Spatial variations of low levels of 134Cs and 137Cs in seawaters within the Sea of Japan after the Fukushima Dai-ichi Nuclear Power Plant accident

Our method based on low background gamma-spectrometry enabled the measurement of low radiocesium concentrations in only 20 L of seawater. In May 2011 after deposition of radiocesium, Cs-134 concentration in surface water within the Sea of Japan was confirmed to be significantly small ( <0.1-1 mBq/L) by the method. The concentration was not detected (< 0.1 mBq/L) below 50 m depth. The Fukushima-derived radiocesium migrated from the surface water of the Sea of Japan without advection to below the thermocline. (C) 2013 Elsevier Ltd. All rights reserved.