OCEAN CARBONATE CHEMISTRY: THE AQUATIC CHEMISTRY FUNDAMENTALS

摘要

Some of the main questions we consider when studying the global carbon cycle are the exchange of CO2 between the ocean and atmosphere and internal redistribution of carbon species within the ocean due to uptake and remineralization of organic matter and calcium carbonate. A schematic representation of these processes is shown in Figure 1. When CO_2 evades from or invades to the ocean it changes the equilibrium that exists between the species of dissolved inorganic carbon (H_2CO_3, HCO_3~- and CO_3~(2+)) already there. Some of the CO_2 is taken75 up by phytoplankton to make algal protoplasm. Some CO_3~(2+) reacts with Ca~(2+) and is taken up in the form of calcium carbonate shells. Both organic matter and CaCO3 are contained in the particles that sink from the surface ocean into the deep sea. The biologically driven fluxes are called the "Biological Pump". These particles are remineralized through respiration of the organic carbon and solubilization of the CaCO3. The reactions control the distribution of carbonate species and pH in the deep sea. The pH of seawater is a master variable that reflects the net effect of all acid and base producing aquatic geochemical processes. Some of these particles reach the sediments where their input drives an extensive set of reactions termed sedimentary diagenesis.