GROUNDWATER AND ENVIRONMENT

Geophysical techniques have demonstrated their potential to provide valuable information for hydrogeological and environmental studies. In particular the geoelectrical methods, such as electrical resistivity tomography (ERT) and Spectral Induced Polarization (SIP), have emerged as suitable techniques to permit site characterization with enhanced spatio-temproal resolution.
The Geophysics group is currently  involved in international, and multidiscipline, collaborations aiming at the application of the ERT and SIP techniques at the field scale for hydrogeological characterization (e.g., patterns of the hydraulic conductivity), assessment of contaminated sites (e.g., geometry of contaminant plumes), and the monitoring of biogeochemical processes accompanying remediation of groundwater pollutants (e.g., bioremediation and nano-particles injections).

Figure: Visualization of the electrical properties of the subsurface at the Department of Energy’s Integrated Field Research Challenge (IRFC) Rifle. Electrical Resistivity data were collected to characterize the hydrogeological properties at the floodplain scale with high spatial resolution, aiming at the delineation of aquifer geometry, heterogeneities and preferential flow paths.

 

Characterization of contaminated sites
Ongoing work in our group investigates the application of the Spectral Induced Polarization (SIP), Time-Domain Induced Polarization (TDIP), Ground Penetrating Radar (GPR) and low-induction number Electromagnetic methods. We aim at developing a robust non-invasive methodology for the in-situ characterization of contaminated sites. In particular, our results demonstrate that the Spectral induced Polarization (SIP) imaging method may permit the discrimination of source-zone and the plume of contaminants in case of aquifers affected by organic pollutants. Innovative research lead by Adrián Flores Orozco and Matthias Bücker targets the application of electrical imaging methods for the delineation of changes in pore-space geometry due to geochemical changes in groundwater composition or aquifer sediments.  Further research investigates the development of acquisition techniques for urban areas, characterized by high rates of anthropogenic noise.

Figure: Spectral Induced Polarization (SIP) measurements collected in the grounds of an industrial area (indicated by the gray line in the Figure top-left), characterize by high concentrations of organic contaminants (top-left). The SIP response (top right) revealed a flat spectra and a low polarization effect in areas characterized by high contaminant-concentrations and the occurrence of free-phase. The imaging results revealed significant spatial variations in the polarization effect, most likely due to variations in the pore-space due to the occurrence of free-phase contaminants (Figure bottom),. Further details can be found in Flores Orozco et al., 2012.

Collaborations with:
Prof. Dr. Thilo Hofmann, head of the Department of Environmental Geosciences at the Vienna-University.Prof. Dr. Andreas Kemna, head of the Applied Geophysics group at the University of Bonn.

Monitoring of biogeochemical processes along remediation of contaminated sites
The application of geophysical geoelectrical methods appear as a suitable alternative for the monitoring of processes accompanying the remediation of contaminated sites, as they permit to obtain continuous data (spatial and temporal) about the properties of the subsurface. Hence, geophysical monitoring (e.g., Flores Orozco et al., 2011) may permit to delineate contaminant attenuation and biogeochemical changes induced in the aquifer along remediation.

Current research led by Dr. Adrián Flores Orozco investigates the application of the spectral induced polarization (SIP) imaging method to monitor the injection of metallic particles at the field scale. The injection of nanoparticles for site remediation has become a key research topic in environmental sciences due to the fast degradation of pollutants reported in several studies, and because the remediation can be performed in locations not accessible to other methods. 
Investigations perform by our group aims at developing a geophysical monitoring method, which could provide in real-time information about changes in the pore space geometry and geochemical parameters, as required to improve the efficiency of the available remediation techniques. To achieve this, we work on the improvement of current methodologies for the collection and processing of field-scale monitoring datasets.

Figure: Spectral Induced Polarization (SIP) measurements collected in the grounds of an industrial area (indicated by the gray line in the Figure top-left), characterize by high concentrations of organic contaminants (top-left). The SIP response (top right) revealed a flat spectra and a low polarization effect in areas characterized by high contaminant-concentrations and the occurrence of free-phase. The imaging results revealed significant spatial variations in the polarization effect, most likely due to variations in the pore-space due to the occurrence of free-phase contaminants (Figure bottom),. Further details can be found in Flores Orozco et al., 2012.

Collaborations with:
Prof. Dr. Thilo Hofmann, head of the Department of Environmental Geosciences at the Vienna-University.
Prof. Dr. Andreas Kemna, head of the Applied Geophysics group at the University of Bonn.