title: Assessment of dry and wet atmospheric deposits of radioactive aerosols: application to Fukushima radiocaesium fallout.
abstract: The Fukushima Dai-ichi nuclear accident led to massive atmospheric deposition of radioactive substances onto the land surfaces. The spatial distribution of deposits has been estimated by Japanese authorities for gamma-emitting radionuclides through either airborne monitoring surveys (since April 2011) or in situ gamma-ray spectrometry of bare soil areas (since summer 2011). We demonstrate that significant differences exist between the two surveys for radiocaesium isotopes and that these differences can be related to dry deposits through the use of physically based relationships involving aerosol deposition velocities. The methodology, which has been applied to cesium-134 and cesium-137 deposits within 80-km of the nuclear site, provides reasonable spatial estimations of dry and wet deposits that are discussed and compared to atmospheric numerical simulations from the Japanese Atomic Energy Agency and the French Institute of Radioprotection and Nuclear Safety. As a complementary approach to numerical simulations, this field-based analysis has the possibility to contribute information that can be applied to the understanding and assessment of dose impacts to human populations and the environment around Fukushima.
authors.affiliation: Institute for Radiological Protection and Nuclear Safety (IRSN), Environmental Research Division, BP 3-13115 St-Paul-lez-Durance Cedex, France.
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Gonze
authors.forename: Philippe
authors.initials: P
authors.lastname: Renaud
authors.forename: Irène
authors.initials: I
authors.lastname: Korsakissok
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kato
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Hinton
authors.forename: Christophe
authors.initials: C
authors.lastname: Mourlon
authors.forename: Marie
authors.initials: M
authors.lastname: Simon-Cornu
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000396:Air Pollutants, Radioactive / Q000032:analysis*; D001272:Atmosphere; D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D006801:Humans; D007564:Japan; D011834:Radiation Monitoring / Q000379:methods*; D013051:Spectrometry, Gamma / Q000379:methods
chemical_list: D000336:Aerosols; D000396:Air Pollutants, Radioactive; D002588:Cesium Radioisotopes