492 LOCKHART, PATTERSON, SAUNDERS, AND BLACK — NOVEMBER — DECEMBER 1962 = P low? FUSS. 19627 oN om ey / \ \. PvpU: S- 1962 Oo. ’ < “oO id < ‘ | O ' 2 3 * ~ 1073 Te gJ PRE—1961 | / f \ yn “| if \ \\ * ASSUMED VALUES \ | \ Le \\\ \\s \ / \ T_ a V\ > = ‘ ‘\ Q ‘ / \\ N \ l , \ a / \ / \l — 4 * lo -— | 80°N 60°N | 4CPN i 20°N o LATITUDE | 20°S 40°S 60°S Fig. 11—Profiles of 98&y concentrations in November and December 1962 along the 80th meridian (west). southern hemisphere were observed at the high-altitude collecting station at Chacaltaya, In the March and April collections (profiles not shown) the pat- terns of distribution of Sr in the ground-level air were relatively unchanged from the preceding period. Even at this date negligible pene- tration of the fresher debris to southern Chile had occurred. An estimated 85% of the Sr activity at the three northernmost sites (Thule, Moosonee, and Washington) can be attributed to the U.S.S.R.

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