Oceanic Mass Balance of Elements Interactive with Ca, Mg, and

Oceanic Mass Balance of Elements Interactive with Ca, Mg, and C 

Among the four elemental components, carbon, nitrogen, and sulfur represent natural chemical redox couples, because each element occurs both in an oxidized and a reduced state. The process of formation of organic matter by photosynthesis constitutes chemical reduction of C, N, and S from their inorganic 

The net photosynthetic reactions that produce organic matter with the stoichiometric proportions of C, N, S, and P as given above can be written for the mean composition of marine plankton and land plants in a form that balances oxidized inorganic reactants with organic matter and free oxygen as the reaction products. The two reactions are  

In the marine photosynthesis reaction, for convenience, the proportion of sulfur was raised from 1.7 to 2, and for land photosynthesis the proportion of S was rounded up to 1. The proportions of hydrogen and oxygen in organic matter are nearly H 0 = 2 1 this is the reason for the abbreviated chemical notation of organic matter usually written as CH2O. 

Inputs and outputs of calcium, magnesium, and carbon can be balanced for the modern ocean. This balance necessitates reverse weathering reactions in the ocean system in which CO2 consumed in weathering on land is released to the ocean-atmosphere system during the formation of minerals in the ocean. If this were not the case, regardless of juvenile emissions of CO2 to the ocean-atmosphere system, atmospheric CO2 concentrations could be reduced to vanishingly small values in less than 5000 years. 

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