Extreme levels of fallout radionuclides and other contaminants in glacial sediment (cryoconite) and implications for downstream aquatic ecosystems

Unveiling threats to glacier biota: Bioaccumulation, mobility, and interactions of radioisotopes with key biological components

Contemporary melting glaciers are considered a secondary source of pollutants including radionuclides. Cryoconite - biogenic sediment on the glacier surface - exhibits high concentrations of natural and anthrophogenic radioisotopes. Understanding the interactions between radioisotopes and organisms is essential for evaluating their potential impact on glacier-related ecosystems. Using a multidimensional approach and intensive sampling (17 glaciers), we investigated the relationships between activity concentrations of 137Cs and 210Pb and various biotic components of cryoconite such as the amount of organic matter, chlorophyll concentration, the ratio of cyanobacteria to all bacteria, and size of cryoconite granules. Additionally, to better understand the bioavailability and fate of radioisotopes in this ecosystem, we measured the uptake ratio of 137Cs, 210Pb, 238Pu, and 239+240Pu in the top consumers, and examined the mobility of radioisotopes by measuring 137Cs and 210Pb activity concentrations after a parallel extraction using media with different specific ion exchange capacities. The activity concentrations of both 137Cs and 210Pb showed a large variability reaching 5.8 kBq kg-1 and 7.2 kBq kg-1, respectively. Their activity concentrations were positively related to the amount of organic matter, however, the 210Pb also increased with the chlorophyll concentration. This might be due to the difference in the deposition of both elements: lead, being deposited constantly, binds also to currently developing communities, while caesium deposition peaked in the 1960s. The mobility analysis revealed that the loosely bound fraction of 210Pb was more strongly related to organic-metallic complexes than 137Cs. Firmly bound radioisotope fractions (anhydrous interlayer sites of minerals) were three times higher for 137Cs than for 210Pb. The median uptake ratios of radioisotopes were determined as 0.07-0.111 for 137Cs, 0.177 for 210Pb, 0.07 for 239+240Pu. Our findings emphasize the importance of organisms in the accumulation of radioisotopes on glaciers and suggest an impact of radionuclides on glacier organisms.

Chemical availability of fallout radionuclides in cryoconite

Atmospheric deposition on glaciers is a major source of legacy fallout radionuclides (FRNs) accumulating in cryoconite, a dark granular material with surface properties that efficiently bind FRN contaminants (specifically 137Cs; 210Pb; 241Am). Cryoconite-bound FRNs in glaciers can be released when they interact with and are transported by glacial meltwater, resulting in the discharge of amassed particulate contaminants into aquatic and terrestrial environments downstream. The environmental consequences of FRN release from the cryosphere are poorly understood, including impacts of cryoconite-sourced FRNs for alpine food chains. Consequently, there is limited understanding of potential health risks to humans and animals associated with the consumption of radiologically-contaminated meltwater. To assess the chemical availability of cryoconite-adsorbed FRNs we used a three-stage sequential chemical extraction method, applied to cryoconite samples from glaciers in Sweden and Iceland, with original FRN activity concentrations up to 3300 Bq kg-1 for 137Cs, 10,950 Bq kg-1 for unsupported 210Pb (210Pbun) and 24.1 Bq kg-1 for 241Am, and orders of magnitude above regional backgrounds. Our results demonstrate that FRNs attached to cryoconite are solubilized to different degrees, resulting in a stage-wise release of 210Pbun involving significant stepwise solubilization, while 137Cs and 241Am tend to be retained more in the particulate phase. This work provides an insight into the vulnerability of pristine glacial environments to the mobilization of FRN-contaminated particles released during glacier melting, and their potential impact on glacial-dependent ecology.

Natural and anthropogenic radionuclides concentration with heavy metals analysis of the sediments collected around Novaya Zemlya

The Dispersal profile of the radioisotopes (226Ra, 232Th, 235U, 40K, 137Cs) along with potentially toxic elements (Cd, Co, Cr, Cu, Ni, Pb, V, Zn, and Hg) in the sediments around the Novaya Zemlya was determined. The task was fulfilled with the aid of HPGe gamma spectrometry, inductively coupled plasma optical emission spectroscopy, DMA-80 Direct Mercury Analysis System, X-ray diffraction and statistical tools. At most of the locations, the radionuclides activity was higher than the world average activity concentration for the respective nuclei, 40K being the most abundant. From all the potentially toxic elements detected, Cr and Ni were usually observed on higher levels compared to their background values, indicating the probability of the detrimental biological effects. Thus, the present situation at the studied area might be a threat to the neighboring marine life.

