Disproportionately High Contributions of 60 Year Old Weapons-¹³⁷Cs Explain the Persistence of Radioactive Contamination in Bavarian Wild Boars

Abstract

Radionuclides released from nuclear accidents or explosions pose long-term threats to ecosystem health. A prominent example is wild boar contamination in central Europe, which is notorious for its persistently high 137 Cs levels. However, without reliable source identification, the origin of this decades old problem has been uncertain. Here, we target radiocesium contamination in wild boars from Bavaria. Our samples (2019–2021) range from 370 to 15,000 Bq·kg –1 137 Cs, thus exceeding the regulatory limits (600 Bq·kg –1 ) by a factor of up to 25. Using an emerging nuclear forensic fingerprint, 135 Cs/ 137 Cs, we distinguished various radiocesium source legacies in their source composition. All samples exhibit signatures of mixing of Chornobyl and nuclear weapons fallout, with 135 Cs/ 137 Cs ratios ranging from 0.67 to 1.97. Although Chornobyl has been widely believed to be the prime source of 137 Cs in wild boars, we find that “old” 137 Cs from weapons fallout significantly contributes to the total level (10–68%) in those specimens that exceeded the regulatory limit. In some cases, weapons- 137 Cs alone can lead to exceedances of the regulatory limit, especially in samples with a relatively low total 137 Cs level. Our findings demonstrate that the superposition of older and newer legacies of 137 Cs can vastly surpass the impact of any singular yet dominant source and thus highlight the critical role of historical releases of 137 Cs in current environmental pollution challenges.

Factors of the slow decline in the activity concentration of 137Cs in eutrophic lake water

“…If phytoplankton continue to retain 137 Cs in the lake, there should be a concern about prolonged contamination of organisms with higher trophic levels through the food chain . Long-term persistence of cesium has been confirmed on land, raising concerns about the health of the ecosystem . In order to adequately discuss the importance of phytoplankton, it will be important to quantitatively evaluate the 137 Cs concentration in phytoplankton in the field.…”

137Cesium (137Cs) assessment in wild boars from northwestern Italy

“…In Bavaria wild boar, meats exceeded the regulatory limit by 1–2 orders of magnitude. High contamination values (min 0.37 kBq/kg max 14 kBq/kg–median 1.7 kBq/kg) were still registered several years later (fall 2019 –spring 2020) in the tongue [ 28 ].…”

“…The contamination was widely spread across Europe and in agreement with other sites showed a slower decline than what could be expected considering the half-life of 137 Cs in wild boar meat. This phenomenon is called the “wild boar paradox” [ 28 ]. In addition, it was demonstrated also in a retrospective study for vegetables, water and soils [ 29 ].…”

Development of a Novel Passive Monitoring Technique to Showcase the 3D Distribution of Tritiated Water (HTO) Vapor in Indoor Air of a Nuclear Facility

“…Recently, the discharge of radioactive wastewater from Fukushima into the Pacific Ocean has triggered major concerns about tritium and other radionuclides to the public and the scientific communities. − In the near future, it is expected that anthropogenic 3 H release will keep increasing. For example, some countries are now reconsidering the use of nuclear power against climate change and the energy crisis, with 57 nuclear reactors being under construction worldwide . Moreover, the first net energy gain of fusion reaction implies significant progress in nuclear fusion technology, which might cause additional tritium input into the environment .…”