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Torrento Aguerri, Clara

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Torrento Aguerri, Clara
Affiliation principale
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/30665

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  • Publication
    Accès libre
    Dual element (C-Cl) isotope approach to distinguish abiotic reactions of chlorinated methanes by Fe(0) and by Fe(II) on iron minerals at neutral and alkaline pH
    (2018-5)
    Rodriguez-Fernandez, Diana
    ;
    Heckel, Benjamin
    ;
    Torrento Aguerri, Clara 
    ;
    Meyer, Armin
    ;
    Elsener, Martin
    ;
    Hunkeler, Daniel 
    ;
    Soler, Albert
    ;
    Rosell, Monica
    ;
    Domenèch, Christina
    A dual element C-Cl isotopic study was performed for assessing chlorinated methanes (CMs) abiotic transformation reactions mediated by iron minerals and Fe(0) to further distinguish them in natural attenuation monitoring or when applying remediation strategies in polluted sites. Isotope fractionation was investigated during carbon tetrachloride (CT) and chloroform (CF) degradation in anoxic batch experiments with Fe(0), with FeCl2(aq), and with Fe-bearing minerals (magnetite, Mag and pyrite, Py) amended with FeCl2(aq), at two different pH values (7 and 12) representative of field and remediation conditions. At pH 7, only CT batches with Fe(0) and Py underwent degradation and CF accumulation evidenced hydrogenolysis. With Py, thiolytic reduction was revealed by CS2 yield and is a likely reason for different Λ value (Δδ13C/Δδ37Cl) comparing with Fe(0) experiments at pH 7 (2.9±0.5 and 6.1±0.5, respectively). At pH 12, all CT experiments showed degradation to CF, again with significant differences in Λ values between Fe(0) (5.8±0.4) and Fe-bearing minerals (Mag, 2±1, and Py, 3.7±0.9), probably evidencing other parallel pathways (hydrolytic and thiolytic reduction). Variation of pH did not significantly affect the Λ values of CT degradation by Fe(0) nor Py. CF degradation by Fe(0) at pH 12 showed a Λ (8±1) similar to that reported at pH 7 (8±2), suggesting CF hydrogenolysis as the main reaction and that CF alkaline hydrolysis (13.0±0.8) was negligible. Our data establish a base for discerning the predominant or combined pathways of CMs natural attenuation or for assessing the effectiveness of remediation strategies using recycled minerals or Fe(0). keywords (6 words): CSIA, carbon tetrachloride, chloroform, pyrite, Fe(0), degradation pathways
  • Publication
    Accès libre
    Vitamin B12 effects on chlorinated methanes-degrading microcosms: Dual isotope and metabolically active microbial populations assessment
    (2017-10)
    Rodriguez-Fernandez, Diana
    ;
    Torrento Aguerri, Clara 
    ;
    Guivernau, Miriam
    ;
    Vinas, Marc
    ;
    Hunkeler, Daniel 
    ;
    Soler, Albert
    ;
    Domenèch, Christina
    ;
    Rosell, Mònica
    Field-derived anoxic microcosms were used to characterize chloroform (CF) and carbon tetrachloride (CT) natural attenuation to compare it with biostimulation scenarios in which vitamin B12 was added (B12/pollutant ratio of 0.01 and 0.1) by means of by-products, carbon and chlorine compound-specific stable-isotope analysis, and the active microbial community through 16S rRNA MiSeq high-throughput sequencing. Autoclaved slurry controls discarded abiotic degradation processes. B12 catalyzed CF and CT biodegradation without the accumulation of dichloromethane, carbon disulphide, or CF. The carbon isotopic fractionation value of CF (ƐCCF) with B12 was −14 ± 4‰, and the value for chlorine (ƐClCF) was −2.4 ± 0.4‰. The carbon isotopic fractionation values of CT (ƐCCT) were−16±6 with B12, and−13±2‰without B12; and the chlorine isotopic fractionation values of CT (ƐClCT)were−6±3and−4±2‰, respectively. Acidovorax, Ancylobacter, andPseudomonaswere themost metabolically active genera,whereas Dehalobacter and Desulfitobacteriumwere below0.1% of relative abundance. The dual C-Cl element isotope slope (Λ = Δδ13C/Δδ37Cl) for CF biodegradation (only detected with B12, 7 ± 1) was similar to that reported for CF reduction by Fe(0) (8 ± 2). Several reductive pathways might be competing in the tested CT scenarios, as evidenced by the lack of CF accumulation when B12 was added, which might be linked to a major activity of Pseudomonas stutzeri; by different chlorine apparent kinetic isotope effect values and Λ which was statistically different with and without B12 (5 ± 1 vs 6.1 ± 0.5), respectively. Thus, positive B12 effects such as CT and CF degradation catalyst were quantified for the first time in isotopic terms, and confirmedwith themajor activity of species potentially capable of their degradation.Moreover, the indirect benefits
