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Sample records for tce perchloroethylene pce

  1. Insights into dechlorination of PCE and TCE from carbon isotope fractionation by vitamin B12

    NASA Astrophysics Data System (ADS)

    Slater, G.; Sherwood Lollar, B.; Lesage, S.; Brown, S.

    2003-04-01

    Reductive dechlorination of perchloroethylene (PCE) and trichloroethylene (TCE) by vitamin B12 is both a potential remediation technique and an analogue of the microbial reductive dechlorination reaction. Stable carbon isotopic analysis, an effective and powerful tool for the investigation and monitoring of contaminant remediation, was used to characterize the isotopic effects of reductive dechlorination of PCE and TCE by vitamin B12 in laboratory microcosms. 10 mg/L vitamin B12 degraded greater than 90% of an initial concentration of PCE of 20 mg/L. TCE, the primary product of PCE degradation, accounted for between 64 - 72% of the PCE degraded. In experiments with TCE, 147 mg/L vitamin B12 degraded greater than 90% of an initial concentration of TCE of 20 mg/L. Cis-dichloroethene (cDCE), the primary product of TCE degradation, accounted for between 30 - 35% of the TCE degraded. Degradation of both PCE and TCE exhibited first order kinetics. Strong isotopic fractionation of the reactant PCE and of the reactant TCE was observed over the course of degradation. This fractionation could be described by a Rayleigh model with enrichment factors between -16.5 ppm and -15.8 ppm for PCE, and -17.2 ppm and -16.6 ppm for TCE. Fractionation was similar in all four experiments, with a mean enrichment factor of -16.5 +/- 0.6 ppm. These large enrichment factors indicate that isotopic analysis can be used to assess the occurrence of dechlorination of PCE and TCE by vitamin B12 in remediation situations. Significantly, the Rayleigh model could be used to predict the isotopic compositions of the major products of the reaction as well as the reactant, notwithstanding the lack of complete mass balance observed between product and reactant. This evidence suggests that isotopic fractionation is taking place during complexation of the chlorinated ethenes to vitamin B12, as has been suggested for reductive dechlorination by zero valent iron. The differences between e for this reaction and

  2. PCE/TCE DEGRADATION USING MULCH BIOWALLS

    EPA Science Inventory

    A passive reactive barrier (Biowall) was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contamin...

  3. Novel Chemical Detection Strategies for TCE and PCE

    SciTech Connect

    Pipino, Andrew C.R.

    2003-09-10

    Results describing two new applications of cavity ring-down spectroscopy (CRDS) will be discussed: (1) detection of TCE and PCE by refractive-index change using surface-plasmon-resonance (SPR)-enhanced CRDS, and (2) C-H overtone detection of TCE by evanescent wave CRDS (EW -CRDS) with a determination of absolute adsorbate surface coverage. The SPR-enhanced CRDS measurements show a minimum detectable concentration of 70 nanomol/L and 20 nanomo l/L for TCE and PCE, respectively, based on a one minute response time at 555 nm. The EW-CRDS measurements use the first C-H overtone of TCE occurring around 1640 nm. Spectra for both surface and gas -phase species are obtained in the evanescent wave. Employing the absolute absorption cross section for the C-H overtone of TCE obtained from gas-phase CRDS measurements, the adsorbate spectrum and corresponding absolute surface number density are determined. The requisite measure of molecular orientation is provided by the polarization dependence of the surface spectrum.

  4. Soil Vapor Extraction of PCE/TCE Contaminated Soil

    SciTech Connect

    Bradley, J.M.; Morgenstern, M.R.

    1998-08-01

    The A/M Area of the Savannah River Site soil and groundwater is contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE). Contamination is the result of previous waste disposal practices, once considered state-of-the-art. Soil Vapor Extraction (SVE) units have been installed to remediate the A/M Area vadose zone. SVE is a proven in-situ method for removing volatile organics from a soil matrix with minimal site disturbance. SVE alleviates the infiltration of contaminants into the groundwater and reduces the total time required for groundwater remediation. Lessons learned and optimization of the SVE units are also discussed.

  5. COMPLETE NATURAL ATTENUATION OF PCE AND TCE WITHOUT VINYL CHLORIDE AND ETHENE ACCUMULATION

    EPA Science Inventory

    A shallow aquifer at the Twin Cities Army Ammunition Plant (TCAAP) was contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE). Cisdichloroethylene (cis-DCE) is found in ground water at the site, indicating that reductive dehalogenation of PCE and TCE is occurrin...

  6. REPORT ON THE GEOELECTRICAL DETECTION OF SURFACTANT ENHANCED AQUIFER REMEDIATION OF PCE: PROPERTY CHANGES IN AQUEOUS SOLUTIONS DUE TO SURFACTANT TREATMENT OF PERCHLOROETHYLENE: IMPLICATIONS TO GEOPHYSICAL MEASUREMENTS

    EPA Science Inventory

    Select physicochemical properties of nine surfactants which are conventionally used in the remediation of perchloroethylene (PCE, a.k.a. tetrachloroethene) were evaluated with varying concentrations of PCE and indicator dyes in aqueous solutions using a response surface quadrati...

  7. COMPLETE NATURAL ATTENUATION OF A PCE AND TCE PLUME AFTER SOURCE REMOVAL

    EPA Science Inventory

    Disposal of the chlorinated solvents PCE and TCE at the Twin Cities Army Ammunition Plant (TCAAP) resulted in the contamination of groundwater in a shallow, unconsolidated sand aquifer. The resulting plume had moved over 1000 feet from the disposal source area and had impacted p...

  8. Air purification from TCE and PCE contamination in a hybrid bioreactors and biofilter integrated system.

    PubMed

    Tabernacka, Agnieszka; Zborowska, Ewa; Lebkowska, Maria; Borawski, Maciej

    2014-01-15

    A two-stage waste air treatment system, consisting of hybrid bioreactors (modified bioscrubbers) and a biofilter, was used to treat waste air containing chlorinated ethenes - trichloroethylene (TCE) and tetrachloroethylene (PCE). The bioreactor was operated with loadings in the range 0.46-5.50gm(-3)h(-1) for TCE and 2.16-9.02gm(-3)h(-1) for PCE. The biofilter loadings were in the range 0.1-0.97gm(-3)h(-1) for TCE and 0.2-2.12gm(-3)h(-1) for PCE. Under low pollutant loadings, the efficiency of TCE elimination was 23-25% in the bioreactor and 54-70% in the biofilter. The efficiency of PCE elimination was 44-60% in the bioreactor and 50-75% in the biofilter. The best results for the bioreactor were observed one week after the pollutant loading was increased. However, the process did not stabilize. In the next seven days contaminant removal efficiency, enzymatic activity and biomass content were all diminished. PMID:24316808

  9. BINARY DESORPTION ISOTHERMS OF TCE AND PCE FROM SILICA GEL AND NATURAL SOLIDS. (R822626)

    EPA Science Inventory

    Binary solute desorption isotherms of trichloroethylene (TCE) and tetrachloroethylene (PCE) at 100% relative humidity from silica gel and two well-characterized natural solids were investigated. Results indicated that the ideal adsorbed solution theory (IAST) was able to descr...

  10. Bubbleless dissolution of methane and hydrogen for the biodegradation of TCE and PCE

    SciTech Connect

    Semmens, M.J. . Dept. of Civil and Mineral Engineering); Gantzer, C.J.

    1993-10-01

    Trichloroethylene (TCE) and tetrachloroethylene (PCE) are two chlorinated aliphatic compounds commonly found in contaminated ground water. The use of methane in the biodegradation of TCE and the use of hydrogen in the biotransformation of PCE offer substantial cost advantages. TCE can be oxidized by several different groups of aerobic bacteria including those that use phenol, toluene, and methane as electron donors. A bulk cost comparison of these three substrates indicates that per electron equivalent phenol is 500 times and toluene is 13 times more expensive than methane. Anaerobic enrichment cultures grown on methanol, acetate, or hydrogen have the capacity to transform PCE all the way to ethylene via reductive dechlorination. A comparison of bulk costs of these three substrates per electron equivalent transferred to methyl reductase indicates that methanol is 13 times and acetate is 6 times more expensive than hydrogen. Because both gases are slightly soluble in water, the in situ and on-site bioreclamation of ground water contaminated with TCE or PCE can be limited by the ability to dissolve the gases into water.

  11. Effect of biosurfactants on the aqueous solubility of PCE and TCE.

    PubMed

    Albino, John D; Nambi, Indumathi M

    2009-12-01

    The effect of biosurfactants on the solubility of tetrachloroethylene (PCE) and trichloroethylene (TCE) was studied in batch experiments pertaining to their use for solubilization and mobilization of such contaminants in surfactant enhanced aquifer remediation. Biosurfactants, rhamnolipid and surfactin used in solubility studies were synthesized in our laboratory by Pseudomonas aeruginosa (MTCC 2297) and Bacillus subtilis (MTCC 2423), respectively. The efficiency of the biosurfactants in solubilizing the chlorinated solvents was compared to that of synthetic surfactants. The Weight Solubilization Ratio (WSR) values for solubilization of PCE and TCE by biosurfactants were very high compared to the values obtained for synthetic surfactants. Surfactin proved to be a better surfactant over rhamnolipid. The WSR of surfactin on solubilization of PCE and TCE were 3.83 and 12.5, respectively, whereas the values obtained for rhamnolipid were 2.06 and 8.36. The solubility of the chlorinated solvents by biosurfactants was considerably affected by the changes in pH. The aqueous solubility of PCE and TCE increased tremendously with decrease in pH. The solubility of biosurfactants was observed to decrease with the pH, favoring partitioning of surfactants into the chlorinated solvents in significant amounts at lower pH. The excessive accumulation of biosurfactants at the interface facilitated interfacial tension reductions resulting in higher solubility of the chlorinated solvents at pH less than 7. PMID:20183515

  12. FY00 Phytoremediation of Trichloroethylene and Perchloroethylene in the Southern Sector of SRS

    SciTech Connect

    Brigmon, R.L.

    2000-12-15

    This treatability study addresses the fate of volatile organic contaminants (VOCs) in an experiment that simulates a vegetated seepline supplied with trichloroethylene (TCE) and perchloroethylene (PCE) -contaminated groundwater. The primary objective is to determine how the trees uptake TCE and PCE, accumulate it, and/or transform it.

  13. Groundwater contamination by PCE and TCE: ATSDR's approach to evaluating public health hazard

    SciTech Connect

    Weis, B.K.; Susten, A.S.

    1999-07-01

    The Agency for Toxic Substances and Disease Registry (ATSDR) conducts public health assessments and consultations that evaluate the potential health impacts from human exposure to hazardous substances and recommend appropriate actions needed to mitigate or prevent exposures. ATSDR has conducted health evaluations for more than 80 federal facilities. Eighteen sites involve human exposure to tetrachloroethylene (PCE) or trichloroethylene (TCE) in groundwater. ATSDR uses a two-tiered approach to evaluate health hazard or risk from exposure. The first tier of analysis is described as a rote algorithmic determination of risk (RAD) and is used to screen exposure conditions that do not pose a health hazard under conservative assumptions of exposure. The second tier is a weight-of-evidence analysis that incorporates the traditional elements of risk assessment within the broader context of professional and biomedical health hazard for exposure pathways involving groundwater contamination at federal facilities.

  14. Transformation efficiency and formation of transformation products during photochemical degradation of TCE and PCE at micromolar concentrations

    PubMed Central

    2014-01-01

    Background Trichloroethene and tetrachloroethene are the most common pollutants in groundwater and two of the priority pollutants listed by the U.S. Environmental Protection Agency. In previous studies on TCE and PCE photolysis and photochemical degradation, concentration ranges exceeding environmental levels by far with millimolar concentrations of TCE and PCE have been used, and it is not clear if the obtained results can be used to explain the degradation of these contaminants at more realistic environmental concentration levels. Methods Experiments with micromolar concentrations of TCE and PCE in aqueous solution using direct photolysis and UV/H2O2 have been conducted and product formation as well as transformation efficiency have been investigated. SPME/GC/MS, HPLC/UV and ion chromatography with conductivity detection have been used to determine intermediates of degradation. Results The results showed that chloride was a major end product in both TCE and PCE photodegradation. Several intermediates such as formic acid, dichloroacetic acid, dichloroacetaldehyede, chloroform, formaldehyde and glyoxylic acid were formed during both, UV and UV/H2O2 treatment of TCE. However chloroacetaldehyde and chloroacetic acid were only detected during direct UV photolysis of TCE and oxalic acid was only formed during the UV/H2O2 process. For PCE photodegradation, formic acid, di- and trichloroacetic acids were detected in both UV and UV/H2O2 systems, but formaldehyde and glyoxylic acid were only detected during direct UV photolysis. Conclusions For water treatment UV/H2O2 seems to be favorable over direct UV photolysis because of its higher degradation efficiency and lower risk for the formation of harmful intermediates. PMID:24401763

  15. Sulfur removal from high-sulfur Illinois coal by low-temperature perchloroethylene (PCE) extraction. Final technical report, 1 September, 1992--31 August, 1993

    SciTech Connect

    Chou, M.I.M.; Lytle, J.M.; Ruch, R.R.; Kruse, C.W.; Chaven, C.; Hackley, K.C.; Hughes, R.E.; Harvey, R.D.; Frost, J.K.; Buchanan, D.H.; Stucki, J.W.; Huffman, G.P.; Huggins, F.E.

    1993-12-31

    The Midwest Ore Processing Co. (MWOPC) has reported a precombustion coal desulfurization process using perchloroethylene (PCE) at 120 C to remove up to 70% of the organic sulfur. The purposes of this research were to independently confirm and possibly to improve the organic sulfur removal from Illinois coals with the PCE desulfurization and to verify the ASTM forms-of-sulfur determination for evaluation of the process. An additional goal was to develop a dechlorination procedure to remove excess PCE from the PCE-treated coal. A laboratory scale operation of the MWOPC PCE desulfurization process was demonstrated, and a dechlorination procedure to remove excess PCE from the PCE-treated coal was developed. The authors have determined that PCE desulfurization removed mainly elemental sulfur from coal. The higher the level of coal oxidization, the larger the amount of elemental sulfur that is removed by PCE extraction. The increased elemental sulfur during short-term preoxidation is found to be pH dependent and is attributed to coal pyrite oxidation under acidic (pH < 2) conditions. The non-ASTM sulfur analyses confirmed the hypothesis that the elemental sulfur produced by oxidation of pyrite complicates the interpretation of analytical data for PCE process evaluations when only the ASTM forms-of-sulfur is used. When the ASTM method is used alone, the elemental sulfur removed during PCE desulfurization is counted as organic sulfur. A study using model compounds suggests that mild preoxidation treatment of coal described by MWOPC for removal of organic sulfur does not produce enough oxidized organic sulfur to account for the amounts of sulfur removal reported. Furthermore, when oxidation of coal-like organosulfur compounds does occur, the products are inconsistent with production of elemental sulfur, the product reported by MWOPC. Overall, it is demonstrated that the PCE process is not suitable for organic sulfur removal.

  16. Identification of TCE and PCE sorption and biodegradation parameters in a sandy aquifer for fate and transport modelling: batch and column studies.

    PubMed

    Kret, E; Kiecak, A; Malina, G; Nijenhuis, I; Postawa, A

    2015-07-01

    The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, K d = 0.0016; PCE, soil 1, K d = 0.0051; PCE, soil 2, K d = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, K f = 0.6493 and S max = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ(13)C values within the range of -23.6 ÷ -24.3‰ and -26.3 ÷-27.7‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer. PMID:25647491

  17. Understanding pH Effects on Trichloroethylene and Perchloroethylene Adsorption to Iron in Permeable Reactive Barriers for Groundwater Remediation.

    PubMed

    Luo, Jing; Farrell, James

    2013-01-01

    Metallic iron filings are becoming increasing used in permeable reactive barriers for remediating groundwater contaminated by chlorinated solvents. Understanding solution pH effects on rates of reductive dechlorination in permeable reactive barriers is essential for designing remediation systems that can meet treatment objectives under conditions of varying groundwater properties. The objective of this research was to investigate how the solution pH value affects adsorption of trichloroethylene (TCE) and perchloroethylene (PCE) on metallic iron surfaces. Because adsorption is first required before reductive dechlorination can occur, pH effects on halocarbon adsorption energies may explain pH effects on dechlorination rates. Adsorption energies for TCE and PCE were calculated via molecular mechanics simulations using the Universal force field and a self-consistent reaction field charge equilibration scheme. A range in solution pH values was simulated by varying the amount of atomic hydrogen adsorbed on the iron. The potential energies associated TCE and PCE complexes were dominated by electrostatic interactions, and complex formation with the surface was found to result in significant electron transfer from the iron to the adsorbed halocarbons. Adsorbed atomic hydrogen was found to lower the energies of TCE complexes more than those for PCE. Attractions between atomic hydrogen and iron atoms were more favorable when TCE versus PCE was adsorbed to the iron surface. These two findings are consistent with the experimental observation that changes in solution pH affect TCE reaction rates more than those for PCE. PMID:23626602

  18. Understanding pH Effects on Trichloroethylene and Perchloroethylene Adsorption to Iron in Permeable Reactive Barriers for Groundwater Remediation

    PubMed Central

    Luo, Jing; Farrell, James

    2013-01-01

    Metallic iron filings are becoming increasing used in permeable reactive barriers for remediating groundwater contaminated by chlorinated solvents. Understanding solution pH effects on rates of reductive dechlorination in permeable reactive barriers is essential for designing remediation systems that can meet treatment objectives under conditions of varying groundwater properties. The objective of this research was to investigate how the solution pH value affects adsorption of trichloroethylene (TCE) and perchloroethylene (PCE) on metallic iron surfaces. Because adsorption is first required before reductive dechlorination can occur, pH effects on halocarbon adsorption energies may explain pH effects on dechlorination rates. Adsorption energies for TCE and PCE were calculated via molecular mechanics simulations using the Universal force field and a self-consistent reaction field charge equilibration scheme. A range in solution pH values was simulated by varying the amount of atomic hydrogen adsorbed on the iron. The potential energies associated TCE and PCE complexes were dominated by electrostatic interactions, and complex formation with the surface was found to result in significant electron transfer from the iron to the adsorbed halocarbons. Adsorbed atomic hydrogen was found to lower the energies of TCE complexes more than those for PCE. Attractions between atomic hydrogen and iron atoms were more favorable when TCE versus PCE was adsorbed to the iron surface. These two findings are consistent with the experimental observation that changes in solution pH affect TCE reaction rates more than those for PCE. PMID:23626602

  19. PHOTOCHEMICAL REACTIVITY OF PERCHLOROETHYLENE

    EPA Science Inventory

    Perchloroethylene (PCE), a solvent used in dry cleaning, has been suspected of contributing significantly to photochemical ozone/oxidant (O3/Ox) problems in urban atmospheres. Past evidence, however, was neither complete nor consistent. To interpret more conclusively the past evi...

  20. Potential waste minimization of trichloroethylene and perchloroethylene via aerobic biodegradation.

    PubMed

    Wang, Jian; Cutright, Teresa J

    2005-01-01

    Trichloroethylene (TCE) and perchloroethylene (PCE) are two of the most frequently detected chlorinated organics found in groundwater. Biodegradation with a new aerobic consortium was used to ascertain the viability of bioremediation for waste minimization applications. After 1 week of treatment, the degradation rate constants, k, were between 0.004 and 0.012 d(-1) for initial concentrations of 54-664 microM TCE. When PCE was used as the sole contaminant, the k values were approximately 0.01 d(-1) regardless of the initial concentration. The addition of 0.2 microM toluene or phenol as an inducer dramatically increased TCE degradation. For instance, at 200 microM TCE the k value when toluene was added (0.03 d(-1)) was 2.2 times higher than without inducers (0.009 d(-1)). The addition of 0.2 microM phenol increased the rate constant by 58%. However, PCE degradation rates were not changed significantly. PMID:15991724

  1. Sulfur removal from high-sulfur Illinois coal by low-temperature perchloroethylene (PCE) extraction. [Quarterly] technical report, March 1, 1993--May 31, 1993

    SciTech Connect

    Chou, M.I.M.; Buchanan, D.H.; Stucki, J.W.

    1993-09-01

    The purposes of this project are: to independently confirm and possibly to improve the organic sulfur removal from Illinois coals with the PCE process developed by the Midwest Ore Processing Co. (MWOPC), to verify the forms-of-sulfur determination using the ASTM method for evaluation of the PCE process, and to develop a dechlorination procedure to remove excess PCE from the PCE-treated coal. The objectives for the second year are: to verify the possible effects of PCE treatment on coal-derived FeS{sub 2}, FeSO{sub 4}, and Fe{sub 2}(SO{sub 4}){sub 3} on ASTM coal analysis, to investigate the behavior of sulfur during oxidation and PCE desulfurization using the isotopically signatured coal sample, to investigate the effects of conditions and/or reagents on the oxidation of the organic-sulfur-model compounds, to evaluate the extended oxidation condition on the organic sulfur removal by PCE desulfurization, and to study other innovative pretreatment processes for the removal of organic sulfur from coal under mild conditions.

  2. Sorption of PCE in a reactive zero-valent iron system

    SciTech Connect

    Campbell, T.J.; Burris, D.R.

    1995-12-01

    The degradation of the chlorinated solvents perchloroethylene (PCE) and trichloroethylene (TCE) by reduction on the surface of zero-valent iron has emerged in recent years as a potentially viable approach to the remediation of chlorinated solvent-contaminated groundwaters. The sorption of PCE in a batch reactive zero-valent iron system was examined in this study. Aqueous PCE concentrations and total system PCE masses were determined in batch time-series experiments used to ascertain degradation kinetics. Sorbed concentrations were calculated using the difference between the aqueous phase and total system masses. The results showed Langmuir isotherm behavior which is consistent with a model of a finite number of available sorption sites. The kinetics of sorption could not be determined since degradation was also occurring. Knowledge of sorption to reactive and non-reactive sites is of importance in gaining a thorough understanding of the performance-behavior of the flow-through reactive systems envisioned for remediation technologies.

  3. Effects of trichloroethylene and perchloroethylene on wild rodents at Edwards Air Force Base, California, USA

    USGS Publications Warehouse

    Spring, S.E.; Miles, A.K.; Anderson, M.J.

    2004-01-01

    Effects of inhalation of volatilized trichloroethylene (TCE) or perchloroethylene (PCE) were assessed based on the health and population size of wild, burrowing mammals at Edwards Air Force Base (CA, USA). Organic soil-vapor concentrations were measured at three sites with aquifer contamination of TCE or PCE of 5.5 to 77 mg/L and at two uncontaminated reference sites. Population estimates of kangaroo rats (Dipodomys merriami and D. panamintinus) as well as hematology, blood chemistry, and histopathology of kangaroo rats and deer mice (Peromyscus maniculatus) were compared between contaminated and uncontaminated populations. Maximum soil-gas concentrations associated with groundwater contamination were less than 1.5 ??l/L of TCE and 0.07 ??l/L of PCE. Population estimates of kangaroo rats were similar at contaminated and reference sites. Hematology, blood chemistry, and histopathology of kangaroo rats and deer mice indicated no evidence of health effects caused by exposure. Trichloroethylene or PCE in groundwater and in related soil gas did not appear to reduce the size of small mammal populations or impair the health of individuals.

  4. Effects of trichloroethylene and perchloroethylene on wild rodents at Edwards Air Force Base, California, USA.

    PubMed

    Spring, Sarah E; Miles, A Keith; Anderson, Michael J

    2004-09-01

    Effects of inhalation of volatilized trichloroethylene (TCE) or perchloroethylene (PCE) were assessed based on the health and population size of wild, burrowing mammals at Edwards Air Force Base (CA, USA). Organic soil-vapor concentrations were measured at three sites with aquifer contamination of TCE or PCE of 5.5 to 77 mg/L and at two uncontaminated reference sites. Population estimates of kangaroo rats (Dipodomys merriami and D. panamintinus) as well as hematology, blood chemistry, and histopathology of kangaroo rats and deer mice (Peromyscus maniculatus) were compared between contaminated and uncontaminated populations. Maximum soil-gas concentrations associated with groundwater contamination were less than 1.5 microl/L of TCE and 0.07 microl/L of PCE. Population estimates of kangaroo rats were similar at contaminated and reference sites. Hematology, blood chemistry, and histopathology of kangaroo rats and deer mice indicated no evidence of health effects caused by exposure. Trichloroethylene or PCE in groundwater and in related soil gas did not appear to reduce the size of small mammal populations or impair the health of individuals. PMID:15378993

  5. A critical review of epidemiology studies of trichloroethylene and perchloroethylene and risk of renal-cell cancer.

    PubMed

    McLaughlin, J K; Blot, W J

    1997-01-01

    The epidemiology studies of trichloroethylene (TCE) and perchloroethylene (PCE) as they relate to risk of renal-cell cancer are critically reviewed. The studies fall into two basic groups: cohort studies of workers who use TCE or PCE and community-based case-control studies. Issues of bias, confounding, and chance are examined in relation to the studies. There is little evidence of an increased risk of renal-cell cancer and exposure to TCE or PCE. The few studies with elevations in risk suffer from important methodologic shortcomings. Although it is virtually impossible using epidemiology data to rule out conclusively a small increase in risk of renal-cell cancer, the totality of epidemiologic evidence clearly does not support a causal association with TCE or PCE. Future studies of these chemicals must include quantitative evidence of exposure and proper methodologic design, be large-scale in nature to detect small increases in risk, and provide a coherent interpretation of all epidemiology data on these solvents and risk of renal-cell cancer. PMID:9342621

  6. A shift in pathway of iron-mediated perchloroethylene reduction in the presence of sorbed surfactant--a column study.

    PubMed

    Li, Zhaohui; Willms, Cari; Alley, Jeff; Zhang, Pengfei; Bowman, Robert S

    2006-12-01

    Surface modification of zero-valent iron (ZVI) to enhance its reduction rates for chlorinated ethanes and ethenes has recently attracted great attention. In this research, the enhancement of perchloroethylene (PCE) reduction by ZVI in the presence of sorbed micelles of the cationic surfactant hexadecyltrimethylammonium (HDTMA) was examined in a series of laboratory column tests with varying flow rates and input PCE concentrations. Model simulations using HYDRUS-1D showed that the overall pseudo first-order rate constants for PCE reduction by ZVI increased by a factor of four in the presence of sorbed HDTMA admicelles. The increase in reduction rate was attributed to a higher distribution coefficient (K(d)) for contaminant sorption on surfactant-modified ZVI (SM-ZVI) compared to untreated ZVI. Modeling results also showed that in the presence of HDTMA admicelles 58-100% of PCE reduction occurred via hydrogenolysis. In contrast, only 12-25% PCE underwent hydrogenolysis when HDTMA was absent. The significant increase in TCE production during PCE reduction by SM-ZVI verified a shift in reaction pathway previously observed in batch studies, most likely from beta-elimination to hydrogenolysis. Although this shift in reaction pathway resulted in a higher accumulation of TCE, the combined concentrations of chlorinated hydrocarbons in the effluent were 1.5-5 times lower when SM-ZVI rather than unmodified ZVI was used. PMID:17055029

  7. Characterization of the effects of inhaled perchloroethylene on sustained attention in rats performing a visual signal detection task.

    PubMed

    Oshiro, Wendy M; Krantz, Q Todd; Bushnell, Philip J

    2008-01-01

    The aliphatic hydrocarbon perchloroethylene (PCE) has been associated with neurobehavioral dysfunction including reduced attention in humans. The current study sought to assess the effects of inhaled PCE on sustained attention in rats performing a visual signal detection task (SDT). Due to its similarities in physiological effect to toluene and trichloroethylene (TCE), two other commonly used volatile organic compounds (VOCs) known to reduce attention in rats, we hypothesized (1) that acute inhalation of PCE (0, 500, 1000, 1500 ppm) would disrupt performance of the SDT in rats; (2) that impaired accuracy would result from changes in attention to the visual signal; and (3) that these acute effects would diminish upon repetition of exposure. PCE impaired performance of the sustained attention task as evidenced by reduced accuracy [P(correct): 500 to 1500 ppm], elevated response time [RT: 1000 and 1500 ppm] and reduced number of trials completed [1500 ppm]. These effects were concentration-related and either increased (RT and trial completions) or remained constant [P(correct)] across the 60-min test session. The PCE-induced reduction in accuracy was primarily due to an increase in false alarms, a pattern consistent with reduced attention to the signal. A repeat of the exposures resulted in smaller effects on these performance measures. Thus, like toluene and TCE, inhaled PCE acutely impaired sustained attention in rats, and its potency weakened upon repetition of the exposure. PMID:18299185

  8. PHOTOCHEMICAL REACTIVITY OF PERCHLOROETHYLENE: A NEW APPRAISAL

    EPA Science Inventory

    Perchloroethylene (PCE), a solvent used in dry cleaning, has been suspected of contributing significantly to photochemical ozone/oxidant (O3/O(x)) problems in urban atmospheres. Past evidence, however, was neither complete nor consistent. To interpret more conclusively the past e...

  9. Dechlorination of perchloroethylene using zero-valent metal and microbial community

    NASA Astrophysics Data System (ADS)

    Ma, Changwen; Wu, Yanqing

    2008-07-01

    This research evaluates an integrated technique for the degradation of perchloroethylene (PCE) using a combination of zero-valent metal and an anaerobic microbial community. The microbial community was obtained from river sediment through a series of cultivation and enrichment processes, and was able to successfully convert PCE to ethylene. The degradation tests were carried out in five groups of reactors, i.e. Zn (zero-valent zinc), Fe (zero-valent iron), MB (a microbial community), ZnMB (zinc and a microbial community) and FeMB (iron and a microbial community). The results suggested that the FeMB system had the highest efficiency in removing PCE (about 99.9% after 24 days), followed by Zn (98.5%), ZnMB (84.8%), Fe (76.9%) and MB (49.6%). The degradation kinetics of PCE could be described by a pseudo-first-order reaction; the apparent reaction rate constants were 0.231, 0.187, 0.135, 0.076, 0.031 days-1 for the Zn, FeMB, ZnMB, Fe, and MB systems, respectively. Much more Cl- was detected as a by-product in the degradation tests using FeMB or ZnMB than using Fe or Zn. The results implied that not only PCE, but also the reaction intermediates, e.g., trichloroethylene (TCE) and dichloroethylenes (DCE isomers) may have been dechlorinated in the FeMB and ZnMB systems. Results suggest that the presence of the microbial community in the FeMB and ZnMB systems may not only affect the removal efficiency of PCE, but can also change the reaction pathways in the dechlorination process. The integrated technique combining the iron and the microbial community showed better degradation efficiency than the others; it may be viewed as an environmentally desirable remediation.

  10. Confronting workplace exposure to chemicals with LCA: examples of trichloroethylene and perchloroethylene in metal degreasing and dry cleaning.

    PubMed

    Hellweg, Stefanie; Demou, Evangelia; Scheringer, Martin; McKone, Thomas E; Hungerbühler, Konrad

    2005-10-01

    Life-Cycle Assessment (LCA) aims to assess all environmental impacts "from cradle to grave". Nevertheless, existing methods for Life-Cycle Impact Assessment (LCIA) generally do not consider impacts from chemical exposure at the workplace. This is a severe drawback, because neglecting occupational health effects may result in product or process optimizations at the expense of workers' health. We adapt an existing LCIA method to consider occupational health effects from the use of perchloroethylene (PCE) and trichloroethylene (TCE) in dry cleaning and metal degreasing. The results show that, in applications such as metal degreasing and dry cleaning, long-term (steady-state) concentrations at the workplace are up to 6 orders of magnitude higher than ambient air levels. Legal threshold values may be exceeded, depending on machine technology, size, and surrounding working conditions. The impact from workplace exposure to the total human-toxicity potential of the complete life cycle of PCE and TCE (including use, production, and disposal) is accordingly high. We therefore conclude that occupational health effects need to be considered in LCA to prevent overlooking key environmental-health impacts in LCA. PMID:16245853

  11. PHASE BEHAVIOR OF WATER/PERCHLOROETHYLENE/ANIONIC SURFACTANT SYSTEMS

    EPA Science Inventory

    Winsor Type I (o/w), Type II (w/o), and Type III (middle phase) microemulsions have been generated for water and perchloroethylene (PCE) in combination with anionic surfactants and the appropriate electrolyte concentration. The surfactant formulation was a combination of sodium d...

  12. Sonochemical degradation of perchloroethylene: the influence of ultrasonic variables, and the identification of products.

    PubMed

    Sáez, V; Esclapez, M D; Bonete, P; Walton, D J; Rehorek, A; Louisnard, O; González-García, J

    2011-01-01

    Sonochemistry is a technique that offers promise for pollutant degradation, but earlier studies on various chlorinated substrates do not give a definitive view of the effectiveness of this methodology. We now report a thorough study of ultrasonic operational variables upon perchloroethylene (PCE) degradation in water (variables include ultrasonic frequency, power and system geometry as well as substrate concentration) and we attempt to close the mass balance where feasible. We obtained fractional conversions of >97% showing very effective loss of pollutant starting material, and give mechanistic proposals for the reaction pathway based on cavitational phenomena inducing pyrolytic and free radical processes. We note major products of Cl(-) and CO(2)/CO, and also trichloroethylene (TCE) and dichloroethylene (DCE) at ppm concentrations as reported earlier. The formation at very low (ppb) concentration of small halocompounds (CHCl(3), CCl(4)) and also of higher-mass species, such as pentachloropropene, hexachloroethane, is noteworthy. But of particular importance in our work is the discovery of significant quantities of chloroacetate derivatives at ppm concentrations. Although these compounds have been described as by-products with other techniques such as radiolysis or photochemistry, this is the first time that these products have been identified in the sonochemical treatment of PCE; this allows a much more effective account of the mass balance and may explain earlier inconsistencies. This reaction system is now better identified, but a corollary is that, because these haloacetates are themselves species of some toxicity, the use of ultrasound here may not sufficiently diminish wastewater toxicity. PMID:20403718

  13. Effect of temperature on perchloroethylene dechlorination by a methanogenic consortium

    SciTech Connect

    Gao, J.; Skeen, R.S.; Hooker, B.S.

    1995-04-01

    The effect of temperature on the kinetics of growth, substrate metabolism, and perchloroethylene (PCE) dechlorination by a methanogenic consortium is reported. In all cases, a simple kinetic model accurately reflected experimental data. Values for the substrate and methane yield coefficients, and the maximum specific growth rate are fairly consistent at each temperature. Also, the substrate and methane yield coefficients show little temperature sensitivity. In contrast, both the maximum specific growth rate and the PCE dechlorination yield coefficient (Y{sub PCE}) are temperature dependent.

