Measurements and modeling of airborne plutonium in Subarctic Finland between 1965 and 2011

Abstract

Abstract. The activity concentrations of 238,239,240Pu and 241Am (for determining its mother nuclide, 241Pu) as well as activity ratios of 238Pu/239+240Pu, 241Pu/239+240Pu and 239+240Pu/137Cs and the mass ratio of 240Pu∕239Pu were determined from air filter samples collected in Rovaniemi (Finnish Lapland) in 1965 to 2011. The origin of plutonium in surface air was assessed based on these data from long time series. The most important Pu sources in the surface air of Rovaniemi were atmospheric nuclear-weapon testing in the 1950s and 1960s, later nuclear tests in 1973–1980 and the SNAP-9A satellite accident in 1964, whereas the influence from the 1986 Chernobyl accident was only minor. Contrary to the alpha-emitting Pu isotopes, 241Pu from the Fukushima accident in 2011 was detected in Rovaniemi. Dispersion modeling results with the SILAM (System for Integrated modeLling of Atmospheric composition) model indicate that Pu contamination in northern Finland due to hypothetical reactor accidents would be negligible in the case of a floating reactor in the Shtokman natural gas field and relatively low in the case of an intended nuclear power plant in western Finland.

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

“…During the sampling time of this study, i.e. mid-1990s, the 239+240 Pu/ 137 Cs activity ratio was 0.0393 ± 0.0038 in surface air in Rovaniemi in 1991–1995 (Salminen-Paatero et al 2020 ). This value was slightly higher than in the global fallout at the same time.…”

“…The phenomenon of 137 Cs mainly originating from Chernobyl whilst 239+240 Pu mainly originating from global fallout in environmental samples has been observed in several studies, e.g., in Swiss Alps (Alewell et al 2014 ), Norwegian glaciers (Łokas et al 2022 ), and also in Finnish Lapland (Salminen-Paatero et al 2020 ). The radioactive deposition from global fallout was more uniform than from the Chernobyl accident.…”

“…Furthermore, the deposition area of 137 Cs from the Chernobyl accident was much wider than that of 239+240 Pu and other transuranium radionuclides. For example, the activity concentration of 137 Cs in surface air of Rovaniemi, Finnish Lapland, peaked in April–June 1986, reaching a value of 1294 ± 7 μBq/m 3 , but activity concentrations of Pu isotopes 238 Pu, 239+240 Pu, and 241 Pu were below detection limits in the same sample (Salminen-Paatero et al 2019 , 2020 ). However, it was possible to determine 240 Pu/ 239 Pu mass ratio from this sample, and the value was 0.278 ± 0.093, indicating the presence of Chernobyl-derived Pu in this pooled air filter sample, which was collected during three months after the accident happened (Salminen-Paatero et al 2020 ).…”

“…For example, the activity concentration of 137 Cs in surface air of Rovaniemi, Finnish Lapland, peaked in April–June 1986, reaching a value of 1294 ± 7 μBq/m 3 , but activity concentrations of Pu isotopes 238 Pu, 239+240 Pu, and 241 Pu were below detection limits in the same sample (Salminen-Paatero et al 2019 , 2020 ). However, it was possible to determine 240 Pu/ 239 Pu mass ratio from this sample, and the value was 0.278 ± 0.093, indicating the presence of Chernobyl-derived Pu in this pooled air filter sample, which was collected during three months after the accident happened (Salminen-Paatero et al 2020 ). In the same study, 239+240 Pu/ 137 Cs ratio in the surface air could not be determined for April–June 1986 due to 239+240 Pu having activity concentration below detection limit.…”

Cancer Incidence of Finnish Sami in the Light of Exposure to Radioactive Fallout

“…The Chernobyl accident in 1986 only had a minor effect on air concentration. The major source of Pu-238 in the stratosphere was the burn-up of the SNAP-9A satellite over the South Pacific Ocean in 1964 [10][11][12].…”