Stokes settling and dissolution rate model for marine particles as a function of size distribution

Abstract

A critical analysis of a Stokes settling model for marine particles which takes into account dissolution rate, density, size distribution of the particles, and velocity of vertical advection is proposed. The dissolution rate is considered proportional to the diameter, surface area, or volume of the particles. Coefficients of the model are exclusively calculated from particle size measurements made in 1971–1972 in the western Mediterranean and the Guinea Basin with a modified Coulter counter. The variation of diameters and the settling rates of particles with depth are calculated in a defined surface water column taken between 300 and 800 m to match actual conditions. Known values of the dissolution rate of calcite particles in seawater are used to test the model coefficients. The theoretical influence of dissolution on concentration and size distribution of marine particles is evaluated. Comparison of the model values with weight and particle size data in this depth interval indicates that Stokes settling only applies to particles with sizes greater than 4–5 μm.