INFLUENCE OF AGE OF RADIOACTIVE FALLOUT MATERIAL UPON ITS DEPOSITION IN MILK AND VERTICAL DISTRIBUTION IN SOIL
Milk samples from Jersey and Holstein cows analyzed for /sup 90/Sr and Ca and Sr unit (SU) values during the spring and summer of 1961 showed that the SU values ( mu mu C /sup 90/Sr/g Ca) were significantly higher in the spring (April--May 196l) than in the samples (July--August 1961). This difference may have been due to a higher Ca intake during pasture feeding in the summer or because during the spring months the cows were fed silage and hay grown in the summer of 1960, when the /sup 90/Sr fallout in Ontario was relatively higher than in 1961. The difference in the fallout rate between the spring and summer periods probably explained the higher levels of /sup 90/Sr in the spring milk samples. In a further investigation using the same cows, milk samples were obtained six weeks after the first announced resumption of an atmospheric nuclear detonation in October 1961, about two months after the collection of summer samples from July 17 to August 18. The data were examined to seek evidence whether /sup 89/Sr, /sup 90/Sr, and SU values of milk increased from the summer to the fall sampling periods, and whether an increase in the amount of atmospheric /sup 89/Sr and /sup 90/Sr was similarly reflected in the isotope content of the milk sample of the two breeds of cows. Milk samples showed consistently higher SU and /sup 90/Sr values in October than in August 1961, and the presence of /sup 89/Sr was evidence of fresh fallout, proving that the delay period for introduction of Sr in milk is less than two months. The soil samples taken from the site where the cows grazed showed no increase of /sup 90/Sr and no evidence of /sup 89/Sr. In grass, however, there was a sharp increase of both isotopes from September to November 1961, the simultaneous rise suggesting recent pollution. The effective delay period, therefore, for fallout to be incorporated into grass was less than two months. That there was no increase in either isotope in the soil suggests that the isotopes entered the vegetation by direct routes. The average SU values were higher in Holstein milk than in milk obtained from the Jersey cows tested. In the October samples the mean SU values were 2.358 for Holstein milk as compared with 1.987 for Jersey samples. This significant difference was most likely due to the consistently higher levels of Ca in Jersey milk in October 1961 (1.380 g/l for Jersey, and 1.150 g/l for Holstein milk). Data for soil and grass concentrations of the isotopes are tabulated. (BBB)
- Research Organization:
- Univ. of Toronto, ON (Canada)
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-018045
- OSTI ID:
- 4034944
- Journal Information:
- Journal of Dairy Science (U.S.), Vol. Vol: 47; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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