137Cs and isotopic ratios of Pu and U in lichens and mosses from Russian Arctic areas

Knowledge of past anthropogenic sources of radionuclide contamination in Russian Arctic areas is important to assess the radioecological situation of these less-studied regions. Therefore, we investigated the sources of radionuclide contamination in Russian Arctic in the 1990s. Lichen and moss samples were collected from 1993 to 1996 in Kola Peninsula, Franz Josef Land, and few other locations. The activity concentration of 137Cs was determined from the archived samples by gamma spectrometry in 2020. After radiochemical separation of Pu and U isotopes from the lichens and mosses, mass ratios 240Pu/239Pu, 234U/238U, 235U/238U, and 236U/238U were determined by mass spectrometry. 137Cs activity concentrations at the sampling date were found to vary from 3.1 ± 1.4 (Inari, Finnish-Russian border) to 303 ± 7 (Kola Peninsula) Bq/kg. The ranges of isotopic ratios were 0.0592 ± 0.0007 to 0.253 ± 0.082 for 240Pu/239Pu, (4.89 ± 3.91) × 10-5 to (6.86 ± 0.04) × 10-5 for 234U/238U, 0.0072104(21) to 0.007376(41) for 235U/238U, and from below 1 × 10-7 to (2.65 ± 0.19) × 10-6 for 236U/238U, respectively. Based on the measured isotopic ratios and characteristic isotopic ratios of known contamination sources, the main Pu and U sources in the sampled lichens and mosses are global fallout, the Chernobyl accident, and possibly local nuclear activities. These results contribute to further understanding of past nuclear events and resulting nuclear contamination in Russian Arctic terrestrial areas.

Radionuclide contamination in Canada: A scoping review

Radionuclides were first discovered in the late 1800s, and artificial (anthropogenic) radionuclides in the 1930s. Since then, this group of substances has been increasingly incorporated into various peaceful and non-peaceful applications across Canada and the world, bringing with it both advanced technological and medical benefits, and public concern about the dangers from radiation exposure. As such, a breadth of research on, and monitoring of, radionuclides in the Canadian environment has been generated, the results of which span decades. However, a recent comprehensive review of these is not readily available. This study aims to fill this gap by synthesizing available literature from the last 30 years on the Canadian state and provenance of radionuclide contamination to better understand the context of overall sources and status of contamination. The findings indicate that while regional and temporal variations exist, on average, routine radionuclide exposure in Canada is generally attributed mainly to natural sources and fallout from historical nuclear weapons testing and nuclear accidents (including the Chernobyl and Fukushima power plant accidents) and to a smaller degree to emissions from nuclear facilities, including active and historical uranium mines and mills, nuclear research facilities, and nuclear power plants. Levels of anthropogenic radionuclides in the Canadian environment have declined since the initial cessation of nuclear weapons testing in the 1960s and are generally below guidelines protective of human health. On the national scale, present-day nuclear sector facilities do not appear to be a significant source of routine anthropogenic, nor technically-enhanced naturally occurring radionuclide exposure, though local scenarios may vary. These findings contribute context for evaluating the sustainable management of nuclear technologies, radioactive materials and waste in Canada and globally, in line with UN Sustainable Development Goal 12 and target 12.4: responsible management of chemicals and waste.

Legacy radionuclides in cryoconite and proglacial sediment on Orwell Glacier, Signy Island, Antarctica

Cryoconite is a specific type of material found on the surface of glaciers and icesheets. Samples of cryoconite were collected from the Orwell Glacier and its moraines, together with suspended sediment from the proglacial stream on Signy Island, part of the South Orkney Islands, Antarctica. The activity concentrations of certain fallout radionuclides were determined in the cryoconite, moraine and suspended sediment, in addition to particle size composition and %C and %N. For cryoconite samples (n = 5), mean activity concentrations (±1SD) of ¹³⁷Cs, ²¹⁰Pb_un and ²⁴¹Am were 13.2 ± 20.9, 66.1 ± 94.0 and 0.32 ± 0.64 Bq kg^-1, respectively. Equivalent values for the moraine samples (n = 7) were 2.56 ± 2.75, 14.78 ± 12.44 and <1.0 Bq kg^-1, respectively. For the composite suspended sediment sample, collected over 3 weeks in the ablation season, the values (± counting uncertainty) for ¹³⁷Cs, ²¹⁰Pb_un and ²⁴¹Am were 2.64 ± 0.88, 49.2 ± 11.9 and <1.0 Bq kg^-1, respectively. Thus, fallout radionuclide activity concentrations were elevated in cryoconite relative to moraine and suspended sediment. In the case of ⁴⁰K, the highest value was for the suspended sediment (1423 ± 166 Bq kg^-1). The fallout radionuclides in cryoconite were 1-2 orders of magnitude greater than values in soils collected from other locations in Antarctica. This work further demonstrates that cryoconite likely scavenges fallout radionuclides (dissolved and particulate) in glacial meltwater. In the case of ⁴⁰K, the greater value in suspended sediment implies a subglacial source. These results are amongst the relatively few that demonstrate the presence of fallout radionuclides in cryoconites at remote locations in the Southern Hemisphere. This work adds to the growing contention that elevated activities of fallout radionuclides, and other contaminants, in cryoconites are a global phenomenon and may be a risk to downstream terrestrial and aquatic ecosystems.