  • Publication
    Accès libre
    Carbon and Chlorine Isotope Fractionation Patterns Associated with
    (2017-5)
    Torrento Aguerri, Clara 
    ;
    Rodriguez-Fernandez, Diana
    ;
    Heckel, Benjamin
    ;
    Meyer, Armin
    ;
    Domenèch, Christina
    ;
    Rosell, Monica
    ;
    Soler, Albert
    ;
    Elsener, Martin
    ;
    Hunkeler, Daniel 
    To use compound-specific isotope analysis for confidently assessing organic contaminant attenuation in the environment, isotope fractionation patterns associated with different transformation mechanisms must first be explored in laboratory experiments. To deliver this information for the common groundwater contaminant chloroform (CF), this study investigated for the first time both carbon and chlorine isotope fractionation for three different engineered reactions: oxidative C−H bond cleavage using heat-activated persulfate, transformation under alkaline conditions (pH ∼ 12) and reductive C− Cl bond cleavage by cast zerovalent iron, Fe(0). Carbon and chlorine isotope fractionation values were −8 ± 1‰ and −0.44 ± 0.06‰ for oxidation, −57 ± 5‰ and −4.4 ± 0.4‰ for alkaline hydrolysis (pH 11.84 ± 0.03), and −33 ± 11‰ and −3 ± 1‰ for dechlorination, respectively. Carbon and chlorine apparent kinetic isotope effects (AKIEs) were in general agreement with expected mechanisms (C−H bond cleavage in oxidation by persulfate, C−Cl bond cleavage in Fe(0)-mediated reductive dechlorination and E1CB elimination mechanism during alkaline hydrolysis) where a secondary AKIECl (1.00045 ± 0.00004) was observed for oxidation. The different dual carbon-chlorine (Δδ13C vs Δδ37Cl) isotope patterns for oxidation by thermally activated persulfate and alkaline hydrolysis (17 ± 2 and 13.0 ± 0.8, respectively) vs reductive
  • Publication
    Accès libre
    Compound-Specific Chlorine Isotope Analysis of Tetrachloromethane and Trichloromethane by Gas Chromatography-Isotope Ratio Mass Spectrometry vs Gas Chromatography-Quadrupole Mass Spectrometry: Method Development and Evaluation of Precision and Trueness
    (2017-3)
    Heckel, Benjamin
    ;
    Rodriguez-Fernandez, Diana
    ;
    Torrento Aguerri, Clara 
    ;
    Meyer, Armin
    ;
    Domenèch, Christina
    ;
    Rosell, Mònica
    ;
    Soler, Albert
    ;
    Hunkeler, Daniel 
    ;
    Elsener, Martin
    Compound-specific chlorine isotope analysis of tetrachloromethane (CCl4) and trichloromethane (CHCl3) was explored by both, gas chromatography-isotope ratio mass spectrometry (GC-IRMS) and GC-quadrupole MS (GC-qMS), where GC-qMS was validated in an interlaboratory comparison between Munich and Neuchâtel with the same type of commercial GC-qMS instrument. GC-IRMS measurements analyzed CCl isotopologue ions, whereas GC-qMS analyzed the isotopologue ions CCl3, CCl2, CCl (of CCl4) and CHCl3, CHCl2, CHCl (of CHCl3), respectively. Lowest amount dependence (good linearity) was obtained (i) in H-containing fragment ions where interference of 35Cl- to 37Cl-containing ions was avoided; (ii) with tuning parameters favoring one predominant rather than multiple fragment ions in the mass spectra. Optimized GC-qMS parameters (dwell time 70 ms, 2 most abundant ions) resulted in standard deviations of 0.2‰ (CHCl3) and 0.4‰ (CCl4), which are only about twice as large as 0.1‰ and 0.2‰ for GC-IRMS. To compare also the trueness of both methods and laboratories, samples from CCl4 and CHCl3 degradation experiments were analyzed and calibrated against isotopically different reference standards for both CCl4 and CHCl3 (two of each). Excellent agreement confirms that true results can be obtained by both methods provided that a consistent set of isotopically characterized reference materials is used.