Hyper-accumulation of legacy fallout radionuclides in cryoconite on Isfallsglaciären (Arctic Sweden) and their downstream distribution

Abstract

Abstract. The release of legacy fallout radionuclides (FRNs) in response to glacier retreat is a process that has received relatively little attention to date, yet may have important consequences as a source of secondary contamination as glaciers melt and down-waste in response to a warming climate. The prevalence of FRNs in glacier-fed catchments is poorly understood in comparison to other contaminants, yet there is now emerging evidence from multiple regions of the global cryosphere for substantially augmented FRN activities in cryoconite. Here we report concentrated FRNs in both cryoconite and proglacial sediments from the Isfallsglaciären catchment in Arctic Sweden. Activities of some FRNs in cryoconite are two orders of magnitude above those found elsewhere in the catchment, and above the activities found in other environmental matrices outside of nuclear exclusion zones. We also describe the presence of the short-lived cosmogenic radionuclide 7Be in cryoconite samples, highlighting the importance of meltwater-sediment interactions in radionuclide accumulation in the ice surface environment. The presence of fallout radionuclides in glaciers may have the potential to impact local environmental quality through both isolated hotspots of radioactivity caused by glacier down-wasting, and downstream transport of contaminants to the proglacial environment through interaction with sediments and meltwater. We thus recommend that future research in this field focusses on processes of accumulation of FRNs and other environmental contaminants in cryoconite, and whether these contaminants are present in quantities harmful for both local and downstream ecosystems.

Anthropogenic contaminants in glacial environments I: Inputs and accumulation

“…Previous research on cryoconite has often focused on microorganism ecosystems and the ability of cryoconite to accumulate nutrients (Poniecka et al, 2020; Poniecka and Bagshaw, 2021). However, recent research has shown that cryoconite can also act as a sink for pollutants including BC, FRNs and PTEs (Clason et al, 2021; Cong et al, 2018; Fortner and Lyons, 2018; Li et al, 2017; Łokas et al, 2018). Larger pockets of cryoconite called ‘cryoconite holes’ vary in size, but typically have dimensions of 10–100cm 3 (MacDonell and Fitzsimons, 2008, 2012).…”

“…There is evidence that even low to moderate doses of FRNs within drinking water can increase cancer risk and genetic malformations (WHO, 2008). FRNs have been found in most regions of the global cryosphere, but research has predominantly focused on activity in the northern hemisphere due to the location of many FRN sources, including areas such as the European Alps, Canada, Svalbard, Scandinavia and the Caucasus (Baccolo et al, 2020; Clason et al, 2021; Łokas et al, 2016, 2018, 2021; Owens et al, 2019). FRNs found in high concentrations include 137 Cs, 241 Am and 210 Pb, with some of the highest concentrations found in cryoconite, an organic rich glacial sediment (Baccolo et al, 2020; Łokas et al, 2019).…”

“…If the glacier is on an impermeable bedrock or frozen substrate, the meltwater will travel along the basal layer, releasing contaminants in the proglacial area (Eyles, 2006). Glacial lakes and fjords, often situated within close proximity to glaciers, are an efficient accumulating mechanism, becoming repositories for contaminants, which can settle within sediments due to the low velocity of the water (Clason et al, 2021; Mohan et al, 2018; Zhu et al, 2020). These lakes are rapidly growing in response to climate change and glacier retreat (Shugar et al, 2020).…”