Geoelectrics for Mapping a Buried Waste and Contaminated Ground

7/28/2019 Geoelectrics for Mapping a Buried Waste and Contaminated Ground

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Resistivity and Induced Polarisation forMapping of Buried Waste and

Contaminated Ground

Examples from Sweden and South Africa

Torleif Dahlin, Engineering Geology, Lund UniversityHkan Rosqvist, NSR AB


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Acknowledgements

Work presented was carried out by:

Waterval; Anna Bengtsson (M.Sc. student), Maria Larsson

(M.Sc. student), Andy Fourie (supervisor), Lynette Dollar(supervisor)

Ekeboda; Sonja J ones (M.Sc. student), Bjrn J ohansson

(M.Sc. student), Peter Flyhammar (supervisor) Filborna; Filip Linders

Funding was provided by Sida-SAREC, Lund University,University of the Witswatersrand, Hrby Kommun,NSR AB ...


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Outline

Method

The IP phenomenon

Example Waterval, South Africa

Example Filborna, Sweden Example Ekeboda, Sweden

Summary - Conclusions


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Princ

ipleof

resistivity

surve

ying

(efter Robinson ochCoruh 1988)

A M N B

(Robinson andCoruh1988)


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Automated Multi-electrode Data Acquisition


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Pseudosection

Iterative inversemodelling

FD or FEM model

Presentation of finalresistivity model(s)

Geologic interpretation

Interpretation using

referencedata

Shale

Dolerite

Clayey tillCable trench

Coarse sediments

Shale

Processing and interpretation

of 2D resistivity data

L1-norm or L2-norm optimisation


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Induced polarisation phenomenonPolarization:

[1] redistribution of ions within

electrical double layer ofinterconnected pore surfacefollowing application of electriccurrent[2] relaxation of ions uponcurrent termination

Measured by:[1] decay of induced voltage intime-domain IP equipment

[2] phase shift () betweenvoltage & current waveforms in

frequency domain equipment

Schematic for polarisation of electricaldouble layer of interconnected pore surface

around a single mineral grain

Basis for recent theoretical models,

e.g. Lesmes and Morgan (2001); Leroy

et al. (2008)

Chargeability (IP effect)~surface area


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Alternative / Traditional Interpretation

Frameworks / Pore Scale Models?

Ionic accumulation /mobility reduction at porethroats?Basis of recent theoretical

models (Titov et al., 2002;Zadorozhnaya, 2008)

Ion selective membranesenhanced by clay

particles? (Madden andMarshall, 1959)


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Resistivity and Induced Polarisation (IP)

Measurement cycle

Resistivity is always measured when doing IP surveying.

Backgroundlevel correction important!


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Waterval waste deposit, J ohannesburg

Geology

Localisation in / over oldquarry

Weathered crystallinerocks with fault zones

Geoelectricalimaging

Augering, samplingand analysis


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Waterval waste deposit, J ohannesburg example

Resistivity

IP

Normalised IP

CulvertWaste

Fresh

rock

Sandy soil/dry coverLeachateSoil

Fault

WasteCulvert

Soil cover

WasteCulvert

Soil cover


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Resistivity survey at Waterval waste deposit, J ohannesburg

0 50 100


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IP survey at Waterval waste deposit, J ohannesburg

0 50 100


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4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)

Waterval waste deposit, Johannesburg, South Africa

Depth 0.0-0.5 m


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4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)


Depth 0.5-1.0 m


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Depth 1.0-1.4 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 1.4-1.9 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 1.9-2.4 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 2.4-3.0 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 3.0-3.6 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 3.6-4.3 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 4.3-5.1 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 5.1-6.0 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 6.0-7.0 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 7.0-8.0 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 8.0-9.2 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 9.2-10.5 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 10.5-12.0 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 12.0-13.6 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 13.6-15.3 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Depth 15.3-17.3 m

4 6 10 16 25 40 63 100160250 400

Resistivity(ohm-m)



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Resistivity imaging and water conductivity/resistivityat Waterval waste dump, J ohannesburg

108 mS/m9,3 m

80 mS/m

12,5 m

223 mS/m

4,3 m

323 mS/m3,1 m

(Rosqvist et al 2003)Groundwater conductivity in earlier investigations 38-84 mS/m

ilb l i b


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Filborna, Helsingborg

Resistivity & IP Waste Characterisation

Gypsumdeposit

Mixed wastedeposit


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Filborna Resistivity

Gypsumdeposit

Mixed wastedeposit


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Filborna Induced Polarisation (IP)

Gypsumdeposit

Mixed wastedeposit

Fi ld E l Ek b d W t D it


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Field Example Ekeboda Waste DepositProfil 1 Resistivitet

RMS 3,0%

E l P d ti i ti it / IP Ek b d


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Single cable layoutabase = 2 m

Llayout = 160 m

Itx = 20-200 mA

Rcontact =


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Example Inverted Sections Resistivity / IP Ekeboda

Profil 1 Resistivitet

RMS 3,0%

IP

RMS 1,4%

Norm. IP

RMS 1,4%

C i ith M t t


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Comparison with Magnetometry

Field Example Ekeboda Waste Deposit


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Field Example Ekeboda Waste DepositGradient + bipole-dipole array L1-norm inversion

Ekeboda


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Ekeboda

Normalised IP ~ Extension of Deposited Waste?

Mirrored image

S C l i


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Summary - Conclusions

Resistivity can detect and map leachate contaminatedground / groundwater in 3D

Resistivity results often ambiguous for mapping extent of

waste IP can map / characterise buried waste in 3D

IP more sensitive to noise than resistivity, but IP surveyalways includes resistivity

Normalised IP measure of surface conductivity in soilsand rocks (i.e. without fluid conductivity)

IP decay contains information related to hydraulicproperties of the ground, but more research needed

Std inversion software does not use decay info

Resistivity / IP survey excellent base for designing adrilling / digging and sampling / analysis program

Documents

Geoelectrics for Mapping a Buried Waste and Contaminated Ground