4 diffuses 10 4 times faster in air than in water (Dörr et al 1993;Topp and Pattey 1997). Organic layers are considered to affect CH 4 oxidation primarily as gas diffusion barriers because they display little, if any, CH 4 oxidation capacity (Butterbach-Bahl et al 2002a;Maurer et al 2008;Saari et al 1998;Steinkamp et al 2001).…”

High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions

“…Few studies have examined anaerobic oxidation of methane (AOM) in FWW [2][3][4][5] and AOM was largely regarded as inconsequential in these environments until recently. Instead, aerobic methane oxidation was assumed to be the dominant mode of methane consumption in FWW 6 . The reasoning for this assumption is simple: sulphate was long considered the sole oxidant for methane 7 in anoxic environments and sulphate is scarce in freshwater.…”

A Review on Biogas Interception Processes in Municipal Landfill

“…Methanotrophs are inhibited by high soil N; driving attention that the contemporary worldwide increase in atmospheric N deposition will decrease soil CH 4 oxidation. Oxidation of CH 4 by methanotrophic and methylotrophic bacteria occurs in aerobic soils and the magnitude and rate of oxidation are influenced by soil type, aeration, environmental parameters and Nitrogen availability (Topp and Pattey, 1997;Le Mer and Roger, 2001). Application of fertilizer has been shown to inhibit CH 4 oxidation in soil (Steudler et al, 1989;Hutsch, 1998;Tlustos et al, 1998;Kravchenko et al, 2002).…”