What to do with toxic soil?

Fukushima soil remediation proves promising

Japanese farmer Kenichi Okubo didn’t lose his family farm immediately when the massive TOHOKU EARTHQUAKE hit in March 2011. Even the ensuing tsunami spared his crops from sea water. But the meltdown of the Fukushima Daiichi nuclear reactor, 30 miles away, spewed RADIOACTIVE CESIUM over the fields, and forced the 72-year-old rice farmer and his nonagenarian mother to evacuate.

“The cloud stopped at some hills east of the reactor,” says soil physicist and WSU instructor Colin Campbell ’95. “Then radioactive cesium-137 dropped in snow on this little village called Iitate and surrounding areas.”

Campbell is vice president of Decagon Devices, a family-owned scientific instrument company in Pullman founded by his father, former WSU professor Gaylon Campbell ’68 PhD. Since 1983, the company has made products to measure energy states of water, important for soil quality, food safety, and other uses. In 2007, one of their devices tested soil for water on Mars.

Campbell learned about Okubo and the soil contamination in Fukushima from his colleague and friend Masaru Mizoguchi, a soil scientist at the University of Tokyo.

The Japanese government response was to scrape the top ten centimeters of soil from the area and cart it away, leaving the fields a barren wasteland. However, Mizoguchi knew that cesium will bind onto certain soil particles, like clay, which is prevalent around Iitate. He had a plan to mix the soil and filter it so the heavier clay bound to cesium goes into a containment hole. Okubo and other farmers who returned could then start farming with little to no soil radioactivity.

Mizoguchi turned to Campbell and Decagon Devices for help. They donated sensors and expertise to the project.

Campbell visited Iitate in 2013 to see the progress. “They were just beautiful rice farms carved out in the valleys,” he says. Campbell had studied rice cultivation as a doctoral student at Texas A&M, so he borrowed some boots and joined dozens of retired scientists and university professors to help remediate Okubo’s farm.

Through the course of Mizoguchi’s project, radiation levels dropped significantly and rice grown there was safe to eat.

A few factors confound the operation: cesium washes down from the unremediated hills; the public still suspects crops from Iitate might have radiation; and wild boars dig up the soil and return some cesium.

Still, the process shows promise. Campbell knows it’s not a solution for every incident, but “Okubo is making rice in the land he loves,” he says.