title: Iodine isotopes in precipitation: Four-year time series variations before and after 2011 Fukushima nuclear accident.
abstract: Rainwater samples were collected monthly from Fukushima, Japan, in 2012-2014 and analysed for (127)I and (129)I. These are combined with previously reported data to investigate atmospheric levels and behaviour of Fukushima-derived (129)I before and after the 2011 nuclear accident. In the new datasets, (127)I and (129)I concentrations between October 2012 and October 2014 varied from 0.5 to 10 μg/L and from 1.2 × 10(8) to 6.9 × 10(9) atoms/L respectively, resulting in (129)I/(127)I atomic ratio ranges from 3 × 10(-8) to 2 × 10(-7). The (127)I concentrations were in good agreement with those in the previous period from March 2011 to September 2012, whereas the (129)I concentrations and (129)I/(127)I ratios followed declining trends since the accident. Although (129)I concentrations in five samples during the period of 2013-2014 have approached the pre-accident levels, (129)I concentrations in most samples remained higher values in winter and spring-summer. The high (129)I levels in winter and spring-summer are most likely attributed to local resuspension of the Fukushima-derived radionuclide-bearing fine soil particles deposited on land surfaces, and re-emission through vegetation taking up (129)I from contaminated soil and water, respectively. Long-term declining rate suggests that contribution of the Fukushima-derived (129)I to the atmosphere would become less since 2014.
authors.affiliation: Scottish Universities Environmental Research Center, East Kilbride, G75 0QF, UK; Fukushima University, Fukushima, 960-1296, Japan. Electronic address: s.xu@suerc.gla.ac.uk.
authors.forename: Sheng
authors.initials: S
authors.lastname: Xu
authors.affiliation: Center for Nuclear Technologies, Technical University of Denmark, 4000, Roskilde, Denmark; SKLLQG, Xi'an AMS Center, Institute of Earth Environment, CAS, Xi'an 710061, China.
authors.forename: Luyuan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Scottish Universities Environmental Research Center, East Kilbride, G75 0QF, UK.
authors.forename: Stewart P H T
authors.initials: SPHT
authors.lastname: Freeman
authors.affiliation: Center for Nuclear Technologies, Technical University of Denmark, 4000, Roskilde, Denmark.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Hou
authors.affiliation: Fukushima University, Fukushima, 960-1296, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Watanabe
authors.affiliation: Scottish Universities Environmental Research Center, East Kilbride, G75 0QF, UK.
authors.forename: David C W
authors.initials: DCW
authors.lastname: Sanderson
authors.affiliation: Scottish Universities Environmental Research Center, East Kilbride, G75 0QF, UK; Fukushima University, Fukushima, 960-1296, Japan.
authors.forename: Alan
authors.initials: A
authors.lastname: Cresswell
authors.affiliation: Fukushima University, Fukushima, 960-1296, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yamaguchi
mesh_terms: D062406:Fukushima Nuclear Accident; D007456:Iodine Isotopes / Q000032:analysis*; D007457:Iodine Radioisotopes / Q000032:analysis*; D007564:Japan; D011834:Radiation Monitoring / Q000379:methods*; D011891:Rain; D013997:Time Factors; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D007456:Iodine Isotopes; D007457:Iodine Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: (129)I/(127)I; Fukushima nuclear accident; Fukushima-derived (129)I; Long-term variation; Rainwater