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1

Catalytic removal of perchloroethylene (PCE) over supported chromium oxide catalysts  

Microsoft Academic Search

The oxidation of perchloroethylene (PCE) was investigated over chromium oxide catalysts supported on SiO2, SiO2–Al2O3, activated carbon, mordenite type zeolites, MgO, TiO2 and Al2O3. Supported chromium oxide catalysts were more active than any other metal oxide catalysts including noble metal examined in the present study. PCE removal activity of chromium oxide catalysts mainly depended on the type of supports and

Sung Dae Yim; Kwang-Hyun Chang; Dong Jun Koh; In-Sik Nam; Young Gul Kim

2000-01-01

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

Perchloroethylene (PCE) oxidation by percarbonate in Fe(2+)-catalyzed aqueous solution: PCE performance and its removal mechanism.  

PubMed

The performance of Fe(2+)-catalyzed sodium percarbonate (SPC) stimulating the oxidation of perchloroethylene (PCE) in groundwater remediation was investigated. The experimental results showed that PCE could be completely oxidized in 5 min at 20 °C with a Fe(2+)/SPC/PCE molar ratio of 8/8/1, indicating the effectiveness of Fe(2+)-catalyzed SPC oxidation for PCE degradation. Fe(2+)-catalyzed SPC oxidation was suitable for the nearly neutral pH condition, which was superior to the conventional Fenton oxidation in acidic condition. In addition, the investigations by using hydroxyl radical scavengers and free radical probe compounds elucidated that PCE was degraded mainly by hydroxyl radical (HO) oxidation in Fe(2+)/SPC system. In conclusion, Fe(2+)-catalyzed SPC oxidation is a highly promising technique for PCE-contaminated groundwater remediation, but more complex constituents in groundwater should be carefully considered for its practical application. PMID:25460751

Miao, Zhouwei; Gu, Xiaogang; Lu, Shuguang; Zang, Xuke; Wu, Xiaoliang; Xu, Minhui; Ndong, Landry Biyoghe Bi; Qiu, Zhaofu; Sui, Qian; Fu, George Yuzhu

2015-01-01

4

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...

5

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...

6

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...

7

ADVANCED OXIDATION PROCESSES FOR TREATING GROUNDWATER CONTAMINATED WITH TCE (TRICHLOROETHYLENE) AND PCE (TETRACHLOROETHYLENE): LABORATORY STUDIES (JOURNAL VERSION)  

EPA Science Inventory

Oxidation of trichloroethylene (TCE) and tetrachloroethylene (PCE) with various dosages of ozone or ozone plus hydrogen peroxide was studied in laboratory experiments. The results show that hydrogen peroxide accelerates the oxidation of TCE and PCE by ozone. At peroxide-to-ozone ...

8

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...

9

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

SciTech Connect

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.

Brigmon, R.L.

2000-12-15

10

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

PubMed Central

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

2014-01-01

11

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

SciTech Connect

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.

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

1999-07-01

12

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

SciTech Connect

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.

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. [Illinois State Geological Survey, Champaign, IL (United States); Buchanan, D.H. [Eastern Illinois Univ., Charleston, IL (United States); Stucki, J.W. [Univ. of Illinois, Urbana, IL (United States); Huffman, G.P.; Huggins, F.E. [Univ. of Kentucky, Lexington, KY (United States)

1993-12-31

13

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

PubMed Central

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

Luo, Jing; Farrell, James

2013-01-01

14

Phytoremediation of Trichloroethylene and Perchloroethylene at the Savannah River Site  

SciTech Connect

Bioremediation of chlorinated solvents, both natural and accelerated, is exemplified by phytoremediation and biodegradation by rhizosphere microorganisms. Phytoremediation is the use of vegetation for the treatment of contaminated soils, sediments, and water. The potential for phytoremediation of chlorinated solvents has been demonstrated at the Savannah River Site (SRS) Miscellaneous Chemical Basin, Southern Sector of A/M Area and TNX/D-Area. Recent characterization work at the SRS has delineated widespread plumes (1-2 miles) of low concentration (40 ppb -10-ppm range) trichloroethylene (TCE) and perchloroethylene (PCE) contaminated groundwater. Phytoremediation deployments are underway for TCE and PCE phytoremediation in select SRS areas. Phytoremediation appears to be an excellent technology to intercept and control plume migration. The ongoing Southern Sector treatability study is part of a multi-year field study of SRS seepline-soil systems maintained under saturated conditions. The primary focus is on determining how trees, seepline groundcover, soil microbial communities, and geochemical and surface-volatilization processes affect TCE and PCE in contaminated groundwater that flows through surface seepline areas. Therefore, FY00 represented an initial acclimation phase for soil and plant systems and will facilitate examination of seepline phyto- and bioactivity in subsequent growth season in FY01.

Brigmon, R.L.

2001-01-10

15

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

USGS Publications Warehouse

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.

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

2004-01-01

16

RESPONSE TO ISSUES AND DATA SUBMISSIONS ON THE CARCINOGENICITY OF TETRACHLOROETHYLENE (PERCHLOROETHYLENE)  

EPA Science Inventory

The scientific debate over the potential carcinogenicity of tetrachloroethylene (perchloroethylene, perc, PCE) spans several years. his document reviews the issues considered by the EPA's Science Advisory Board (SAB) during its review of the Draft Addendum to the Health Assessmen...

17

Industrial-hygiene report: perchloroethylene at Dubarry Cleaners, Detroit, Michigan  

Microsoft Academic Search

An on-site visit was made to Dubarry Cleaners, Detroit, Michigan, as part of an industry-wide mortality and industrial hygiene study of dry cleaning workers exposed to perchloroethylene (PCE). Air samples were taken at the facility and the time weighted average exposure to PCE was calculated to be 23 parts per million (ppm) with 5-minute peak exposures ranging from 33 to

1980-01-01

18

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...

19

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...

20

Effect of temperature on perchloroethylene dechlorination by a methanogenic consortium  

SciTech Connect

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.

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

1995-04-01

21

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...

22

Kinetics study of the perchloroethylene hydrofluorination into pentafluoroethane (Freon 125) over chromium-based catalyst  

Microsoft Academic Search

The gas-phase hydrofluorination of perchloroethylene (PCE) into pentafluoroethane (non ozone-depleting Freon 125) at T=330–390°C and P=0.4MPa in the presence of a chromium–magnesium catalyst has been studied. A hydrofluorination scheme including main product and by-products formation routes is deduced from the observed dependences of particular products selectivity. The kinetic model of the PCE hydrofluorination has been developed. The rate parameters and

S. I. Reshetnikov; A. A. Zirka; R. V. Petrov; E. A. Ivanov

23

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 ...

24

Catalytic Dechlorination of Gas-phase Perchloroethylene under Mixed Redox Conditions  

PubMed Central

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

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

2008-01-01

25

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

PubMed Central

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

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

2010-01-01

26

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

PubMed

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

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

2009-01-01

27

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...

28

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...

29

EMISSIONS OF PERCHLOROETHYLENE FROM DRY CLEANED FABRICS  

EPA Science Inventory

The paper gives results of an evaluation of emissions of perchloroethylene (tetrachloroethylene) from dry cleaned fabrics to determine: how introducing fresh dry cleaning into a home affects the indoor concentration of perchloroethylene, and the effectiveness of "airing out" dry ...

30

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

SciTech Connect

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.

Thome, T.L.; Fullerton, K.L.; Lee, S. [Univ. of Akron, OH (United States). Dept. of Chemical Engineering

1996-12-31

31

Cosolvent-enhanced chemical oxidation of perchloroethylene by potassium permanganate.  

PubMed

A laboratory study was conducted to examine cosolvent-enhanced in-situ chemical oxidation (ISCO) of perchloroethylene (PCE) using potassium permanganate (KMnO4). The conceptual basis for this new technique is to enhance permanganate oxidation of dense non-aqueous phase liquids (DNAPLs) with the addition of a cosolvent, thereby increasing DNAPL solubility while avoiding mobilization. Among 17 cosolvent candidates screened, tertiary butyl alcohol (TBA) and acetone were the most stable in the presence of KMnO4, both of which increased PCE aqueous solubility significantly, and therefore are suitable to be used as cosolvent in this study. Batch experiments indicated that the second-order rate constant for PCE oxidation by potassium permanganate was 0.043+/-0.002 M(-1) s(-1) in the purely aqueous (no cosolvent) solution. In the presence of 20% cosolvent (volume fraction=fc=0.2), the rate constant decreased to 0.036+/-0.003 M(-1) s(-1) with TBA and to 0.031+/-0.002 M(-1) s(-1) with acetone. However, in the presence of free-phase PCE, chloride ion concentration from PCE oxidation in acetone/water solutions (fc=0.2) was about twice that in aqueous solutions, indicating that the increase in PCE solubility more than compensated for the decrease in reaction rate constant, such that the oxidation efficiency of PCE was increased with cosolvent. A complete chlorine mass balance was observed in the aqueous system, whereas approximately 70% was obtained in TBA/water or acetone/water (fc=0.2). In soil columns containing residual DNAPL and subjected to isocratic flushing with step-wise increases in f(c) cosolvent, TBA at fc=0.2 resulted in PCE mobilization, whereas acetone at fc

Zhai, Xihong; Hua, Inez; Rao, P Suresh C; Lee, Linda S

2006-01-01

32

Renal function in dry cleaning workers exposed to perchloroethylene  

SciTech Connect

Perchloroethylene (PCE) is a widely used dry cleaning and degreasing solvent. Although there is evidence in animals and humans for renal effects at extremely high doses, there are few studies of its potential renal toxicity at typical occupational concentrations. This study reports on the relationship of PCE in breath and estimates of chronic exposure with the urinary ratios of total urinary protein, albumin, and n-acetyl-glucosaminidase (NAG) to creatinine in dry cleaning workers exposed to PCE. Regression models including one or more exposure variables, demographic variables, mean arterial blood pressure (MAP), and the presence of diseases affecting kidney function were examined. Urine samples, breath samples, exposure histories, and medical histories were obtained from 192 dry cleaning workers. The results failed to demonstrate any consistent relationship between exposure and renal outcome variables. However, protein/creatinine and albumin/creatinine were significantly, although weakly and positively, associated with MAP; NAG/creatinine was weakly but significantly positively associated with age; mean NAG/creatinine was also higher in non-whites. The reasons why an association between exposure and renal outcome was not found are discussed.

Solet, D.; Robins, T.G. (School of Public Health, University of Michigan, Ann Arbor (United States))

1991-01-01

33

Possible involvement of glutathione and p53 in trichloroethylene- and perchloroethylene-induced lipid peroxidation and apoptosis in human lung cancer cells  

Microsoft Academic Search

Trichloroethylene (TCE) and perchloroethylene (PERC) are volatile organic compounds (VOCs) that are primarily inhaled through the respiratory system. The aim of this study was to elucidate the role of glutathione (GSH) and p53 in TCE- and PERC-induced lung toxicity. Human lung adenocarcinoma cells NCI-H460 (p53-wild-type) have constitutively lower levels of GSH than NCI-H1299 (p53-null) cells. The results showed that exposure

Shiang-Jiuun Chen; Jia-Lin Wang; Jian-Hung Chen; Rong-Nan Huang

2002-01-01

34

Surfactant enhanced removal of PCE in a nominally two-dimensional, saturated, stratified porous medium  

NASA Astrophysics Data System (ADS)

Although surfactant enhanced remediation of nonaqueous phase liquids (NAPLs) by pump-and-treat technology has been studied extensively in the laboratory with one-dimensional columns, very few multi-dimensional investigations have been reported. In this study we focus on the removal of perchloroethylene (PCE) from a two-dimensional, saturated porous medium containing a low permeability sand layer situated in an otherwise high permeability sand. A PCE spill was applied at the surface of the porous medium and allowed to redistribute until static equilibrium was achieved. The porous medium was then flushed with various surfactant and co-solvent formulations injected at the PCE source location and extracted at the bottom of the porous medium using a configuration similar to that of Abdul and Ang [Abdul, S.A., Ang, C.C., 1994. In situ surfactant washing of polychlorinated biphenyls and oils from a contaminated field site: Phase II. Pilot study. Ground Water 32, 727-734]. Effluent samples were analyzed for dissolved PCE concentrations. Volumetric water and PCE content values were determined at a number of locations by means of dual-energy gamma radiation measurements. Once surfactant flushing had started, PCE moved as a distinct separate phase ahead of the surfactant front. Most of this downward moving PCE accumulated on top of the low permeability sand layer. Some PCE, however, passed quickly through this layer and subsequently through the high permeability sand below it. Movement of some of the PCE into and through the low permeability sand layer was attributed to local heterogeneities combined with reduced interfacial tensions associated with the surfactant formulation. Clean-up of PCE in most of the high permeability sand was considered to be effective. PCE accumulated on top of the fine layer, however, posed a significant challenge to remediation and required several pumping configurations and surfactant/co-solvent formulations before most of it was removed.

Walker, R. C.; Hofstee, C.; Dane, J. H.; Hill, W. E.

1998-10-01

35

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

PubMed Central

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

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

2009-01-01

36

In situ biodegradation of perchloroethylene in constructed wetland mesocosms  

SciTech Connect

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.

Hoylman, A.M.; Rosensteel, B.A.; Trettin, C.C. [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.

1994-12-31

37

Removal of perchloroethylene from a layered soil system by steam flushing  

SciTech Connect

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.

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

1999-10-01

38

Biostimulation of indigenous communities for the successful dechlorination of tetrachloroethene (perchloroethylene)-contaminated groundwater.  

PubMed

Chlorinated ethenes are of environmental concern with most reports of successful microbial-mediated remediation being associated with major dechlorinating groups such as Dehalococcoides (Dhc) species. However, limited information is available on the community dynamics and dechlorinating activities of indigenous non-Dhc groups. Here, we present evidence of dechlorination of tetrachloroethene (perchloroethylene, PCE) in groundwater samples by indigenous microbial communities. 100 % PCE conversion to ethene was observed in acetate-stimulated 24 week-microcosms (controls; 15 %). Microbial community profiles showed dominance by groups such as Proteobacteria, Spirochaetes, Firmicutes, Methanomicrobiaceae and Methanosarcinaceae. Pareto-Lorenz (PL) analyses suggested an adapted (45 % PL value) but variable bacterial community (55.5 % ? t(week)) compared to Archaea (25 % PL value; 46.9 % ? t(week)). Our findings provide evidence of dechlorinating potential of indigenous microorganisms and useful information on their dynamics which may be exploited for in situ groundwater bioremediation. PMID:24101252

Patil, Sayali S; Adetutu, Eric M; Aburto-Medina, Arturo; Menz, Ian R; Ball, Andrew S

2014-01-01

39

Evolving TCE Biodegraders  

NSDL National Science Digital Library

A hypothetical scenario is introduced in which the class is asked to apply their understanding of the forces that drive natural selection to prepare a proposal along with an environmental consulting company to help clean up an area near their school that is contaminated with trichloroethylene (TCE). Students use the Avida-ED software application to test hypotheses for evolving (engineering) a strain of bacteria that can biodegrade TCE, resulting in a non-hazardous clean-up solution. Conduct this design challenge activity after completion of the introduction to digital evolution activity, Studying Evolution with Digital Organisms.

Bio-Inspired Technology and Systems (BITS) RET,

40

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 ...

41

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...

42

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...

43

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

SciTech Connect

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.

Eskenazi, B.; Wyrobek, A.J.; Fenster, L.; Katz, D.F.; Sadler, M.; Lee, J.; Hudes, M.; Rempel, D.M. (Program of Maternal and Child Health, School of Public Health, University of California, Berkeley (United States))

1991-01-01

44

The PACSAT Communications Experiment (PCE)  

SciTech Connect

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.

Not Available

1993-02-12

45

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...

46

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

USGS Publications Warehouse

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.

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

1993-01-01

47

FTIR quantification of industrial hydraulic fluids in perchloroethylene  

NASA Technical Reports Server (NTRS)

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.

Mehta, Narinder K.

1993-01-01

48

Physical cleaning of coal using perchloroethylene as heavy medium  

SciTech Connect

Use of perchloroethylene solvent in the physical cleaning of finely crushed coal has been studied in a glass tube batch apparatus. The density of perchloroethylene makes it an ideal heavy medium for float/sink separation processes. Float/sink removal of pyrites and mineral matter has been studied to determine the effect of process variables. The effect of various parameters is studied, such as mean residence time, solvent-to-coal ratio, and heavy medium density. The density of the perchloroethylene solvent is varied using kerosene to study the effects of medium density. The test results are used to assess the effectiveness of perchloroethylene as a heavy medium for the removal of pyritic sulfur from the coal. The data is used to develop a model of the process for use in scale-up and plant studies.

