Download or read book Constraining the Fate of Chlorinated Ethenes in Groundwater Systems Using Stable Carbon Compound Specific Isotope Analysis microform written by Gregory Franklin Slater and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2001 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Constraining the Fate of Chlorinated Ethenes in Groundwater Systems Using Stable Carbon Compound Specific Isotope Analysis written by Gregory Franklin Slater and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The isotopic effects of subsurface processes on the stable carbon isotopic composition, [delta]13C, of chlorinated ethenes were investigated using Compound Specific Isotope Analysis (CSIA). Headspace analysis was determined to be a robust, simple and effective method for sample preparation and analysis using Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS). No significant isotopic fractionation (>0.5 ‰) was observed during equilibrium volatilization of the chlorinated ethenes from aqueous solution. Further, no significant isotopic fractionation (>0.5 ‰) was associated with equilibrium sorption of TCE and PCE. These results confirmed the hypothesis that non-degradative, physical subsurface processes would not result in significant isotopic fractionation of the [delta]13C of the chlorinated ethenes. In contrast, degradation of the chlorinated ethenes resulted in large isotopic enrichments of the residual reactant in 13C, consistent with preferential reaction of molecules containing the lighter 12C isotope. This isotopic enrichment could be described by a Rayleigh model enrichment factor ([epsilon]). Rayleigh enrichment factors ([epsilon]) described isotopic fractionation of the chlorinated ethenes during microbial reductive dechlorination of most of the chlorinated ethenes, during abiotic reductive dechlorination of TCE by zero-valent iron, and during aerobic co-metabolic degradation of TCE by toluene ortho-monooxygenase. Enrichment factors varied with specific microbial consortia, with degradation pathway (reductive dechlorination versus aerobic co-metabolism); and for abiotic experiments, with different iron types and surface treatments. The observation of these isotopic enrichment trends indicated that CSIA can provide direct evidence of the occurrence of chlorinated ethene degradation in the field, independent of mass loss due to non-degradative subsurface processes. CSIA was applied at three field sites. These studies confirmed that the [delta] 13CTCE can be conserved at a site where plume geometry is controlled by advective and partitioning processes. Most importantly, they confirmed that CSIA could give direct confirmation of the occurrence of degradation of the chlorinated ethenes at field sites. Therefore CSIA of the [delta] 13C of the chlorinated ethenes represents a powerful tool for the investigation and monitoring of sources and fate of chlorinated ethenes in subsurface systems.
Download or read book Constraining the Fate of Chlorinated Ethenes in Groundwater Systems Using Stable Carbon Compound Specific Isotope Analysis written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Stable Carbon Compound Specific Isotope Analysis to Monitor and Quantify the Biodegradation of Chlorinated Ethenes in Groundwater Systems written by Penny Lea Morrill and published by . This book was released on 2004 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Identification and quantification of chlorinated ethene biodegradation were investigated using carbon compound specific isotope analysis (CSIA). A dynamic headspace sampling technique was developed and shown to be a robust, simple and effective method for isotopic analysis of dissolved chlorinated ethenes at low concentrations ([mu]g/L). This technique was used to monitor the biodegradation of tetrachloroethene (PCE) to ethene at a contaminated field site. At the field site, significant isotopic fractionation characteristic of biodegradation was observed in the isotope values of PCE and its degradation products trichloroethene (TCE), cis -1,2-dichloroethene (cDCE), and vinyl chloride (VC). During this study, stable carbon isotope analysis also provided one of the earliest lines of evidence for biodegradation. In laboratory and field experiments with an emplaced PCE dense nonaqueous phase liquid (DNAPL) source, isotopic fractionation was observed in the isotope values of the dechlorination intermediates produced by biodegradation, but not in the aqueous PCE near the DNAPL. These results confirm the hypothesis that isotopic fractionation due to biodegradation will not be observed in aqueous PCE close to the source zone. A model was developed to predict concentration values from isotope data for each step in the sequential reaction of PCE to non-toxic ethene. ...
