Characterization of DNAPL source zones in clay-sand media via joint inversion of DC resistivity, induced polarization and borehole data

Xueyuan Kang; Christopher Power; Amalia Kokkinaki; André Revil; Jichun Wu; Xiaoqing Shi; Yaping Deng

doi:10.1016/j.jconhyd.2023.104240

Characterization of DNAPL source zones in clay-sand media via joint inversion of DC resistivity, induced polarization and borehole data

J Contam Hydrol. 2023 Sep:258:104240. doi: 10.1016/j.jconhyd.2023.104240. Epub 2023 Sep 1.

Authors

Xueyuan Kang¹, Christopher Power², Amalia Kokkinaki³, André Revil⁴, Jichun Wu⁵, Xiaoqing Shi⁶, Yaping Deng⁷

Affiliations

¹ Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
² Department of Civil and Environmental Engineering, Western University, London, Ontario N6A 5B9, Canada.
³ Department of Environmental Science, University of San Francisco, San Francisco, CA 94117, USA.
⁴ Univ. Grenoble Alpes, Univ. Savoie Mont-Blanc, CNRS, UMR CNRS 5204, EDYTEM, 73370 Le Bourget du Lac, France.
⁵ Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China. Electronic address: jcwu@nju.edu.cn.
⁶ Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China. Electronic address: shixq@nju.edu.cn.
⁷ School of Natural Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China.

PMID: 37683375
DOI: 10.1016/j.jconhyd.2023.104240

Abstract

Toxic organic contaminants in groundwater are pervasive at many industrial sites worldwide. These contaminants, such as chlorinated solvents, often appear as dense non-aqueous phase liquids (DNAPLs). To design efficient remediation strategies, detailed characterization of DNAPL Source Zone Architecture (SZA) is required. Since invasive borehole-based investigations suffer from limited spatial coverage, a non-intrusive geophysical method, direct current (DC) resistivity, has been applied to image the DNAPL distribution; however, in clay-sand environments, the ability of DC resistivity for DNAPLs imaging is limited since it cannot separate between DNAPLs and surrounding clay-sand soils. Moreover, the simplified parameterization of conventional inversion approaches cannot preserve physically realistic patterns of SZAs, and tends to smooth out any sharp spatial variations. In this paper, the induced polarization (IP) technique is combined with DC resistivity (DCIP) to provide plausible DNAPL characterization in clay-sand environments. Using petrophysical models, the DCIP data is utilized to provide tomograms of the DNAPL saturation (S_N) and hydraulic conductivity (K). The DCIP-estimated K/S_N tomograms are then integrated with borehole measurements in a deep learning-based joint inversion framework to accurately parameterize the highly irregular SZA and provide a refined DNAPL image. To evaluate the performance of the proposed approach, we conducted numerical experiments in a heterogeneous clay-sand aquifer with a complex SZA. Results demonstrate the standalone DC resistivity method fails to infer the DNAPL in complex clay-sand environments. In contrast, the combined DCIP technique provides the necessary information to reconstruct the large-scale features of K/S_N fields, while integrating DCIP data with sparse but accurate borehole data results in a high resolution characterization of the SZA.

Keywords: Clay-sand environments; DNAPL source zone characterization; Hydrogeophysics; Induced polarization; Joint inversion.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Clay
Groundwater*
Sand
Water Pollutants, Chemical* / analysis

Substances

Sand
Clay
Water Pollutants, Chemical