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- Title
Mapping and Monitoring of DNAPL Source Zones With Combined Direct Current Resistivity and Induced Polarization: A Field‐Scale Numerical Investigation.
- Authors
Almpanis, Angelos; Gerhard, Jason; Power, Christopher
- Abstract
Direct current (DC) resistivity has been widely investigated for non‐invasive mapping of dense non‐aqueous phase liquids (DNAPLs); however, due to its difficulty in distinguishing DNAPLs from adjacent soils, the DC method is limited for static detection of DNAPLs and more often employed for monitoring DNAPL changes over time. Time‐domain induced polarization (IP) can provide complementary information to better discriminate between DNAPL, water and surrounding soils. Since highly resistive DNAPLs tend to laterally spread and pool on polarizable (chargeable) clay lenses, combined DC and IP (DCIP) has the potential to enhance static detection, and also monitoring of DNAPL source zones (SZs). The objective of this study is to assess DCIP for characterizing and monitoring DNAPL SZs at the field‐scale. A new DNAPL‐DCIP numerical model was first developed that couples a 3D multiphase flow model, which simulates DNAPL release and remediation scenarios, with a 3D DCIP model, which calculates the corresponding resistivity and chargeability response. The sensitivity of the DCIP response to key DNAPL and soil properties was then analyzed at a single subsurface location, closely matching previous theoretical and experimental observations. Finally, a field‐scale simulation of DNAPL release and remediation was conducted, with simultaneous mapping by DCIP surveys. Results demonstrate that chargeability can provide enhanced understanding of the lithological distribution that controls the variability in the DNAPL SZ, with time‐lapse resistivity being used to monitor DNAPL mass changes during SZ remediation. This numerical study suggests that combined DCIP can be valuable for site characterization and time‐lapse monitoring performance at DNAPL‐impacted sites. Key Points: Development of a new coupled model that simulates dense non‐aqueous phase liquids (DNAPL) release and remediation and its mapping by direct current resistivity and induced polarization (DCIP)Analysis of the DCIP response to key DNAPL and soil matrix properties at a single location and field‐scale DCIP imaging of DNAPL remediationCombined DCIP provides improved characterization and monitoring of DNAPL source zones compared to standalone DC resistivity
- Subjects
INDUCED polarization; DENSE nonaqueous phase liquids; MULTIPHASE flow
- Publication
Water Resources Research, 2021, Vol 57, Issue 11, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2021WR031366