Flames fan lasting fallout from Chernobyl

by Mary Caperton Morton
Monday, May 4, 2015

Forest fires in the Chernobyl Exclusion Zone have the potential to spread radioactive contamination as far as Turkey and Scandinavia. Credit: ©Hrebenjuk Oleksandr, CC BY-NC-SA 2.0.

On April 26, 1986, the Chernobyl nuclear power plant in Ukraine exploded during a catastrophic meltdown, spewing radioactivity over Eastern Europe and forcing evacuations of thousands of people. Nearly 30 years later, the scar of the Chernobyl disaster remains in Belarus, Russia and Ukraine in the form of the 2,600-square-kilometer Exclusion Zone, which is choked with dead trees and overgrown brush contaminated with high levels of radioactive cesium, strontium and plutonium. Occasional wildfires in these woods send plumes of smoke laced with potentially harmful radionuclides into the atmosphere. Now, a new study finds that climate change will likely increase the frequency and intensity of these fires, further increasing the possible hazard.

“The first time I visited Chernobyl I was struck by the sheer number of downed trees and the amount of leaf litter. It seemed nothing was decomposing,” says Timothy Mousseau, a biologist at the University of South Carolina in Columbia and a co-author of the new study, published in Ecological Monographs. In previous studies, Mousseau and his colleagues found that reduced microbial activity in the Exclusion Zone leads to slower than expected rates of decomposition of dead plant matter.

This plant debris has fueled many blazes over the years. After the initial fires sparked by the 1986 blast, a series of naturally ignited forest fires broke out in 1992, burning more than 170 square kilometers of trees. In the 2000s, more fires sent plumes of contaminated smoke high into the atmosphere.

To study how far these plumes can carry radioactive materials, and how climate change may affect the fire hazard around Chernobyl, Mousseau’s team combined satellite images of fires in 2002, 2008 and 2010 with field measurements of radioisotope levels measured in and around the Exclusion Zone to model changes in the distribution of radiation over the region. The researchers found that previous fires likely spread radiation across much of Eastern Europe, with Ukraine, Belarus and Russia receiving the highest doses. Traces of radioactive cesium-137 may have even traveled to Turkey, Italy and Scandinavia.

The models predicted that the recent fires could have each delivered as much as 10 microsieverts of radiation — about 1 percent of the yearly exposure deemed safe by U.N. public health officials — to the residents of Kiev, Ukraine, located 100 kilometers south of the Exclusion Zone. “This sounds like a small amount, but these fires serve as a warning of how far radioactive contaminants can go,” Mousseau says. “Should there be a larger fire, quite a bit more could end up on populated areas.”

The team also found that a shift to a hotter, drier climate will likely increase the frequency and intensity of the fires in the coming decades. “Precipitation patterns are changing in the area of Chernobyl, and the probability of large catastrophic forest fires will increase over time,” Mousseau says.

This modeling study emphasizes the widespread implications of radioactive wildfires, says Johann Goldammer, a fire ecologist at the Global Fire Monitoring Center in Freiburg, Germany, who was not involved in the study. Unfortunately, he notes, predicting how the fire hazard may change in the future does little to help confront the current risk to people in affected areas. The danger from the Chernobyl fires is well known, he says, and the difficulties of fighting the fires on the ground are intractable.

“It has been a struggle over many decades to hold somebody responsible for dealing with the hazards of this fallout zone,” Goldammer says. “Ukraine is too unstable politically and financially to bear the weight, and nobody — nationally or internationally — has taken responsibility for managing these fires.”

Fighting such fires is extremely dangerous for workers, who risk ingesting or breathing radioactive contaminants. The Global Fire Monitoring Center is “looking at unmanned technologies for fire management that would minimize the risk to foresters and firefighters,” Goldammer says. “The hope is to develop some techniques for reducing fuel sources and to be more proactive in preventing these fires, rather than trying to deal with them once they’re burning.”

The new study makes some recommendations for better managing the fire risk at Chernobyl, such as installing video cameras that allow closer monitoring of the forests without exposing workers to radiation, as well as remote warning systems to detect high levels of radiation. But most recommendations offered have already “been on the table at one time or another,” Goldammer says. What’s needed now is “more work on the ground, if we’re ever going to get ahead of these fires.”

Mousseau agrees that more on-the-ground efforts are needed, but says that studies such as this can help keep the problem in the public and scientific eye. “Chernobyl happened so long ago that most people have forgotten about it,” he says. “These kinds of studies show that [Chernobyl’s radiation] is still a problem.”

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