Impact of anthropogenic contamination on glacier surface biota

Glaciers are ecosystems and they host active biological communities. Despite their remoteness, glaciers act as cold condensers where high precipitation rates and cold temperatures favor the deposition of pollutants. These contaminants include a broad range of substances, including legacy pollutants, but also compounds still largely used. Some of these compounds are monitored in the environment and their effects on the ecosystems are known, in contrast others can be defined as emerging pollutants since their presence and their impact on the environment are still poorly understood (e.g. microplastics, radionuclides). This review aim to provide an overview of the studies that have investigated the effects of pollutants on the supraglacial ecosystem so far. Despite the distribution of the pollutants in glacier environments has been discussed in several studies, no review paper has summarized the current knowledge on the effects of these substances on the ecological communities living in glacier ecosystems.

Bottom sediment radioactivity of the six Caucasus lakes located in different altitude zones

Natural and artificial radioactivity of bottom sediment in the six lakes of the Western and Central Caucasus have been evaluated. It allowed to define the variation of sedimentation rate during the last 100-150 years using technogenic (¹³⁷Cs) and natural (²¹⁰Pb, ²²⁶Ra) radionuclides as a chronomarkers. The studied lakes are located in the contrasting geographic conditions, different orographic positions, and have different origin. The average annual precipitation in the area of each of the lakes has been detected to stay relatively constant during the ¹³⁷Cs fallout period, while the air temperature has markedly increased during the last decades. The detected sedimentation rates are the indirect indicator of climate change in the mountains. They are slightly decreasing owing to the increased protection of soil by vegetation cover in the lower altitude zone; in the upper zones, they are growing due to accelerated glacier retreat. The radioecological situation is estimated as normal. High levels of ¹³⁷Cs (33 kBq m^-2) and ²⁴¹Am (0.1 kBq m^-2) in bottom sediments are attributed to the region-specific geographical characteristics.

Thermodynamics Affecting Glacier-Released 4-Nonylphenol Deposition in Alaska, USA

Glaciers have recently been recognized as a secondary source of organic pollutants. As glacier melt rates increase, downstream ecosystems are at increasing risk of exposure to these pollutants. Nonylphenols (NPs) are well-documented anthropogenic persistent pollutants whose environmental prevalence and ecotoxicity make them of immediate concern to the health of humans and wildlife populations. As glacier melt increases, transport of NPs to downstream environments will also increase. Snow, ice, meltwater, and till for five glaciers in the Chugach National Forest and Kenai Fjords National Park, Alaska, USA, were investigated for the presence of 4-nonylphenol (4NP). Average concentrations for snow, ice, meltwater, and glacial till were 0.77 ± .017 µg/L snow water, 0.75 ± .006 µg/L, 0.26 ± .053 µg/L, and 0.016 ± .004 µg/g, respectively. All samples showed the presence of 4NP. Deposition of 4NP downstream from glaciers will depend more on the ionic strength of the water than organic carbon to drive partitioning and deposition. Laboratory studies of partition coefficients showed that ionic strength contributed 59% of the driving force behind partitioning, while organic carbon contributed 36%. Evidence was found for interaction between organic carbon and the aqueous phase. The 4NP Setschenow constants (K_s ) were determined for particle types with varying percentages of organic carbon. Values of K_s increased with the percentage of organic carbon. These relationships will shape further studies of 4NP deposition into the environment downstream of glacier outflow. Environ Toxicol Chem 2022;41:1623-1636. © The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Unveiling the extreme environmental radioactivity of cryoconite from a Norwegian glacier

