The solubility of CaCO 3 in seawater at 2°C based upon in-situ sampled pore water composition

Abstract

Analyses of the concentration product (Ca 2+) × (CO 3 2−) in the pore waters of marine sediments have been used to estimate the apparent solubility products of sedimentary calcite ( K′ SP c ) and aragonite ( K′ SP a ) in seawater. Regression of the data gives the relation In K′ P SP c = 1.94 × 10 −3 δP − 14.59 The 2°C, 1 atm value of K′ SP c is, then, 4.61 × 10 −7 mol 2 l −2. The pressure coefficient yields a Δ V r at 2°C of −43.8 cm 3 atm −1. A single station where aragonite is present in the sediments gives a value of K′ SP a = 9.2 × 10 −7 (4°C, 81 atm). The calcite data are very similar to those determined experimentally by Ingle et al. (1973) for K′ SP c at 2°C and 1 atm. The calculated Δ V r is also indistinguishable from the experimental results of Ingle (1975) if Δ V r is assumed to be independent of pressure.