Southwest Intrusion of 134Cs and 137Cs Derived from the Fukushima Dai-ichi Nuclear Power Plant Accident in the Western North Pacific

• DOI: 10.1021/es403686v
• Publication Date: 2014-02-28T10:40:21Z
• Authors: Hideki Kaeriyama; Yugo Shimizu; Daisuke Ambe; Masachika Masujima; Yuya Shigenobu; Ken Fujimoto; Tsuneo Ono; Kou Nishiuchi; Takeshi Taneda; Hiroaki Kurogi; Takashi Setou; Hiroya Sugisaki; Tadafumi Ichikawa; Kiyotaka Hidaka; Yutaka Hiroe; Akira Kusaka; Taketoshi Kodama; Mikiko Kuriyama; Hiroshi Morita; Kaoru Nakata; Kenji Morinaga; Takami Morita; Tomowo Watanabe
• Keywords: Mode water; Caesium; Deposition; Radioactive decay

Enormous quantities of radionuclides were released into the ocean via both atmospheric deposition and direct release as a result Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident. This study discusses southward dispersion FNPP-derived radioactive cesium (Cs) in subsurface waters. The southernmost point where we found (134)Cs (1.5-6.8 Bq m(-3)) was 18 °N, 135 °E, September 2012. potential density at peaks (100-500 m) increased water column inventories (137)Cs between 0 500 m after winter 2011-2012 suggested that main mass containing Cs North Pacific Subtropical Mode Water (NPSTMW), formed convection. We estimated amount core waters western part NPSTMW to be 0.99 PBq (decay-corrected on 11 March 2011). accounts for 9.0% from FNPP, with our estimation revealing considerable has been transported subtropical region by formation circulation mode water.