166 80 TTTTTT ax 25 4 s 20 t+ = x ws — O 15;— EFe Z 19 |. TROPOPAUSE ae > F- ob 10° 30 a X ] A >0.15 p RADIUS X 0,02 TO 0.15 p RADIUS ® <0.02 p RADIUS top rit 10! > © TOTAL pop pil fb pat a 10? 103 104 TOTAL B7, NET COUNTS/MIN X G/M3(S.T.P.) TTT TT TTT (=. me | x Iw x a > 15 -& x < 19 LTROPOPAUSE = a 5 7 poop pt 10! 10 10° M4Ce CONCENTRATION, DIS/MIN PER CUBIC METER (S.T.P.) 104 aT ALTITUDE, KM 10° — — he 0 10° 10 }- TROPOPAUSE — 0 107! — =o Lett] [ ttyl i jit 10° 10! 107 9S, CONCENTRATION, DIS/MIN PER CUBIC METER (S.T.P.) Fig. 2—Radioactivity data for impactor —filter collections over Minneapolis, Minn. (45°N 93°W), on Mar. 16, 1962.