Hydrology and Earth System Sciences
www.hydrol-earth-syst-sci.net
1027-5606
1607-7938
8
1
2004
10.5194/hess-8-8-2004
http://www.hydrol-earth-syst-sci.net/8/8/2004/
http://www.hydrol-earth-syst-sci.net/8/8/2004/hess-8-8-2004.html
http://www.hydrol-earth-syst-sci.net/8/8/2004/hess-8-8-2004.pdf
8
22
0000-00-00
Groundwater redox conditions and conductivity in a contaminant plume from geoelectrical investigations
V. Naudet
A. Revil
E. Rizzo
J.-Y. Bottero
P. Bégassat
CNRS-CEREGE, Dept. of Hydrogeophysics and Porous Media, Aix-en-Provence, France
CNRS-CEREGE, Dept. of Interfacial Chemistry, Aix-en-Provence, France
ADEME, 2, Square La Fayette BP 406, Angers, France
E-mail for corresponding author: revil@cerege.fr
Accurate mapping of the electrical conductivity and of the redox potential of
the groundwater is important in delineating the shape of a contaminant plume. A map of redox
potential in an aquifer is indicative of biodegradation of organic matter and of concentrations
of redox-active components; a map of electrical conductivity provides information on the
mineralisation of the groundwater. Both maps can be used to optimise the position of pumping
wells for remediation. The self-potential method (SP) and electrical resistivity tomography
(ERT) have been applied to the contaminant plume associated with the Entressen landfill in
south-east France. The self-potential depends on groundwater flow (electrokinetic contribution)
and redox conditions ("electro-redox" contribution). Using the variation of the piezometric
head in the aquifer, the electrokinetic contribution is removed from the SP signals. A good
linear correlation (R<sup>2</sup>=0.85) is obtained between the residual SP data and the redox potential
values measured in monitoring wells. This relationship is used to draw a redox potential map
of the overall contaminated site. The electrical conductivity of the subsoil is obtained from
3D-ERT analysis. A good linear correlation (R<sup>2</sup>=0.91) is observed between the electrical
conductivity of the aquifer determined from the 3D-ERT image and the conductivity of the
groundwater measured in boreholes. This indicates that the formation factor is nearly
homogeneous in the shallow aquifer at the scale of the ERT. From this correlation, a map of
the pore water conductivity of the aquifer is obtained.</p>
<p style="line-height: 20px;"><b>Keywords: </b>self-potential, redox potential, electrical resistivity tomography, fluid
conductivity, contaminant plume