  14. Interaction of Perchloroethylene with Cerium Oxide in Three-Way Catalysts

    PubMed Central

    Rupp, Erik C.; Betterton, Eric A.; Arnold, Robert G.

    2010-01-01

    The role of cerium oxide on direct oxidation of perchloroethylene (PCE) by a three-way catalyst was explored. In the absence of an external oxidizing agent, PCE was oxidized over an alumina supported Pt/Rh three-way catalyst. We hypothesize that the chlorine atoms in the adsorbed PCE interact with oxygen in CeO2, reducing the cerium to create CeCl3. PMID:21218178

  15. Contamination of ground water by PCE - A national perspective

    USGS Publications Warehouse

    Moran, M.J.; Delzer, G.C.

    2006-01-01

    Perchloroethylene (PCE) has physical and chemical properties that make it likely to persist in groundwater if released to the environment. The US Geological Survey has collected or compiled data on the occurrence of PCE in groundwater from major aquifers around the US. These data represent the occurrence of PCE in the groundwater resource as a whole and not occurrence at specific release sites. PCE was detected at measurable concentrations in nearly one in 10 wells in major aquifers throughout the country. Trichloroethylene was found most commonly with PCE and its presence may be due, in part, to reductive dechlorination of PCE. This is an abstract of a paper presented at the Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Assessment, and Remediation Conference (Houston, TX 11/6-7/2006).

  16. Reductive Dechlorination of PCE DNAPL Source Zones

    NASA Astrophysics Data System (ADS)

    Sleep, B. E.; Edwards, E. A.

    2006-12-01

    A numerical modeling study was conducted to evaluate the potential impact of reductive dechlorination on enhancement of dissolution of source zones of perchloroethylene (PCE) dense nonaqueous phase liquid (DNAPL). The model included three-phase (water-gas-NAPL) flow and transport with interphase mass transfer. Reductive dechlorination of PCE to ethene was simulated with Monod kinetics with hydrogen as the direct electron donor. Hydrogen was produced from the transformation of ethanol to propionate and acetate. The model also included growth of dechlorinators, fermenters and methanogens, with methane generation from hydrogenotrophic and aceticlastic methanogenesis. The model was applied to the simulation of a two-dimensional bench scale study of reductive dechlorination of a PCE DNAPL source with biostimulation and bioaugmentation with a known PCE dechlorinating culture. In the bench scale study spatial and temporal variation of dissolved concentrations of chlorinated ethenes, electron donors were monitored. Quantitative PCR was also used to track the spatial and temporal variation of the dechlorinators. In this bench scale study, the maximum enhancement of PCE dissolution was approximately threefold. However, this enhancement was not sustained over the entire study, and apparent rates of PCE dissolution, as indicated by maximum dissolved concentrations of total ethenes, declined with time and increasing extent of source removal. The model was used to examine the impact on enhanced dissolution of reduction in source zone size, repartitioning of transformation products, and gas blockage from methane generation. Reductions in source zone size, coupled with a heterogeneous flow field, led to significant reductions in maximum concentrations measured in the bench scale study. Repartitioning of transformation products led to reductions in the maximum dissolved concentrations of PCE transformation products, leading to an apparent reduction in the enhancement of PCE

  17. ACUTE NEUROTOXIC EFFECTS OF INHALED PERCHLOROETHYLENE ON PATTERN VISUAL EVOKED POTENTIALS AS A FUNCTION OF EXPOSURE AND ESTIMATED BLOOD AND BRAIN CONCENTRATION.

    EPA Science Inventory

    Previous experiments have shown the effects of acute inhalation exposure to trichloroethylene (TCE) and toluene are related to the target tissue concentration at the time of testing. The current studies examined exposure to another volatile organic compound, perchloroethylene (P...

  18. Solubilization and mobilization of perchloroethylene by cosolvents in porous media

    SciTech Connect

    Van Valkenburg, M.E.

    1999-07-28

    Batch equilibrium studies conducted for perchloroethylene (PCE)/cosolvent systems determined that the log-linear solubility relationship is not a completely accurate method to predict solubility of PCE in cosolvent mixtures over an entire range of volume fractions. Batch studies resulted in cosolvency powers of 3.73 and 4.13 for ethanol and isopropanol, respectively. However, log-linear predictions may be adequate for estimations necessary for remediation efforts. The use of the Extended Hildebrand model is recommended. The interfacial tension (IFT) resulting from cosolvent mixtures when compared to the initial volume fraction of cosolvent showed a relationship, similar to the log-linear model. An ``IFT reduction power`` was determined for ethanol to be {minus}3.60, and isopropyl alcohol, {minus}5.80, describing the ability of cosolvents to reduce IFT with increasing volume fraction. IFT values are accurately estimated by PCE solubility in regimes conducive to cosolvent flushing.

  19. DEVELOPMENT OF A PHYSIOLOGICALLY BASED PHARMACOKINETIC MODEL FOR PERCHLOROETHYLENE USING TISSUE CONCENTRATION-TIME DATA

    EPA Science Inventory

    The tissue disposition of perchloroethylene (PCE) was characterized experimentally in rats in order to: 1) btain input parameters from in vivo data for the development of a physiologically-based pharmacokinetic (PBPK) model; and 2) use the PBPK model to predict the deposition of ...

  20. PROPERTY CHANGES IN AQUEOUS SOLUTIONS DUE TO SURFACTANT TREATMENT OF PCE: IMPLICATIONS TO GEOPHYSICAL MEASUREMENTS

    EPA Science Inventory

    Select physicochemical properties of aqueous solutions composed of surfactants, dye, and

    perchloroethylene (PCE) were evaluated through a response surface quadratic design

    model of experiment. Nine surfactants, which are conventionally used in the

    remediation...

  1. Catalytic Dechlorination of Gas-phase Perchloroethylene under Mixed Redox Conditions

    PubMed Central

    Orbay, Özer; Gao, Song; Barbaris, Brian; Rupp, Erik; Sáez, A. Eduardo; Arnold, Robert G.; Betterton, Eric A.

    2008-01-01

    The validity of a new method to destroy gas-phase perchloroethylene (PCE) is demonstrated at bench scale using a fixed-bed reactor that contains a Pt/Rh catalyst. Hydrogen and oxygen were simultaneously fed to the reactor together with PCE. The conversion efficiencies of PCE were sensitive to H2/O2 ratio and reactor temperature. When the temperature was ≥ 400 °C and H2/O2 was ≥ 2.15, PCE conversion efficiency was maintained at ≥ 90%. No catalyst deactivation was observed for over two years, using only mild, convenient regeneration procedures. It is likely that PCE reduction steps precede oxidation reactions and that the importance of oxidation lies in its elimination of intermediates that would otherwise lead to catalyst poisoning. In practice, this catalytic dechlorination method holds potential for low-cost, large-scale field operation. PMID:19234593

  2. A mass balance study of the phytoremediation of perchloroethylene-contaminated groundwater

    PubMed Central

    James, C. Andrew; Xin, Gang; Doty, Sharon L.; Muiznieks, Indulis; Newman, Lee; Strand, Stuart E.

    2010-01-01

    A mass balance study was performed under controlled field conditions to investigate the phytoremediation of perchloroethylene (PCE) by hybrid poplar trees. Water containing 7–14 mg L−1 PCE was added to the test bed. Perchloroethylene, trichloroethylene, and cis-dichloroethylene were detected in the effluent at an average of 0.12 mg L−1, 3.9 mg L−1, and 1.9 mg L−1, respectively. The total mass of chlorinated ethenes in the water was reduced by 99%. Over 95% of the recovered chlorine was as free chloride in the soil, indicating near-complete dehalogenation of the PCE. Transpiration, volatilization, and accumulation in the trees were all found to be minor loss mechanisms. In contrast, 98% of PCE applied to an unplanted soil chamber was recovered as PCE in the effluent water or volatilized into the air. These results suggest that phytoremediation can be an effective method for treating PCE-contaminated groundwater in field applications. PMID:19345455

  3. ACUTE BEHAVIORAL EFFECTS OF INHALED PERCHLOROETHYLENE IN RATS ARE DIRECTLY RELATED TO ITS CONCENTRATION IN THE BRAIN.

    EPA Science Inventory

    Perchloroethylene (PCE) is a volatile organic compound (VOC), frequently used in dry cleaning processes, that is currently being assessed by EPA for its risk to human health. Many VOCs are acutely neurotoxic and have been shown to affect attentional processes in humans and animal...

  4. Electrochemical degradation of perchloroethylene in aqueous media: an approach to different strategies.

    PubMed

    Sáez, Verónica; Esclapez Vicente, M D; Frías-Ferrer, Angel J; Bonete, Pedro; González-García, José

    2009-05-01

    An approaching study to the electrochemical degradation of perchloroethylene (PCE) in water has been carried out using controlled current density degradation electrolyses. The different electrochemical strategies to degrade perchloroethylene in aqueous media (i.e. cathodic, anodic and dual treatments) have been checked using divided and undivided configurations. The influence of the initial concentration, pH and current density on the general behavior of the system has been studied, and special attention was paid to the nature of the byproducts formed and to the analysis of the closed mass balance at the end of the reaction. Results from several analytical techniques have been compared. Undivided configuration provides the best results in these experimental conditions, with degradation percentages higher than 50% and with only 6% of the initial perchloroethylene concentration remaining in the system. PMID:19303130

  5. Studies on the use of perchloroethylene as a heavy medium for the removal of pyrites from coal

    SciTech Connect

    Thome, T.L.; Fullerton, K.L.; Lee, S.

    1996-12-31

    Previous studies have shown that perchloroethylene (PCE) shows promise for use as a heavy medium for the removal of pyrites from fine coal. The studies are continued here, as the coal cleaning effectiveness of mixtures of PCE and kerosene are investigated. Float/sink experiments are run for different medium densities obtained by varying the proportions of PCE and kerosene. The effectiveness of the cleaning process is judged by data taken from a long tube sampling apparatus. Among the variables investigated are medium density, residence time, and solvent-to-coal ratio. The data is used to support scale-up predictions for a plant apparatus.

  6. Cometabolic degradation of TCE and DCE without intermediate toxicity

    SciTech Connect

    Bielefeldt, A.R.; Stensel, H.D.; Strand, S.E.

    1995-11-01

    Trichloroethylene (TCE) and cis-1,2-dichloroethylene (DCE) cometabolic degradation by a filamentous, phenol-oxidizing enrichment from a surface-water source were investigated in batch tests. No intermediate toxicity effects were evident during TCE or DCE degradation for loadings up to 0.5 mg TCE/mg VSS or 0.26 mg DCE/mg VSS. Phenol addition up to 40 mg/L did not inhibit TCE or DCE degradation. TCE specific degradation rates ranged from 0.28 to 0.51 g TCE/g VSS-d with phenol present, versus an average endogenous rate of 0.18 g TCE/g VSS-d. DCE specific degradation rates ranged from 0.79 to 2.92 g DCE/g VSS-d with phenol present, versus 0.27 to 1.5 g DCE/g VSS-d for endogenous conditions. There was no inhibition of DCE degradation rates at concentrations as high as 83 mg/L. TCE degradation rates declined between 40 and 130 mg/L TCE. Perchloroethylene, 1,1,1-trichloroethane, and chloroform were not degraded.

  7. EMISSIONS OF PERCHLOROETHYLENE FROM DRY CLEANED FABRICS

    EPA Science Inventory

    A study was conducted to evaluate the emissions of perchloroethylene (tetrachloroethylene) from dry cleaned fabrics to determine: (a) how the introduction of fresh dry cleaning into a home affects the indoor concentration of perchloroethylene, and (b) the effectiveness of ‘airing...

  8. Thermocatalytic Destruction of Gas-Phase Perchloroethylene Using Propane as a Hydrogen Source

    PubMed Central

    Willinger, Marty; Rupp, Erik; Barbaris, Brian; Gao, Song; Arnolda, Robert; Betterton, Eric; Sáez, A. Eduardo

    2009-01-01

    The use of propane in combination with oxygen to promote the destruction of perchloroethylene (PCE) over a platinum (Pt)/rhodium (Rh) catalyst on a cerium/zirconium oxide washcoat supported on an alumina monolith was explored. Conversions of PCE were measured in a continuous flow reactor with residence times less than 0.5 s and temperatures ranging from 200 to 600°C. The presence of propane was shown to increase significantly the conversion of PCE over oxygen-only conditions. Conversions close to 100% were observed at temperatures lower than 450°C with 20% oxygen and 2% propane in the feed, which makes this process attractive from a practical standpoint. In the absence of oxygen, PCE conversion is even higher, but the catalyst suffers significant deactivation in less than an hour. Even though results show that oxygen competes with reactants for active sites on the catalyst, the long-term stability that oxygen confers to the catalyst makes the process an efficient alternative to PCE oxidation. A Langmuir-Hinshelwood competitive adsorption model is proposed to quantify PCE conversion. PMID:19217713

  9. Industrial-hygiene report, perchloroethylene at Key Club Cleaners, Skokie, Illinois, July 18, 1979

    SciTech Connect

    Roberts, D.R.

    1980-08-13

    An on site visit was made to the Key Club Cleaners located in Skokie, Illinois as part of an industrywide mortality and industrial hygiene study of the exposure of dry cleaning workers to perchloroethylene (PCE). Current exposure levels of PCE were determined at the facility using battery operated pumps and charcoal tubes. The company used PCE as a dry cleaning solvent since cleaning began at the site in October of 1978. The facility was housed in a one story building with dimensions of about 40 feet by 100 feet. About 90 gallons of PCE were consumed each month during dry cleaning and about 1800 pounds of clothing were dry cleaned each week. The work force numbered nine persons. The time weighted average exposures to PCE of the dry cleaner/spotter and the presser were 49 and 8.5 parts per million (ppm), respectively. The 5 minute peak exposures to the dry cleaner measured during garment transfer ranged from 316 to 447ppm PCE. While the time weighted average exposures were within recommended guidelines, the peak samples during transfer exceeded all recommended levels. The author recommends measures to lower the exposure level.

  10. Unraveling the Mechanism and Regioselectivity of the B12-Dependent Reductive Dehalogenase PceA.

    PubMed

    Liao, Rong-Zhen; Chen, Shi-Lu; Siegbahn, Per E M

    2016-08-22

    PceA is a cobalamin-dependent reductive dehalogenase that catalyzes the dechlorination of perchloroethylene to trichloroethylene and then to cis-dichloroethylene as the sole final product. The reaction mechanism and the regioselectivity of this enzyme are investigated by using density functional calculations. Four different substrates, namely, perchloroethylene, trichloroethylene, cis-dichloroethylene, and chlorotheylene, have been considered and were found to follow the same reaction mechanism pattern. The reaction starts with the reduction of Co(II) to Co(I) through a proton-coupled electron transfer process, with the proton delivered to a Tyr246 anion. This is followed by concerted C-Cl bond heterolytic cleavage and proton transfer from Tyr246 to the substrate carbon atom, generating a Co(III) -Cl intermediate. Subsequently, a one-electron transfer leads to the formation of the Co(II) -Cl product, from which the chloride and the dehalogenated product can be released from the active site. The substrate reactivity follows the trend perchloroethylene>trichloroethylene≫cis-dichloroethylene≫chlorotheylene. The barriers for the latter two substrates are significantly higher compared with those for perchloroethylene and trichloroethylene, implying that PceA does not catalyze their degradation. In addition, the formation of cis-dichloroethylene has a lower barrier by 3.8 kcal mol(-1) than the formation of trans-dichloroethylene and 1,1-dichloroethylene, reproducing the regioselectivity. These results agree quite well with the experimental findings, which show cis-dichloroethylene as the sole product in the PceA-catalyzed dechlorination of perchloethylene and trichloroethylene. PMID:27459105

  11. Influence of different electron donors and acceptors on dehalorespiration of tetrachloroethene by Desulfitobacterium frappieri TCE1

    SciTech Connect

    Gerritse, J.; Drzyzga, O.; Kloetstra, G.; Keijmel, M.; Wiersum, L.P.; Hutson, R.; Collins, M.D.; Gottschal, J.C.

    1999-12-01

    Strain TCE1, a strictly anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene (PCE) and trichloroethane (TCE), was isolated by selective enrichment from a PCE-dechlorinating chemostat mixed culture. Strain TCE1 is a gram-positive, motile, curved rod-shaped organism that is 2 to 4 by 0.6 to 0.8 {micro}m and has approximately six lateral flagella. The pH and temperature optima for growth are 7.2 and 35 C, respectively. On the basis of a comparative 16S rRNA sequence analysis, this bacterium was identified as a new strain of Desulfitobacterium frappieri, because it exhibited 99.7% relatedness to the D. frappieri type strain, strain PCP-1. Growth with H{sub 2}, format, L-lactate, butyrate, crotonate, or ethanol as the electron donor depends on the availability of an external electron acceptor. Pyruvate and serine can also be used fermentatively. Electron donors (except format and H{sub 2}) are oxidized to acetate and CO{sub 2}. when L-lactate is the growth substrate, strain TCE1 can use the following electron acceptors: PCE and TCE (to produce cis-1,2-dichloroethene), sulfite and thiosulfate (to produce sulfide), nitrate (to produce nitrite), and fumarate (to produce succinate). Strain TCE1 is not able to reductively dechlorinate 3-chloro-4-hydroxyphenylacetate. The growth yields of the newly isolated bacterium when PCE is the electron acceptor are similar to those obtained for other dehalorespiring anaerobes (e.g., Desulfitobacterium sp. strain PCE1 and Desulfitobacterium hafniense) and the maximum specific reductive dechlorination rates are 4 to 16 times higher. Dechlorination of PCE and TCE is an inducible process. In PCE-limited chemostat cultures of strain TCE1, dechlorination is strongly inhibited by sulfite but not by other alternative electron acceptors, such as fumate or nitrate.

  12. In situ biodegradation of perchloroethylene in constructed wetland mesocosms

    SciTech Connect

    Hoylman, A.M.; Rosensteel, B.A.; Trettin, C.C.

    1994-12-31

    Anaerobic reductive dehalogenation initiates degradation of highly chlorinated organic compounds. Subsequent intermediate chlorinated compounds are in turn more readily degraded in aerobic environments. Thus, complete degradation of chlorinated compounds to nontoxic end products requires both anaerobic and aerobic environments. These environments are provided by constructed wetland bioremediation systems, which through the interaction of vegetation, microbial, chemical, and physical processes, result in waste water renovation. The authors integrated the ecological engineering technology of constructed wetland systems with developments in plant-rhizosphere degradation of organic contaminants to examine the effectiveness of constructed wetland systems for in situ bioremediation of waste water contaminated with a chlorinated hydrocarbon, perchloroethylene (PCE) and an aromatic hydrocarbon, toluene. A mesocosm was designed to provide sequential anaerobic and vegetated-aerobic cells with complete control of water and gas flux and to emulate wetland properties such as hydric soil composition, physicochemical parameters, and the presence of wetland vegetation (Eleocharis acicularis). Treatments included contaminated and non-contaminated wetland cells and sterile controls. The fate and transport of PCE, toluene, and metabolic by-products were determined in effluent and chamber headspace, and extracts of soil and plant tissue. These analyses provide the basis for evaluating contaminant fate in wetland systems. Manipulation of aeration and hydrologic regimes in the wetland cells will facilitate testing conditions that affect degradation processes. The experimental apparatus is a innovative design for experimentation on the degradation of volatile organic compounds in plant-soil systems.

  13. Removal of perchloroethylene from a layered soil system by steam flushing

    SciTech Connect

    She, H.Y.; Sleep, B.E.

    1999-10-01

    Steam flushing experiments were conducted in a two-dimensional chamber containing two layers of F75 silica sand separated by a layer of finer F110 silica sand. Perchloroethylene (PCE), which had spilled into the chamber under water-saturated conditions, formed a pool on the F110 sand layer. Steam was injected above the F110 sand layer. Temperatures, moisture content, and PCE concentrations in the chamber were monitored. Samples, taken from the various locations in the sand chamber, indicated that complete removal of PCE from the steam zone was achieved, with an 84% overall recovery. Some downward displacement of PCE-contaminated water through the F110 sand layer was observed and a small amount of gravity override occurred. Channeling of steam was minimal. The experiment indicates that steam flushing may be used successfully for removal of PCE from relatively homogeneous soils. Issues of gravity override and downward mobilization of contaminants must be considered in applying steam flushing at the field scale.

  14. Alternatives to perchloroethylene-based garment care: Assessing the viability of professional wet cleaning. Final report

    SciTech Connect

    Gottlieb, R.; Sinsheimer, P.; Goodheart, J.; Tranby, C.; Bechtel, L.

    1997-12-01

    The report analyzes the viability of Cleaner by Nature, a 100% professional wet cleaner, and whether professional wet cleaning represents a viable pollution prevention approach in eliminating perchloroethylene (PCE), a chemical solvent used in dry cleaning. The analysis includes a comprehensive plant level case study, and comparative performance, financial, and environmental assessments of wet cleaning and PCE-based dry cleaning. The major issues associated with the viability analyses were identified and specific information was collected in relation to how the clothes were cleaned (a customer garment profile, a problem garment analysis, a technical evaluation or repeat clean test, a wearer survey, and customer satisfaction surveys); how wet cleaning did financially (a start-up cost analysis and a profit/loss analysis); what environmental impacts were identified (water, energy, and chemical inputs and outputs); and what contributing factors (technology changes, garment manufacturing and labeling, and regulator or legislative actions) influence the viability of professional wet cleaning.

  15. Gas-phase photocatalytic degradation of perchloroethylene on glass pellets immobilized with TiO{sub 2}

    SciTech Connect

    Hung, C.H.; Yuan, C.S.

    1998-12-31

    The objective of this research was to study gas-phase photocatalytic degradation of perchloroethylene (PCE) under illumination of four 10-W near-ultraviolet (UV) light lamps. Experiments were performed in a photocatalytic reactor packed with Degussa P-25 TiO{sub 2}-coated glass pellets. Anatase TiO{sub 2} was applied as the photocatalyst in the investigation. The effects of reaction parameters including influent PCE concentrations (10 to 50 ppm), water vapor content (0 to 100 % relative humidity), oxygen concentrations (0.31 to 21%), reactor space times (0.55 to 1.83 seconds), and irradiated light intensity (0.4 to 1.0 mW/cm{sup 2}) were investigated in the study. Experimental results indicated that fast photocatalytic degradation of PCE took place in the presence of TiO2 illuminated with near-UV light. Experimental results also showed that the highest degradation rate and quantum efficiency of PCE were 0.523 m mol/secgm and 5.2 %, respectively. The highest conversion ratio of PCE of 99.8 % was achieved in the study. Greater conversation ratios of PCE were observed for longer reaction time. Increase in the reaction rates of PCE by increasing influent PCE and oxygen concentrations were presented. Higher reaction rates of PCE under stronger illumination light intensity were detected. The degradation rates of PCE were proportional to light intensity with the power order of 1.2. On the other hand, the inhibited degradation of PCE was observed in the presence of water vapor. Lower reaction rates of PCE were detected when water vapor was present in the reaction. A modified Langmuir-Hishelwood kinetic was applied to model photocatalytic degradation of PCE. Two different adsorption sites on irradiated TiO2{sub 2} surfaces for the adsorption of PCE and oxygen molecules respectively were assumed in the model. The assumption of water vapor competing with PCE for reactive sites was considered in the reaction.

  16. Regeneration of surfactant-modified zeolite after saturation with chromate and perchloroethylene.

    PubMed

    Li, Z; Bowman, R S

    2001-01-01

    Surfactant-modified zeolites (SMZ) have drawn recent attention as sorbents due to their removal of multiple types of contaminants and low material cost. However, like most sorbents, SMZ has a finite sorption capacity for different contaminants. The potential applications, economics, and efficiency of SMZ as a sorbent are related to the ability to regenerate the material. This paper reports several methods to regenerate chromate- and perchloroethylene-saturated SMZ. Regeneration of chromate-saturated SMZ was achieved by flushing with a sodium carbonate/sodium hydroxide solution. However, this high-pH solution increased the counterion competition for chromate sorption sites and decreased the chromate sorption capacity of the regenerated SMZ. As an alternative regeneration method, chromate sorbed to SMZ was reduced to Cr(III) in situ using sodium dithionite solution. Although reduction with dithionite restored the chromate sorption maximum, the chromate sorption intensity was lowered, possibly due to the competition by sulfate (generated from oxidation of dithionite) for chromate sorption sites. Carbonate-regenerated SMZ showed no loss of sorption affinity for perchloroethylene (PCE) compared to virgin SMZ. Air sparging of PCE-saturated SMZ fully regenerated the SMZ. The results show that it is possible to regenerate and re-use SMZ following saturation with anionic or nonpolar organic contaminants. PMID:11257888

  17. Factors controlling the carbon isotope fractionation of tetra- and trichloroethene during reductive dechlorination by Sulfurospirillum ssp. and Desulfitobacterium sp. strain PCE-S.

    PubMed

    Cichocka, Danuta; Siegert, Michael; Imfeld, Gwenaël; Andert, Janet; Beck, Kirsten; Diekert, Gabriele; Richnow, Hans-Hermann; Nijenhuis, Ivonne

    2007-10-01

    Carbon stable isotope fractionation of tetrachloroethene (PCE) and trichloroethene (TCE) was investigated during reductive dechlorination. Growing cells of Sulfurospirillum multivorans, Sulfurospirillum halorespirans, or Desulfitobacterium sp. strain PCE-S, the respective crude extracts and the abiotic reaction with cyanocobalamin (vitamin B(12)) were used. Fractionation of TCE (alphaC=1.0132-1.0187) by S. multivorans was more than one order of magnitude higher than values previously observed for tetrachloroethene (PCE) (alphaC=1.00042-1.0017). Similar differences in fractionation were observed during reductive dehalogenation by the close relative S. halorespirans with alphaC=1.0046-1.032 and alphaC=1.0187-1.0229 for PCE and TCE respectively. TCE carbon isotope fractionation (alphaC=1.0150) by the purified PCE-reductive dehalogenase from S. multivorans was more than one order of magnitude higher than fractionation of PCE (alphaC=1.0017). Carbon isotope fractionation of TCE by Desulfitobacterium sp. strain PCE-S (alphaC=1.0109-1.0122) as well as during the abiotic reaction with cyanocobalamin (alphaC=1.0154) was in a similar range to previously reported values for fractionation by mixed microbial cultures. In contrast with previous results with PCE, no effects due to rate limitations, uptake or transport of the substrate to the reactive site could be observed during TCE dechlorination. Our results show that prior to a mechanistic interpretation of stable isotope fractionation factors it has to be carefully verified how other factors such as uptake or transport affect the isotope fractionation during degradation experiments with microbial cultures. PMID:17908097

  18. NEUROTOXICITY OF TETRACHLOROETHYLENE (PERCHLOROETHYLENE): DISCUSSION PAPER

    EPA Science Inventory

    This paper is a background document for a meeting of neurotoxicity experts to discuss the central nervous system effects of exposure to perchloroethylene (perc). The document reviews the literature on neurological testing of people exposed to perc occupationally in dry cleanin...

  19. MEASUREMENT OF PERCHLOROETHYLENE IN AMBIENT AIR

    EPA Science Inventory

    Perchloroethylene (i.e., tetrachloroethylene) is an organic solvent widely used in dry cleaning and industrial metal degreasing operations. Short-term field studies were conducted in each of three major metropolitan areas which were selected on the basis of the number, density an...

  20. Nature's Helpers: Using Microorganisms to Remove Trichloroethene (TCE) from Groundwater

    NASA Astrophysics Data System (ADS)

    Delgado, A. G.; Krajmlanik-Brown, R.; Fajardo-Williams, D.; Halloum, I.

    2015-12-01

    Organic chlorinated solvents, such as perchloroethene (PCE) and trichloroethene (TCE), are toxic pollutants threatening ground water quality worldwide and present at many superfund sites. Bioremediation using microorganisms is a promising, green, efficient, and sustainable approach to remove PCE and TCE contamination from soil and groundwater. Under anaerobic conditions, specialized microorganisms (dechlorinators) can reduce these chlorinated ethenes to ethene, an innocuous product, and gain energy for growth by a process known as reductive dechlorination. Dechlorinators are most often present in the environment and in dechlorinating cultures alongside other microbes such as fermenters, methanogens, and acetogens. Fermenters, methanogens, and acetogens syntrophically provide essential nutrients and growth factors to dechlorinators, most specifically to the only members able to reduce TCE all the way to ethene: Dehalococcoides; unfortunately, they also compete with dechlorinators for electron donors. My laboratory devises reductive chlorination platforms to study competition and syntrophy among Dehalococcoides, and other microbes to optimize remediation reactions and transport in the subsurface. We look at competing processes present as part of the natural soil chemistry and microbiology and address these challenges through a combination of enrichment techniques, molecular microbial ecology (deep sequencing), water chemistry, and electron balances. We have applied knowledge gathered in my laboratory to: 1) enrich microbial dechlorinating cultures capable of some of the fastest rates of TCE to ethene dechlorination ever reported, and 2) successfully design and operate three different continuous dechlorinating reactor types. We attribute our successful reactor operations to our multidisciplinary approach which links microbiology and engineering. Our reactors produce robust dechlorinating cultures used for in-situ bioaugmentation of PCE and TCE at contaminated sites

  1. The PACSAT Communications Experiment (PCE)

    SciTech Connect

    Not Available

    1993-02-12

    While VITA (Volunteers in Technical Assistance) is the recognized world leader in low earth orbiting (LEO) satellite technology (below 1 GHz), its involvement in communications technologies is to facilitate renewable energy technology transfer to developing countries. A communications payload was incorporated into the UoSat 2 satellite (Surrey Univ., UK), launched in 1984; a prototype satellite (PCE) was also launched Jan 1990. US DOE awarded a second grant to VITA to design and test the prototype ground stations (command and field), install field ground stations in several developing country sites, pursue the operational licensing process, and transfer the evaluation results to the design of an operating system. This report covers the principal tasks of this grant.

  2. 40 CFR 63.471 - Facility-wide standards.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... total emissions of perchloroethylene (PCE), trichloroethylene (TCE) and methylene chloride (MC) used at... TCE only 14,100 23,500 MC only 60,000 100,000 Multiple solvents—Calculate the MC-weighted emissions..., the facility emissions of PCE and TCE are weighted according to their carcinogenic potency relative...

  3. 40 CFR 63.471 - Facility-wide standards.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... total emissions of perchloroethylene (PCE), trichloroethylene (TCE) and methylene chloride (MC) used at... TCE only 14,100 23,500 MC only 60,000 100,000 Multiple solvents—Calculate the MC-weighted emissions..., the facility emissions of PCE and TCE are weighted according to their carcinogenic potency relative...

  4. 40 CFR 63.471 - Facility-wide standards.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... total emissions of perchloroethylene (PCE), trichloroethylene (TCE) and methylene chloride (MC) used at... TCE only 14,100 23,500 MC only 60,000 100,000 Multiple solvents—Calculate the MC-weighted emissions..., the facility emissions of PCE and TCE are weighted according to their carcinogenic potency relative...

  5. 40 CFR 63.471 - Facility-wide standards.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... total emissions of perchloroethylene (PCE), trichloroethylene (TCE) and methylene chloride (MC) used at... TCE only 14,100 23,500 MC only 60,000 100,000 Multiple solvents—Calculate the MC-weighted emissions..., the facility emissions of PCE and TCE are weighted according to their carcinogenic potency relative...

  6. A study of the effect of perchloroethylene exposure on semen quality in dry cleaning workers

    SciTech Connect

    Eskenazi, B.; Wyrobek, A.J.; Fenster, L.; Katz, D.F.; Sadler, M.; Lee, J.; Hudes, M.; Rempel, D.M. )

    1991-01-01

    The purpose of this investigation was to determine the effects of perchloroethylene (PCE) exposure on human semen quality. We compared the semen quality of 34 dry cleaners with that of 48 laundry workers. We examined the relationships of 17 semen parameters to expired air levels of PCE and to an index of exposure based on job tasks in the last three months. The average sperm concentration was over 80 million for both dry cleaners and laundry workers, but approximately one-quarter of each group was oligospermic. The overall percentage of abnormal forms was similar for the two groups; however, sperm of dry cleaners were significantly more likely to be round (t = -3.29, p = 0.002) and less likely to be narrow (t = 2.35, p = 0.02) than the sperm of laundry workers. These effects were dose-related to expired air levels and to the exposure index after controlling for potential confounders (e.g., heat exposure). The average percent motile sperm for both groups was slightly over 60%; however, sperm of dry cleaners tended to swim with greater amplitude of lateral head displacement (ALH) than those of laundry workers (t = -1.73, p = 0.09), and level of PCE in expired air was a significant predictor of ALH in the multiple regression model (t = 2.00, p = 0.05). In addition, exposure index was a significant negative predictor of the sperm linearity parameter (t = -2.57, p = 0.01). These results suggest that occupational exposures to PCE can have subtle effects on sperm quality. Additional analyses are required to determine whether these effects are associated with changes in fertility.

  7. TRICHLOROETHYLENE (TCE) ISSUE PAPERS

    EPA Science Inventory

    These issue papers are a part of EPA's effort to develop a trichloroethylene (TCE) human health risk assessment. These issue papers were developed by EPA to provide scientific and technical information to the National Academy of Sciences (NAS) for use in developing their advice ...

  8. HORIZONTAL LASAGNA TO BIOREMEDIATE TCE

    EPA Science Inventory

    Removal of TCE from these tight clay soils has been technically difficult and expensive. However, the LASAGNATM technique allows movement of the TCE into treatment zones for biodegradation or dechlorination in place, lessening the costs and exposure to TCE. Electroosmosis was c...

  9. Chlorine isotope effects from isotope ratio mass spectrometry suggest intramolecular C-Cl bond competition in trichloroethene (TCE) reductive dehalogenation.

    PubMed

    Cretnik, Stefan; Bernstein, Anat; Shouakar-Stash, Orfan; Löffler, Frank; Elsner, Martin

    2014-01-01

    Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms. PMID:24853618

  10. FTIR quantification of industrial hydraulic fluids in perchloroethylene

    NASA Technical Reports Server (NTRS)

    Mehta, Narinder K.

