1 BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved 2 contaminants ... more 1 BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved 2 contaminants in groundwater, ideal for rapid screening and teaching. This work extends the 3 BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three4 dimensional exact solution of the reactive transport from a patch source, accounting for 5 fractionation by first-order decay and/or sorption, is used. The results match those from a 6 previously published isotope model but are much simpler to obtain. Two different isotopes 7 may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a 8 rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, 9 deviations of isotope ratios at specific reactive positions with respect to “bulk” ratios in the 10 whole compound can be simulated. This model is named BIOSCREEN-AT-ISO and will be 11 downloadable from the journal homepage. 12 13 Article Impact Statement 14 This BIOSCREEN...
A peine a-t-on fait un sort aux composes de plomb dans l'essence, que les additifs maintenant... more A peine a-t-on fait un sort aux composes de plomb dans l'essence, que les additifs maintenant utilises pointent en tete de la production mondiale des produits chimiques. A-t-on chasse Satan par Belzebuth? L'additif MTBE, ou ether methyltertiobutylique, est de plus en plus utilise en Europe, malgre sa faible biodegradabilite, une connaissance imparfaite de sa toxicite et les mauvaises experiences faites aux Etats-Unis en ce qui concerne la pollution des nappes phreatiques. Dans les eaux souterraines suisses, le MTBE est maintenant la substance la plus detectee parmi les polluants provenant de l'industrie, mais ses concentrations restent (encore?) essentiellement en dessous des valeurs critiques.
This study aimed at investigating whether stable isotopes can be used to monitor the progress of ... more This study aimed at investigating whether stable isotopes can be used to monitor the progress of volatile organic compounds (VOCs) volatilization from contaminated sediment during venting. Batches of a dry aquifer sediment were packed into stainless steel HPLC columns, humidified with distilled water and later contaminated by either liquid toluene or propan-2-ol. The VOCs were then volatilized by a stream of gas at room temperature, and the concentrations and stable isotope ratios of gaseous VOCs were recorded by isotope-ratio mass spectrometry. During early stages of volatilization of toluene, the isotope ratios Δδ13C shifted to more negative values by about -3 to -5‰ and the Δδ2H by more than -40‰, while the concentration remained at or near initial saturated vapor concentration. Depletion of the isotope ratios in the gas was explained by the vapor-liquid fractionation process, which is amplified by successive self-partitioning steps of gaseous VOC into remaining liquid VOC. For propan-2-ol the carbon isotope shift was negative like for toluene, whereas the H shift was positive. Hydrogen bonding in the liquid propan-2-ol phase causes a normal vapor-liquid H isotope effect which was described already in classical literature. The isotope shifts in the present experiments are larger than previously reported shifts due to phase-change processes and reach the magnitude of shifts usually observed in kinetic isotope fractionation.
The journal of physical chemistry. B, Jun 15, 2017
The relationship between the strength of the intermolecular interaction in liquid and the positio... more The relationship between the strength of the intermolecular interaction in liquid and the position-specific 13C fractionation observed during distillation was investigated. A range of molecules showing different intermolecular interactions in terms of mode and intensity were incorporated in the study. Although it had previously been suggested that during evaporation the diffusive 13C isotope effect in the thin liquid layer interfaced with vapor is not position-specific, herein we show that this is not the case. In particular, the position-specific effect was demonstrated for a series of alcohols. Our hypothesis is that intermolecular interactions in the liquid phase are the source of position-specific 13C fractionation observed on the molecule. A clear trend is observed between the 13C isotope effect of the carbon bearing the heteroatom of chemical function and the relative permittivity, the solvent hydrogen-bond acidity and the solvent hydrogen-bond basicity, while only a weak tren...
Environmental pollution (Barking, Essex : 1987), Jan 26, 2015
Isotopic fractionation of pollutants in terrestrial or aqueous environments is a well-recognized ... more Isotopic fractionation of pollutants in terrestrial or aqueous environments is a well-recognized means by which to track different processes during remediation. As a complement to the common practice of measuring the change in isotope ratio for the whole molecule using isotope ratio monitoring by mass spectrometry (irm-MS), position-specific isotope analysis (PSIA) can provide further information that can be exploited to investigate source and remediation of soil and water pollutants. Position-specific fractionation originates from either degradative or partitioning processes. We show that isotope ratio monitoring by (13)C NMR (irm-(13)C NMR) spectrometry can be effectively applied to methyl tert-butylether, toluene, ethanol and trichloroethene to obtain this position-specific data for partitioning. It is found that each compound exhibits characteristic position-specific isotope fractionation patterns, and that these are modulated by the type of evaporative process occurring. Such d...
