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LIMA, PERU
CHACALTAYA, BOLIVIA (ABOUT 17,000 FT
ANTOFAGASTA AND SANTIAGO, CHILE
PUERTO MONTT AND PUNTA ARENAS, CHILE
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5/%Se DECAY IN NORTHERN HEMISPHERE
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JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC
Fig. 5—®Sr/%Sr in air-filter samples in the southern hemisphere in
1968.
seen that the airborne debris at Chacaltaya achieved approximately the
average *Sr/%Sr ratio of the northern hemisphere in June 1963 and
maintained this composition through the next three months. This corre-
sponds
roughly with the annual peak at this site, which was noted
earlier in the discussion of Fig. 3. Whether this material is of southern
stratospheric origin or has moved in from the northern troposphere
cannot yet be clearly determined. The timing of this event, however,
suggests that it is probably the very earliest transfer of debris from
the southern stratosphere and is the onset of the southern-hemisphere
spring peak.
On that basis it then becomes quite clear that the timing of the
annual peaks in fallout deposition is dependent not only upon latitude
and rainfall but also upon the elevation of the sampling site.