It was just after lunch on March 11, 2011, when disaster struck Japan’s east coast.
A catastrophic magnitude 9.0 earthquake, followed quickly by a massive tsunami, hit Miyagi and Fukushima prefectures and left tens of thousands dead in their wake. Then, as a devastating finale, the Fukushima Daiichi nuclear plant in Ōkuma suffered a series of explosions, releasing toxic radioactive waste into the surrounding environment.
The after-effects of what has become known locally as “3.11” are still being felt today, as Japan scrambles to find ways to deal with the million tonnes of radioactive wastewater and half that of solid waste. But in among all the controversies and high-tech solutions, there is one cleanup program you might have missed: sunflowers.
“We plant sunflowers, field mustard, amaranthus and cockscomb, which are all believed to absorb radiation,” Koyu Abe, chief monk at the nearby Buddhist Joenji temple, told Reuters a few months after the disaster. “So far we have grown at least 200,000 flowers … and distributed many more seeds. At least 8 million sunflowers blooming in Fukushima originated from here.”
But this is far from some Japanese folk wisdom: there is hard science backing it up. Sunflowers, it turns out, are fantastic at cleaning radioactive waste from the environment – which is why they were planted in their droves in the wake of the Chernobyl disaster of 1986.
“Sunflowers are really good at taking up certain radioactive isotopes,” explained soil scientist Michael Blaylock in a 2011 interview. “And that’s really the connection between the sunflowers and the nuclear power plants that we’ve discovered … some of the fallout from the Chernobyl accident we were able to address through planting sunflowers in the affected areas.”
So why sunflowers? The jubilant plants weren’t chosen for their looks – although that’s certainly a bonus. Sunflowers have a whole host of practical properties that make them ideal for the job of nuclear cleanup: they grow quickly, easily, and pretty much anywhere. Even better, they store most of their biomass in the leaves and stems, so the radioactive material absorbed by the plants can be disposed of without having to dig up roots.
Phytoremediation, or the use of plants to clear toxins from the environment, was a huge success at Chernobyl, where the nuclear disaster left nearby soil and water heavy with the radioactive elements cesium and strontium. The process works because the isotopes “mimic” nutrients that the sunflower would naturally absorb – cesium mimics potassium, which plants need for photosynthesis, and strontium passes for calcium, which provides structural support.
“It was very effective for the water,” Blaylock explained. “The soil was a little bit of a different story because cesium in soil is a little bit tricky." "But under the right set of circumstances, they could be effective in removing those contaminants from the soil [in Fukushima].”
Unfortunately, despite the success in Chernobyl, phytoremediation efforts in Fukushima were eventually deemed a failure. Not much literature exists on the experiment, but the few analyses that were carried out failed to find any plant that could effectively reduce the levels of radioactive isotopes in the soil.
To a certain extent, though, this shouldn’t be surprising – there were simply too many differences between Fukushima and Chernobyl for the experiments to work out the same way.
“You know, one thing we found in Chernobyl is, we came there a number of years after the fact. And so that gave plenty of time for that cesium to become fixed in the soil, and it’s going to become very dependant on the soil types,” said Blaylock. “You know, soils that have very high mica contents, certain clays, are going to be very difficult to remove the cesium once the cesium gets fixed.”
But even though the sunflowers couldn’t save Fukushima from the fallout, they still helped the recovery in other ways.
“We’ve been so busy with hundreds of locals coming to collect the flowers,” local villager Tomoe told Reuters after her hometown was left devastated. “It helps me forget about [the] radiation.”