    1993-01-01

    The purpose of this summer research project was to investigate whether perchloroethylene can be used as a solvent for the quantitative analysis of industrial hydraulic fluids by infrared spectroscopy employing Beer's law. Standard calibration curves using carbon-hydrogen stretching (generic) and ester absorption peaks were prepared for a series of standard dilutions at low ppm levels of concentration of seven hydraulic fluids in perchloroethylene. The absorbance spectras were recorded with 1.5-10 mm fixed and variable path length sample cells made of potassium bromide. The results indicate that using ester infrared spectral peak, it is possible to detect about 20 ppm of the hydraulic fluid in perchloroethylene.

  11. A convenient method for the quantitative determination of elemental sulfur in coal by HPLC analysis of perchloroethylene extracts

    USGS Publications Warehouse

    Buchanan, D.H.; Coombs, K.J.; Murphy, P.M.; Chaven, C.

    1993-01-01

    A convenient method for the quantitative determination of elemental sulfur in coal is described. Elemental sulfur is extracted from the coal with hot perchloroethylene (PCE) (tetrachloroethene, C2Cl4) and quantitatively determined by HPLC analysis on a C18 reverse-phase column using UV detection. Calibration solutions were prepared from sublimed sulfur. Results of quantitative HPLC analyses agreed with those of a chemical/spectroscopic analysis. The HPLC method was found to be linear over the concentration range of 6 ?? 10-4 to 2 ?? 10-2 g/L. The lower detection limit was 4 ?? 10-4 g/L, which for a coal sample of 20 g is equivalent to 0.0006% by weight of coal. Since elemental sulfur is known to react slowly with hydrocarbons at the temperature of boiling PCE, standard solutions of sulfur in PCE were heated with coals from the Argonne Premium Coal Sample program. Pseudo-first-order uptake of sulfur by the coals was observed over several weeks of heating. For the Illinois No. 6 premium coal, the rate constant for sulfur uptake was 9.7 ?? 10-7 s-1, too small for retrograde reactions between solubilized sulfur and coal to cause a significant loss in elemental sulfur isolated during the analytical extraction. No elemental sulfur was produced when the following pure compounds were heated to reflux in PCE for up to 1 week: benzyl sulfide, octyl sulfide, thiane, thiophene, benzothiophene, dibenzothiophene, sulfuric acid, or ferrous sulfate. A sluury of mineral pyrite in PCE contained elemental sulfur which increased in concentration with heating time. ?? 1993 American Chemical Society.

  12. Effect of dechlorinating bacteria on the longevity and composition of PCE-containing nonaqueous phase liquids under equilibrium dissolution conditions

    SciTech Connect

    Carr, C.S.; Garg, S.; Hughes, J.B.

    2000-03-15

    The influence of dechlorinating microorganisms on PCE and its reduced end products in the presence of a PCE-containing nonaqueous phase liquid (NAPL) was investigated. Experiments were conducted in continuous-flow stirred-tank reactors (CFSTRs) containing a mixed PCE dechlorinating culture and a model NAPL consisting of PCE and tridecane. Comparisons between biotic and abiotic CFSTRs demonstrated that dechlorination resulted in a factor of 14 increase in PCE removal rates from the NAPL. The formation of dechlorination daughter products trichloroethene and cis-dichloroethene were observed, and cis-dichloroethene was not dechlorinated further. Partitioning of daughter products between phases caused temporal changes in the chlorinated ethenes distribution within the NAPL. The combined effects of dissolution and dechlorination on the removal of chlorinated ethenes from the NAPL were described using a mathematical model that approximated dechlorination as a pseudo-first-order process. Pseudo-first-order dechlorination rate coefficients for PCE and TCE were determined and were 0.18 and 0.27 h{sup {minus}1}, respectively. It was determined that total chlorinated ethenes removal from the NAPL would be achieved in 13 days in biotic CFSTRs, as compared to 77 days in the abiotic CFSTRs--corresponding to an 83% reduction in longevity of the chlorinated ethenes component of the NAPL.

  13. Superfund Record of Decision (EPA Region 7): Des Moines TCE, Des Moines, Polk County, Iowa, July 1986. Final report

    SciTech Connect

    Not Available

    1986-07-21

    The Des Moines TCE site includes the underground infiltration gallery used by the Des Moines Water Works (DMWW) as a source of the public water supply. The site was discovered in 1984 after trichloroethylene (TCE) was detected in the city's public water supply. The Dico Company disposed of an unknown quantity of oily waste sludge containing TCE onto their parking lot for dust control and into a drainage ditch on their property. The primary contaminants of concern include: TCE, PCE, 1,2-dichloroethane, vinyl chloride. The selected remedial action for this site includes: extraction wells to collect the contaminated ground water; isolation of the northern-most section of the north gallery; treatment of the ground water through air stripping to remove 96% of the TCE; discharge of the treated water to the Raccoon River; operation of the west extraction wells until established effluent levels are achieved for four consecutive months.

  14. Tetrachloroethene Dehalorespiration and Growth of Desulfitobacterium frappieri TCE1 in Strict Dependence on the Activity of Desulfovibrio fructosivorans

    PubMed Central

    Drzyzga, Oliver; Gottschal, Jan C.

    2002-01-01

    Tetrachloroethene (PCE) dehalorespiration was investigated in a continuous coculture of the sulfate-reducing bacterium Desulfovibrio fructosivorans and the dehalorespiring Desulfitobacterium frappieri TCE1 at different sulfate concentrations and in the absence of sulfate. Fructose (2.5 mM) was the single electron donor, which could be used only by the sulfate reducer. With 2.5 mM sulfate, the dehalogenating strain was outnumbered by the sulfate-reducing bacterium, sulfate reduction was the dominating process, and only trace amounts of PCE were dehalogenated by strain TCE1. With 1 mM sulfate in the medium, complete sulfate reduction and complete PCE dehalogenation to cis-dichloroethene (cis-DCE) occurred. In the absence of sulfate, PCE was also completely dehalogenated to cis-DCE, and the population size of strain TCE1 increased significantly. The results presented here describe for the first time dehalogenation of PCE by a dehalorespiring anaerobe in strict dependence on the activity of a sulfate-reducing bacterium with a substrate that is exclusively used by the sulfate reducer. This interaction was studied under strictly controlled and quantifiable conditions in continuous culture and shown to depend on interspecies hydrogen transfer under sulfate-depleted conditions. Interspecies hydrogen transfer was demonstrated by direct H2 measurements of the gas phase and by the production of methane after the addition of a third organism, Methanobacterium formicicum. PMID:11823202

  15. Combined C and Cl isotope effects indicate differences between corrinoids and enzyme (Sulfurospirillum multivorans PceA) in reductive dehalogenation of tetrachloroethene, but not trichloroethene.

    PubMed

    Renpenning, Julian; Keller, Sebastian; Cretnik, Stefan; Shouakar-Stash, Orfan; Elsner, Martin; Schubert, Torsten; Nijenhuis, Ivonne

    2014-10-21

    The role of the corrinoid cofactor in reductive dehalogenation catalysis by tetrachloroethene reductive dehalogenase (PceA) of Sulfurospirillum multivorans was investigated using isotope analysis of carbon and chlorine. Crude extracts containing PceA--harboring either a native norpseudo-B12 or the alternative nor-B12 cofactor--were applied for dehalogenation of tetrachloroethene (PCE) or trichloroethene (TCE), and compared to abiotic dehalogenation with the respective purified corrinoids (norpseudovitamin B12 and norvitamin B12), as well as several commercially available cobalamins and cobinamide. Dehalogenation of TCE resulted in a similar extent of C and Cl isotope fractionation, and in similar dual-element isotope slopes (εC/εCl) of 5.0-5.3 for PceA enzyme and 3.7-4.5 for the corrinoids. Both observations support an identical reaction mechanism. For PCE, in contrast, observed C and Cl isotope fractionation was smaller in enzymatic dehalogenation, and dual-element isotope slopes (2.2-2.8) were distinctly different compared to dehalogenation mediated by corrinoids (4.6-7.0). Remarkably, εC/εCl of PCE depended in addition on the corrinoid type: εC/εCl values of 4.6 and 5.0 for vitamin B12 and norvitamin B12 were significantly different compared to values of 6.9 and 7.0 for norpseudovitamin B12 and dicyanocobinamide. Our results therefore suggest mechanistic and/or kinetic differences in catalytic PCE dehalogenation by enzymes and different corrinoids, whereas such differences were not observed for TCE. PMID:25216120

  16. Enhanced reduction of chromate and PCE by pelletized surfactant-modified zeolite/zerovalent iron

    SciTech Connect

    Li, Z.; Jones, H.K.; Bowman, R.S.; Helferich, R.

    1999-12-01

    The current research focuses on enhanced removal of chromate and perchloroethylene from contaminated water by a combination of a reduction material (represented by zerovalent iron, ZVI) and a sorption material (represented by surfactant-modified zeolite, SMZ). Natural zeolite and ZVI were homogenized and pelletized to maintain favorable hydraulic properties while minimizing material segregation due to bulk density differences. The zeolite/ZVI pellets were modified with the cationic surfactant hexadecyltrimethylammonium bromide to increase contaminant sorption and, thus, the contaminant concentration on the solid surface. Results of chromate sorption/reduction indicate that the chromate sorption capacity of pelletized SMZ/ZVI is at least 1 order of magnitude higher than that of zeolite/ZVI pellets. Compared to SMZ pellets, the chromate removal capacity of SMZ/ZVI pellets in a 24-h period is about 80% higher, due to the combined effects o sorption by SMZ and reduction by ZVI. The chromate and PCE degradation rates with and without surfactant modification were determined separately. The pseudo-first-order reduction constant increased by a factor of 3 for PCE and by a factor of 9 for chromate following surfactant modification. The enhanced contaminant reduction capacity of SMZ/ZVI pellets may lead to a decrease in the amount of material required to achieve a given level of contaminant removal.

  17. PHASE-TRANSFER-CATALYST APPLIED TO THE OXIDATION OF TRICHLOROETHYLENE BY POTASSIUM PERMANGANATE

    EPA Science Inventory

    Chlorinated ethylenes such as trichloroethylene (TCE) and perchloroethylene (PCE) are common contaminants (Plumb 1991; Westrick et al., 1984). They opccur in the subsurface as zones of residual saturation or occasionally as free products. Because of their inherently low solubil...

  18. TEMPERATURE DEPENDENCE OF THE EMISSION OF PERCHLOROETHYLENE FROM DRY CLEANED FABRICS

    EPA Science Inventory

    The article discusses an evaluation of the emission of perchloroethylene (tetrachloroethylene) from freshly dry cleaned fabrics using small environment test chambers. he temperature dependence of the release of perchloroethylene was evaluated over a temperature range of 20 to 45 ...

  19. TCE treatment pasta-bilities.

    PubMed Central

    Holton, W C

    1999-01-01

    Monsanto's "Lasagna" process uses layers of treatment zones spaced between buried electrodes to remove trichloroethylene (TCE) from contaminated soil and groundwater. TCE is used primarily as a metal degreaser as well as in products such as dyes, printing ink, and paint. TCE can eventually make its way into the environment and is prevalent in the water and soil of industrialized nations. Although TCE breaks down in a few days when released into the atmosphere, it degrades much more slowly in soil, taking months or years. Moreover, it is often broken down by microbes into toxic substances such as vinylidene chloride (a suspected human carcinogen) and vinyl chloride (a known human carcinogen). The Lasagna process is based on the principle of electro-osmosis, in which an electric current draws water from low--permeability soils such as clays, silts, and fine sands. To remove TCE from contaminated soils, Monsanto scientists added layers of filtering media, which attack the contaminant as it is pulled from electrode to electrode. The technology has been tested at the Paducah Gaseous Diffusion Plant in western Kentucky, where it removed over 98% of TCE from contaminated soil. PMID:10464086

  20. TCE treatment pasta-bilities.

    PubMed

    Holton, W C

    1999-09-01

    Monsanto's "Lasagna" process uses layers of treatment zones spaced between buried electrodes to remove trichloroethylene (TCE) from contaminated soil and groundwater. TCE is used primarily as a metal degreaser as well as in products such as dyes, printing ink, and paint. TCE can eventually make its way into the environment and is prevalent in the water and soil of industrialized nations. Although TCE breaks down in a few days when released into the atmosphere, it degrades much more slowly in soil, taking months or years. Moreover, it is often broken down by microbes into toxic substances such as vinylidene chloride (a suspected human carcinogen) and vinyl chloride (a known human carcinogen). The Lasagna process is based on the principle of electro-osmosis, in which an electric current draws water from low--permeability soils such as clays, silts, and fine sands. To remove TCE from contaminated soils, Monsanto scientists added layers of filtering media, which attack the contaminant as it is pulled from electrode to electrode. The technology has been tested at the Paducah Gaseous Diffusion Plant in western Kentucky, where it removed over 98% of TCE from contaminated soil. PMID:10464086

  1. Urban/industrial pollution for the New York City-Washington, D. C., corridor, 1996-1998: 1. Providing independent verification of CO and PCE emissions inventories

    NASA Astrophysics Data System (ADS)

    Barnes, Diana H.; Wofsy, Steven C.; Fehlau, Brian P.; Gottlieb, Elaine W.; Elkins, James W.; Dutton, Geoffrey S.; Montzka, Stephen A.

    2003-03-01

    Atmospheric mixing ratios of carbon monoxide (CO) and perchloroethylene (PCE, C2Cl4) were measured above the canopy at Harvard forest, MA every half-hour for 3 years starting in January 1996. Pollution enhancements are strongly correlated with winds from the southwest, the direction of the New York City-Washington, D. C., corridor, as compared to background levels observed during northwest winds traveling from Canada. We establish the ratio of CO to PCE pollution enhancements by wind direction, by season, and by year and use these results to test the quality of county-level and national source emission inventories for these two gases. The EPA carbon monoxide emission county-level inventories and the McCulloch and Midgley sales-based national-level PCE release estimates are found to be in accord with our independent observations of urban/industrial releases. For the New York City-Washington, D. C., corridor the inventory-based COI/PCEI emissions ratio of 584 (kg/kg) for 1996 falls well within the range of observationally-based ΔCO/ΔPCE pollution plume ratios of 388 to 706 (kg/kg) and is only 11% higher than the observed mean of 521 ± 90 (kg/kg). On the basis of this agreement, PCE emission estimates for 1997 and 1998 are derived from the CO inventory emissions values and the observed ΔCO/ΔPCE ratios in pollution plumes for those years; despite the call for voluntary cutbacks, urban/industrial emissions of PCE appear to be on the rise.

  2. INHIBITORY EFFECTS OF PERCHLOROETHYLENE ON HUMAN NEURONAL NICOTINIC ACETYLCHOLINE RECEPTORS.

    EPA Science Inventory

    Perchloroethylene (PERC) is a volatile organic solvent with a variety of industrial uses. PERC exposure has been shown to cause adverse neurological effects including deficits in vision and memory in exposed individuals. Despite knowledge of these effects, the mechanisms by whi...

  3. IRIS TOXICOLOGICAL REVIEW OF TETRACHLOROETHYLENE (PERCHLOROETHYLENE) (INTERAGENCY SCIENCE DISCUSSION DRAFT)

    EPA Science Inventory

    EPA is releasing the draft report, Toxicological Review of Tetrachloroethylene (Perchloroethylene), that was distributed to Federal agencies and White House Offices for comment during the Science Discussion step of the IRIS Assessment...

  4. HORIZONTAL LASAGNA^TM TO BIOREMEDIATE TCE

    EPA Science Inventory

    Removal of TCE from these tight clay soils has been technically difficult and expensive. However, the LASAGNA technique allows movement of the TCE into treatment zones for biodegradation or dechlorination in place, lessening the costs and exposure to TCE.

    Electroosmosis wa...

  5. Simulating Metabolic Reductive Decholorination with Multiple Cultures during Bioenhanced PCE-NAPL Dissolution

    NASA Astrophysics Data System (ADS)

    Chen, M.; Abriola, L.; Christ, J.; Amos, B. K.; Suchomel, E. J.; Pennell, K. D.; Loeffler, F.

    2009-12-01

    A recently conducted laboratory experiment investigating metabolic reductive dechlorination in dense non-aqueous phase liquid (DNAPL) source zones demonstrated enhanced DNAPL dissolution by increasing the driving force for mass transfer due to reductions in the aqueous phase. Tetrachloroethene (PCE) was degraded sequentially to cis-1,2-dichloroethene (cis-DCE) through trichloroethylene (TCE) and to ethene via vinyl chloride (VC) by Geobacter and Dehalococcoides, respectively. Significant PCE dechlorination led to bioenhanced DNAPL dissolution, with a 5-fold increase in dissolution observed relative to an abiotic system. A multiphase, compositional simulator, the Michigan Subsurface Environmental Simulator (MISER), was modified to model 9 chemical constituents and 3 microbial populations (a fermentor and two dechlorinators) within the column. Monod kinetics, including electron donor thresholds, electron acceptor competition, and competitive inhibition, were used to model contaminant dechlorination and biomass growth. The model was calibrated to the experimental data using effluent concentrations. Model results were compared to analyses of side port samples collected along the column length to determine the ability of the model to reproduce the biomass growth and reductive dechlorination occurring within the column. Results suggest that the model as formulated is capable of capturing the general trends observed in the column. Work is on-going to investigate the influence of initial biomass distribution, DNAPL source zone distribution, and applied boundary conditions on bioenhanced dissolution predictions. This model is expected to provide valuable insights for future experimental design and identification of conditions that may govern bioenhanced dissolution in the field.

  6. Application of solid phase microextraction and needle trap device with silica composite of carbon nanotubes for determination of perchloroethylene in laboratory and field.

    PubMed

    Heidari, Mahmoud; Attari, Seyed Ghavameddin; Rafieiemam, Maryam

    2016-04-28

    In this paper solid phase microextraction (SPME) and needle trap device (NTD) as two in-progress air monitoring techniques was applied with silylated composite of carbon nanotubes for sampling and analysis of perchloroethylene in air. Application of SPME and NTD with proposed nano-structured sorbent was investigated under different laboratory and experimental parameters and compared to the SPME and NTD with CAR/PDMS. Finally the two samplers contained nano-sorbent used as a field sampler for sampling and analysis of perchloroethylene in dry cleaning. Results revealed that silica composite form of CNTs showed better performance for adsorbent of perchloroethylene. SPME and NTD with proposed sorbent was demonstrated better responses in lower levels of temperature and relative humidity. For 5 days from sampling the relative responses were more than 97% and 94% for NTD and SPME, respectively. LOD were 0.023 and 0.014 ng mL(-1) for SPME coated CNTs/SC and CAR/PDMS, and 0.014 and 0.011 ng mL(-1) for NTD packed with CNTs/SC and CAR/PDMS, respectively. And for consecutive analysis RSD were 3.9-6.7% in laboratory and 4.43-6.4% in the field. In the field study, NTD was successfully applied for determining of the PCE in dry cleaning. The results show that the NTD packed with nanomaterial is a reliable and effective approach for the sampling and analysis of volatile compounds in air. PMID:27046209

  7. Potential of the TCE-degrading endophyte Pseudomonas putida W619-TCE to improve plant growth and reduce TCE phytotoxicity and evapotranspiration in poplar cuttings

    SciTech Connect

    Weyens, N.; van der Lelie, D.; Truyens, S.; Dupae, J.; Newman, L.; Taghavi, S.; Carleer, R.; Vangronsveld, J.

    2010-09-01

    The TCE-degrading poplar endophyte Pseudomonas putida W619-TCE was inoculated in poplar cuttings, exposed to 0, 200 and 400 mg l{sup -1} TCE, that were grown in two different experimental setups. During a short-term experiment, plants were grown hydroponically in half strength Hoagland nutrient solution and exposed to TCE for 3 days. Inoculation with P. putida W619-TCE promoted plant growth, reduced TCE phytotoxicity and reduced the amount of TCE present in the leaves. During a mid-term experiment, plants were grown in potting soil and exposed to TCE for 3 weeks. Here, inoculation with P. putida W619-TCE had a less pronounced positive effect on plant growth and TCE phytotoxicity, but resulted in strongly reduced amounts of TCE in leaves and roots of plants exposed to 400 mg l{sup -1} TCE, accompanied by a lowered evapotranspiration of TCE. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), which are known intermediates of TCE degradation, were not detected. The endophyte P. putida W619-TCE degrades TCE during its transport through the xylem, leading to reduced TCE concentrations in poplar, and decreased TCE evapotranspiration.

  8. A Continuous Flow Column Study of Anaerobic PCE Transformation With the Evanite Culture and Hanford Aquifer Solids

    NASA Astrophysics Data System (ADS)

    Semprini, L.; Behrens, S.; Azizian, M.; Sabalowsky, A.; Dolan, M.; Ruiz-Hass, P.; Ingle, J.; Spormann, A.

    2005-12-01

    Anaerobic reductive dehalogenation of tetrachloroethene (PCE) and trichoroethene (TCE) is a promising technology for the in situ treatment of high concentration source zones in contaminated aquifers. Continuous flow column studies were performed where a mixed dehalogenating culture (Evanite culture) that contains Dehalococcides-like microorganisms was bioaugmented into aquifer solids from the Hanford DOE site. Studies conducted prior to bioaugmentation showed PCE transport was retarded due to sorption onto the aquifer solids. Upon bioaugmentation and with continuous lactate addition, PCE (10 mg/L) was transformed to cis-dichloroethene ( cis-DCE), and enhanced transformation of sorbed PCE was observed. Prolonged production of cis-DCE was associated with iron reducing conditions, while eventual vinyl chloride (VC) reduction to ethene was associated with sulfate reducing conditions. Microbial processes included lactate fermentation to acetate and propionate, iron reduction, sulfate reduction, and reductive dehalogenation, with reductive dehalogenation utilizing 2 to 3% of the electron donor addition. PCE was completely transformed to ethene within a hydraulic residence time of one day. Upon competition of the column tests spatial samples of aquifer solids were analyzed using molecular methods and solids were used in batch microcosm activity tests. Dehalococcoides sp. 16S rRNA gene copy numbers dropped from ~ 74% of total Eubacterial 16S rRNA genes in the original inoculum, to about 0.5 to 4% through out the column, consistent with the estimates of electron donor utilization for dehalogenation reactions. Microcosm tests showed most of PCE transformation activity at the entrance of the column, consistent with the Dehalococcoides sp. 16S rRNA gene copy numbers being highest in that area. Roughly 20% of the Dehalococcoides sp. population in the column possessed a vcrA gene for the respiration of VC to ethene. The vcrA-positive subpopulation decreases to about 5% towards

  9. Modeling perchloroethylene degradation under ultrasonic irradiation and photochemical oxidation in aqueous solution

    PubMed Central

    2012-01-01

    Sonolysis and photochemical degradation of different compounds such as chlorinated aliphatic hydrocarbons are among the recent advanced oxidation processes. Perchloroethylene is one of these compounds that has been mainly used as a solvent and degreaser. In this work, elimination of perchloroethylene in aqueous solution by ultrasonic irradiation, andphotochemical oxidation by ultra violet ray and hydrogen peroxide were investigated. Three different initial concentrations of perchloroethylene at different pH values, detention periods, and concentrations of hydrogen peroxide were investigated. Head space gas chromatography with FID detector was used for analyses of perchloroethylene. This research was performed in 9 months from April through December 2011. Results showed that perchloroethylene could be effectively and rapidly degraded by ultrasonic irradiation, photochemical oxidation by ultra violet ray, hydrogen peroxide and a combination of these methods. Kinetics of perchloroethylene was strongly influenced by time, initial concentration and pH value. Degradation of Perchloroethylene increased with decrease in the initial concentration of perchloroethylene from 0.3 to 10 mg/L at all initial pH. The results showed an optimum degradation condition achieved at pH = 5 but did not affect significantly the perchloroethylene destruction in the various pH values. Kinetic modeling applied for the obtained results showed that the degradation of perchloroethylene by ultrasound and photo-oxidation followed first order and second order model. The percentage of removal in the hybrids reactor was higher than each of the reactors alone, the reason being the role of hydroxyl radical induced by ultrasound and photochemical reaction. PMID:23369271

  10. Selection of trichloroethene (TCE) degrading bacteria that resist inactivation by TCE.

    PubMed

    Ewers, J; Freier-Schröder, D; Knackmuss, H J

    1990-01-01

    Two isoprene (2-methyl-1,3-butadiene) utilizing bacteria, Alcaligenes denitrificans ssp. xylosoxidans JE 75 and Rhodococcus erythropolis JE 77, were identified as highly efficient cooxidizers of TCE, cis- and trans-dichloroethene, 1,1-dichloroethene and vinyl-chloride. Isoprene grown cells eliminate chloride from TCE in stoichiometric amounts and tolerate high concentrations of TCE. PMID:2244792

  11. Sulfur cement production using by products of the perchloroethylene coal cleaning process and the FC4-1 cleaned soil

    SciTech Connect

    Bassam Masri, K.L.; Fullerton, S.L.

    1995-12-31

    An introductory set of experiments to show the feasibility of making sulfur cement were carried out at the University of Akron according to Parrett and Currett`s patent which requires the use of sulfur, a filler, a plasticizer, and a vulcanization accelerator. Small blocks of cement were made using byproducts of the perchloroethylene coal cleaning process. Extracted elemental and organic sulfur, ash and mineral matters from the float sink portion of the PCE process, and FC4-1 cleaned soil were used as substitutes for sulfur and filler needed for the production of sulfur cement. Leaching tests in different solutions and under different conditions were conducted on the sulfur blocks. Other tests such as strength, durability, resistance to high or low temperatures will be conducted in the future. Sulfur cement can be used as a sealing agent at a joint, roofing purposes, forming ornamental figures, and coating of exposed surfaces of iron or steel. When mixed with an aggregate, sulfur concrete is formed. This concrete can be used for structural members, curbings, guthers, slabs, and can be precast or cast at the job site. An advantage of sulfur cement over Portland cement is that it reaches its design strength in two to three hours after processing and it can be remelted and recast.

  12. Influence of sediment reduction on TCE degradation

    SciTech Connect

    Szecsody, James E.; Williams, Mark D.; Fruchter, Jonathan S.; Vermeul, Vincent R.; Evans, J. C.; Sklarew, Deborah S.

    2000-12-01

    A field-scale remediation technique for TCE and chromate is currently being implemented which uses a chemical treatment to reduce existing iron(III) in sediments. While reduction of some contaminants is well established, TCE data show that dechlorination is more complex, and the role of iron oxides to catalyze the reaction is not well understood. The purpose of this laboratory-scale study was to investigate the influence of temperature and partial sediment reduction on TCE dechlorination. Fully reduced sediments can degrade TCE at sufficiently fast rates (1.2 to 19 h) during static and transport experiments over 2oC to 25oC that a successful barrier could be made at the field scale. In contrast, partially reduced sediment resulted in up to a 3 order of magnitude decrease in the TCE dechlorination rate. While minimally reduced sediment had nearly no TCE reactivity, > 40% reduced sediment had considerably faster dechlorination rates. The second-order dependence of the TCE dechlorination rate on the fraction of reduced iron demonstrates the significant role of the iron oxide surface (as a catalyst or for surface coordination) for TCE dechlorination. Based on these results, the field-scale reduction was designed with specific reagent concen-trations, temperature, and flow rates to efficiently create a reductive barrier.

  13. REMEDIATION OF SITES CONTAMINATED WITH TCE

    EPA Science Inventory

    Widespread use of trichloroethylene (TCE) in the U.S. has resulted in its frequent detection in soil and groundwater. TCE can become a health hazard after being processed in the human liver; or reductive dehalogenation in the environment may result in production of vinyl chloride...

  14. BIODEGRADATION OF PCE AND TCE IN LANDFILL, LEACHATE PREDICTED FROM CONCENTRATIONS OF MOLECULAR HYDROGEN: A CASE STUDY

    EPA Science Inventory

    The Refuse Hideaway Landfill (23-acre) was designed as a "natural attenuation" landfill and no provision was made to collect and treat contaminated water. Natural biological degradation through sequential reductive dechlorination had been an important mechanism for natural atten...

  15. Potential of the TCE-degrading endophyte Pseudomonas putida W619-TCE to improve plant growth and reduce TCE phytotoxicity and evapotranspiration in poplar cuttings.

    PubMed

    Weyens, Nele; Truyens, Sascha; Dupae, Joke; Newman, Lee; Taghavi, Safiyh; van der Lelie, Daniel; Carleer, Robert; Vangronsveld, Jaco

    2010-09-01

    The TCE-degrading poplar endophyte Pseudomonas putida W619-TCE was inoculated in poplar cuttings, exposed to 0, 200 and 400 mg l(-1) TCE, that were grown in two different experimental setups. During a short-term experiment, plants were grown hydroponically in half strength Hoagland nutrient solution and exposed to TCE for 3 days. Inoculation with P. putida W619-TCE promoted plant growth, reduced TCE phytotoxicity and reduced the amount of TCE present in the leaves. During a mid-term experiment, plants were grown in potting soil and exposed to TCE for 3 weeks. Here, inoculation with P. putida W619-TCE had a less pronounced positive effect on plant growth and TCE phytotoxicity, but resulted in strongly reduced amounts of TCE in leaves and roots of plants exposed to 400 mg l(-1) TCE, accompanied by a lowered evapotranspiration of TCE. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), which are known intermediates of TCE degradation, were not detected. PMID:20598789

  16. Superfund Record of Decision (EPA Region 3): Croyden TCE Spill, PA. (First Remedial Action), December 1988

    SciTech Connect

    Not Available

    1988-12-28

    The Croyden TCE Spill site is located in Bristol Township, Buck County, Pennsylvania. VOC contamination in the ground water was detected over a 3.5-square mile area, predominantly residential, with an estimated 3,000 residents. The study area is bordered on the south by the Delaware River. Neshaminy Creek, which borders the study area to the west, and Hog Run Creek which flows through the focused area of investigation, both discharge to the river. Although the source of contamination has not been identified, the contaminant plume appears to be flowing south-southeast into the East Branch of Hog Run Creek and probably into the Delaware River. The primary contaminants of concern affecting the ground water are TCE and PCE. The selected remedial action for the site includes connecting approximately 13 residences to the public water supply system via the construction of new water services lines, mains, hydrants, and valves; and ground water monitoring to ensure that homes located outside of the TCE-contaminated zone will not be at risk from the migrating plume.

  17. Phytoremediation of trichloroethene (TCE) using cottonwood trees

    USGS Publications Warehouse

    Jones, S.A.; Lee, R.W.; Kuniansky, E.L.

    1999-01-01

    The ability of cottonwood trees for phytoremediation was studied on aerobic shallow groundwater containing TCE. Cottonwood trees were planted over a 0.2-ha area at the Naval Air Station at Fort Worth, TX, in April 1996. Two years later, groundwater chemistry in the terrace alluvial aquifer was changing locally. Dissolved oxygen (DO) concentrations declined at the southern end of the whip plantings while total iron concentration increased. Groundwater chemistry near a mature cottonwood tree ~ 60 m from the caliper trees was different from that observed elsewhere. Anaerobic conditions near the mature cottonwood tree were evident. Reductive dechlorination of TCE occurred in the aquifer near the mature tree, as demonstrated by very small concentration of TCE in groundwater, a small median ratio of TCE to the degradation product cis-1,2-DCE and the presence of vinyl chloride.

  18. Monitoring Anaerobic TCE Degradation by Evanite Cultre in Column Packed with TCE-Contaminated Soil

    NASA Astrophysics Data System (ADS)

    Ko, J.; Han, K.; Ahn, G.; Park, S.; Kim, N.; Ahn, H.; Kim, Y.

    2011-12-01

    Trichloroethylene (TCE) is a long-term common groundwater pollutant because the compound with high density is slowly released into groundwater. Physical and chemical remediation processes have been used to clean-up the contaminant, but novel remediation technology is required to overcome a low efficiency of the traditional treatment process. Many researchers focused on biological process using an anaerobic TCE degrading culture, dehalococcoides spp., but it still needs to evaluate whether the process can be applied into field scale under aerobic condition. Therefore, in this work we examined two different types (i.e., Natural attenuation and bioaugmentation) of biological remediation process in anaerobic column packed with TCE-contaminated soil. A TCE degradation by indigenous microorganisms was confirmed by monitoring TCE and the metabolites (c-DCE, VC, ETH). However, TCE was transformed and stoichiometry amount of c-DCE was produced, and VC and ETH was not detected. To test bioaugmentation of Evanite culture containing dehalococcoides spp., Evanite culture was injected into the column and TCE degradation to c-DCE, VC, ETH was monitored. We are evaluating the transport of the Evanite culture in the column by measuring TCE and VC reductases. In the result, the TCE was completely degraded to ETH using hydrogen as electron donor generate by hydrogen-production fermentation from formate.

  19. Biodegradation of trichloroethylene (TCE) by methanotrophic community.

    PubMed

    Shukla, Awadhesh K; Vishwakarma, Pranjali; Upadhyay, S N; Tripathi, Anil K; Prasana, H C; Dubey, Suresh K

    2009-05-01

    Laboratory incubation experiments were carried out to assess the potential of methanotrophic culture for degrading TCE. Measurements of the growth rate and TCE degradation showed that the methanotrophs not only grew in presence of TCE but also degraded TCE. The rate of TCE degradation was found to be 0.19 ppm h(-1). The reverse transcriptase-PCR test was conducted to quantify expression of pmoA and mmoX genes. RT-PCR revealed expression of pmoA gene only. This observation provides evidence that the pmoA gene was functionally active for pMMO enzyme during the study. The diversity of the methanotrophs involved in TCE degradation was assessed by PCR amplification, cloning, restriction fragment length polymorphism and phylogenetic analysis of pmoA genes. Results suggested the occurrence of nine different phylotypes belonging to Type II methanotrophs in the enriched cultures. Out of the nine, five clustered with, genera Methylocystis and rest got clustered in to a separate group. PMID:19157866

  20. Public health assessment for Malvern Tce Site, Malvern, Chester County, Pennsylvania, Region 3. Cerclis No. PAD014353445. Final report

    SciTech Connect

    Not Available

    1994-01-06

    The Chemclene (Malvern TCE) site is a National Priorities List (NPL) site in Chester County, Pennsylvania, 5.5 miles south of Phoenixville. Over the years, careless waste handling and waste burial have contaminated soil and groundwater with trichloroethene (TCE), 1,1,1-trichloroethane (TCA), and tetrachloroethene (PCE). Based upon the information reviewed, the Pennsylvania Department of Health and the Agency for Toxic Substances and Disease Registry have concluded that this site is a public health hazard because past exposures through the use of contaminated well water were at levels of public health concern. Human exposure to volatile organic compounds (VOCs) may still be occurring through the use of private well water, and the potential for exposure from the nearby public well exists should the contaminant plume reach that well.

