Transformations and Cycling of Dissolved Inorganic Carbon

Our understanding of the DIC cycle in aquatic systems began with the development of analytical techniques that allowed for adequate detection and precision of DIC (Dyrssen and Sillen, 1967). When CO2 dissolves in water it can then be hydrated to form H2CO3, which can then dissociate to HC03 and C032- as shown in the following equations  

The HCO3 and CO32 ions also dissociate into the following equilibria  

Temperature-dependent equilibrium constants for carbonate are shown in table 13.1 (Larson and Buswell, 1942). Equations 13.4 and 13.5 can result in more alkaline waters due to the generation of OH- this is typical of what may be found in lakes and streams due to high carbonates in the drainage basin. The percolation of H2O through soils results in the enrichment of CO2 from plant and microbial decay processes forming H2CO3 which can 

In fact, recent work has shown that the export of carbonate alkalinity in the Mississippi River has increased in the past half-century due to significant increases in rainfall and chemical weathering in the Mississippi Basin (Raymond and Cole, 2003). Moreover, it appears that watersheds with forested areas have less alkalinity transport than cropland systems. While the mechanisms of alkalinity export are not well understood, these results have major implications for management of land-use patterns in watersheds as it relates to carbon sequestration issues. 

Other work has shown alkalinity production associated with Mn(IV), Fe(III), and SO42-in an anoxic fjord (Yao and Millero, 1995). 

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