Revealing chlorinated ethene transformation hotspots in a nitrate-impacted hyporheic zone

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dc.contributor.authorWeatherill, John J.
dc.contributor.authorKrause, Stefan
dc.contributor.authorUllah, Sami
dc.contributor.authorCassidy, Nigel J.
dc.contributor.authorLevy, Amir
dc.contributor.authorDrijfhout, Falko P.
dc.contributor.authorRivett, Michael O.
dc.contributor.funderEnvironment Agency
dc.contributor.funderKeele University
dc.date.accessioned2024-02-09T12:10:28Z
dc.date.available2024-02-09T12:10:28Z
dc.date.issued2019
dc.description.abstractHyporheic zones are increasingly thought of as natural bioreactors, capable of transforming and attenuating groundwater pollutants present in diffuse baseflow. An underappreciated scenario in the understanding of contaminant fate in hyporheic zones is the interaction between point-source trichloroethene (TCE) plumes and ubiquitous, non-point source pollutants such as nitrate. This study aims to conceptualise critical biogeochemical gradients in the hyporheic zone which govern the export potential of these redox-sensitive pollutants from carbon-poor, oxic aquifers. Within the TCE plume discharge zone, discrete vertical profiling of the upper 100 cm of sediment pore water chemistry revealed an 80% increase in dissolved organic carbon (DOC) concentrations and 20ā€“60 cm thick hypoxic zones (<2 mg O2 Lāˆ’1) within which most reactive transport was observed. A 33% reduction of nitrate concentrations coincided with elevated pore water nitrous oxide concentrations as well as the appearance of manganese and the TCE metabolite cis-1,2-dichloroethene (cDCE). Elevated groundwater nitrate concentrations (>50 mg Lāˆ’1) create a large stoichiometric demand for bioavailable DOC in discharging groundwater. With the benefit of a high-resolution grid of pore water samplers investigating the shallowest 30 cm of hypoxic groundwater flow paths, we identified DOC-rich hotspots associated with submerged vegetation (Ranunculus spp.), where low-energy metabolic processes such as mineral dissolution/reduction, methanogenesis and ammonification dominate. Using a chlorine index metric, we show that enhanced TCE to cDCE transformation takes place within these biogeochemical hotspots, highlighting their relevance for natural plume attenuation.en
dc.description.statusPeer revieweden
dc.description.versionAccepted Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationWeatherill, J. J., Krause, S., Ullah, S., Cassidy, N. J., Levy, A., Drijfhout, F. P. and Rivett, M. O. (2019) 'Revealing chlorinated ethene transformation hotspots in a nitrate-impacted hyporheic zone', Water research, 161, pp.222-231. https://doi.org/10.1016/j.watres.2019.05.083en
dc.identifier.doihttps://doi.org/10.1016/j.watres.2019.05.083
dc.identifier.endpage231
dc.identifier.issn431354
dc.identifier.journaltitleWater Researchen
dc.identifier.startpage222
dc.identifier.urihttps://hdl.handle.net/10468/15540
dc.identifier.volume161
dc.language.isoenen
dc.publisherElsevier Ltden
dc.rightsĀ© 2019, Elsevier Ltd. All rights reserved. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/en
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subjectChlorinated ethenesen
dc.subjectDissolved organic carbonen
dc.subjectHyporheic zoneen
dc.subjectNatural attenuationen
dc.subjectNitrateen
dc.subjectTerminal electron-accepting processesen
dc.titleRevealing chlorinated ethene transformation hotspots in a nitrate-impacted hyporheic zoneen
dc.typeArticle (peer-reviewed)en
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