Specific Fall-out Activity in Precipitation as a Function of Sampling Height

Abstract

IN 1956–57 Herbst et al. ¹ found a definite increase with height in the fall-out activity in vegetation from an altitude of 800–1,000 m. and upwards. This was ascribed partly to the slow growth of the vegetation with increasing height and consequently greater accumulation of activity on it, and partly to greater fall-out at increased heights. Small² suggested in 1958 from examination of the variations in the natural activity of the air (radium B and C), compared with the meteorological conditions at ground-level, that during inversion conditions the vertical transport of bomb debris from above would decrease. By comparing the fall-out in a precipitation collector situated in the top of a 123-m. mast with that in corresponding collectors at ground-level, I found³ for the period September 1958–March 1959 more fall-out in the former than in the latter.