250 Ba!in Pittsburgh Fallout 200 +| ° Pure tropospheric = 300 for Ba'*°/Sr° : % Sr *°/ Ba' Pure stratospheric = O for | (NSEC Data) Activity Ratio (Ba'49/ Sr 9°) 150 100 | = i } sn r 3! : | ! | ; ge [8 ¢ ; rr t 3 § 6 t y $ o§ o e 2 “yg __* §otc ———*+ [Leo b | att te i _sfamoasoog_2o APRIL SEPT, OCT. . NOV. DEC, JAK, FER, MAR, “APRIL MAY JUNE SLY, AUG. SEPT. 1957 1958 Figure 9 'y r« lof ttttinal

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