the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 May 2025
Unprecedented radioactive pollution in Spitsbergen air – first data as of 21st century
Abstract. The present study concerned the Arctic troposphere, providing an experimental database on nuclear aerosols that has improved considerably since 1999. The activity concentrations of 238Pu, 239+240Pu and 241Am were determined in the surface air of Hornsund, Spitsbergen, during 2007–2021. A multivariate approach was employed, incorporating meteorological data, 7Be, 137Cs, 210Pb records and isotopic ratios, to explain the transuranium dynamics of changes and provenance. 238Pu and 239+240Pu levels were comparable to recent observations from various locations, whereas 241Am exhibited particularly high values, with a maximum of 354 Bq/m3 detected in 2019. The highest activity concentrations of 6.61 nBq/m3 for 238Pu and 15.51 nBq/m3 for 239+240Pu identified in 2015 could be due to fly ash particles following wildfires in proximity to the Chernobyl zone. During the remaining period, 239+240Pu was correlated with seasonal processes, such as local resuspension and horizontal tropospheric transport of haze layers from remote areas. Similar mechanisms likely regulated a portion of 238Pu, but to a lesser extent. Unexpected single incidents of 237Np were encountered in 2013, 2014 and 2018. Furthermore, activity ratio evaluation demonstrated a frequent occurrence of 238Pu enrichment regarding known nuclear events. Unusual elevated levels of 241Am, 238Pu and 237Np were not associated with environmental processes; therefore, the possibility of recent anthropogenic emissions should be considered. Trajectory simulations performed in 2019 showed prominent transport pathways to the Hornsund from northern Eurasia.
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RC1: 'Comment on egusphere-2025-1573', Anonymous Referee #1, 03 Jul 2025
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The manuscript entitled "Unprecedented radioactive pollution in Spitsbergen air – first data as of 21st century" presents a very interesting and well-written study. The research addresses an important topic in the field of environmental radioactivity and provides new, valuable data on the concentrations and sources of transuranic radionuclides and other artificial and natural radioisotopes in the Arctic atmosphere. The manuscript is clear, logically structured, and presents its methodology and results in a transparent way. I found the discussion to be insightful and supported by relevant literature. While I have a few minor comments and suggestions for improvement, overall, I believe the work is of high quality and recommend it for publication after minor revision.
Line 130 The formulation “the most radiotoxic elements” is not sufficiently precise. While it is true that Pu and Am isotopes are among the most radiotoxic substances on a per-mass basis when incorporated into the human body, their activity concentrations in the environment are typically very low. As a result, their actual impact on human health under natural environmental conditions is negligible, except in cases of nuclear accidents. It would be more accurate to state that they are “among the most radiotoxic elements.”
Line 204 The manuscript states that “the set of weekly air filters was delivered from the Polish Polar Station in Hornsund, Svalbard Archipelago, to the National Centre for Nuclear Research (NCBJ) in Świerk, Poland.” However, the text does not clearly indicate whether the filters were actually sent to Poland every week, or whether shipments coincided with the rotation of polar station personnel and supply missions, which typically occur only a few times a year. This information is particularly important for short-lived radionuclides such as 7Be, as significant delays between sample collection and analysis can result in considerable activity losses and may affect the accuracy of the results.
Line 220 Due to low concentrations, the samples were aggregated on a quarterly or semi-annual basis. While this approach is technically understandable, it significantly limits the ability to detect short-term incidents and to link them to specific meteorological events or emission episodes. I recommend that the authors explicitly acknowledge this limitation in the manuscript.
Line 279 While the application of Tukey’s interquartile range (IQR) method with a conservative multiplier (k = 3) is a well-established and robust approach for detecting statistical outliers, it may have certain limitations when applied to highly dispersed and temporally aggregated environmental data, such as quarterly-averaged radionuclide concentrations. In such cases, individual extreme values often reflect true episodic events (e.g., sudden contaminant influx, wildfire transport, or atmospheric resuspension episodes) rather than errors or measurement artifacts. The IQR method, which does not consider temporal context or trends, may misclassify these scientifically relevant episodes as statistical outliers and overlook underlying regime shifts or changes in baseline levels. Therefore, it could be beneficial to consider supplementing the IQR analysis with additional time series methods—which are well suited to identifying genuine shifts or episodic changes in environmental data.
Line 319 I suggest that Table 1 should also include information on the measurement uncertainty, particularly if the filters were analyzed after a significant storage period. If there was a substantial delay between sample collection and measurement, the decay correction and its associated uncertainty could have a notable impact on the final results—especially for radionuclides with shorter half-lives
Line 345 While the general patterns of 210Pb and 7Be in the lower atmosphere are similar, it is worth noting that, in the case of 210Pb, local emissions related to fuel combustion at the station during winter may also contribute to the elevated concentrations observed in this period
Line 355 The outliers result from the application of Tukey’s method, as noted in the comment described in line 279.
Line 569 Additionally, military activities in Ukraine in 2022 may have contributed to a temporary increase in airborne 137Cs, as observed across Europe.
Citation: https://doi.org/10.5194/egusphere-2025-1573-RC1 -
CC1: 'Reply on RC1', Marek Kubicki, 04 Jul 2025
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Thank you very much for the comments and suggestions described in lines 204 and 220. I agree with them. I would like to add that the filters are delivered for analysis conducted at NCBJ three times a year, i.e. in April, July and September, and this is related to the organization of transport from the Polish Polar Station in Hornsund. This causes losses in activity, especially Be7. Your suggestions will allow us to resume the discussion on the much more frequent shipment of filters.
My interests concern the electricity of the atmosphere and the research Global Electric Circuit of the Earth. The ability to detect Be7 concentration in a short time and with high accuracy is very much needed, because Be 7 ionizes the upper layers of the atmosphere, affecting changes in the electric current between the ionosphere and the earth.
We also made attempts to increase the time resolution of the measurement of radionuclide concentration using the NA-J gamma detector placed directly under the measuring filter in order to obtain results directly at the station.
Thank you very much for your attention to this important measurement aspect. I can assure you that we are working on better solutions than the current ones.
Marek Kubicki, co-author
Citation: https://doi.org/10.5194/egusphere-2025-1573-CC1
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CC1: 'Reply on RC1', Marek Kubicki, 04 Jul 2025
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