tre id ee Studies of Factors Involved in the Biological Uptake of Radiostrontium Identification of the properties of soil which influence the radiostrontium by biological systems is & prerequisite to und the significance of the deposition of radiostrontium in soil, Dependence of sr89~90 Uptake on Soil Caleium The Beltsville Experiment Station has demonstrated th laboratory soils containing Sr89, the uptake of this isotope is dependent on the exchangeable calcium in the soil in which is grown, They have demonstrated that this is likewise true or radioce barium and the Health and Safety Laboratory has demonstrated ship between radium uptake and exchangeable calcium in soil, relation= If, as the Beltsville experiment suggests, the radiostrontium Fontent of plants is dependent not alone on the amount of radiostrontium fi soil, but on exchangeable calcium as well, a correlation shou betveen exchangeable calcium and the ratio of Sr?9°90 in live to Sr89-90 in soil from which their food is derived. To test this hypothesis, soils from five pastures in various the United States wore analyzed for radiostrontium and exchan calcium. Three lembs and two calves that had spent their ent time in these pastures were sacrificed and samples of sk9 leto Figure 8 is a presentation of our data in the form sr89"90 in in soil versus the reciprocal of exchangeable calsium. These the form which would be predictable from the Beltsville exper a linear regression with a slope of 529 was obtained. Becaus few data, a curve through the points in this figure is not sh ever, a jJeast squares fit of the data gives a slope of 760 wh fair agreement with the Beltsville data considering the few o we have and the possible differences between field and laboratpry conditions, In order to emphasize the importance of the exchangeabls calei yaraneter in the relationship between bone and soil radiostro 9 presents bone radiostrontium versus soil radiostrontium, presented are not so orderly as in comparison with Figure 8. as a data thus Dependence of Ra Uptake on Soil Calcium Ifa similar dependence on exchangeable caloium could strated for natural radium, we would have a useful tool for a the significance of radiostrontium deposition in soils. The world wide Ra in soil is kmown to 4 first approximtion and c determined if need be. The relationship of this deposition + human bone has been 'mder study for some time, Our knowledge bio radium equilibrium could be used to estimate the ultimate radiostrontiume m ve sh = pe demon» be better radium in