Carbonate in sediments

Note that this estimate of the annual O2 loss to weathering processes is approximately equal to the estimated annual production of oxygen estimated above. Hence, the weathering of rocks and burial of organic carbon in sediments during their formation are important processes for the oxygen content of the atmosphere. 

The BUSES model provides an estimate of the organic carbon/water partition coefficient (Koc) based on the octanol/water partition coefficient (Kow)- From these data, it is evident that the methyltins are less likely to partition onto organic carbon (in sediments, soils, biota) than are the butyl- and octyltin compormds due to then-lower partition coefficients and higher water solubilities. The 7/oc value can then be used to derive sohds/water partition coefficients in suspended matter, in sediment, and in soil using values of 10%, 5%, and 2% for organie carbon, representing typical organic carbon contents of suspended matter, sediment, and soil, respeetively. 

Various techniques have been used for the determination of organic (and total) carbon in sediments. These include both wet and dry combustion methods which depend on the quantitative conversion of the organic (or total) carbon to carbon dioxide [30-32], In addition, an approximate assay technique reported by Bremner and Jenkinson has been used [36]. 

With the exception of instrumental dry combustion methods [32], the techniques referred to above for the analysis of organic (and total) carbon in sediments are time consuming (e.g. 2-3h). An instrumental technique described by Van Hall and Stenger [33] makes use of a non-dispersive infrared detector and measures the carbon dioxide resulting from the combustion of the carbonaceous compounds. Total and inorganic carbon can be differentiated by the use of different combustion columns and temperatures. 

Chlorinated hydrocarbons and soils content [43,47,48,51,53-63] Ki = Koc Xoc where Koc is the partition coefficient expressed on an organic carbon basis, and Xoc is the mass fraction of organic carbon in sediment a... 

This model places special emphasis on the recovery of reactive metal oxides in the upper layers of the sediment by dissolved oxygen. In other words, the oxidation capacity of dissolved oxygen (DO) is transferred onto metal oxides, which are then buried by further sedimentation. The oxidation capacity is thus shuttled into deeper layers, where it will enhance the anaerobic turnover of organic carbon in sediment layers that could not be maintained by diffusive supply of sulfate alone. A shuttle of oxygen equivalents may also influence the pathways of organic matter decomposition. 

On an average, bacterial carbon in sediments of the Kiel Bight accounted for 0.7 i 0.2% (standard deviation of the mean 76 observations) of the sediment organic carbon. In the literature, higher values have been reported (1.2 %, Dale, 1974 less than 2%,... 

Bird, M. I., and Grocke, D. R. (1997). Determination of the abundance and carbon isotope composition of elemental carbon in sediments. Geochim. Cosmochim. Acta 61, 3413-3423. 

Wolbach, W. S., and Anders, E. (1989). Elemental carbon in sediments determination and isotopic analysis in the presence of kerogen. Geochim. Cosmochim. Acta 53, 1637-1647. 

The distribution of calcium carbonate in sediments with ocean depth shows wide variations. In open ocean basins, where rates of detrital sedimentation are moderate to low, sediments above 3000 meters water depth are generally high in calcium carbonate, whereas sediments below 6000 meters generally have very low calcium carbonate content. Between these depths there is a poor correlation between the weight % calcium carbonate and depth (Smith et al., 1968). Turekian... 

One of the major environmental issues of our time is the impact of anthropogenically generated CO2 on the environment (see Chapter 9 for discussion). The major processes associated with fossil fuel CO2 in the oceans are the uptake of fossil fuel CO2 by the upper ocean, mixing and transport within the ocean, and reaction with calcium carbonate in sediments. In addition, biologic productivity may be influenced by increased Pc02 values- The two major reactions for uptake of CO2 by the oceans, beyond those that would occur for a chemically unreactive gas, are in a simple form ... 

Schidlowski M. (1982) Content and isotopic composition of reduced carbon in sediments. In Mineral Deposits and the Evolution of the Biosphere (eds. H.D. Holland and M. Schidlowski), pp. 103-122. Springer Verlag, Berlin. 

Alperin, M.J., Martens, C.S., Albert, D.B., Suayah, I.B., Benninger, L.K., Blair, N.E., and Jahnke, R.A. (1999) Benthic fluxes and porewater concentration profiles of dissolved organic carbon in sediments from the North Carolina continental slope. Geochim. Cosmochim. Acta 63, 427 148. 

Gustafsson, O., Bucheli, T.D., Kukulska, Z., Andersson, M., Largeau, C., Rouzaud, J.N., Reddy, C.M., and Eglinton, T.I. (2001) Evaluation of aprotocol for the quantification of black carbon in sediments, soils and aquatic particles. Global Biogeochem. Cycles 15, 881-890. 

Koepfler, E. T., Benner, R., and Montagna, P. A. (1993). Variability of dissolved organic carbon in sediments of a seagrass bed and an unvegetated area within an estuary in southern Texas. Estuaries 16, 391-404. 

Water column fluxes and the burial of organic carbon in sediments... 

Archer D. E. (1996a) An atlas of the distribution of calcium carbonate in sediments of the deep sea. Global Biogeochem. 

Figure 15.18. Comparison of global reservoirs and their residence times (t in years) (Example 15.3). The reservoirs of the atmosphere, of surface fresh waters, and of living biomass are significantly smaller than the reservoirs of sediment and marine waters and are thus more susceptible to distuibance. For example, the combustion of fossil fuel (from the reservoir of organic carbon in sediments) will have an impact on the smaller reservoirs CO2 in the atmosphere will be markedly enlarged. This combustion also fixes some N2 to NO and NO2 sulfur, associated with the organic carbon, introduces CO2 into the atmosphere. These nitrogen and sulfur compounds are washed out relatively rapidly into soil and aquatic ecosystems. The total groundwater reservoir may be twice that of surface fresh water but, however, is less accessible. (From Stumm, 1986.)...

Berner, R.A., 1971. Bacterial processes effecting the precipitation of calcium carbonate in sediments. In O.P. Bricker (Editor), Carbonate Cements. Johns Hopkins University Studies in Geology, No. 19, Johns Hopkins, Baltimore, pp. 247—251. 

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