Download or read book Investigation of Stable Carbon Compound Specific Isotope Analysis to Monitor and Quantify the Biodegradation Fo Chlorinated Ethenes in Groundwater Systems written by Penny Lea Morrill and published by . This book was released on 2005 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Use of Stable Isotopoe Analyses to Assess Natural Attenuation of Chlorinated Ethenes in Groundwater written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Chlorinated ethenes are among the most frequently detected groundwater contaminants in industrially developed countries. Although their degradation pathways have been understood, assessing the progress of natural attenuation of chlorinated ethenes still remains a challenge. This thesis explored the possibilities and limits of the use of compound-specific stable isotope analysis as a field investigation tool to document and to quantify the progress of natural attenuation of chlorinated ethenes. The thesis focused particularly on the fate of reductive dechlorination intermediates such as cis-dichloroethene (cDCE) and vinyl chloride (VC) as the success of natural attenuation of chlorinated ethenes depends principally on the fate of these compounds. Two field investigations were carried out to demonstrate the use of stable isotope analysis to characterize the progress of natural attenuation of chlorinated ethenes. One site was characterized as a complex hydrological and geochemical system at the groundwater-surface water interface where a tetrachloroethene- (PCE) plume discharged through the streambed. Another site was located under relatively stable hydrological conditions and characterized by a 2-km long plume of chlorinated ethenes. Laboratory studies evaluated the use of combined carbon and chlorine isotope analysis to distinguish different degradation pathways of cDCE and VC, and the same approach was employed at a field site to determine the fate of cDCE. Numerical studies evaluated the field applicability of isotope-based quantification, according to the Rayleigh isotope fractionation model, to estimate the extent of degradation and the first-order reaction rate under various flow conditions. In addition, a scheme to quantify the reductive dechlorination rates of chlorinated ethenes based on field concentration and isotope data at one of the field sites was proposed and evaluated with a series of 3D analytical solutions to accommodate sequential reactions. The stu.
Download or read book Application of Carbon chlorine Isotopic Analysis to Determine the Origin and Fate of Chlorinated Ethenes in Groundwater written by Alice Badin and published by . This book was released on 2015 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Utilization of Stable Carbon Isotope in the Verification of Bioremediation of Chlorinated Hydrocarbons written by and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall goal of this work was to test the feasibility of using stable carbon isotope analysis to verify in situ biodegradation of hydrocarbons and chlorinated ethenes under aerobic conditions. Specific objectives were to 1) determine d13C values for TCE and the various compounds to be used as co-substrates for TCE degradation; 2) evaluate effects of aerobic biodegradation of co-substrate compounds and TCE on gross fractionation of carbon isotopes as measured in the resulting CO2; 3) test the carbon isotope method for its ability to differentiate the source of the CO2 resulting from aerobic biodegradation; and 4) use samples from an appropriately contaminated bioventing site. Different degrees of fractionation were measured in both pure and mixed cultures for the different compounds tested in this study. Fractionation for toluene was slightly more negative than the starting compound. For JP-4, the fractionation of JP-4 resulted in d13C values much more negative than the starting compound. Fractionation for TCE results in d13C values more positive, indicating the CO2 had a higher percentage of 13C than the source compound. A mixture of toluene and TCE had a d13C value intermediate between the two. These results indicate, with the d13C values for these co-substrates and chlorinated ethenes sufficiently different, the degradation of one or the other can be determined. When both are being degraded an intermediate value can be obtained.
Download or read book Assessment of microbial transformation of chlorinated ethenes by compound specific isotope analysis and cultivation techniques written by and published by . This book was released on 2008 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Use of compound specific stable isotopes of carbon and chlorine for source tracking and assessments of biodegradation potential in a chlorinated solvent plume in Fort Worth Texas written by Christopher Lee Braun and published by . This book was released on 2005 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation Into the Fate of Groundwater Contaminants Using Compound Specific Isotope Analysis written by Shiran Qiu and published by . This book was released on 2013 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigations of Reductive Dechlorination Reactions of Chlorinated Ethenes and Ethanes on Zero valent Metals Using Compound Specific Isotopic Analysis written by Nancy Anne VanStone and published by . This book was released on 2006 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reductive dechlorination reactions occurring on zero-valent metal