Scientists at IFJ PAN discovered significant differences in plutonium isotope accumulation between hemispheres, with unique anomalies linked to events like the Mars-96 crash. Their large-scale study of cryoconite on glaciers revealed cryoconite’s key role in concentrating radioactive contaminants, raising ecological concerns and prompting further research.
Recent investigations by scientists at the Institute of Nuclear Physics PAN have provided new insights into the accumulation of plutonium isotopes on Southern Hemisphere glaciers.
By analyzing cryoconite—sediment that forms and collects on glaciers—the researchers uncovered not only significant differences in isotope concentrations between the hemispheres but also identified unprecedented anomalies. These anomalies may be linked to incidents such as the crash of the Mars-96 spacecraft.
Glaciers are not just scenic features of mountain landscapes; they play a crucial role in global freshwater reserves. However, their melting due to global warming poses serious threats. These include rising sea levels and a reduction in water resources critical for hydroelectric power generation.
Moreover, as glaciers melt, they release radionuclides and other contaminants, which can migrate into nearby ecosystems. There, these pollutants may accumulate, entering the food chain and potentially disrupting environmental balance.
Sources and Impacts of Radioactive Contaminants
Radioactive elements are present in the environment as a result of natural processes and human activity. Artificial radionuclides, such as plutonium, are released into the environment mainly through nuclear tests, reactor accidents, or failures of satellites and space probes containing radioactive sources of energy.
These substances, transported mainly through the atmosphere, accumulate in different ecosystems, including glaciers, in the form of dark sediments called cryoconite. A typical cryoconite hole is no more than a few dozen centimeters in diameter and depth. At its bottom, there is a dark sediment called cryoconite. It contains organic material and contaminants, i.e. radionuclides, heavy metals, pesticides, microplastics, or antibiotics. This sediment may pose a potential threat to local ecosystems.
The newest investigations conducted at the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) with the use of novel methods of mass spectrometry allowed researchers to create a database for plutonium isotopes (238,239,240Pu) in the glaciers of the Northern and Southern Hemispheres.
The analyzed samples of cryoconite come from 49 glaciers of nine regions of the world, including the Arctic, Alpes, Himalayas, and Antarctica. The material was collected by an international team of researchers over the years 2000-2020, and the studies were financed from a National Science Centre project.
“These are the first analyses of plutonium concentration in cryoconite samples carried out on such a large scale” – says Dr. Edyta Łokas (IFJ PAN), the initiator and first author of the article published in Science of the Total Environment.
Key Findings: Hemispheric Differences and Isotope Anomalies
The results of the study have provided unique information about the accumulation, distribution and sources of plutonium isotopes in glaciers. The concentration of 239+240Pu activity turned out to be much higher in the Northern than the Southern Hemisphere, which reflects an uneven deposition of Pu coming from nuclear weapon tests between the hemispheres. As for the Northern Hemisphere, the highest concentrations are observed in Scandinavia and the Alps. No relevant differences have been noticed between the hemispheres in the case of 238Pu. The cryoconite from the southern hemisphere is characterized by high heterogeneity in terms of both Pu activity and mass ratio.
The isotope ratios of 238Pu/239+240Pu, so far unprecedented in the literature, have been for the first time observed in the cryoconite of the Exploradores Glacier in Patagonia. Researchers hypothesize that the excess of 238Pu may be related to the fall of the Soviet space probe MARS-96, which sank in the ocean off the coast of Chile in 1996. The space probe contained a generator with 238Pu, which may explain higher concentrations of this isotope on the nearby glacier. The results of the study are the first observations of their kind showing anomalies in plutonium isotope ratios in the Southern Hemisphere.
Additionally, the cryoconite samples from South American glaciers demonstrated 240Pu/239Pu mass ratios significantly deviating from those found in the literature, which may suggest that the dominant source of Pu is related to low-altitude nuclear tests conducted in the area of French Polynesia.
“The concentrations of plutonium activity in the cryoconite that we have observed are – especially in the Northern Hemisphere – orders of magnitude higher than in other environmental matrices used to monitor the environment, such as lichen, moss, soil, and sediments. Simultaneously, our discoveries emphasize the importance of cryoconite in the accumulation of radioactive contaminants that may pose a potential threat to the surrounding fauna and flora, and at the same time they may help us to track the diffusion of those pollutants”. – notes Dr. Edyta Łokas.
The group of researchers from IFJ PAN continue their work. The next investigations, conducted in cooperation with the AGH University in Kraków, took place at the ice cap of Jostedalsbreen in Norway. The expedition, organized in August 2024, aimed at better understanding the processes of contaminant accumulation in glaciers and their sources.
Reference: “Isotopic signature of plutonium accumulated in cryoconite on glaciers worldwide” by Edyta Łokas, Giovanni Baccolo, Anna Cwanek, Jakub Buda, Katarzyna Kołtonik, Nozomu Takeuchi, Przemysław Wachniew, Caroline Clason, Krzysztof Zawierucha, Dylan Bodhi Beard, Roberto Ambrosini, Francesca Pittino, Andrea Franzetti, Philip N. Owens, Massimiliano Nastasi, Monica Sisti and Biagio Di Mauro, 8 August 2024, Science of The Total Environment.
DOI: 10.1016/j.scitotenv.2024.175356
