Spatial variation in sedimentary radioactive cesium concentrations in Tokyo Bay following the Fukushima Daiichi Nuclear Power Plant accident

• Published in: Chemosphere (Oxford) 2019-11, Vol.235, p.550-555
• Main Authors: Kubo, Atsushi, Tanabe, Kai, Ito, Yukari, Ishimaru, Takashi, Arakawa, Hisayuki, Kanda, Jota
• Format: Article
• Language: English
• Subjects: Cesium-137; CsMP; FDNPP; Sediment; Tokyo bay
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2019.06.215

Cesium-137 concentrations in sediment (137Cs) at Tokyo Bay were measured at 26 stations during 2017. Average 137Cs concentrations at the Arakawa river mouth (117 ± 46 Bq kg−1) were approximately six times higher than those of the other stations in the bay (20 ± 16 Bq kg−1). There were radiocesium-bearing microparticles in the bay sediment as well as in suspended matter of Fukushima coastal waters. Radioactivity of radiocesium-bearing microparticles was estimated to be 0.12 Bq. However, the contributions of radiocesium-bearing microparticles to each 137Cs concentration of the bulk sample were low; 3% was the maximum. The 137Cs inventory in sediment at the entire bay was 0.67 TBq, showing that a large amount of 137Cs was supplied to the bay from the river following the Fukushima Daiichi Nuclear Power Plant accident. Approximately 9.2% of the 137Cs which was fallout in the drainage basin has already flowed into the bay from the watershed, which is approximately 3.2 times higher than that of a previous estimate. •The radiocesium concentrations in the sediment of river mouth and Tokyo Bay were measured at 26 stations in 2017.•Radiocesium-bearing microparticles contributions to each 137Cs concentration of the bulk sediment sample were very low.•The 137Cs inventory in the sediment was 0.67 TBq which is approximately 3.2 times higher than that of a previous estimate.