[en] Highlights: • Equilibrium in radionuclide partition between water and sediment seldom found in the sea. • Differences between suspended matter and bed sediment kd highlighted. • One step and two step kinetic models performances compared. • Single layer and multi-layer models compared. • Formulation to deal with changes in salinity and pH provided. - Abstract: The behavior of marine distribution coefficients is analyzed with the help of numerical experiments and analytical solutions of equations describing kinetic models for uptake/release of radionuclides. The difficulties in measuring true k_d in a marine environment perturbed by an external radionuclide source are highlighted. Differences between suspended matter and bed sediment k_d are analyzed. The performances of different kinetic models (1-step/2step; single-layer/multi-layer) are studied in model/model and model/experiment comparisons. Implications for the use of models to assess radioactive contamination after an emergency are given; as well as recommendations when k_d data are compiled in order to create a useful database.