title: Processes controlling the fate of chloroethenes emanating from DNAPL aged sources in river-aquifer contexts.
abstract: This work dealt with the physical and biogeochemical processes that favored the natural attenuation of chloroethene plumes of aged sources located close to influent rivers in the presence of co-contaminants, such as nitrate and sulfate. Two working hypotheses were proposed: i) Reductive dechlorination is increased in areas where the river-aquifer relationship results in the groundwater dilution of electron acceptors, the reduction potential of which exceeds that of specific chloroethenes; ii) zones where silts predominate or where textural changes occur are zones in which biodegradation preferentially takes place. A field site on a Quaternary alluvial aquifer at Torelló, Catalonia (Spain) was selected to validate these hypotheses. This aquifer is adjacent to an influent river, and its redox conditions favor reductive dechlorination. The main findings showed that the low concentrations of nitrate and sulfate due to dilution caused by the input of surface water diminish the competition for electrons between microorganisms that reduce co-contaminants and chloroethenes. Under these conditions, the most bioavailable electron acceptors were PCE and metabolites, which meant that their biodegradation was favored. This led to the possibility of devising remediation strategies based on bioenhancing natural attenuation. The artificial recharge with water that is low in nitrates and sulfates may favor dechlorinating microorganisms if the redox conditions in the mixing water are sufficiently maintained as reducing and if there are nutrients, electron donors and carbon sources necessary for these microorganisms.
authors.affiliation: Dept. de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/Martí i Franquès, s/n, E-08028 Barcelona, Spain. Electronic address: puigserverdiana@ub.edu.
authors.forename: Diana
authors.initials: D
authors.lastname: Puigserver
authors.affiliation: Dept. de Productes Naturals, Biologia Vegetal i Edafologia, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII, s/n, E-08028 Barcelona, Spain. Electronic address: acortes@ub.edu.
authors.forename: Amparo
authors.initials: A
authors.lastname: Cortés
authors.affiliation: Dept. de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/Martí i Franquès, s/n, E-08028 Barcelona, Spain. Electronic address: mviladevall@ub.edu.
authors.forename: Manuel
authors.initials: M
authors.lastname: Viladevall
authors.affiliation: Dept. de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/Martí i Franquès, s/n, E-08028 Barcelona, Spain. Electronic address: xenianogueras@ub.edu.
authors.forename: Xènia
authors.initials: X
authors.lastname: Nogueras
authors.affiliation: School of Engineering, University of Guelph, NIG 2W1 Guelph, ON, Canada. Electronic address: bparker@uoguelph.ca.
authors.forename: Beth L
authors.initials: BL
authors.lastname: Parker
authors.affiliation: Dept. de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/Martí i Franquès, s/n, E-08028 Barcelona, Spain. Electronic address: jmcarmona@ub.edu.
authors.forename: José M
authors.initials: JM
authors.lastname: Carmona
mesh_terms: D001673:Biodegradation, Environmental; D002713:Chlorine / Q000378:metabolism*; D060587:Groundwater / Q000032:analysis / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D013030:Spain; D013750:Tetrachloroethylene / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D012987:Soil; D014874:Water Pollutants, Chemical; D002713:Chlorine; D013750:Tetrachloroethylene
keywords: Denitrification; Ecotone; Immobile residual DNAPL; PCE isotopic enrichment; Reductive dechlorination; Sulfate reduction