Cryoconite: an efficient accumulator of radioactive fallout in glacial environments

Abstract

Abstract. Cryoconite is rich in natural and artificial radioactivity, but a discussion about its ability to accumulate radionuclides is lacking. A characterization of cryoconite from two Alpine glaciers is presented here. Results confirm that cryoconite is significantly more radioactive than the matrices usually adopted for the environmental monitoring of radioactivity, such as lichens and mosses, with activity concentrations exceeding 10 000 Bq kg−1 for single radionuclides. This makes cryoconite an ideal matrix to investigate the deposition and occurrence of radioactive species in glacial environments. In addition, cryoconite can be used to track environmental radioactivity sources. We have exploited atomic and activity ratios of artificial radionuclides to identify the sources of the anthropogenic radioactivity accumulated in our samples. The signature of cryoconite from different Alpine glaciers is compatible with the stratospheric global fallout and Chernobyl accident products. Differences are found when considering other geographic contexts. A comparison with data from literature shows that Alpine cryoconite is strongly influenced by the Chernobyl fallout, while cryoconite from other regions is more impacted by events such as nuclear test explosions and satellite reentries. To explain the accumulation of radionuclides in cryoconite, the glacial environment as a whole must be considered, and particularly the interaction between ice, meltwater, cryoconite and atmospheric deposition. We hypothesize that the impurities originally preserved into ice and mobilized with meltwater during summer, including radionuclides, are accumulated in cryoconite because of their affinity for organic matter, which is abundant in cryoconite. In relation to these processes, we have explored the possibility of exploiting radioactivity to date cryoconite.

An overview of optical and thermal methods for the characterization of carbonaceous aerosol

“…Part of this feedback involves the increase of the cryoconite holes in glaciers [86]. Cryoconite is the dark, unconsolidated sediment that is found on the surface of glaciers worldwide [87], it is formed by the interaction between mineral particles and the microbial communities present on the surface of glaciers [88] and it also acts as accumulator of several anthropogenic species [89] and radioactive fallout [90]. Cryoconite has the potential to significantly impact surface albedo [86].…”

90Sr level and behaviour in the terrestrial environment of Spitsbergen

“…This observation corresponds to the previous findings. Namely, cryoconite granules are considered as highly rich in natural (unsupported 210 Pb) and artificial radioisotopes, significantly more radioactive than other environmental matrices routinely used in radioecological monitoring [9].…”

“…In recent years cryoconite holes have begun drawing attention among matrices known to be efficient in accumulating of radioisotopes and typically adopted for radioecological monitoring, such as lichens, mosses, peats, soils, sea and lake sediments. Cryoconite is a small size repository of a high level of pollutants on the glacier surfaces [9,46]. These aggregates of mineral and organic components are associated with biological consortia.…”

“…They decrease an icealbedo and are responsible for the formation of water-filled holes. Research on heavy metals and radionuclides in different environmental media showed that cryoconite absorbs most of the analysed elements in high concentration [9,42]. The hypothesis by Łokas et al [30,32] assumes that such material might be transferred into the proglacial zones while glaciers retreating, causing secondary contamination of the initial soils.…”

Artificial and natural radionuclides in cryoconite as tracers of supraglacial dynamics

“…It has not been observed in proglacial sediments. The identification of 207 Bi (t1/2 31.5 yr) in the environment is also rather rare, although it has been previously detected in some terrestrial environments (Bossew et al, 2006) and in cryoconite (Tieber et al, 2009;Baccolo et al, 2017Baccolo et al, , 2019. Its production in the Northern Hemisphere is associated with the explosion of the Tzar thermonuclear device in 1961 in Novaja Zemlja (Bossew et al, 2006).…”