We report for the first time an environmental uranium-236 (236U) and uranium-233 (233U) dataset, on samples in the Greenland marine environment during the 5-year period (2012-2016). Results are discussed in terms of time evolution and spatial distribution characters of radionuclides (236U) concentrations and isotopic ratios of 236U/238U and 233U/236U. Our results indicate that 236U concentrations and 236U/238U atomic ratios along Greenland coast are distributed within a relatively narrow range of (3.6-8.2) × 107 atoms/L and 1× 10-9, respectively, but still up to 4 times the expected value from direct global fallout (236U=0.8 × 107 atoms/L and 236U/238U=1× 10-9).
Slightly higher 236U/238U ratios as well as high 236U concentrations were observed on the west coast of Greenland compared to the eastern side for 2012, 2015 and 2016, which is in contrast to the expectation that the major source term of 236U near the Greenland coast are the two European reprocessing plants. This feature might be interpreted as a hint for another 236U input in the western Greenland Sea, but may also be caused by the complexity of water currents or by the slow turnover rate. A first preliminary source term assessment was performed using the measured 233U/236U ratios indicating considerable differences in the contributions from the various source terms for 236U between the east and west coast of Greenland.