Explain the process of buffering that occurs in oceans.

In simple chemical terms it plays out as follows:

When CO2 dissolves in seawater it combines with water to form hydrogen (H+) and bicarbonate (HCO3-) ions:

CO2 + H2O - > H (+) + HCO3 (-)

Some of the hydrogen ions combine with carbonate (CO3 (2-)) ions to form additional bicarbonate ions resulting in a decrease in the former and an increase in the latter:

H (+) + CO3 (2-) - > HCO3 (-)

Therefore, the net effect when is added to seawater is for the concentrations of H+, CO2, and HCO3 - to increase, and the concentration of CO32 - to decrease.

bicarbonate can act as an acid or a base (i. e., donate or accept hydrogen ions) depending on conditions.

Under present-day conditions, these reactions buffer the pH of surface seawater at a slightly basic value of about 8.1 (above the neutral value around 7.0). At this pH, the total dissolved inorganic carbon (DIC ~ 2 mM) consists of approximately 1% CO2, 90% HCO3-, and 9% CO32 - (Figure 2.1). The total boric acid concentration (B (OH) 4 - + B (OH) 3)) is about 1/5 that of DIC. As discussed in section 2.2, increases in CO2 will increase the H+concentration, thus decreasing pH; the opposite occurs when CO2 decreases. We note that isotope fractionation between B (OH) 3 and B (OH) 4-is used for estimating past pH values