Carbon reservoirs exchange processes

Budgets and cycles can be considered on very different spatial scales. In this book we concentrate on global, hemispheric and regional scales. The choice of a suitable scale (i.e. the size of the reservoirs), is determined by the goals of the analysis as well as by the homogeneity of the spatial distribution. For example, in carbon cycle models it is reasonable to consider the atmosphere as one reservoir (the concentration of CO2 in the atmosphere is fairly uniform). On the other hand, oceanic carbon content and carbon exchange processes exhibit large spatial variations and it is reasonable to separate the... 

The most abundant isotope is which constitutes almost 99% of the carbon in nature. About 1% of the carbon atoms are There are, however, small but significant differences in the relative abundance of the carbon isotopes in different carbon reservoirs. The differences in isotopic composition have proven to be an important tool when estimating exchange rates between the reservoirs. Isotopic variations are caused by fractionation processes (discussed below) and, for C, radioactive decay. Formation of takes place only in the upper atmosphere where neutrons generated by cosmic radiation react with nitrogen ... 

The free 14C atoms formed in the atmosphere become oxidized and form 14C02 which is rapidly mixed throughout the atmosphere (Libby, 1952). This 14C then becomes incorporated into other reservoirs such as the biosphere, as plants fix carbon during the process of photosynthesis the exchange between the atmosphere and the surface ocean is estimated to take approximately 5 y (Broecker and Peng, 1982). 

A 41Ca/ 40Ca equilibrium ratio is maintained in living organisms by exchange and metabolic processes. In contrast to 14C dating, where the death of an animal or plant and the isolation of a sample from one of the carbon reservoirs constitutes the t = 0 event (0 B.P.), the t = 0 event in the 41Ca... 

Major efforts have been made to sharpen this sketch of the global carbon cycle. In part such work consists of quantitative system modelling fe.g., Bolin, 1981), where the chief gains derive from the need to grasp and quantify the nature of the various exchange processes. For the rest, the effort is directed primarily towards actual measurement of the fluxes, or of reservoir content (e.g., Woodwell et al., 1978 Ajtay et al., 1979 Olson, 1982). 

Salinity is essential for all chemical processes. It directly affects polymer viscosity, and it determines the type of microemulsion a surfactant can form. Salinity effects in waterflooding, in both sandstone and carbonate reservoirs, have recently drawn research interest. This chapter briefly discusses sahnity and ion exchange. At the end of this chapter, the sahnity effects on waterflooding in sandstone and carbonate reservoirs are summarized. 

The carbon reservoirs described in the preceding sections are coupled to each other by a variety of exchange processes. The resulting total network... 

Figure 1 Major global reservoirs Involved in active production, exchange and cycling of organic carbon. Reservoir sizes are shown in Gt carbon (1 GtC = 10 g C). Numbers in parentheses are based on 1980s values numbers without parentheses are estimates of the pre-anthropogenic values. Fluxes primarily mediated by biological reactions are shown with dashed arrows physical transport processes are shown with solid arrows. (Modified after Siegenthaler and Sarmiento (1993) and Hedges and Oades (1997).)...

Information on the sources and sinks of CO2 can be obtained from variations of carbon isotopes. Carbon-13, a stable isotope, comprises approximately 1% the total inventory of carbon. Different carbon exchange processes have different degrees of fractionation or discrimination against the heavier isotope, so that the variations in the ratio of C C in the atmospheric terrestrial and oceanic carbon reservoirs provide additional information about the sources and sinks of atmospheric CO2. 

An important stage in understanding the processes of C02 exchange between biospheric reservoirs is study of the laws of the development of various ecosystems in pre-industrial epochs, when there was little human involvement. Natural carbon fluxes between the atmosphere, oceans, land ecosystems, and inland water bodies... 

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