168 DREVINSKY AND PECCI 30 1 25 TTTtTy TTT TIT TT TTT YT TTT - — 20 — = x iw 215 = - 2 — TROPOPAUSE —= x 10 — A X @ © 5 kL 0 10° 30 fogash 10! >0.15 p RADIUS 0.02 TO 0.15 p RADIUS <0.02 » RADIUS TOTAL tt 107 ~] Popp dite pe TOTAL B, NET COUNTS/MIN x G/M? (S.T.P.) TTT y 103 104 TTT 25 ~ 20 be — #15 -- _ = ww ws 5 — = z TROPOPAUSE—t =X 10 _ 5K _] 0 197! fo} pt td 10° on oe 10! Jott tt 5+ CONCENTRATION, DIS/ MIN PER CUBIC METER(S.T.P.) Fig. 4—Radioactivity data for impactor —filter collections over Minneapolis, Minn. (45°N 93°W), on May 16, 1963. 102