SCOTLAND could a very dangerous place to live in the wake of a nuclear
accident, a new study has found. Its food鈥攊n particular meat and
milk鈥攁re far more vulnerable to contamination because the country鈥檚 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 鈥渃ritical load鈥� 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).
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The vast majority of Europe鈥檚 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. 鈥淭he idea is to focus the attention of decision-makers on
specific geographical areas,鈥� 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鈥檚 study is welcomed by the government鈥檚 Scottish Environment
Protection Agency. 鈥淚t will help us deal with a nuclear accident,鈥� says George
Hunter, SEPA鈥檚 head of radiation policy. 鈥淏ut it needs expanding to include
other radionuclides.鈥�
The highest concentration of caesium in British food after
Chernobyl鈥攁lmost 7 kilobecquerels per kilogram鈥攚as found in a grouse
from the Scottish Highlands in 1987. Over 47 000 sheep on 23 farms in Scotland
are still subject to restrictions on their slaughter and movement because of
contamination from Chernobyl.