Wildfires Oppositely Modify Radiocesium Mobility in Forest Litter and Soils: Evidence from Radiologically...

Area of Science:

• Environmental Science
• Radiochemistry
• Soil Science

Background:

• Wildfires in radiologically contaminated zones raise concerns about radionuclide redistribution and radiation exposure.
• Cesium-137 (¹³⁷Cs) is a key radionuclide of concern, often remaining in soil and charred residues post-wildfire.

Purpose of the Study:

• To investigate the impact of wildfires on cesium-137 (¹³⁷Cs) speciation in forest litter and soils.
• To understand the behavior of ¹³⁷Cs in post-Fukushima nuclear accident environments.

Main Methods:

• Conducted ¹³⁷Cs extraction tests on unburned litter and soil artificially combusted at various temperatures (250, 375, 500 °C).
• Analyzed ¹³⁷Cs leaching from field-collected charred residues and burned soil.
• Performed sequential extraction on post-fire soil samples.

Main Results:

• Water-soluble ¹³⁷Cs in burned litter increased with combustion temperature.
• Artificially combusted soil showed reduced water-soluble ¹³⁷Cs release.
• Field studies indicated lower ¹³⁷Cs leaching from charred residues compared to unburned litter.
• Water-soluble ¹³⁷Cs fractions in burned soil were not significantly different from unburned soil, suggesting limited leaching and potential alteration of exchangeable forms due to organic matter combustion.

Conclusions:

• Wildfire combustion temperatures were likely insufficient to promote significant ¹³⁷Cs leaching or soil drying.
• Wildfires appear to enhance ¹³⁷Cs retention in soil, potentially delaying its long-term release into the environment.