  1. Removal of TCE from water with enhanced hybrid aluminas

    SciTech Connect

    Moskovitz, M.; Kepner, B.; Mitchell, M.

    1996-10-01

    TCE is ubiquitous as a hazardous contaminant in ground water which needs to be removed. We have examined the removal of TCE from water with enhanced hybrid aluminas (EHAs) over the range of TCE concentrations: 5 ppb to 50 ppm. Removal efficiencies of 99+% have been achieved. In some cases TCE levels have been reduced to below 0.1 ppb. The capacity and kinetics of EHAs for TCE removal will be discussed. The ultimate fate of the TCE along with the possibility of catalytic destruction of TCE in water EHAs will be discussed. The removal of TCE as a function of the surface area, pore area, and pore diameter will be described. In addition, the results from infrared studies on of the gas phase sorption of TCE with EHAs will be described.

  2. Effect of trichloroethylene (TCE) and toluene concentrations on TCE and toluene biodegradation and the population density of TCE and toluene degraders in soil

    SciTech Connect

    Mu, D.Y.; Scow, K.M.

    1994-07-01

    Toluene is one of several cosubstrates able to support the cometabolism of trichloroethylene (TCE) by soil microbial communities. Indigenous microbial populations in soil degraded TCE in the presence, but not the absence, of toluene after a 60- to 80-h lag period. Initial populations of toluene and TCE degraders ranged from 0.2 x 10{sup 3} to 4 x 10{sup 3} cells per g of soil and increased by more than 4 orders of magnitude after the addition of 20 {mu}g of toluene and 1 {mu}g of TCE per mol of soil solution. The numbers of TCE and toluene degraders and the percent removal of TCE increased with an increase in initial toluene concentration. As the initial TCE concentration was increased from 1 to 20 {mu}g/ml, the numbers of toluene and TCE degraders and the rate of toluene degradation decreased, and no TCE degradation occurred. No toluene or TCE degradation occurred at a TCE concentration of 50 {mu}g/ml. 22 refs., 3 figs., 2 tabs.

  3. Anaerobic dehalogenation of TCE in continuous flow systems

    SciTech Connect

    Singhal, N. |; Jaffe, P.; Maier, W.

    1995-12-31

    This study focuses on the effect of various factors on trichloroethene (TCE) degradation in batch and continuous flow systems, develops mathematical models to describe the dehalogenation of TCE, and provides results of simulations conducted using these models to determine the conditions necessary for maximizing the degradation of TCE. Batch parameters were shown to underpredict substrate and TCE degradation in continuous flow systems. The active biomass concentration had the most significant effect on TCE degradation. TCE degradation may be enhanced in the field by changing the substrate injection pattern to result in a more uniform distribution of the substrate. Gas production under anaerobic conditions needs to be included in any model describing TCE degradation in the field; ignoring this effect can result in gross overpredictions of TCE degradation by the model.

  4. Comparison of pulsed and continuous addition of H2 gas via membranes for stimulating PCE biodegradation in soil columns.

    PubMed

    Ma, Xin; Novak, Paige J; Semmens, Michael J; Clapp, Lee W; Hozalski, Raymond M

    2006-03-01

    Column experiments were performed to investigate a technology for remediating aquifers contaminated with chlorinated solvents. The technology involves installation of hollow-fiber membranes in the subsurface to supply hydrogen gas (H2) to groundwater to support biological reductive dechlorination in situ. Three laboratory-scale columns [control (N2 only), continuous H2, and pulsed H2] were packed with aquifer material from a trichloroethene (TCE)-contaminated wetland in Minnesota and supplied with perchloroethene (PCE)-contaminated synthetic groundwater. The main goals of the research were: (1) evaluate the long-term performance of the H2 supply system and (2) compare the effects of pulsed (4 h on, 20 h off) versus continuous H2 supply (lumen partial pressure approximately 1.2 atm) on PCE dechlorination and production of by-products (i.e. methane and acetate). The silicone-coated fiberglass membranes employed in these experiments were robust, delivering H2 steadily over the entire 349-day experiment. Methane production decreased when H2 was added in a pulsed manner. Nevertheless, the percentage of added H2 used to support methanogenesis was similar in both H2-fed columns (92-93%). For much of the experiment, PCE dechlorination (observed end product = dichloroethene) in the continuous and pulsed H2 columns was comparable, and enhanced in comparison to the natural attenuation observed in the control column. Dechlorination began to decline in the pulsed H2 column after 210 days, however, while dechlorination in the continuous H2 column was sustained. Acetate was detected only in the continuous H2 column, at concentrations of up to 36 microM. The results of this research suggest that in situ stimulation of PCE dechlorination by direct H2 addition requires the continuous application of H2 at high partial pressures, favoring the production of bioavailable organic matter such as acetate to provide a carbon source, electron donor, or both for dechlorinators. Unfortunately

  5. Complex electrical resistance tomography of a subsurface PCE plume

    SciTech Connect

    Ramirez, A.; Daily, W,; LeBrecque, D.

    1996-01-01

    A controlled experiment was conducted to evaluate the performance of complex electrical resistivity tomography (CERT) for detecting and delineating free product dense non-aqueous phase liquid (DNAPL) in the subsurface. One hundred ninety liters of PCE were released at a rate of 2 liters per hour from a point 0.5 m below ground surface. The spill was conducted within a double walled tank where saturated layers of sand, bentonite and a sand/bentonite mixture were installed. Complex electrical resistance measurements were performed. Data were taken before the release, several times during, and then after the PCE was released. Magnitude and phase were measured at 1 and 64 Hz. Data from before the release were compared with those during the release for the purpose of imaging the changes in conductivity resulting from the plume. Conductivity difference tomographs showed a decrease in electrical conductivity as the DNAPL penetrated the soil. A pancake-shaped anomaly developed on the top of a bentonite layer at 2 m depth. The anomaly grew in magnitude and extent during the release and borehole television surveys data confirmed the anomaly to be free-product PCE whose downward migration was stopped by the low permeability clay. The tomographs clearly delineated the plume as a resistive anomaly.

  6. Monitoring TCE Degradation by In-situ Bioremediation in TCE-Contaminated site

    NASA Astrophysics Data System (ADS)

    Han, K.; Hong, U.; Ahn, G.; Jiang, H.; Yoo, H.; Park, S.; Kim, N.; Ahn, H.; Kwon, S.; Kim, Y.

    2012-12-01

    Trichloroethylene (TCE) is a long-term common groundwater pollutant because the compound with high density is slowly released into groundwater. Physical and chemical remediation processes have been used to clean-up the contaminant, but novel remediation technology is required to overcome a low efficiency of the traditional treatment process. Many researchers focused on biological process using an anaerobic TCE degrading culture, but it still needs to evaluate whether the process can be applied into field scale under aerobic condition. Therefore, in this work we investigated two different tests (i.e., biostimulation and bioaugmentation) of biological remediation through the Well-to-Well test (injection well to extraction well) in TCE-contaminated site. Also solutions (Electron donor & acceptor, tracer) were injected into the aquifer using a liquid coupled with nitrogen gas sparging. In biostimulation, we use 3 phases to monitoring biological remediation. Phase 1: we inject formate solution to get electron donor hydrogen (hydrogen can be generated from fermentation of formate). We also inject bromide as tracer. Phase 2: we made injection solution by formate, bromide and sulfate. The reason why we inject sulfate is that as a kind of electron accepter, sulfate reduction process is helpful to create anaerobic condition. Phase 3: we inject mixed solution made by formate, sulfate, fumarate, and bromide. The degradation of fumarate has the same mechanism and condition with TCE degradation, so we added fumarate to make sure that if the anaerobic TCE degradation by indigenous microorganisms started up (Because low TCE concentration by gas sparging). In the bioaugmentation test, we inject the Evanite culture (containing dehalococcoides spp) and TCE degradation to c-DCE, VC, ETH was monitored. We are evaluating the transport of the Evanite culture in the field by measuring TCE and VC reductases.

  7. SOURCES, EMISSION AND EXPOSURE TO TRICHLOROETHYLENE (TCE) AND RELATED CHEMICALS

    EPA Science Inventory

    This report documents the sources, emission, environmental fate and exposures for TCE, some of its metabolites, and some other chemicals known to produce identical metabolites. The major findings for TCE are:


    1. The primary sources releasing TCE to the environment ...

    2. Molecular biomarker-based biokinetic modeling of a PCE-dechlorinating and methanogenic mixed culture.

      PubMed

      Heavner, Gretchen L W; Rowe, Annette R; Mansfeldt, Cresten B; Pan, Ju Khuan; Gossett, James M; Richardson, Ruth E

      2013-04-16

      Bioremediation of chlorinated ethenes via anaerobic reductive dechlorination relies upon the activity of specific microbial populations--most notably Dehalococcoides (DHC) strains. In the lab and field Dehalococcoides grow most robustly in mixed communities which usually contain both fermenters and methanogens. Recently, researchers have been developing quantitative molecular biomarkers to aid in field site diagnostics and it is hoped that these biomarkers could aid in the modeling of anaerobic reductive dechlorination. A comprehensive biokinetic model of a community containing Dehalococcoides mccartyi (formerly D. ethenogenes) was updated to describe continuously fed reactors with specific biomass levels based on quantitative PCR (qPCR)-based population data (DNA and RNA). The model was calibrated and validated with subsets of chemical and molecular biological data from various continuous feed experiments (n = 24) with different loading rates of the electron acceptor (1.5 to 482 μeeq/L-h), types of electron acceptor (PCE, TCE, cis-DCE) and electron donor to electron acceptor ratios. The resulting model predicted the sum of dechlorination products vinyl chloride (VC) and ethene (ETH) well. However, VC alone was under-predicted and ETH was over predicted. Consequently, competitive inhibition among chlorinated ethenes was examined and then added to the model. Additionally, as 16S rRNA gene copy numbers did not provide accurate model fits in all cases, we examined whether an improved fit could be obtained if mRNA levels for key functional enzymes could be used to infer respiration rates. The resulting empirically derived mRNA "adjustment factors" were added to the model for both DHC and the main methanogen in the culture (a Methanosaeta species) to provide a more nuanced prediction of activity. Results of this study suggest that at higher feeding rates competitive inhibition is important and mRNA provides a more accurate indicator of a population's instantaneous

    3. Molecular Biomarker-Based Biokinetic Modeling of a PCE-Dechlorinating and Methanogenic Mixed Culture

      SciTech Connect

      Heavner, Gretchen L. W.; Rowe, Annette R.; Mansfeldt, Cresten B.; Pan, Ju Khuan; Gossett, James M.; Richardson, Ruth E.

      2013-04-16

      Bioremediation of chlorinated ethenes via anaerobic reductive dechlorination relies upon the activity of specific microbial population-most notably Dehalococcoides (DHC) strains. In the lab and field Dehalococcoides grow most robustly in mixed communities which usually contain both fermenters and methanogens. Recently, researchers have been developing quantitative molecular biomarkers to aid in field site diagnostics and it is hoped that these biomarkers could aid in the modeling of anaerobic reductive dechlorination. A comprehensive biokinetic model of a community containing Dehalococcoides mccartyi (formerly D. ethenogenes) was updated to describe continuously fed reactors with specific biomass levels based on quantitative PCR (qPCR)-based population data (DNA and RNA). The model was calibrated and validated with subsets of chemical and molecular biological data from various continuous feed experiments (n = 24) with different loading rates of the electron acceptor (1.5 to 482 μeeq/L-h), types of electron acceptor (PCE, TCE, cis-DCE) and electron donor to electron acceptor ratios. The resulting model predicted the sum of dechlorination products vinyl chloride (VC) and ethene (ETH) well. However, VC alone was under-predicted and ETH was over predicted. Consequently, competitive inhibition among chlorinated ethenes was examined and then added to the model. Additionally, as 16S rRNA gene copy numbers did not provide accurate model fits in all cases, we examined whether an improved fit could be obtained if mRNA levels for key functional enzymes could be used to infer respiration rates. The resulting empirically derived mRNA “adjustment factors” were added to the model for both DHC and the main methanogen in the culture (a Methanosaeta species) to provide a more nuanced prediction of activity. Results of this study suggest that at higher feeding rates competitive inhibition is important and mRNA provides a more accurate indicator of a population’s instantaneous

    4. PERCHLOROETHYLENE (PERC) INHIBITS FUNCTION OF VOLTAGE-GATED CALCIUM CHANNELS IN PHEOCHROMOCYTOMA CELLS.

      EPA Science Inventory

      The industrial solvent perchloroethylene (PERC) is listed as a hazardous air pollutant in the 1990 Ammendments to Clean Air Act and is a known neurotoxicant. However, the mechanisms by which PERC alters nervous system function are poorly understood. In recent years, it has been d...

    5. CATALYTIC STEAM REFORMING OF CHLOROCARBONS: TRICHLOROETHANE, TRICHLOROETHYLENE AND PERCHLOROETHYLENE. (R826694C633)

      EPA Science Inventory

      The effective destruction of trichloroethane, trichloroethylene and perchloroethylene by steam reforming with a commercial nickel catalyst has been demonstrated. Conversion levels of up to 0.99999 were attained in both laboratory and semi-pilot experiments, with the products c...

    6. Carbon isotope fractionation during abiotic reductive dehalogenation of trichloroethene (TCE).

      PubMed

      Bill, M; Schüth, C; Barth, J A; Kalin, R M

      2001-08-01

      Dehalogenation of trichloroethene (TCE) in the aqueous phase, either on palladium catalysts with hydrogen as the reductant or on metallic iron, was associated with strong changes in delta13C. In general, the delta13C of product phases were more negative than those of the parent compound and were enriched with time and fraction of TCE remaining. For dehalogenation with iron, the delta13C of TCE and products varied from -42/1000 to +5/1000. For the palladium experiments, the final product, ethane, reached the initial delta13C of TCE at completion of the dehalogenation reaction. During dehalogenation, the carbon isotope fractionation between TCE and product phases was not constant. The variation in delta13C of TCE and products offers a new monitoring tool that operates independently of the initial concentration of pollutants for abiotic degradation processes of TCE in the subsurface, and may be useful for evaluation of remediation efficiency. PMID:11513419

    7. Inter-Domain Redundancy Path Computation Methods Based on PCE

      NASA Astrophysics Data System (ADS)

      Hayashi, Rie; Oki, Eiji; Shiomoto, Kohei

      This paper evaluates three inter-domain redundancy path computation methods based on PCE (Path Computation Element). Some inter-domain paths carry traffic that must be assured of high quality and high reliability transfer such as telephony over IP and premium virtual private networks (VPNs). It is, therefore, important to set inter-domain redundancy paths, i. e. primary and secondary paths. The first scheme utilizes an existing protocol and the basic PCE implementation. It does not need any extension or modification. In the second scheme, PCEs make a virtual shortest path tree (VSPT) considering the candidates of primary paths that have corresponding secondary paths. The goal is to reduce blocking probability; corresponding secondary paths may be found more often after a primary path is decided; no protocol extension is necessary. In the third scheme, PCEs make a VSPT considering all candidates of primary and secondary paths. Blocking probability is further decreased since all possible candidates are located, and the sum of primary and secondary path cost is reduced by choosing the pair with minimum cost among all path pairs. Numerical evaluations show that the second and third schemes offer only a few percent reduction in blocking probability and path pair total cost, while the overheads imposed by protocol revision and increase of the amount of calculation and information to be exchanged are large. This suggests that the first scheme, the most basic and simple one, is the best choice.

    8. Long-term perchloroethylene exposure: a limited meta-analysis of neurobehavorial deficits in occupationally and residentially exposed groups

      EPA Science Inventory

      The literature concerning the neurobehavioral and neurophysiological effects of long-term exposure to perchloroethylene (PERC) in humans was meta-analyzed to provide a quantitative review and synthesis. The useable data base from this literature comprised studies reporting effec...

    9. Status of groundwater pollution in the San Gabriel Valley, California

      SciTech Connect

      Earley, J.D.

      1987-07-01

      Contamination of groundwater in the San Gabriel Valley of California has been identified as a potential health hazard from industrial sources. Sampling has revealed the presence of trichloroethylene (TCE), perchloroethylene (PCE) and carbon tetrachloride (CTC); therefore, water purveyors are using a variety of means to alleviate the contamination and the use of contaminated water.

    10. Biodegradation of vapor phase trichloroethylene (TCE) in compost packed biofilters

      SciTech Connect

      Sukesan, S.; Watwood, M.E.

      1996-10-01

      Batch and column scale biofiltration experiments were performed to measure biodegradation of gaseous trichloroethylene (TCE) in finished compost. Compost was amended with hydrocarbon gas (methane or propane) as primary substrate to support microorganisms capable of cometabolic TCE degradation. In column biofilter experiments hydrocarbon utilization was observed within 10-15 days; gaseous TCE (50 ppmv) was then introduced continuously into the biofilter at approximately 1 L min{sup -1}. Columns supplied with 0.5% v/v methane removed 73% TCE after 8 days of continuous column operation, whereas amendment with 0.25% v/v methane corresponded with TCE removal of 93%, which was observed after 1.5 h of column operation. Similar results were obtained for propane amendment. Biofilters without hydrocarbon amendment exhibited no TCE biodegradation over 35 days. These results, analyzed together with those obtained in batch experiments, indicate that hydrocarbon identity and concentration and other related parameters influence the extent of ICE breakdown.

    11. Methanotrophic TCE biodegradation in a multi-stage bioreactor

      SciTech Connect

      Tschantz, M.L.F.; Bowman, J.P.; Bienkowski, P.R.; Sayler, G.S.; Donaldson, T.L.; Strong-Gunderson, J.M.; Palumbo, A.V.; Herbes, S.E.

      1995-08-01

      A two-stage bioreactor system was continuously fed a solution of TCE (concentrations ranging between 0.2 and 20 mg L{sup -1}) at 2 mL min{sup -1}; the system utilized a mutant (PP358) of the methane oxidizing bacterium Methylosinus trichosporium OB3b for the fortuitous cooxidation of TCE by the enzyme-soluble methane monooxygenase (sMMO). A methane-free environment was maintained in the TCE treatment portion of the reactor (plug-flow columns), minimizing the effects of competitive inhibition between TCE and methane for the sMMO. The reactor was operated in two separate flow configurations, single-pass and cross-flow, with TCE removal percentages exceeding 78% (for a TCE feed concentration of 20 mg L{sup -1}) and 93% (for a TCE feed concentration of 10 mg L{sup -1}), respectively. A r{sub max} of 109.4 mg of TCE (g of VS){sup -1} d{sup -1} for a TCE feed concentration of 20 mg L{sup -1} was obtained, suggesting that high rates of degradation occurred within the reactor. TCE-induced toxicity effects occurred at TCE feed concentrations of 10 mg L{sup -1} and greater, resulting in declines of the biomass concentrations and the enzyme activities. A model describing the rate of TCE degradation in the plug-flow columns was proposed by Alvarez-Cohen et al. and was modified to incorporate the suboptimal activities of sMMO. 29 refs., 7 figs., 1 tab.

    12. CHARACTERIZATION OF THE EFFECTS OF INHALED PERCHLOROETHYLENE ON SUSTAINED ATTENTION IN RATS PERFORMING A VISUAL SIGNAL DETECTION TASK

      EPA Science Inventory

      The aliphatic hydrocarbon perchloroethyelene (PCE) has been associated with neurobehavioral dysfunction including reduced attention in humans. The current study sought to assess the effects of inhaled PCE on sustained attention in rats performing a visual signal detection task (S...

    13. Laboratory and field evaluation of a SAW microsensor array for measuring perchloroethylene in breath.

      PubMed

      Groves, William A; Achutan, Chandran

      2004-12-01

      This article describes the laboratory and field performance evaluation of a small prototype instrument employing an array of six polymer-coated surface acoustic wave (SAW) sensors and a thermal desorption preconcentration unit for rapid analysis of perchloroethylene in breath. Laboratory calibrations were performed using breath samples spiked with perchloroethylene to prepare calibration standards spanning a concentration range of 0.1-10 ppm. A sample volume of 250 mL was preconcentrated on 40 mg of Tenax GR at a flow rate of 100 mL/min, followed by a dry air purge and thermal desorption at a temperature of 200 degrees C. The resulting pulse of vapor was passed over the sensor array at a flow rate of 20 mL/min and sensor responses were recorded and displayed using a laptop computer. The total time per analysis was 4.5 min. SAW sensor responses were linear, and the instrument's limit of detection was estimated to be 50 ppb based on the criterion that four of the six sensors show a detectable response. Field performance was evaluated at a commercial dry-cleaning operation by comparing prototype instrument results for breath samples with those of a portable gas chromatograph (NIOSH 3704). Four breath samples were collected from a single subject over the course of the workday and analyzed using the portable gas chromatograph (GC) and SAW instruments. An additional seven spiked breath samples were prepared and analyzed so that a broader range of perchloroethylene concentrations could be examined. Linear regression analysis showed excellent agreement between prototype instrument and portable GC breath sample results with a correlation coefficient of 0.99 and a slope of 1.04. The average error for the prototype instrument over a perchloroethylene breath concentration range of 0.9-7.2 ppm was 2.6% relative to the portable GC. These results demonstrate the field capabilities of SAW microsensor arrays for rapid analysis of organic vapors in breath. PMID:15742707

    14. Draft genome sequence and characterization of Desulfitobacterium hafniense PCE-S

      PubMed Central

      2015-01-01

      This genome report describes the draft genome and the physiological characteristics of Desulfitobacterium hafniense PCE-S, a Gram-positive bacterium known to dechlorinate tetrachloroethene (PCE) to dichloroethene by a PCE reductive dehalogenase. The draft genome has a size of 5,666,696 bp with a G + C content of 47.3%. The genome is very similar to the already sequenced Desulfitobacterium hafniense Y51 and the type strain DCB-2. We identified two complete reductive dehalogenase (rdh) genes in the genome of D. hafniense PCE-S, one of which encodes PceA, the PCE reductive dehalogenase, and is located on a transposon. Interestingly, this transposon structure differs from the PceA-containing transposon of D. hafniense Y51. The second rdh encodes an unknown reductive dehalogenase, highly similar to rdhA 7 found in D. hafniense DCB-2, in which the corresponding gene is disrupted. This reductive dehalogenase might be responsible for the reductive dechlorination of 2,4,5-trichlorophenol and pentachlorophenol, which is mediated by D. hafniense PCE-S in addition to the reductive dechlorination of PCE. PMID:26203328

  1. Treatment of trichloroethene (TCE) with a fluidized-bed bioreactor

    SciTech Connect

    Foeller, J.R.; Segar, R.L. Jr.

    1997-12-31

    Fluidized-bed bioreactors (FBBR`s) offer a promising alternative to existing treatment technologies for the treatment of water contaminated with chlorinated solvents. The objective of this research was to test a laboratory-scale FBBR for removal of trichloroethene (TCE) from groundwater and to study the FBBR kinetic behavior so that field-scale treatment systems could be designed. Phenol was selected as the growth substrate for biofilm-forming microorganisms enriched from activated-sludge because phenol induces enzymes capable of cometabolizing TCE and lesser chlorinated ethenes. The biofilm forming microorganisms were identified as Pseudomonas putida, a common soil bacterium. Experiments with a conventional, single-pass FBBR addressed TCE removal as effected by changes in TCE loading, phenol loading, and media type. In this study, TCE removal using quartz filter sand and garnet filter sand as the biofilm attachment media was measured. Removal ranged from 20 to 60% and was not affected by the media type. Also, removal was not affected by inlet TCE concentration over the range of 100 to 500 {micro}g/L provided the phenol loading was decreased with increasing TCE loading. The FBBR was capable of complete phenol removal at an inlet concentration of 20 to 25 mg/L and an empty-bed contact time of 2.7 minutes. However, the empty-bed contact time was insufficient to sustain greater than 40 to 50% removal of TCE in a nutrient-amended groundwater.

  2. Cometabolic degradation kinetics of TCE and phenol by Pseudomonas putida.

    PubMed

    Chen, Yan-Min; Lin, Tsair-Fuh; Huang, Chih; Lin, Jui-Che

    2008-08-01

    Modeling of cometabolic kinetics is important for better understanding of degradation reaction and in situ application of bio-remediation. In this study, a model incorporated cell growth and decay, loss of transformation activity, competitive inhibition between growth substrate and non-growth substrate and self-inhibition of non-growth substrate was proposed to simulate the degradation kinetics of phenol and trichloroethylene (TCE) by Pseudomonas putida. All the intrinsic parameters employed in this study were measured independently, and were then used for predicting the batch experimental data. The model predictions conformed well to the observed data at different phenol and TCE concentrations. At low TCE concentrations (<2 mg l(-1)), the models with or without self-inhibition of non-growth substrate both simulated the experimental data well. However, at higher TCE concentrations (>6 mg l(-1)), only the model considering self-inhibition can describe the experimental data, suggesting that a self-inhibition of TCE was present in the system. The proposed model was also employed in predicting the experimental data conducted in a repeated batch reactor, and good agreements were observed between model predictions and experimental data. The results also indicated that the biomass loss in the degradation of TCE below 2 mg l(-1) can be totally recovered in the absence of TCE for the next cycle, and it could be used for the next batch experiment for the degradation of phenol and TCE. However, for higher concentration of TCE (>6 mg l(-1)), the recovery of biomass may not be as good as that at lower TCE concentrations. PMID:18586301

  3. EVALUATION OF GEOPHYSICAL METHODS FOR THE DETECTION OF SUBSURFACE TETRACHLOROETHYLENE (PCE) IN CONTROLLED SPILL EXPERIMENTS

    EPA Science Inventory

    Tetrachloroethylene (PCE), typically used as a dry cleaning solvent, is a predominant contaminant in the subsurface at Superfund Sites. PCE is a dense non-aqueous phase liquid (DNAPL) that migrates downward into the earth, leaving behind areas of residual saturation and free prod...

  4. Fate and Transport of TCE Solvents Through Saturated Karst Aquifer

    NASA Astrophysics Data System (ADS)

    Padilla, I. Y.; Carmona, M.; Anaya, A. A.

    2014-12-01

    Dense Nonaqueous-Phase Liquids (DNAPLs) are a group of organic compounds that have been a serious problem for groundwater pollution in karst. The industrial production and utilization of these chemicals spread since 1940, and are present at tens of thousands of contaminated sites worldwide. The physic-chemical properties of DNAPLs in conjunction with the hydraulic properties of the karst systems create the perfect condition for DNAPLs to penetrate the epikarst, reach the groundwater, and more within the karst system to zones of potential exposure, such as wells, streams and wetlands. Trichloroethylene (TCE) is the most common DNPAL found in the subsurface environment. This research studies the fate and transport of TCE DNAPL in a karstified limestone physical model (KLPM). Experiments are carried out in KLPM. The KLPM is an enclosed stainless steel tank packed with a rectangular limestone block (15cm x 15cm x 76cm) that simulates a saturated confine karst aquifer. DNAPL experiment involve the injection of 40 ml of pure TCE into steady groundwater flow at the upstream boundary of the KLPM model, while sampling spatially and temporally along the block. Samples are analyzed for TCE on the pure and dissolved phase. Pure TCE is analyzed volumetrically and dissolved phase concentrations are analyze using a High Performance Liquid Chromatography (HPLC). TCE data is used to construct temporal distributions curves (TDCs) at different spatial locations. Results show that pure TCE volumes are collected at the beginnings of the experiment in sampling ports located near the injection port and along preferential flow paths. TCE concentration TDCs show spatial variations related to the limestone block heterogeneously. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response and long tailing of TCE of TCE concentration are associated with diffusive transport in rock matrix and mass transport rates limitations. Bimodal distributions are

  5. Decontamination of TCE- and U-rich waters by granular iron: Role of sorbed Fe(II)

    SciTech Connect

    Charlet, L.; Liger, E.; Gerasimo, P.

    1998-01-01

    Uranium (UO{sub 2}{sup 2+}) and chlorinated aliphatics [tetrachloroethane (PCE) and trichloroethane (TCE)] can be reduced and thus immobilized or degraded, respectively, by the same abiotic mechanism. In this mechanism the reduction reaction is coupled to the oxidation of Fe(II) sorbed on iron corrosion products such as hematite. This is indicated by the equilibrium E{sub h} values measured during uranium immobilization and PCE degradation reactions of zerovalent iron. These values fit closely with those measured in the Fe(II)-{alpha}Fe{sub 2}O{sub 3}-H{sub 2}O system (in the absence of U or PCE), not those of the Fe(o)/Fe(II) or H{sub 2}(g)/H{sub 2}O couples. Because iron (II) is very unstable in environments that are not strictly anaerobic, Fe(o) serves as a source of Fe(II). The reduction kinetic rate, analyzed in detail for the reduction of U(VI), is found to be a function of the concentration of OH{sup {minus}}, Fe{sup 2+} and reactive surface sites, and is given in terms of sorbed species concentrations by {l_brace}d[U(VI)]{sub ads}{r_brace}/dt = {l_brace}{minus}k{prime}[{triple_bond}FeOFeOH{sup 0}][U(VI)]{sub ads}{r_brace}. This rate law applies to organic pollutants as well, as long as they can be reduced by surface Fe(II): {l_brace}d[Pollutant]{r_brace}/dt = {l_brace}{minus}k{prime}[{triple_bond}FeOFeOH{sup 0}][Pollutant]{r_brace}. This mechanism suggests new possibilities for the improvement of low-cost decontamination techniques for U- and chlorinated aliphatic-rich waters.

  6. Coupling Surfactant Flushing and Bioaugmentation for PCE-DNAPL Source Zone Treatment

    NASA Astrophysics Data System (ADS)

    Cápiro, N. L.; Granbery, E. K.; Amos, B. K.; Löffler, F. E.; Pennell, K. D.

    2008-12-01

    Enhanced solubilization flushing using a biodegradable surfactant (Tween 80) was combined with bioaugmentation to initiate microbial reductive dechlorination and detoxify residual tetrachloroethene (PCE)- dense nonaqueous phase liquid (DNAPL). Dechlorination activity, spatial distribution of Dehalococcoides spp., and down-gradient plume development were monitored in a 2-D aquifer cell equipped with eighteen sampling ports. Saturation distributions of the PCE-DNAPL source zone were quantified using a light transmission system to determine the ganglia-to-pool (GTP) volume ratio, which was approximately 1.5 (i.e., 60% ganglia and 40% pools) prior to surfactant flushing. Flushing with three pore volumes (PVs) of 4% (w/w) Tween 80 solution recovered approximately 55% of the original PCE mass and reduced PCE effluent concentration from saturation (200 mg/L) to less than 50 mg/L. Following the introduction of reduced basal salts medium amended with 10 mM lactate, nine side ports located upstream and within the initial PCE- DNAPL source zone were augmented with Bio-Dechlor INOCULUM (BDI), a PCE-to-ethene dechlorinating consortium. Flux-averaged measurements of aqueous effluent samples revealed the conversion of PCE to cis-dichloroethene (DCE) with minimal lag time (7 days, approx. 1 PV), and vinyl chloride and ethene were detected within 10 PVs after bioaugmentation. Quantitative real-time PCR (qPCR) targeting Dehalococcoides spp. demonstrated growth once aqueous PCE concentrations decreased below inhibitory levels (~540 mM), with significant growth (2 to 4-orders of magnitude) near the remaining source zone. These results demonstrate the successful colonization of a pool-dominated (NAPL saturation >0.13) PCE- DNAPL source zone by a dechlorinating consortium following partial mass removal, and the potential for locally bioenhanced DNAPL dissolution.

  7. TCE adsorption by GAC preloaded with humic substances

    SciTech Connect

    Kilduff, J.E.; Karanfil, T.; Weber, W.J. Jr.

    1998-05-01

    Adsorption of trichloroethylene (TCE) by activated carbon preloaded with humic and fulvic acids was studied under several conditions in completely mixed batch systems. The authors investigated how molecular weight and molecular-weight distribution of preloaded humic substances affected subsequent adsorption of TCE. The capacity of carbon to adsorb TCE was most greatly reduced in carbon that was preloaded with humic acid components having molecular weights less than about 1,400 g/mol as polystyrene sulfonate. The adsorption capacity was greatly reduced in carbon that was preloaded with whole humic mixtures in which lower molecular weights predominated. The energy distributions of adsorbent indicate that preloaded compounds preferentially occupy high-energy sites, making them inaccessible to subsequently encountered TCE.

  8. IRIS Toxicological Review of Trichloroethylene (TCE) (External Review Draft)

    EPA Science Inventory

    EPA is conducting a peer review and public comment of the scientific basis supporting the human health hazard and dose-response assessment of Trichloroethylene (TCE) that when finalized will appear on the Integrated Risk Information System (IRIS) database.

  9. TCE degradation by methanotrophic bacteria in a water-saturated sand column

    SciTech Connect

    Fayolle, F.; Le Roux, F.; Treboul, C.; Ballerini, D.

    1995-12-31

    Trichloroethylene (TCE) degradation in a polluted aquifer was simulated using water-saturated sand columns with alternative injection of aqueous TCE/salt solution and CH{sub 4}/air mixture. Experiments were performed with two columns. The first under abiotic conditions to determine the TCE stripped fraction and the second seeded with a methanotrophic strain to quantify TCE biodegradation. Preliminary tests were performed in flasks to optimize CH{sub 4}/air injection. Stripping of TCE increased with increasing influent TCE concentration and residence time inside the column. TCE losses in gaseous effluent varied between 34% and 67% of the TCE injected. Under nonlimiting oxygen and mineral nutrient conditions, 50% of the TCE was biodegraded immediately after seeding the column, this value finally stabilizing at 20 to 30% of residual TCE after stripping.

  10. Coupling Surfactants with Permanganate for PCE DNAPL Removal: Coinjection or Sequential Application as Delivery Methods

    NASA Astrophysics Data System (ADS)

    Dugan, P. J.; Siegrist, R. L.; Crimi, M. L.

