Distributions of radiocesium and radium isotopes in the western Bering Sea in 2018

Abstract

We examined the spatial variations in radiocesium (134Cs and 137Cs) and radium (226Ra and 228Ra) concentrations (activities) in and around the western Bering Sea in August 2018. 134Cs concentrations in the surface seawater samples were 1.1–2.0 mBq/L, decay-corrected to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident date. The northward slope current-dominated water of the Bering Sea exhibited higher 134Cs concentrations (345 Bq/m2 of the column inventory at a site near the slope), along with higher 228Ra concentrations and lower salinities relative to the Aleutian Basin area in the western Bering Sea. The observed features were considered to be a consequence of the arrival of FDNPP-derived radiocesium-rich and lower salinity Alaskan Stream water from the Pacific Ocean side, and subsequent mixing of the 228Ra-rich shelf water in the eastern slope area of the Bering Sea.