Distributions of 137Cs in the Southern Sea of Korea: Preliminary results of onboard measurement in 2022

Abstract

Cesium-137 (137Cs; half-life = 30 years) is one of the artificial gamma-decay nuclides which has been produced from human activities related to nuclear facilities and reactors. In marine environments, 137Cs have been widely used as a tracer for water mass transport and sedimentation rates. We measured the horizontal and vertical distributions of 137Cs in seawater and other oceanographic parameters (i.e., temperature and salinity) during September 30 to October 5, 2022 in the Southern Sea of Korea (SSK). In this study, we applied the onboard measurement of 137Cs by the nickel potassium ferrocyanide (KNiFC) co- precipitation (< 12 hours) and High Purity Germanium (HPGe) detector (~ 8 hours of counting time) equipped in a shipbased mobile laboratory. 137Cs activities ranged from 1.35 to 2.60 dpm L-1, with a chemical recovery of 97% ± 5% (n > 30). These 137Cs activities were similar to those observed in the past from the SSK (2014-2021) which was measured by traditional methods (i.e., AMP co- precipitation). Our results suggest that the onboard measurement of 137Cs can be used in the event of an accident requiring urgent monitoring in the ocean.