Influences of T, S and PCO2 on the pseudo-homogeneous precipitation of CaCO 3 from seawater: implications for whiting formation

Abstract

The influences of temperature, salinity and P CO 2 on the pseudo-homogeneous nucleation of calcium carbonate from natural seawater were investigated to determine if whitings could be produced by this mechanism under ‘reasonable’ natural conditions. Increasing temperature and salinity substantially raises the P CO 2 at which calcium carbonate nucleation can occur. The saturation state of the water, at which precipitation takes place, is essentially independent (range 20–25 times with respect to calcite) of temperature and salinity, from 25 to 40°C and for S = 35–70 psu. These findings indicate that formation of whitings on the Great Bahama Bank are unlikely to be due to the nucleation of calcium carbonate. However, whitings observed near the Trucial Coast of the Persian Gulf could possibly be the result of direct nucleation of calcium carbonate in waters of lowered P CO 2 associated with phytoplankton blooms.