Abstract
Cryoconite granules are mixtures of mineral particles, organic substances and organisms on the surface of glaciers where they decrease the ice albedo and are responsible for formation of water-filled holes. The contaminants are effectively trapped in the cryoconite granules and stay there for many years. This study evaluates the contamination level of artificial and natural radionuclides in cryoconite holes from Adishi glacier (Georgia) and identifies the sources of contamination based on activity or mass ratios among artificial radionuclides. Results revealed high activity concentrations of fallout radionuclides reaching 4900 Bq/kg, 2.5 Bq/kg, 107 Bq/kg and 68 Bq/kg for 137Cs, 238Pu, 239+240Pu and 241Am, respectively. The main source of Pu is global fallout, but the low 240Pu/239Pu atomic ratios also indicated local tropospheric source of 239Pu, probably from the Kapustin Yar nuclear test site. Also, high activity ratios of 241Am/239+240Pu could originate from Kapustin Yar. The natural radionuclides originate from the surrounding rocks and were measured to control the environmental processes. 210Pb in cryoconite granules comes predominantly from the atmospheric deposition, and its activity concentrations reach high values up to 12000 Bq/kg.
Highlights
Analytical procedures for all isotopes. 137Cs and 210Pb activities were determined using a planar HPGe detector
The combination of the results obtained from different isotopic and mass ratios allowed us to investigate the proportion of Cs, Pu and Am from different sources
Black Sea-Caspian Sea are determined by their location between the converging Eurasian and Africa-Arabian lithosphere plates within a zone of continent-continent collision[61]
Summary
The activities of 137Cs were determined using its emission peak at 662 keV, and its emission peak at 46.6 keV was used to determine the activities of 210Pb. The absolute efficiencies of the detector were determined using calibrated sources and sediment samples of known activity. Corrections were made to measure the effect of self-absorption of low-energy γ-rays (46.6 keV) within the sample, these corrections were insignificant because the masses of the samples were low. The activities of the 238Pu, 239+240Pu, 241Am, 234,238U, 230,232Th and 90Sr dried samples were determined 0.94 and 1.93 g. Organic matter in the samples was decomposed by heating in a Muffle oven at 600 °C for 6 hour
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