Activity coefficients of a simplified seawater electrolyte at varying salinity (5–40) and temperature (0 and 25 °C) using Monte Carlo simulations

Abstract

Mean salt activity coefficients of a simplified seawater electrolyte (Na+, Mg2+, Ca2+, Cl−, SO42−, HCO3−, CO32−) at varying salinity (5–40) and temperature (0–25°C) were estimated by Monte Carlo (MC) simulations, and compared with Pitzer calculations. The MC simulations used experimentally determined dielectric constants of water at different temperatures, and optimal agreement with the experimental data and the Pitzer calculations was achieved by adjusting the ionic radii. The results, together with a previous study of the carbon dioxide system in sodium chloride solution by the authors, suggest that a complete Monte Carlo description of seawater activity coefficients may be achievable using the charged hard sphere approach with a very limited number of fitted parameters (effective ionic radii), in contrast to the large number of fitted parameters required for a Pitzer model.