EPJ Web of Conferences 24, 04005 (2012)
https://doi.org/10.1051/epjconf/20122404005

Seasonal variations of ²²⁸Ra/²²⁶Ra and ²²⁸Th/²²⁸Ra ratios in surface water from the eastern East China Sea

¹ Institute of Nature and Environmental Technology, Kanazawa University, Japan
² Fisheries Research Agency, Seikai National Fisheries Research Institute, Japan
³ Fisheries Research Agency, National Research Institute of Fisheries Science, Japan
⁴ Mutsu Marine Laboratory, Japan Marine Science Foundation, Aomori, Japan

Abstract

A total of 30 surface water samples were collected at 2 sites on the east side of the East China Sea (ECS) during 2008–20f0, and ²²⁶Ra, ²²⁸Ra, and ²²⁸Th activities were measured using low-background γ-spectrometry. The ²²⁸Ra/²²⁶Ra and ²²⁸Th/²²⁸Ra activity ratios of the samples exhibited notable seasonal variations (²²⁸Ra/²²⁶Ra = 0.2–3.3; ²²⁸Th/²²⁸Ra = < 0.1–0.4) accompanying salinity changes (31.0–34.6). These changes are hypothesized to cause the change by altering the mixing ratio of ²²⁸Ra-rich and particle-rich continental shelf water within the ECS.