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

Following the accident at the Chernobyl nuclear power plant in 1986, radioactive materials including (137)Cs were distributed over large parts of the former Soviet Union and Europe. Due to the relatively long physical half-life of (137)Cs (30.1 y) measurable activity concentrations can still be observed in the natural environment. We have determined the depth distribution of (137)Cs from the testing of nuclear weapons in the atmosphere and Chernobyl, in eight highly-organic soils along an approximately east to west transect across the Central Highlands of Scotland. The (137)Cs activity concentrations in the soil profiles, corrected for radioactive decay to May 1986, were between 2.8 and 14.4 kBq m(-2). There were differences in the pattern of distribution of (137)Cs in the soil profiles. The mean migration depth of (137)Cs in the soil profiles was 12.2 cm with a range between 8.2 and 17.4 cm. Quantitative mineralogical analysis of the ash obtained after heating the soil to 400 °C indicated that clay minerals alone did not have a prime role in controlling the migration of (137)Cs down the profile.