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- Title
Assessing Contaminant Mass Discharge Uncertainty With Application of Hydraulic Conductivities Derived From Geoelectrical Cross‐Borehole Induced Polarization and Other Methods.
- Authors
Thalund‐Hansen, Rasmus; Troldborg, Mads; Levy, Léa; Christiansen, Anders Vest; Bording, Thue S.; Bjerg, Poul L.
- Abstract
A new methodology was developed to support contaminant mass discharge (CMD)‐based risk assessment of groundwater contamination downgradient of point source zones. Geoelectrical cross‐borehole induced polarization (IP) data were collected at a site undergoing in situ remediation of chlorinated solvents for determining 2D hydraulic conductivity (K) distributions with an inversion model resolution of 0.15 m (vertically) x 0.50 m (horizontally) in three control planes from 10 to 20 m depth. Additionally, 18 slug tests and 31 grain size distribution analyses (GSA) from the control planes, were used for K‐estimation. The geometric means and variance of the IP, slug test, and GSA derived K‐estimates were consistent with previously studied sandy aquifers. Furthermore, the vertical variation in K between two geological settings, a sandy till and a meltwater sand formation, was clearly identified by the IP K‐estimates. The vertical variation was backed up by hydraulic profiling tool (HPT) measurements. Random realizations of CMD were simulated based on the cross‐borehole IP derived K‐values. For comparison, the CMD was also estimated with a geostatistical conditional simulation approach, using the data from slug tests and GSAs. The high IP resolution captured the small scale variations in K across the transects and led to CMD predictions with a narrow uncertainty interval, whereas slug test and GSA either under‐ or overestimated the magnitude of the areas with the highest CMD. Applying the geophysical cross‐borehole method for estimating K‐distributions in addition to traditional methods would improve CMD‐based risk assessment and evaluation of remediation performance at contaminated sites. Key Points: Cross‐borehole induced polarization (IP) data have successfully been used to infer a high resolution hydraulic conductivity fieldHydraulic conductivity estimates from cross‐borehole IP, slug test, grain size distribution and hydraulic profiling tool compared wellCompared to other hydraulic conductivity estimation methods, application of cross‐borehole IP data enables an improved estimation of contaminant mass discharge
- Subjects
HYDRAULIC conductivity; PARTICLE size distribution; INDUCED polarization; IN situ remediation; HAZARDOUS waste sites; MODEL airplanes
- Publication
Water Resources Research, 2023, Vol 59, Issue 8, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2022WR034360