Natural radionuclides as tracers of coastal sediment dynamics in El Confital Bay (Spain): Spatial distribution and relationships with sediment characteristics

Erosion and accumulation of coastal areas have become an increasing concern in recent years since they can result in important social and economic problems. In this framework, natural radionuclides have emerged as an alternative tool to study coastal sediment transport and help with the management of the littoral zone. However, there is still a lack of knowledge on how these radionuclides can be applied as tracers of coastal sediment dynamics and how the sediment characteristics can influence this use. Thus, a methodology is presented in this work to use natural radionuclides as tracers of coastal erosion, transport and accumulation of sediments. For this purpose, the spatial distributions of 226Ra, 228Ra, 40K and unsupported 210Pb (210Pbex) in two periods of time were analysed and compared in a coastal area with diverse marine dynamics. The results showed that 226Ra, 228Ra and 40K identified the different sediment erosion, transport and accumulation occurring in the study region. In addition, it was found that changes in the activity concentrations of the samples were mostly related to variations in their mineralogical composition. Finally, the activity concentration values of 210Pbex made it possible to trace the areas where accumulation due to the sedimentation of aerosol particles in the seabed is favoured. These results highlight the suitability of natural radionuclides to study coastal sediment transport.