Wildfires in radioactive areas found to heighten river contamination risks

Wildfires in radiologically contaminated areas pose substantial risks, such as the redistribution of radionuclides and increased radiation exposure for residents. A team of researchers from the University of Tsukuba investigated the effects of a large wildfire that occurred in April 2020 within the Chornobyl exclusion zone in Ukraine, focusing on the redistribution of ¹³⁷Cs and ⁹⁰Sr in the rivers flowing through the region.

The researchers analyzed the charred residues and soil collected from the area post-fire to determine the fractions of ¹³⁷Cs and ⁹⁰Sr. They also examined long-term monitoring data on the concentrations of these radionuclides in rivers. The research is published in the journal Environmental Science & Technology.

The results showed that the concentrations of ¹³⁷Cs and ⁹⁰Sr in charred residues and soil decreased as the distance from the Chornobyl Nuclear Power Plant increased, following the pattern of initial deposition after the 1986 Chornobyl nuclear accident. Leaching tests further showed that the water-soluble forms of ¹³⁷Cs and ⁹⁰Sr were substantially higher in the charred residues than in the soil, indicating that the wildfire enhanced the mobility of these radionuclides.

Although no notable increase in the ¹³⁷Cs concentration was observed in the Chornobyl River basin before and after the fire, the ⁹⁰Sr concentration increased considerably, exceeding the permissible limit of the radionuclide concentration for drinking water in Ukraine (2 Bq/L). This increase is likely due to ⁹⁰Sr leaching from charred residues and soil into the river.