Factors Determining the Attenuation of Chlorinated Aliphatic Hydrocarbons in Eutrophic River Sediment Impacted by Discharging Polluted Groundwater

Abstract

This study explored the potential of eutrophic river sediment to attenuate the infiltration of chlorinated aliphatic hydrocarbon (CAH)-polluted groundwater discharging into the Zenne River near Brussels, Belgium. Active CAH biodegradation by reductive dechlorination in the sediment was suggested by a high dechlorination activity in microcosms containing sediment samples and the detection of dechlorination products in sediment pore water. A unique hydrogeochemical evaluation, including a delta2H and delta18O stable isotope approach, allowed to determine the contribution of different abiotic and biotic CAH attenuation processes and to delineate their spatial distribution inthe riverbed. Reductive dechlorination of the CAHs seemed to be the most widespread attenuation process, followed by dilution by unpolluted groundwater discharge and by surface water mixing. Although CAHs were never detected in the surface water, 26-28% of the investigated locations in the riverbed did not show CAH attenuation. We conclude that the riverbed sediments can attenuate infiltrating CAHs to a certain extent, but will probably not completely prevent CAHs to discharge from the contaminated groundwater into the Zenne River.

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

“…Several processes influence CHC plume fate in the riverbed -hyporheic zone environment at the GSI (Bencala, 2000;Environment Agency, 2009). Although dilution due to surface-water mixing into discharging groundwater plumes within the hyporheic zone does not remove contaminant mass, it may reduce concentrations impacting surface waters (Conant et al, 2004;Hamonts et al, 2009). Sorption is often more significant than in the preceding aquifer as riverbed deposits are often rich in organic matter, leading to retarded transport and greater residence times (Smith and Lerner, 2008).…”

Characterization and assessment of contaminated soil and groundwater at an organic chemical plant site in Chongqing, Southwest China

“…The groundwater samples were placed into glass bottles and maintained under 4°C conditions for transportation to the laboratory. Samples of soil and groundwater were analyzed for VOCs and SVOCs according to the procedures and methods of the Standard of Soil Quality Assessment for Exhibition Sites (Ministry of Environmental Protection of the People's Republic of China 2007) using high-performance liquid chromatography and gas chromatography (Brasseur et al 2007;Hamonts et al 2009;Ma et al 2013). Heavy metal analyses were also conducted according to the standards for inductively coupled plasma atomic emission spectrometry (Aydin and Soylak 2010).…”

Ecophysiology and environmental distribution of organohalide-respiring bacteria

“…This could be due to the high hydraulic conductivity of 1-3 m/day at this site [222] facilitating a rapid dispersion and community succession [416]. Accordingly, the pre-biostimulation bacterial community in the stimulated wells was significantly different from the control well (Table S6.7) whereas the geochemical parameters were similar between the pre-biostimulation and control well samples and clustered closely in the PCA plot ( Figure S6.7).…”

“…Numerous studies reported anaerobic dechlorination of chlorinated ethenes in the groundwater surface water interaction zone from various geographical locations i.e. freshwater tidal wetlands of West Branch Canal Creek, Maryland, USA [219], Lake Michigan, USA [220], as well as streambed sediments in Angus, Ontario, Canada [221] and in Vilvoorde, Brussels, Belgium [222] without identification of responsible microorganisms. With growing interest on environmental distribution of OHRB, several 16S RNA gene-based methods were applied to track their presence in organohalide impacted or pristine sediments [48,90,186,223].…”

“…However, in spite of repeated detection of biomarkers associated with OHRB in the field, microcosm studies with Zenne riverbed sediments [224][225][226] and high OHR performance in microcosm studies with material from different locations at the Zenne river site [222,226], high spatial variability of OHR potential was observed in field measurements from the 39 2…”