title: Vertical and lateral transport of particulate radiocesium off Fukushima.
abstract: Transport processes of particulate radiocesium were investigated using a sediment trap deployed at about 100 km east of the Fukushima Daiichi Nuclear Power Plant. A sediment trap was installed at 873 m depth of the station (119 m above the bottom), and time-series sampling of sinking particles was carried out from August, 2011 to June, 2013. The accident-derived radiocesium was detected from sinking particles over two years after the accident. Observed 137Cs flux was highest in September 2011 (98 mBq m(-2) day(-1): decay-corrected to March 11, 2011), and decreased over time with seasonal fluctuations. Particulate fluxes of radiocesium were mainly affected by two principal processes. One was the rapid sinking of radiocesium-bound particles (moderate mode). This mode was dominant especially in the early postaccident stage, and was presumed to establish the distribution of radiocesium in the offshore seabed. Another mode was observed in winter, and secondary transport of particles attributed to turbulence near the seabed increased fluxes of particulate radiocesium (turbulence mode). Although the latter process would not drastically change the distribution of sedimentary radiocesium in the short term, attention should be paid as this key process redistributing the accident-derived radiocesium may cumulatively affect the long-term distribution.
authors.affiliation: Research Group for Environmental Science, Japan Atomic Energy Agency , 2-4 Shiraka-Shirane, Tokai-mura, Ibaraki 319-1195, Japan.
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Otosaka
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nakanishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Yuhi
authors.initials: Y
authors.lastname: Satoh
authors.forename: Hisashi
authors.initials: H
authors.lastname: Narita
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D019015:Geologic Sediments / Q000032:analysis; D007564:Japan; D055848:Nuclear Power Plants; D011834:Radiation Monitoring; D011848:Radioactive Pollutants / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D011848:Radioactive Pollutants