Thome, T.L.; Fullerton, K.L.; Lee, S. [Univ. of Akron, OH (United States). Dept. of Chemical Engineering

1994-12-31

49

Photolysis, Sonolysis, and Photosonolysis of Trichloroethane (TCA), Trichloroethylene (TCE), and Tetrachloroethylene (PCE) Without Catalyst  

Microsoft Academic Search

Photolysis, sonolysis, and photosonolysis of common groundwater contaminants, namely 1,1,1-trichloroethane, trichloroethylene,\\u000a and tetrachloroethylene, were investigated using a flow-through photosono reactor system. Simulated groundwater containing\\u000a the chlorinated volatile organic compounds (VOCs) was exposed to ultraviolet light (UV), ultrasonication (US), and UV and\\u000a US concurrently (UVUS), without a photo catalyst. VOC removal efficiencies of the UV, US, and UVUS treatment processes were

Chikashi Sato

2011-01-01

50

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 ...

51

Exposure Assessment to Trichloroethylene and Perchloroethylene for Workers in the Dry Cleaning Industry  

Microsoft Academic Search

Perchloroethylene and trichloroethylene are two particular organochloro compounds, are often used for dry-cleaning. In the\\u000a present study the excretion of urinary Perchloroethylene and trichloroethylene were evaluated as biomarkers of exposure to\\u000a these compounds. The mean value of Perchloroethylene in breathing zone and the total Perchloroethylene uptake during the work\\u000a shift of the three groups of dry-cleaning workers according to the

Noushin Rastkari; Masud Yunesian; Reza Ahmadkhaniha

2011-01-01

52

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...

53

Physiological Adaptation of Desulfitobacterium hafniense Strain TCE1 to Tetrachloroethene Respiration?†  

PubMed Central

Desulfitobacterium spp. are ubiquitous organisms with a broad metabolic versatility, and some isolates have the ability to use tetrachloroethene (PCE) as terminal electron acceptor. In order to identify proteins involved in this organohalide respiration process, a comparative proteomic analysis was performed. Soluble and membrane-associated proteins obtained from cells of Desulfitobacterium hafniense strain TCE1 that were growing on different combinations of the electron donors lactate and hydrogen and the electron acceptors PCE and fumarate were analyzed. Among proteins increasingly expressed in the presence of PCE compared to fumarate as electron acceptor, a total of 57 proteins were identified by mass spectrometry analysis, revealing proteins involved in stress response and associated regulation pathways, such as PspA, GroEL, and CodY, and also proteins potentially participating in carbon and energy metabolism, such as proteins of the Wood-Ljungdahl pathway and electron transfer flavoproteins. These proteomic results suggest that D. hafniense strain TCE1 adapts its physiology to face the relative unfavorable growth conditions during an apparent opportunistic organohalide respiration. PMID:21478312

Prat, Laure; Maillard, Julien; Grimaud, Régis; Holliger, Christof

2011-01-01

54

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...

55

Occupational Exposure to Perchloroethylene in the Dry Cleaning Industry  

Microsoft Academic Search

Field surveys were conducted of 67 dry cleaning establishments to assess working conditions and potential for exposure to perchloroethylene, a solvent of choice in this industry. Evaluation of ventilation controls showed that 28% of cleaning machines (transfer type) did not have functioning local exhaust systems, and an additional 32% had inadequately maintained systems providing less than the recommended face velocity

BARBARA L. MATERNA

1985-01-01

56

Evaluation and Control of Perchloroethylene Exposures during Dry Cleaning  

Microsoft Academic Search

A study was conducted at a large, commercial dry cleaner to evaluate the control of worker exposure to perchloroethylene (PERC) and provide recommendations to reduce exposure. This shop used a dry-to-dry machine that had a refrigerated condenser, which operated during the dry cycle, as the primary vapor recovery device. A small fan that was ducted to a carbon canister was

Gary S. Earnest

1996-01-01

57

Potential of the TCE-degrading endophyte Pseudomonas putida W619TCE to improve plant growth and reduce TCE phytotoxicity and evapotranspiration in poplar cuttings  

Microsoft Academic Search

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

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

2010-01-01

58

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

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.

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

2010-09-01

59

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

60

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...

61

Temperature dependence of the emission of perchloroethylene from dry-cleaned fabrics  

SciTech Connect

The article discusses an evaluation of the emission of perchloroethylene (tetrachloroethylene) from freshly dry cleaned fabrics using small environmental test chambers. The temperature dependence of the release of perchloroethylene was evaluated over a temperature range of 20 to 45 C. A linear relation exists between the logarithm of perchloroethylene retention time and the reciprocal of the absolute temperature. Study results for 100% wool and 55% polyester/45% wool indicate that airing out freshly dry cleaned fabrics at above ambient temperature will increase the rate at which perchloroethylene is emitted from the fabrics.

Guo, Z.; Tichenor, B.A.; Mason, M.A.; Plunket, C.M.

1990-01-01

62

Assessing Occupational Exposure to Perchloroethylene in Dry Cleaning  

Microsoft Academic Search

Occupational exposure to perchloroethylene (PERC) in dry cleaning is analyzed by calculating airborne concentrations for a large set of possible exposure scenarios. Different generations of dry-cleaning machines ranging from vented machines used until the 1980s to nonvented closed-loop machines used since the 1990s are investigated; the geographical scope of the study is Germany. Concentrations are calculated for diffuse emissions, release

Julia von Grote; Christian Hürlimann; Martin Scheringer; Konrad Hungerbühler

2006-01-01

63

Exposure assessment to trichloroethylene and perchloroethylene for workers in the dry cleaning industry.  

PubMed

Perchloroethylene and trichloroethylene are two particular organochloro compounds, are often used for dry-cleaning. In the present study the excretion of urinary Perchloroethylene and trichloroethylene were evaluated as biomarkers of exposure to these compounds. The mean value of Perchloroethylene in breathing zone and the total Perchloroethylene uptake during the work shift of the three groups of dry-cleaning workers according to the capacity of the dry-cleaning machine (8, 12 and 18 kg) were 31.04, 50.87 and 120.99 mg m(-3) and 11.46, 22.6 and 41.6 ?g L(-1), respectively, which were significantly greater than the occupationally nonexposed groups. A good correlation (r = 0.907) between the mean values of Perchloroethylene in breathing zone and the urinary concentrations was observed. PMID:21416139

Rastkari, Noushin; Yunesian, Masud; Ahmadkhaniha, Reza

2011-04-01

64

Phytoremediation of trichloroethene (TCE) using cottonwood trees  

USGS Publications Warehouse

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.

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

1999-01-01

65

Remediation of sites contaminated with TCE  

SciTech Connect

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, a known carcinogen. This has generated a high degree of interest in efficient and cost-efficient technologies that can be used to remediate soil and groundwater contaminated with TCE. The purpose of the paper is to present and discuss relevant physicochemical properties and reactive mechanisms of TCE, and to delineate and discuss promising remediation methodologies that have been proposed and/or demonstrated for restoring contaminated subsurface environments.

Russell, H.H.; Matthews, J.E.; Sewell, G.W.

1991-01-01

66

ISIS Protocol Extensions for Path Computation Element (PCE) Discovery  

Microsoft Academic Search

There are various circumstances where it is highly desirable for a Path Computation Client (PCC) to be able to dynamically and automatically discover a set of Path Computation Elements (PCEs), along with information that can be used by the PCC for PCE selection. When the PCE is a Label Switching Router (LSR) participating in the Interior Gateway Protocol (IGP), or

Y. Ikejiri; NTT Communications; R. Zhang

67

LABORATORY AND FIELD SCALE BIOREMEDATION OF TETRACHLOROETHENE (PCE) CONTAMINATED GROUNDWATER  

Microsoft Academic Search

Bioremediation studies were conducted at a tetrachloroethene contaminated site located in Manhattan Kansas. A former dry cleaning facility was in operation for 30 years. Shallow and deep aquifers down gradient from contaminated site were found to be contaminated with PCE and it's degradation products all above their Maximum Contamination Limits (MCL's). PCE concentration in groundwater at the pilot study area

J. Ibbini; S. Santharam; L. C. Davis; L. E. Erickson

68

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

PubMed Central

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

2012-01-01

69

Activated carbon adsorption of trichloroethylene (TCE) vapor stripped from TCE-contaminated water  

Microsoft Academic Search

Ground water contaminated with trichloroethylene (TCE) used in electronic, electric, dry cleaning and the like industries is often treated by air-stripping. In this treatment process, TCE in its vapor form is stripped from ground water by air stream and sometimes emitted into the atmosphere without any additional treatments. Activated carbon adsorption is one of the practical and useful processes for

Yusaku Miyake; Akiyoshi Sakoda; Hiroaki Yamanashi; Hirotaka Kaneda; Motoyuki Suzuki

2003-01-01

70

Health Assessment Document for Tetrachloroethylene (Perchloroethylene) (Final Report)  

EPA Science Inventory

Tetrachloroethylene (PCE) is a volatile solvent with important commercial applications. It has been detected in the ambient air of a variety of urban and nonurban areas of the United States. It has less frequently been detected in water but has been monitored generally at levels ...

71

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...

72

Engineering TCE-Degrading Rhizobacteria for Heavy Metal  

E-print Network

Engineering TCE-Degrading Rhizobacteria for Heavy Metal Accumulation and Enhanced TCE Degradation are currently co-contami- nated with organic pollutants such as trichloroethene (TCE) and heavy metals that will survive and thrive in soil heavily polluted with heavy metals. In this work, a gene coding for the metal

Chen, Wilfred

73

Occupational exposure to perchloroethylene in dry-cleaning shops in Tehran, Iran.  

PubMed

Perchloroethylene, the most widely used solvent in dry cleaning, is toxic to the liver, kidneys and central nervous system and may be a human carcinogen. An exposure assessment was carried out in 69 dry-cleaning shops using perchloroethylene in Tehran city, Iran. The 8-h time weighted average (TWA) breathing zone air samples and end-exhaled air samples were obtained from 179 workers who worked as the job titles included machine operator (n=71), presser (n=63) and counter area (clerk) (n=45). The mean perchloroethylene concentrations in breathing zone air were 11.5 ppm, 9.6 ppm and 7.2 ppm respectively. The mean perchloroethylene concentrations in end-exhaled air of the same participants in Saturday morning (prior to shift of workweek) were 1.7 ppm, 1.5 ppm and 1.1 ppm, but in Thursday evening (end of shift at end of workweek) were 2.4 ppm, 2.0 ppm and 1.5 ppm respectively. This study found that, the mean perchloroethylene concentrations in breathing zone air and end-exhaled air in the dry-cleaning workers were lower than the TLV (25 ppm) and BEI (5 ppm) recommended by ACGIH. Regression analysis showed that the concentration of perchloroethylene in breathing zone air (TWA) was highly and significantly correlated with the concentration of perchloroethylene in end-exhaled air in Saturday morning with a regression equation Y=0.147X + 0.031 (r=0.99, p<0.001) and also in Thursday evening with a regression equation Y=0.201X + 0.072 (r=0.98, p<0.001) where X is the concentration of perchloroethylene in breathing zone air and Y is that the concentration of perchloroethylene in end-exhaled air. The results also showed the potential utility of measuring the concentration of perchloroethylene in end-exhaled air as a method for assessing relative exposure in dry cleaning shops which use it. PMID:19367044

Azimi Pirsaraei, Seyed Reza; Khavanin, Ali; Asilian, Hassan; Soleimanian, Ardalan

2009-04-01

74

Personal Continuing Education (PCE) for the Graduate Veterinarian  

E-print Network

Personal Continuing Education (PCE) for the Graduate Veterinarian 1. Intensive Training Continuing: The veterinarian can participate as part of the student group rotation. They can attend rounds, observe case (practicing veterinarian) will provide all financial resources for fees, health services, transportation

Ghajar, Afshin J.

75

Complex electrical resistance tomography of a subsurface PCE plume  

Microsoft Academic Search

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

A. Ramirez; W Daily; D. LeBrecque

1996-01-01

76

Well Installation and Sampling Report for Monitoring Wells TCM6 TCM7, and TNX 28D - 40D and GeoSiphon Cell TGSC-2  

SciTech Connect

The shallow groundwater and sediments beneath the TNX Area are contaminated with both dissolved and residual chlorinated volatile organic compounds (CVOCs) such as trichloroethylene (TCE), carbon tetrachloride and perchloroethylene (PCE). The Savannah River Technology Center (SRTC) is studying a new technology for remediating CVOCs known as GeoSiphon.

Nichols, R.L.

1999-09-20

77

Design and construction techniques for permeable reactive barriers  

Microsoft Academic Search

Adequate site characterization, bench-scale column testing, and hydrogeologic modeling formed the basis for the design and construction of permeable reactive barriers for groundwater remediation at various sites, such as Dover Air Force Base, DE and Naval Air Station, Moffett Field, CA. Dissolved chlorinated solvents, such as perchloroethylene (PCE) and trichloroethylene (TCE), have been the focus at many sites because the

Arun R. Gavaskar

1999-01-01

78

Perchloroethylene detection in air: a comparative study using polymer sensor elements and catalyst/sensor systems  

NASA Astrophysics Data System (ADS)

In a first approach, perchloroethylene (C2Cl4 or 'PER') was determined quantitatively in air by monitoring mass and temperature changes of polymer-coated quartz microbalance and calorimetric transducers. The different equilibrium and time-dependent sensor responses result from reversible interactions between perchloroethylene molecules from the gas phase and chemically sensitive polymers based upon modified siloxanes. In a second approach, we determined PER by applying pattern recognition methods to evaluate data from catalyst/electrochemical sensor-systems. Here, PER is decomposed at a heated catalytic filament. The molecular fragments are detected subsequently by an electrochemical or semiconductor gas sensor. The quantitative determination of perchloroethylene in air in the ppm-range is possible by applying mathematical procedures of pattern recognition. Finally, a comparative discussion of the different transducer and evaluation principles is given for specific applications.

Schierbaum, Klaus-Dieter; Vaihinger, S.; Haug, M.; Goepel, Wolfgang

1993-03-01

79

TCE degradation in a methanotrophic attached-film bioreactor  

Microsoft Academic Search

Trichloroethene was degraded in expanded-bed bioreactors operated with mixed-culture methanotrophic attached films. Biomass concentrations of 8 to 75 g volatile solids (VS) per liter static bed (L[sub sb]) were observed. Batch TCE degradation rates at 35C followed the Michaelis-Menten model, and a maximum TCE degradation rate (q[sub max]) of 10.6 mg TCE\\/gVS [center dot] day and a half velocity coefficient

Donna E. Fennell; Yarrow M. Nelson; Sheila E. Underhill; Thomas E. White; William J. Jewell

1993-01-01

80

Dechlorination of PCE by mixtures of green rust and zero-valent iron  

E-print Network

in the model is as follows. C~c =CRc ? B (13) where, B is the cumulative aqueous PCE concentration removed by GRsp4. The concentration of PCE removed by GRsp4 at any time was calculated by solving the following equation. dB (k/P)C pcE (CRc B) dt 1/K+ CUE...

Marchal, Fabienne

2002-01-01

81

Complex electrical resistance tomography of a subsurface PCE plume  

SciTech Connect

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.

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

1996-01-01

82

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...

83

AMBIENT PERCHLOROETHYLENE LEVELS INSIDE COIN-OPERATED LAUNDRIES WITH DRYCLEANING MACHINES ON THE PREMISES  

EPA Science Inventory

In this study, ambient perchloroethylene (PERC) levels were measured inside and in the vicinity of six self serve laundries containing coin-type dry cleaning operations. Inside two of the laundries, evaluations of organic vapor monitoring badges were performed in addition to the ...

84

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...

85

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...

86

Effects of Retrofit Emission Controls and Work Practices on Perchloroethylene Exposures in Small Dry-Cleaning Shops  

Microsoft Academic Search

The effectiveness of commercially available interventions for reducing workers' perchloroethylene exposures in three small dry-cleaning shops was evaluated. Depending upon machine configuration, the intervention consisted of the addition of either a refrigerated condenser or a closed-loop carbon adsorber to the existing dry-cleaning machine. These relatively inexpensive (less than $5000) engineering controls were designed to reduce perchloroethylene emissions when dry-cleaning machine

Lynda M. Ewers; Avima M. Ruder; Martin R. Petersen; G. Scott Earnest; Linda M. Goldenhar

2002-01-01

87

Complex electrical resistance tomography of a subsurface PCE plume  

SciTech Connect

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 from 4 vertical electrode arrays, each with 10 electrodes spaced between 3 m and 0.5 m depth. 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. Images showing phase changes caused by the spill are also presented. The phase changes at 64 Hz suggest that the DNAPL spill increased the induced polarization (IP) effect of the clay layers.

Ramirez, A.; Daily W. [Lawrence Livermore National Laboratory, CA (United States); LaBrecque, D. [Univ. of Arizona, Tucson, AZ (United States)

1996-11-01

88

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...

