Weatherill, JJ and Atashgahi, S and Schneidewind, U and Krause, S and Ullah, S and Cassidy, NJ and Rivett, M (2017) Natural attenuation of chlorinated ethenes in hyporheic zones: a review of key biogeochemical processes and in-situ transformation potential. Water Research. ISSN 1879-2448

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Abstract

Chlorinated ethenes (CEs) are legacy contaminants whose chemical footprint is expected to persist in aquifers around the world for many decades to come. These organohalides have been reported in river systems with concerning prevalence and are thought to be significant chemical stressors in urban water ecosystems. The aquifer-river interface (known as the hyporheic zone) is a critical pathway for CE discharge to surface water bodies in groundwater baseflow. This pore water system may represent a natural bioreactor where anoxic and oxic biotransformation process act in synergy to reduce or even eliminate contaminant fluxes to surface water. Here, we critically review current process understanding of anaerobic CE respiration in the competitive framework of hyporheic zone biogeochemical cycling fuelled by in-situ fermentation of natural organic matter. We conceptualise anoxic-oxic interface development for metabolic and co-metabolic mineralisation by a range of aerobic bacteria with a focus on vinyl chloride degradation pathways. The superimposition of microbial metabolic processes occurring in sediment biofilms and bulk solute transport delivering reactants produces a scale dependence in contaminant transformation rates. Process interpretation is often confounded by the natural geological heterogeneity typical of most riverbed environments. We discuss insights from recent field experience of CE plumes discharging to surface water and present a range of practical monitoring technologies which address this inherent complexity at different spatial scales. Future research must address key dynamics which link supply of limiting reactants, residence times and microbial ecophysiology to better understand the natural attenuation capacity of hyporheic systems.

Item Type: Article
Uncontrolled Keywords: Chlorinated ethenes; hyporheic zone; natural attenuation; biogeochemistry; biotransformation; heterogeneity
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Depositing User: Hannah Reidy
Date Deposited: 31 Oct 2017 08:50
Last Modified: 31 Oct 2017 08:50
URI: http://eprints.keele.ac.uk/id/eprint/4149

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