170 DREVINSKY AND PECCI 30 TOT TTT 25 |- TT TTTTTT x _ SS 20 |=x ur Sst E z + - TROPOPAUSE —— 10 -- 10° 30 25 =pa @ <0.02 » RADIUS 7 o TOTAL Popa riiith 10! TT TTT - — d >0.15 y RADIUS x 0.02 TO 0.15 p RADIUS 5 | 0 ~ x + oy pa 10? tt TOTAL B , NET COUNTS/ MIN x G/M TTT 10° OT ty OT + — He 20} > Sis 215 7 a TROPO PAUSE — 10 F- 107? - ~ 5 0 104 pop tii 107! LoL titty 10° Popeeitit 10! yp ei 90S; CONCENTRATION, DIS/MIN PER CUBIC METER (S.T.P.) Fig. 3—Radioactivity data for impactor —filter collections over Minne apolis, Minn. (45°N 93°W), on Aug. 15, 1963. 10?