This study is a first survey of the occurrence of artificial (¹³⁷Cs, ²⁴¹Am, ²⁰⁷Bi, Pu isotopes) and natural (²¹⁰Pb, ²²⁸Ac, ²¹⁴Bi, ⁴⁰K) radionuclides in Norwegian cryoconite. Cryoconite samples were collected before (12 samples) and after (5 samples) a rainfall event, after which 7 cryoconite holes dissapeared. The concentrations of radionuclides in cryoconite samples from the Blåisen Glacier are compared with data from the Arctic and Alpine glaciers. Cryoconite samples from the studied glacier had extremely high activity concentrations of ¹³⁷Cs, ²⁴¹Am, ²⁰⁷Bi and ^239+240Pu (up to 25,000 Bq/kg, 58 Bq/kg, 13 Bq/kg and 131 Bq/kg, respectively) and also high concentrations of organic matter (OM), comparing to other Scandinavian and Arctic glaciers, reaching up to ~40% of total mass. The outstandingly high concentrations of ¹³⁷Cs, ²⁴¹Am, Pu isotopes, and ²⁰⁷Bi on the Blåisen Glacier are primarily related to bioaccumulation of radionuclides in organic-rich cryoconite and might be enhanced by additional transfers of contamination from the tundra by lemmings during their population peaks. The presumed influence of intense rainfall on radionuclide concentrations in the cryoconite was not confirmed.

Radioecological and geochemical peculiarities of cryoconite on Novaya Zemlya glaciers

In recent years, cryoconite has received growing attention from a radioecological point of view, since several studies have shown that this material is extremely efficient in accumulating natural and anthropogenic radionuclides. The Novaya Zemlya Archipelago (Russian Arctic) hosts the second largest glacial system in the Arctic. From 1957 to 1962, numerous atmospheric nuclear explosions were conducted at Novaya Zemlya, but to date, very little is known about the radioecology of its ice cap. Analysis of radionuclides and other chemical elements in cryoconite holes on Nalli Glacier reveals the presence of two main zones at different altitudes that present different radiological features. The first zone is 130-210 m above sea level (a.s.l.), has low radioactivity, high concentrations of lithophile elements and a chalcophile content close to that of upper continental crust clarkes. The second zone (220-370 m a.s.l.) is characterized by high activity levels of radionuclides and "inversion" of geochemical behaviour with lower concentrations of lithophiles and higher chalcophiles. In the upper part of this zone (350-370 m a.s.l.), ¹³⁷Cs activity reaches the record levels for Arctic cryoconite (5700-8100 Bq/kg). High levels of Sn, Sb, Bi and Ag, significantly exceeding those of upper continental crust clarkes, also appear here. We suggest that a buried layer of contaminated ice that formed during atmospheric nuclear tests serves as a local secondary source of radionuclide contamination. Its melting is responsible for the formation of this zone.

Glacier algae foster ice-albedo feedback in the European Alps

The melting of glaciers and ice sheets is nowadays considered a symbol of climate change. Many complex mechanisms are involved in the melting of ice, and, among these processes, surface darkening due to organic material on bare ice has recently received attention from the scientific community. The presence of microbes on glaciers has been shown to decrease the albedo of ice and promote melting. Despite several studies from the Himalaya, Greenland, Andes, and Alaska, no quantitative studies have yet been conducted in the European Alps. In this paper, we made use of DNA sequencing, microscopy and field spectroscopy to describe the nature of glacier algae found at a glacier (Vadret da Morteratsch) of the European Alps and to evaluate their effect on the ice-albedo feedback. Among different algal species identified in the samples, we found a remarkable abundance of Ancylonema nordenskioeldii, a species that has never previously been quantitatively documented in the Alps and that dominates algal blooms on the Greenland Ice Sheet. Our results show that, at the end of the ablation season, the concentration of Ancylonema nordenskioeldii on the glacier surface is higher than that of other algal species (i.e. Mesotaenium berggrenii). Using field spectroscopy data, we identified a significant correlation between a reflectance ratio (750 nm/650 nm) and the algae concentration. This reflectance ratio could be useful for future mapping of glacier algae from remote sensing data exploiting band 6 (740 nm) and band 4 (665 nm) of the MultiSpectral Instrument (MSI) on board Sentinel-2 satellite. Here we show that the biological darkening of glaciers (i.e. the bioalbedo feedback) is also occurring in the European Alps, and thus it is a global process that must be taken into account when considering the positive feedback mechanisms related to glacier melting.