-5they arrive at the lower tropospheric levels. .- Ultimate Br’? soil concentration, if present tropospheric activity levels are maintained> 7 (= Ga x 207) e207) = 2x20! ayn/te.? - or, by miltiplying by 2.8 x 107 £t2/mt® = 5.6 x 102La/ms® ¥ | and, by dividing by 2.2 x10? d/m/me := 2.5 x0 ne/mi® . ir the present level has beena existence for 3 years and if negligible a”1 levels were encountered prior to thie: - . - _presdnt a? soillevel at Woshington,De. yee. * (2.5.x: 10° mo/mi? )x (1.eat) oo . | vhere x) =BB | and +t “ 3 yr. = 0.07 (2.5 x 10” m¢/mt?) | z= 17 mC/mt2 - | These calculatias consider only that rein is the principle mechanism of ex’? end BaD deposition and that similar efficiencies are obtained. for either RaD or gr’? would serve ag @ check on these values. Soil analysis | _ Libbey, in an address defore the American Physical Society, Philadelphia, Pa. April 20, 1956, reported average total deposit of Br’. in US to be about 13 me/mi*,Ww which is in reasonable agreemrit with the 17 me/mi= we estimated for a year leer. ny