Soil acidification is an ongoing natural process which can be enhanced by human activities or can... more Soil acidification is an ongoing natural process which can be enhanced by human activities or can be controlled by appropriate soil management practices. Two highly acidified urban garden soils, CHA and NTO, were subjected to single-extraction procedure by water to determine the extractable concentrations of Ca, Mg, K, Na, Al, Cu, Fe, Mn, Pb, Zn and . A modeling of effects of liming on soil solution was carried out from initial pH to pH 8.0 using the PHREEQC-2 code coupled with the PHREEQC.dat thermodynamic database. In NTO soil solution, liming increased the concentration of all cations, exception of Al when in CHA soil solution concentration of Ca, Cu, Fe and Pb increased. The chemical speciation of cations was evaluated in the soil solution. Basic cations Ca, Mg, K and Na were found as free forms (Ca 2+ , Mg 2+ , K + , Na + ) and sometimes complexed by sulfate (,). The concentration of the toxic free ion Al 3+ decreased quickly and was replaced by less toxic hydroxide complexes. ...
BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved contaminants in g... more BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved contaminants in groundwater, ideal for rapid screening and teaching. This work extends the BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three-dimensional exact solution of the reactive transport from a patch source, accounting for fractionation by first-order decay and/or sorption, is used. The results match those from a previously published isotope model but are much simpler to obtain. Two different isotopes may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, deviations of isotope ratios at specific reactive positions with respect to "bulk" ratios in the whole compound can be simulated. This model is named BIOSCREEN-AT-ISO and will be downloadable from the journal homepage.
BIOCHLOR is a well-known simple tool for evaluating the transport of dissolved chlorinated solven... more BIOCHLOR is a well-known simple tool for evaluating the transport of dissolved chlorinated solvents in groundwater, ideal for rapid screening and teaching. This work extends the BIOCHLOR model for the calculation of stable isotope ratios of carbon and chlorine isotopes in chloroethenes. An exact solution for the three-dimensional reactive transport of a chain of degrading compounds including sorption is provided in a spreadsheet and applied for modeling the transport of individual isotopes (12)C, (13)C, (35)Cl, (37)Cl from a constant source. The model can consider secondary isotope effects that can occur in the breaking of CCl bonds. The model is correctly reproducing results for δ(13)C and δ(37)Cl modeled by a previously published 1-D numerical model without secondary isotope effects, and is also reproducing results from a microcosm experiment with secondary chlorine isotope effects. Two applications of the model using field data from literature are further given and discussed. The new BIOCHLOR-ISO model is distributed as a spreadsheet (MS EXCEL) along with this publication.
Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in whic... more Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in which tetrachloro- and trichloroethene sequentially degrade to dichloroethenes, vinyl chloride (VC) and ethene, or ethane under reducing conditions. For detoxification, degradation must go beyond VC. Assessments based on ethene and ethane, however, are difficult because these products are volatile, may stem from alternative sources, can be further transformed and are not always monitored. To alternatively quantify degradation beyond VC, stable carbon isotope mass balances have been proposed where concentration-weighted CE isotope ratios are summed up and compared to the original source isotope ratio. Reported assessments, however, have provided not satisfactorily quantified results entailing greatly differing upper and lower estimates. This work proposes an integrative approach to better constrain the extent of total chloroethene degradation in groundwater samples. It is based on fitting of ...
In forensic environmental investigations the main issue concerns the inference of the original so... more In forensic environmental investigations the main issue concerns the inference of the original source of the pollutant for determining the liable party. Isotope measurements in geochemistry, combined with complimentary techniques for contaminant identification, have contributed significantly to source determination at polluted sites. In this work we have determined the intramolecular (13)C profiles of several molecules well-known as pollutants. By giving additional analytical parameters, position-specific isotope analysis performed by isotope ratio monitoring by (13)C nuclear magnetic resonance (irm-(13)C NMR) spectrometry gives new information to help in answering the major question: what is the origin of the detected contaminant? We have shown that isotope profiling of the core of a molecule reveals both the raw materials and the process used in its manufacture. It also can reveal processes occurring between the contamination site 'source' and the sampling site. Thus, irm-(13)C NMR is shown to be a very good complement to compound-specific isotope analysis currently performed by mass spectrometry for assessing polluted sites involving substantial spills of pollutant.
Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nu... more Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nuclear magnetic resonance spectrometry during the evaporation of 10 liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation, distillation). The observed effects are used to assess the validity of the Craig-Gordon isotope model for organic liquids. For seven liquids the overall isotope effect (IE) includes a vapor-liquid contribution that is strongly position-specific in polar compounds but less so in apolar compounds and a diffusive IE that is not position-specific, except in the alcohols, ethanol and propan-1-ol. The diffusive IE is diminished under forced evaporation. The position-specific isotope pattern created by liquid-vapor IEs is manifest in five liquids, which have an air-side limitation for volatilization. For the alcohols, undefined processes in the liquid phase create additional PSIEs. Three other liquids with limitations on the liquid side have a lower, highly position-specific, bulk diffusive IE. It is concluded that evaporation of organic pollutants creates unique position-specific isotope patterns that may be used to assess the progress of remediation or natural attenuation of pollution and that the Craig-Gordon isotope model is valid for the volatilization of nonpolar organic liquids with air-side limitation of the volatilization rate.
Investigations were made on the potential for biotransformation of ten chlorofluorocarbons and hy... more Investigations were made on the potential for biotransformation of ten chlorofluorocarbons and hydrochlorofluorocarbons under methanogenic conditions. Transformations were monitored in batch experiments by analysis of the concentrations in the headspace. Trichlorofluoromethane (CFC-11) was transformed to dichlorofluoromethane (HCFC-21) and to chlorofluoromethane (HCFC-31). The methanogenesis inhibitor 2-bromoethanesulfonate (BES) significantly decreased the CFC-11 transformation rate. 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) was transformed to two products which were deduced to be 1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a) and chlorotrifluoroethene (CTFE). No transformation was detected for dichlorodifluoromethane (CFC-12), chlorodifluoromethane (HCFC-22), 1,2-dichloro-1,1,2,2-tetra-fluoroethane (CFC-114), chloropentafluoroethane (CFC-115), 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b) and 1,1,1,2-tetrafluoroethane (HFC-134a).
1 BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved 2 contaminants ... more 1 BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved 2 contaminants in groundwater, ideal for rapid screening and teaching. This work extends the 3 BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three4 dimensional exact solution of the reactive transport from a patch source, accounting for 5 fractionation by first-order decay and/or sorption, is used. The results match those from a 6 previously published isotope model but are much simpler to obtain. Two different isotopes 7 may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a 8 rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, 9 deviations of isotope ratios at specific reactive positions with respect to “bulk” ratios in the 10 whole compound can be simulated. This model is named BIOSCREEN-AT-ISO and will be 11 downloadable from the journal homepage. 12 13 Article Impact Statement 14 This BIOSCREEN...
A peine a-t-on fait un sort aux composes de plomb dans l'essence, que les additifs maintenant... more A peine a-t-on fait un sort aux composes de plomb dans l'essence, que les additifs maintenant utilises pointent en tete de la production mondiale des produits chimiques. A-t-on chasse Satan par Belzebuth? L'additif MTBE, ou ether methyltertiobutylique, est de plus en plus utilise en Europe, malgre sa faible biodegradabilite, une connaissance imparfaite de sa toxicite et les mauvaises experiences faites aux Etats-Unis en ce qui concerne la pollution des nappes phreatiques. Dans les eaux souterraines suisses, le MTBE est maintenant la substance la plus detectee parmi les polluants provenant de l'industrie, mais ses concentrations restent (encore?) essentiellement en dessous des valeurs critiques.
This study aimed at investigating whether stable isotopes can be used to monitor the progress of ... more This study aimed at investigating whether stable isotopes can be used to monitor the progress of volatile organic compounds (VOCs) volatilization from contaminated sediment during venting. Batches of a dry aquifer sediment were packed into stainless steel HPLC columns, humidified with distilled water and later contaminated by either liquid toluene or propan-2-ol. The VOCs were then volatilized by a stream of gas at room temperature, and the concentrations and stable isotope ratios of gaseous VOCs were recorded by isotope-ratio mass spectrometry. During early stages of volatilization of toluene, the isotope ratios Δδ13C shifted to more negative values by about -3 to -5‰ and the Δδ2H by more than -40‰, while the concentration remained at or near initial saturated vapor concentration. Depletion of the isotope ratios in the gas was explained by the vapor-liquid fractionation process, which is amplified by successive self-partitioning steps of gaseous VOC into remaining liquid VOC. For propan-2-ol the carbon isotope shift was negative like for toluene, whereas the H shift was positive. Hydrogen bonding in the liquid propan-2-ol phase causes a normal vapor-liquid H isotope effect which was described already in classical literature. The isotope shifts in the present experiments are larger than previously reported shifts due to phase-change processes and reach the magnitude of shifts usually observed in kinetic isotope fractionation.
