A Multi-Media Coupled Model for Radionuclide Migration in Coastal Environments: Integrating Suspended Particles and Sediment Dynamics

Accurate prediction of radionuclide migration in coastal zones is critical for nuclear risk management. This study proposes a multi-media coupled model to address the limitations of conventional approaches that neglect suspended particles and sediment interactions. This study develops a multi-media coupled model to address these limitations by integrating hydrodynamic transport, adsorption-desorption kinetics, and sediment dynamics. Four key processes are explicitly quantified: (1) dissolved-phase transport in seawater, (2) adsorption-desorption on suspended particles, (3) sediment-phase retention, and (4) pore-water diffusion. The model was validated using field data from a coastal nuclear power plant discharging 137 Cs, achieving a high correlation with monitoring results (R 2 =0.81) and reducing prediction errors by 74% compared to single-phase models. Sensitivity analysis revealed that increasing adsorption-desorption rates by 10-fold confined dissolved-phase concentrations to near-source areas while expanding adsorbed-phase distributions in suspended particles by 2.3-fold. This framework provides a robust tool for simulating radionuclide fate in complex marine environments, with direct applications in coastal nuclear safety assessments. • Developed a multi-media coupled model for radionuclide migration in marine environments. • Applied to a coastal nuclear power plant with excellent field data agreement. • Demonstrated that adsorption-desorption rates critically affect radionuclide distribution.