<<返回上一页

Take the low road

发布时间:2019-03-08 05:17:14来源:未知点击:

By Rob Edwards SCOTLAND could a very dangerous place to live in the wake of a nuclear accident, a new study has found. Its food—in particular meat and milk—are far more vulnerable to contamination because the country’s peat bogs transfer radioactive caesium to plants, and thence to sheep and cows, far more efficiently than the sandy and clay soils in England and on the Continent. The study was carried out for the European Commission and the British government by Brenda Howard and colleagues from the Institute of Terrestrial Ecology in Cumbria. They found that cattle, sheep, deer and grouse in Scotland have a high risk of long-term contamination after an accident such as that at Chernobyl in 1986. Using data from the aftermath of Chernobyl, the scientists have calculated how much caesium-137 would have to be deposited on soils across Western Europe before the level in milk was likely to exceed the European safety limit of 1 kilobecquerel per litre. The “critical load” for peat is just 80 kilobecquerels per square metre, compared with 470 kBq/m2 for sandy soils and 3370 kBq/m2 for clay (The Science of the Total Environment, vol 221, p 75). The vast majority of Europe’s peat, defined as soils with an organic content between 5 and 30 per cent, is concentrated on the islands and mainland of north and west Scotland. There are also significant areas in the Netherlands, Denmark and Ireland, as well as small patches in Britain in the Pennines, the Lake District and Wales. “The idea is to focus the attention of decision-makers on specific geographical areas,” says Howard. The efficiency with which a soil passes on contamination depends on how well it binds caesium. Particles of caesium become trapped within the structure of clay minerals such as illites and cannot be taken up by plants. Peat contains fewer of these minerals than other soils, so caesium is more available to the grass and heather grazed by animals in Scotland. In the Netherlands, however, Howard points out that the amount of caesium absorbed by plants may be limited by competition with the potassium from fertilisers. Howard’s study is welcomed by the government’s Scottish Environment Protection Agency. “It will help us deal with a nuclear accident,” says George Hunter,