Carbon release from sediments

However, calcium carbonate budget calculations are strongly biased by inexact estimations of calcite production in the surface ocean and of the dissolution of pelagic biogenic calcite in the water column and in sediments above the calcite lysocline. In addition, the uncertainty is enhanced by the difficulty to estimate dissolved inorganic carbon release from sediments. 

In combination with the flux of dissolved organic carbon (DOC), which may add another 20 10 " mol yr (Otto 1996 Table 9.7), a total carbon release from deep-sea sediments of about 120 10 mol yr seems to be the best recent approximation regarding all sources of uncertainty. 

The total carbon release from deep-sea sediments is estimated to be about 120-10 mol yr, but is subject to great uncertainty due to the complexity of processes controlling carbon remobilization. 

Aguilar, L. and L.J. Thibodeaux. 2005. Kinetics of peat soil dissolved organic carbon released from bed sediment to water. Part 1. Laboratory simulation. Chemosphere 58,1309-1318. 

Carbon is released from the lithosphere by erosion and resides in the oceans ca. 10 years before being deposited again in some form of oceanic sediment. It remains in the lithosphere on the average 10 years before again being released by erosion (Broecker, 1973). The amount of carbon in the ocean-atmosphere-biosphere system is maintained in a steady state by geologic processes the role of biological processes is, however, of profound importance... 

Some of the carbon released by decomposition may be washed into rivers and the ocean. Some of it may be taken up by other living things for use in their life processes. Some of it maybe buried in sediments and, over long periods of time, converted to fossil fuels. The burial and conversion of carbon compounds to fossil fuels upsets the balance between photosynthesis and respiration because these processes remove the carbon from the cycle for such long periods of time. Some carbon is also removed from the cycle for longs periods of time when the shells of some small ocean-dwelling... 

Total S content cannot indicate whether increased carbon inputs to sediments cause increased diffusion of sulfate into sediments or restrict reoxidation and release of S from sediments, because the net effect is the same. In a survey of 14 lakes, Rudd et al. (80) did not observe a strong correlation between organic matter content per volume and net diffusive flux of sulfate. However, in English lakes the lowest C S ratios occur in the most productive lakes (24) whether this represents enhanced influx or retarded release is not clear. Among 11 Swiss lakes, ratios of C to S sedimentation rates are relatively constant and substantially below C S ratios in seston net S fluxes... 

None of the pure cultures that produced HFBT have been shown to further metabolize this compound. Bohonos et al. (46) found two further oxidation products, 3-hydroxybenzothiophene and 2,3-dihydrobenzothiophene-2,3-dione in aerobic mixed cultures co-metabolizing dibenzothiophene. Recently, Mormile and Atlas (61) inoculated portions of the filter-sterilized supernatant from a dibenzothiophene-degrading culture with soil and sediment samples and observed the loss of HFBT using a spectroscopic method. Under their aerobic growth conditions, they also observed the release of carbon dioxide from these cultures indicating that these products of dibenzothiophene degradation can be further oxidized. In addition, they observed carbon dioxide production from dibenzothiophene-sulfoxide. 

Some volatile compounds such as methanethiol, dimethylsulfide and dimethyldisulfide have been shown to yield methane when they were added to anaerobic cultures derived from aquatic sediments (70. 71V Kiene et al. (22) showed that methane bacteria and sulfate-reducers competed for dimethyldisulfide when it was added at low concentrations to anaerobic aquatic sediments. They also isolated a methanogen that metabolized dimethyldisulfide to methane and carbon dioxide (72). Recently Oremland et al (22) detected trace amounts of ethane released from anoxic sediment slurries. This could be stimulated by the addition of ethanethiol or diethylsulfide and inhibited by the addition of bromoethanesulfonic acid which specifically inhibits methane bacteria. These results indicated that methane bacteria co-metabolized these two OSC. 

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