Accumulation of atmospheric radionuclides and heavy metals in cryoconite holes on an Arctic glacier

• Extremely high radioactivity was found in Arctic cryoconites.
• Cryoconites retain and concentrate airborne radionuclides on glacier surfaces.
• Heavy metals in cryoconites exceed natural background.
• Strong anthropogenic contribution to heavy metal deposition in the Arctic was noted.

Surface of glaciers is covered by mineral and organic dust, together with microorganisms forming cryoconite granules. Despite fact that glaciers and ice sheets constitute significance part of land surface, reservoir of freshwater, and sites of high biological production, the knowledge on the cryoconite granules still remain unsatisfactory. This study presents information on radionuclide and heavy metal contents in cryoconites. Cryoconites collected from the Hans Glacier in SW Spitsbergen reveal high activity concentrations of anthropogenic (238,239,240Pu, 137Cs, 90Sr) and natural (210Pb) radionuclides. The 238Pu/239+240Pu activity ratios in these cryoconites significantly exceed the mean global fallout ratio (0.025). The 238Pu/239+240Pu ranged from 0.064 to 0.118. The 239+240Pu/137Cs varied from 0.011 ± 0.003 to 0.030 ± 0.007. Such activity ratios as observed in these cryoconites were significantly higher than the values characterizing global fallout, pointing to possible contributions of these radionuclides from other sources. Heavy metals (Pb, Cd, Cu, Zn, Fe, and Mn) in cryoconites exceed both UCC concentrations and local rocks’ concentrations, particularly for cadmium. The concentration ratios of stable lead isotopes (206Pb/207Pb, 208Pb/206Pb) were determined to discriminate between the natural and anthropogenic sources of Pb in cryoconites and to confirm the strong anthropogenic contribution to heavy metal deposition in the Arctic. In investigated cryoconite holes, two groups of invertebrates, both extremophiles, Tardigrada and Rotifera were detected. Our study indicate that cryoconites are aggregates of mineral and organic substances on surfaces of glaciers are able to accumulate large amounts of airborne pollutants bound to extracellular polymeric substances secreted by microorganisms.