soe Nae mA SMTA DR BT he ee ee ae mabe Mr Ne a tatee ree FIGURE I. Pu-239/Sr-90 Ratio at 19.2 km SON [ + | lor 20 ;30 40-F 90 [6ol-* +t 7OoOguLe—1 Ju 1 dy Au dd S O 1967 N OD J F | Mr Ap My Ju Jy Au 1968 S OF N D J F Mr IS69 Ap My CONTOURS ARE IN PERCENT. ARROWS INDICATE THE DATE AND RANGE (SMALL ARROWS-KILOTONS, LARGE ARROWSMEGATONS) OF ATMOSPHERIC NUCLEAR WEAPONS TESTS IN EACH HEMISPHERE.