A PCE groundwater plume discharging to a river: influence of the streambed and near-river zone on contaminant distributions

Conant, Brewster; Cherry, John A.; Gillham, Robert W.

doi:10.1016/j.jconhyd.2004.04.001

Cited by 192 publications

(194 citation statements)

References 32 publications

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“…The plume has been delineated in detail all the way from the front of the dry cleaning building to the river (Conant, 2004;Conant et al, submitted for publication; Guilbeault et al, in press). This delineation was accomplished using transects of depth-discrete multilevel samplers and/or the Waterloo groundwater profiler, as described by Pitkin et al (1999).…”

Section: Angus Sitementioning

confidence: 99%

Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers

Hunkeler

Chollet

Pittet

et al. 2004

Journal of Contaminant Hydrology

109

119

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Chlorinated ethenes often migrate over extended distances in aquifers and may originate from different sources. The aim of this study was to determine whether stable carbon isotope ratios remain constant during dissolution and transport of chlorinated ethenes and whether the ratios can be used to link plumes to their sources. Detailed depth-discrete delineation of the carbon isotope ratio in a tetrachloroethene (PCE) plume and in a trichloroethene (TCE) plume was done along cross-sections orthogonal to groundwater flow in two sandy aquifers in the Province of Ontario, Canada. At the TCE site, TCE concentrations up to solubility were measured in one high concentration zone close to the bottom of the aquifer from where dense non-aqueous phase liquid (DNAPL) was collected. A laboratory experiment using the DNAPL indicated that only very small carbon isotope fractionation occurs during dissolution of TCE (0.26x), which is consistent with field observations. At most sampling points, the y 13 C of dissolved TCE was similar to that of the DNAPL except for a few sampling points at the bottom of the aquifer close to the underlying aquitard. At these points, a 13 C enrichment of up to 2.4x was observed, which was likely due to biodegradation and possibly preferential diffusion of TCE with 12 C into the aquitard. In contrast to the TCE site, several distinct zones of high concentration were observed at the PCE site and from zones to zone, the y 13 C values varied substantially from À 24.3x to À 33.6x. Comparison of the y 13 C values in the high concentration zones made it possible to divide the plume in the three different domains, each probably representing a different episode and location of DNAPL release. The three different zones could still be distinguished 220 m from the DNAPL sources. This demonstrates that carbon isotope ratios can be used to differentiate between different zones in chlorinated ethene plumes and to link plume zones to their sources. In addition, subtle variations in y 13 C at plume fringes provided insight into mechanisms of plume spreading in transverse vertical direction. These variations were identified because of the high-resolution provided by the monitoring network.

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Section: Angus Sitementioning

confidence: 99%

Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers

Hunkeler

Chollet

Pittet

et al. 2004

Journal of Contaminant Hydrology

109

119

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“…Plumes may also be lengthy due to their modest natural attenuation in many aquifer environments (McGuire et al, 2004). As such, dissolvedphase CHC plumes may hold significant potential to discharge to surface waters where they may pose risks to ecosystems and human receptors (Conant et al, 2004;McGuire et al, 2004;McKnight et al, 2010;Moran et al, 2007;Weatherill et al, 2014). Our focus is upon the final opportunity for natural attenuation of discharging CHC groundwater contaminants at the groundwater -surface water interface (GSI) and hyporheic zone therein.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach

Freitas

Rivett

Roche

et al. 2015

Science of The Total Environment

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This version is available at https://strathprints.strath.ac.uk/62331/ 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 AbstractThe typically elevated natural attenuation capacity of riverbed -hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed -hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool -riffle -glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter is anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition and absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed -hyporheic zone CHC dechlorination may provide only a partial, patchy barrier to CHC groundwater plume discharges to a surface water receptor; and, monitoring requirements to assess the variability in CHC attenuation within a reach are expected to be onerous. Further research on transient hyporheic zone dechlorination is...

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“…The discharge of contaminated groundwater into streams may impact surface water quality, with contaminant loads originating from contaminated sites e.g., chlorinated solvents and other xenobiotic organic compounds (Conant et al 2004;Westbrook et al 2005;Chapman et al 2007) , old landfill sites (Milosevic et al 2012) or agricultural application of pesticides (McKnight et al 2012). Due to the implementation of the European Water Framework Directive (WFD) and the increasing exploitation of stream water and groundwater, an increasing effort is made to understand the linkage between these two systems and assesses the effect of groundwater contaminants on surface water ecosystems and chemical quality (Hancock 2002;McKnight et al 2010;Schmidt et al 2010;McKnight et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Field experimental studies have attempted to identify the surface water -groundwater interaction zones, quantify the inflow (Westbrook et al 2005;Milosevic et al 2012), and study the processes in the sediment bed during groundwater seepage (e.g., Conant et al 2004;Bianchin et al 2006;Chapman et al 2007;Ellis and Rivett 2007;McKnight et al 2010;Milosevic et al 2012). In field studies the contaminant discharged from a groundwater plume was rarely detected in the stream due to rapid dilution by clean stream water and there is little published work on the resultant concentration distribution along the stream.…”

Section: Introductionmentioning

confidence: 99%

Dilution and volatilization of groundwater contaminant discharges in streams

Aisopou¹,

Bjerg²,

Sonne³

et al. 2015

Journal of Contaminant Hydrology

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An analytical solution to describe dilution and volatilisation of a continuous groundwater contaminant plume into streams is developed for risk assessment. The location of groundwater plume discharge into the stream (discharge through the side versus bottom of the stream) and different distributions of the contaminant plume concentration (Gaussian, homogeneous or heterogeneous distribution) are considered. The model considering the plume discharged through the bank of the river, with a uniform concentration distribution was the most appropriate for risk assessment due to its simplicity and limited data requirements. The dilution and volatilisation model is able to predict the entire concentration field, and thus the mixing zone, maximum concentration and fully mixed concentration in the stream. It can also be used to identify groundwater discharge The dilution model can also provide recommendations for sampling locations and the size of impact zones in streams. This is of interest for regulators, for example when developing guidelines for the implementation of the European Water Framework Directive.3

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A PCE groundwater plume discharging to a river: influence of the streambed and near-river zone on contaminant distributions

Cited by 192 publications

References 32 publications

Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers

Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers

Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach

Dilution and volatilization of groundwater contaminant discharges in streams

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