89

A Control Technology Evaluation of State-of-the-Art, Perchloroethylene Dry-Cleaning Machines  

Microsoft Academic Search

NIOSH researchers evaluated the ability of fifthgeneration dry-cleaning machines to control occupational exposure to perchloroethylene (PERC). Use of these machines is mandated in some countries; however, less than 1 percent of all U.S. shops have them. A study was conducted at a U.S. dry-cleaning shop where two fifth-generation machines were used. Both machines had a refrigerated condenser as a primary

G. Scott Earnest

2002-01-01

90

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

PubMed

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

Groves, William A; Achutan, Chandran

2004-12-01

91

Use of a Plasma Cathode Electron (PCE) source in an Electron Beam Integrated Thruster (EBIT)  

Microsoft Academic Search

The electron Beam Integrated Thruster (EBIT) plasma propulsion concept centers around the use of an electron beam to ionize a propellant; a more efficient ionization mechanism than conventional electric propulsion concepts. In this paper we outline the EBIT concept, in particular, the generation of the electron beam in a Plasma Cathode Electron (PCE) source. The PCE beam source utilizes a

Max Light; Tsitsi Madziwa-Nussinov; Pat Colestock; Ron Kashuba; Rick Faehl

2006-01-01

92

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...

93

Drip Irrigation Aided Phytoremediation for Removal of TCE from Groundwater  

SciTech Connect

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).

Wilde, E.W.

2003-04-24

94

Socioeconomic disparities in indoor air, breath, and blood perchloroethylene level among adult and child residents of buildings with or without a dry cleaner.  

PubMed

In many cities, dry cleaners using perchloroethylene are frequently located in multifamily residential buildings and often cause elevated indoor air levels of perchloroethylene throughout the building. To assess individual perchloroethylene exposures associated with co-located dry cleaners, we measured perchloroethylene in residential indoor air, and in blood and breath of adults and children residing in buildings with a dry cleaner as part of the New York City (NYC) Perc Project. We also measured perchloroethylene in indoor air, and in blood and breath of residents of buildings without a dry cleaner for comparison. Here, we evaluate whether an environmental disparity in perchloroethylene exposures is present. Study participants are stratified by residential building type (dry cleaner or reference) and socioeconomic characteristics (race/ethnicity and income); measures of perchloroethylene exposure are examined; and, the influence of stratified variables and other factors on perchloroethylene exposure is assessed using multivariate regression. All measures of perchloroethylene exposure for residents of buildings with a dry cleaner indicated a socioeconomic disparity. Mean indoor air perchloroethylene levels were about five times higher in minority (82.5 ug/m(3)) than in non-minority (16.5 ug/m(3)) households, and about six times higher in low-income (105.5 ug/m(3)) than in high income (17.8 ug/m(3)) households. Mean blood perchloroethylene levels in minority children (0.27 ng/mL) and adults (0.46 ng/mL) were about two and three times higher than in non-minority children (0.12 ng/mL) and adults (0.15 ng/mL), respectively. Mean blood perchloroethylene levels in low income children (0.34 ng/mL) and adults (0.62 ng/mL) were about three and four times higher than in high income children (0.11 ng/mL) and adults (0.14 ng/mL), respectively. A less marked socioeconomic disparity was observed in perchloroethylene breath levels with minority and low income residents having slightly higher levels than non-minority and high income residents. Multivariate regression affirmed that indoor air perchloroethylene level in dry cleaner buildings was the single most important factor determining perchloroethylene in blood and breath. Neither age, gender, nor socioeconomic status significantly influenced perchloroethylene levels in breath or blood. We previously reported that increased indoor air, breath, and blood perchloroethylene levels among NYC Perc Project child participants were associated with an increased risk for slightly altered vision. Thus, the disproportionately elevated perchloroethylene exposures of minority and low-income child residents of buildings with a dry cleaner shown here constitutes an environmental exposure disparity with potential public health consequences. Among residents of buildings without a dry cleaner, we observed some small increases in perchloroethylene breath and blood levels among non-minority or high income residents compared to minority or low income residents. These differences were not attributable to differences in indoor air levels of perchloroethylene which did not differ across socioeconomic categories, but appear to be associated with more frequent exposures dry cleaned garments. PMID:23453848

Storm, Jan E; Mazor, Kimberly A; Shost, Stephen J; Serle, Janet; Aldous, Kenneth M; Blount, Benjamin C

2013-04-01

95

Global Gene Expression of Dehalococcoides Within a Robust Dynamic TCE-Dechlorinating  

E-print Network

contaminant (US EPA, 2001; US HHS, 2007) and human carcinogen (US EPA, 2011), has been an ongoing challenge since TCE first received regulatory attention in the 1980s. In groundwater environments, TCE

Alvarez-Cohen, Lisa

96

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...

97

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...

98

Cometabolic Degradation of TCE Vapors in a Foamed Emulsion  

E-print Network

Cometabolic Degradation of TCE Vapors in a Foamed Emulsion Bioreactor E U N S U N G K A N A N D M)vaporsinanovelgas-phasebioreactorcalledthefoamed emulsion bioreactor (FEBR) was demonstrated. Toluene vapors were used as the primary growth substrate-phase bioreactor called the foamed emulsion bioreactor (FEBR) was developed (20). The FEBR consists of an emulsion

99

Fenton Oxidation of TCE Vapors in a Foam Reactor  

E-print Network

peroxide (H2O2) yielding hydroxyl radicals (HOÁ, hereafter), one of the strongest and least specific oxi, and relatively low costs. The mechanism of Fenton oxida- tion involves oxidation of Fe2þ to Fe3þ by hydrogenFenton Oxidation of TCE Vapors in a Foam Reactor Eunsung Kan,a,b Seongyup Kim,a and Marc A

100

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...

101

Demonstration of a resilient PCE\\/GMPLS controlled translucent optical network  

Microsoft Academic Search

A resilient translucent optical network controlled by a PCE and extended GMPLS controllers was successfully demonstrated, while quantitatively evaluating the path computation latency and service disruption time during end-to-end lightpath restoration.

Lei Liu; Takehiro Tsuritani; Ramon Casellas; Munefumi Tsurusawa

2010-01-01

102

Effectiveness of nanoscale zero-valent iron for treatment of a PCE-DNAPL source zone  

NASA Astrophysics Data System (ADS)

Nanoscale zero-valent iron (nZVI) has received considerable attention as a potential in situ remediation technology for treating chlorinated solvent source zones. Experimental and mathematical modeling studies were conducted to investigate the performance of nZVI in the transformation of tetrachloroethene (PCE) entrapped as a dense nonaqueous phase liquid (DNAPL). Injection of a 60 g/L suspension of nZVI into a column containing 20-30 mesh Ottawa sand and PCE-DNAPL at a residual saturation of 5.5% resulted in a uniform distribution of nZVI and minimal displacement of PCE. Subsequent flushing with 267 pore volumes of water containing 3 mM CaCl 2 at a Darcy velocity of 0.75 m/day resulted in steady-state effluent concentrations of PCE near the solubility limit (ca. 200 mg/L) and production of dissolved-phase ethene (10-30 mg/L). Over the duration of the experiment, approximately 30% of the initial PCE-DNAPL mass reacted to form ethene, 50% was eluted as dissolved-phase PCE, and 20% remained in the column as PCE-DNAPL. To further explore the implications of the nZVI column results, a multiphase transport model was developed that incorporated rate-limited PCE-DNAPL dissolution and reactions with nZVI. Using a fitted pseudo first-order transformation rate coefficient of 1.42 1/h, the model accurately captured observed trends in effluent concentrations of PCE and ethene and overall mass balance. A model sensitivity study reveals a strong dependence of treatment effectiveness on system characteristics. The sensitivity analysis suggests that an increase in the extent of PCE transformation is facilitated by decreasing flow rate, emplacement of nZVI down-gradient of the DNAPL source zone, and decreasing length of the DNAPL source zone. These findings indicate that, although emplacement of high concentrations of nZVI within a PCE-DNAPL source zone can result in substantial transformation of the parent compound, careful attention to design parameters (e.g. flow rate, location and amount nZVI delivered) will be required to achieve complete conversion to benign reaction products.

Taghavy, Amir; Costanza, Jed; Pennell, Kurt D.; Abriola, Linda M.

2010-11-01

103

Enhanced reductive dechlorination of PCE DNAPL with TBOS as a slow-release electron donor  

Microsoft Academic Search

Tetrabutoxysilane (TBOS), which yields 1-butanol upon abiotic hydrolysis, was evaluated as a slow-release substrate for the reductive dechlorination of tetrachloroethylene (PCE) as a dense non-aqueous-phase liquid (DNAPL). Dechlorination was achieved using an anaerobic binary mixed (BM) culture, which consisted of the Pt. Mugu (PM) and the Evanite (EV) mixed cultures. In batch reactor experiments, TBOS was mixed with PCE DNAPL

Seungho Yu; Lewis Semprini

2009-01-01

104

GeneCARD-FISH: Detection of tceA and vcrA reductive dehalogenase genes in Dehalococcoides mccartyi by fluorescence in situ hybridization.  

PubMed

Due to the direct involvement in the biodegradation of chlorinated solvents, reductive dehalogenase genes (RDase) are considered biomarkers of the metabolic potential of different strains of Dehalococcoides mccartyi (Dhc). This is known to be the only microbe able to completely reduce toxic chlorinated solvents to harmless ethene. In the last years, several Molecular Biological Tools (MBTs) have been developed to optimize the detectability of Dhc cells and/or the RDase genes, with particular attention to the most important indicators of ethene formation, namely tceA and vcrA genes. Despite qPCR has been indicated as the MBT of choice, the use of CARD-FISH recently demonstrated to provide a more accurate quantification of Dhc cells in a wide concentration range, overcoming the drawbacks of loosing nucleic acids during the preparation of the sample associated with qPCR. CARD-FISH assays usually target 16S rRNA and up to date no protocol able to discriminate different Dhc strains by detecting RDase genes has been developed. This study reports the first evidence of in situ detection of tceA and vcrA genes into Dhc cells by applying a new procedure named geneCARD-FISH. Dhc strains carrying tceA and vcrA genes were identified and quantified in a PCE-to-ethene dechlorinating microbial enrichment and overall they represented 58.63%±2.45% and 40.46%±1.86% of the total Dhc cells, respectively. These values were markedly higher than those obtained by qPCR, which strongly underestimated the actual concentration of vcrA gene (0.08%±0.01% of Dhc 16S rRNA gene copies). The assay was successfully applied also for the analysis of environmental samples and remarkably strengthens the biomonitoring activities at field scale by providing the specific in situ discrimination of Dhc cells carrying the key-RDase genes. PMID:25595619

Matturro, B; Rossetti, S

2015-03-01

105

Dissolution Coupled Biodegradation of Pce by Inducing In-Situ Biosurfactant Production Under Anaerobic Conditions  

NASA Astrophysics Data System (ADS)

Biosurfactants have proven to enhance the bioavailability and thereby elevate the rate of degradation of Light Non Aqueous Phase Liquids (LNAPLs) such as crude oil and petroleum derivatives. In spite of their superior characteristics, use of these biomolecules for remediation of Dense Non Aqueous Phase Liquids (DNAPLs) such as chlorinated solvents is still not clearly understood. In this present study, we have investigated the fate of tetrachloroethylene (PCE) by inducing in-situ biosurfactants production, a sustainable option which hypothesizes increase in bioavailability of LNAPLs. In order to understand the effect of biosurfactants on dissolution and biodegradation under the inducement of in-situ biosurfactant production, batch experiments were conducted in pure liquid media. The individual influence of each process such as biosurfactant production, dissolution of PCE and biodegradation of PCE were studied separately for getting insights on the synergistic effect of each process on the fate of PCE. Finally the dissolution coupled biodegradation of non aqueous phase PCE was studied in conditions where biosurfactant production was induced by nitrate limitation. The effect of biosurfactants was differentiated by repeating the same experiments were the biosurfactant production was retarded. The overall effect of in-situ biosurfactant production process was evaluated by use of a mathematical model. The process of microbial growth, biosurfactant production, dissolution and biodegradation of PCE were translated as ordinary differential equations. The modelling exercise was mainly performed to get insight on the combined effects of various processes that determine the concentration of PCE in its aqueous and non-aqueous phases. Model simulated profiles of PCE with the kinetic coefficients evaluated earlier from individual experiments were compared with parameters fitted for observations in experiments with dissolution coupled biodegradation process using optimization routines. Complete disappearance of PCE from DNAPL and aqueous phase was observed in a span of 14 days in systems triggered with biosurfactant production through enhanced dissolution and biodegradation. Synergistic effect of dissolution process towards biodegradation was observed as bioavailability of PCE was increased by 3.1 times in systems with biosurfactant production. Modelling studies illustrate that biodegradation on the other hand synergistically enhanced dissolution by elevating the dissolution rates by 1.4 times. This study also suggests a mass transfer phenomenon is greatly influenced not only by surface active molecules but by microbes as well.

Dominic, J.; Nambi, I. M.

2013-12-01

106

Reaction products and mass balances from irradiated TCE vapor  

SciTech Connect

Trichloroethylene (TCE) vapor, at a concentration of 3000 ppmv in synthetic air, was sealed in Tedlar bags and irradiated with a 3.7 MeV electron beam. Bags of dry vapor and vapor at 90% relative humidity were irradiated. Doses up to 11 megarads (11 MR) were applied. Each bag was chemically analyzed for reaction products and a mass balance of the chlorine and carbon was obtained within the 11 MR dose range. The results of these radiolysis experiments and chemical analysis show that, given the proper treatment, the TCE concentration is reduced to below detection limit and the reaction products of the organic carbon and chlorine are carbon monoxide (CO), carbon dioxide (CO{sub 2}), chlorine gas (Cl{sub 2}) and hydrochloric acid (140). No detectable amounts of dichloroacetyl chloride (DCAC) or phosgene (PG) remained in the sample after proper treatment. DCAC and PG were found only as intermediary oxidation products of the TCE. High energy ionizing radiation, as electron beams and bremsstrahlung, is a new treatment technology for destroying toxic compounds and hazardous Wastes. A demonstration of complete destruction of organic products, using this treatment at standard temperature and pressure, is expected to help implement the use of this technology.

Matthews, S.M.; Wang, F.T. [Lawrence Livermore National Lab., CA (United States); Mill, T. [SRI International, Menlo Park, CA (United States)] [and others

1995-12-31

107

Enhanced Reductive Dechlorination of TCE in a Basalt Aquifer  

SciTech Connect

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.

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

1999-04-01

108

Enhanced Reductive Dechlorination of TCE in a Basalt Aquifer  

SciTech Connect

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.

K. S. Sorenson; L. N. Peterson (INEEL); R. Ely (U of Idaho)

1999-04-01

109

A Planet Hunters Search of the Kepler TCE Inventory  

NASA Astrophysics Data System (ADS)

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.

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

110

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

SciTech Connect

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 was evaporating through the leaves to the atmosphere. The characterization of the isolates obtained in this study shows that the bacterial community associated with Oak and Ash on a TCE-contaminated site, was strongly enriched with TCE-tolerant strains. However, this was not sufficient to degrade all TCE before it reaches the leaves. A possible strategy to overcome this evapotranspiration to the atmosphere is to enrich the plant-associated TCE-degrading bacteria by in situ inoculation with endophytic strains capable of degrading TCE.

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

2009-11-01

111

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

PubMed

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

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

2015-01-01

112

Aerobic TCE degradation by encapsulated toluene-oxidizing bacteria, Pseudomonas putida and Bacillus spp.  

PubMed

The degradation rates of toluene and trichloroethylene (TCE) by Pseudomonas putida and Bacillus spp. that were encapsulated in polyethylene glycol (PEG) polymers were evaluated in comparison with the results of exposure to suspended cultures. PEG monomers were polymerized together with TCE-degrading microorganisms, such that the cells were encapsulated in and protected by the matrices of the PEG polymers. TCE concentrations were varied from 0.1 to 1.5 mg/L. In the suspended cultures of P. putida, the TCE removal rate decreased as the initial TCE concentration increased, revealing TCE toxicity or a limitation of reducing power, or both. When the cells were encapsulated, an initial lag period of about 10-20 h was observed for toluene degradation. Once acclimated, the encapsulated P. putida cultures were more tolerant to TCE at an experimental range of 0.6-1.0 mg/L and gave higher transfer efficiencies (mass TCE transformed/mass toluene utilized). When the TCE concentration was low (e.g., 0.1 mg/L) the removal of TCE per unit mass of cells (specific removal) was significantly lower, probably due to a diffusion limitation into the PEG pellet. Encapsulated Bacillus spp. were able to degrade TCE cometabolically. The encapsulated Bacillus spp. gave significantly higher values than did P. putida in the specific removal and the transfer efficiency, particularly at relatively high TCE concentration of approximately 1.0±0.5 mg/L. The transfer efficiency by encapsulated Bacillus spp. in this study was 0.27 mgTCE/mgToluene, which was one to two orders of magnitude greater than the reported values. PMID:21045323

Kim, Seungjin; Bae, Wookeun; Hwang, Jungmin; Park, Jaewoo

2010-01-01

113

Degradation of perchloroethylene and nitrate by high-activity modified green rusts  

E-print Network

-F(Pt) was characterized using a batch reactor system. The reaction kinetics of PCE degradation by GR-F(Cu) and GR-F(Pt) was strongly dependent on pH over the range of pH 7.5-11, with the fastest rate at pH 11. Increasing concentrations of Cu(II) over the range of 0 to 5 m...

