title: ¹³⁷Cs in irrigation water and its effect on paddy fields in Japan after the Fukushima nuclear accident.
abstract: There is concern that radiocesium deposited in the environment after the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 will migrate to paddy fields through hydrological pathways and cause serious and long-lasting damage to the agricultural activities. This study was conducted in the Towa region of Nihonmatsu in the northern part of Fukushima Prefecture, Japan, (1) to quantify (137)Cs in stream water used to irrigate paddy fields by separating the dissolved and particulate components in water samples and then fractionating the particulate components bonded in different ways using a sequential extraction procedure, and (2) to determine the amounts of radiocesium newly added to paddy fields in irrigation water relative to the amounts of radiocesium already present in the fields from the deposition of atmospheric fallout immediately after the FDNPP accident. Three catchments were studied, and the (137)Cs activity concentrations in stream water samples were 79-198 mBq L(-1) under stable runoff conditions and 702-13,400 Bq L(-1) under storm runoff conditions. The residual fraction (F4, considered to be non-bioavailable) was dominant, accounting for 59.5-82.6% of the total (137)Cs activity under stable runoff conditions and 69.4-95.1% under storm runoff conditions. The (137)Cs newly added to paddy fields in irrigation water only contributed 0.03-0.05% of the amount already present in the soil (201-348 kBq m(-2)). This indicates that the (137)Cs inflow load in irrigation water is negligible compared with that already in the soil. However, the contribution from the potentially bioavailable fractions (F1+F2+F3) was one order of magnitude larger, accounting for 0.20-0.59%. The increase in the dissolved and soluble radiocesium fraction (F1) was especially large (3.0% to infinity), suggesting that radiocesium migration in irrigation water is increasing the accumulation of radiocesium in rice.
authors.affiliation: Institute of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Natsuki
authors.initials: N
authors.lastname: Yoshikawa
authors.affiliation: Oriental Consultants, Sumitomo Fudosan Nishi Shinjuku Bldg. No. 6, 3-12-1 Honmachi, Shibuya-ku, Tokyo 151-0071, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Obara
authors.affiliation: Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Marie
authors.initials: M
authors.lastname: Ogasa
authors.affiliation: Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Miyazu
authors.affiliation: Institute of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Harada
authors.affiliation: Graduate School for Management of Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Nonaka
mesh_terms: D000383:Agriculture; D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D007564:Japan; D012275:Oryza; D011834:Radiation Monitoring; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D012990:Soil Pollutants, Radioactive; D014875:Water Pollutants, Radioactive
keywords: Fukushima Daiichi Nuclear Power Plant; Irrigation water; Radiocesium; River water; Sequential extraction procedure; Soil