title: Plutonium isotopes concentration in seawater and bottom sediment off the Pacific coast of Aomori sea area during 1991-2005.
abstract: A radioactivity survey was launched in 1991 to determine the background levels of ²³⁹+²⁴⁰Pu in the marine environment off a commercial spent nuclear fuel reprocessing plant before full operation of the facility. Particular attention was focused on the ²⁴⁰Pu/²³⁹Pu atom ratio in seawater and bottom sediment to identify the origins of Pu isotopes. The concentration of ²³⁹+²⁴⁰Pu was almost uniform in surface water, decreasing slowly over time. Conversely, the ²³⁹+²⁴⁰Pu concentration varied markedly in the bottom water and was dependent upon the sampling point, with higher concentrations of ²³⁹+²⁴⁰Pu observed in the bottom water sample at sampling points having greater depth. The ²⁴⁰Pu/²³⁹Pu atom ratio in the seawater and sediment samples was higher than that of global fallout Pu, and comparable with the data in the other sea area around Japan which has likely been affected by close-in fallout Pu originating from the Pacific Proving Grounds. The ²⁴⁰Pu/²³⁹Pu atom ratio in bottom sediment samples decreased with sea depth. The land-originated Pu is not considered as the reason of the increasing ²³⁹+²⁴⁰Pu concentration and also decreasing the ²⁴⁰Pu/²³⁹Pu atom ratio with sea depth, and further study is required to clarify it.
authors.affiliation: Marine Ecology Research Institute, Head Office, Research and Survey Group, Towa-Edogawabashi Bldg. 7F., 347 Yamabuki-cho, Shinjuku-ku, Tokyo 162-0801, Japan. oikawa@kaiseiken.or.jp
authors.forename: Shinji
authors.initials: S
authors.lastname: Oikawa
authors.forename: Teruhisa
authors.initials: T
authors.lastname: Watabe
authors.forename: Naohiko
authors.initials: N
authors.lastname: Inatomi
authors.forename: Naohiko
authors.initials: N
authors.lastname: Isoyama
authors.forename: Jun
authors.initials: J
authors.lastname: Misonoo
authors.forename: Chiyoshi
authors.initials: C
authors.lastname: Suzuki
authors.forename: Motokazu
authors.initials: M
authors.lastname: Nakahara
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Nakamura
authors.forename: Shigemitsu
authors.initials: S
authors.lastname: Morizono
authors.forename: Seiji
authors.initials: S
authors.lastname: Fujii
authors.forename: Takeya
authors.initials: T
authors.lastname: Hara
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Kido
mesh_terms: D019015:Geologic Sediments / Q000032:analysis*; D009792:Oceans and Seas; D011005:Plutonium / Q000032:analysis*; D011834:Radiation Monitoring; D012623:Seawater / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D014875:Water Pollutants, Radioactive; D011005:Plutonium