A microscopic simulation of particle flux in ocean waters: Application to radioactive pair disequilibrium

In this paper we relate typical parametrizations of the flux attenuation curve to their corresponding degradation rate and propose an alternative parametrization to model the flux degradation function which is negligible at very large depths, therefore producing a constant residual flux, and remains finite in the euphotic zone. This degradation function is implemented in the simulation and applied to estimate the scavenging of the naturally occurring radioisotopes 234Th and 210Po. We use the results to estimate effective adsorption and desorption rate constants for both isotopes. We found that the degradation rate, rather than the half-life, controls the depth at which the parent and daughter reach equilibrium. Thus, this depth is ruled by a combination of the degradation rate and the particle sinking velocity.