Analysis of time-lapse data error in complex conductivity imaging to alleviate anthropogenic noise for site characterization

Flores Orozco, A. and Kemna, A. and Binley, A. and Cassiani, G. (2019) Analysis of time-lapse data error in complex conductivity imaging to alleviate anthropogenic noise for site characterization. Geophysics, 84 (2). B181-B193. ISSN 0016-8033

[img]
Preview
PDF (Flores Orozco et al(author accepted copy))
Flores_Orozco_et_al_author_accepted_copy_.pdf - Accepted Version
Available under License Unspecified.

Download (5MB)

Abstract

Previous studies have demonstrated the potential benefits of the complex conductivity (CC) imaging over electrical resistivity tomography for an improved delineation of hydrocarbonimpacted sites and accompanying biogeochemical processes. However, time-lapse CC field applications are still rare, in particular for measurements performed near anthropogenic structures such as buried pipes or tanks, which are typically present at contaminated sites. To fill this gap, we have developed CC imaging (CCI) results for monitoring data collected in Trecate (northwest Italy), a site impacted by a crude oil spill. Initial imaging results reveal only a poor correlation with seasonal variations of the groundwater table at the site (approximately 6 m). However, it is not clear to which extend such results are affected by anthropogenic structures present at the site. To address this, we performed a detailed analysis of the misfit between direct and reciprocal time-lapse differences. Based on this analysis, we were able to discriminate spatial and temporal sources of systematic errors, with the latter commonly affecting measurements collected near anthropogenic structures. Following our approach, CC images reveal that temporal changes in the electrical properties correlate well with seasonal fluctuations in the groundwater level for areas free of contaminants, whereas contaminated areas exhibit a constant response over time characterized by a relatively high electrical conductivity and a negligible polarization effect. In accordance with a recent mechanistic model, such a response can be explained by the presence of immiscible fluids (oil and air) forming a continuous film through the micro and macropores, hindering the development of ion-selective membranes and membrane polarization. Our results demonstrate the applicability of CCI for an improved characterization of hydrocarboncontaminated areas, even in areas affected by cultural noise.

Item Type: Journal Article
Journal or Publication Title: Geophysics
Additional Information: © 2019 Society of Exploration Geophysicists. Use is subject to SEG terms of use and conditions
Uncontrolled Keywords: /dk/atira/pure/subjectarea/asjc/1900/1908
Subjects:
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 132159
Deposited By: ep_importer_pure
Deposited On: 21 Mar 2019 13:25
Refereed?: Yes
Published?: Published
Last Modified: 26 Feb 2020 04:55
URI: https://eprints.lancs.ac.uk/id/eprint/132159

Actions (login required)

View Item View Item