Origin biogenic

About 20% of the World s natural gas is of biogenic origin. Biogenic methane commonly occurs in recent freshwater or marine sediments and results from various bacterial fermentation processes. Typical 813C for methanes from marine sediments... 

According to Rice and Claypool (1981), over 20% of the world s natural gas accumulations are of biogenic origin. Biogenic methane commonly occms in recent anoxic sediments and is well documented in both freshwater enviromnents, such as... 

Aside from Sr, the original biogenic components of calcareous oozes also contain variable and minor amounts of other elements, like Mg, Na and S, all of which affect the solubility of the biogenic phases. Magnesium is especially... 

MicrocrystaUine Silicas. Various microcrystalline (cryptocrystalline) materials such as flint, chert, and diatomaceous earth are found ia nature (see Diatomite). These may arise from amorphous silica, often of biogenic origin, which undergoes compaction and microcrysta11i2ation over geologic time. 

In addition, the linear, biogenic polyamines, spermidine and spermine, originally isolated from human sperm19), have been long known. Their structures are shown below. 

An estimate of the annual methane flux into the atmosphere can be calculated by adding the sinks and the annual increase. These data (Table II) indicate that a flux of 375-475 trillion tons(Tg) per year would be required to account for an annual increase of50-60 trillion tons (7). Estimates of sources of atmospheric methane indicate that up to 83% is biogenic in origin (5). The other abiogenic... 

Probably, iron of biogenic magnetite was originated from hydrothermal solution. It is considered that ferric iron of hydrothermal solution was oxidized by iron oxidizing bacteria to form magnetite. 

A correlation exists between the flux of particles collected by sediment traps and the ( Paxs/ °Thxs) of these particles (Kumar et al. 1995). In pelagic regions, particulate material settling through the deep sea is almost entirely of biogenic origin. A... 

CS2 and COS occur in the atmosphere in significant amounts - CS2, 3.8-4.7 Tg S yr-1, COS, 2.7-3.5 Tg S yr-1 one-fifth to one quarter of these amounts are probably anthropogenic. Biogenic CS2 mainly originates in marine settings - anaerobic sediments (bacteria) and salt marshes with a role for Spartina alterniflora.6,10 Some terrestrial plants produce CS2 and tree roots are another source, usually after cutting or wetting. A tree of central America, Stryphnodendron excelsum. can be detected by its CS2 odor.10... 

Solubilities of the Mg-caldte as a function of MaCOn constant. The solubility is expressed in line with Eq. (8.11) as lAP g-calcite = (Ca2 1 ) (Mg2+) CO 2). The solid curves represent the general trend of results on dissolution of biogenic and synthetic Mg-calcites. The curve fitting the data of Plummer and Mackenzie (1974) is dashed. The various points refer to the results of different researches. (For the origin of the data see Morse and Mackenzie, 1990.) (IAP = ion activity product.)... 

It is doubtful that formation and dissolution of any mineral in low temperature aqueous solutions has been more fully investigated than the magnesian caicite. This mineral is a preponderant carbonate phase, mostly of biogenic origin, in seawater. Fig. 8.8 gives some data on the solubilities of Mg-calcites as a function of MgC03 content. 

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