A study of calcium carbonate chemistry in the oceans with emphasis on the effect of dissolved organic matter

Abstract

Through the use of a modification of the Carpenter method for the determination of dissolved calcium and of a combination of the titration alkalinity and graphical methods for the carbonate ion de-termination, the apparent molar solubility product of calcite in sea water was obtained at 15 and 25°C. and a chlorinity range of 0 to 32 0 / (infinity sign) Cl. Aragonite solubility product was measured by a means of Weyl's carbonate saturometer at 15°C, in the same chlorinity range. The calcite results obtained here confirm Wattenberg's value, while the aragonite values are slightly smaller than the values of previous investigators. The average solubility product ratio was 1 .4 for aragonite as compared to calcite. A method for the preparation of double-labeled Ca⁴⁵C¹⁴ O₃ as calcite and aragonite in the laboratory is described. Using radioactive calcium carbonate crystals it was found that the net exchange of both calcium and carbonate in the sea water-crystal mixture was slight in the 8 month period of equilibration which was studied. Among the major constituents of sea water, both sulphate and magnesium appeared to possess the power to reduce the apparent supersaturation of calcium carbonate in sea water. This observation corroborates recent evidence presented by Garrels and Thompson.