Wildfires in Ukraine could revive Chernobyl's radiation

CHERNOBYL, Ukraine, Feb. 9 (UPI) -- When the Chernobyl Nuclear Power Plant exploded in 1986, some 85 petabecquerels of radioactive cesium was released into the atmosphere and surrounding environs. Researchers believe somewhere between 2 and 8 PBq is still lingering in the soil and forest debris that surrounds the disaster site.

Scientists have long feared that forest fires could send leftover radiation back into the atmosphere as radioactive leaves and other dead and dry plant material burn up -- traces of cesium wafting skyward in the plumes of smoke. Now, a new study confirms these fears, suggesting forest fires can and will enable radiation to accumulate in clouds and travel across Eastern Europe.

Some climatologists suggest global warming could encourage an uptick in forest fires. To better understand how such a trend might affect the redistribution of Chernobyl's radioactive soil and debris, scientists built a computer model using forest fire and cesium exposure data. Their simulation showed that a combo of fire and air movements could move radiation from Chernobyl's forests across much of Eastern Europe, especially Ukraine, Russia and Belarus. The models also showed radioactive clouds could carry traces of cesium as far away as Turkey (to the south), as well as Italy and Scandinavia (to the west).

Researchers say the model showed forest fires could currently be delivering as much as an extra 10 microsieverts of radiation -- just 1 percent of the yearly exposure amount deemed safe by public health officials -- to the residents of Kiev.

"This is very small," study co-author Tim Mousseau, a researcher at the University of South Carolina, told the New Scientist. "But these fires serve as a warning of where these contaminants can go. Should there be a larger fire, quite a bit more could end up on populated areas."

The study also found that radioactivity in leaf litter on the forest floor is building up fuel for more fires because the leaves are not decomposing normally, possibly because the radioactivity has killed insects and microorganisms that break them down.

The study isn't so much an attempt to sound the panic alarm, but a reminder of how slow-decaying radiation can continue to find its way into new environments long after its original release.

"This is clearly an important problem and one that applies also to Fukushima, where a significant amount of forest land has been contaminated," said Keith Baverstock, the former head of radiation protection in Europe for the World Health Organization. Baverstock, who did not participate in the study, is currently a researcher at University of Eastern Finland.

"They have a very valid point," Baverstock said. "The lack of management of forests, the apparently slower decay of vegetation exposed to radiation, climate change leading to drought and the expansion of forested areas all contribute to increasing the risk of forest fire and therefore further dispersal of long-lived radioactive nuclides."

But even if the study's main takeaway is an improved understanding of the movement of radioactive elements (and not necessarily heightened health risks), researchers say it's important not dismiss the public health component.

"A growing body of information supports the idea that there is no threshold below which they have no effect," Mousseau said.

Researchers noted that fires also redistribute other radioactive elements, including strontium, plutonium and americium -- all of which can accumulate in food, if not expose humans and animals directly.

The study was published in the latest issue of Ecological Monographs.