Hydrology and Earth System Sciences
www.hydrol-earth-syst-sci.net
1027-5606
1607-7938
11
5
2007
10.5194/hess-11-1621-2007
http://www.hydrol-earth-syst-sci.net/11/1621/2007/
http://www.hydrol-earth-syst-sci.net/11/1621/2007/hess-11-1621-2007.html
http://www.hydrol-earth-syst-sci.net/11/1621/2007/hess-11-1621-2007.pdf
1621
1631
2007-09-28
Tracing and quantifying groundwater inflow into lakes using a simple method for radon-222 analysis
T. Kluge
tobias.kluge@iup.uni-heidelberg.de
J. Ilmberger
C. von Rohden
W. Aeschbach-Hertig
Institute for Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany
Due to its high activities in groundwater, the radionuclide <sup>222</sup>Rn is a
sensitive natural tracer to detect and quantify groundwater inflow into
lakes, provided the comparatively low activities in the lakes can be
measured accurately. Here we present a simple method for radon measurements
in the low-level range down to 3 Bq m<sup>−3</sup>, appropriate for
groundwater-influenced lakes, together with a concept to derive inflow rates
from the radon budget in lakes. The analytical method is based on a
commercially available radon detector and combines the advantages of
established procedures with regard to efficient sampling and sensitive
analysis. Large volume (12 l) water samples are taken in the field and
analyzed in the laboratory by equilibration with a closed air loop and alpha
spectrometry of radon in the gas phase. After successful laboratory tests,
the method has been applied to a small dredging lake without surface in- or
outflow in order to estimate the groundwater contribution to the
hydrological budget. The inflow rate calculated from a <sup>222</sup>Rn balance
for the lake is around 530 m³ per day, which is comparable to the
results of previous studies. In addition to the inflow rate, the vertical
and horizontal radon distribution in the lake provides information on the
spatial distribution of groundwater inflow to the lake. The simple
measurement and sampling technique encourages further use of radon to
examine groundwater-lake water interaction.
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