title: Catchment-scale distribution of radiocesium air dose rate in a mountainous deciduous forest and its relation to topography.
abstract: A large number of air dose rate measurements were collected by walking through a mountainous area with a small gamma-ray survey system, KURAMA-II. The data were used to map the air dose rate of a mountainous deciduous forest that received radiocesium from the Fukushima Dai-ichi Nuclear Power Plant accident. Measurements were conducted in a small stream catchment (0.6 km(2) in area) in August and September 2013, and the relationship between air dose rates and the mountainous topography was examined. Air dose rates increased with elevation, indicating that more radiocesium was deposited on ridges, and suggesting that it had remained there for 2.5 y with no significant downslope migration by soil erosion or water drainage. Orientation in relation to the dominant winds when the radioactive plume flowed to the catchment also strongly affected the air dose rates. Based on our continuous measurements using the KURAMA-II, we describe the variation in air dose rates in a mountainous forest area and suggest that it is important to consider topography when determining sampling points and resolution to assess the spatial variability of dose rates and contaminant deposition.
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan. Electronic address: andoh.mariko@jaea.go.jp.
authors.forename: Mariko
authors.initials: M
authors.lastname: Atarashi-Andoh
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Koarashi
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Erina
authors.initials: E
authors.lastname: Takeuchi
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Katsunori
authors.initials: K
authors.lastname: Tsuduki
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Syusaku
authors.initials: S
authors.lastname: Nishimura
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsunaga
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D002588:Cesium Radioisotopes / Q000032:analysis*; D065928:Forests; D062406:Fukushima Nuclear Accident; D005843:Geography; D007564:Japan; D011834:Radiation Monitoring
chemical_list: D000396:Air Pollutants, Radioactive; D002588:Cesium Radioisotopes
keywords: Air dose rate; Fukushima Dai-ichi NPP accident; KURAMA-II; Mountainous forest area; Radiocesium deposition