    2008-12-01

    Batch experiments and two-dimensional (2-D) flow-through cell experiments were conducted to investigate coupling surfactant-enhanced aquifer remediation (SEAR) with in situ chemical oxidation (ISCO) of tetrachloroethene (PCE) dense nonaqueous phase liquid (DNAPL) for PCE mass destruction. Previous batch screening tests were performed on surfactants and cosolvents in the presence of the oxidant potassium permanganate, to assess compatibility for coupling with permanganate. The anionic surfactants sodium dioctyl sulfosuccinate (Aerosol OT), and sodium hexadecyl diphenyl oxide disulfonate (Dowfax 8390) were compatible and selected for use. Two delivery methods were investigated: (1) coinjection of 0.66 pore volumes (PVs) of 1.0-wt% Aerosol-OT, 0.5-wt% Dowfax 8390, 0.35-wt% CaBr2, and 0.75-wt% NaBr, (for enhanced PCE solubilization) with 0.5-wt% permanganate(for DNAPL mass destruction), and (2) sequential application of 0.66 PVs of the same surfactant solution followed by 0.66 PVs of 0.5-wt% permanganate flush. The 2-D cell packing configuration consisted of a fine-grained silica sand matrix with an embedded medium- grained sand lens, which allowed for the development of a high saturation PCE DNAPL source zone (~9-11% v/v) within the lens of each cell. For both experiments the flushing solutions were delivered at a linear velocity of 52 cm/day. Water quality samples were collected from eight point sampling ports, as well as the cell effluent. Samples were analyzed for PCE, chloride, and permanganate. At the conclusion of the experiments, the mass of PCE removed was quantified by destructively analyzing the cell. Results indicate complete mass removal using sequential application as a delivery method. In the coinjection experiment, cores extracted at the conclusion revealed that 99.8% of PCE DNAPL mass was removed. However, it was not possible to close a mass balance between the initial PCE added and the PCE removed. It is hypothesized this result was due to incomplete

  11. The Potential of the Ni-Resistant TCE-Degrading Pseudomonas putida W619-TCE to Reduce Phytotoxicity and Improve Phytoremediation Efficiency of Poplar Cuttings on A Ni-TCE Co-Contamination.

    PubMed

    Weyens, Nele; Beckers, Bram; Schellingen, Kerim; Ceulemans, Reinhart; van der Lelie, Daniel; Newman, Lee; Taghavi, Safiyh; Carleer, Robert; Vangronsveld, Jaco

    2015-01-01

    To examine the potential of Pseudomonas putida W619-TCE to improve phytoremediation of Ni-TCE co-contamination, the effects of inoculation of a Ni-resistant, TCE-degrading root endophyte on Ni-TCE phytotoxicity, Ni uptake and trichloroethylene (TCE) degradation of Ni-TCE-exposed poplar cuttings are evaluated. After inoculation with P. putida W619-TCE, root weight of non-exposed poplar cuttings significantly increased. Further, inoculation induced a mitigation of the Ni-TCE phytotoxicity, which was illustrated by a diminished exposure-induced increase in activity of antioxidative enzymes. Considering phytoremediation efficiency, inoculation with P. putida W619-TCE resulted in a 45% increased Ni uptake in roots as well as a slightly significant reduction in TCE concentration in leaves and TCE evapotranspiration to the atmosphere. These results indicate that endophytes equipped with the appropriate characteristics can assist their host plant to deal with co-contamination of toxic metals and organic contaminants during phytoremediation. Furthermore, as poplar is an excellent plant for biomass production as well as for phytoremediation, the obtained results can be exploited to produce biomass for energy and industrial feedstock applications in a highly productive manner on contaminated land that is not suited for normal agriculture. Exploiting this land for biomass production could contribute to diminish the conflict between food and bioenergy production. PMID:25174423

  12. Isolation of a methanogenic bacterium, Methanosarcina sp. strain FR, for its ability to degrade high concentration of perchloroethylene.

    PubMed

    Cabirol, N; Villemur, R; Perrier, J; Jacob, F; Fouillet, B; Chambon, P

    1998-12-01

    Tetrachloroethylene (PCE) is a toxic compound essentially used as a degreasing and dry-cleaning solvent. A methanogenic and sulfate-reducing consortium that dechlorinates and mineralizes high concentrations of PCE was derived from anaerobically digested sludge obtained from a waste water treatment plant (Bourg-en-Bresse, France). A methanogenic bacterium, strain FR, was isolated from this acclimated consortium. On the basis of morphological and physiological characteristics, strain FR was classified in the genus of Methanosarcina. Phylogeny analysis with the 16S rRNA gene sequence revealed that strain FR is highly related to Methanosarcina mazei and Methanosarcina frisia (99.6 and 99.5% identity, respectively). High concentrations (50-87 microM) of PCE were completely dechlorinated by strain FR cultures at the rate of 76 nM-mg protein(-1).day(-1). PCE dechlorination produced a nonidentified compound. The tracer experiments with [13C]PCE revealed that the product was nonchlorinated. Dechlorination of PCE to trichloroethylene was still active in the presence of boiled cell extract of the strain FR. However, no further dechlorination was observed. This result suggests that a cofactor rather than an enzymatic system is responsible for the first dechlorination of PCE. Dechlorination-active fractions purified from cell extracts on a XAD-4 column revealed the presence of F(420), F(430), and cobamides cofactors. This is the first report of the isolation of a methanogenic bacterium with the ability to dechlorinate high concentrations of PCE to a nonchlorinated product. PMID:10383226

  13. Drip Irrigation Aided Phytoremediation for Removal of TCE from Groundwater

    SciTech Connect

    Wilde, E.W.

    2003-04-24

    Groundwater in D-Area at the Savannah River Site (SRS) is contaminated with trichloroethylene (TCE) and by-products resulting from discharges of this organic solvent during past disposal practices. This contaminated groundwater occurs primarily at depths of 9 meters to 15 meters below ground surface, well below the depths that are typically penetrated by plant roots. The process investigated in this study involved pumping water from the contaminated aquifer and discharging the water into overlying test plots two inches below the surface using drip irrigation. The field treatability study was conducted from 8/31/00 to 4/18/02 using six 0.08 hectare test plots, two each containing pines, cottonwoods, and no vegetation (controls). The primary objective was to determine the overall effectiveness of the process for TCE removal and to determine the principal biotic and abiotic pathways for its removal. Results demonstrated that the process provides a viable method to remove TCE-contaminated groundwater. The data clearly showed that the presence of trees reduced volatilization of TCE from the drip irrigation system to the atmosphere. Influent groundwater TCE concentrations averaging 89 mg/L were reduced to non-detectable levels (less than 5 mg/L) within the upper two feet of soil (rhizosphere).

  14. The effect of Fe(0) on electrokinetic remediation of clay contaminated with perchloroethylene.

    PubMed

    Yuan, C

    2006-01-01

    The present paper was to investigate the effect of Fe(0) reaction barrier position and Fe(0) quantity on the remediation efficiency and electrokinetic performances of tetrachloroethylene (PCE) contaminated clay under potential gradient of 2 V/cm for 5 days. The Fe(0) reaction barrier was composed of 2 to approximately 16 g of Fe(0) mixed with Ottawa sand in a ratio of 1: 2. Its positions were respectively located at the anode, the middle, and the cathode end of the electrokinetic cell. Results showed that a relatively higher remediation of 66% of PCE was found as the Fe(0) reaction barrier located at the cathode side, which corresponded to a factor 2.4 times greater than that in the EK system alone (27.0%). As the Fe(0) quantity increased to 16 g, a highest remediation efficiency of 90.7% was found. It was concluded that the PCE removal in the EK/Fe(0) system was dominated by Fe(0) quantity rather than the Fe(0) reaction barrier position. As more Fe(0) existed in the EK system, a higher electroosmosis flow, higher permeability, and lower soil pH after treatment were found. The cost analyses were also investigated in this research. PMID:16749444

  15. Field and laboratory evaluation of a diffusive emitter for semipassive release of PCE to an aquifer

    SciTech Connect

    Arildskov, N.P.; Devlin, J.F.

    2000-02-01

    In controlled field experiments or model aquifers, it is sometimes desirable to introduce solutes below the water table without perturbing the flow system. Diffusive emitters offer a means of achieving that goal. In this study, two laboratory experiments were conducted to evaluate nylon tubing as a diffusive emitter for tetrachloroethene (PCE). The initial approach was to pump a saturated aqueous PCE solution through a piece of nylon tubing immersed in a flow-through contractor vessel. Millipore water was pumped through the contractor vessel at a constant rate. Due to PCE diffusion through the nylon, a steady-state concentration in the contractor vessel eventually developed. The process was well described by a computer model that accounted for retarded diffusion through the nylon. In a second experiment, pieces of nylon tubing were exposed to a relatively low concentration of PCE in water for 10 days in gently rotated hypovials. With the aid of a second diffusion model, the bulk diffusion coefficient was obtained from the concentration history of the solution. With the different experimental conditions taken into account, there was reasonably good agreement between the bulk diffusion coefficients in the two experiments. The results were used in the field design of a semipassive release system. Evaluation of this system showed a lower than expected steady-state concentration of PCE inside the releasing wells. The difference is likely due to lower temperature, variable PCE concentrations in the nylon tubing, and nonideal mixing in the wells. The work has shown that laboratory derived diffusion coefficients for polymeric materials are likely to be larger than, but within an order of magnitude of, the effective diffusion coefficients exhibited by emitters in the field. Nevertheless, with temperature corrections taken into account and proper well development, these values could be used to design emitters that would suit most practical applications.

  16. KINETICS AND MECHANISMS FOR TCE OXIDATION BY PERMANGANATE

    EPA Science Inventory

    The oxidation of trichloroethylene (TCE) by permanganate was studied via a series of kinetic experiments. The goal in product identificationa dn parameterization of the oxidation kinetics was to assess the utility of this reaction as the basis for the in-situ remediation of grou...

  17. In Situ Dechlorination of TCE During Aquifer Heating

    SciTech Connect

    Truex, Michael J.; Powell, Thomas; Lynch, Kira P.

    2007-04-01

    Laboratory and field efforts were undertaken to examine trichloroethene (TCE) dechlorination as a function of temperature as an aquifer is heated to temperatures approaching boiling. Experiments were conducted using sediment samples during electrical resistance heating (ERH) treatment at the Fort Lewis East Gate Disposal Yard, which contains non-aqueous phase TCE and hydrocarbon contamination. Laboratory microcosms with these sediments showed TCE dechlorination at 70oC with measured products of acetylene, ethene, and ethane, indicating an abiotic component of the degradation. In contrast, TCE was dechlorinated to cis-1,2-dichloroethene in experiments at 10oC, likely by biological reductive dechlorination. The observed products at 70oC suggest dechlorination catalyzed by reduced sediment iron. Indications of in situ dechlorination were observed in periodic groundwater samples collected during field-scale electrical resistance heating from an average ambient temperature of about 19oC to near boiling. Dechlorination indicators included an increase in chloride concentration at the onset of heating and observation of acetylene, ethene, and methane at elevated temperatures. The data collected in this study suggest that dechlorination can occur during ERH. The overall cost-effectiveness of ERH may be enhanced by fortuitous in situ dechlorination and, potentially, can be further enhanced by specifically designing and operating ERH to maximize in situ dechlorination.

  18. TCE REMEDIATION: REVIEW OF TECHNOLOGIES AND COMPARISON OF COSTS

    EPA Science Inventory

    Information will be compiled to compare the cost and performance of conventional technologies used to remediate dissolved TCE plumes in groundwater with the cost and performance of innovative and/or emerging technologies. The conditions at Elizabeth City, NC (site of an ongoing f...

  19. FRACTIONATION OF STABLE CARBON ISOTOPES DURING ABIOTIC TRANSFORMATION OF TCE

    EPA Science Inventory

    At a Superfund Site in Minnesota, ground water is contaminated with trichloroethylene (TCE) with the contaminant plume stretching over five miles long. The ground water is iron and manganese reducing, and the complete absence of dichloroethylene, vinyl chloride, and ethene in th...

  20. The Impact of FeS Mineralogy on TCE Degradation

    EPA Science Inventory

    Iron- and sulfate-reducing conditions are often encountered in permeable reactive barrier (PRB) systems that are constructed to remove TCE from groundwater, which usually leads to the accumulation of FeS mineral phases in the matrix of the PRB. Poorly crystalline mackinawite (Fe...

  1. Impact of FeS Mineralogy on TCE Degradation

    EPA Science Inventory

    Iron- and sulfate-reducing conditions are often encountered in permeable reactive barrier (PRB) systems that are constructed to remove TCE from groundwater, which usually leads to the accumulation of FeS mineral phases in the matrix of the PRB. Poorly crystalline mackinawite (Fe...

  2. Transpiration and metabolisation of TCE by willow plants - a pot experiment.

    PubMed

    Schöftner, Philipp; Watzinger, Andrea; Holzknecht, Philipp; Wimmer, Bernhard; Reichenauer, Thomas G

    2016-07-01

    Willows were grown in glass cylinders filled with compost above water-saturated quartz sand, to trace the fate of TCE in water and plant biomass. The experiment was repeated once with the same plants in two consecutive years. TCE was added in nominal concentrations of 0, 144, 288, and 721 mg l(-1). Unplanted cylinders were set-up and spiked with nominal concentrations of 721 mg l(-1) TCE in the second year. Additionally, (13)C-enriched TCE solution (δ(13)C = 110.3 ‰) was used. Periodically, TCE content and metabolites were analyzed in water and plant biomass. The presence of TCE-degrading microorganisms was monitored via the measurement of the isotopic ratio of carbon ((13)C/(12)C) in TCE, and the abundance of (13)C-labeled microbial PLFAs (phospholipid fatty acids). More than 98% of TCE was lost via evapotranspiration from the planted pots within one month after adding TCE. Transpiration accounted to 94 to 78% of the total evapotranspiration loss. Almost 1% of TCE was metabolized in the shoots, whereby trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were dominant metabolites; less trichloroethanol (TCOH) and TCE accumulated in plant tissues. Microbial degradation was ruled out by δ(13)C measurements of water and PLFAs. TCE had no detected influence on plant stress status as determined by chlorophyll-fluorescence and gas exchange. PMID:26684839

  3. Au Nanocluster assisted PCE improvement in PEDOT: PSS - Si Hybrid Devices

    NASA Astrophysics Data System (ADS)

    Sharma, Manisha; Pudasaini, Pushpa Raj; Ayon, Arturo A.

    2015-03-01

    Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a P-type organic polymer is frequently employed in the fabrication of heterojunction p-n solar cell devices due to its proper HOMO-LUMO band gap as well as its tunable conductivity. In this report we describe the incorporation of gold (Au) nanoclusters in the PEDOT:PSS blend and its influence on the power-conversion-efficiency (PCE) on planar silicon (Si) hybrid heterojunction solar cell devices. Specifically, the reference samples without the aforementioned nanoclusters, were measured to exhibit a 6.10% PCE, value that increased to 7.55% upon the addition of the Au nanoclusters. The observed increase in the PCE is attributed to the enhanced electrical conductivity of the PEDOT:PSS films due to the incorporation of the nanoclusters, which is directly reflected in their improved fill factor. It is further theorized that the presence of Au nanoclusters in the insulating PSS layer in the PEDOT:PSS blend have a positive influence in the charge collection effectiveness of the devices produced. Considering that the Au nanoparticles involved in this research exercise had an average size of only 4 nm, it is considered that plasmonic effects did not play a relevant role in the observed PCE improvement.

  4. Crystallization and preliminary X-ray diffraction studies of the pneumococcal teichoic acid phosphorylcholine esterase Pce

    SciTech Connect

    Lagartera, Laura; González, Ana; Stelter, Meike; García, Pedro; Kahn, Richard; Menéndez, Margarita; Hermoso, Juan A.

    2005-02-01

    The modular choline-binding protein Pce, the phosphorylcholine esterase from S. pneumoniae, has been crystallized by the hanging-drop vapour-diffusion method. A SAD data set from a derivative with a gadolinium complex has been collected to 2.7 Å resolution.

  5. FIELD MEASUREMENT OF VAPOR INTRUSION RATES AT A PCE SITE (ABSTRACT ONLY)

    EPA Science Inventory

    A field study was performed to evaluate vapor intrusion (VI) of tetrachloroethylene (PCE) and other chlorinated solvents at a commercial retail site in Dallas, TX. The building is approximately 40 years old and once housed a dry cleaning operation. Results from an initial site ch...

  6. Hydration of alumina cement containing ferrotitanium slag with polycarboxylate-ethers (PCE) additives

    NASA Astrophysics Data System (ADS)

    Rechkalov, Denis; Chernogorlov, Sergey; Abyzov, Victor

    2016-01-01

    The paper is discussing results of study of alumina binder containing aluminous cement and ferrotitanium slag from aluminothermic process by Kliuchevskoi Ferroalloys corp. with various additives containing polycarboxylate-ethers (PCE). Selecting ferrotitanium slag as additive is based on the fact that its content of alumina and phase composition is closest to the alumina cement. The composition of the ferrotitanium slag is displayed. In order to compensate the decrease in strength caused by addition of ferrotitanium slag having low activity, PCE additives were added. As PCE additives were used Melflux 1641F, Melflux 2651F and Melflux PP200F by BASF. The effect of additives on the hydration of the binder, depending on the amount and time of additives hardening is shown. The composition of the hydration products in the cement was studied by physico-chemical analysis: derivatography and X-ray analysis. It is found that in the early stages of hardening PCE additives have inhibitory effect on hydration processes and promote new phase amorphization. The optimal content of additives was investigated. The basic properties of the binders have been tested. It was observed that the modified binders meet the requirements of Russian National State Standard GOST 969 to the alumina cement.

  7. Sewer Gas: An Indoor Air Source of PCE to Consider During Vapor Intrusion Investigations

    PubMed Central

    Pennell, Kelly G.; Scammell, Madeleine Kangsen; McClean, Michael D.; Ames, Jennifer; Weldon, Brittany; Friguglietti, Leigh; Suuberg, Eric M.; Shen, Rui; Indeglia, Paul A.; Heiger-Bernays, Wendy J.

    2013-01-01

    The United States Environmental Protection Agency (USEPA) is finalizing its vapor intrusion guidelines. One of the important issues related to vapor intrusion is background concentrations of volatile organic chemicals (VOCs) in indoor air, typically attributed to consumer products and building materials. Background concentrations can exist even in the absence of vapor intrusion and are an important consideration when conducting site assessments. In addition, the development of accurate conceptual models that depict pathways for vapor entry into buildings is important during vapor intrusion site assessments. Sewer gas, either as a contributor to background concentrations or as part of the site conceptual model, is not routinely evaluated during vapor intrusion site assessments. The research described herein identifies an instance where vapors emanating directly from a sanitary sewer pipe within a residence were determined to be a source of tetrachloroethylene (PCE) detected in indoor air. Concentrations of PCE in the bathroom range from 2.1 to 190 ug/m3 and exceed typical indoor air concentrations by orders of magnitude resulting in human health risk classified as an “Imminent Hazard” condition. The results suggest that infiltration of sewer gas resulted in PCE concentrations in indoor air that were nearly two-orders of magnitude higher as compared to when infiltration of sewer gas was not known to be occurring. This previously understudied pathway whereby sewers serve as sources of PCE (and potentially other VOC) vapors is highlighted. Implications for vapor intrusion investigations are also discussed. PMID:23950637

  8. Effects of pure and dyed PCE on physical and interfacial properties of remedial solutions.

    PubMed

    Jeong, Seung-Woo; Wood, A Lynn; Lee, Tony R

    2002-11-11

    Hydrophobic dyes have been used to visually distinguish dense non-aqueous phase liquid (DNAPL) contaminants from background aqueous phases and soils. The objective of this study was to evaluate the effects of a dyed DNAPL, 0.5 g Oil-Red-O/l of PCE, on the physical properties of remedial solutions: water, co-solvents (50, 70, and 90% (v/v) ethanol), and surfactants (4% (w) sodium dihexyl sulfosuccinate). This study compared the densities, viscosities, and interfacial tensions (IFTs) of the remedial solutions in contact with both dyed and undyed PCE. The presence of the dye in PCE substantially alters the IFTs of water and ethanol solutions, while there is no apparent difference in IFTs of surfactant solutions. The remedial solutions saturated with PCE showed higher viscosities and densities than pure remedial solutions. Solutions with high ethanol content exhibited the largest increases in liquid density. Because physical properties affect the flow of the remedial solutions in porous media, experiments using dyed DNAPLs should assess the influence of dyes on fluid and interfacial properties prior to remediation process analysis. PMID:12409243

  9. PCE/K-10 Activities for Career Education, Grades 4-6.

    ERIC Educational Resources Information Center

    Portland Public Schools, OR. Area II Office.

    The Portland (Oregon) Public School Project Career Education (PCE) Activities for grades 4-6 is based on the city's overall Area 2 program goals for career education which proposed that children completing school should have sufficient knowledge and competencies to enter into a field of employment or an advanced training program in that field.…

  10. Adult Neuropsychological Performance Following Prenatal and Early Postnatal Exposure to Tetrachloroethylene (PCE)-contaminated Drinking Water

    PubMed Central

    Janulewicz, Patricia A; White, Roberta F; Martin, Brett M; Winter, Michael R; Weinberg, Janice M; Vieira, Veronica; Aschengrau, Ann

    2012-01-01

    This population-based retrospective cohort study examined adult performance on a battery of neuropsychological tests in relation to prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using pipe network information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Results of crude and multivariate analyses among 35 exposed and 28 unexposed subjects showed no association between prenatal and early postnatal exposure and decrements on tests that assess abilities in the domains of omnibus intelligence, academic achievement or language. The results were suggestive of an association between prenatal and early postnatal PCE exposure and diminished performance on tests that assessed abilities in the domains of visuospatial functioning, learning and memory, motor, attention and mood. Because the sample size was small, most findings were not statistically significant. Future studies with larger sample sizes should be conducted to further define the neuropsychological consequences of early developmental PCE exposure. PMID:22522125

  11. Characterization of Microbial Communities in TCE-Contaminated Seep Zone Sediments

    SciTech Connect

    ROBIN, BRIGMON

    2005-03-07

    Hundreds of sites across the United States contain trichloroethene (TCE) contamination, including the Department of Energy's Savannah River Site (SRS) in Aiken, South Carolina. Previous studies have indicated that microorganisms are capable of efficiently degrading TCE to nonhazardous end products. In this project, molecular and growth based methods were used for microbial characterization of a TCE impacted seepzone where TCE degradation is naturally occurring. The results from this work provide clear evidence that the SRB may play a significant role in TCE degradation along the Twin Lakes seepline.

  12. DEPENDENCE OF A HIGH-RATE, PCE-DECHLORINATING ENRICHMENT CULTURE ON METHANOGENIC ACTIVITY. (R825549C053)

    EPA Science Inventory

    The role served by the presence of methanogenic activity within a tetrachloroethene (PCE)-dechlorinating culture was investigated through a series of supplementation experiments. An acclimated lactate-enrichment culture (LEC 1) capable of rapidly converting PCE to ethene was s...

  13. Use of enrichments and nucleic acid probes in monitoring bioremediation of a deep trichloroethylene plume

    SciTech Connect

    Brockman, F.; Payne, W.; Workman, D.; Soong, A.; Manley, S.; Sun, W.; Ogram, A.

    1994-12-31

    The field site was manipulated with injection of air (control experiment), 1% methane (in air), pulsing of air only and 4% methane, and pulsing of 4% methane supplemented with gaseous forms of nitrogen and phosphorus. Gases were injected through a horizontal well into the aquifer and a vacuum was established in a second horizontal well in the vadose zone. Following each injection regime, sediment samples from the contaminated region were analyzed. Analyses included most-probable-number enrichments for physiological groups known or suspected to degrade trichloroethylene (TCE) and per-chloroethylene (PCE), TCE and PCE removal from enrichments, and DNA extraction and hybridization with various gene probes corresponding to enzymes known to degrade TCE or TCE metabolites.

  14. Quantification of potassium permanganate consumption and PCE oxidation in subsurface materials

    NASA Astrophysics Data System (ADS)

    Hønning, J.; Broholm, M. M.; Bjerg, P. L.

    2007-03-01

    A series of laboratory scale batch slurry experiments were conducted in order to establish a data set for oxidant demand by sandy and clayey subsurface materials as well as to identify the reaction kinetic rates of permanganate (MnO 4-) consumption and PCE oxidation as a function of the MnO 4- concentration. The laboratory experiments were carried out with 31 sandy and clayey subsurface sediments from 12 Danish sites. The results show that the consumption of MnO 4- by reaction with the sediment, termed the natural oxidant demand (NOD), is the primary reaction with regards to quantification of MnO 4- consumption. Dissolved PCE in concentrations up to 100 mg/l in the sediments investigated is not a significant factor in the total MnO 4- consumption. Consumption of MnO 4- increases with an increasing initial MnO 4- concentration. The sediment type is also important as NOD is (generally) higher in clayey than in sandy sediments for a given MnO 4- concentration. For the different sediment types the typical NOD values are 0.5-2 g MnO 4-/kg dry weight (dw) for glacial meltwater sand, 1-8 g MnO 4-/kg dw for sandy till and 5-20 g MnO 4-/kg dw for clayey till. The long term consumption of MnO 4- and oxidation of PCE can not be described with a single rate constant, as the total MnO 4- reduction is comprised of several different reactions with individual rates. During the initial hours of reaction, first order kinetics can be applied, where the short term first order rate constants for consumption of MnO 4- and oxidation of PCE are 0.05-0.5 h - 1 and 0.5-4.5 h - 1 , respectively. The sediment does not act as an instantaneous sink for MnO 4-. The consumption of MnO 4- by reaction with the reactive species in the sediment is the result of several parallel reactions, during which the reaction between the contaminant and MnO 4- also takes place. Hence, application of low MnO 4- concentrations can cause partly oxidation of PCE, as the oxidant demand of the sediment does not need

  15. Enhanced Reductive Dechlorination of TCE in a Basalt Aquifer

    SciTech Connect

    K. S. Sorenson; L. N. Peterson; R. Ely

    1999-04-01

    A field evaluation of enhanced reductive dechlorination of trichloroethene (TCE) in groundwater has been in progress since November 1998 to determine whether in situ biodegradation can be significantly enhanced through the addition of an electron donor (lactate). An in situ treatment cell was established in the residual source area of a large TCE plume in a fractured basalt aquifer utilizing continuous ground water extraction approximately 150 meters downgradient of the injection location. After a 1-month tracer test and baseline sampling period, the pulsed injection of lactate was begun. Ground water samples were collected from 11 sampling points on a biweekly basis and in situ water quality parameters were recorded every 4 hours at two locations. Within 2 weeks after the initial lactate injection, dissolved oxygen and redox potential were observed to decrease substantially at all sampling locations within 40 m of the injection well. Decreases in nitrate and sulfate concentrations were also observed. Both quantitative in situ rate estimation methods and qualitative measures such as changes in redox conditions, decreases in chlorine number, and changes in biomass indicator parameters are being used throughout the test to evaluate the extent to which biodegradation of TCE is enhanced.

  16. Enhanced Reductive Dechlorination of TCE in a Basalt Aquifer

    SciTech Connect

    Sorenson, Kent Soren; Peterson, Lance Nutting; Ely, R. L.

    1999-04-01

    A field evaluation of enhanced reductive dechlorination of trichloroethene (TCE) in ground water has been in progress since November 1998 to determine whether in situ biodegradation can be significantly enhanced through the addition of an electron donor (lactate). An in situ treatment cell was established in the residual source area of a large TCE plume in a fractured basalt aquifer utilizing continuous ground water extraction approximately 150 meters downgradient of the injection location. After a 1-month tracer test and baseline sampling period, the pulsed injection of lactate was begun. Ground water samples were collected from 11 sampling points on a biweekly basis and in situ water quality parameters were recorded every 4 hours at two locations. Within 2 weeks after the initial lactate injection, dissolved oxygen and redox potential were observed to decrease substantially at all sampling locations within 40 m of the injection well. Decreases in nitrate and sulfate concentrations were also observed. Both quantitative in situ rate estimation methods and qualitative measures such as changes in redox conditions, decreases in chlorine number, and changes in biomass indicator parameters are being used throughout the test to evaluate the extent to which biodegradation of TCE is enhanced.

  17. A Planet Hunters Search of the Kepler TCE Inventory

    NASA Astrophysics Data System (ADS)

    Schwamb, Meg; Lintott, Chris; Fischer, Debra; Smith, Arfon; Boyajian, Tabetha; Brewer, John; Giguere, Matt; Lynn, Stuart; Schawinski, Kevin; Simpson, Rob; Wang, Ji

    2013-07-01

    NASA's Kepler spacecraft has spent the past 4 years monitoring ~160,000 stars for the signatures of transiting exoplanets. Planet Hunters (http://www.planethunters.org), part of the Zooniverse (http://www.zooniverse.org) collection of citizen science projects, uses the power of human pattern recognition via the World Wide Web to identify transits in the Kepler public data. We have demonstrated the success of a citizen science approach with the project's discoveries including PH1 b, a transiting circumbinary planet in a four star system., and over 20 previously unknown planet candidates. The Kepler team has released the list of 18,406 potential transit signals or threshold-crossing events (TCEs) identified in Quarters 1-12 (~1000 days) by their automated Transit Planet Search (TPS) algorithm. The majority of these detections found by TPS are triggered by transient events and are not valid planet candidates. To identify planetary candidates from the detected TCEs, a human review of the validation reports, generated by the Kepler pipeline for each TCE, is performed by several Kepler team members. We have undertaken an independent crowd-sourced effort to perform a systematic search of the Kepler Q1-12 TCE list. With the Internet we can obtain multiple assessments of each TCE's data validation report. Planet Hunters volunteers evaluate whether a transit is visible in the Kepler light curve folded on the expected period identified by TPS. We present the first results of this analysis.

  18. Hydrogeologic investigation of the Malvern TCE Superfund Site, Chester County, Pennsylvania

    USGS Publications Warehouse

    Sloto, Ronald A.

    1997-01-01

    The Malvern TCE Superfund Site, a former solvent recycling facility that now stores and sells solvents, consists of a plant and disposal area, which are approximately 1,900 ft (feet) apart. The site is underlain by an unconfined carbonate bedrock aquifer in which permeability has been enhanced in places by solution. Water levels respond quickly to precipitation and show a similar seasonal variation, response to precipitation, and range of fluctuation. The altitude of water levels in wells at the disposal area is nearly identical because of the small hydraulic gradient. A comparison of water-table maps for 1983, 1993, and 1994 shows that the general shape of the water table and hydraulic gradients in the area have remained the same through time and for different climatic conditions. The plant area is underlain by dolomite of the Elbrook Formation. The dolomite at the plant area does not yield as much water as the dolomite at the disposal area because it is less fractured, and wells penetrate few water-bearing fractures. Yields of nine wells at the plant area range from 1 to 200 gal/min (gallons per minute); the median yield is 6 gal/min. Specific capacities range from 0.08 to 2 (gal/min)/ft (gallons per minute per foot). Aquifer tests were conducted in two wells; median transmissivities estimated from the aquifer-test data ranged from 528 to 839 feet squared per day. Maximum concentrations of volatile organic compounds (VOC's) in ground water at the plant area in 1996 were 53,900 ug/L (micrograms per liter) for trichloroethylene (TCE), 7,110 ug/L for tetrachloroethylene (PCE), and 17,700 ug/L for 1,1,1-trichloroethane (TCA). A ground-water divide is located between the plant area and the disposal area. Ground-water withdrawal for dewatering the Catanach quarry has caused a cone of depression in the water-table surface that reaches to the plant area. From the plant area, ground water flows 1.2 miles to the northeast and discharges to the Catanach quarry. The regional

  19. Bacteria associated with oak and ash on a TCE-contaminated site: Characterization of isolates with potential to avoid evapotranspiration of TCE

    SciTech Connect

    Weyens, N.; van der Lelie, D.; Taghavi, S.; Barac, T.; Boulet, J.; Artois, T.; Carleer, R.; Vangronsveld, J.

    2009-11-01

    Along transects under a mixed woodland of English Oak (Quercus robur) and Common Ash (Fraxinus excelsior) growing on a trichloroethylene (TCE)-contaminated groundwater plume, sharp decreases in TCE concentrations were observed, while transects outside the planted area did not show this remarkable decrease. This suggested a possibly active role of the trees and their associated bacteria in the remediation process. Therefore, the cultivable bacterial communities associated with both tree species growing on this TCE-contaminated groundwater plume were investigated in order to assess the possibilities and practical aspects of using these common native tree species and their associated bacteria for phytoremediation. In this study, only the cultivable bacteria were characterized because the final aim was to isolate TCE-degrading, heavy metal resistant bacteria that might be used as traceable inocula to enhance bioremediation. Cultivable bacteria isolated from bulk soil, rhizosphere, root, stem, and leaf were genotypically characterized by amplified rDNA restriction analysis (ARDRA) of their 16S rRNA gene and identified by 16S rRNA gene sequencing. Bacteria that displayed distinct ARDRA patterns were screened for heavy metal resistance, as well as TCE tolerance and degradation, as preparation for possible future in situ inoculation experiments. Furthermore, in situ evapotranspiration measurements were performed to investigate if the degradation capacity of the associated bacteria is enough to prevent TCE evapotranspiration to the air. Between both tree species, the associated populations of cultivable bacteria clearly differed in composition. In English Oak, more species-specific, most likely obligate endophytes were found. The majority of the isolated bacteria showed increased tolerance to TCE, and TCE degradation capacity was observed in some of the strains. However, in situ evapotranspiration measurements revealed that a significant amount of TCE and its metabolites

  20. Experimental Results on the Destruction of PCE using a Photo-Chemical Remediation Reactor

    NASA Astrophysics Data System (ADS)

    Lee, J. J.; Lee, K. Y.; Stencel, J. R.; Khinast, J.

    2001-12-01

    A vapor-phase tetrachloroethylene (PCE) destruction experiment using a newly constructed photo-chemical remediation (PCR) reactor is performed. One of the applications for the PCR reactor is subsurface remediation of volatile organic compounds (VOCs). Ultraviolet (UV) light, when emitted at an effective absorption frequency (primary wavelengths of 185 and 254 nm), cleaves a VOC's carbon-chlorine bond thus reducing harmful contaminants to harmless products. The PCR reactor consists of a stainless steel tubular vessel with internal dimensions 0.32 m in diameter and 1.05 m in length. Sixteen Suprasil glass sleeves (Heraeus Inc.) with external dimensions of 25 mm in diameter and 1.1 m in length are inserted along the length of the reactor. The Suprasil sleeves are positioned in a geometrical pattern to provide maximum UV exposure. An amalgam UV lamp (Heraeus Inc. NIQ 200/110) is placed inside every Suprasil sleeve. Each UV lamp has its own igniter and ballast for versatile power control. The Suprasil sleeves provide barrier protection between the UV lamps and the vapor-phase contaminant, and at the same time allow transmission of UV light to the interior of the PCR reactor. A gas heater is installed to increase the influent vapor-phase temperature and the PCR reactor is insulated to minimize heat loss. However, the PCE destruction experiment is presently being performed without the aid of the gas heater. During the experiment, the PCR reactor temperature reached in excess of 200 degrees Celsius from heat generated from the UV lamps. Vapor-phase samples are collected at the influent and effluent reactor sampling ports prior and after UV lamp ignitions. Preliminary results show good PCE destruction efficiency for the range of influent PCE concentrations considered in this study.

