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

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

Author Freitas, Juliana G. Autor UNIFESP Google Scholar
Rivett, Michael O. Google Scholar
Roche, Rachel S. Google Scholar
Durrant (Nee Cleverly), Megan Google Scholar
Walker, Caroline Google Scholar
Tellam, John H. Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Univ Birmingham
Abstract The 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 are anticipated to be a key control. the glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally 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, somewhat 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 recommended. (C) 2014 Elsevier B.V. All rights reserved.
Keywords Groundwater-surface water interaction
Trichloroethene (TCE)
Chlorinated hydrocarbon (CHC)
Natural attenuation
Hyporheic zone
Dechlorination
Language English
Sponsor Environment Agency
University of Birmingham
Date 2015-02-01
Published in Science of the Total Environment. Amsterdam: Elsevier B.V., v. 505, p. 236-252, 2015.
ISSN 0048-9697 (Sherpa/Romeo, impact factor)
Publisher Elsevier B.V.
Extent 236-252
Origin http://dx.doi.org/10.1016/j.scitotenv.2014.09.083
Access rights Closed access
Type Article
Web of Science ID WOS:000347654900023
URI http://repositorio.unifesp.br/handle/11600/38706

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