The best way to describe the kinetics of the uptake of radioisotopes from sea water by bottom sediments and suspended solid matter is by molecular diffusion. The basic diffusion laws can be applied for finding the important parameter of the diffusion, the diffusion coefficient, which will characterize the migration of radioisotopes in sediments and the kinetics of the sorption into solid suspended matter. A theoretical approach is made for several situations, for which the relation between concentration with time and distance, or total uptake with time is calculated.
Duursma, E. K., & Hoede, C. (1967). Theoretical, experimental and field studies concerning molecular diffusion of radioisotopes in sediments and suspended solid particles of the sea Part A: Theories and mathematical calculations. Netherlands Journal of Sea Research, 3(3), 432-457. https://doi.org/10.1016/0077-7579(67)90013-0