Monitoring well utility in a heterogeneous DNAPL source zone area: Insights from proximal multilevel sampler wells and sampling capture-zone modelling

Abstract

This version is available at https://strathprints.strath.ac.uk/63641/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. ABSTRACTGroundwater-quality assessment at contaminated sites often involves the use of short-screen (1.5 to 3 m) monitoring wells. However, even over these intervals considerable variation may occur in contaminant concentrations in groundwater adjacent to the well screen. This is especially true in heterogeneous dense nonaqueous phase liquid (DNAPL) source zones, where cm-scale contamination variability may call into question the effectiveness of monitoring wells to deliver representative data. The utility of monitoring wells in such settings is evaluated by reference to high-resolution multilevel sampler (MLS) wells located proximally to shortscreen wells, together with sampling capture-zone modelling to explore controls upon well sample provenance and sensitivity to monitoring protocols. Field data are analysed from the highly instrumented SABRE research site that contained an old trichloroethene source zone within a shallow alluvial aquifer at a UK industrial facility. With increased purging, monitoring-well samples tend to a flow-weighted average concentration but may exhibit sensitivity to the implemented protocol and degree of purging. Formation heterogeneity adjacent to the wellscreen particularly, alongside pump-intake position and water level, influence this sensitivity. Purging of low volumes is vulnerable to poor reproducibility arising from concentration variability predicted over the initial 1 to 2 screen volumes purged. Marked heterogeneity may also result in limited long-term sample concentration stabilization. Development of bespoke monitoring protocols, that consider screen volumes purged, alongside water-quality indicator parameter stabilization, is recommended to validate and reduce uncertainty when interpreting monitoring-well data within source zone areas. Generalised recommendations on monit...

Numerical Modeling and Data‐Worth Analysis for Characterizing the Architecture and Dissolution Rates of a Multicomponent DNAPL Source

“…Conversely, situations where available MD data is uncertain with respect to source depletion trends, upscaled, dual‐domain models with explicit mass transfer parameters constrained by direct site characterization, provide a viable alternative to estimate source zone depletion behavior (Stewart et al., 2022). Furthermore, sites where natural attenuation mechanisms are significant may benefit from several monitoring transects along the flow direction, differentiating attenuation capacity from NAPL dissolution rates for decision‐support modeling (McMillan et al., 2018; Rivett et al., 2014).…”

“…Numerical models with parsimoniously parameterized source zones have proved useful for characterizing NAPL architecture and/or lumped‐process mass transfer coefficients (Marble et al., 2008; Mobile et al., 2012; Saenton & Illangasekare, 2004). Moreover, combining multilevel monitoring with recovery rates of contaminant mass (or with conventional monitoring wells) can be valuable for characterizing heterogeneous NAPL architectures, as spatially varying contaminant fluxes may be mapped to soil horizons harboring NAPL mass within a source zone (McMillan et al., 2018). Several studies have incorporated Gilland‐Sherwood or upscaled mass transfer functions in discretized NAPL zones or in dual‐domain models to estimate grid‐scale parameters from multilevel monitoring data and/or mass discharge/flux measurements (Christ et al., 2006; Falta, 2003; Frind et al., 1999; Guo et al., 2020; Mobile et al., 2012; Park & Parker, 2005; Saenton & Illangasekare, 2004).…”

Independent Review of Groundwater Remediation Strategy for Hexavalent Chromium and RDX Groundwater Plumes at Los Alamos National Laboratory (Rev. 1)

“…Description: A new or existing well is needed that is screened over a long interval(s) in the regional a Passive multi-level sampling surveys have been previously shown to be effective for measuring depthdiscrete geochemical and microbial patterns (Baldwin et al, 2008, Lasagna et al, 2016, McMillan et al, 2018. A detailed description of the multilevel sampler (MLS) is described in Baldwin and others (2008).…”

The Effects of Spill Pressure on the Migration and Remediation of Dense Non-Aqueous Phase Liquids in Homogeneous and Heterogeneous Aquifers

“…These petrochemical developments have provided more convenience for human beings and are a continually motivating force for our societal economy. However, these factories and facilities have become great potential sources of groundwater contamination and have caused serious damage to the subsurface environment [6,7,11,[13][14][15][16][17][18][19][20]. When dense non-aqueous liquids (DNAPLs) are released into aquifers, groundwater resources are seriously contaminated [21,22].…”