  1. Abiotic dechlorination in rock matrices impacted by long-term exposure to TCE.

    PubMed

    Schaefer, Charles E; Towne, Rachael M; Lippincott, David R; Lacombe, Pierre J; Bishop, Michael E; Dong, Hailiang

    2015-01-01

    Field and laboratory tests were performed to evaluate the abiotic reaction of trichloroethene (TCE) in sedimentary rock matrices. Hydraulically conductive fractures, and the rock directly adjacent to the hydraulically conductive fractures, within a historically contaminated TCE bedrock aquifer were used as the basis for this study. These results were compared to previous work using rock that had not been exposed to TCE (Schaefer et al., 2013) to assess the impact of long-term TCE exposure on the abiotic dechlorination reaction, as the longevity of these reactions after long-term exposure to TCE was hitherto unknown. Results showed that potential abiotic TCE degradation products, including ethane, ethene, and acetylene, were present in the conductive fractures. Using minimally disturbed slices of rock core at and near the fracture faces, laboratory testing on the rocks confirmed that abiotic dechlorination reactions between the rock matrix and TCE were occurring. Abiotic daughter products measured in the laboratory under controlled conditions were consistent with those measured in the conductive fractures, except that propane also was observed as a daughter product. TCE degradation measured in the laboratory was well described by a first order rate constant through the 118-d study. Observed bulk first-order TCE degradation rate constants within the rock matrix were 1.3×10(-8) s(-1). These results clearly show that abiotic dechlorination of TCE is occurring within the rock matrix, despite decades of exposure to TCE. Furthermore, these observed rates of TCE dechlorination are expected to have a substantial impact on TCE migration and uptake/release from rock matrices. PMID:25192648

  2. Health-hazard evaluation report HETA 85-083-1705, Summit Finishing Company, Inc. , Mooresville, Indiana. [Perchloroethylene concentrations

    SciTech Connect

    Daniels, W.J.; Kramkowski, R.S.

    1986-06-01

    An evaluation of employee exposures to chemicals used in electroplating operations was made. At the time of the study there were 67 employees, about 26 of whom were involved directly in the production operations. Airborne concentrations of perchloroethylene did not exceed OSHA standards, but they did exceed the NIOSH recommended exposure level on both a ceiling and time weighted average basis. Environmental samples collected for cyanides, inorganic acids, metals, and formaldehyde were below their respective evaluation criteria at the time of the survey. The authors conclude that a potential health hazard existed from exposures to perchloroethlyene. A significant number of employees reported acute mucous membrane irritation. The authors made recommendations.

  3. Spatial and temporal distributions of Geobacter lovleyi and Dehalococcoides spp. during bioenhanced PCE-NAPL dissolution.

    PubMed

    Amos, Benjamin K; Suchomel, Eric J; Pennell, Kurt D; Löffler, Frank E

    2009-03-15

    The spatial and temporal distributions of multiple reductively dechlorinating bacteria were simultaneously assessed in a one-dimensional sand column containing a tetrachloroethene (PCE) nonaqueous phase liquid (NAPL) source and associated plume zones. The column was uniformly inoculated with a PCE-to-ethene dechlorinating microbial consortium that contained Dehalococcoides spp., Dehalobacter spp., and Geobacter lovleyi strain SZ. Geobacter and Dehalococcoides populations grew and colonized the column material, including the mixed-NAPL (0.25 mol/mol PCE in hexadecane) source zone. In contrast, Dehalobacter cells did not colonize the porous column material, and planktonic Dehalobacter cell titers remained below the detection limit of ca. 2.6 x 10(2) cells/mL throughout the experiment. Significant PCE dechlorination was observed and resulted in bioenhanced NAPL dissolution up to 21-fold (maximum) and 5.2-fold (cumulative) relative to abiotic dissolution. cis-1,2-Dichloroethene (cis-DCE) wasthe primary dechlorination product although vinyl chloride (VC) was also formed throughout the experiment. Ethene production occurred after significant depletion of PCE from the NAPL and when cis-DCE concentrations dropped below 6 microM. Data obtained after increasing the column residence time from 1.1 to 2.8 days and introducing a VC pulse to the column indicated that both the residence time and cis-DCE inhibition limited significant VC and ethene production. Although both Geobacter and Dehalococcoides cells were present and active in the mixed-NAPL source zone and plume region, Geobacter cell numbers were typically more than 1 order of magnitude higher than Dehalococcoides cell numbers, which is consistent with the production of predominantly cis-DCE. Analysis of both liquid- and solid-phase samples indicated that Geobacter cells grew and remained attached to the porous medium within the source zone but were largely planktonic in the plume region. In contrast Dehalococcoides cell

  4. Innovative treatment for TCE-contaminated saturated clay soils

    SciTech Connect

    West, O.R.; Cameron, P.A.; Smuin, D.R.

    1995-12-31

    This paper describes the evaluation of mixed region vapor stripping (MRVS) coupled with calcium oxide conditioning for removing trichloroethylene (TCE) for a site underlain by saturated clay soils. Volatile organic compound removal during MRVS with and without calcium oxide conditioning were simulated using a previously developed model. The results of the modeling were compared with laboratory MRVS tests on undisturbed soil cores taken from the study site. The modeling results were consistent with laboratory simulations of MRVS on field-contaminated soils from the study site, and showed that calcium oxide conditioning is an effective method for enhancing VOC removal efficiencies in saturated clay soils.

  5. Surfactant foam/bioaugmentation technology for in situ treatment of TCE-DNAPLs.

    SciTech Connect

    Rothmel, R. K.; Peters, R. W.; St. Martin, E.; Deflaun, M. F.; Energy Systems; Envirogen, Inc.

    1998-06-01

    Chlorinated solvents such as trichloroethylene (TCE) are prevalent aquifer contaminants. Depending on the degree of contamination, their physical properties may cause them to occur as dense nonaqueous-phase liquids (DNAPLs) making them difficult to remediate by pump-and-treat methods. Successful in situ bioremediation requires mobilization and dispersion of DNAPLs in order to reduce sediment concentrations to levels nontoxic to degradative bacteria. A bench-scale study was conducted to evaluate a novel remediation technology that utilized surfactant foam for mobilizing and dispersing TCE-DNAPLs combined with a bioaugmentation technology to remediate TCE in situ. Results using the anionic surfactant Steol CS-330 showed that foam injected into TCE-DNAPL-contaminated sand columns enhanced mobilization of TCE-DNAPLs. Mobilization was maximized when the foam was injected in a pulsed operation. Injection of foam followed by artificial groundwater (AGW) and then by foam again resulted in flushing 75% of the initial TCE-DNAPL through an 8-in. column (884 cm3 of sand). The residual TCE was dispersed within the column at concentration levels compatible with biodegradation (<500 {micro}g/g). Adding the TCE-degrading bacterial strain ENV 435 simultaneously with the second pulse of foam resulted in 95-99% degradation of the residual TCE. This level of remediation was achieved with a total of 3 pore volumes (foam/AGW/foam + bacteria) and an aqueous column retention time of 1 h.

  6. Laboratory study of air sparging of TCE-contaminated saturated soils and ground water

    SciTech Connect

    Adams, J.A.; Reddy, K.R.

    1999-06-30

    Air sparging has proven to be an effective remediation technique for treating saturated soils and ground water contaminated by volatile organic compounds (VOCs). Since little is known about the system variables and mass transfer mechanisms important to air sparging, several researchers have recently performed laboratory investigations to study such issues. This paper presents the results of column experiments performed to investigate the behavior of dense nonaqueous phase liquids (DNAPLs), specifically trichloroethylene (TCE), during air sparging. The specific objectives of the study were (1) to compare the removal of dissolved TCE with the removal of dissolved light nonaqueous phase liquids (LNAPLs), such as benzene or toluene; (2) to determine the effect of injected air-flow rate on dissolved TCE removal; (3) to determine the effect of initial dissolved TCE concentration on removal efficiency; and (4) to determine the differences in removal between dissolved and pure-chase TCE. The test results showed that (1) the removal of dissolved TCE was similar to that of dissolved LNAPL; (2) increased air-injection rates led to increased TCE removal at lower ranges of air injection, but further increases at higher ranges of air injection did not increase the rate of removal, indicating a threshold removal rate had been reached; (3) increased initial concentration of dissolved TCE resulted in similar rates of removal; and (4) the removal pf pure-phase TCE was difficult using a low air-injection rate, but higher air-injection rates led to easier removal.

  7. Steam and air co-injection in removing residual TCE in unsaturated layered sandy porous media

    NASA Astrophysics Data System (ADS)

    Peng, Sheng; Wang, Ning; Chen, Jiajun

    2013-10-01

    Steam and air co-injection is a promising technique for volatile and semi-volatile organic contaminant remediation in heterogeneous porous media. In this study, removal of trichloroethene (TCE) with steam-air co-injection was investigated through a series of 2D sandbox experiments with different layered sand structures, and through numerical simulations. The results show that a layered structure with coarse sand, in which steam and air convection are relatively rapid, resulted in a higher removal rate and a larger removal ratio than those observed in an experiment using finer sand; however, the difference was not significant, and the removal ratios from three experiments ranged from 85% to 94%. Slight downward movement of TCE was observed for Experiment 1 (TCE initially in a fine sand zone encased in a coarse sand), while no such movement was observed for Experiment 2 (TCE initially in two fine sand layers encased in a coarse sand) or 3 (TCE initially in a silty sand zone encased in a coarse sand). Simulations show accumulation of TCE at the interface of the layered sands, which indicates a capillary barrier effect in restraining the downward movement of TCE. This effect is illustrated further by a numerical experiment with homogeneous coarse sand, in which continuous downward TCE movement to the bottom of the sandbox was simulated. Another numerical experiment with higher water saturation was also conducted. The results illustrate a complicated influence of water saturation on TCE removal in a layered sand structure.

  8. Steam and air co-injection in removing residual TCE in unsaturated layered sandy porous media.

    PubMed

    Peng, Sheng; Wang, Ning; Chen, Jiajun

    2013-10-01

    Steam and air co-injection is a promising technique for volatile and semi-volatile organic contaminant remediation in heterogeneous porous media. In this study, removal of trichloroethene (TCE) with steam-air co-injection was investigated through a series of 2D sandbox experiments with different layered sand structures, and through numerical simulations. The results show that a layered structure with coarse sand, in which steam and air convection are relatively rapid, resulted in a higher removal rate and a larger removal ratio than those observed in an experiment using finer sand; however, the difference was not significant, and the removal ratios from three experiments ranged from 85% to 94%. Slight downward movement of TCE was observed for Experiment 1 (TCE initially in a fine sand zone encased in a coarse sand), while no such movement was observed for Experiment 2 (TCE initially in two fine sand layers encased in a coarse sand) or 3 (TCE initially in a silty sand zone encased in a coarse sand). Simulations show accumulation of TCE at the interface of the layered sands, which indicates a capillary barrier effect in restraining the downward movement of TCE. This effect is illustrated further by a numerical experiment with homogeneous coarse sand, in which continuous downward TCE movement to the bottom of the sandbox was simulated. Another numerical experiment with higher water saturation was also conducted. The results illustrate a complicated influence of water saturation on TCE removal in a layered sand structure. PMID:23962760

  9. Characterization of TCE DNAPL and Dissolved Phase Transport in Karst Media

    NASA Astrophysics Data System (ADS)

    Carmona, M.; Padilla, I. Y.

    2015-12-01

    Trichloroethylene (TCE) contaminated sites are a threat to the environment and human health. Of particular concerns is the contamination of karst groundwater systems (KGWSs). Their heterogeneous character, rapid flow through conduits, high permeability zones, and strong storage capacity in the rock porous-matrix pose a high risk of exposure over large areas and temporal scales. To achieve effective remedial actions for TCE removal, it is important to understand and quantify the fate and transport process of trichloroethylene in these systems. This research studies the fate, transport, and distribution of TCE Non-Aqueous Phase Liquids (NAPLs) and associated dissolved species in KGWSs. Experiments are conducted in a karstified limestone physical model, a limestone rock mimicking a saturated confined karst aquifer. After injecting TCE solvent into a steady groundwater flow field, samples are taken spatially and temporally and analyzed for TCE NAPL and dissolved phases. Data analysis shows the rapid detection of TCE NAPL and high aqueous concentrations along preferential pathway, even at distances far away from the injection point. Temporal distribution curves exhibit spatial variations related to the limestone rock heterogeneity. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response with long tailing indicates rate-limited diffusive transport in the rock matrix. Overall, results indicate that karstified limestone has a high capacity to rapidly transport pure and dissolved TCE along preferential flow paths, and to store and slowly release TCE over long periods of time.

  10. Biodegradation of high concentrations of tetrachloroethene in a continuous flow column system

    SciTech Connect

    Isalou, M; Sleep, B.E.; Liss, S.N.

    1998-11-15

    A long-term (2.5 years) study of the anaerobic biodegradation of high concentrations of perchloroethylene (PCE) was carried out in a continuously operated laboratory column filled with sand which was inoculated with biomass from an anaerobic digester. Concentrations of PCE fed to the column were increased from 12 {micro}M to over 600 {micro}M over 21 months, with methanol added as electron donor. Vinyl chloride (VC) was the terminal product of PCE dechlorination for the first 21 months at which point significant conversion of VC to ethylene (ETH) was detected. The onset of ETH production coincided with acetogenesis becoming the primary pathway for methanol metabolism. ETH production occurred in the column in the presence of PCE and TCE. Varying methanol:PCE molar ratios from 1.4 to 7.5 had little effect on the transformation of PCE and TCE to VC. The degradation of VC to ETH was much more sensitive, and VC accumulated when the methanol:PCE molar ratio dropped below 5.0. Withdrawal of PCE from the system for a 5 month period and maintenance of the column on methanol alone did not result in the loss of PCE degradation capability of the consortium.

  11. Inter-layer traffic engineering with hierarchical-PCE in MPLS-TP over wavelength switched optical networks.

    PubMed

    Casellas, R; Martinez, R; Muñoz, R; Liu, L; Tsuritani, T; Morita, I

    2012-12-31

    We present the implementation and validation of an Inter-layer Traffic Engineering (TE) architecture based on a hierarchical path computation element (PCE), where the parent PCE is notified of established optical layer Label Switched Paths that induce packet traffic engineering (TE) links, thus not requiring full topology visibility. We summarize the architecture, the control plane extensions and its experimental evaluation in a control plane testbed. PMID:23388738

  12. Functional Analysis of Esterase TCE2 Gene from Tetranychus cinnabarinus (Boisduval) involved in Acaricide Resistance

    PubMed Central

    Shi, Li; Wei, Peng; Wang, Xiangzun; Shen, Guangmao; Zhang, Jiao; Xiao, Wei; Xu, Zhifeng; Xu, Qiang; He, Lin

    2016-01-01

    The carmine spider mite, Tetranychus cinnabarinus is an important pest of crops and vegetables worldwide, and it has the ability to develop resistance against acaricides rapidly. Our previous study identified an esterase gene (designated TCE2) over-expressed in resistant mites. To investigate this gene’s function in resistance, the expression levels of TCE2 in susceptible, abamectin-, fenpropathrin-, and cyflumetofen-resistant strains were knocked down (65.02%, 63.14%, 57.82%, and 63.99%, respectively) via RNA interference. The bioassay data showed that the resistant levels to three acaricides were significantly decreased after the down-regulation of TCE2, indicating a correlation between the expression of TCE2 and the acaricide-resistance in T. cinnabarinus. TCE2 gene was then re-engineered for heterologous expression in Escherichia coli. The recombinant TCE2 exhibited α-naphthyl acetate activity (483.3 ± 71.8 nmol/mg pro. min−1), and the activity of this enzyme could be inhibited by abamectin, fenpropathrin, and cyflumetofen, respectively. HPLC and GC results showed that 10 μg of the recombinant TCE2 could effectively decompose 21.23% fenpropathrin and 49.70% cyflumetofen within 2 hours. This is the first report of a successful heterologous expression of an esterase gene from mites. This study provides direct evidence that TCE2 is a functional gene involved in acaricide resistance in T. cinnabarinus. PMID:26725309

  13. MICROFRACTURE SURFACE GEOCHEMISTRY AND ADHERENT MICROBIAL POPULATION METABOLISM IN TCE-CONTAMINATED COMPETENT BEDROCK

    EPA Science Inventory

    A TCE-contaminated competent bedrock site in Portsmouth, NH was used to determine if a relation existed between microfracture (MF) surface geochemistry and the ecology and metabolic activity of attached microbes relative to terminal electron accepting processes (TEAPs) and TCE bi...

  14. 77 FR 6863 - Proposed Collection; Comment Request for VITA/TCE Program Forms

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-09

    ... Internal Revenue Service Proposed Collection; Comment Request for VITA/TCE Program Forms AGENCY: Internal...(c)(2)(A)). Currently, the IRS is soliciting comments concerning VITA/TCE Program Forms 14310, 8653... 20224, or through the Internet, at Allan.M.Hopkins@irs.gov . SUPPLEMENTARY INFORMATION: Title:...

  15. 75 FR 22437 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-28

    ... were published in the Federal Register at 44 FR 72113 on December 13, 1979. Section 163 gives the IRS... Internal Revenue Service Tax Counseling for the Elderly (TCE) Program Availability of Application Packages... of the availability of Application Packages for the 2011 Tax Counseling for the Elderly (TCE)...

  16. PCE dechlorination by non-Dehalococcoides in a microbial electrochemical system.

    PubMed

    Yu, Jaecheul; Park, Younghyun; Nguyen, Van Khanh; Lee, Taeho

    2016-08-01

    The bioremediation of tetrachloroethene (perchloroethene; PCE) contaminated sites generally requires a supply of some fermentable organic substrates as an electron donor. On the other hand, organic substrates can induce the massive growth of microorganisms around the injection wells, which can foul the contaminated subsurface environment. In this study, PCE dechlorination to ethene was performed in a microbial electrochemical system (MES) using the electrode (a cathode polarized at -500 mV vs. standard hydrogen electrode) as the electron donor. Denaturing gel gradient electrophoresis and pyrosequencing revealed a variety of non-Dehalococcoides bacteria dominant in MES, such as Acinetobacter sp. (25.7 % for AS1 in suspension of M3), Rhodopseudomonas sp. (10.5 % for AE1 and 10.1 % for AE2 in anodic biofilm of M3), Pseudomonas aeruginosa (22.4 % for BS1 in suspension of M4), and Enterobacter sp. (21.7 % for BE1 in anodic biofilm of M4) which are capable of electron transfer, hydrogen production and dechlorination. The Dehalococcoides group, however, was not detected in this system. Therefore, these results suggest that a range of bacterial species outside the Dehalococcoides can play an important role in the microbial electrochemical dechlorination process, which may lead to innovative bioremediation technology. PMID:27271246

  17. Surfactant-enhanced remediation of a trichloroethene-contaminated aquifer. 2. Transport of TCE

    USGS Publications Warehouse

    Sahoo, D.; Smith, J.A.; Imbrigiotta, T.E.; Mclellan, H.M.

    1998-01-01

    Field studies were conducted under an induced gradient in a trichloroethene (TCE)-contaminated aquifer at Picatinny Arsenal, NJ, to study (a) the rate-limited desorption of TCE from aquifer sediments to water and (b) the effect of a surfactant (Triton X-100) on the desorption and transport of TCE. Clean water was injected into the contaminated aquifer for 206 day. Triton X-100 was added for a 36-day period (days 36-71 from the start of clean water injection). The effect of Triton X-100 on the desorption and transport of TCE in the field was examined by observing the concentrations of these two solutes in four monitoring wells 3-9 m from the injection wells. These data show a small but discernible increase in the TCE concentration in two of the wells corresponding approximately to the time when surfactant reaches the wells; in the other two monitoring wells, the increase in TCE concentration is negligible. A solute transport model that assumes local sorption equilibrium and used a laboratory-derived distribution coefficient could not adequately describe TCE desorption and transport observed in the aquifer. Two model formulations that accounted for rate-limited sorption - two-site and multisite models - fit the data well. TCE concentrations after surfactant injection were underpredicted by the models unless mass transfer rate was increased to account for the effect of surfactant on the rate of TCE desorption. The concentration data from the two wells and the model analysis suggest that the rate of TCE desorption is increased (by approximately 30%) as a result of Triton X-100 injection.Field studies were conducted under an induced gradient in a trichloroethene (TCE)-contaminated aquifer at Picatinny Arsenal, NJ, to study (a) the rate-limited desorption of TCE from aquifer sediments to water and (b) the effect of a surfactant (Triton X-100) on the desorption and transport of TCE. Clean water was injected into the contaminated aquifer for 206 day. Triton X-100 was added

  18. Health assessment for Keystone Hydraulics/J. W. Rex Company, Lansdale, Pennsylvania, Region 3. CERCLIS No. PAD980926976. Preliminary report

    SciTech Connect

    Not Available

    1988-05-04

    The Keystone Hydraulics/J. W. Rex Company Site has been listed on the National Priorities List. A metal heat-treating facility operated there from the 1940s until 1950. The Allied Paint Company then conducted operations until 1979. The site has been a construction equipment storage area since 1979. Identified contaminants of concern on-site include trichloroethylene (TCE), perchloroethylene (PCE), 1,1-dichloroethylene (1,1-DCE), cis-1,2-dichloroethylene (DCE), and vinyl chloride in well water. Identified soil contaminants include DCE, TCE, PCE, and vinyl chloride. Off-site contamination of groundwater by TCE and vinyl chloride has been found. The site is considered to be of potential public health concern because of the risk to human health caused by the possibility of exposure to hazardous substances via groundwater and soil.

  19. Tetrachloroethene metabolism of Dehalospirillum multivorans.

    PubMed

    Neumann, A; Scholz-Muramatsu, H; Diekert, G

    1994-01-01

    Dehalospirillum multivorans is a strictly anaerobic bacterium that is able to dechlorinate tetrachloroethene (perchloroethylene; PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) as part of its energy metabolism. The present communication describes some features of the dechlorination reaction in growing cultures, cell suspensions, and cell extracts of D. multivorans. Cell suspensions catalyzed the reductive dechlorination of PCE with pyruvate as electron donor at specific rates of up to 150 nmol (chloride released) min-1 (mg cell protein)-1 (300 microM PCE initially, pH 7.5, 25 degrees C). The rate of dechlorination depended on the PCE concentration; concentrations higher than 300 microM inhibited dehalogenation. The temperature optimum was between 25 and 30 degrees C; the pH optimum at about 7.5. Dehalogenation was sensitive to potential alternative electron acceptors such as fumarate or sulfur; nitrate or sulfate had no significant effect on PCE reduction. Propyl iodide (50 microM) almost completely inhibited the dehalogenation of PCE in cell suspensions. Cell extracts mediated the dehalogenation of PCE and of TCE with reduced methyl viologen as the electron donor at specific rates of up to 0.5 mumol (chloride released) min-1 (mg protein).-1 An abiotic reductive dehalogenation could be excluded since cell extracts heated for 10 min at 95 degrees C were inactive. The PCE dehalogenase was recovered in the soluble cell fraction after ultracentrifugation. The enzyme was not inactivated by oxygen. PMID:7802545

  20. Characterization of uranium surfaces machined with aqueous propylene glycol-borax or perchloroethylene-mineral oil coolants

    SciTech Connect

    Cristy, S.S.; Bennett, R.K. Jr.; Dillon, J.J.; Richards, H.L.; Seals, R.D.; Byrd, V.R.

    1986-12-31

    The use of perchloroethylene (perc) as an ingredient in coolants for machining enriched uranium at the Oak Ridge Y-12 Plant has been discontinued because of environmental concerns. A new coolant was substituted in December 1985, which consists of an aqueous solution of propylene glycol with borax (sodium tetraborate) added as a nuclear poison and with a nitrite added as a corrosion inhibitor. Uranium surfaces machined using the two coolants were compared with respects to residual contamination, corrosion or corrosion potential, and with the aqueous propylene glycol-borax coolant was found to be better than that of enriched uranium machined with the perc-mineral oil coolant. The boron residues on the final-finished parts machined with the borax-containing coolant were not sufficient to cause problems in further processing. All evidence indicated that the enriched uranium surfaces machined with the borax-containing coolant will be as satisfactory as those machined with the perc coolant.

  1. A study of the effect of perchloroethylene exposure on the reproductive outcomes of wives of dry-cleaning workers

    SciTech Connect

    Eskenazi, B.; Fenster, L.; Hudes, M.; Wyrobek, A.J.; Katz, D.F.; Gerson, J.; Rempel, D.M. )

    1991-01-01

    The purpose of this investigation was to compare the reproductive outcomes of wives of men exposed to perchloroethylene in the dry-cleaning industry compared to those of wives of laundry workers. Seventeen female partners of dry cleaners and 32 partners of laundry workers were interviewed. The number of pregnancies and the standardized fertility ratios were similar between the two groups. Wives of dry cleaners did not have higher rates of spontaneous abortions. However, wives of dry cleaners were more than twice as likely to have a history of attempting to become pregnant for more than 12 months or to have sought care for an infertility problem. Cox proportional hazards models indicated that dry-cleaners' wives had half of the per-cycle pregnancy rate of wives of laundry workers, when controlling for other potential confounders (estimated rate ratio of 0.54, 95% C.I. = 0.23, 1.27).

  2. Acetylene fuels reductive dechlorination of TCE by Dehalococcoides/Pelobacter-containing microbial consortia

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.; Mao, X.; Mahandra, C.; Baesman, S. M.; Gushgari, S.; Alvarez-Cohen, L.; Liu, T.

    2015-12-01

    Groundwater contamination by trichloroethene (TCE) poses a threat to health and leads to the generation of vinyl chloride (VC), a carcinogen. Dehalococcoides mccartyi is the only bacterium that can completely dechlorinate TCE to ethene (C2H4). Acetylene (C2H2) occurs in TCE-contaminated sites as a consequence of chemical degradation of TCE. Yet acetylene inhibits a variety of microbial processes including methanogesis and reductive dechlorination. Pelobacter acetylenicus and related species can metabolize acetylene via acetylene hydratase and acetaldehyde dismutatse thereby generating acetate and H2 as endproducts, which could serve as electron donor and carbon source for growth of D. mccartyi. We found that 1mM acetylene (aqueous) inhibits growth of D. mccartyi strain 195 on 0.3 mM TCE, but that the inhibition was removed after 12 days with the addition of an acetylene-utilizing isolate from San Francisco Bay, Pelobacter strain SFB93. TCE did not inhibit the growth of this Pelobacter at the concentrations tested (0.1-0.5 mM) and TCE was not consumed by strain SFB93. Co-cultures of strain 195 with strain SFB93 at 5% inoculation were established in 120 mL serum bottles containing 40 mL defined medium. TCE was supplied at a liquid concentration of 0.1 mM, with 0.1 mM acetylene and N2/CO2 (90:10 v/v) headspace at 34 °C. Co-cultures were subsequently transferred (5% vol/vol inoculation) to generate subcultures after 20 μmol TCE was reduced to VC and 36 μmol acetylene was depleted. Aqueous H2 ranged from 114 to 217 nM during TCE-dechlorination, and the cell yield of strain 195 was 3.7 ±0.3 × 107 cells μmol-1 Cl- released. In a D. mccartyi-containing enrichment culture (ANAS) under the same conditions as above, it was found that inhibition of dechlorination by acetylene was reversed after 19 days by adding SFB93. Thus we showed that a co-culture of Pelobacter SFB93 and D. mccartyi 195 could be maintained with C2H2 as the electron donor and carbon source while TCE

  3. A collision-aware backward recursive PCE-based computation algorithm in multi-domain optical networks

    NASA Astrophysics Data System (ADS)

    Xing, Jianchao; Zhang, Jie; Zhao, Yongli; Cao, Xuping; Wang, Dajiang; Gu, Wanyi

    2011-12-01

    The traditional approach for inter-domain Traffic Engineering Label Switching Path (TE-LSP) computation like BRPC could provide a shortest inter-domain constrained TE-LSP, but under wavelength continuity constraint, it couldn't guarantee the success of the resources reservation for the shortest path. In this paper, a Collision-aware Backward Recursive PCE-based Computation Algorithm (CA-BRPC) in multi-domain optical networks under wavelength continuity constraint is proposed, which is implemented based on Hierarchical PCE (H-PCE) architecture, could provide an optimal inter-domain TE-LSP and avoid resources reservation conflict. Numeric results show that the CA-BRPC could reduce the blocking probability of entire network.

  4. The PACSAT Communications Experiment (PCE). Final report, August 13, 1990--February 12, 1992

    SciTech Connect

    Not Available

    1993-02-12

    While VITA (Volunteers in Technical Assistance) is the recognized world leader in low earth orbiting (LEO) satellite technology (below 1 GHz), its involvement in communications technologies is to facilitate renewable energy technology transfer to developing countries. A communications payload was incorporated into the UoSat 2 satellite (Surrey Univ., UK), launched in 1984; a prototype satellite (PCE) was also launched Jan 1990. US DOE awarded a second grant to VITA to design and test the prototype ground stations (command and field), install field ground stations in several developing country sites, pursue the operational licensing process, and transfer the evaluation results to the design of an operating system. This report covers the principal tasks of this grant.

  5. Impacts of Residual Surfactant on Tetrachloroethene (PCE) Degradation Following Pilot-Scale SEAR Treatment at a Chloroethene-Impacted Site

    NASA Astrophysics Data System (ADS)

    Ramsburg, C. A.; Abriola, L. M.; Pennell, K. D.; Löffler, F. E.; Gamache, M.; Petrovskis, E. A.

    2003-04-01

    A pilot-scale surfactant-enhanced aquifer remediation (SEAR) demonstration was completed during the summer of 2000 at the Bachman Road site (Oscoda, MI USA). For this test, an aqueous solution of 60 g/L Tween 80 (polyoxyethylene (20) sorbitan monooleate) was used to recover tetrachloroethene (PCE) from a suspected source zone, located underneath a former dry-cleaning facility. Tween 80 was selected for use based upon its demonstrated capacity to solubilize PCE, “food-grade” status, and biodegradative potential. Hydraulic control was maintained throughout the test, with 95% of the injected surfactant mass recovered by a single extraction well. Source-zone monitoring conducted 15 months after SEAR treatment revealed the presence of previously undetected volatile fatty acids (acetate and formate) and PCE degradation products (trichloroethene, cis-1,2-dichloroethene, trans-1,2-dichlorethene, and vinyl chloride), in conjunction with PCE concentration reductions of approximately two orders-of-magnitude. The detection of volatile fatty acids is relevant, as they are likely fermentation products of residual Tween 80. Microbial reductive dechlorination is limited by available electron donors, and microcosm studies demonstrated that both acetate and formate support reductively dechlorinating populations present at the oligotrophic Bachman Road site aquifer. Surfactant transport simulations, using a regional flow model developed for the site, were employed to determine appropriate down-gradient monitoring locations. Drive point samples taken 15 months post-treatment in the vicinity of the simulated residual surfactant plume, contained elevated concentrations of acetate and PCE daughter products. Ongoing efforts include continued site-monitoring, and microcosm studies to corroborate a causal relationship between Tween 80 fermentation and PCE dechlorination.

  6. Factors Influencing TCE Anaerobic Dechlorination Investigated via Simulations of Microcosm Experiments

    NASA Astrophysics Data System (ADS)

    Mao, X.; Harkness, M.; Lee, M. D.; Mack, E. E.; Dworatzek, S.; Acheson, C.; McCarty, P.; Barry, D. A.; Gerhard, J. I.

    2006-12-01

    SABRE (Source Area BioREmediation) is a public-private consortium whose charter is to determine if enhanced anaerobic bioremediation can result in effective and quantifiable treatment of chlorinated solvent DNAPL source areas. The focus of this 4-year, $5.7 million research project is a field site in the United Kingdom containing a TCE DNAPL source area. In preparation, a microcosm study was performed to determine the optimal combination of factors to support reductive dechlorination of TCE in site soil and groundwater. The study consisted of 168 bottles distributed between four laboratories (Dupont, GE, SiREM, and Terra Systems) and tested the impact of six carbon substrates (lactate, acetate, methanol, SRS (soybean oil), hexanol, butyl acetate), bioaugmentation with KB-1 bacterial culture, three TCE levels (100 mg/L, 400 mg/L, and 800 mg/L) and two sulphate levels (200 mg/L, >500 mg/L) on TCE dechlorination. This research presents a numerical model designed to simulate the main processes occurring in the microcosms, including substrate fermentation, sequential dechlorination, toxic inhibition, and the influence of sulphate concentration. In calibrating the model to over 60 of the microcosm experiments, lumped parameters were employed to quantify the effect of key factors on the conversion rate of each chlorinated ethene in the TCE degradation sequence. Results quantify the benefit (i.e., increased stepwise dechlorination rate) due to both bioaugmentation and the presence of higher sulphate concentrations. Competitive inhibition is found to increase in significance as TCE concentrations increase; however, inclusion of Haldane inhibition is not supported. Over a wide range of experimental conditions and dechlorination steps, SRS appears to induce relatively little hydrogen limitation, thereby facilitating relatively quick conversion of TCE to ethene. In general, hydrogen limitation is found to increase with increasing TCE concentration and with bioaugmentation, and

  7. Use of emulsified vegetable oil to support bioremediation of TCE DNAPL in soil columns

    NASA Astrophysics Data System (ADS)

    Harkness, Mark; Fisher, Angela

    2013-08-01

    The interaction between emulsified vegetable oil (EVO) and trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) was observed using two soil columns and subsequent reductive dechlorination of TCE was monitored over a three year period. Dyed TCE DNAPL (~ 75 g) was emplaced in one column (DNAPL column), while the second was DNAPL-free (plume column). EVO was added to both columns and partitioning of the EVO into the TCE DNAPL was measured and quantified. TCE (1.9 mM) was added to the influent of the plume column to simulate conditions down gradient of a DNAPL source area and the columns were operated independently for more than one year, after which they were connected in series. Initially limited dechlorination of TCE to cDCE was observed in the DNAPL column, while the plume column supported complete reductive dechlorination of TCE to ethene. Upon connection and reamendment of the plume column with EVO, near saturation levels of TCE from the effluent of the DNAPL column were rapidly dechlorinated to c-DCE and VC in the plume column; however, this high rate dechlorination produced hydrochloric acid which overwhelmed the buffering capacity of the system and caused the pH to drop below 6.0. Dechlorination efficiency in the columns subsequently deteriorated, as measured by the chloride production and Dehalococcoides counts, but was restored by adding sodium bicarbonate buffer to the influent groundwater. Robust dechlorination was eventually observed in the DNAPL column, such that the TCE DNAPL was largely removed by the end of the study. Partitioning of the EVO into the DNAPL provided significant operational benefits to the remediation system both in terms of electron donor placement and longevity.

