Fukushima wheat: throw current harvet away, but OK to plant again

On the radiological impact on the food chain I blogged on the cesium tainted beef making it all the way to consumption in Tokyo. This week also saw a counter trend in cereals and vegetable reported. NatureNews reports:

Soon after the meltdown at Fukushima Daiichi, the government evacuated people living within 30 kilometres of the plant, and later imposed restrictions on agricultural products. Those measures are still in place, and the government has not yet announced a clear strategy for dealing with the contaminated areas. “People are panicking because there are no data,” says plant radiophysiology expert Tomoko Nakanishi at the University of Tokyo.

Nakanishi is coordinating seven teams to study the impact of the disaster on soil, plants, animals, fisheries and forests for the next decade, measuring contamination levels and assessing the long-term threat. Their first results, to appear in the Japanese journal Radioisotopes in August, paint a surprisingly optimistic picture.

The scientists studied crops at a Tokyo research field, including cabbages and potatoes that were planted a few weeks after rains showered the field with radioisotopes from Fukushima. The crops were harvested on 16 May, and contained low levels of radiation — around 9 becquerels per kilogram (Bq kg–1; wet weight), much lower than the 500 Bq kg–1 safety limit for human consumption. Furthermore, most of the radiation had accumulated on the leaves and could be washed off, suggesting that the plants were not absorbing dangerous levels of radioisotopes directly from the soil.

The more highly exposed fields around Fukushima showed similar results, with most of the radiation in plants accumulated on their surfaces. Wheat leaves that were open at the time of the greatest fallout were heavily contaminated, with combined levels of caesium-134 and caesium-137 ranging from thousands to about 1 million Bq kg–1. But leaves that unfolded afterwards were largely free of contamination. Wheat ears from these plants contained 300–500 Bq kg–1 — within the prescribed radiation limit. “It’s harvest time now and farmers are wondering what to do,” says Nakanishi. “They can throw the current harvest away. But it is OK to plant again.”

Despite this good news, the team’s data also show that the radioisotopes seem to be stuck firmly to the soil, mainly in the top five centimetres, and are not being washed away by rain. This might prevent the radioisotopes from entering groundwater, but suggests that cleaning up the more radioactive public spaces in Fukushima prefecture will not be easy.

My humble opinion: One of the consequences of the Fukushima disaster will be long-term disruption and security concerns in the food chain, both land and ocean based.

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