Reductive dechlorination in recalcitrant sources of chloroethenes in the transition zone between aquifers and aquitards.
In the transition zone between aquifers and basal aquitards, the perchloroethene pools at an early time in their evolution are more recalcitrant than those elsewhere in the aquifer. The aim of this study is to demonstrate that the biodegradation of chloroethenes from aged pools (i.e., pools after decades of continuous groundwater flushing and dissolution) of perchloroethene is favored in the transition zone. A field site was selected where an aged pool exists at the bottom of a transition zone. Two boreholes were drilled to obtain sediment and groundwater samples to perform chemical, isotopic, molecular, and clone library analyses and microcosm experiments. The main results were as follows: (i) the transition zone is characterized by a high microbial richness; (ii) reductively dechlorinating microorganisms are present and partial reductive dechlorination coexists with denitrification, Fe and Mn reduction, and sulfate reduction; (iii) reductively dechlorinating microorganisms were also present in the zone of the aged pool; (v) the high concentrations of perchloroethene in this zone resulted in a decrease in microbial richness; (vi) however, the presence of fermenting microorganisms supplying electrons for the reductively dechlorinating microorganisms prevented the reductive dechlorination to be inhibited. These findings suggest that biostimulation and/or bioaugmentation could be applied to promote complete reductive dechlorination and to enhance the dissolution of more nonaqueous phase liquids (DNAPL).
Department de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
Diana
D
Puigserver
Department de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
Jofre
J
Herrero
Department de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
Mònica
M
Torres
Departament de Productes Naturals, Biologia Vegetal i Edafologia, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII, s/n., 08028, Barcelona, Spain.
Amparo
A
Cortés
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstrasse 15., 04318, Leipzig, Germany.
Ivonne
I
Nijenhuis
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstrasse 15., 04318, Leipzig, Germany.
Kevin
K
Kuntze
School of Engineering, University of Guelph, 50, Stone Road East, Guelph, ON, N1G 2W1, Canada.
Beth L
BL
Parker
Department de Gequímica, Petrologia i Prospecció Geològica, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain. jmcarmona@ub.edu.
José M
JM
Carmona
D001673:Biodegradation, Environmental; D060587:Groundwater / Q000032:analysis / Q000382:microbiology*; D054879:Halogenation; D007501:Iron / Q000378:metabolism; D008345:Manganese / Q000378:metabolism; D010084:Oxidation-Reduction; D013431:Sulfates / Q000378:metabolism; D013750:Tetrachloroethylene / Q000032:analysis / Q000378:metabolism*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
D013431:Sulfates; D014874:Water Pollutants, Chemical; D008345:Manganese; D007501:Iron; D013750:Tetrachloroethylene
Aged PCE pool; Biodegradation halo; Biotic reductive dechlorination; Genus Dehalococcoides; Richness of microbial communities; Transition zone to a basal aquitard