The dataset details radioisotope concentrations (210Pb, 214Pb, 137Cs, 241Am) of 1358 down core soil samples collected from 19 saltmarshes across the UK between 2018 -2021. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1 Full details about this dataset can be found at https://doi.org/10.5285/a85756f9-2685-4ec4-ac44-3210425ba70e