The journal of physical chemistry. B, Jun 15, 2017
The relationship between the strength of the intermolecular interaction in liquid and the positio... more The relationship between the strength of the intermolecular interaction in liquid and the position-specific 13C fractionation observed during distillation was investigated. A range of molecules showing different intermolecular interactions in terms of mode and intensity were incorporated in the study. Although it had previously been suggested that during evaporation the diffusive 13C isotope effect in the thin liquid layer interfaced with vapor is not position-specific, herein we show that this is not the case. In particular, the position-specific effect was demonstrated for a series of alcohols. Our hypothesis is that intermolecular interactions in the liquid phase are the source of position-specific 13C fractionation observed on the molecule. A clear trend is observed between the 13C isotope effect of the carbon bearing the heteroatom of chemical function and the relative permittivity, the solvent hydrogen-bond acidity and the solvent hydrogen-bond basicity, while only a weak tren...
Environmental pollution (Barking, Essex : 1987), Jan 26, 2015
Isotopic fractionation of pollutants in terrestrial or aqueous environments is a well-recognized ... more Isotopic fractionation of pollutants in terrestrial or aqueous environments is a well-recognized means by which to track different processes during remediation. As a complement to the common practice of measuring the change in isotope ratio for the whole molecule using isotope ratio monitoring by mass spectrometry (irm-MS), position-specific isotope analysis (PSIA) can provide further information that can be exploited to investigate source and remediation of soil and water pollutants. Position-specific fractionation originates from either degradative or partitioning processes. We show that isotope ratio monitoring by (13)C NMR (irm-(13)C NMR) spectrometry can be effectively applied to methyl tert-butylether, toluene, ethanol and trichloroethene to obtain this position-specific data for partitioning. It is found that each compound exhibits characteristic position-specific isotope fractionation patterns, and that these are modulated by the type of evaporative process occurring. Such d...
Soil acidification is an ongoing natural process which can be enhanced by human activities or can... more Soil acidification is an ongoing natural process which can be enhanced by human activities or can be controlled by appropriate soil management practices. Two highly acidified urban garden soils, CHA and NTO, were subjected to single-extraction procedure by water to determine the extractable concentrations of Ca, Mg, K, Na, Al, Cu, Fe, Mn, Pb, Zn and . A modeling of effects of liming on soil solution was carried out from initial pH to pH 8.0 using the PHREEQC-2 code coupled with the PHREEQC.dat thermodynamic database. In NTO soil solution, liming increased the concentration of all cations, exception of Al when in CHA soil solution concentration of Ca, Cu, Fe and Pb increased. The chemical speciation of cations was evaluated in the soil solution. Basic cations Ca, Mg, K and Na were found as free forms (Ca 2+ , Mg 2+ , K + , Na + ) and sometimes complexed by sulfate (,). The concentration of the toxic free ion Al 3+ decreased quickly and was replaced by less toxic hydroxide complexes. ...
BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved contaminants in g... more BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved contaminants in groundwater, ideal for rapid screening and teaching. This work extends the BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three-dimensional exact solution of the reactive transport from a patch source, accounting for fractionation by first-order decay and/or sorption, is used. The results match those from a previously published isotope model but are much simpler to obtain. Two different isotopes may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, deviations of isotope ratios at specific reactive positions with respect to "bulk" ratios in the whole compound can be simulated. This model is named BIOSCREEN-AT-ISO and will be downloadable from the journal homepage.
