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1 Eight adult male volunteers ingested 203Pb as chloride with varying amounts of CaCO3 and NaH2PO4. The uptake from the gastrointestinal tract declined progressively as the amount of minerals taken simultaneously was increased, in agreement with the findings of Blake (1980). 2 With four of the volunteers, further tests were done to compare the effect of the two minerals together and separately. With no minerals, uptake averaged 63.3% (range 58.6-66.7%). The two together (200 mg Ca and 140 mg P) reduced it to 10.6% (range 8.6-12.8%), but neither mineral by itself was nearly so effective as the two together. 3 A lamb was injected with 203Pb and butchered after 6 days. Six volunteers ate the liver or kidneys as part of a meal. Uptake of 203Pb incorporated in the offal averaged 2.8% (range 1.6-4.7%). When 203Pb in solution was taken with inactive offal in a similar meal, uptake averaged 3.0% (range 1.7-3.6%). Thus incorporation of 203Pb in liver or kidney did not affect the uptake.

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This book is about radioactive gases and particles which are dispersed in the environment, either from natural causes, or following nuclear test and accidental emissions. In the first five chapters of this book, the formation and properties of radioactive aerosols are described. Radon, which is of natural origin, is treated at some length, because its contribution to background radiation dose is important. Chapters describe the release of fission products, tritium and plutonium, in bomb tests and nuclear accidents. Particular reference is made to the pathways leading via agricultural products to man. The emphasis then changes to cover experimental aspects of radioactive aerosols. For example, problems in micrometeorology, the study of mass transfer, the mechanics of the human lung and uptake of lead from motor exhausts. Arthur Chamberlain has worked at the Atomic Energy Research Establishment at Harwell for thirty years as the leader of the Aerosol Group. It is a unique exposition and will be used by chemists, geographers, environmentalists as well as governments and other agencies involved in the nuclear debate.

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Measurements have been made in the field and in a wind tunnel of the transport of Lycopodium spores to grass an d other surfaces, and wind tunnel experiments also have been done with aerosols of various smaller particle sizes. The spores and other particles were made radioactive to enable the deposition of small numbers on rough surfaces to be detected. In principle the experiments in the wind tunnel were similar to those previously done with gases (Chamberlain 1966), but the mechanisms by which particles and gases are transported across the boundary layer are different. The velocity of deposition v g of the particle to the surface is equal to the terminal velocity v s if the wind speed is very small, but at higher speeds deposition by impaction on roughness elements becomes progressively more important. If the roughness elements are of a form which gives good impaction efficiency, and have a sticky surface, v g is determined by the rate of eddy diffusion in the turbulent boundary layer above the surface, and may equal or even exceed the analogous velocity of deposition of momentum. The effect of surface texture and stickiness was investigated by comparing the catch of particles on segments of real leaves with the catch on similarity shaped segments of PVG treated with adhesive. Stickiness is important in determining v g for particles of about 10 μ m diameter upwards, but not for smaller particles. In the field experiments, the use of radioactive tagging enabled the presence of a few Lycopodium spores in several grams of grass or soil to be detected, and the deposition could be measured at ranges up to 100 m from the source. At low wind speeds, v g was only a little greater than v s but at higher speeds the contribution of impaction became evident. A particularly high value was obtained when the grass was wet after recent rain. The field results with Lycopodium give a ratio of velocity of deposition to wind speed of 0·01, and this value is used to calculate the percentage of large spores or pollen grains which will travel various distances in normal meteorological conditions. It is found that the median range is about 1 km if the particles are liberated at a height of 50 cm, but 10 km if the height is 10 m. The relative importance of direct deposition to the ground and washout by rain of the air spora is considered, and is shown to depend on the effective height of the cloud of particles. For an effective height of 500 m, derived from vertical profiles of concentration observed from aircraft, it is calculated that about 25% of the total deposition of pollen grains may be in rain.

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