Methane from soils

Denier van der Gon HAC, van Breemen N. Diffusion-controlled transport of methane from soil to atmosphere as mediated by rice plants. Biogeochemistry. 1993 21 177-190. 

The absorption of the ether bis(2-fluoroethoxy)methane from the soil and its translocation in plants in a concentration sufficient to kill insects is a recent discovery heretofore observed only in some selenium compounds and in the insecticidal esters of some polyphosphoric acids (4) Whether this property is shared by other organofluorine compounds will doubtless be determined for the purpose of studying plant metabolism and of evaluating any practical application. 

Holzapfel-Pschorn A, Conrad R, Seiler W. Effects of vegetation on the emission of methane from submerged paddy soil. Plant Soil. 1986 92 223-233. 

Fernandez-Luqueno F, Reyes-Varela V, Cervantes-Santiago F, Gomez-Juarez C, San-tillan-Arias A, Dendooven L.Emissions of carbon dioxide, methane and nitrous from soil receiving urban wastewater for maize Zea mays L.) cultivation. Plant Soil. 2010 331 203-215. DOI 10.1007/slll04-009-0246-0... 

Neue HU. 1997. Eluxes of methane from rice fields and potential for mitigation. Soil Use and Management 13 258-267. 

Methane (CH4) in the atmosphere is an important greenhouse gas. You wonder if this compound is degraded by bacteria that occur in the upper layers of oxic soils. You estimate that the diffusive flux of methane from the atmosphere (present at about... 

Bodelier P. L. E., Hahn A. P., Arth I. R., and Frenzel P. (2000a) Effects of ammonium-based fertilisation on microbial processes involved in methane emission from soils planted with rice. Biogeochemistry 51, 225-257. 

Methane from the atmosphere can be consumed (oxidized) by microbial communities in soils. 

Siller, H. Winter, J. (1998) Degradation of cyanide in agroindustrial or industrial wastewater in an acidification reactor or in a single-step methane reactor by bacteria enriched from soil and peels of cassava. Appl. Microbiol. Biotechnol., 50, 384—389. 

Air samples from soil are usually withdrawn directly with syringes having airtight stopcocks through stainless steel or nylon tubes installed into the soils or headspace inside the closed chambers, as described in the previous section. Methane, one of the target gases, can be analyzed within 6 h of collection by GC-FID. The column and detector parameters are very similar to those set for the analyses of major air components in the atmosphere. Experiments have been conducted by individual teams at different geological locations to measure how soil consumes atmospheric methane, and how soil moisture and temperature control the consumption and production of CH4 and CO2 in it. ... 

Methane and carbon dioxide produced in soils are transported into the atmosphere by diffusion and mass flow via two pathways (1) the aerenchyma tissues of plant roots and stems and (2) flux from soil to the overlying water column (Figure 5.61). Gas exchange in plants is discussed in detail in Chapter 7. Carbon dioxide is highly soluble and undergoes various chemical reactions, and it may be difficult to estimate flux accurately without considering aU associated reactions. Because of the potency (on molecule-to-molecule basis, methane absorbs 25 times as much infrared radiation as carbon dioxide) of methane as greenhouse gas, we will focus our discussion on methane emissions from wetlands. 

Wetlands and rice paddies are major sources of methane and emit approximately up to 50% of annual methane to the atmosphere. Microbial pathways involved in production of methane from wetlands and aquatic systems are discussed in detail in Chapter 5. Until all electron acceptors (oxygen, nitrate, iron and manganese oxides, and sulfate) with higher reduction potentials are exhausted, no methane will be produced. Potentially all these electron acceptors can be present in the same soil profile with electron acceptors with higher reduction potentials utilized in surface layers and the electron acceptors with lower reduction potentials utilized in lower depths (Figure 10.33). 

Emission of CH4 from soils to the atmosphere is a balance between methane oxidation, production, and transport within the soil systems (Chan and Parkin, 2000 Bradford et al., 2001). Methane is released from anaerobic wetland soils to the atmosphere through diffusion of dissolved methane, through ebullition of gas bubbles, and through wetland plants that develop aerenchyma tissue (Figure 16.1). Large portions of methane formed in an anaerobic soil remain trapped in the flooded soil. Entrapped methane can be oxidized to carbon dioxide when the floodwater is drained or when the soil dries. Entrapped methane can escape to the atmosphere immediately after the floodwater is removed or recedes. 

The low solubility of methane in water limits its diffusive transport in the flooded soil, and most methane is oxidized to carbon dioxide. The aerenchyma of plants mediates the transport of air (oxygen) to the roots and methane from the anaerobic soil to the atmosphere. The flux of gases in the aerenchyma depends on concentration and total pressure gradients and internal structure, including openings of the aerenchyma (see Chapter 7 for details). 

Approximately 90% of the methane transport from soils to the atmosphere in rice paddies and freshwater marshes is through aerenchyma portion of roots and stems of the plants. Gases are transported according to their concentration gradient, not only for CH4 but also for N2O (Yu et al.,... 

There are only two important sinks that serve to destroy methane. The first is the oxidation of methane by aerobic bacteria in soils whereas the second and the most important sink is reaction (oxidation) with hydroxyl radicals in the atmosphere. Biological oxidation of methane in soils is responsible for 6-10% of the global source strength. Oxidation dne to the reaction of methane with hydroxyl radicals in the atmosphere, however, accounts for the remaining 90% (Cicerone and Oremland, 1988). An estimated 500 Tg year is removed from the atmosphere each year over 95% of the annual emission is removed through these two primary sinks (Khalil et al., 1992). 

Methane emissions from enteric fermentation and nitrous oxide emissions from soils were the main drivers of GWP. 

Carbene intermediates have also been identified as products of the reduction of polyhalogenated methanes by iron porphyrins in the presence of cysteine [119]. Such a process seems to be of particular interest because of its potential applicability in the treatment of wastes as well as in remediation approaches to removing polyhalogenated methanes from contaminated soils. 

How does sulfate reduce methane emission The methane comes primarily from soil bacteria. The additional sulfates increase the growth of a type of bacteria that uses sulfates to produce energy. This increase, called a bloom, causes the methane-producing bacteria to decrease. These com-... 

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