– Japan Experts: Contamination from Fukushima “is almost irreversible” in coastal sediments (ENENews, Nov 17, 2012):
Title: Sedimentation and remobilization of radiocesium in the coastal area of Ibaraki, 70 km south of the Fukushima Dai-ichi Nuclear Power Plant
Authors: Shigeyoshi Otosaka and Takuya Kobayashi, Research Group for Environmental Science, Japan Atomic Energy Agency
Date: 13 November 2012[…] it can be inferred that dissolved radiocesium advected southward from the region adjacent to the 1FNPP and was deposited to the sediment of the study area in the early stage after the accident. The incorporation of radiocesium into sediments was almost irreversible, and higher concentrations of 137Cs were obtained from the finer-grained fraction of sediments. […]
137Cs levels in sediment decreased considerably between June and August, and then remained at the same level until January 2012. This trend indicates that the initial deposition of 137Cs to the sediment had almost ceased by August, and that the incorporation of 137Cs into sediments was almost irreversible. […]
In conclusion […] it can also be inferred that the remarkable decrease in 137Cs level between June and August 2011 (Table 3) was not caused by dissolution of labile 137Cs but by a physical transport (export) of irreversibly bound 137Cs.
[…] Most of radiocesium in the coastal sediments is incorporated into lithogenic fractions, and this incorporation is almost irreversible. Accordingly, the biological availability of sedimentary radiocesium is relatively low, but continuous monitoring of radiocesium inmarine biota is highly recommended because significant amounts of radiocesium have been accumulated in the sediment.