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

•High activity concentrations of 210Pb (5 Bq/g) and 7Be (3.6 Bq/g) were found in rooftop sediments in Japan.•Activity is an order of magnitude greater than in field soils and lacustrine and marine sediments.•The sample history is modeled using both nuclides.

High activity concentrations of 210Pb and 7Be, in addition to 137Cs, were found in a rooftop deposit in Japan. This deposit had activities of about 5 Bq/g from 210Pb and 3.6 Bq/g from 7Be, 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 210Pb and 7Be.