Choi, Jeong Yun

2006-10-30

114

The study of lag phase and rate improvement of TCE decay in UV\\/surfactant systems  

Microsoft Academic Search

The photodegradation of trichloroethene (TCE) in surfactant micelles was investigated. The decay of TCE was studied in the Rayonet RPR-200 merry-go-round photoreactor, at 253.7 nm monochromatic ultraviolet (UV) lamps, in the presence of surfactants. Surfactants are used as additional hydrogen sources to improve the photodegradation rates of TCE. About three times the rate increment is observed in the presence of

Wei Chu; Wing-Ki Choy

2000-01-01

115

Measurement of Perchloroethylene Indoor Air Levels Caused by Fugitive Emissions from Unvented Dry-to-Dry Dry Cleaning Units  

Microsoft Academic Search

The large emissions of perchloroethylene (PERC), a potential carcinogen, from dry cleaning establishments led the fabriccare industry to redesign dry cleaning machines. State-of-theart facilities now employ nonvented self-contained machines that do not emit vapors directly to the outside air. However, fugitive emissions in indoor environments continue to be emitted from these new machines.An indoor air quality study was conducted in

D. J. Moschandreas; D. S. O’Dea

1995-01-01

116

Preliminary Study of Propyl Bromide Exposure among New Jersey Dry Cleaners as a Result of a Pending Ban on Perchloroethylene  

Microsoft Academic Search

Many states are considering, and some states have actively pursued, banning the use of perchloroethylene (PERC) in dry cleaning establishments. Proposed legislation has led many dry cleaners to consider the use of products that contain greater than 90% n-propyl bromide (n-PB; also called 1-bromopropane or 1-BP). Very little information is known about toxicity and exposure to n-PB. Some n-PB-containing products

James D. Blando; Donald P. Schill; Mary Pauline De La Cruz; Lin Zhang; Junfeng Zhang; Vladimir Vukovic; Paulo Tabares-Velasco; Jelena Srebric; A. Abhishek; Joo-Youp Lee; Tim Keener; Y. Yang; Pat Rasmussen; H. Gardner; Jianjun Niu; Qian Tan; Guo Huang; Yanpeng Cai; Barbara George; Donald Whitaker; Robert Gilliam; Jenise Swall; Ronald Williams; Barron Henderson; Harvey Jeffries; Byeong-Uk Kim; William Vizuete; Donna Jones

2010-01-01

117

An Evaluation of Retrofit Engineering Control Interventions to Reduce Perchloroethylene Exposures in Commercial Dry-Cleaning Shops  

Microsoft Academic Search

Real-time monitoring was used to evaluate the ability of engineering control devices retrofitted on two existing dry-cleaning machines to reduce worker exposures to perchloroethylene. In one dry-cleaning shop, a refrigerated condenser was installed on a machine that had a water-cooled condenser to reduce the air temperature, improve vapor recovery, and lower exposures. In a second shop, a carbon adsorber was

G. Scott Earnest; Lynda M. Ewers; Avima M. Ruder; Martin R. Petersen; Ronald J. Kovein

2002-01-01

118

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

SciTech Connect

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.

Isalou, M; Sleep, B.E. [Univ. of Toronto, Ontario (Canada). Dept. of Civil Engineering] [Univ. of Toronto, Ontario (Canada). Dept. of Civil Engineering; Liss, S.N. [Ryerson Polytechnic Univ., Toronto, Ontario (Canada). Dept. of Applied Chemical and Biological Sciences] [Ryerson Polytechnic Univ., Toronto, Ontario (Canada). Dept. of Applied Chemical and Biological Sciences

1998-11-15

119

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

NASA Astrophysics Data System (ADS)

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.

Peng, Sheng; Wang, Ning; Chen, Jiajun

2013-10-01

120

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

PubMed

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

Peng, Sheng; Wang, Ning; Chen, Jiajun

2013-10-01

121

Degradation of perchloroethylene and dichlorophenol by pulsed-electric discharge and bioremediation  

PubMed

Pulsed electric discharge (PED) and bioremediation were combined to create a novel two-stage system which dechlorinates the halogenated pollutants, 2,4-dichlorophenol and perchloroethylene, with repetitive (0.1-1 kHz), short pulse ( approximately 100 ns), low voltage (40-80 kV) discharges and then mineralizes the less chlorinated products with aerobic bacteria. A 6.1 mM aqueous dichlorophenol sample was cycled through the PED reactor (60 kV of applied pulsed voltage and 300 Hz) 6 times, resulting in the release of 55% of the initial dichlorophenol chloride ions (1 mM Cl- removed each cycle). The respective average specific efficiency is 0.4-0.6 keV/(Cl- molecule). Pseudomonas mendocina KR1, which grows in minimal medium supplemented with phenol but not with dichlorophenol, increased in cell density in all cultures supplemented with the PED-treated DCP samples and yielded a maximum of two-fold additional Cl- released compared to the PED-related alone. The number of PED-treatment cycles, voltage, and frequency were also varied, showing that both cell densities and overall dichlorophenol dechlorination were highly dependent upon the number of PED-treatment cycles, rather than the tested voltages and frequencies. Using this two-stage treatment system, PED released 31% of the initial chloride ions from dichlorophenol (after three cycles at 40-45 kV and 1.2 kHz) while P. mendocina KR1 in the second stage increased dechlorination to 90%. These results were corroborated by the 35% additional chloride release found with activated sludge cultures. Perchloroethylene (0.6 mM) was similarly treated in a first-stage PED reactor (80% chloride removal after four cycles) followed by biodegradation of the dechlorinated products with a recombinant toluene o-monooxygenase-expressing Pseudomonas fluorescens strain. Gas chromatographic analysis showed that the PED reactor created less-chlorinated byproducts (i.e., trichloroethylene) that were removed (74%) upon exposure to the recombinant bacterium. Copyright 1998 John Wiley & Sons, Inc. PMID:10099357

Yee; Chauhan; Yankelevich; Bystritskii; Wood

1998-08-20

122

Reductive dechlorination of TCE by zero valent bimetals.  

PubMed

Six zero valent bimetal combinations were tested for trichloroethene (TCE) dechlorination. Palladium, nickel, and copper were coated at 500 mg kg(-1) or less onto zero valent iron, producing Pd/Fe, Ni/Fe, and Cu/Fe bimetals, and zinc, producing Pd/Zn, Ni/Zn, and Cu/Zn bimetals. The order of reactivity of the six bimetals and two metals based on surface area normalized pseudo first order rate constants was observed to be: Pd/Fe > Pd/Zn > Ni/Fe > Cu/Fe > Ni/Zn > Cu/Zn > Fe > Zn. Thus, in general, 1) iron metal and bimetals exhibit faster reaction rates than the corresponding zinc reductants, 2) bimetals exhibit faster reaction rates than pure metals, and 3) metal coating enhance reactivity in the order of Pd > Ni > Cu. Chlorinated intermediate products were observed in small amounts for Fe only. In all cases, the chloride balance, calculated from TCE and chloride concentrations, ranged from 90 to 111%. The results are discussed in terms of the effects of bimetal combinations on catalytic dechlorination, prevention of nonreactive film and metal corrosion. PMID:12641254

Kim, Y H; Carraway, E R

2003-01-01

123

Risk of learning and behavioral disorders following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water  

Microsoft Academic Search

This population-based retrospective cohort study examined the association between developmental disorders of learning, attention and behavior and prenatal and early postnatal drinking water exposure to tetrachloroethylene (PCE) on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling

Patricia A. Janulewicz; Roberta F. White; Michael R. Winter; Janice M. Weinberg; Lisa E. Gallagher; Veronica Vieira; Thomas F. Webster; Ann Aschengrau

2008-01-01

124

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...

125

Role of diffusion in chemical oxidation of PCE in a dual permeability system.  

PubMed

The effect of in situ chemical oxidation (ISCO) with permanganate (MnO4-) on tetrachloroethene (PCE) in a dual permeability system consisting of low permeability clay with high permeability sand lenses was investigated by two-dimensional laboratory experiments. The experiments imitate a field remediation at a former dry cleaning facility in Denmark. Results from laboratory experiments and field observations both show that after an application of MnO4- in the sand layer, the diffusion rate into the matrix is decreased due to reaction with PCE and the natural oxidant demand (NOD) related to the clayey till. A narrow but very efficient reaction zone is created in the clayey till. Initiallythe zone developed rapidlyfollowed by a slower expansion with time. PCE will counter diffuse into the reaction zone, where it will be degraded as long as MnO4- is present. A mass balance for the laboratory experiment revealed that the reaction between MnO4- and the clayey till was responsible for up to 90% of the total MnO4- consumption. Based on laboratory experiments, the high MnO4- consumption from reaction with clayey till appears to have been the limiting factor for the oxidation of PCE at the field site and is thus impairing the efficiency of ISCO as a remedy. PMID:18200874

Hønning, J; Broholm, M M; Bjerg, P L

2007-12-15

126

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...

127

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

PubMed Central

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

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

128

Adult neuropsychological performance following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water.  

PubMed

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

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

2012-01-01

129

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

PubMed Central

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

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

2012-01-01

130

A Historical and Technical Review and Analysis of TCE Contamination in the  

E-print Network

had entered the subsurface environment near the fire reservoir. Other TCE spills of unknown amounts Cornell University to provide "another set of eyes" to examine data related to the spill on behalf-level long-term toxic effects of TCE are not as well studied. Economic impacts of concern include house

131

Residual saturation, a source of long-term TCE contamination in the northeastern United States  

Microsoft Academic Search

Production wells at the US Army Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire are contaminated by trichloroethy lene (TCE). The concentrations in these production wells, which are pumping at a rate of 1 million gallons per day, have not decreased, despite CRREL's ceasing TCE use in 1987. The goal of this study is to identify the

JAN PRAVDA; KENNETH BELITZ

132

IN SITU CHEMICAL AND BIOLOGICAL TREATMENT OF TCE IN GROUNDWATER AT A LEGACY RAILROAD SITE  

E-print Network

IN SITU CHEMICAL AND BIOLOGICAL TREATMENT OF TCE IN GROUNDWATER AT A LEGACY RAILROAD SITE Vibhav Mankad, PE and Nathan Diem, CRA Lauren Mancuso, UPRR 2014 Railroad Environmental Conference Urbana · Railroad Legacy ­ acquisitions and mergers · Trichloroethene (TCE) used as degreaser in manufacturing

Illinois at Urbana-Champaign, University of

133

Microfabricated gas chromatograph for Sub-ppb determinations of TCE in vapor intrusion investigations  

Microsoft Academic Search

A microfabricated gas chromatograph (?GC) is described and its application to the analysis of sub-parts-per-billion (ppb) concentrations of trichloroethylene (TCE) in mixtures, relevant to the problem of TCE vapor intrusion (VI) into homes and offices, is demonstrated. The system employs a MEMS focuser, dual MEMS separation columns, and MEMS interconnects along with a microsensor array. These are interfaced to a

Hungwei Chang; Sun Kyu Kim; Thitiporn Sukaew; Forest Bohrer; Edward T. Zellers

2010-01-01

134

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...

135

Removal of gaseous trichloroethylene (TCE) in a composite membrane biofilm reactor.  

PubMed

A membrane biofilm reactor (MBfR) was investigated for the degradation of trichloroethylene (TCE) vapors inoculated by Burkholderia vietnamiensis G4. Toluene (TOL) was used as the primary substrate. The MBfR was loaded sequentially with TOL, TCE (or both) during 110 days. In this study, a maximum steady-state TCE removal efficiency of 23% and a maximum volumetric elimination capacity (EC) of 2.1 g m(-3) h(-1) was achieved. A surface area based maximum elimination capacity (EC(m)) of 4.2 × 10(-3) g m(-2) h(-1) was observed, which is 2-10 times higher than reported in other gas phase biological treatment studies. However, further research is needed to optimize the TCE feeding cycle and to evaluate the inhibiting effects of TCE and its intermediates on TOL biodegradation. PMID:22486674

Kumar, Amit; Vercruyssen, Aline; Dewulf, Jo; Lens, Piet; Van Langenhove, Herman

2012-01-01

136

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

USGS Publications Warehouse

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 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.

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

1998-01-01

137

Quantification of potassium permanganate consumption and PCE oxidation in subsurface materials  

NASA Astrophysics Data System (ADS)

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 to be met fully before PCE is oxidised.

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

2007-03-01

138

Experimental Results on the Destruction of PCE using a PhotoChemical Remediation Reactor  

Microsoft Academic Search

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

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

2001-01-01

139

Effectiveness of stimulating PCE reductive dechlorination: a step-wise approach.  

PubMed

Reductive dechlorination of tetrachloroethene (PCE) and its daughter products in aquifers is often hampered by Fe(III) reducing conditions. Rigorous treatment to adjust the redox potential and stimulate dechlorination may be costly and potentially have negative effects on other aquifer functions. A step-wise experimental strategy was applied to investigate the effectiveness of various adjustment scenarios. Batch experiments with ascorbic acid (AA) and sodium lactate (SL) showed that 75?mol electron equivalents per gram dry mass of aquifer material was required to reach a sufficiently low redox potential for the onset of PCE dechlorination. Similar effects of either AA or SL on the measured redox potential suggest electron donors are not specific. However, the relative rates of Fe(III) and sulphate reduction appeared to be specific to the electron donor applied. While redox potential stabilised around -450mV after titration and sulphate was reduced to zero in both treatments, in the AA treatment a faster production of Fe(2+) was observed with a final concentration of 0.46mM compared to only 0.07mM in the SL treatment. In subsequent batch experiments with aquifer material that was pre-treated with AA or SL, PCE reductive dechlorination occurred within 30days. Further stimulation tests with extra electron donor or inoculum revealed that adding electron donor can accelerate the initiation of PCE biodegradation. However, bioaugmentation with dechlorinating bacteria is required to achieve complete reductive dechlorination to ethene. The findings from step-wise approaches are relevant for improving the cost-effectiveness of the design and operation of in-situ bioremediation at initially unfavourable environmental conditions. PMID:24995946

Ni, Zhuobiao; Smit, Martijn; Grotenhuis, Tim; van Gaans, Pauline; Rijnaarts, Huub

2014-08-01

140

Effectiveness of stimulating PCE reductive dechlorination: A step-wise approach  

NASA Astrophysics Data System (ADS)

Reductive dechlorination of tetrachloroethene (PCE) and its daughter products in aquifers is often hampered by Fe(III) reducing conditions. Rigorous treatment to adjust the redox potential and stimulate dechlorination may be costly and potentially have negative effects on other aquifer functions. A step-wise experimental strategy was applied to investigate the effectiveness of various adjustment scenarios. Batch experiments with ascorbic acid (AA) and sodium lactate (SL) showed that 75 ?mol electron equivalents per gram dry mass of aquifer material was required to reach a sufficiently low redox potential for the onset of PCE dechlorination. Similar effects of either AA or SL on the measured redox potential suggest electron donors are not specific. However, the relative rates of Fe(III) and sulphate reduction appeared to be specific to the electron donor applied. While redox potential stabilised around - 450 mV after titration and sulphate was reduced to zero in both treatments, in the AA treatment a faster production of Fe2 + was observed with a final concentration of 0.46 mM compared to only 0.07 mM in the SL treatment. In subsequent batch experiments with aquifer material that was pre-treated with AA or SL, PCE reductive dechlorination occurred within 30 days. Further stimulation tests with extra electron donor or inoculum revealed that adding electron donor can accelerate the initiation of PCE biodegradation. However, bioaugmentation with dechlorinating bacteria is required to achieve complete reductive dechlorination to ethene. The findings from step-wise approaches are relevant for improving the cost-effectiveness of the design and operation of in-situ bioremediation at initially unfavourable environmental conditions.

Ni, Zhuobiao; Smit, Martijn; Grotenhuis, Tim; van Gaans, Pauline; Rijnaarts, Huub

2014-08-01

141

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

NASA Astrophysics Data System (ADS)

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.

Harkness, Mark; Fisher, Angela

2013-08-01

142

Factors Influencing TCE Anaerobic Dechlorination Investigated via Simulations of Microcosm Experiments  

NASA Astrophysics Data System (ADS)

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 is most pronounced in the dechlorination of TCE to DCE.

