668
THATCHER, PAYNE, AND CAMERON
The North American continent provides the opportunity to study
a meridional traverse over an essentially continental environment, just
as the Pacific provided the same traverse for an oceanic environment.
Data for Fort Smith (CR), Edmonton (CR), Chicago (IA), and Flagstaff
(IA) are averaged for the full year of 1963.
Station
Fort Smith
Edmonton
Chicago
Flagstaff
Location
Mean T.U.
60°01’N, 111°58’W
3836
35°12/N, 111°40’W
1471
53°34’N, 113°31'W
41°47/N, 87°44°W
4193
2333
The tritium concentrations increase toward the north. However,
it is not certain that this is solely a latitude effect.
The
difference
between the Canadian and U. S. sites must be
attributed in part, at least, to the effect of oceanic air from the Gulf of
Mexico; therefore it is not entirely a latitude effect. In other parts of
the world, sites south of Chicago have shown higher tritium averages.
Teheran (35°41'N) averaged 3150 T.U. for the first half of 1963, com-
pared to 2333 T.U. for Chicago. Presumably, Teheran is less affected
by oceanic air masses than is Chicago and is therefore more truly
representative of a continental site at this latitude. Data for eastern
North America (IA, GS) are given in Fig. 9, showing an increasing
oceanic component from Hatteras, N. C., to Ocala, Fla.
Data from South America are incomplete, partly because of the
poor cooperation of national authorities. Large parts of Brazil remain
unsampled. Data from Buenos Aires indicate that higher tritium concentrations may be developing in South America, possibly because of
high-altitude interception by the Andes. The March 1964 measurement of Buenos Aires rain (IA) was 110 T.U., and the April measurement was 86 T.U. In the Falkland Islands relatively high concentra-
tions were measured in 1964 as follows (IA): January, 42 T.U.;
February, 29 T.U.; March, 43 T.U.; and April, 18 T.U.
RATIO OF TRITIUM TO 9°Sr IN PRECIPITATION
The fractionation of tritium from particulate fallout in the course
of global circulation may be observed by comparing tritium and "Sr
deposition at selected sites. As a gaseous molecule, the transport
phenomena for tritium are not identical with the transport phenomena
for Sr, and the investigation of these differences should lead toa
better understanding of the transport mechanisms. The relation be-
tween HTO and “Sr deposition may be observed in Figs. 11 and 12
for typical northern-hemisphere and southern-hemisphere sites, respectively.