Subsoil heterogeneities controlling porewater contaminant mass and microbial diversity at a site with a complex pollution history

Abstract

Abstract

Degradation of chloroethenes in the transition zone between aquifers and aquitards

“…1(a), label 1a 4 ) and constituted a biodegradation halo (halo 2), which is similar to another halo in the USZ (halo 1; Fig. 1(a), (b)), indicating the biotic RD of PCE and metabolites, as described by Puigserver et al [3]. In addition, the PCE groundwater at port 7 of the multilevel well F1UB (located at the zone of halo 2) showed isotopic fractionation, with a δ 13 C value of -23.53 ± 0.07‰.…”

“…A core-sampler was used to recover the core. The drilling operations and the core-sampler are described by Puigserver et al [3]. The boreholes were equipped as multilevel wells (multi-level CMT-type 7 channels, Solinst) following the protocol established by Einarson and Cherry [8].…”

“…The core sampling is necessary to study the biogeochemical conditions under which the biodegradation processes occur in the subsurface [2] and to analyze the depth variation of contaminants that result from degradation processes expressed as biodegradation haloes of parent and metabolite compounds in the depth profile of concentrations. According to the observations of Puigserver et al [3], a biodegradation halo is a depth interval in the profile of concentrations where a gradual increase in a metabolite (e.g., TCE) reaches a maximum and then progressively decreases which results in a steep concentration gradient of this compound. An opposite variation of the parental compound (e.g., PCE), is produced parallel to the evolution of this metabolite.…”

Unravelling long-term source removal effects and chlorinated methanes natural attenuation processes by C and Cl stable isotopic patterns at a complex field site

“…Monitored Natural Attenuation (MNA) is an alternative cost-effective treatment, although it requires appropriate quantification and evaluation over time (Wiegert et al, 2012). There are only few MNA case studies of CT and CF in polluted sites, mainly based on the detection and quantification of by-products (Devlin and Muller, 1999;Davis et al, 2003;Puigserver et al, 2013). However, monitoring parental and by-product compounds concentration as an indicator of (bio)degradation has some limitations, such as i) long periods of time are often necessary to detect a significant decrease in concentrations, especially at highly polluted sites or when sources have not been removed; ii) no clear conclusions can be drawn when a given compound appears as both parent and by-product; when a by-product originates from multiple parent compounds; or when the target by-product is further degraded and iii) sorption or desorption, differential transport or dilution events could also produce concentrations variations but not degradation.…”

Natural attenuation model and biodegradation for 1,1,1-trichloroethane contaminant in shallow groundwater

“…Chlorinated aliphatic hydrocarbons are often present in the form of dense non-aqueous phase liquids (DNAPLs) in subsurface environments ( Puigserver et al, 2013 ). Migration of these contaminants in the groundwater is affected by dissolution of the pollutants within the source zone, mass transfer to the groundwater, advection, dispersion, diffusion, sorption (retardation), and biodegradation ( Schirmer and Butler, 2004 ).…”