Radioactive fallout in air and rain: results for 1985 and 1986

Samples of atmospheric particulate and rainwater have been collected from the United Kingdom and elsewhere. Results are presented of analyses of these samples for various fission products and certain other radionuclides. The average concentrations of long-lived fission products in air and rain in the United Kingdom in 1985 were near to or below the limit of detection and lower than at any time since measurements began in 1953. The Chernobyl accident of 26 April 1986 produced a sharp increase in the concentrations of caesium-137 in air and rain in the northern hemisphere. Levels of Cs-137 in some parts of the United Kingdom were greater than any previously recorded. Plutonium concentrations in air and rainwater were a very small fraction of the NRPB's Generalised Derived Limit for members of the public. There was negligible contribution from the Chernobyl accident. Strontium-90 deposited in the United Kingdom in 1985 was below the limit of detection. The deposits in 1986 were generally about 2% of that from Cs-137. The estimated cumulative worldwide deposit of Cs-137 at the end of 1986 is about 10% greater than at the end of 1985. This increase is attributable to the Chernobyl accident. The gamma and beta-ray dose rates from fallout at Chilton are estimated from the observed deposition. (author)