Use of ²¹⁰Pb technique for calculating sedimentation rate in the Ba Lat coastal area (Red river)

In implementing the 2020-2021 Ministerial-level research project ^Research on the use of nuclear and isotope techniques to identify the origin and history of pollution in the coastal ecosystem of the Red River estuary^, we have taken sediment cores in the coastal area of Ba Lat estuary (Red River). The cores were taken in Xuan Thuy National Park area, sliced into sample slices and numbered from the top to the bottom and then analyzing for radionuclides (U, Th, ²²⁶Ra, ¹³⁷Cs and ²¹⁰Pb. Based on the analysis results, we have tried to use computational dating models to determine the age and sedimentation rate for each sediment core. This report presents the results of applying computational models to the sediment core BL13 that could provide a general methodology for determining the age and the sedimentation rate of the sediment cores taken in the coastal area of Ba Lat estuary. Results show that CRS model probably is the best model for determining the sedimentation rate. For the sediment core BL13, the use of the Composite model by adjusting the results of the CRS model in combination with the time marker of August 1971 (the time of the historical flood event on the Red River) seems to give the most reasonable results. The average sedimentation rate at the BL13 site before 1960 was about 0.5 cm/year, has increased significantly from 1960, up to the highest value of 1.5 cm/year in the 1970s and then decreased to about 1.0 to 1.2 cm/year from the 1980s to the present. The change in the sedimentation rate could be caused by the main flow changes and large floods on the Red River in the years from 1960 to 1980. (author)