Variability of fallout radionuclide accumulation and possible contamination sources of a peripheral glacier in...

Cryoconite, granule-shaped debris found on the surface of glaciers, is known for trapping substantial quantities of pollutants such as radioactive nuclides and heavy metals. This study investigates contamination levels, sources and spatial variability of natural and artificial radioisotopes in cryoconite from Mittivakkat Gletsjer in southeast Greenland by determining the activity and atomic ratios of selected radionuclides. The maximum activity concentrations of artificial radioisotopes were 1129 ± 34 Bq kg^-1 for ¹³⁷Cs, 3.75 ± 0.39 Bq kg^-1 for ²³⁸Pu; 62.6 ± 6.1 Bq kg^-1 for ^239+240Pu, and 23.2 ± 2.4 Bq kg^-1 for ²⁴¹Am. For natural radionuclides, the maximum concentrations were 4900 ± 120 Bq kg^-1 for ²¹⁰Pb, 470 ± 17 Bq kg^-1 for ⁴⁰K, and 42.9 ± 1.7 Bq kg^-1 for ²²⁸Ra. Statistically significant and positive correlations were found between altitude and activity concentrations of ¹³⁷Cs, ^238,239+240Pu, ²⁴¹Am, and ²¹⁰Pb. This linkage could be explained by lower ablation rates with altitude and higher presence of supraglacial channels near the glacier front. The major source of plutonium shown by ²³⁸Pu/^239+240Pu activity ratios in the surveyed area can be attributed to global fallout and is consistent with the activity ratios of ²⁴¹Am/^239+240Pu. The ^239+240Pu/¹³⁷Cs activity ratio suggests that the main source of cesium is global fallout, but possible input from Chernobyl cannot be excluded. Lower values of ²⁴⁰Pu/²³⁹Pu atomic ratio indicate a mixture of possible sources, including fallout derived from low-yield nuclear detonations such as from the Novaya Zemlya Test Site or Semipalatinsk. Overall, the findings of this study show that the radionuclide contamination levels on glaciers in southeast Greenland are relatively normal compared to other glaciers worldwide and that the dominating source is global fallout.