A Kinetic Model for the Chemical Composition of Sea Water

Abstract

The thermodynamic ocean of the Sillen school offers little incentive to those who search the sedimentary record for evidence of changes in ocean chemistry during Cenozoic time. Their models predict a uniform chemical composition. However as the sediments presently accumulating in the ocean show little evidence of equilibration with the overlying water, the possibility that kinetic factors play an important role must be seriously explored. Such a model is presented in this paper. Material balance restrictions are substituted for some of the usual chemical equilibria. The role of organisms is shown to be dominant for at least some of the important components of sea salt (i.e., C, N, P, Si, …). If, as proposed here, the chemistry of sea water is dependent on rates of supply of individual components, the rate of vertical mixing in the sea, and the type of material formed by organisms, then substantial changes in the chemical composition have almost certainly taken place. Several means by which such changes might be reconstructed from chemical and isotopic measurements on marine sediments are discussed.