Jökull - 01.12.1962, Side 55

thermal water the first changes to be observed
in the wells will be a change of the isotopic
concentration. Temperature changes will ap-
pear later due to an exchange of lieat between
the cold water ancl the hot rock. The isotopic
concentration in the thermal water may, there-
fore, be an important indicator of unwanted
or dangerous changes in the pattern of flow
in the heat reservoir.
Tritium. The application of tritium for the
determination of the “age” of natural water
has been discussed above.
The injection of synthetic tritium can be
used for limited areas in hydrology. The method
is applicable to the study of the underground
flow pattern and for a ground-water inventory
in general.
PRELIMINARY RESULTS IN ICELAND
Dr. Harrnon Craig, Scripps Institution of
Oceanography, has analysed the isotopic con-
centration in a number of samples of thermal
ancl surface water collected in Iceland in 1954
by the writer. The samples were collected in
the region around Reykjavik ancl Akureyri as
shown in Fig. 1. In Fig. 2 a rnore detailed
picture is given of the location of the samples
from the Reykjavík region.
The results of the analytical work are given
in the table below where the data on the iso-
topic concentration are given as deviations
from a standard sample which is taken from
Lake Michigan in U.S.A. The table gives also
the surface temperature and flow of the springs
from which the samples were taken.
The isotopic data are plotted in Fig. 3 where
AD is plotted against AO18. This is the com-
mon way of illustrating data of this kind.
Moreover, the concentration of F ancl SÍO2
in the samples are given in the same table.
The concentration of these components ap-
pears to depend on the temperature conclitions
in the individual thermal areas. Their con-
centration increases with increasing tempera-
ture.
Finally, the table contains a few data on the
tritium concentration in samples analysed by
Dr. F. Begemann then at the Enrico Fermi
Institute for Nuclear Physics at the University
of Chicago.
Four important results can be derived from
the data given in the table.
Isotopic composition of natural ivater in Iceland.
Isotope Analysis: Dr. Harmon Craig and Dr. F. Begernann.
The isotopic data are given as deviations from a standard sample.
Location Temp. FiowxlO”3 AD AO18 F Si02 T/HxlO18
Reykjavík area °C cm3/sec % %0 p.p.m. p.p.m.
Surface water
(1) River Ellidaár (2) River Varmá - 1.4 - 1.7 - 7.9 - 8.0 0 10
Thermal water
(3) Álfsnes .... 30 1 -2.8 - 9.9 1.1 87
(4) Laugarnes .... 87 15 -2.7 - 9.8 1.0 125 1.1 ± 0.1
(5) Raudará .... 91 O -2.6 - 9.5 1.1 130
(6) Norclur-Reykir .... 87 180 -2.7 - 9.6 1.1 91
(7) Sudur-Reykir (8) Blikastadir 87 . .. . 22 160 0.2 -2.4 -2.5 - 9.1 - 9.3 0.2 22
(9) Breidholt , .. . 30 1 -2.1 - 9.0 0.5 63
Akureyri area (Kristnes)
(10) Surface water (11) Kristnes ... 75 1.5 -4.8 -7.0 - 11.2 - 13.7 0.7 110 18.4 ± 1 6.1 ± 0.4
Hveragerdi area
(12) Well ... 100 -2.4 - 6.9 1.1 340 3.5 ± 0.3
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