BIOCHLOR is a well-known simple tool for evaluating the transport of dissolved chlorinated solven... more BIOCHLOR is a well-known simple tool for evaluating the transport of dissolved chlorinated solvents in groundwater, ideal for rapid screening and teaching. This work extends the BIOCHLOR model for the calculation of stable isotope ratios of carbon and chlorine isotopes in chloroethenes. An exact solution for the three-dimensional reactive transport of a chain of degrading compounds including sorption is provided in a spreadsheet and applied for modeling the transport of individual isotopes (12)C, (13)C, (35)Cl, (37)Cl from a constant source. The model can consider secondary isotope effects that can occur in the breaking of CCl bonds. The model is correctly reproducing results for δ(13)C and δ(37)Cl modeled by a previously published 1-D numerical model without secondary isotope effects, and is also reproducing results from a microcosm experiment with secondary chlorine isotope effects. Two applications of the model using field data from literature are further given and discussed. The new BIOCHLOR-ISO model is distributed as a spreadsheet (MS EXCEL) along with this publication.
Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in whic... more Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in which tetrachloro- and trichloroethene sequentially degrade to dichloroethenes, vinyl chloride (VC) and ethene, or ethane under reducing conditions. For detoxification, degradation must go beyond VC. Assessments based on ethene and ethane, however, are difficult because these products are volatile, may stem from alternative sources, can be further transformed and are not always monitored. To alternatively quantify degradation beyond VC, stable carbon isotope mass balances have been proposed where concentration-weighted CE isotope ratios are summed up and compared to the original source isotope ratio. Reported assessments, however, have provided not satisfactorily quantified results entailing greatly differing upper and lower estimates. This work proposes an integrative approach to better constrain the extent of total chloroethene degradation in groundwater samples. It is based on fitting of ...
In forensic environmental investigations the main issue concerns the inference of the original so... more In forensic environmental investigations the main issue concerns the inference of the original source of the pollutant for determining the liable party. Isotope measurements in geochemistry, combined with complimentary techniques for contaminant identification, have contributed significantly to source determination at polluted sites. In this work we have determined the intramolecular (13)C profiles of several molecules well-known as pollutants. By giving additional analytical parameters, position-specific isotope analysis performed by isotope ratio monitoring by (13)C nuclear magnetic resonance (irm-(13)C NMR) spectrometry gives new information to help in answering the major question: what is the origin of the detected contaminant? We have shown that isotope profiling of the core of a molecule reveals both the raw materials and the process used in its manufacture. It also can reveal processes occurring between the contamination site 'source' and the sampling site. Thus, irm-(13)C NMR is shown to be a very good complement to compound-specific isotope analysis currently performed by mass spectrometry for assessing polluted sites involving substantial spills of pollutant.
Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nu... more Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nuclear magnetic resonance spectrometry during the evaporation of 10 liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation, distillation). The observed effects are used to assess the validity of the Craig-Gordon isotope model for organic liquids. For seven liquids the overall isotope effect (IE) includes a vapor-liquid contribution that is strongly position-specific in polar compounds but less so in apolar compounds and a diffusive IE that is not position-specific, except in the alcohols, ethanol and propan-1-ol. The diffusive IE is diminished under forced evaporation. The position-specific isotope pattern created by liquid-vapor IEs is manifest in five liquids, which have an air-side limitation for volatilization. For the alcohols, undefined processes in the liquid phase create additional PSIEs. Three other liquids with limitations on the liquid side have a lower, highly position-specific, bulk diffusive IE. It is concluded that evaporation of organic pollutants creates unique position-specific isotope patterns that may be used to assess the progress of remediation or natural attenuation of pollution and that the Craig-Gordon isotope model is valid for the volatilization of nonpolar organic liquids with air-side limitation of the volatilization rate.
Investigations were made on the potential for biotransformation of ten chlorofluorocarbons and hy... more Investigations were made on the potential for biotransformation of ten chlorofluorocarbons and hydrochlorofluorocarbons under methanogenic conditions. Transformations were monitored in batch experiments by analysis of the concentrations in the headspace. Trichlorofluoromethane (CFC-11) was transformed to dichlorofluoromethane (HCFC-21) and to chlorofluoromethane (HCFC-31). The methanogenesis inhibitor 2-bromoethanesulfonate (BES) significantly decreased the CFC-11 transformation rate. 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) was transformed to two products which were deduced to be 1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a) and chlorotrifluoroethene (CTFE). No transformation was detected for dichlorodifluoromethane (CFC-12), chlorodifluoromethane (HCFC-22), 1,2-dichloro-1,1,2,2-tetra-fluoroethane (CFC-114), chloropentafluoroethane (CFC-115), 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b) and 1,1,1,2-tetrafluoroethane (HFC-134a).
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