Spatial Distributions of Inorganic Carbon in Seawaters

CO2 can enter seawater in two ways from the atmosphere and from the breakdown of organic materials in seawater and sediment by organisms. In an aqueous solution, CO2 exists in many forms HCO3, COg, H2CO3, and the sum 

The CO2 system in seawater is an important and complicated balance system in oceans it is composed of some sub-balance systems and is influenced by atmospheric, biological, geologic and other processes. The Pco2 in seawater is an important parameter of the sea s CO2 system and is very sensitive to physicochemical and biological processes in oceans. Its distribution and change are closely related to factors such as water mass and biological activity. 

For a representative estuary, the Changjiang River Estuary can be divided into two sections, namely the inner and outer estuaries. The inner estuary is a region between the limit of the tidal influence and the river mouth the outer estuary is the plume of freshened water which floats on denser coastal seawater and can be traced miles away from the geographical mouth of the 

To sum up, the Pco2 distribution pattern in estuaries results from a combination of various processes the production/degradation/export of organic carbon, the production/dissolution/export of carbonates, the input of dissolved inorganic carbon by vertical mixing processes and/or freshwater runoff, and the thermodynamic effects related to both water temperature variations and water mass mixing. 

Temperature affects the equilibrium constants of dissolved inorganic carbon and, in particular, the solubility coefficient of CO2, so that Pco2 rises by 4% with an increase of 1 °C in temperature. In the sampling region, the surface water temperature decreased from the west to the east, similar to that of Pcos (Fig- 4.5). Thus this was another possible factor causing the Pco2 distribution to show such a pattern in this study. 

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