First dataset of 236U and 233U around the Greenland coast: A 5-year snapshot (2012-2016)

We report the first combined dataset of U-236 and U-233 in the Greenland marine environment during the period of 2012-2016. Results are discussed in terms of time evolution and spatial distribution of U-236 concentration, and atomic ratios of U-236/U-238 and U-233/U-236, U-236 concentrations along the Greenland coast are distributed within a relatively narrow range of (0.7-12.9) x 10(7) atom/L, corresponding to U-236/U-2(38) atomic ratios of (1.1-15.5) x 10(-9). The U-233/U-236 atomic ratios obtained vary from 0.12 x 10(-2) to 1.16 x 10(-2), with the majority distributed in the range of (0.2-0.7) x 10(-2). We applied U-233/U-236 and U-236/U-238 atomic ratios in a binary mixing model to identify possible U-236 source terms. The results indicate that anthropogenic U-236 and U-233 in Greenland surface seawater originated from the direct global fallout (DGF) and the Sellafleld and La Hague reprocessing plants (RP) is diluted by a third endmember, mostly likely natural ocean water (NOW), containing marginal U-236 and U-233. A preliminary estimation of the source terms of U-236 using U-233/U-236 atomic ratios indicate that, for both eastern and western Greenland seawater, contributions from global fallout (GF) constitute about 30% of U-236. The dominating source for U-236, i.e. 70 %, is associated to reactor U-236 including discharges from RP and local reactor input in the Arctic Ocean. (C) 2020 Elsevier Ltd. All rights reserved.