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

143

A risk-based cleanup criterion for PCE in soil. [Tetrachloroethylene  

SciTech Connect

The most important attribute of a chemical contaminant at a hazardous-wastes site for decision makers to consider with regard to its cleanup is the potential risk associated with human exposure. For this reason we have developed a strategy for establishing a risk-based cleanup criterion for chemicals in soil. We describe this strategy by presenting a cleanup criterion for tetrachloroethylene (PCE) in soil associated with a representative California landscape. We being by discussing the environmental fate and transport model, developed at the Lawrence Livermore National Laboratory (LLNL), that we used to predict the equilibrium concentration of PCE in five environmental media from a steady-state source in soil. Next, we explain the concept and application of pathway-exposure factors (PEFs), the hazard index, and cancer-potency factors (CPFs) for translating the predicted concentrations of PCE into estimated potential hazard or risk for hypothetically exposed individuals. Finally, the relationship between concentration and an allowable level of risk is defined and the societal and financial implications are discussed. 22 refs., 6 tabs.

Daniels, J.I.; McKone, T.E.; Hall, L.C.

1990-09-26

144

Cleanup of PCE-contaminated groundwater using an integrated pump-and-treat and vapor extraction system  

SciTech Connect

Contaminants can exist in saturated soil zones in three phases: (1) dissolved in soil-pore liquid, (2) adsorbed onto soil particles, and (3) occurring as free product. Pump-and-treat systems are designed to remove dissolved-phase and free-phase contaminants, but do not effectively remove sorbed contaminants and generally fail to remediate contaminated groundwater to drinking water standards. However, other remedial technologies that remove adsorbed or vapor-phase compounds can be combined with pump-and-treat technologies to enhance contaminant removal. A pump-and-treat groundwater remediation system was installed at a site in southern California contaminated with tetrachloroethene (PCE). The pump- and-treat system was selected to (1) remove dissolved-phase PCE, (2) contain the impacted groundwater plume, and (3) draw the water table down to expose impacted soil. The system was enhanced with a soil vapor extraction system to remove adsorbed PCE from the dewatered saturated zone and vapor-phase, dissolved-phase, and sorbed-phase PCE from the unsaturated zone. In less than 2 years, PCE concentrations in the groundwater were reduced from 1,100 {mu}g/l to less than the maximum contaminant level (5 {mu}g/l). The overseeing regulatory agency subsequently granted closure for this site, which was one of the first southern California sites with PCE-impacted groundwater to obtain closure.

Gwinn, J.P.; Read, M. [Orion Environmental Inc., Long Beach, CA (United States)

1997-12-31

145

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

146

Sorption model of trichloroethylene (TCE) and benezene in municipal landfill materials  

E-print Network

This research is intended to establish a mathematical model describing the mass transfer of trace gas in landfill. Experimental data used for calibration were reported by Stiegler et al. [ 1989]. Transfer mechanisms of TCE and benzene (trace gases...

Chuang, Yuh-Lin

1995-01-01

147

Trichloroethene (TCE) Degradation using Granular Activated Carbon and Zero Valent Iron Particles  

E-print Network

methods of TCE removal include Permeable Reactive Barriers (PRB), Bioremediation and Solvent Extraction, and Dionysios D. Dionysiou, Synthesis of Reactive Nano- Fe/Pd Bimetallic System-Impregnated Activated Carbon

Barthelat, Francois

148

In-situ bioremediation of TCE-contaminated groundwater  

SciTech Connect

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.

Travis, B.J. [Los Alamos National Lab., NM (United States); Rosenberg, N.D. [Lawrence Livermore National Lab., CA (United States)

1998-12-31

149

Effect of inorganic ions in heterogeneous photocatalysis of TCE  

SciTech Connect

The influence of 12 ionic compounds (Na{sub 2}SO{sub 4}, NaHCO{sub 3}, Na{sub 2}HPO{sub 4}, NaNO{sub 3}, NaCl, MnCl{sub 2}, NiCl{sub 2}, CaCl{sub 2}, MgCl{sub 2}, AlCl{sub 3}, FeCl{sub 3}, and MgSO{sub 4}) on performance of a fixed-bed photocatalytic reactor is examined. The fixed-bed photocatalyst was developed at Michigan Technological University and comprises 1% Pt-TiO{sub 2} on a silica-based support. The degradation of trichloroethylene (TCE) in Milli-Q water is used to monitor catalyst performance. All compounds are found to inhibit photocatalysis at some or all of the concentrations tested, although only MnCl{sub 2} seems to suppress it altogether. Fouling appears to be a least partially reversible. Electron microprobe analysis is employed to investigate how selected fouling agents interact with the catalyst and support.

Burns, R.A.; Crittenden, J.C.; Hand, D.W.; Selzer, V.H.; Sutter, L.L. [Michigan Technological Univ., Houghton, MI (United States). Dept. of Civil and Environmental Engineering] [Michigan Technological Univ., Houghton, MI (United States). Dept. of Civil and Environmental Engineering; Salman, S.R. [Yarmouk Univ., Irbid (Jordan). Dept. of Chemistry] [Yarmouk Univ., Irbid (Jordan). Dept. of Chemistry

1999-01-01

150

Biodegradation of aromatic compounds and TCE by a filamentous bacteria-dominated consortium  

Microsoft Academic Search

The Michaelis-Menten biodegradation kinetics (k and Ks) of aromatic compounds and trichloroethene (TCE) by an aerobic enrichment culture grown on phenol and dominated by a unique filamentous bacterium were measured. The average k and Ks values for phenol, benzene (B), toluene (T), ethylbenzene (E), o-xylene (oX), p-xylene (pX), naphthalene and TCE in g per g VSS-d and mg L-1 were

Angela R. Bielefeldt; H. David Stensel

1999-01-01

151

Influence of pH on persulfate oxidation of TCE at ambient temperatures.  

PubMed

In situ chemical oxidation (ISCO) is a technology used for groundwater remediation. This laboratory study investigated the use of the oxidant sodium persulfate for the chemical oxidation of trichloroethylene (TCE) at near ambient temperatures (10, 20 and 30 degrees C) to determine the influence of pH (pH=4, 7 and 9) on the reaction rate (i.e., pseudo-first-order rate constants) over the range of temperatures utilized. TCE solutions (60 mg l(-1); 0.46 mM) were prepared in phosphate buffered RO water and a fixed persulfate/TCE molar ratio of 50/1 was employed in all tests. Half-lives of TCE degradation at 10, 20 and 30 degrees C (pH 7) were 115.5, 35.0 and 5.5h, respectively. Maximum TCE degradation occurred at pH 7. Lowering system pH resulted in a greater decrease in TCE degradation rates than increasing system pH. Radical scavenging tests used to identify predominant radical species suggested that the sulfate radical (SO(4)(.-)) predominates under acidic conditions and the hydroxyl radical (.OH) predominates under basic conditions. In a side by side comparison of TCE degradation in a groundwater vs. unbuffered RO water it was demonstrated that when the system pH is buffered to near neutral pH conditions due to the presence of natural occurring groundwater constituents that the TCE degradation rate is higher than in unbuffered RO water where the system pH dropped from 5.9 to 2.8. The results of this study suggest that in a field application of ISCO, pH should be monitored and adjusted to near neutral if necessary. PMID:16814844

Liang, Chenju; Wang, Zih-Sin; Bruell, Clifford J

2007-01-01

152

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

NASA Astrophysics Data System (ADS)

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.

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

1995-03-01

153

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

154

Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination  

SciTech Connect

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.

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

2010-07-01

155

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

SciTech Connect

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.

Wise, D.P.

1997-12-01

156

In situ iron activated persulfate oxidative fluid sparging treatment of TCE contamination--a proof of concept study.  

PubMed

In situ chemical oxidation (ISCO) is considered a reliable technology to treat groundwater contaminated with high concentrations of organic contaminants. An ISCO oxidant, persulfate anion (S(2)O(8)(2-)) can be activated by ferrous ion (Fe(2+)) to generate sulfate radicals (E(o)=2.6 V), which are capable of destroying trichloroethylene (TCE). The property of polarity inhibits S(2)O(8)(2-) or sulfate radical (SO(4)(-)) from effectively oxidizing separate phase TCE, a dense non-aqueous phase liquid (DNAPL). Thus the oxidation primarily takes place in the aqueous phase where TCE is dissolved. A bench column study was conducted to demonstrate a conceptual remediation method by flushing either S(2)O(8)(2-) or Fe(2+) through a soil column, where the TCE DNAPL was present, and passing the dissolved mixture through either a Fe(2+) or S(2)O(8)(2-) fluid sparging curtain. Also, the effect of a solubility enhancing chemical, hydroxypropyl-beta-cyclodextrin (HPCD), was tested to evaluate its ability to increase the aqueous TCE concentration. Both flushing arrangements may result in similar TCE degradation efficiencies of 35% to 42% estimated by the ratio of TCE degraded/(TCE degraded+TCE remained in effluent) and degradation byproduct chloride generation rates of 4.9 to 7.6 mg Cl(-) per soil column pore volume. The addition of HPCD did greatly increase the aqueous TCE concentration. However, the TCE degradation efficiency decreased because the TCE degradation was a lower percentage of the relatively greater amount of dissolved TCE by HPCD. This conceptual treatment may serve as a reference for potential on-site application. PMID:18649972

Liang, Chenju; Lee, I-Ling

2008-09-10

157

Mammalian cytochrome CYP2E1 triggered differential gene regulation in response to trichloroethylene (TCE) in a transgenic poplar  

Microsoft Academic Search

Trichloroethylene (TCE) is an important environmental contaminant of soil, groundwater, and air. Studies of the metabolism\\u000a of TCE by poplar trees suggest that cytochrome P450 enzymes are involved. Using poplar genome microarrays, we report a number\\u000a of putative genes that are differentially expressed in response to TCE. In a previous study, transgenic hybrid poplar plants\\u000a expressing mammalian cytochrome P450 2E1

Jun Won Kang; Hui-Wen Wilkerson; Federico M. Farin; Theo K. Bammler; Richard P. Beyer; Stuart E. Strand; Sharon L. Doty

2010-01-01

158

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

SciTech Connect

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).

Eskenazi, B.; Fenster, L.; Hudes, M.; Wyrobek, A.J.; Katz, D.F.; Gerson, J.; Rempel, D.M. (Program of Maternal and Child Health, School of Public Health, University of California, Berkeley (United States))

1991-01-01

159

The Effect of FeS Mineral Transformation on TCE Degradation  

NASA Astrophysics Data System (ADS)

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 from mackinawite (FeS) to a mixture of mackinawite, greigite, pyrite, a transient phase lepidocrocite and goethite. This study show that freeze drying process could significantly change FeS mineralogy, and the mineralogy characteristics of FeS has important impact on its reactivity over TCE degradation. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

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

2009-12-01

160

TCE Transport to Woburn Wells G and H  

NSDL National Science Digital Library

To prepare to view the TCE animation, students could view the 'A Civil Action' movie and the instructor could read to them excerpts from the trial testimony and images from Woburn, wells G and H, geologic materials, geologic cross sections, the trial participants, and the federal courtroom in Boston (available as a attachment to this activity and at a website listed below). The discussion in Bair (2001) about scientists in the courtroom, the specific (excerpted) testimony presented by the three expert witnesses in the 'A Civil Action' trial, a chart summarizing the differences in their testimony, and the views of a federal judge on the goal of science versus the goal of a civil trial may also be worthwhile reading by the class prior to the assignment. The instructor could also show students the large plates included in the USGS report by Myette and others (1987) that display potentiometric data and contours before and after the famous aquifer test performed in December 1985 and January 1986, just before the trial, and discuss the ramifications of having only two sets of water-level measurements to characterize all the changes in the flow system between 1964 and 1979, when wells G and H periodically operated. This makes students consider the substantial differences in making predictions based on a steady-state conceptualization of the flow system or a transient conceptualization. The instructor could also show the animation of induced infiltration from the Aberjona River to wells G and H that also was created by Martin van Oort (M.S., 2005) and based on the research of Maura Metheny (M.S., 1998; Ph.D., 2004) at Ohio State University. Viewing both animations enables students to see that the water produced by wells G and H is a highly transient mixture derived from many different source areas within the valley. The article by Bair and Metheny (2002) concerning the remediation activities at the Wells G & H Superfund Site could be used to show how groundwater contamination is cleaned up, why different remediation schemes needed to be used in different hydrogeologic settings, and why cleanup to U.S. EPA standards can take decades.

Scott Bair

161

TCE degradation by toluene/benzene monooxygenase of Pseudomonas aeruginosa JI104 and Escherichia coli recombinant  

SciTech Connect

Pseudomonas aeruginosa JI104 incorporates more than three degradation pathways for aromatic compounds such as benzene, toluene, and xylene. A dioxygenase and two monooxygenases were cloned in Escherichia coli XL1-Blue. The dioxygenase yielding cis-toluene dihydrodiol and one of the monooxygenases producing o-cresol from toluene did not exhibit conspicuous activity in trichloroethylene (TCE) oxygenation, although DNA sequencing proved that the former enzyme was an isozyme of toluene dioxygenase of the known TCE decomposer P.putida F1. The other toluene/benzene monooxygenase that could generate o-, m-, and p-cresol simultaneously from toluene showed TCE oxygenation activity resulting in TCE decomposition in E. coli. The activity was inhibited competitively by toluene, ethylbenzene, and o- and m-xylene: their inhibition constants were greater than those of propylbenzene and p-xylene. When the E. coli recombinant harboring the monooxygenase was induced by isopropyl {beta}-D-thiogalactopyranoside (IPTG) and incubated in the absence of toluene, TCE degradation activity decreased during incubation, compared to that with toluene. Toluene probably controlled the lifetime of the enzyme.

Koizumi, Junichi [National Univ. of Yokohama (Japan). Div. of Bioengineering; Kitayama, Atsushi [Univ. of Tokyo (Japan). Dept. of Biochemistry and Biotechnology

1995-12-31

162

FY01 Phytoremediation of Chlorinated Ethenes in Southern Sector Seepline Sediments of SRS  

SciTech Connect

This treatability study is now in the second year of deployment for the Southern Sector Phytoremediation Project. Phytoremediation is the use of vegetation and associated media to treat contaminated soils, sediments, and groundwater. Phytoremediation is a rapidly developing technology that promises effective and safe cleanup of certain hazardous wastes. This ongoing work 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 and sediments uptake groundwater TCE and PCE, biodegrade it, and/or transform it. The experimental focus of this project is the biological removal of VOCs from seepline groundwater and sediments.

Brigmon, R.L.

2004-01-30

163

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

SciTech Connect

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.

Hoffman, F.

1995-04-01

164

Effects of Different Electron Donor Feeding Patterns on TCE Reductive Dechlorination Performance.  

PubMed

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

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

2015-03-01

165

Field study of TCE diffusion profiles below DNAPL to assess aquitard integrity.  

PubMed

An area where a free-product accumulation of trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) occurs at the bottom of a 10-m-thick surficial sand aquifer was studied to determine the integrity of the underlying, 20-m-thick, clayey silt aquitard formed of glaciolacustrine sediment. TCE concentration-versus-depth profiles determined from aquitard cores collected at five locations indicated penetration of detectable TCE 2.5 to 3.0 m into the aquitard. Two of the profiles show persistent DNAPL at the aquitard interface, while two others indicate that DNAPL, present initially, was completely dissolved away producing concentration declines at the aquitard interface. The fifth profile suggests shallow DNAPL penetration (<0.5 m) into the aquitard, however, this penetration, which was likely caused by cross-contamination during core collection or cone penetrometry (CPT) of the aquitard interface, did not increase the maximum depth of TCE penetration. Combining the field profiles with one-dimensional model simulations, downward migration of the aqueous TCE front, defined as the EPA MCL of 5 microg/l, which was below the analytical detection limit, was projected to a distance between 4 and 5 m below the top of the aquitard. Using a single set of estimated aquitard parameter values, simulations of aqueous TCE migration into the aquitard provided a good fit to four of the field profiles with a migration time of 35 to 45 years, consistent with the history of TCE use at the site. These simulations indicate aqueous TCE migration is diffusion-dominated with only small advective influence by the downward groundwater velocity of 2 to 3 cm/year or less in the aquitard due to pumping of the underlying aquifer to supply water to the facility in the past 50 years. The applicability of the parameter values was confirmed by in situ diffusion experiments of 1-year duration, in which stainless steel cylinders containing DNAPL were inserted into the aquitard. The diffusion-dominated nature of the profiles indicates that the aquitard provides long-term protection of the underlying aquifer from contamination from this DNAPL zone. Simulations of long-term migration of the TCE solute front indicate breakthrough to the lower aquifer at 1200 years for the no advection scenario and at 500 years if the strong downward hydraulic gradient persists. However, even after breakthrough, the mass flux through the aquitard to the underlying aquifer remains relatively low, and when considered in terms of potential impacts to pumping wells, concentrations are not expected to increase significantly above present-day MCLs. The use of contaminant profiles of different time and distance scales, in addition to hydraulic data, dramatically improves the ability to assess aquitard integrity, and provides improved transport parameter values for estimating contaminant arrival times and fluxes. The apparent lack of deep preferential pathways for TCE migration, such as open fractures, is probably due to the softness of the silty aquitard deposit and minimal physical or chemical weathering of the aquitard provides long-term protection of the underlying aquifer from contamination from this DNAPL zone. Simulations of long-term migration of the TCE solute front indicate breakthrough to the lower aquifer at 1200 years for the no advection scenario and at 500 years if the strong downward hydraulic gradient persists. However, even after the breakthrough, the mass flux through the aquitard to the underlying aquifer remains relatively low, and when considered in terms of potential impacts to pumping wells , concentrations are not expected to increase significantly above present-day MCLs. The use of contaminant profiles of different time and distance scales, in addition to hydraulic data, dramatically improves the ability to assess aquitard integrity, and provides improved transport parameter values for estimating contaminant arrival times and fluxes. The apparent lack of deep preferential pathways for TCE migration, such as open fractures, is probably due to the softness

Parker, Beth L; Cherry, John A; Chapman, Steven W

2004-10-01

166

Dual augmentation for aerobic bioremediation of MTBE and TCE pollution in heavy metal-contaminated soil.  

