Occurrence of highly radioactive microparticles in the seafloor sediment from the pacific coast 35 km northeast of the Fukushima Daiichi nuclear power plant

To understand the properties and significance of highly radioactive particles in marine environment, we have examined seafloor sediment with a radioactivity ?1200 Bq/kg (dry weight; after decay correction to March 2011) collected 35 km northeast Fukushima Daiichi Nuclear Power Plant (FDNPP). Among 697 separated from sediment, two particles, D1-MAX D1-MID, had total Cs ?56 0.67 Bq (after 2011), respectively. These were characterized variety electron microscopic techniques, including transmission microscopy. The 134Cs/137Cs ratio D1-MAX, 1.04, was comparable that calculated for Unit 2 or 3. consisted mainly Cs-rich microparticle (CsMP) silica glass matrix. data clearly suggested resulted molten core–concrete interaction during meltdowns. In contrast, D1-MID an aggregate plagioclase, quartz, anatase, Fe-oxide nanoparticles as well clay minerals, which adsorbed soluble Cs. likely terrestrial particle been transported by wind and/or ocean currents site FDNPP. fractions 15% 0.36%, respectively, bulk sediment. great impact on movement environment carrying condensed various colloidal desorption depending host phase.