Delineation of subsurface hydrocarbon contamination at a former hydrogenation plant using spectral induced polarization imaging.
Broadband spectral induced polarization (SIP) measurements were conducted at a former hydrogenation plant in Zeitz (NE Germany) to investigate the potential of SIP imaging to delineate areas with different BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations. Conductivity images reveal a poor correlation with the distribution of contaminants; whereas phase images exhibit two main anomalies: low phase shift values (<5 mrad) for locations with high BTEX concentrations, including the occurrence of free-phase product (BTEX concentrations >1.7 g/l), and higher phase values for lower BTEX concentrations. Moreover, the spectral response of the areas with high BTEX concentration and free-phase products reveals a flattened spectrum in the low frequencies (<40 Hz), while areas with lower BTEX concentrations exhibit a response characterized by a frequency peak. The SIP response was modelled using a Debye decomposition to compute images of the median relaxation-time. Consistent with laboratory studies, we observed an increase in the relaxation-time associated with an increase in BTEX concentrations. Measurements were also collected in the time domain (TDIP), revealing imaging results consistent with those obtained for frequency domain (SIP) measurements. Results presented here demonstrate the potential of the SIP imaging method to discriminate source and plume of dissolved contaminants at BTEX contaminated sites.
Department of Geodynamics and Geophysics, University of Bonn, Germany. flores@geo.uni-bonn.de
Adrián
A
Flores Orozco
Andreas
A
Kemna
Christoph
C
Oberdörster
Ludwig
L
Zschornack
Carsten
C
Leven
Peter
P
Dietrich
Holger
H
Weiss
D000393:Air Pollutants / Q000737:chemistry; D001554:Benzene / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D001673:Biodegradation, Environmental; D004784:Environmental Monitoring / Q000379:methods*; D006838:Hydrocarbons / Q000737:chemistry*; D006865:Hydrogenation; D014050:Toluene / Q000737:chemistry; D014992:Xylenes / Q000737:chemistry
D000393:Air Pollutants; D001555:Benzene Derivatives; D006838:Hydrocarbons; D014992:Xylenes; D014050:Toluene; D001554:Benzene; C004912:ethylbenzene