Abstract
Radiocesium, 137Cs, is one of the most common and dispersed human-made radionuclides. Substantial stocks of 137Cs are stored in organic layers, like soils and peat, as a consequence of nuclear weapons fallout and accidental releases. As climate warming progresses these organic layers are subject to enhanced risks of wildfires, especially in the vast boreal biome of the northern hemisphere. Reemission of 137Cs to the atmosphere is therefore presumed to increase. Here, we experimentally investigated the emissions and redistribution of 137Cs in smoldering fires of boreal soil and peat by varying the oxygen concentration during combustion. For both soil and peat, significantly more 137Cs was released through flaming combustion in 21% O2 (50% and 31%, respectively) compared to smoldering in reduced O2 environments (14% and 8%, respectively). The residual ashes were heavily enriched (>100%) in 137Cs. Hence, after a wildfire induced volatilization of 137Cs, there exists further pathways of 137Cs enriched ash to proliferate in the environment. These results serve as a link between wildfire combustion conditions and the mobility of the 137Cs inventory found in ground fuels of the boreal environment and can be valuable for radiological risk assessments in a warmer and a more nuclear energy reliant world.
Highlights
The boreal biome comprises approximately 30% of the global forests (Brandt et al, 2013)
These results serve as a link between wildfire combustion conditions and the mobility of the 137Cs inventory found in ground fuels of the boreal environment and can be valuable for radiological risk assessments in a warmer and a more nuclear energy reliant world
450 civilian nuclear power plant reactors are in operation globally, and 50 more reactors are under construction (Engler, 2020)
Summary
The boreal biome comprises approximately 30% of the global forests (Brandt et al, 2013). In a scenario of 4 °C global warming, temperature increments of 4–11 °C are expected in the boreal biome. This temperature increase together with an insufficient increase in precipitation are expected to result in a net drying of the boreal biome, increasing the probability of wildfires (Flannigan et al, 2016). 450 civilian nuclear power plant reactors are in operation globally, and 50 more reactors are under construction (Engler, 2020). Eight core meltdowns have occurred in nuclear power plant reactors since the 1950s. History has shown that the frequency of nuclear accidents is higher than first expected, the probability of nuclear power plant disasters has been underestimated (Lelieveld et al, 2012; Rose and Sweeting, 2016)
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