THE TRANSFER OF CESIUM-137 AND SR-90 FROM SOIL TO FOOD CROPS AFTER THE CHERNOBYL ACCIDENT

The soil to plant transfer of Cs-137 and Sr-90 was studied at seven locations in Finland over 4 and 2 years, respectively. The plant/soil concentration ratio of Cs-137 for field crops in the southern area (60-degrees-63-degrees-N) ranged from 0.001 to 0.26 and in the northern area (64-67-degrees-N) from 0.01 to 2.29, and that of Sr-90 in the whole area from 0.02 to 2.44. The mean concentration ratio of Sr-90 was about nine times higher than that of Cs-137 in the southern area. The concentration ratio of Cs-137 for leaf vegetables fluctuated between years, and that for carrot, potato and especially cereals decreased gradually after the first year. In the fourth year, the mean concentration ratio of Cs-137 in the southern area was about 60% of the first year value for coarse mineral soils and 80% of that for clay and silt soils. There was no difference in the average Sr-90 ratios between the 2 years studied. The concentration ratio of Cs-137 was lower for clay and silt soils than for coarse mineral soils, and the Sr-90 ratio was lowest for organic soils. The concentration ratio of Cs-137 for vegetables and grain decreased in the order: lettuce, cabbage > carrot, potato > cereals, onion; for fruits in the order: blackcurrant > strawberry > apple, and the concentration ratio of Sr-90 decreased in the order: lettuce, cabbage > carrot, onion > cereals > potato.