Downward migration of radiocaesium in organic soils across a transect in Scotland

► In 1986 the Chernobyl accident contaminated soils across Europe with 137Cs. ► In 2008/2010 we measured 137Cs in 8 peaty soils from a transect across Scotland. ► The 137Cs activities were between 2.8 and 14.4 kBq m−2, decay corrected to 1986. ► The mean migration depths of 137Cs were between 8.2 and 17.4 cm. ► Clay minerals alone in the soils did not control the downward migration of 137Cs.