PubMed

In this work we isolated from soil and characterized several bacterial strains capable of either resisting high concentrations of heavy metals (Cd(2+) or Hg(2+) or Pb(2+)) or degrading the common soil and groundwater pollutants MTBE (methyl-tert-butyl ether) or TCE (trichloroethylene). We then used soil microcosms exposed to MTBE (50 mg/l) or TCE (50 mg/l) in the presence of one heavy metal (Cd 10 ppm or Hg 5 ppm or Pb 50 or 100 ppm) and two bacterial isolates at a time, a degrader plus a metal-resistant strain. Some of these two-membered consortia showed degradation efficiencies well higher (49-182% higher) than those expected under the conditions employed, demonstrating the occurrence of a synergetic relationship between the strains used. Our results show the efficacy of the dual augmentation strategy for MTBE and TCE bioremediation in the presence of heavy metals. PMID:18987783

Fernandes, V C; Albergaria, J T; Oliva-Teles, T; Delerue-Matos, C; De Marco, P

2009-06-01

167

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

NASA Astrophysics Data System (ADS)

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.

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

2006-06-01

168

Applications of ultrasound in NAPL remediation: sonochemical degradation of TCE in aqueous surfactant solutions.  

PubMed

Surfactant-enhanced pump-and-treat technologies increase the efficiency of nonaqueous-phase liquids (NAPLs) removal from soils. However, high concentrations of surfactants in groundwater impose severe limitations to water treatment. In this paper, we explore the applicability of ultrasonic irradiation as an alternative method for surfactant recovery and contaminant degradation. The combined effects of temperature, initial substrate concentration, and concentration of added surfactant (sodium dodecyl sulfate, SDS) were analyzed for the sonolysis of trichloroethylene (TCE) in batch experiments at an ultrasonic frequency of 500 kHz and 77 W/L applied power density. In the range of 5-30 degrees C, TCE sonolysis becomes faster at higher temperatures, both in the absence and in the presence of surfactant. This indicates that gas-phase pyrolysis prevails over other chemical reactions in the liquid phase. Inhibition of TCE sonolysis was observed in the presence of surfactant at all SDS concentrations. Changes in the initial TCE concentration (from 250 microM to 1.2 mM) showed no effect on the degradation rates in the presence of SDS. For surfactant levels below its critical micelle concentration (cmc), the inhibition of TCE sonolysis exhibited a highly nonlinear dependence with increasing SDS concentration. A correlation was observed in this range between the relative inhibition of sonolysis and the decreasing surface tension of the solutions. Above the cmc up to an SDS concentration of 5%, the reaction rate decreased less markedly. Micellar sequestration of the contaminant seems to be the main reason for this additional inhibition. Bubble growth prior to collapse may incorporate some of the TCE dissolved in the micelles through their adsorption in the expanding bubble walls, thus partially overcoming the scavenging effect due to micellar entrapment of the contaminant. PMID:11478257

Destaillats, H; Alderson, T W; Hoffmann, M R

2001-07-15

169

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

SciTech Connect

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.

Not Available

1993-02-12

170

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

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

171

Multiplexed Selective Detection and Identification of TCE and Xylene in Water by On-Chip Absorption Spectroscopy  

E-print Network

Multiplexed Selective Detection and Identification of TCE and Xylene in Water by On-Chip Absorption spectroscopy. The signature of Trichloroethylene(TCE) and xylene in water enable multiplexed detection on one Volatile Organic Compounds (VOCs) in liquid and gaseous phases to detect xylene in water and methane

Chen, Ray

172

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 ...

173

The Bin3 RNA methyltransferase (MePCE) targets 7SK RNA to control transcription and translation  

PubMed Central

Bin3 is a conserved RNA methyltransferase found in eukaryotes ranging from fission yeast to humans. It was originally discovered as a Bicoid-interacting protein in Drosophila, where it is required for anterior-posterior and dorso-ventral axis determination in the early embryo. The mammalian ortholog of Bin3 (BCDIN3), also known as methyl phosphate capping enzyme (MePCE), plays a key role in repressing transcription. In transcription, MePCE binds the non-coding 7SK RNA, which forms a scaffold for an RNA-protein complex that inhibits P-TEFb, an RNA polymerase II elongation factor. MePCE uses S-adenosyl methionine to transfer a methyl group onto the ?-phosphate of the 5? guanosine of 7SK RNA generating an unusual cap structure that protects 7SK RNA from degradation. Bin3/MePCE also has a role in translation regulation. Initial studies in Drosophila indicate that Bin3 targets 7SK RNA and stabilizes a distinct RNA-protein complex that assembles on the 3? UTR of caudal mRNAs to prevent translation initiation. Much remains to be learned about Bin3/MeCPE function, including how it recognizes 7SK RNA, what other RNA substrates it might target, and how widespread a role it plays in gene regulation and embryonic development. PMID:22740346

Cosgrove, Michael; Ding, Ye; Rennie, William A.; Lane, Michael J.; Hanes, Steven D.

2013-01-01

174

Preliminary technology report for Southern Sector bioremediation  

SciTech Connect

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.

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

1997-06-01

175

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

PubMed

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

Lewis, Jeffrey; Qvarfort, Ulf; Sjöström, Jan

2015-01-01

176

Formulation design for target delivery of iron nanoparticles to TCE zones  

NASA Astrophysics Data System (ADS)

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.

Wang, Ziheng; Acosta, Edgar

2013-12-01

177

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

NASA Astrophysics Data System (ADS)

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.

Park, J.; Yoo, K.

2013-12-01

178

Superfund Record of Decision (EPA Region 4): Davis Park Road TCE, Gastonia, NC, September 29, 1998  

SciTech Connect

This decision document presents the selected remedial action for the Davis Park Road TCE Site in Gastonia, Gaston County, North Carolina. This remedy addressees the principle threat posed by the Site. The major threat is the contaminated groundwater emanating from beneath the Site.

NONE

1998-10-01

179

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...

180

Treatment of co-mingled benzene, toluene and TCE in groundwater.  

PubMed

This work addressed a hypothetical but practical scenario that includes biological oxidation and reductive dechlorination in treating groundwater containing co-mingled plume of trichloroethene (TCE), benzene and toluene. Groundwater immediately downgradient from the commonly used zero-valent iron (ZVI) has shown alkaline pH (up to 10.7). The elevated pH may influence BTEX compounds (i.e., benzene, toluene, ethyl benzene, and xylenes) biodegradation, which could also be inhibited by elevated concentrations of TCE. Data from this work suggests that the inhibition coefficients (IC) value for 100 ?g/L and 500 ?g/L of TCE on benzene and toluene degradation are 2.1-2.8 at pH 7.9, and 3.5-6.1 at pH 10.5. For a co-mingled plume, it appears to be more effective to reduce TCE by ZVI before addressing benzene and toluene biodegradation. The ample buffering capacity of most groundwater and the adaptation of benzene and toluene-degrading microbes are likely able to eliminate the adverse influence of pH shifts downgradient from a ZVI-PRB. PMID:24857895

Chen, Liang; Liu, Yulong; Liu, Fei; Jin, Song

2014-06-30

181

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 ...

182

Monitoring Performance of a Dual Wall Permeable Reactive Barrier for Treating Perchlorate and TCE  

Microsoft Academic Search

AMEC Geomatrix, through collaboration with Aerojet General Corporation and the University of California, Davis (UCD), has performed work leading to the installation of a dual wall permeable reactive barrier (PRB) system capable of treating perchlorate and chlorinated aliphatic hydrocarbon compounds (CAHs), including trichloroethylene (TCE), at Aerojet's Area 40 site in Sacramento, California. This unique system consisted of an upgradient zero-valent

C. E. Dowman; Y. Hashimoto; S. Warner; P. Bennett; D. Gandhi; F. Szerdy; S. Neville; C. Fennessy; K. M. Scow

2008-01-01

183

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...

184

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...

185

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...

186

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...

187

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

PubMed

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 ?(13) C and ?(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 ?(13) C and ?(37) Cl, respectively. The dual isotope approach represented by a plot of ?(13) C vs. ?(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 biodegradation in the complex fractured rock aquifer. It is highly recommended to revisit the study when the municipal well is back into full operation. PMID:22220911

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

2012-01-01

188

Episodic emissions data summary. Final report, March-June 1987  

SciTech Connect

The report presents a complete summary of episodic emissions data collected by the Environmental Protection Agency (EPA) under the authority of Section 114 of the Clean Air Act (CAA). Episodic emissions data were collected for the production and use of nine potentially hazardous organic compounds: methylene chloride (MC), carbon tetrachloride (CT), chloroform (CF), perchloroethylene (PCE), trichloroethylene (TCE), ethylene dichloride (EDC), butadiene (BD), ethylene oxide (EO), and epichlorohydrin (EPI). These chemicals and data are reported in 13 source categories that best describe the scope of use of these chemicals.

Howle, R.H.; Nash, R.A.

1987-06-01

189

Change of pH and Iron Ion Concentration During Photodegradation of TCE with Ferrioxalate/UVvis Process  

SciTech Connect

Recently, some studies show various organic compounds such as pesticides and dyes degraded with the irradiation of ultraviolet light and visible light in the presence of oxalic acid and ferric ion (ferrioxalate/UVvis process). The process has much advance than other technologies because it can utilize the wavelength of 300{approx}450nm and also under the condition of neutral pH. Chlorinated organic compounds such as trichloroethene (TCE), which have caused ground water pollution on a lot of sites, have never been applied by photodegradation with this process. In this study, we showed the degradation of TCE in the presence of oxalic acid and iron ion and the change of pH, ferric and ferrous ion concentration during the photodegradation of TCE with ferrioxalate/UV-vis process. TCE was degraded in the presence of oxalic acid and iron ion. In the reactions, the equilibrium of oxalate ion and iron ion is important since it determines the amount of ferrioxalate complex which absorbs light and induces the reactions of the degradation of TCE. Thus, the pH value and iron ion concentration are the important factors which determine the amount of ferrioxalate complex. The pH is nearly constant during the photodegradation of TCE. The ferrous ion concentration was decreased as soon as beginning photodegradation of TCE, and then the ferrous ion concentration and ferric ion concentration became constant.

Hareyama, Wataru; Suto, Koichi; Inoue, Chihiro; Chida, Tadashi [Graduate School of Environmental Studies, Tohoku University, Sendai (Japan); Nakazawa, Hiroshi [Graduate School of Engineering, Iwate University, Morioka (Japan)

2006-05-15

190

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

NASA Technical Reports Server (NTRS)

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.

Downie, John D.

1992-01-01

191

RNA elements directing in vivo assembly of the 7SK/MePCE/Larp7 transcriptional regulatory snRNP  

PubMed Central

Through controlling the nuclear level of active positive transcription elongation factor b (P-TEFb), the 7SK small nuclear RNA (snRNA) functions as a key regulator of RNA polymerase II transcription. Together with hexamethylene bisacetamide-inducible proteins 1/2 (HEXIM1/2), the 7SK snRNA sequesters P-TEFb into transcriptionally inactive ribonucleoprotein (RNP). In response to transcriptional stimulation, the 7SK/HEXIM/P-TEFb RNP releases P-TEFb to promote polymerase II-mediated messenger RNA synthesis. Besides transiently associating with HEXIM1/2 and P-TEFb, the 7SK snRNA stably interacts with the La-related protein 7 (Larp7) and the methylphosphate capping enzyme (MePCE). In this study, we used in vivo RNA–protein interaction assays to determine the sequence and structural elements of human 7SK snRNA directing assembly of the 7SK/MePCE/Larp7 core snRNP. MePCE interacts with the short 5?-terminal G1-U4/U106-G111 helix-tail motif and Larp7 binds to the 3?-terminal hairpin and the following U-rich tail of 7SK. The overall RNA structure and some particular nucleotides provide the information for specific binding of MePCE and Larp7. We also demonstrate that binding of Larp7 to 7SK is a prerequisite for in vivo recruitment of P-TEFb, indicating that besides providing stability for 7SK, Larp7 directly participates in P-TEFb regulation. Our results provide further explanation for the frequently observed link between Larp7 mutations and cancer development. PMID:23471002

Muniz, Lisa; Egloff, Sylvain; Kiss, Tamás

2013-01-01

192

Remediation of PCE-contaminated aquifer by an in situ two-layer biobarrier: laboratory batch and column studies  

Microsoft Academic Search

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop an in situ two-layer biobarrier system consisting of an organic-releasing material layer followed by an oxygen-releasing material layer. The organic-releasing material, which contained sludge cakes from a domestic wastewater treatment plant, is able to release biodegradable

C. M Kao; S. C Chen; J. Y Wang; Y. L Chen; S. Z Lee

2003-01-01

193

Retaining and recovering enzyme activity during degradation of TCE by methanotrophs  

SciTech Connect

To determine if compounds added during trichloroethylene (TCE) degradation could reduce the loss of enzyme activity or increase enzyme recovery, different compounds serving as energy and carbon sources, pH buffers, or free radical scavengers were tested. Formate and formic acid (reducing power and a carbon source), as well as ascorbic acid and citric acid (free radical scavengers) were added during TCE degradation at a concentration of 2 mM. A saturated solution of calcium carbonate was also tested to address pH concerns. In the presence of formate and methane, only calcium carbonate and formic acid had a beneficial effect on enzyme recovery. The calcium carbonate and formic acid both reduced the loss of enzyme activity and resulted in the highest levels of enzyme activity after recovery. 19 refs., 3 figs.

Palumbo, A.V.; Strong-Gunderson, J.M.; Carroll, S. [Oak Ridge National Lab., TN (United States)

1997-12-31

194

In Situ Redox Manipulation of Subsurface Sediments from Fort Lewis, Washington: Iron Reduction and TCE Dechlorination Mechanisms  

SciTech Connect

The feasibility of chemically treating sediments from the Ft. Lewis, Washington, Logistics Center to develop a permeable barrier for dechlorination of TCE was investigated in a series of laboratory experiments.

Szecsody, James E.; Fruchter, Jonathan S.; Sklarew, Deborah S.; Evans, John C.

2000-03-17

195

Influence of pH on persulfate oxidation of TCE at ambient temperatures  

Microsoft Academic Search

In situ chemical oxidation (ISCO) is a technology used for groundwater remediation. This laboratory study investigated the use of the oxidant sodium persulfate for the chemical oxidation of trichloroethylene (TCE) at near ambient temperatures (10, 20 and 30°C) to determine the influence of pH (pH=4, 7 and 9) on the reaction rate (i.e., pseudo-first-order rate constants) over the range of

Chenju Liang; Zih-Sin Wang; Clifford J. Bruell

2007-01-01

196

Electrochemically induced dual reactive barriers for transformation of TCE and mixture of contaminants in groundwater  

PubMed Central

A novel reactive electrochemical flow system consisting of iron anode and porous cathode is proposed for the remediation of mixture of contaminants in groundwater. The system consists of a series of sequentially arranged electrodes, a perforated iron anode, a porous copper cathode followed by a mesh-type mixed metal oxide anode. The iron anode generates ferrous species and a chemically reducing environment, the porous cathode provides a reactive electrochemically reducing barrier, and the inert anode provides proton and oxygen to neutralize the system. The redox conditions of the electrolyte flowing through this system can be regulated by controlling the distribution of the electric current. Column experiments are conducted to evaluate the process and study the variables. The electrochemical reduction on a copper foam cathode produced an electrode-based reductive potential capable of reducing TCE and nitrate. Rational electrodes arrangement, longer residence time of electrolytes and higher surface area of foam electrode improve the reductive transformation of TCE. More than 82.2% TCE removal efficiency is achieved for the case of low influent concentration (< 7.5 mg/L) and high current (> 45 mA). The ferrous species produced from the iron anode not only enhance the transformation of TCE on the cathode, but also facilitates transformation of other contaminants including dichromate, selenate and arsenite. Removal efficiencies greater than 80% are achieved for these contaminants from flowing contaminated water. The overall system, comprising the electrode-based and electrolyte-based barriers, can be engineered as a versatile and integrated remedial method for a relatively wide spectrum of contaminants and their mixtures. PMID:23067023

Mao, Xuhui; Yuan, Songhu; Fallahpour, Noushin; Ciblak, Ali; Howard, Joniqua; Padilla, Ingrid; Loch-Caruso, Rita; Alshawabkeh, Akram N.