  8. A search for residual behavioral effects of trichloroethylene (TCE) in rats exposed as young adults.

    PubMed

    Oshiro, Wendy M; Krantz, Q Todd; Bushnell, Philip J

    2004-01-01

    Trichloroethylene (TCE) is an organic solvent with robust acute effects on the nervous system, but poorly documented long-term effects. This study employed a signal detection task (SDT) to assess the persistence of effects of repeated daily inhalation of TCE on sustained attention in rats. Adult male Long-Evans rats inhaled TCE at 0, 1600, or 2400 ppm, 6 h/day for 20 days (n=8/group) and began learning the SDT 3 weeks later. Rats earned food by pressing one retractable response lever in a signal trial and a second lever in a blank (no signal) trial. TCE did not affect acquisition of the response rule or performance of the SDT after the intertrial interval (ITI) was changed from a constant value to a variable one. Increasing the trial presentation rate reduced accuracy equivalently in all groups. Injections of ethanol (0, 0.5, 1.0, 1.5 g/kg ip) and d-amphetamine (0, 0.1, 0.3, 1.0 mg/kg sc) systematically impaired performance as functions of drug dose. d-Amphetamine (1.0 mg/kg) reduced P(hit) more in the 2400-ppm TCE group than in the other groups. All rats required remedial training to learn a reversal of the response contingencies, which TCE did not interfere with. Thus, a history of exposure to TCE did not significantly alter learning or sustained attention in the absence of drugs. Although ethanol did not differentially affect the TCE groups, the effect of d-amphetamine is consistent with solvent-induced changes in dopaminergic functions in the CNS. Calculations indicated power values of 0.5 to 0.8 to detect main effects of TCE for the three primary endpoints. PMID:15019957

  9. Improving the treatment of non-aqueous phase TCE in low permeability zones with permanganate.

    PubMed

    Chokejaroenrat, Chanat; Comfort, Steve; Sakulthaew, Chainarong; Dvorak, Bruce

    2014-03-15

    Treating dense non-aqueous phase liquids (DNAPLs) embedded in low permeability zones (LPZs) is a particularly challenging issue for injection-based remedial treatments. Our objective was to improve the sweeping efficiency of permanganate (MnO4(-)) into LPZs to treat high concentrations of TCE. This was accomplished by conducting transport experiments that quantified the penetration of various permanganate flooding solutions into a LPZ that was spiked with non-aqueous phase (14)C-TCE. The treatments we evaluated included permanganate paired with: (i) a shear-thinning polymer (xanthan); (ii) stabilization aids that minimized MnO2 rind formation and (iii) a phase-transfer catalyst. In addition, we quantified the ability of these flooding solutions to improve TCE destruction under batch conditions by developing miniature LPZ cylinders that were spiked with (14)C-TCE. Transport experiments showed that MnO4(-) alone was inefficient in penetrating the LPZ and reacting with non-aqueous phase TCE, due to a distinct and large MnO2 rind that inhibited the TCE from further oxidant contact. By including xanthan with MnO4(-), the sweeping efficiency increased (90%) but rind formation was still evident. By including the stabilization aid, sodium hexametaphosphate (SHMP) with xanthan, permanganate penetrated 100% of the LPZ, no rind was observed, and the percentage of TCE oxidized increased. Batch experiments using LPZ cylinders allowed longer contact times between the flooding solutions and the DNAPL and results showed that SHMP+MnO4(-) improved TCE destruction by ∼16% over MnO4(-) alone (56.5% vs. 40.1%). These results support combining permanganate with SHMP or SHMP and xanthan as a means of treating high concentrations of TCE in low permeable zones. PMID:24491441

  10. Microbial community changes associated with a shift from reductive dechlorination of PCE to reductive dechlorination of cis-DCE and VC

    SciTech Connect

    Flynn, S.J.; Loeffler, F.E.; Tiedje, J.M.

    2000-03-15

    Subcultures that reductively dechlorinate cis-dichloroethene (cis-DCE) or vinyl chloride (VC) were derived from three independent enrichments that completely dechlorinated tetrachloroethene (PCE) to ethene in order to study the reductive dechlorination of the lesser chlorinated ethenes. These subcultures completely dechlorinated cis-DCE and VC and could be transferred indefinitely in basal salts minimal medium with H{sub 2} as the electron donor. After 10 transfers (1% V/V) the cis-DCE and VC-dechlorinating subcultures from two of the PCE enrichments failed to dechlorinate PCE, but the subcultures from the third PCE enrichment maintained the ability to dechlorinate PCE. Analysis of the 16S rRNA genes from these enrichments by terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE) demonstrated shifts in the community composition of the subcultures that had lost the PCE-dechlorinating activity but not in the subcultures that maintained the PCE-dechlorinating activity. Analysis of the changes in community composition of the different enrichments suggested that at least two populations were responsible for the sequential dechlorination of PCE to ethene in these cultures and that consortia can cooperate in the complete dechlorination of PCE.

  11. Solubilities of Toluene, Benzene and TCE in High-Biomass Systems

    SciTech Connect

    Barton, John W.; Vodraska, Christopher D; Flanary, Sandie A.; Davison, Brian H

    2008-01-01

    We report measurements of solubility limits for benzene, toluene, and TCE in systems that contain varying levels of biomass up to 0.13 g/mL. The solubility limit increased from 20 to 48 mM when biomass (in the form of yeast) was added to aqueous batch systems containing benzene. The toluene solubility limit increased from 4.9 to greater than 20 mM. For TCE, the solubility increased from 8 mM to more than 1000 mM. Solubility for TCE was most heavily impacted by biomass levels, changing by two orders of magnitude.

  12. Health assessment for Whitehall Wells, Whitehall, Michigan, Region 5. CERCLIS No. MID980701254. Preliminary report

    SciTech Connect

    Not Available

    1989-04-14

    The Whitehall Wells (WW) are listed on the National Priorities List. Tap water in Whitehall City was found to contain 4 ppb of perchloroethylene (PCE). Two of the city's five production wells contained up to 6 ppb PCE, and nearby monitor wells contained up to 5 ppb 1,1-dichloroethane, 68 ppb trichloroethylene (TCE), 28 ppb chloroform, and 474 ppb cis-1,2-dichloroethylene. Analysis of soil, surface water, and especially ground water within the City of Whitehall clearly demonstrate the presence of chemical contaminants in the environment. The site is of potential public health concern because of the risk to human health that could result from possible exposure to hazardous substances at levels that may result in adverse health effects over time; human exposure to perchloroethylene has occurred via ground water.

  13. Laboratory evaluation of a two-stage treatment system for TCE cometabolism by a methane-oxidizing mixed culture

    SciTech Connect

    Smith, L.H.; McCarty, P.L.

    1997-08-20

    The objective of this research was to evaluate several factors affecting the performance of a two-stage treatment system employing methane-oxidizing bacteria for trichloroethylene (TCE) biodegradation. The system consists of a completely mixed growth reactor and a plug-flow transformation reactor in which the TCE is cometabolized. Laboratory studies were conducted with continuous growth reactors and batch experiments simulating transformation reactor conditions. Performance was characterized in terms of TCE transformation capacity (T{sub C}, g TCE/g cells), transformation yield (T{sub Y}, g TCE/g CH{sub 4}), and the rate coefficient ratio k{sub TCE}/K{sub S,TCE} (L/mg-d). The growth reactor variables studied were solids retention time (SRT) and nutrient nitrogen (N) concentration. Formate and methane were evaluated as potential transformation reactor amendments.

  14. Highly organic natural media as permeable reactive barriers: TCE partitioning and anaerobic degradation profile in eucalyptus mulch and compost.

    PubMed

    Öztürk, Zuhal; Tansel, Berrin; Katsenovich, Yelena; Sukop, Michael; Laha, Shonali

    2012-10-01

    Batch and column experiments were conducted with eucalyptus mulch and commercial compost to evaluate suitability of highly organic natural media to support anaerobic decomposition of trichloroethylene (TCE) in groundwater. Experimental data for TCE and its dechlorination byproducts were analyzed with Hydrus-1D model to estimate the partitioning and kinetic parameters for the sequential dechlorination reactions during TCE decomposition. The highly organic natural media allowed development of a bioactive zone capable of decomposing TCE under anaerobic conditions. The first order TCE biodecomposition reaction rates were 0.23 and 1.2d(-1) in eucalyptus mulch and compost media, respectively. The retardation factors in the eucalyptus mulch and compost columns for TCE were 35 and 301, respectively. The results showed that natural organic soil amendments can effectively support the anaerobic bioactive zone for remediation of TCE contaminated groundwater. The natural organic media are effective environmentally sustainable materials for use in permeable reactive barriers. PMID:22795070

  15. In-situ bioremediation of TCE-contaminated groundwater

    SciTech Connect

    Travis, B.J.; Rosenberg, N.D.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). A barrier to wider use of in situ bioremediation technology is that results are often variable and difficult to predict. In situ bioremediation has shown some very notable and well publicized successes, but implementation of the technology is complex. An incomplete understanding of the effects of variable site characteristics and the lack of adequate tools to predict and measure success have made the design, control and validation of bioremediation more empirical than desired. The long-term objective of this project is to improve computational tools used to assess and optimize the expected performance of bioremediation at a site. An important component of the approach is the explicit inclusion of uncertainties and their effect on the end result. The authors have extended their biokinetics model to include microbial competition and predation processes. Predator species can feed on the microbial species that degrade contaminants, and the simulation studies show that species interactions must be considered when designing in situ bioremediation systems. In particular, the results for TCE indicate that protozoan grazing could reduce the amount of biodegradation by about 20%. These studies also indicate that the behavior of barrier systems can become complex due to predator grazing.

  16. Field testing solar photocatalytic detoxification on TCE-contaminated groundwater

    SciTech Connect

    Mehos, M.S.; Turchi, C.S. )

    1993-08-01

    The Solar Detoxification Field Experiment was designed to investigate the photocatalytic decomposition of organic contaminants in groundwater at a Superfund site at Lawrence Livermore National Laboratory. The process uses ultraviolet (UV) energy available in sunlight in conjunction with a photocatalyst, titanium dioxide, to decompose organic chemicals into nontoxic compounds. The destruction mechanism, as in many other advanced oxidation processes, involves hydroxyl radicals. The field experiment was developed by three federal laboratories: The National Renewable Energy Laboratory, Sandia National Laboratory, and Lawrence Livermore National Laboratory. The United States Department of Energy funded the experiment. Groundwater at the test site was contaminated with trichloroethylene (TCE). A factorial test series examined four separate process variables: pH, catalyst loading, flow velocity, and solar intensity. Lowering the pH from pH 7 to pH 5 had the largest single effect, presumably by minimizing interference by bicarbonate. The catalyst was found to operate more efficiently at low, e.g. ambient sunlight, UV light levels. Information from these field tests suggest that treatment costs for the solar process would be similar to those for more conventional technologies. 8 refs., 10 figs., 4 tabs.

  17. IDENTIFICATION OF CHLOROMETHANE FROMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

    EPA Science Inventory

    The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

  18. IDENTIFICATION OF CHLOROMETHANE FORMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

    EPA Science Inventory

    The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

  19. UNCERTAINTY ANALYSIS OF TCE USING THE DOSE EXPOSURE ESTIMATING MODEL (DEEM) IN ACSL

    EPA Science Inventory

    The ACSL-based Dose Exposure Estimating Model(DEEM) under development by EPA is used to perform art uncertainty analysis of a physiologically based pharmacokinetic (PSPK) model of trichloroethylene (TCE). This model involves several circulating metabolites such as trichloroacet...

  20. Comparative phylogenetic microarray analysis of microbial communities in TCE-contaminated soils.

    PubMed

    Nemir, Audra; David, Maude M; Perrussel, Ronan; Sapkota, Amy; Simonet, Pascal; Monier, Jean-Michel; Vogel, Timothy M

    2010-07-01

    The arrival of chemicals in a soil or groundwater ecosystem could upset the natural balance of the microbial community. Since soil microorganisms are the first to be exposed to the chemicals released into the soil environment, we evaluated the use of a phylogenetic microarray as a bio-indicator of community perturbations due to the exposure to trichloroethylene (TCE). The phylogenetic microarray, which measures the presence of different members of the soil community, was used to evaluate unpolluted soils exposed to TCE as well as to samples from historically TCE polluted sites. We were able to determine an apparent threshold at which the microbial community structure was significantly affected (about 1ppm). In addition, the members of the microbial community most affected were identified. This approach could be useful for assessing environmental impact of chemicals on the biosphere as well as important members of the microbial community involved in TCE degradation. PMID:20444493

  1. Comparison of TCeMA and TDMA for Inter-Satellite Communications using OPNET Simulation

    NASA Technical Reports Server (NTRS)

    Hain, Regina Rosales; Ramanathan, Ram; Bergamo, Marcos; Wallett, Thomas M.

    2003-01-01

    A robust data link protocol, enabling unique physical and MAC layer technologies and sub-network level protocols, is needed in order to take advantage of the full potential of using both TDMA and CDMA in a satellite communication network. A novel MAC layer protocol, TDMA with CDMA-encoding multiple access (TCeMA) integrated with null-steered digital beam-forming spatial multiplexing, is investigated to support flexible spacecraft communications. Abstract models of the TCeMA and TDMA processes are developed in OPNFiT and a comparison of the performances of TCeMA and TDMA in a satellite network simulation are made. TCeMA provides the better connectivity and capacity with respect to TDMA for satellite communication traffic.

  2. Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination

    SciTech Connect

    Weyens, N.; van der Lelie, D.; Croes, S.; Dupae, J.; Newman, L.; Carleer, R.; Vangronsveld, J.

    2010-07-01

    The aim of this work was to investigate if engineered endophytes can improve phytoremediation of co-contaminations by organic pollutants and toxic metals. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive trichloroethylene (TCE) degradation, and (b) the ncc-nre Ni resistance/sequestration system. Plants were exposed to Ni and TCE and (a) Ni and TCE phytotoxicity, (b) TCE degradation and evapotranspiration, and (c) Ni concentrations in the roots and shoots were determined. Inoculation with B. cepacia VM1468 resulted in decreased Ni and TCE phytotoxicity, as measured by 30% increased root biomass and up to 50% decreased activities of enzymes involved in anti-oxidative defence in the roots. In addition, TCE evapotranspiration showed a decreasing trend and a 5 times higher Ni uptake was observed after inoculation. Engineered endophytes can improve phytoremediation of mixed contaminations via enhanced degradation of organic contaminants and improved metal uptake and translocation.

  3. Effects of a nutrient-surfactant compound on solubilization rates of TCE

    SciTech Connect

    Gillespie, M.T.; Strong-Gunderson, J.M.

    1997-12-31

    BioTreat{trademark}, a commercially available nutrient-surfactant compound, was investigated for its ability to solubilize TCE. Potential mechanisms for enhancing biodegradation rates by the use of nutrient-surfactant mixtures are: increased solubilization of TCE into the aqueous phase, and increased nutrients for the bacteria and greater numbers of colony forming units (CFUs). In aqueous systems, no measured solubilization of 0.1 and 1.0 ppm TCE from the headspace into the liquid phase was observed with BioTreat added at concentrations <0.5%. However, at BioTreat concentrations in excess of the CMC (>0.5%), increased solubilization of TCE was measured. A second question was the nutrient effect of BioTreat on the growth of the TCE-degrading bacterium, Burkholderia cepacia G4 PR1{sub 301}. The added nutrients provided by BioTreat was evident and lead to increased cell numbers. The effect of BioTreat on the expression of ortho-monooxgenase, the enzyme necessary for TCE degradation by B. cepacia was also investigated. Enzyme expression as detected by a calorimetric assay was inhibited for BioTreat concentrations >0.05%. 17 refs., 5 figs., 3 tabs.

  4. [Steam and air co-injection in removing TCE in 2D-sand box].

    PubMed

    Wang, Ning; Peng, Sheng; Chen, Jia-Jun

    2014-07-01

    Steam and air co-injection is a newly developed and promising soil remediation technique for non-aqueous phase liquids (NAPLs) in vadose zone. In this study, in order to investigate the mechanism of the remediation process, trichloroethylene (TCE) removal using steam and air co-injection was carried out in a 2-dimensional sandbox with different layered sand structures. The results showed that co-injection perfectly improved the "tailing" effect compared to soil vapor extraction (SVE), and the remediation process of steam and air co-injection could be divided into SVE stage, steam strengthening stage and heat penetration stage. Removal ratio of the experiment with scattered contaminant area was higher and removal speed was faster. The removal ratios from the two experiments were 93.5% and 88.2%, and the removal periods were 83.9 min and 90.6 min, respectively. Steam strengthened the heat penetration stage. The temperature transition region was wider in the scattered NAPLs distribution experiment, which reduced the accumulation of TCE. Slight downward movement of TCE was observed in the experiment with TCE initially distributed in a fine sand zone. And such downward movement of TCE reduced the TCE removal ratio. PMID:25244869

  5. Modeling the uptake and transpiration of TCE using phreatophytic trees. Master`s Thesis

    SciTech Connect

    Wise, D.P.

    1997-12-01

    Phytoremediation is a recent addition to the numerous methods used today to remediate ground water contaminants. It is proving more effective and efficient compared to existing remediation techniques. The use of phreatophytes, or water seeking trees, has great potential for phytoremediation. These trees are fast growing, long lived, grow their roots down to the ground water table, transpire large amounts of water, and are proven to actively remove contaminants from the soil horizon. The purpose of this research is to develop quantitative concepts for understanding the dynamics of TCE uptake and transpiration by phreatophytic trees over a short rotation woody crop time frame. This will he done by constructing a system dynamics model of this process and running it over a wide range of conditions. This research will offer managers a tool to simulate long-term uptake and transpiration of TCE at potential sites. The results of this study indicate that TCE is actively removed from the soil horizon by phreatophytic trees and a significant proportion of this TCE is then transpired. Changes in soil horizon parameters, xylem flow rates, and variables in the uptake equation greatly influence TCE uptake rates as well as transpiration. Also, parameters used in equations representing flows in and out of the leaf greatly influence transpiration. Better understanding of these processes is essential for managers to accurately predict the amount of TCE removed and transpired during potential phytoremediation projects.

  6. Degradation of TCE using sequential anaerobic biofilm and aerobic immobilized bed reactor

    NASA Technical Reports Server (NTRS)

    Chapatwala, Kirit D.; Babu, G. R. V.; Baresi, Larry; Trunzo, Richard M.

    1995-01-01

    Bacteria capable of degrading trichloroethylene (TCE) were isolated from contaminated wastewaters and soil sites. The aerobic cultures were identified as Pseudomonas aeruginosa (four species) and Pseudomonas fluorescens. The optimal conditions for the growth of aerobic cultures were determined. The minimal inhibitory concentration values of TCE for Pseudomonas sps. were also determined. The aerobic cells were immobilized in calcium alginate in the form of beads. Degradation of TCE by the anaerobic and dichloroethylene (DCE) by aerobic cultures was studied using dual reactors - anaerobic biofilm and aerobic immobilized bed reactor. The minimal mineral salt (MMS) medium saturated with TCE was pumped at the rate of 1 ml per hour into the anaerobic reactor. The MMS medium saturated with DCE and supplemented with xylenes and toluene (3 ppm each) was pumped at the rate of 1 ml per hour into the fluidized air-uplift-type reactor containing the immobilized aerobic cells. The concentrations of TCE and DCE and the metabolites formed during their degradation by the anaerobic and aerobic cultures were monitored by GC. The preliminary study suggests that the anaerobic and aerobic cultures of our isolates can degrade TCE and DCE.

  7. INFLUENCE OF HYDRAULIC RETENTION TIME ON EXTENT OF PCE DECHLORINATION AND PRELIMINARY CHARACTERIZATION OF THE ENRICHMENT CULTURE. (R826694C703)

    EPA Science Inventory

    The extent of tetrachloroethene (PCE) dechlorination in two chemostats was evaluated as a function of hydraulic retention time (HRT). The inoculum of these chemostats was from an upflow anaerobic sludge blanket (UASB) reactor that rapidly converts PCE to vinyl chloride (VC) an...

  8. Optimizing binary phase and amplitude filters for PCE, SNR, and discrimination

    NASA Technical Reports Server (NTRS)

    Downie, John D.

    1992-01-01

    Binary phase-only filters (BPOFs) have generated much study because of their implementation on currently available spatial light modulator devices. On polarization-rotating devices such as the magneto-optic spatial light modulator (SLM), it is also possible to encode binary amplitude information into two SLM transmission states, in addition to the binary phase information. This is done by varying the rotation angle of the polarization analyzer following the SLM in the optical train. Through this parameter, a continuum of filters may be designed that span the space of binary phase and amplitude filters (BPAFs) between BPOFs and binary amplitude filters. In this study, we investigate the design of optimal BPAFs for the key correlation characteristics of peak sharpness (through the peak-to-correlation energy (PCE) metric), signal-to-noise ratio (SNR), and discrimination between in-class and out-of-class images. We present simulation results illustrating improvements obtained over conventional BPOFs, and trade-offs between the different performance criteria in terms of the filter design parameter.

  9. Application of electrolysis to stimulate microbial reductive PCE dechlorination and oxidative VC biodegradation.

    PubMed

    Lohner, Svenja T; Tiehm, Andreas

    2009-09-15

    A novel approach was applied to stimulate biodegradation of chloroethenes bya coupled bioelectro-process. In a flow-through column system, microbial dechlorination of tetrachloroethene to cis-dichloroethene, vinyl chloride, and ethene was stimulated by hydrogen produced by water electrolysis. Dechlorinating bacteria (Dehalococcoides spp. and Desulfitobacterium spp.) and also methanogens and homoacetogens were detected in the anaerobic column. Simultaneously, oxidative biodegradation of lower chlorinated metabolites (vinyl chloride) was stimulated by electrolytic oxygen formation in the corresponding aerobic column. The process was stable for more than 100 days and an average removal of approximately 23 micromol/d PCE and 72 micromo/d vinyl chloride was obtained with a current density of 0.05 mA/cm2. Abiotic electrochemical degradation of the contaminants was not observed. Microbial dechlorination correlated with the current densities in the applied range of 0.01-0.05 mA/cm2. The results are promising for environmental applications, since with electrolysis hydrogen and oxygen can be supplied continuously to chloroethene degrading microorganisms, and the supply rates can be easily controlled by adjusting the electric current. PMID:19806748

  10. Degradation of TCE with iron: The role of competing chromate and nitrate reduction

    SciTech Connect

    Schlicker, O.; Ebert, M.; Fruth, M.; Weidner, M.; Wuest, W.; Dahmke, A.

    2000-06-01

    This study evaluates the potential of using granular iron metal for the abiotic removal of the organic ground water pollutant trichloroethene (TCE) in the presence of the common inorganic co-contaminants chromate and nitrate, respectively. Their long-term column experiments indicate a competitive process between TCE dechlorination and reductive transformation of chromate and nitrate, which is reflected in a significantly delayed onset of TCE dechlorination. Delay times and therefore the ranges of the nonreactive flowpaths increased with increasing experimental duration, resulting in a migration of the contaminants through the iron metal treatment zone. The present investigation also indicates that the calculated migration rates of TCE and the added cocontaminants chromate and nitrate are linearly related to the initial content of the cocontaminants. With an average pore water velocity of 0.6 m/d and a surface area concentration of 0.55 m{sup 2}/mL in the column, the calculated migration rates varied between 0.10 cm/d and 5.86 cm/d. The particular similarity between the values of TCE migration and the migration of the strong oxidants chromate and nitrate and the long-term steady state of the TCE dechlorination in the absence of the chromate and nitrate indicates that these competitive transformations are the driving force for the gradual passivation of the granular iron due to the buildup of an electrically insulating Fe(III)-oxyhydroxide. Based on these passivation processes, general formulae were developed that allow a simplified approximation of breakthrough times for the contaminants TCE, chromate, and nitrate.

  11. Chemostat Studies of TCE-Dehalogenating Anaerobic Consortia under Excess and Limited Electron Donor Addition

    NASA Astrophysics Data System (ADS)

    Semprini, L.; Azizian, M.; Green, J.; Mayer-Blackwell, K.; Spormann, A. M.

    2015-12-01

    Two cultures - the Victoria Strain (VS) and the Evanite Strain (EV), enriched with the organohalide respiring bacteria Dehalococcoides mccartyi - were grown in chemostats for more than 4 years at a mean cell residence time of 50 days. The slow doubling rate represents growth likely experienced in the subsurface. The chemostats were fed formate as an electron donor and trichloroethene (TCE) as the terminal electron acceptor. Under excess formate conditions, stable operation was observed with respect to TCE transformation, steady-state hydrogen (H2) concentrations (40 nM), and the structure of the dehalogenating community. Both cultures completely transformed TCE to ethene, with minor amounts of vinyl chloride (VC) observed, along with acetate formation. When formate was limited, TCE was transformed incompletely to ethene (40-60%) and VC (60- 40%), and H2 concentrations ranged from 1 to 3 nM. The acetate concentration dropped below detection. Batch kinetic studies of TCE transformation with chemostat harvested cells found transformation rates of c-DCE and VC were greatly reduced when the cells were grown with limited formate. Upon increasing formate addition to the chemostats, from limited to excess, essentially complete transformation of TCE to ethene was achieved. The increase in formate was associated with an increase in H2 concentration and the production of acetate. Results of batch kinetic tests showed increases in transformation rates for TCE and c-DCE by factors of 3.5 and 2.5, respectively, while VC rates increased by factors of 33 to 500, over a six month period. Molecular analysis of chemostat samples is being performed to quantify the changes in copy numbers of reductase genes and to determine whether shifts in the strains of Dehalococcoides mccartyi where responsible for the observed rate increases. The results demonstrate the importance of electron donor supply for successful in-situ remediation.

  12. Results of the Lasagna{trademark} Phase IIa field demonstration for the remediation of TCE in clay soils

    SciTech Connect

    Athmer, C.J.; Ho, S.V.; Hughes, B.M.; Clausen, J.L.; Johnstone, F.; Hines, R.L.

    1998-12-31

    The Lasagna{trademark} technology is an integrated in-situ treatment in which established geotechnical methods are used to install degradation zones directly in the contaminated soil and electrokinetics is utilized to move the contaminants through those zones until the treatment is completed. The Phase IIa demonstration was the second field demonstration at a trichloroethylene (TCE) contaminated site in Paducah, Ky. The first demonstration, Phase I, proved that TCE could be mobilized and captured using Lasagna{trademark}. This second demonstration measured 30 feet by 21 feet by 45 feet deep and showed for the first time TCE, including pure phase residual TCE, could be mobilized in tight soils using electrokinetics and degraded in-situ using iron filings. Over 95% removal of TCE was observed in areas of the demonstration site including pure phase residual TCE regions.

  13. A novel PCE-based algorithm for P2MP inter-domain traffic engineering in optical networks

    NASA Astrophysics Data System (ADS)

    Wu, Koubo; Zhang, Jie; Zhao, Yongli; Yu, Ziyan; Gu, Wanyi; Wang, Dajiang; Cao, Xuping

    2011-12-01

    Point-to-Multipoint (P2MP) services in optical networks are more and more important for high-capacity applications. Steiner tree algorithms have been investigated to compute minimum-cost multicast tree. However, it is difficult to compute an optimal P2MP tree in multi-domain networks because of isolation of each domain. There are several algorithms based on Path Computation Element (PCE) for computing multi-domain Point-to-point path, but computing P2MP Traffic Engineering Label Switched Path (TE-LSP) in a multi-domain networks is still a challenge. In this paper, three PCE-based schemes for P2MP inter-domain LSP computation are compared in full splitting capability networks, and a novel Multi-Domain Minimum-cost Path Heuristic (MDMPH) algorithm is proposed. Simulation results proved that the MDMPH algorithm computes P2MP tree with less cost than the other three schemes.

  14. The Effect of FeS Mineral Transformation on TCE Degradation

    NASA Astrophysics Data System (ADS)

    He, Y. T.; Wilson, J. T.; Wilkin, R. T.

    2009-12-01

    Iron- and sulfate-reducing conditions are often encountered in permeable reactive barrier (PRB) systems that are constructed to remove TCE from groundwater, which usually leads to the accumulation of FeS mineral phases in the matrix of the PRB. Poorly crystalline mackinawite (FeS) has been shown to play an important role in the removal of TCE in these engineered systems. In a column experiment simulating conditions in a PRB at Altus AFB in Oklahoma, USA, abiotic reaction of TCE with FeS could account for up to 50% of TCE removal in the PRB. However, the rate constant obtained in the column experiment with biogenic FeS was an order of magnitude higher than rates reported in the literature for TCE reaction with chemically synthesized FeS. The experiments reported in the literature used freeze drying as part of its preparation for synthesized FeS. To resolve the discrepancy between our results from biogenic FeS and the reports in the literature, we conducted batch experiments with FeS that was chemically synthesized under conditions that corresponded to the geochemical conditions in the column experiment (final free sulfide concentrations ~5 mg/L). All operations were carried out in an oxygen free glove box. One set of experiments were conducted with chemically synthesized FeS kept in suspension throughout the experiment, and a second set of experiments were conducted using FeS that had been freeze dried, then resuspended in water. The pH and free sulfide concentrations were adjusted to equal the conditions in the first set of experiments. The results show that 13C labeled TCE is readily degraded by FeS to acetylene and CO2. TCE degradation rate by FeS kept in suspension is 20-40 times faster than the freeze dried FeS. The effect of pH on TCE degradation is also investigated in this study. Mineralogical characterization by XRD and XAS show FeS in suspension remains as mackinawite (FeS) through out the experiment duration (56d), while freeze dried FeS changes over time

  15. Characterization of an Enriched Anaerobic Culture Having Ability to Dechlorinate TCE

    NASA Astrophysics Data System (ADS)

    Ise, K.; Suto, K.; Inoue, C.

    2007-03-01

    An anaerobic mixed microbial culture was enriched from soil and groundwater taken from a site contaminated with trichloroethene (TCE). This enrichment culture could dechlorinate TCE sequentially to cis-dichloroethene (cis-DCE), vinyl chloride (VC), and ethene rapidly within 2 weeks. This enrichment culture could utilize various organic compounds, such as methanol, ethanol, and sodium acetate and so on, as electron donor. This culture had maintained high ability of TCE dechlorination for about 3 years since the start of enrichment cultivation. The optimum pH value for the dechlorination activity of this culture, which reacts from TCE to ethene, was 6.7. However above the pH value 7.1, it lost the dechlorination ability of cis-DCE and VC. So cis-DCE was remained at that pH conditions. From the DNA sequencing analysis of 16SrRNA gene, this enrichment culture includes Dehalococcoides sp. which has the ability to dechlorinate TCE to VC completely with hydrogen. It suggested that this Dehalococcoides sp. takes part in the dechlorination of chloroethenes.

  16. Phytoremediation of chlorinated ethenes in seepline sediments: tree selection.

    PubMed

    Stanhope, Andrine; Berry, Christopher J; Brigmon, Robin L

    2008-01-01

    Phytoremediation of chlorinated ethene (CE)-contaminated water was investigated at the Savannah River Site in Aiken, SC, USA. Perchloroethylene (PCE) and trichloroethylene (TCE) are present where CE-contaminated groundwater currently outcrops in seepline soils. Results of constructed and planted test cells, filled with soil from a noncontaminated seepline area and supplied with CE-contaminated groundwater (48 ppb) in the field for one season are presented. These test cells were planted with loblolly pines, hybrid poplars, coyote willow, and sweet gum. Cis-dichloroethylene (cDCE), a byproduct from rhizosphere microbial activity, was detected in the soils as well as some tree tissues. All trees tested were found to uptake both PCE and TCE (5-50 pbb/gm dry wt). PMID:19260231

  17. Retardation of volatile organic compounds in ground water in low organic carbon sediments

    SciTech Connect

    Hoffman, F.

    1995-04-01

    It is postulated that adsorption onto aquifer matrix surfaces is only one of the processes that retard contaminants in ground water in unconsolidated sediments; others include hydrodynamic dispersion, abiotic/biotic degradation, matrix diffusion, partitioning to organic carbon, diffusion into and retention in dead-end pores, etc. This work aims at these processes in defining the K{sub d} of VOCs in sediments with low organic carbon content. Experiments performed include an initial column experiment for VOC (TCE and perchloroethylene(PCE)) retardation tests on geological materials, PCE and TCE data from LLNL sediments, and a preliminary multilayer sampler experiment. The VOC K{sub d}s in low organic carbon permeable aquifer materials are dependent on the VOC composition and independent of aquifer grain size, indicating that sorption was not operative and that the primary retarding factors are diffusion controlled. The program of future experiments is described.

  18. Health hazard evaluation determination report HE-80-71-703, Bear Creek Uranium Company, Douglas, Wyoming

    SciTech Connect

    Gunter, B.J.

    1980-06-01

    An environmental survey was conducted in February 1980 to evaluate exposure to CRC, a cleaning solvent containing perchloroethylene (127184), (PCE) and 1,1,1-trichloroethane (71556) (TCE) at Bear Creek Uranium Company (SIC-1094) in Wyoming. The survey was requested by the company safety engineer. Breathing zone and general room air samples were collected and analyzed. One mine electrician was exposed to 6,500 milligrams per cubic meter (mg/cu m) (PCE recommended OSHA limit is 690mg/cu m). Of the 7 samples of TCE, none exceeded the OSHA standard of 1900mg/cu m. Overexposure did occur when workers used the solvent in confined areas. The authors concluded that a health hazard existed when the solvent was used on confined spaces, and they recommend improved work practices.

