Náttúrufræðingurinn - 1988, Page 23

Sigurjón Rist 1986. Efnarannsókn vatna.
Borgarfjörður, einnig Elliðaár í
Reykjavík. Orkustofnun, Reykjavík
OS-86070/VOD-03. 46 bls.
Stefán Arnórsson, Sven Sigurðsson &
Hörður Svavarsson 1982. The chemist-
ry of geothermal waters in Iceland. I.
Calculation of aqueous speciation from
0° to 370°C. Geochim. Cosmochim.
Acta 46. 1513-1532.
Unnsteinn Stefánsson 1950. Meðalfells-
vatn. Náttúrufrœðingurinn 20. 170-175.
Unnsteinn Stefánsson & Björn Jóhannes-
son 1978. Miklavatn í Fljótum. Nátt-
úrufrœðingurinn 48. 24-51.
Þorleifur Einarsson 1985. Jarðfræði. 5. út-
gáfa, Mál og menning, Reykjavík. 233
bls.
Walling, D.E. & B.W. Webb 1986. Solut-
es in river systems. / Solute Processes
(ritstj. S.T. Trudgill). John Wiley &
Sons Ltd. New York. 251-327.
Veðurstofa íslands 1958-1987. Mælingar á
nokkrum efnum í úrkomu og andrúms-
lofti. / Veðráttunni 1958-1987.
SUMMARY
Chemistry of rivers in Iceland and
the rate of chemical denudation
by
Sigurður R. Gíslason and Stefán Arnórsson
Science Institute
University of Iceland
Dunhagi 3
IS-107 REYKJAVÍK
Iceland
The rate of chemical denudation in Ice-
land is at least two times that of the conti-
nents. This is because of high precipita-
tion and run-off and the abundance of re-
active glassy basaltic rocks in Iceland.
Temperature, discharge and total dis-
solved solids are stable in spring-fed rivers
but not in direct run-off and glacier-fed
rivers. The pH of direct run-off rivers and
glacier-fed rivers ranges from 7 to 7.5 and
is controlled by the dissociation of the
aqueous C02 species. The pH of the
spring-fed rivers ranges from 8.5 to 9.5
and is controlled by the dissociation of the
aqueous monomeric silica species. The
spring waters are undersaturated with re-
spect to the C02 of the atmosphere. At-
mospheric C02 dissolves downstream in
the spring-fed rivers and can simultan-
eously lower the pH of the water. How-
ever, the time available for the dissolution
of atmospheric C02 is short, less than one
day, so relatively short spring-fed rivers
can maintain high pH all the way to the
river mouth. The same applies for the dis-
solution of suspended load in the main
stream of the rivers. The time for dissolu-
tion is less than a day, and therefore does
not have a significant effect on the amount
of total dissolved solids in the main
stream.
197