2012-01-01

197

Factors Influencing TCE Anaerobic Dechlorination Investigated via Simulations of Microcosm Experiments  

Microsoft Academic Search

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

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

2006-01-01

198

Characterization and Performance of Granular Iron as Reactive Media for TCE degradation by Permeable Reactive Barriers  

Microsoft Academic Search

The application of Permeable Reactive Barriers (PRBs), an innovative clean-up technology for in-situ groundwater remediation, represents an effective alternative to traditional pump-and-treat systems and has raised strong interest during recent years. From recent statistics of the Italian Water Research Institute (IRSA), trichloroethylene (TCE) from industrial activities is the most widespread contaminant in groundwater. The goal of the research was to

Renato Baciocchi; Maria Rosaria Boni; Laura D'Aprile

2003-01-01

199

In Situ Chemical Reduction of Aquifer Sediments: Enhancement of Reactive Iron Phases and TCE Dechlorination  

Microsoft Academic Search

In situ chemical reduction of aquifer sediments is currently being used for chromate and TCE remediation by forming a permeable reactive barrier. The chemical and physical processes that occur during abiotic reduction of natural sediments by sodium dithionite were investigated. In different aquifer sediments, 15 to 25% of Fe{sup III} -oxides were dissolved\\/reduced, which produces primarily adsorbed Fe{sup II}, and

Jim E. Szecsody; Jonathan S. Fruchter; Mark D. Williams; Vince R. Vermeul; Debbie S. Sklarew

2004-01-01

200

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

SciTech Connect

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 reconciles the disparity between those previously published PBPK models that concluded low perc metabolism in humans and those that predicted high perc metabolism in humans. In essence, both conclusions are consistent with the data if augmented with some additional qualifications: in humans, oxidative metabolism is low, while GSH conjugation metabolism may be high or low, with uncertainty and/or interindividual variability spanning three orders of magnitude. More direct data on the internal kinetics of perc GSH conjugation, such as trichlorovinyl glutathione or tricholorvinyl cysteine in blood and/or tissues, would be needed to better characterize the uncertainty and variability in GSH conjugation in humans. - Research Highlights: >We analyze perchloroethylene (perc) toxicokinetics with a physiological model. >Results from previous analyses lumping metabolic pathways are inconsistent. >Separately tracking oxidation and conjugation pathways reconciles these results. >Available data are adequate for predicting perc blood levels and oxidation by P450. >High uncertainty remains for human conjugation of perc with glutathione.

Chiu, Weihsueh A., E-mail: chiu.weihsueh@epa.gov [National Center for Environmental Assessment, U.S. Environmental Protection Agency, Washington, DC 20460 (United States); Ginsberg, Gary L., E-mail: gary.ginsberg@ct.gov [Connecticut Department of Public Health, Hartford, CT 06106 (United States)

2011-06-15

201

Long Term Remote Monitoring of TCE Contaminated Groundwater at Savannah River Site  

SciTech Connect

The purpose of this study was to develop a mobile self powered remote monitoring system enhanced for field deployment at Savannah River Site (SRS). The system used a localized power source with solar recharging and has wireless data collection, analysis, transmission, and data management capabilities. The prototype was equipped with a Hydrolab's DataSonde 4a multi-sensor array package managed by a Supervisory Control and Data Acquisition (SCADA) system, with an adequate pumping capacity of water samples for sampling and analysis of Trichloroethylene (TCE) in contaminated groundwater wells at SRS. This paper focuses on a study and technology development efforts conducted at the Hemispheric Center for Environmental Technology (HCET) at Florida International University (FIU) to automate the sampling of contaminated wells with a multi-sensor array package developed using COTS (Commercial Off The shelf) parts. Bladder pumps will pump water from different wells to the sensors array, water quality TCE indicator parameters are measured (i.e. pH, redox, ORP, DO, NO3 -, Cl-). In order to increase user access and data management, the system was designed to be accessible over the Internet. Remote users can take sample readings and collect data remotely over a web. Results obtained at Florida International University in-house testing and at a field deployment at the Savannah River Site indicate that this long term monitoring technique can be a feasible solution for the sampling of TCE indicator parameters at remote contaminated sites.

Duran, C.; Gudavalli, R.; Lagos, L.; Tansel, B.; Varona, J.; Allen, M.

2004-10-06

202

Electrolytic Manipulation of Persulfate Reactivity by Iron Electrodes for TCE Degradation in Groundwater  

PubMed Central

Activated persulfate oxidation is an effective in situ chemical oxidation process for groundwater remediation. However, reactivity of persulfate is difficult to manipulate or control in the subsurface causing activation before reaching the contaminated zone and leading to a loss of chemicals. Furthermore, mobilization of heavy metals by the process is a potential risk. An effective approach using iron electrodes is thus developed to manipulate the reactivity of persulfate in situ for trichloroethylene (TCE) degradation in groundwater, and to limit heavy metals mobilization. TCE degradation is quantitatively accelerated or inhibited by adjusting the current applied to the iron electrode, following k1 = 0.00053•Iv + 0.059 (?122 A/m3 ? Iv ? 244 A/m3) where k1 and Iv are the pseudo first-order rate constant (min?1) and volume normalized current (A/m3), respectively. Persulfate is mainly decomposed by Fe2+ produced from the electrochemical and chemical corrosion of iron followed by the regeneration via Fe3+ reduction on the cathode. SO4•? and •OH co-contribute to TCE degradation, but •OH contribution is more significant. Groundwater pH and oxidation-reduction potential can be restored to natural levels by the continuation of electrolysis after the disappearance of contaminants and persulfate, thus decreasing adverse impacts such as the mobility of heavy metals in the subsurface. PMID:24328192

Yuan, Songhu; Liao, Peng; Alshawabkeh, Akram N.

2014-01-01

203

The transfer of trichloroethylene (TCE) from a shower to indoor air: Experimental measurements and their implications  

SciTech Connect

Experiments were performed to measure the transfer of trichloroethylene (TCE), a volatile organic compound (VOC), from tap water to showers to indoor air. In these experiments, the loss of TCE from tap water in the shower is based on the difference between influent and effluent concentrations. We have developed and previously published a three-compartment model, which we use to simulate the 24-h concentration history of VOCs in the shower, bathroom, and remaining household volumes resulting from the use of contaminated tap water. An important input to this model is the transfer efficiency of the VOC from water to air. The experiments reveal that the transfer efficiency of TCE from shower water to air has an arithmetic mean value of 61 percent and an arithmetic standard deviation of 9 percent. Analysis of the results shows that there is no statistically significant difference between the transfer efficiency measured with hot (37C) or cold (22C) shower water and that there is no statistically significant change in transfer efficiency with time during a 20-min shower. The implications for exposure assessment are considered.

McKone, T.E.; Knezovich, J.P. (Univ. of California, Livermore (United States))

1991-05-01

204

The transfer of trichloroethylene (TCE) from a shower to indoor air: Experimental measurements and their implications  

SciTech Connect

Experiments were performed to measure the transfer of trichloroethylene (TCE), a volatile organic compound (VOC), from tap water in showers to indoor air. In these experiments, the loss of TCE from tap water in the shower is based on the difference between influent and effluent concentrations.We have developed and previously published a three-compartment model, which we use to simulate the 24-h concentration history of VOCs in the shower, bathroom, and remaining household volumes resulting from the use of contaminated tap water. An important input to this model is the transfer efficiency of the VOC from water to air. The experiments reveal that the transfer efficiency of TCE from shower water to air has an arithmetic mean value of 51 percent and an arithmetic standard deviation of 9 percent. Analysis of the results shows that there is no statistically significant difference between the transfer efficiency measured with hot (37C) or cold (22C) shower water and that there is no statistically significant change in transfer efficiency with time during a 20-min shower. The implications for exposure assessment are considered.

McKone, T.E.; Knezovich, J.P. (Univ. of California, Livermore (United States))

1991-08-01

205

The role of microbial reductive dechlorination of TCE at a phytoremediation site  

USGS Publications Warehouse

In April 1996, a phytoremediation field demonstration site at the Naval Air Station, Fort Worth, Texas, was developed to remediate shallow oxic ground water (< 3.7 m deep) contaminated with chlorinated ethenes. Microbial populations were sampled in February and June 1998. The populations under the newly planted cottonwood trees had not yet matured to an anaerobic community that could dechlorinate trichloroethene (TCE) to cis-1,2-dichloroethene (DCE); however, the microbial population under a mature (???22-year-old) cottonwood tree about 30 m southwest of the plantings had a mature anaerobic population capable of dechlorinating TCE to DCE, and DCE to vinyl chloride (VC). Oxygen-free sediment incubations with contaminated groundwater also demonstrated that resident microorganisms were capable of the dechlorination of TCE to DCE. This suggests that a sufficient amount of organic material is present for microbial dechlorination in aquifer microniches where dissolved O2 concentrations are low. Phenol, benzoic acid, acetic acid, and a cyclic hydrocarbon, compounds consistent with the degradation of root exudates and complex aromatic compounds, were identified by gas chromatography/mass spectrometry (GC/MS) in sediment samples under the mature cottonwood tree. Elsewhere at the site, transpiration and degradation by the cottonwood trees appears to be responsible for loss of chlorinated ethenes.

Godsy, E.M.; Warren, E.; Paganelli, V.V.

2003-01-01

206

In situ detection of organic molecules: Optrodes for TCE (trichloroethylene) and CHCl sub 3  

SciTech Connect

We have developed new absorption-based chemical indicators for detecting chloroform (CHCl{sub 3}) and trichloroethylene (TCE). These indicators were used to make very sensitive optical chemical sensors (optrodes) for each of these two contaminants. Concentrations below 10 ppb can be accurately measured using these sensors. Furthermore, they are selective and do not response to similar contaminants commonly found with TCE and CHCl{sub 3} in contaminated groundwater. In addition, the sensor response is linearly proportional to the chemical concentration. In this report, we describe the details of this optrode and the putative reaction sequences of the indicator chemistries with CHCl{sub 3} and TCE and present an analysis of the spectral data obtained from the reaction products. A key part of the development of this optrode was designing a simple readout device. The readout is a dual-channel fiber-optic fluorimeter modified to measure transmission or absorption of light. The system is controlled by a lap-top microcomputer and is fully field portable. In addition to describing the final absorption optrode, details of the chemical indicator reactions are presented for both absorption- (colorimetric) and fluorescence-based optrodes. Finally, we report on the syntheses of several compounds used to evaluate the indicator chemical reactions that led to the development of the absorption optrode. 23 refs., 26 figs., 1 tab.

Angel, S. M.; Langry, K. C.; Ridley, M. N.

1990-05-01

207

Implementing heterogeneous catalytic dechlorination technology for remediating TCE-contaminated groundwater.  

PubMed

To transition catalytic reductive dechlorination (CRD) into practice, it is necessary to demonstrate the effectiveness, robustness, and economic competitiveness of CRD-based treatment systems. A CRD system scaled up from previous laboratory studies was tested for remediating groundwater contaminated with 500-1200 microg L(-1) trichloroethylene (TCE) at Edwards Air Force Base (AFB), California. Groundwater was pumped from a treatment well at 2 gal min(-1), amended with hydrogen to 0.35 mg L(-1) and contacted for 2.3 min with 20 kg eggshell-coated Pd on alumina beads (2% Pd by wt) packed in a fixed-bed reactor, and then returned to the aquifer. Operation was continuous for 23 h followed a 1 h regeneration cycle. After regeneration, TCE removal was 99.8% for 4 to 9 h and then declined to 98.3% due to catalyst deactivation. The observed catalyst deactivation was tentatively attributed to formation of sulfidic compounds; modeling of catalyst deactivation kinetics suggests the presence of sulfidic species equivalent to 2-4 mg L(-1) hydrogen sulfide in the reactor water. Over the more than 100 day demonstration period, TCE concentrations in the treated groundwater were reduced by >99% to an average concentration of 4.1 microg L(-1). The results demonstrate CRD as a viable treatment alternative technically and economically competitive with activated carbon adsorption and other conventional physicochemical treatmenttechnologies. PMID:19192817

Davie, Matthew G; Cheng, Hefa; Hopkins, Gary D; Lebron, Carmen A; Reinhard, Martin

2008-12-01

208

Characterization of four TCE-dechlorinating microbial enrichments grown with different cobalamin stress and methanogenic conditions.  

PubMed

To investigate the important supportive microorganisms responsible for trichloroethene (TCE) bioremediation under specific environmental conditions and their relationship with Dehalococcoides (Dhc), four stable and robust enrichment cultures were generated using contaminated groundwater. Enrichments were maintained under four different conditions exploring two parameters: high and low TCE amendments (resulting in inhibited and uninhibited methanogenic activity, respectively) and with and without vitamin B?? amendment. Lactate was supplied as the electron donor. All enrichments were capable of reductively dechlorinating TCE to vinyl chloride and ethene. The dechlorination rate and ethene generation were higher, and the proportion of electrons used for dechlorination increased when methanogenesis was inhibited. Biologically significant cobalamin biosynthesis was detected in the enrichments without B?? amendment. Comparative genomics using a genus-wide microarray revealed a Dhc genome similar to that of strain 195 in all enrichments, a strain that lacks the major upstream corrin ring biosynthesis pathway. Seven other bacterial operational taxonomic units (OTUs) were detected using clone libraries. OTUs closest to Pelosinus, Dendrosporobacter, and Sporotalea (PDS) were most dominant. The Clostridium-like OTU was most affected by B?? amendment and active methanogenesis. Principal component analysis revealed that active methanogenesis, rather than vitamin B?? limitation, exerted a greater effect on the community structures even though methanogens did not seem to play an essential role in providing corrinoids to Dhc. In contrast, acetogenic bacteria that were abundant in the enrichments, such as PDS and Clostridium sp., may be potential corrinoid providers for Dhc. PMID:23640361

Men, Yujie; Lee, Patrick K H; Harding, Katie C; Alvarez-Cohen, Lisa

2013-07-01

209

Intercalation of TCE by Sediment-Associated Clay Minerals and Implications for Low-Concentration Elution Tailing and Back Diffusion  

NASA Astrophysics Data System (ADS)

Pump-and-treat systems are widely used to remediate hazardous waste sites wherein groundwater is contaminated by compounds such as TCE (trichloroethene). It is well known that removal of contaminant mass by pump and treat becomes less effective over time, with a persistent mass discharge causing greatly extended operational periods. One mechanism potentially responsible for this persistent mass discharge is "back diffusion", wherein dissolved contaminant stored in lower-permeability layers diffuses into the higher-permeability zones that are more readily swept via pump and treat. Because the lower-permeability layers typically contain high fractions of clay minerals, a question of great interest is whether contaminant-clay interactions may influence the back-diffusion process. For example, intercalation of TCE into the interlayer spaces of clay minerals could potentially exacerbate diffusive mass-transfer limitations. The primary objectives of this research were to evaluate the long-term elution of TCE from aquifer sediments, and to examine the potential for TCE intercalation. Sediment samples were collected from a TCE-contaminated field site in Tucson, AZ. A widely used Na- Montmorillonite specimen clay was used as a control. Miscible-displacement experiments were conducted to characterize TCE elution behavior. X-ray diffraction, conducted with a controlled environment chamber, was used to characterize smectite interlayer d-spacing for three treatments (bulk dry sample, sample mixed with synthetic groundwater, sample mixed with TCE-saturated synthetic groundwater). Extensive elution tailing was observed for the column experiments. Results of the XRD analysis indicate a greater d-spacing for the samples treated with TCE-saturated synthetic groundwater for all field samples as well as the specimen clay.

Matthieu, D. E.; Brusseau, M. L.; Bowden, M. E.; Johnson, G. R.; Artiola, J. F.; Curry, J. E.

2011-12-01

210

Electro-enhanced Permeable Reactive Barrier : Optimal Design of PRB System With External Current for Effective TCE Removal From Groundwater  

Microsoft Academic Search

The objective of this study was to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC). A series of column experiments were conducted to evaluate the location of Fe0 permeable reactive barrier (PRB) and the effects of electrode arrangement in the column on the TCE

J. Moon; H. Moon; Y. Roh; H. Kim; Y. Song

2002-01-01

211

Electrocatalytic activity of Pd-loaded Ti/TiO2 nanotubes cathode for TCE reduction in groundwater.  

