Factors affecting the distribution of natural and anthropogenic radionuclides in the coastal Burullus Lake

•226Ra and 232Th are uniformly distributed in Burullus Lake.•Increasing salinity increases the adsorption of 137Cs and solubilization of 40K in sediment.•Sediment with high organic matter content traps 137Cs and 40K.•137Cs and 40K are not associated with the same particulate material.

In the present study, measurements of naturally occurring radioactive materials and 137Cs activity in sediment were conducted for locations covering the entire Burullus Lake in order to gather information about radionuclides mobility and distribution. Low-background γ-spectrometry was employed to determine the activity concentrations of water and sediment samples. The activity concentrations of 226Ra and 232Th are close to uniform distribution in the lake environment. Among the different physical and chemical characteristics measured for water and sediment, only salinity and total organic matter content have the potential to affect the mobility of 137Cs and 40K. The results suggest that these two radionuclides are attached to different mobile particulates. Increasing salinity tends to strengthen the adsorption of 137Cs and solubilization of 40K in sediment. On the other hand, sediment with high organic matter content traps 137Cs and 40K associated particulates to bottom sediment.