High activity concentrations of (210)Pb and (7)Be in sediments and their histories

High activity concentrations of (210)Pb and (7)Be, in addition to (137)Cs, were found in a rooftop deposit in Japan. This deposit had activities of about 5 Bq/g from (210)Pb and 3.6 Bq/g from (7)Be, an order of magnitude greater than typically found in field soils and lake and sea bottom sediments. It is clear that under certain conditions aerosol particles can accumulate in deposits with little or no mixing and dilution by silicate materials, and that subsequent processes and factors result in a heterogeneous distribution pattern of activity concentration on the Earth's surface. A simple model suggests that the history of an environmental sample can be estimated by using the activities of (210)Pb and (7)Be.