surfaces for chlorinated ethenes and chlorinated ethanes are investigated using compound specific isotopic analysis (CSIA) to measure carbon isotopic fractionation and carbon kinetic isotope effects (KIE). Reductive dechlorination of chlorinated contaminants on zero-valent iron (Fe0) is used for remediation purposes at over 100 sites worldwide employing permeable reactive barrier (PRB) technology. Degradation can occur via 3 main pathways: (1) alpha-elimination, (2) beta-elimination and (3) hydrogenolysis. Experiments documenting carbon isotopic fractionation observed during degradation of a suite of chlorinated ethenes are described, and it is demonstrated that reproducible carbon isotopic fractionation occurs for perchloroethene (PCE), trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinyl chloride (VC). The results for Fe0 from two different sources show distinct differences in both rates of reaction and isotopic fractionation factors (epsilon), particularly for the cis-DCE and VC. Using ground water samples from pre- and post-treatment of a Fe0 PRB at F.E. Warren Air Force Base, it is established that carbon isotopic fractionation of chlorinated ethenes follows the same principles under field conditions, and it is shown that CSIA, in combination with traditional compositional analysis, can help to resolve complex performance-related problems for PRBs. Finally, it is demonstrated that reaction pathways and mechanisms can be investigated using CSIA and ranges of epsilon and KIE are established for the investigated reactions on different zero-valent metals. In batch experiments monitoring dichloroethane (DCA) degradation on Zn0, CSIA was used to determine that a common rate limiting step occurs for hydrogenolysis and alpha-elimination reactions of 1,1-DCA. As well, overall epsilon and KIE are greater for beta-elimination of 1,2-DCA than for hydrogenolysis and alpha-elimination of 1,1-DCA. The degradation of a chlorinated ethene, cis-DCE, was investigated on Fe0. Direct measurements of epsilon and KIE for hydrogenolysis and beta-elimination were measured using CSIA. It is established that these reactions do not share a rate limiting step, and unique and reproducible carbon isotopic fractionation is associated with each reaction pathway. CSIA has been shown to be a versatile tool, aiding research as both a reliable diagnostic (i.e. identification of degradation) and as a valuable analytical instrument for mechanistic studies.
Download or read book Application of Stable Isotope Geochemistry to Assess TCE Biodegradation and Natural Attenuation in a Fractured Dolostone Bedrock written by Justin Allen Clark and published by . This book was released on 2011 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Isotopic analyses have been developed over the last 10 years as a method for determining chemical interactions of chlorinated solvents. These methods are especially promising for chlorinated ethenes, such as TCE and DCE. This study further develops and employs TCE and DCE compound specific isotopic analyses, along with chemical analyses, to characterize the degradation of TCE in fractured bedrock aquifers. The site chosen, in Smithville, Ontario, was contaminated by extremely high levels of TCE that is currently undergoing monitored pump-and-treat remediation. A collection of historical data and a extended description of the site are provided for potential use in other research. From December 2008 until April 2010 samples were collected from the site to provide additional data, including isotopic data. The redox conditions at the site are anoxic to reducing, with sulfate reduction and methanogenesis as dominant terminal electron accepting processes. Redox data indicates that electrochemical conditions are highly variable within the site, including areas near the source zone that are less reducing. Documented changes in groundwater conditions to much more reducing environments indicate that increased oxidation of organic matter is occurring at the Smithville site in select wells. Chemical analyses of potential TCE degradation products are employed to identify degradation. Many wells on site have dechlorination products. Combined chemical and redox shows that degradation seems to be a removal process for TCE at the Smithville site. Reductive dechlorination is shown to be a significant process forming degradation products such as DCE, VC, ethene and ethane. Production of DCE in significant amounts, above 1.0 ppb, was observed to only occur after 2003. In addition to this, DCE data shows that the percentage of DCE made up of cDCE is above 96%. This indicates that microbes most likely mediate the processes that formed DCE from TCE. The isotopic data had a high range in both carbon and chlorine isotopes. Chlorine isotopic data ranges from a [delta]37ClTCE of 1.39 to 4.69, and a [delta]37ClcDCE of 3.57 to 13.86. Carbon isotopic data ranges from a [delta]13CTCE of -28.9 to -20.7, and a [delta]13CcDCE of -26.5 to -11.82. Samples collected in the well closest to the source zone returned the lightest carbon and chlorine isotopic signatures. The range in values indicate varying degrees of degradation throughout the site, however the same wells have similar isotopic trends. Based on isotopic evidence, degradation past DCE to more degraded compounds also occurs at the Smithville site. However, determination of the degree of degradation of TCE and DCE was not implemented due to the variability in isotopic data.
