Matthias Kelter, Johan A Huisman, Egon Zimmermann, Andreas Kemna, and Harry Vereecken (2014)
Imaging spectral electrical properties of variably saturated soil columns
In: 3 rd International Workshop on Induced Polarization.
Accurate knowledge about the
spatial distribution of soil h
ydraulic parameters is highly
important for modelling the movement of water and
solutes in saturated and unsaturated soils on
several scales. Electrical impedance tomography (EIT) is a promising tec
hnique to non-invasively
acquire information on hydraulic conductivity, because the measured complex conductivity is
sensitive to soil pr
operties that also contro
l the hydraulic properties (w
ater saturation, porosity,
specific surface and pore/grain size distribution). Ev
en more information is
available if EIT is
performed in a spectral manner (i.e. performing
EIT measurements over a range of frequencies),
which yields information on the spa
tial distribution of the spectral electrical properties of the soil.
Relationships between spectral electrical and hydr
aulic parameters have s
hown strong correlations
in several studies. Our ability to
obtain such distributions of spectra
l electrical parameters in an EIT
inversion approach is influenced by several factors, among which data accuracy, sensitivity and
regularization strength and type
are typically the most importa
nt. Numerical studies of the
reproducibility of spectral electri
cal parameters in an inversion a
pproach showed that an effective
electrical relaxation time should be less affected
by these factors than
chargeability or DC-
conductivity. In order to i
nvestigate this finding experimentally a
nd to test the actual reproducibility
of spectral electrical pr
operties in an imaging approach, EIT measurements were conducted on a
range of packed soil columns with materials whic
h were well defined in terms of their spectral
electrical properties
using effective spectroscopic measurements.