The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here: https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Charlotte Sparrenbom

Charlotte Sparrenbom

Senior lecturer

Charlotte Sparrenbom

Combining spectral induced polarization with x-ray tomography to investigate the importance of DNAPL geometry in sand samples

Author

  • Sara Johansson
  • Matteo Rossi
  • Stephen Hall
  • Charlotte J. Sparrenbom
  • David Hagerberg
  • Erika Tudisco
  • Håkan Rosqvist
  • Torleif Dahlin

Summary, in English

Whilst many studies have been performed to investigate the spectral induced polarization (SIP) response of Non-aqueous Phase Liquid (NAPL) contaminated soil samples there are still many uncertainties in the interpretation of the data. A key issue is that altered pore space geometries due to the presence of a NAPL phase will change the measured IP spectra. However, without any information on the NAPL distribution in the pore space, assumptions are necessary for the SIP data interpretation. Therefore, experimental data of SIP signals directly associated with different NAPL distributions is needed. We use high-resolution x-ray tomography and 3D image processing to quantitatively assess NAPL distributions in samples of fine-grained sand containing different concentrations of tetrachloroethylene (PCE) and link this to SIP measurements on the same samples. The total concentration of the sample constituents as well as the volumes of the individual NAPL blobs were calculated and used for the interpretation of the associated SIP responses. The x-ray tomography and image analysis showed that the real sample properties (porosity and NAPL distributions) differed from the targeted ones. Both contaminated samples contained less NAPL than expected from the manual sample preparation. The SIP results showed higher real conductivity and lower imaginary conductivity in the contaminated samples compared to a clean sample. This is interpreted as an effect of increased surface conductivity along interconnected NAPL blobs and decreased surface areas in the samples due to NAPL blobs larger than and enclosing grains. We conclude that the combination of SIP, x-ray tomography and image analysis is a very promising approach to achieve a better understanding of the measured SIP responses of NAPL contaminated samples.

Department/s

  • Engineering Geology
  • Solid Mechanics
  • Quaternary Sciences
  • Geotechnical Engineering

Publishing year

2019-02-13

Language

English

Pages

173-188

Publication/Series

Geophysics

Volume

84

Issue

3

Document type

Journal article

Publisher

Soc Exploration Geophysicists

Topic

  • Geotechnical Engineering

Status

Published

Project

  • Geoelectrical Imaging for Site Investigation for Urban Underground Infrastructure

ISBN/ISSN/Other

  • ISSN: 0016-8033