Decomposition of organic matter

Sulfur comes mainly from the decomposition of organic matter, and one observes that with the passage of time and of gradual settling of material into strata, the crude oils lose their sulfur in the form of H2S that appears in the associated gas, a small portion stays with the liquid. Another possible origin of H2S is the reduction of sulfates by hydrogen by bacterial action of the type desulforibrio desulfuricans (Equation 8.1) ... 

Methane also is commonly produced by the decomposition of organic matter by a variety of bacterial processes, and the gas is used as a fuel in sewage plants (see Water, sewage). Methane also is called marsh gas because it is produced during the decay of vegetation in stagnant water. 

Putrefaction Biological decomposition of organic matter with the production of ill-smelling products associated with anaerobic conditions. 

Most petroleum scientists believe that crude oil and natural gas formed over millions to tens of millions of years through the decomposition of organic matter buried by sediments. Generally, marine sediments have led to oil and gas, while freshwater... 

Diminished alkalinity, attributable to thermal decomposition of organic matter to acidic compounds... 

Impairment of steam purity, attributable to thermal decomposition of organic matter to volatile compounds this is especially important where steam is used directly in processing food, pharmaceuticals, or beverages... 

It is less conunonly known that methane was one of the original atmospheric gases and is a normal product of the microbial decomposition of organic matter under anaerobic conditions. Bacteria involved in production of methane are unique in their metabolism and other properties. The balanced... 

Fig. 14-6 Profiles of potential temperature and phosphate at 21 29 N, 122 15 W in the Pacific Ocean and a schematic representation of the oceanic processes controlling the P distribution. The dominant processes shown are (1) upwelling of nutrient-rich waters, (2) biological productivity and the sinking of biogenic particles, (3) regeneration of P by the decomposition of organic matter within the water column and surface sediments, (4) decomposition of particles below the main thermocline, (5) slow exchange between surface and deep waters, and (6) incorporation of P into the bottom sediments.

Soil solution is the aqueous phase of soil. It is in the pore space of soils and includes soil water and soluble constituents, such as dissolved inorganic ions and dissolved organic solutes. Soil solution accommodates and nourishes many surface and solution reactions and soil processes, such as soil formation and decomposition of organic matter. Soil solution provides the source and a channel for movement and transport of nutrients and trace elements and regulates their bioavailability in soils to plants. Trace element uptake by organisms and transport in natural systems typically occurs through the solution phase (Traina and Laperche, 1999). 

Organically bound matter (OM). Heavy metals/trace elements may be bound in living organisms, detritus, and organic matter of the soil. The organically bound trace elements or heavy metals are affected by the production and decomposition of organic matter. 

Agren GI, Bosatta E, Balesdent J (1996) Isotope discrimination during decomposition of organic matter a theoretical analysis. Soil Sci Soc Am J 60 1121-1126 Balesdent J (1987) The turnover of soil organic fractions estimated by radiocarbon dating. Sci Total Environ 62 405-408... 

Moore [355] used the solvent extraction procedure of Danielson et al. [119] to determine iron in frozen seawater. To a 200 ml aliquot of sample was added lml of a solution containing sodium diethyldithiocarbamate (1% w/v) and ammonium pyrrolidine dithiocarbamate (1 % w/v) at pH to 4. The solution was extracted three times with 5 ml volumes of 1,1,2 trichloro-1,2,2 trifluoroethane, and the organic phase evaporated to dryness in a silica vial and treated with 0.1 ml Ultrex hydrogen peroxide (30%) to initiate the decomposition of organic matter present. After an hour or more, 0.5 ml 0.1 M hydrochloric acid was added and the solution irradiated with a 1000 W Hanovia medium pressure mercury vapour discharge tube at a distance of 4 cm for 18 minutes. The iron in the concentrate was then compared with standards in 0.1 M hydrochloric acid using a Perkin-Elmer Model 403 Spectrophotometer fitted with a Perkin-Elmer graphite furnace (HGA 2200). 

The anaerobic decomposition of organic matter by fermentation, methanogenesis (methane formation) and sulfate respiration is exemplified in Table 3.2. 

Any of the above-mentioned compounds can be found and even synthesized in soil. The simplest example, methane (CH4), is commonly found in the soil atmosphere, ft is produced during the decomposition of organic matter under anaerobic conditions, which can occur even in aerobic soils. It is interesting to note that methane can not only can be produced in aerobic soils but can also be oxidized by soil bacteria in the same soil. 

Any low-molecular-weight organic compounds are normally a gas at standard temperature and pressure (STP) may also be found in the soil solution. These compounds will be produced as a result of the decomposition of organic matter in soil. Many of these will be readily taken up and used by microorganisms and thus their life spans in the soil solution are short. 

In settings that do not contain oxygen or alternative electron acceptors, methane production is favored. Methane production is the final step in anaerobic decomposition of organic matter. 

In broad terms the decomposition of organic matter under anaerobic conditions is expected to be slower than nnder aerobic conditions becanse the free energy changes for the reactions involved are mnch smaller (Table 4.1 and Fignre 4.3). For example, for the aerobic decomposition of CH2O ,... 

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