Download or read book Application of Compound Specific Carbon and Chlorine Stable Isotope for Fingerprinting Sources of Chlorinated Compounds in Groundwater Journal of King Abdulaziz University written by Orfan Shouakar-Stash and published by . This book was released on 2000 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Carbon Isotopes Determination of Ground water Age and Estimated Characteristics of the Contaminant Source at Two Fuel spill Plumes Western Cape Cod Massachusetts 1996 written by Jennifer Savoie and published by . This book was released on 1999 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigating Controls on Variation in Isotopic Fractionation During Biodegradation of Chlorinated Ethenes and Ethanes written by Lisa Marie Douglas and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Kinetic isotope effects occur due to different reaction rates for light and heavy isotope-containing molecules, and are controlled by the bonds broken during degradation. For many primary pollutants, stable carbon, hydrogen, and chlorine isotope effects have been found to fit a Rayleigh model, indicating a single rate-limiting step. This thesis examines biodegradation pathways where additional controls and rate-limiting steps may affect observed isotope fractionation. Two haloalkane dehalogenases catalyzed aerobic 1,2-dichloroethane (1,2-DCA) dechlorination with very different enzyme affinities and turnover rates. However, carbon isotope enrichment factors were the same for both enzymes, reflecting the intrinsic kinetic isotope effect associated with C-Cl bond breakage. Carbon isotope fractionation was also largely constant during anaerobic 1,1,1-trichloroethane (1,1,1-TCA) biodegradation, even when the rate of biodegradation was inhibited by trichloroethene (TCE) co-contamination. This finding provided the basis for carbon isotope-based assessment of 1,1,1-TCE biodegradation at a TCE co-contaminated field site. The wide range of carbon isotope fractionation observed for anaerobic tetrachloroethene (PCE) biodegradation has been a matter of longstanding controversy. This work found the magnitude of carbon isotope fractionation for PCE biodegradation is related to the phylogenetic relationships between PCE-degrading organisms, which may allow for better selection of enrichment factors when assessing PCE biodegradation at field sites. Unexpectedly large variations in carbon isotope fractionation have also been observed for anaerobic TCE biodegradation. During C-Cl bond breakage, slopes of dual element carbon and chlorine isotope effects are typically constant for a given reaction because additional rate-limiting steps affect both elements in a similar way. Hence, characteristic combinations of C/Cl isotope effects can be used to investigate the underlying mechanistic details of a reaction. For TCE biodegradation, C/Cl isotope slopes indicate different reductive dehalogenases may catalyze different reductive dechlorination reaction pathways. This thesis advances the application of compound specific isotope analysis for assessing bioremediation of chlorinated ethenes and ethanes, as well our understanding of the enzymatic degradation mechanisms that catalyze biodegradation.
Download or read book Compound Specific Isotope Analysis 13C 37Cl 2H to Trace Induced Attenuation of Chlorinated Organic Contaminants in Groundwater written by Carme Audí Miró and published by . This book was released on 2014 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: El chloroform (CF), el tetracloroetè (PCE) i el tricloretè (TCE) són hidrocarburs clor-alifàtics densos usats extensament com a solvents industrials. Aquests compostos s'han alliberat al medi degut a un tractament inadequat dels seus residus. En aquesta tesi, l'efecte d'una barrera permeable reactiva de ferro zero valent (BPR-FZV) instal·lada en un emplaçament contaminat majoritàriament amb PCE, TCE i cis-dicloretè (cis-DCE, subproducte de TCE) ha estat avaluada. A més a més, s'ha proposat i desenvolupat una nova estratègia per a degradar el CF, el qual és un compost recalcitrant, consistent en la inducció de la hidròlisi alcalina del CF mitjançant residus de construcció basats en formigó. L'ànàlisi isotòpic de compost específic (AICE) és una eina valuosa per al monitoreig d'un sistema de tractament medi ambiental, basant-se en el fraccionament isotòpic d'un element durant les reaccions de transformació. L'objectiu general d'aquesta tesi és l'ús de l'anàlisi isotòpic de compost específic de 13C, 37Cl i 2H com una eina per a controlar els dos processos d'atenuació 1) la degradació dels eten-clorats mitjançant una BPR-FZV instal·lada en el camp; i, 2) la nova tècnica de remediació de CF proposada basada en l'ús de residus reciclats de la construcció per tal d'induir la hidròlisi alcalina del CF. En general, mitjançant la combinació dels isòtops de C, Cl i H, aquesta tesi aporta noves eines per discriminar la degradació dels compostos organoclorats d'estudi mitjançant FZV, respecte la biodegradació en el camp, així com també per a identificar fonts de contaminació d'origen industrial o de productes formats, entre d'altres aportacions. A més a més, el nou mètode proposat per a degradar el CF basat en la seva hidròlisi alcalina mitjançant l'ús de residus de construcció reciclats ha demostrat ser eficient en la degradació d'aquest contaminant, així com també, mitjançant l'ús de isòtops de carboni, ha demostrat funcionar en experiments pilot monitorejats a escala de camp.
