The blue hills of Snowdonia


By KEVIN BREWER Hills and uplands in Wales and northwestern England could soon turn from green to navy blue as scientists try to ‘lock up’ radioactive caesium deposited by rain after the Chernobyl disaster. Seven years after the world’s worst nuclear accident, vegetation in parts of Snowdonia and Cumbria still contains high levels of radioactivity. The biggest culprit is caesium-137 which is being taken up by plants. Research at the Institute of Grassland and Environmental Research in Aberystwyth has found that spreading certain minerals over contaminated land can fix caesium in the soil, preventing plants from taking it up. But the best substance tested so far is ammonium ferric hexacyanoferrate, or Prussian blue, which turns the hills blue. Dafydd Rhys Jones of IGER says that 80 per cent of the radioactive contamination is still in the soil. Caesium-137 has a half-life of 30 years and, he says, if no action is taken, government controls on sheep grazing the affected areas will have to stay ‘for the foreseeable future’. Hundreds of farmers still work under post-Chernobyl regulations imposed in 1986. Sheep being moved from a restricted area that are found to have radioactivity higher than 1000 becquerels per kilogram are deemed ineligible for slaughter for their meat, and are marked with paint. Radio-activity levels fall quickly once sheep stop eating contaminated grass and within a few months all marked sheep are released from the safety controls. Experiments funded by the Ministry of Agriculture, Fisheries and Food are now under way on the Carneddau mountains of Snowdonia and the Cumbrian hills at Corneyfell, near Bootle, to see if decontamination zones can be created where lambs can be taken to lose their radioactivity before slaughter. Besides Prussian blue, other minerals being tested are potassium chloride and the clay minerals bentonite and clinoptilolite. Caesium concentrations in plants growing in areas treated with the potassium salt fell sharply, but the substance also acted as a fertiliser. ‘This causes some concern,’ says Jones. ‘Potash could have long-term environmental effects by changing the botanical composition of these ecosystems.’ Prussian blue worked on both sites,
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