Abstract
A sediment trap experiment was conducted between August 2011 and July 2013 and sinking particles were collected at 100 km east of the Fukushima Daiichi Nuclear Power Plant. Particulate fluxes of radiocesium were mainly affected by two principal processes. One was a rapid sinking of radiocesium-bound particles (vertical mode). This mode was dominant especially in the early post-accident stage, and was presumed to establish the distribution of radiocesium in the offshore seabed. Another was the secondary transport of particles attributed to turbulence near the seabed and was observed in winter (lateral mode). Although the latter process would not drastically change the distribution of sedimentary radiocesium, attention should be paid as this key process redistributing the accident-derived radiocesium over a long duration.
