Chapter 10 - Solubility of Carbon Dioxide in Natural Systems

Abstract

This chapter focuses on the basic relationships of CO2 in natural waters and investigates the “CO2 utilizing” processes in the environment. In low-mineral freshwaters that have low buffer capacity, atmospheric CO2 has a significant influence on the pH. However, the effect of increased atmospheric CO2 composition on the pH of seawater is small because of its large buffering capacity. Approximately 98% of the carbon in the ocean–atmosphere system is in the oceans in the form of dissolved carbon and calcite. Calcite, with its vast reservoirs on the ocean floor, plays a major role in the oceanic CO2 balance and acts as an effective buffer against pH changes. Thus, the change in pH is small because CO2 or other acids dissolve in the ocean or fresh waters with a calcite buffer. The lowering of pH in the sea causes dissolution of coral material and inorganic chemical acidification, while in natural aqueous systems it causes dissolution of solid calcium carbonate. The biological impact of such increased acidification of sea and dissolution of coral matter could be detrimental and irreversible because the timescales of physical dissolution and biological recovery are different. The dissolution and precipitation processes of aqueous CaCO3 solutions are controlled by acid–base chemistry, and these processes are thermodynamically driven.