  19. Development and evaluation of a harmonized physiologically based pharmacokinetic (PBPK) model for perchloroethylene toxicokinetics in mice, rats, and humans

    SciTech Connect

    Chiu, Weihsueh A.; Ginsberg, Gary L.

    2011-06-15

    This article reports on the development of a 'harmonized' PBPK model for the toxicokinetics of perchloroethylene (tetrachloroethylene or perc) in mice, rats, and humans that includes both oxidation and glutathione (GSH) conjugation of perc, the internal kinetics of the oxidative metabolite trichloroacetic acid (TCA), and the urinary excretion kinetics of the GSH conjugation metabolites N-Acetylated trichlorovinyl cysteine and dichloroacetic acid. The model utilizes a wider range of in vitro and in vivo data than any previous analysis alone, with in vitro data used for initial, or 'baseline,' parameter estimates, and in vivo datasets separated into those used for 'calibration' and those used for 'evaluation.' Parameter calibration utilizes a limited Bayesian analysis involving flat priors and making inferences only using posterior modes obtained via Markov chain Monte Carlo (MCMC). As expected, the major route of elimination of absorbed perc is predicted to be exhalation as parent compound, with metabolism accounting for less than 20% of intake except in the case of mice exposed orally, in which metabolism is predicted to be slightly over 50% at lower exposures. In all three species, the concentration of perc in blood, the extent of perc oxidation, and the amount of TCA production is well-estimated, with residual uncertainties of {approx} 2-fold. However, the resulting range of estimates for the amount of GSH conjugation is quite wide in humans ({approx} 3000-fold) and mice ({approx} 60-fold). While even high-end estimates of GSH conjugation in mice are lower than estimates of oxidation, in humans the estimated rates range from much lower to much higher than rates for perc oxidation. It is unclear to what extent this range reflects uncertainty, variability, or a combination. Importantly, by separating total perc metabolism into separate oxidative and conjugative pathways, an approach also recommended in a recent National Research Council review, this analysis

  20. Effects of different electron donor feeding patterns on TCE reductive dechlorination performance.

    PubMed

    Panagiotakis, I; Antoniou, K; Mamais, D; Pantazidou, M

    2015-03-01

    This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enhanced in situ bioremediation in TCE-contaminated aquifers. A series of lab-scale batch experiments were conducted using butyrate or hydrogen gas (H2) as e(-) donor and a TCE-dechlorinating microbial consortium dominated by Dehalococcoides spp. The results of these experiments demonstrate that butyrate is similarly efficient for TCE dechlorination whether it is injected once or in doses. Moreover, the present work indicates that the addition of butyrate in great excess cannot be avoided, since it most likely provide, even indirectly, significant part of the H2 required. Furthermore, methanogenesis appears to be the major ultimate e(-) accepting process in all experiments, regardless the e(-) donor used and the feeding pattern. Finally, the timing of injection of H2 seems to significantly affect dechlorination performance, since the injection during the early stages improves VC-to-ETH dechlorination and reduce methanogenic activity. PMID:25613854

  1. In situ, subsurface monitoring of vapor-phase TCE using fiber optics

    SciTech Connect

    Rossabi, J.; Colston, B. Jr.; Brown, S.; Milanovich, F.; Lee, L.T. Jr.

    1993-03-05

    A vapor-phase, reagent-based, fiber optic trichloroethylene (TCE) sensor developed by Lawrence Livermore National Laboratory (LLNL) was demonstrated at the Savannah River Site (SRS) in two configurations. The first incorporated the sensor into a down-well instrument bounded by two inflatable packers capable of sealing an area for discrete depth analysis. The second involved an integration of the sensor into the probe tip of the Army Corps of Engineers Waterways Experiment Station (WES) cone penetrometry system. Discrete depth measurements of vapor-phase concentrations of TCE in the vadose zone were successfully made using both configurations. These measurements demonstrate the first successful in situ sensing (as opposed to sampling) of TCE at a field site.

  2. Spatial and temporal dynamics of organohalide-respiring bacteria in a heterogeneous PCE-DNAPL source zone

    NASA Astrophysics Data System (ADS)

    Cápiro, Natalie L.; Löffler, Frank E.; Pennell, Kurt D.

    2015-11-01

    Effective treatment of sites contaminated with dense non-aqueous phase liquids (DNAPLs) requires detailed understanding of the microbial community responses to changes in source zone strength and architecture. Changes in the spatial and temporal distributions of the organohalide-respiring Dehalococcoides mccartyi (Dhc) strains and Geobacter lovleyi strain SZ (GeoSZ) were examined in a heterogeneous tetrachloroethene- (PCE-) DNAPL source zone within a two-dimensional laboratory-scale aquifer flow cell. As part of a combined remedy approach, flushing with 2.3 pore volumes (PVs) of 4% (w/w) solution of the nonionic, biodegradable surfactant Tween® 80 removed 55% of the initial contaminant mass, and resulted in a PCE-DNAPL distribution that contained 51% discrete ganglia and 49% pools (ganglia-to-pool ratio of 1.06). Subsequent bioaugmentation with the PCE-to-ethene-dechlorinating consortium BDI-SZ resulted in cis-1,2-dichloroethene (cis-DCE) formation after 1 PV (ca. 7 days), while vinyl chloride (VC) and ethene were detected 10 PVs after bioaugmentation. Maximum ethene yields (ca. 90 μM) within DNAPL pool and ganglia regions coincided with the detection of the vcrA reductive dehalogenase (RDase) gene that exceeded the Dhc 16S rRNA genes by 2.0 ± 1.3 and 4.0 ± 1.7 fold in the pool and ganglia regions, respectively. Dhc and GeoSZ cell abundance increased by up to 4 orders-of-magnitude after 28 PVs of steady-state operation, with 1 to 2 orders-of-magnitude increases observed in close proximity to residual PCE-DNAPL. These observations suggest the involvement of these dechlorinators the in observed PCE dissolution enhancements of up to 2.3 and 6.0-fold within pool and ganglia regions, respectively. Analysis of the solid and aqueous samples at the conclusion of the experiment revealed that the highest VC (≥ 155 μM) and ethene (≥ 65 μM) concentrations were measured in zones where Dhc and GeoSZ were predominately attached to the solids. These findings demonstrate

  3. Visualization of TCE recovery mechanisms using surfactant polymer solutions in a two-dimensional heterogeneous sand model

    NASA Astrophysics Data System (ADS)

    Robert, Thomas; Martel, Richard; Conrad, Stephen H.; Lefebvre, René; Gabriel, Uta

    2006-06-01

    This research focused on the optimization of TCE dissolution in a physical two-dimensional model providing a realistic representation of a heterogeneous granular aquifer. TCE was infiltrated in the sand pack where it resided both in pools and in zones of residual saturation. Surfactant was initially injected at low concentration to minimize TCE remobilization at first contact but was incrementally increased later during the experiment. Xanthan gum was added to the injected surfactant solution to optimize the sweep efficiency through the heterogeneous medium. Photographs and digital image analysis illustrated the interactions between TCE and the injected fluids. During the polymer flood, the effects of heterogeneities inside the sand pack were greatly reduced by the increased fluid viscosity and the shear-thinning effects of the polymer. The polymer also improved the contact between the TCE ganglia and the surfactant-polymer solution, thereby promoting dissolution. Surfactants interacted with the polymer reducing the overall viscosity of the solution. At first contact with a 0.5% mass surfactant solution, the TCE pools drained and some remobilization occurred. However, no TCE bank was formed and TCE did not penetrate into any previously uncontaminated areas. As a result, TCE surface area was increased. Subsequent surfactant floods at higher surfactant concentrations did not trigger more remobilization. TCE was mainly dissolved by the solution with the highest surfactant concentration. Plugging from bacterial growth or microgel formation associated to the polymer at the inflow screen prevented the full completion of the experiment. However, more than 90% of TCE was recovered with the circulation of less than 6 pore volumes of surfactant-polymer solution.

  4. Visualization of TCE recovery mechanisms using surfactant-polymer solutions in a two-dimensional heterogeneous sand model.

    PubMed

    Robert, Thomas; Martel, Richard; Conrad, Stephen H; Lefebvre, René; Gabriel, Uta

    2006-06-30

    This research focused on the optimization of TCE dissolution in a physical two-dimensional model providing a realistic representation of a heterogeneous granular aquifer. TCE was infiltrated in the sand pack where it resided both in pools and in zones of residual saturation. Surfactant was initially injected at low concentration to minimize TCE remobilization at first contact but was incrementally increased later during the experiment. Xanthan gum was added to the injected surfactant solution to optimize the sweep efficiency through the heterogeneous medium. Photographs and digital image analysis illustrated the interactions between TCE and the injected fluids. During the polymer flood, the effects of heterogeneities inside the sand pack were greatly reduced by the increased fluid viscosity and the shear-thinning effects of the polymer. The polymer also improved the contact between the TCE ganglia and the surfactant-polymer solution, thereby promoting dissolution. Surfactants interacted with the polymer reducing the overall viscosity of the solution. At first contact with a 0.5%(mass) surfactant solution, the TCE pools drained and some remobilization occurred. However, no TCE bank was formed and TCE did not penetrate into any previously uncontaminated areas. As a result, TCE surface area was increased. Subsequent surfactant floods at higher surfactant concentrations did not trigger more remobilization. TCE was mainly dissolved by the solution with the highest surfactant concentration. Plugging from bacterial growth or microgel formation associated to the polymer at the inflow screen prevented the full completion of the experiment. However, more than 90% of TCE was recovered with the circulation of less than 6 pore volumes of surfactant-polymer solution. PMID:16624443

  5. Gene regulation in Drosophila spermatogenesis: analysis of protein binding at the translational control element TCE.

    PubMed

    Kempe, E; Muhs, B; Schäfer, M

    1993-01-01

    We have previously identified a 12 nucleotide long sequence element, the TCE, that was demonstrated to be necessary for translational control of expression in the male germ line of Drosophila melanogaster (Schäfer et al., 1990). It is conserved among all seven members of the Mst(3)CGP gene family, that encode structural proteins of the sperm tail. The TCE is invariably located in the 5' untranslated region (UTR) at position +28 relative to the transcription start site. In this paper we analyse the mode of action of this element. We show that protein binding occurs at the TCE after incubation with testis protein extracts from Drosophila melanogaster. While several proteins are associated with the translational control element in the RNA, only one of these proteins directly crosslinks to the sequence element. The binding activity is exclusively observed with testis protein extracts but can be demonstrated with testis extracts from other Drosophila species as well, indicating that regulatory proteins involved in translational regulation in the male germ line are conserved. Although binding to the TCE can occur independent of its position relative to the transcription start site of the in vitro transcripts, its function in vivo is not exerted when shifted further downstream within the 5' UTR of a fusion gene. In addition to being a translational control element the TCE also functions as a transcriptional regulator. Consequently, a DNA-protein complex is also formed at the TCE. In contrast to the RNA-protein complexes we find DNA-protein complexes with protein extracts of several tissues of Drosophila melanogaster. PMID:8111973

  6. Hydrodechlorination of TCE in a circulated electrolytic column at high flow rate.

    PubMed

    Fallahpour, Noushin; Yuan, Songhu; Rajic, Ljiljana; Alshawabkeh, Akram N

    2016-02-01

    Palladium-catalytic hydrodechlorination of trichloroethylene (TCE) by cathodic H2 produced from water electrolysis has been tested. For a field in-well application, the flow rate is generally high. In this study, the performance of Pd-catalytic hydrodechlorination of TCE using cathodic H2 is evaluated under high flow rate (1 L min(-1)) in a circulated column system, as expected to occur in practice. An iron anode supports reduction conditions and it is used to enhance TCE hydrodechlorination. However, the precipitation occurs and high flow rate was evaluated to minimize its adverse effects on the process (electrode coverage, clogging, etc.). Under the conditions of 1 L min(-1) flow, 500 mA current, and 5 mg L(-1) initial TCE concentration, removal efficacy using iron anodes (96%) is significantly higher than by mixed metal oxide (MMO) anodes (66%). Two types of cathodes (MMO and copper foam) in the presence of Pd/Al2O3 catalyst under various currents (250, 125, and 62 mA) were used to evaluate the effect of cathode materials on TCE removal efficacy. The similar removal efficiencies were achieved for both cathodes, but more precipitation generated with copper foam cathode (based on the experiments done by authors). In addition to the well-known parameters such as current density, electrode materials, and initial TCE concentration, the high velocities of groundwater flow can have important implications, practically in relation to the flush out of precipitates. For potential field application, a cost-effective and sustainable in situ electrochemical process using a solar panel as power supply is being evaluated. PMID:26344148

  7. System for In-Situ Detection of Plant Exposure to Trichloroethylene (TCE)

    NASA Technical Reports Server (NTRS)

    Lewis, Mark D. (Inventor); Anderson, Daniel J. (Inventor); Newman, Lee A. (Inventor); Keith, Amy G. (Inventor)

    2013-01-01

    A system detects a plant's exposure to trichloroethylene (TCE) through plant leaf imaging. White light impinging upon a plant's leaf interacts therewith to produce interacted light. A detector is positioned to detect at least one spectral band of the interacted light. A processor coupled to the detector performs comparisons between photonic energy of the interacted light at the one or more spectral bands thereof and reference data defining spectral responses indicative of leaf exposure to TCE. An output device coupled to the processor provides indications of the comparisons.

  8. CIS-DCE AND VC MICROBIAL COMMUNITY CHANGES ASSOCIATED WITH A SHIFT FROM REDUCTIVE DECHLORINATION OF PCE TO REDUCTIVE DECHLORINATION OF

    EPA Science Inventory

    Subcultures that reductively dechlorinate cis-dichloroethene (cis-DCE) or vinyl chloride (VC) were derived from three independent enrichments that completely dechlorinated tetrachloroethene (PCE) to ethene in order to study the reductive dechlorination of the lesser chlorinated e...

  9. Use Of Statistical Tools To Evaluate The Reductive Dechlorination Of High Levels Of TCE In Microcosm Studies

    EPA Science Inventory

    A large, multi-laboratory microcosm study was performed to select amendments for supporting reductive dechlorination of high levels of trichloroethylene (TCE) found at an industrial site in the United Kingdom (UK) containing dense non-aqueous phase liquid (DNAPL) TCE. The study ...

  10. PD-CATALYZED TCE DECHLORINATION IN GROUNDWATER: SOLUTE EFFECTS, BIOLOGICAL CONTROL, AND OXIDATIVE CATALYST REGENERATION. (R825421)

    EPA Science Inventory

    The performance of a Pd-on-src="/ncer/pubs/images/gamma.gif">-Al2O3 catalyst for
    dechlorination of trichloroethylene (TCE) was evaluated in synthetic and real
    groundwater. Low initial TCE conversions were used to provide maximum ...

  11. High-Performance Polymer Solar Cells with PCE of 10.42% via Al-Doped ZnO Cathode Interlayer.

    PubMed

    Liu, Xiaohui; Li, Xiaodong; Li, Yaru; Song, Changjian; Zhu, Liping; Zhang, Wenjun; Wang, Hai-Qiao; Fang, Junfeng

    2016-09-01

    High-performance polymer solar cells incorporating a low-temperature-processed aluminum-doped zinc oxide (AZO) cathode interlayer are constructed with power conversion efficiency (PCE) of 10.42% based on PTB7-Th:PC71 BM blends (insensitive to the AZO thickness). Moreover, flexible devices on poly(ethylene terephthalate)/indium tin oxide substrates with PCE of 8.93% are also obtained, and welldistributed efficiency and good device stability are demonstrated as well. PMID:27309840

  12. Stable Isotope Fractionation of Tetrachloroethene during Reductive Dechlorination by Sulfurospirillum multivorans and Desulfitobacterium sp. Strain PCE-S and Abiotic Reactions with Cyanocobalamin

    PubMed Central

    Nijenhuis, Ivonne; Andert, Janet; Beck, Kirsten; Kästner, Matthias; Diekert, Gabriele; Richnow, Hans-Hermann

    2005-01-01

    Carbon stable isotope fractionation of tetrachloroethene (PCE) during reductive dechlorination by whole cells and crude extracts of Sulfurospirillum multivorans and Desulfitobacterium sp. strain PCE-S and the abiotic reaction with cyanocobalamin (vitamin B12) was studied. Fractionation was largest during the reaction with cyanocobalamin with αC = 1.0132. Stable isotope fractionation was lower but still in a similar order of magnitude for Desulfitobacterium sp. PCE-S (αC = 1.0052 to 1.0098). The isotope fractionation of PCE during dehalogenation by S. multivorans was lower by 1 order of magnitude (αC = 1.00042 to 1.0017). Additionally, an increase in isotope fractionation was observed with a decrease in cell integrity for both strains. For Desulfitobacterium sp. strain PCE-S, the carbon stable isotope fractionation factors were 1.0052 and 1.0089 for growing cells and crude extracts, respectively. For S. multivorans, αC values were 1.00042, 1.00097, and 1.0017 for growing cells, crude extracts, and the purified PCE reductive dehalogenase, respectively. For the field application of stable isotope fractionation, care is needed as fractionation may vary by more than an order of magnitude depending on the bacteria present, responsible for degradation. PMID:16000743

  13. Validation and application of pharmacokinetic models for interspecies extrapolations in toxicity risk assessments of volatile organics. Annual report No. 2, 1 July 1988-30 June 1989

    SciTech Connect

    Dallas, C.E.; Bruckner, J.V.; Gallo, J.; Ramanathan, R.; Muralidhara, S.

    1989-07-21

    In pursuit of the goal of establishing a scientific basis for the interspecies extrapolation of pharmacokinetic data in health-risk assessments, a series of studies were conducted involving pharmacokinetic determinations in rats to several aliphatic halocarbons (with parallel studies initiated in the dog). Direct measurements of the uptake and elimination of halocarbon in rats were completed during the following inhalation exposures and following oral administration of dichloroethylene (DCE) and perchloroethylene (PCE). An assay for the measurement of halocarbons in the tissues of exposed animals has been successfully developed, and tissue-concentration profiles in the liver, kidney, lung, fat, brain, muscle, and heart were completed for oral and intraarterial administrations of PCE. The utility of the physiologically-based pharmacokinetic model for the accurate computer simulations of the pharmacokinetics of three halocarbons with wide variation in physicochemical properties (TRI, TCE, and PCE) has been demonstrated.

  14. Preliminary technology report for Southern Sector bioremediation

    SciTech Connect

    Brigmon, R.L.; White, R.; Hazen, T.C.; Jones, D.; Berry, C.

    1997-06-01

    This project was designed to demonstrate the potential of intrinsic bioremediation and phytoremediation in the Southern Sector of the A/M-Area at the Savannah River Site. A subsurface plume of trichloroethylene (TCE) and perchloroethylene (PCE) is present in the Lost Lake aquifer upgradient of the study site and is predicted to impact the area at some point in the future. The surface area along the Lost lake aquifer seep line where the plume is estimated to emerge was identified. Ten sites along the seep line were selected for biological, chemical, and contaminant treatability analyses. A survey was undertaken in this area to to quantify the microbial and plant population known to be capable of remediating TCE and PCE. The current groundwater quality upgradient and downgradient of the zone of influence was determined. No TCE or PCE was found in the soils or surface water from the area tested at this time. A TCE biodegradation treatability test was done on soil from the 10 selected locations. From an initial exposure of 25 ppm of TCE, eight of the samples biodegraded up to 99.9 percent of all the compound within 6 weeks. This biodegradation of TCE appears to be combination of aerobic and anaerobic microbial activity as intermediates that were detected in the treatability test include vinyl chloride (VC) and the dichloroethenes (DCE) 1,2-cis-dichloroethylene and 1,1-dichloroethylene. The TCE biological treatability studies were combines with microbiological and chemical analyses. The soils were found through immunological analysis with direct fluorescent antibodies (DFA) and microbiological analysis with direct fluorescent antibodies (DFA) and microbiological analysis to have a microbial population of methanotrophic bacteria that utilize the enzyme methane monooxygenase (MMO) and cometabolize TCE.

  15. RATE OF TCE DEGRADATION IN A PLANT MULCH PASSIVE REACTIVE BARRIER (BIOWALL)

    EPA Science Inventory

    A passive reactive barrier was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contaminated groun...

  16. EFFECTIVE REMOVAL OF TCE IN A LABORATORY MODEL OF A PRB CONSTRUCTED WITH PLANT MULCH

    EPA Science Inventory

    Ground water contaminated with TCE is commonly treated with a permeable reactive barrier (PRB) constructed with zero-valence iron. The cost of iron as the reactive matrix has driven a search for less costly alternatives, and composted plant mulch has been used as an alternative ...

  17. FIELD SCALE EVALUATION OF TREATMENT OF TCE IN A BIOWALL AT THE OU-1 SITE

    EPA Science Inventory

    A passive reactive barrier (Biowall) was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contamin...

  18. LESSONS LEARNED FROM IN-SITU RESISTIVE HEATING OF TCE AT FORT LEWIS, WASHINGTON

    EPA Science Inventory

    The EGDY is the source of a potentially expanding, three mile long TCE plume in a sole source drinking water aquifer. Thermal remediation is being employed to reduce source mass loading to the dissolved phase aquifer plume and reduce the time to reach site cleanup goals. This i...

  19. 76 FR 30243 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-24

    ..., or private delivery service; or electronically through Grants.gov by the deadline date. ADDRESSES.... Regulations were published in the Federal Register at 44 FR 72113 on December 13, 1979. Section 163 gives the... Internal Revenue Service Tax Counseling for the Elderly (TCE) Program Availability of Application...

  20. Abiotic and Biotic Transformation of TCE under Sulfate Reducing Conditions: the Role of Spatial Heterogeneity

    EPA Science Inventory

    At a number of sites in the USA, passive reactive barriers built with shredded plant mulch have been constructed to treat ground water contaminated with TCE. These barriers are called biowalls because anaerobic biodegradation of the plant mulch is expected to provide substrates...

  1. REMEDIATION OF TCE-CONTAMINATED GROUNDWATER BY A PERMEABLE REACTIVE BARRIER FILLED WITH PLANT MULCH (BIOWALL)

    EPA Science Inventory

    A pilot-scale permeable reactive barrier filled with plant mulch was installed at Altus Air Force Base (in Oklahoma, USA) to treat trichloroethylene (TCE) contamination in ground water emanating from a landfill. The barrier was constructed in June 2002. It was 139 meters long, 7 ...

  2. Betula pendula: A Promising Candidate for Phytoremediation of TCE in Northern Climates.

    PubMed

    Lewis, Jeffrey; Qvarfort, Ulf; Sjöström, Jan

    2015-01-01

    Betula pendula (Silver birch) trees growing on two contaminated sites were evaluated to assess their capacity to phytoscreen and phytoremediate chlorinated aliphatic compounds and heavy metals. Both locations are industrially-contaminated properties in central Sweden. The first was the site of a trichloroethylene (TCE) spill in the 1980s while the second was polluted with heavy metals by burning industrial wastes. In both cases, sap and sapwood from Silver birch trees were collected and analyzed for either chlorinated aliphatic compounds or heavy metals. These results were compared to analyses of the surface soil, vadose zone pore air and groundwater. Silver birch demonstrated the potential to phytoscreen and possibly phytoremediate TCE and related compounds, but it did not demonstrate the ability to effectively phytoextract heavy metals when compared with hyperaccumulator plants. The capacity of Silver birch to phytoremediate TCE appears comparable to tree species that have been employed in field-scale TCE phytoremediation efforts, such as Populus spp. and Eucalyptus sideroxylon rosea. PMID:25174420

  3. Diversity of Pristine Methanotrophic Communities in a Basalt Aquifer: Implications for Natural Attenuation of TCE

    NASA Astrophysics Data System (ADS)

    Reed, D. W.; Newby, D. T.; Delwiche, M. E.; Igoe, A.; McKinley, J. P.; Roberto, F. F.; Colwell, F. S.

    2001-12-01

    Natural attenuation of a large trichloroethylene (TCE) plume within the oxic Snake River Plain Aquifer (SRPA) appears to be occurring by aerobic co-metabolism. Methanotrophs are some of the key TCE degraders known to inhabit the aquifer. To better understand the role methanotrophs may have in TCE degradation and the relationship of methanotrophs to dissolved methane concentrations, groundwater collected from wells in the SRPA was analyzed for geochemical properties and methanotroph diversity. Microorganisms removed from groundwater by filtration were used as inocula for enrichments or were frozen and subsequently extracted for DNA. Primers that target Type I and Type II methanotroph 16S rDNA or genes that code for soluble (mmoX) and particulate (pmoA) methane monooxygenase subunits were used to characterize the indigenous methanotrophs via PCR, cloning, and sequencing. Groundwater had dissolved methane concentrations that ranged from 1 to >1000 nM. Analysis of sequencing results suggest that the group Methylocystaceae is a predominant Type II methanotroph in each sample. Methanotrophs can be detected and enriched from groundwater containing even low methane concentrations. Analysis of gene sequences provides assessments of methanotroph abundance and diversity with respect to the aquifer methane concentrations, imparting greater insight into the genetic potential of the microbial community capable of degrading TCE. This research will continue to focus on the evaluation of natural attenuation by methanotrophs.

  4. Formulation design for target delivery of iron nanoparticles to TCE zones

    NASA Astrophysics Data System (ADS)

    Wang, Ziheng; Acosta, Edgar

    2013-12-01

    Nanoparticles of zero-valent iron (NZVI) are effective reducing agents for some dense non-aqueous phase liquid (DNAPL) contaminants such as trichloroethylene (TCE). However, target delivery of iron nanoparticles to DNAPL zones in the aquifer remains an elusive feature for NZVI technologies. This work discusses three strategies to deliver iron nanoparticles to DNAPL zones. To this end, iron oxide nanoparticles coated with oleate (OL) ions were used as stable analogs for NZVI. The OL-coated iron oxide nanoparticles are rendered lipophilic via (a) the addition of CaCl2, (b) acidification, or (c) the addition of a cationic surfactant, benzethonium chloride (BC). Mixtures of OL and BC show promise as a target delivery strategy due to the high stability of the nanoparticles in water, and their preferential partition into TCE in batch experiments. Column tests show that while the OL-BC coated iron oxide nanoparticles remain largely mobile in TCE-free columns, a large fraction of these particles are retained in TCE-contaminated columns, confirming the effectiveness of this target delivery strategy.

  5. Modeling of TCE diffusion to the atmosphere and distribution in plant stems.

    PubMed

    Ma, Xingmao; Burken, Joel

    2004-09-01

    Fate of chlorinated solvents in phytoremediation has been delineated by many discoveries made in recent years. Plant uptake, metabolism, rhizosphere degradation, accumulation, and volatilization were shown to occur to differing degrees for many organic contaminants including chlorinated solvents. Among these mechanistic findings, recent research confirmed that volatile organic compounds (VOCs) volatilize from stems and that the resulting diffusive flux to the atmosphere is related to exposure concentration and to height up the stem. A comprehensive model was developed based upon all identified fate and transport mechanisms for VOCs, including translocation in the xylem flow and diffusion. The dispersion and diffusion in the radial direction were considered as one process (effective diffusion) as the two could not be investigated individually. The mechanism-based model mathematically indicates an exponential decrease of concentrations with height. While an analytic solution for the comprehensive model was not attained, it can serve as a starting point for other modeling efforts. The comprehensive model was simplified in this work for practical application to experimentally obtained data on trichloroethylene (TCE) fate. Model output correlated well with experimental results, and effective diffusivities for TCE in plant tissues were obtained through the model calibrations. The simplified model approximated TCE concentrations in the transpiration stream as well as TCE volatilization to the atmosphere. Xylem transport, including advection, dispersion, and diffusion through cell walls with subsequent volatilization to the atmosphere, is a major fate for VOCs in phytoremediation. PMID:15461166

  6. A SEARCH FOR RESIDUAL BEHAVIORAL EFFECTS OF TRICHLOROETHYLENE (TCE) IN RATS EXPOSED AS YOUNG ADULTS

    EPA Science Inventory

    Trichloroethylene (TCE) is a solvent of concern to the EPA due to its extensive use in industry, its prevalence in urban air, and its appearance in water supplies. Human clinical studies have associated short and long-termsolvent exposures with cognitive dysfunction including att...

  7. Decision Tree based Prediction and Rule Induction for Groundwater Trichloroethene (TCE) Pollution Vulnerability

    NASA Astrophysics Data System (ADS)

    Park, J.; Yoo, K.

    2013-12-01

    For groundwater resource conservation, it is important to accurately assess groundwater pollution sensitivity or vulnerability. In this work, we attempted to use data mining approach to assess groundwater pollution vulnerability in a TCE (trichloroethylene) contaminated Korean industrial site. The conventional DRASTIC method failed to describe TCE sensitivity data with a poor correlation with hydrogeological properties. Among the different data mining methods such as Artificial Neural Network (ANN), Multiple Logistic Regression (MLR), Case Base Reasoning (CBR), and Decision Tree (DT), the accuracy and consistency of Decision Tree (DT) was the best. According to the following tree analyses with the optimal DT model, the failure of the conventional DRASTIC method in fitting with TCE sensitivity data may be due to the use of inaccurate weight values of hydrogeological parameters for the study site. These findings provide a proof of concept that DT based data mining approach can be used in predicting and rule induction of groundwater TCE sensitivity without pre-existing information on weights of hydrogeological properties.

  8. Initial Results of ISCO for a Large TCE DNAPL Source Area

    SciTech Connect

    Thompson, S.L.; Cross, P.E.

    2008-07-01

    This paper will describe the results of an in situ chemical oxidation (ISCO) remedial action currently in progress to address subsurface contamination by trichloroethene (TCE) dense nonaqueous phase liquid (DNAPL). The U.S. Department of Energy is responsible for the cleanup of environmental media at the Portsmouth Gaseous Diffusion Plant (PORTS) in southern Ohio. The X-701B Solid Waste Management Unit is an unlined surface impoundment at PORTS which was operated from 1954 to 1988. A TCE plume in groundwater emanates from the unit and is approximately 2,200 feet in length. Metals, radioactive inorganics, and other organic chemicals are also present at lower concentrations in the groundwater. An ongoing 1.6-acre TCE DNAPL source area for the plume is believed to exist up-gradient in the vicinity of the X-701B pond. The extent of the source area is inferred from actual recovery of DNAPL in production wells and from detection of TCE concentrations between 100 and 1,000 mg/L in monitoring wells. Previous remedial activities at X-701B have included a Resource Conservation and Recovery Act (RCRA) closure and a technology demonstration that recirculated permanganate solutions between two horizontal wells. Results of sampling after these remedial activities showed that the permanganate effectively destroyed TCE in portions of the aquifer where adequate contact was achieved, but that uniform distribution by the recirculation system was problematic. As a result, the TCE concentration in the groundwater eventually rebounded after the treatment. To overcome distribution issues and to more aggressively remediate the source, a new remediation approach is being implemented for the unit. The new approach involves the injection of Modified Fenton's Reagent directly into the source area using temporary direct push injection points. This new approach provides the ability to overcome limitations imposed by heterogeneities in the subsurface by injecting relatively small quantities of

  9. Fingerprinting TCE in a bedrock aquifer using compound-specific isotope analysis.

    PubMed

    Lojkasek-Lima, Paulo; Aravena, Ramon; Parker, Beth L; Cherry, John A

    2012-01-01

    A dual isotope approach based on compound-specific isotope analysis (CSIA) of carbon (C) and chlorine (Cl) was used to identify sources of persistent trichloroethylene (TCE) that caused the shut-down in 1994 of a municipal well in an extensive fractured dolostone aquifer beneath Guelph, Ontario. Several nearby industrial properties have known subsurface TCE contamination; however, only one has created a comprehensive monitoring network in the bedrock. The impacted municipal well and many monitoring wells were sampled for volatile organic compounds (VOCs), inorganic parameters, and CSIA. A wide range in isotope values was observed at the study site. The TCE varies between -35.6‰ and -21.8‰ and from 1.6‰ to 3.2‰ for δ(13) C and δ(37) Cl, respectively. In case of cis-1,2-dichloroethene, the isotope values range between -36.3‰ and -18.9‰ and from 2.4‰ to 4.7‰ for δ(13) C and δ(37) Cl, respectively. The dual isotope approach represented by a plot of δ(13) C vs. δ(37) Cl shows the municipal well samples grouped in a domain clearly separate from all other samples from the property with the comprehensive well network. The CSIA results collected under non-pumping and short-term pumping conditions thus indicate that this particular property, which has been studied intensively for several years, is not a substantial contributor of the TCE presently in the municipal well under non-pumping conditions. This case study demonstrates that CSIA signatures would have been useful much earlier in the quest to examine sources of the TCE in the municipal well if bedrock monitoring wells had been located at several depths beneath each of the potential TCE-contributing properties. Moreover, the CSIA results show that microbial reductive dechlorination of TCE occurs in some parts of the bedrock aquifer. At this site, the use of CSIA for C and Cl in combination with analyses of VOC and redox parameters proved to be important due to the complexity introduced by

  10. Remediation of TCE contaminated soils by in situ EK-Fenton process.

    PubMed

    Yang, G C; Liu, C Y

    2001-08-17

    The treatment performance and cost analysis of in situ electrokinetic (EK)-Fenton process for oxidation of trichloroethylene (TCE) in soils were evaluated in this work. In all experiments, an electric gradient of 1V/cm, de-ionized water as the cathode reservoir fluid and a treatment time of 10 days were employed. Treatment efficiencies of TCE were evaluated in terms of the electrode material, soil type, catalyst type, and catalyst dosage and granular size if applicable. Test results show that graphite electrodes are superior to stainless steel electrodes. It was found that the soil with a higher content of organic matter would result in a lower treatment efficiency (e.g. a sandy loam is less efficient than a loamy sand). Experimental results show that the type of catalyst and its dosage would markedly affect the reaction mechanisms (i.e. "destruction" and "removal") and the treatment efficiency. Aside from FeSO4, scrap iron powder (SIP) in the form of a permeable reactive wall was also found to be an effective catalyst for Fenton reaction to oxidize TCE. In general, the smaller the granular size of SIP, the lower the overall treatment efficiency and the greater the destruction efficiency. When a greater quantity of SIP was used, a decrease of the overall treatment efficiency and an increase of percent destruction of TCE were found. Experimental results have shown that the quantity of electro-osmotic (EO) flow decreased as the quantity of SIP increased. It has been verified that the treatment performances are closely related to the corresponding EO permeability. Results of the cost analysis have indicated that the EK-Fenton process employed in this work is very cost-effective with respect to TCE destruction. PMID:11489531