The transfer of cesium-137 and strontium-90 from soil to food crops after the Chernobyl accident.

The soil to plant transfer of 137Cs and 90Sr was studied at seven locations in Finland over 4 and 2 years, respectively. The plant/soil concentration ratio of 137Cs 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 degrees-67 degrees N) from 0.01 to 2.29, and that of 90 Sr in the whole area from 0.02 to 2.44. The mean concentration ratio of 90Sr was about nine times higher than that of 137Cs in the southern area. The concentration ratio of 137Cs 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 137Cs 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 90Sr ratios between the 2 years studied. The concentration ratio of 137Cs was lower for clay and silt soils than for coarse mineral soils, and the 90Sr ratio was lowest for organic soils. The concentration ratio of 137Cs 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 90Sr decreased in the order: lettuce, cabbage > carrot, onion > cereals > potato.