PubMed

A novel cathode, Pd loaded Ti/TiO2 nanotubes (Pd-Ti/TiO2NTs), is synthesized for the electrocatalytic reduction of trichloroethylene (TCE) in groundwater. Pd nanoparticles are successfully loaded on TiO2 nanotubes which grow on Ti plate via anodization. Using Pd-Ti/TiO2NTs as the cathode in an undivided electrolytic cell, TCE is efficiently and quantitatively transformed to ethane. Under conditions of 100 mA and pH 7, the removal efficiency of TCE (21 mg/L) is up to 91% within 120 min, following pseudo-first-order kinetics with the rate constant of 0.019 min(-1). Reduction rates increase from 0.007 to 0.019 min(-1) with increasing the current from 20 to 100 mA, slightly decrease in the presence of 10 mM chloride or bicarbonate, and decline with increasing the concentrations of sulfite or sulfide. O2 generated at the anode slightly influences TCE reduction. At low currents, TCE is mainly reduced by direct electron transfer on the Pd-Ti/TiO2NT cathode. However, the contribution of Pd-catalytic hydrodechlorination, an indirect reduction mechanism, becomes significant with increasing the current. Compared with other common cathodes, i.e., Ti-based mixed metal oxides, graphite and Pd/Ti, Pd-Ti/TiO2NTs cathode shows superior performance for TCE reduction. PMID:23726693

Xie, Wenjing; Yuan, Songhu; Mao, Xuhui; Hu, Wei; Liao, Peng; Tong, Man; Alshawabkeh, Akram N

2013-07-01

212

A PCE groundwater plume discharging to a river: influence of the streambed and near-river zone on contaminant distributions.  

PubMed

An investigation of a tetrachloroethene (PCE) groundwater plume originating at a dry cleaning facility on a sand aquifer and discharging to a river showed that the near-river zone strongly modified the distribution, concentration, and composition of the plume prior to discharging into the surface water. The plume, streambed concentration, and hydrogeology were extensively characterized using the Waterloo profiler, mini-profiler, conventional and driveable multilevel samplers (MLS), Ground Penetrating Radar (GPR) surveys, streambed temperature mapping (to identify discharge zones), drivepoint piezometers, and soil coring and testing. The plume observed in the shallow streambed deposits was significantly different from what would have been predicted based on the characteristics of the upgradient plume. Spatial and temporal variations in the plume entering the near-river zone contributed to the complex contaminant distribution observed in the streambed where concentrations varied by factors of 100 to 5000 over lateral distances of less than 1 to 3.5 m. Low hydraulic conductivity semi-confining deposits and geological heterogeneities at depth below the streambed controlled the pattern of groundwater discharge through the streambed and influenced where the plume discharged into the river (even causing the plume to spread out over the full width of the streambed at some locations). The most important effect of the near-river zone on the plume was the extensive anaerobic biodegradation that occurred in the top 2.5 m of the streambed, even though essentially no biodegradation of the PCE plume was observed in the upgradient aquifer. Approximately 54% of the area of the plume in the streambed consisted solely of PCE transformation products, primarily cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC). High concentrations in the interstitial water of the streambed did not correspond to high groundwater-discharge zones, but instead occurred in low discharge zones and are likely sorbed or retarded remnants of past high-concentration plume discharges. The high-concentration areas (up to 5529 microg/l of total volatile organics) in the streambed are of ecological concern and represent potential adverse exposure locations for benthic and hyporheic zone aquatic life, but the effect of these exposures on the overall health of the river has yet to be determined. Even if the upgradient source of PCE is remediated and additional PCE is prevented from reaching the streambed, the high-concentration deposits in the streambed will likely take decades to hundreds of years to flush completely clean under natural conditions because these areas have low vertical groundwater flow velocities and high retardation factors. Despite high concentrations of contaminants in the streambed, PCE was detected in the surface water only rarely due to rapid dilution in the river and no cDCE or VC was detected. Neither the sampling of surface water nor the sampling of the groundwater from the aquifer immediately adjacent to the river gave an accurate indication of the high concentrations of PCE biodegradation products present in the streambed. Sampling of the interstitial water of the shallow streambed deposits is necessary to accurately characterize the nature of plumes discharging to rivers. PMID:15336797

Conant, Brewster; Cherry, John A; Gillham, Robert W

2004-09-01

213

Analysis of TCE Fate and Transport in Karst Groundwater Systems Using Statistical Mixed Models  

NASA Astrophysics Data System (ADS)

Karst groundwater systems are highly productive and provide an important fresh water resource for human development and ecological integrity. Their high productivity is often associated with conduit flow and high matrix permeability. The same characteristics that make these aquifers productive also make them highly vulnerable to contamination and a likely for contaminant exposure. Of particular interest are trichloroethylene, (TCE) and Di-(2-Ethylhexyl) phthalate (DEHP). These chemicals have been identified as potential precursors of pre-term birth, a leading cause of neonatal complications with a significant health and societal cost. Both of these contaminants have been found in the karst groundwater formations in this area of the island. The general objectives of this work are to: (1) develop fundamental knowledge and determine the processes controlling the release, mobility, persistence, and possible pathways of contaminants in karst groundwater systems, and (2) characterize transport processes in conduit and diffusion-dominated flow under base flow and storm flow conditions. The work presented herein focuses on the use of geo-hydro statistical tools to characterize flow and transport processes under different flow regimes, and their application in the analysis of fate and transport of TCE. Multidimensional, laboratory-scale Geo-Hydrobed models (GHM) were used for this purpose. The models consist of stainless-steel tanks containing karstified limestone blocks collected from the karst aquifer formation of northern Puerto Rico. The models integrates a network of sampling wells to monitor flow, pressure, and solute concentrations temporally and spatially. Experimental work entails injecting dissolved CaCl2 tracers and TCE in the upstream boundary of the GHM while monitoring TCE and tracer concentrations spatially and temporally in the limestone under different groundwater flow regimes. Analysis of the temporal and spatial concentration distributions of solutes indicates a highly heterogeneous system resulting in large preferential flow components. The distributions are highly correlated with statistically-developed spatial flow models. High degree of tailing in breakthrough curves indicate significant amount of mass limitations, particularly in diffuse flow regions. Higher flow rates in the system result in increasing preferential flow region volumes, but lower mass transfer limitations. Future work will involve experiments with non-aqueous phase liquid TCE, DEHP, and a mixture of these, and geo-temporal statistical modeling. This work is supported by the U.S. Department of Energy, Savannah River (Grant Award No. DE-FG09-07SR22571), and the National Institute of Environmental Health Sciences (NIEHS, Grant Award No. P42ES017198).

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

2012-12-01

214

Public health assessment for Newton County Wells (a/k/a Silver Creek TCE), Joplin, Jasper County, Missouri, Region 7: CERCLIS number MOD985798339. Final report  

SciTech Connect

The Newton County TCE site contains an uncontrolled groundwater plume of trichloroethylene (TCE) contamination. The source of contamination is believed to be FAG Bearings. From 1973 to 1982, FAG Bearings produced ball bearings using TCE as a commercial degreaser. It is alleged that improper disposal and leaks of an alleged closed system of TCE led to the contamination of soil at the industrial site, the groundwater aquifer, and subsequently, 82 private water wells. Exposure pathways at the site consist of inhalation of, ingestion of, and dermal contact with TCE-contaminated groundwater and surface water. Because completed and potential exposure pathways exist, the Newton County TCE site has been classified as a Public Health Hazard.

NONE

1999-07-19

215

Use of statistical tools to evaluate the reductive dechlorination of high levels of TCE in microcosm studies  

NASA Astrophysics Data System (ADS)

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 was designed as a fractional factorial experiment involving 177 bottles distributed between four industrial laboratories and was used to assess the impact of six electron donors, bioaugmentation, addition of supplemental nutrients, and two TCE levels (0.57 and 1.90 mM or 75 and 250 mg/L in the aqueous phase) on TCE dechlorination. Performance was assessed based on the concentration changes of TCE and reductive dechlorination degradation products. The chemical data was evaluated using analysis of variance (ANOVA) and survival analysis techniques to determine both main effects and important interactions for all the experimental variables during the 203-day study. The statistically based design and analysis provided powerful tools that aided decision-making for field application of this technology. The analysis showed that emulsified vegetable oil (EVO), lactate, and methanol were the most effective electron donors, promoting rapid and complete dechlorination of TCE to ethene. Bioaugmentation and nutrient addition also had a statistically significant positive impact on TCE dechlorination. In addition, the microbial community was measured using phospholipid fatty acid analysis (PLFA) for quantification of total biomass and characterization of the community structure and quantitative polymerase chain reaction (qPCR) for enumeration of Dehalococcoides organisms (Dhc) and the vinyl chloride reductase (vcrA) gene. The highest increase in levels of total biomass and Dhc was observed in the EVO microcosms, which correlated well with the dechlorination results.

Harkness, Mark; Fisher, Angela; Lee, Michael D.; Mack, E. Erin; Payne, Jo Ann; Dworatzek, Sandra; Roberts, Jeff; Acheson, Carolyn; Herrmann, Ronald; Possolo, Antonio

2012-04-01

216

Risk of learning and behavioral disorders following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water.  

PubMed

This population-based retrospective cohort study examined the association between developmental disorders of learning, attention and behavior and prenatal and early postnatal drinking water exposure to tetrachloroethylene (PCE) on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Mothers completed a questionnaire on disorders of attention, learning and behavior in their children and on potential confounding variables. The final cohort consisted of 2086 children. Results of crude and multivariate analyses showed no association between prenatal exposure and receiving tutoring for reading or math, being placed on an Individual Education Plan, or repeating a school grade (adjusted Odds Ratios (OR)=1.0-1.2). There was also no consistent pattern of increased risk for receiving a diagnosis of Attention Deficit Disorder (ADD) or Hyperactive Disorder (HD), special class placement for academic or behavioral problems, or lower educational attainment. Modest associations were observed for the latter outcomes only in the low exposure group (e.g., adjusted ORs for ADD were 1.4 and 1.0 for low and high exposure, respectively). (All ORs are based on an unexposed referent group.) Results for postnatal exposure through age five years were similar to those for prenatal exposure. We conclude that prenatal and early postnatal PCE exposure is not associated with disorders of attention, learning and behavior identified on the basis of questionnaire responses and at the exposure levels experienced by this population. PMID:18353612

Janulewicz, Patricia A; White, Roberta F; Winter, Michael R; Weinberg, Janice M; Gallagher, Lisa E; Vieira, Veronica; Webster, Thomas F; Aschengrau, Ann

2008-01-01

217

Risk of Learning and Behavioral Disorders Following Prenatal and Early Postnatal Exposure to Tetrachloroethylene (PCE)-contaminated Drinking Water  

PubMed Central

This population-based retrospective cohort study examined the association between developmental disorders of learning, attention and behavior and prenatal and early postnatal drinking water exposure to tetrachloroethylene (PCE) on Cape Cod, Massachusetts. Subjects were identified through birth records from 1969 through 1983. Exposure was modeled using information from town water departments, a PCE leaching and transport algorithm, EPANet water flow modeling software, and a Geographic Information System (GIS). Mothers completed a questionnaire on disorders of attention, learning and behavior in their children and on potential confounding variables. The final cohort consisted of 2,086 children. Results of crude and multivariate analyses showed no association between prenatal exposure and receiving tutoring for reading or math, being placed on an Individual Education Plan, or repeating a school grade (adjusted Odds Ratios (OR)=1.0–1.2). There was also no consistent pattern of increased risk for receiving a diagnosis of Attention Deficit Disorder (ADD) or Hyperactive Disorder (HD), special class placement for academic or behavioral problems, or lower educational attainment. Modest associations were observed for the latter outcomes only in the low exposure group (e.g., adjusted ORs for ADD were 1.4 and 1.0 for low and high exposure, respectively). (All ORs are based on an unexposed referent group.) Results for postnatal exposure through age five years were similar to those for prenatal exposure. We conclude that prenatal and early postnatal PCE exposure is not associated with disorders of attention, learning and behavior identified on the basis of questionnaire responses and at the exposure levels experienced by this population. PMID:18353612

Janulewicz, Patricia A; White, Roberta F; Winter, Michael R; Weinberg, Janice M; Gallagher, Lisa E; Vieira, Veronica; Webster, Thomas F; Aschengrau, Ann

2008-01-01

218

Preliminary study of propyl bromide exposure among New Jersey dry cleaners as a result of a pending ban on perchloroethylene.  

PubMed

Many states are considering, and some states have actively pursued, banning the use of perchloroethylene (PERC) in dry cleaning establishments. Proposed legislation has led many dry cleaners to consider the use of products that contain greater than 90% n-propyl bromide (n-PB; also called 1-bromopropane or 1-BP). Very little information is known about toxicity and exposure to n-PB. Some n-PB-containing products are marketed as nonhazardous and "green" or "organic." This has resulted in some users perceiving the solvent as nontoxic and has resulted in at least one significant poisoning incident in New Jersey. In addition, many dry cleaning operators may not realize that the machine components and settings must be changed when converting from PERC to n-PB containing products. Not performing these modifications may result in overheating and significant leaks in the dry cleaning equipment. A preliminary investigation was conducted of the potential exposures to n-PB and isopropyl bromide (iso-PB; also called 2-bromopropane or 2-BP) among dry cleaners in New Jersey who have converted their machines from PERC to these new solvent products. Personal breathing zone and area samples were collected using the National Institute for Occupational Safety and Health Sampling and Analytical Method 1025, with a slight modification to gas chromatography conditions to facilitate better separation of n-PB from iso-PB. During the preliminary investigation, exposures to n-PB among some workers in two of three shops were measured that were greater than the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for n-PB. The highest exposure measured among a dry cleaning machine operator was 54 parts per million (ppm) as an 8-hr time-weighted average, which is more than 5 times the ACGIH TLV of 10 ppm. The preliminary investigation also found that the work tasks most likely to result in the highest short-term exposures included the introduction of solvent to the machine, maintenance of the machine, unloading and handling of recently cleaned clothes, and interrupting the wash cycle of the machine. In addition, this assessment suggested that leaks may have contributed to exposure and may have resulted from normal machine wear over time, ineffective maintenance, and from the incompatibility of n-PB with gasket materials. PMID:20863050

Blando, James D; Schill, Donald P; De La Cruz, Mary Pauline; Zhang, Lin; Zhang, Junfeng

2010-09-01

219

Simulating the fate and transport of TCE from groundwater to indoor air.  

PubMed

This work provides an exploratory analysis on the relative importance of various factors controlling the fate and transport of volatile organic contaminants (in this case, TCE) from a DNAPL source zone located below the water table and into the indoor air. The analysis is conducted using the multi-phase compositional model CompFlow Bio, with the base scenario problem geometry reminiscent of a field experiment conducted by Rivett [Rivett, M.O., (1995), Soil-gas signatures from volatile chlorinated solvents: Borden field experiments. Groundwater, 33(1), 84-98.] at the Borden aquifer where groundwater was observed to transport a contaminant plume a substantial distance without vertical mass transport of the contaminant across the capillary fringe and into the vadose zone. Results for the base scenario model indicate that the structure of the permeability field was largely responsible for deflecting the groundwater plume upward towards the capillary fringe, permitting aqueous phase diffusion to transport the TCE into the vadose zone. Alternative permeability realizations, generated as part of a Monte Carlo simulation process, at times deflected the groundwater plume downwards causing the extended thickness of the saturated zone to insulate the vadose zone from exposure to the TCE by upward diffusive transport. Comparison of attenuation coefficients calculated using the CompFlow Bio and Johnson and Ettinger [Johnson, P.C. and Ettinger, R.A., (1991), Heuristic model for predicting the intrusion rate of contaminant vapors into buildings. Environmental Science and Technology, 25, 1445-1452.] heuristic model exhibited fortuitous agreement for the base scenario problem geometry, with this agreement diverging for the alternative permeability realizations as well as when parameters such as the foundation slab fracture aperture, the indoor air pressure drop, the capillary fringe thickness, and the infiltration rate were varied over typical ranges. PMID:19525028

Yu, Soonyoung; Unger, Andre J A; Parker, Beth

2009-07-21

220

Simulating the fate and transport of TCE from groundwater to indoor air  

NASA Astrophysics Data System (ADS)

This work provides an exploratory analysis on the relative importance of various factors controlling the fate and transport of volatile organic contaminants (in this case, TCE) from a DNAPL source zone located below the water table and into the indoor air. The analysis is conducted using the multi-phase compositional model CompFlow Bio, with the base scenario problem geometry reminiscent of a field experiment conducted by Rivett [Rivett, M.O., (1995), Soil-gas signatures from volatile chlorinated solvents: Borden field experiments. Groundwater, 33(1), 84-98.] at the Borden aquifer where groundwater was observed to transport a contaminant plume a substantial distance without vertical mass transport of the contaminant across the capillary fringe and into the vadose zone. Results for the base scenario model indicate that the structure of the permeability field was largely responsible for deflecting the groundwater plume upward towards the capillary fringe, permitting aqueous phase diffusion to transport the TCE into the vadose zone. Alternative permeability realizations, generated as part of a Monte Carlo simulation process, at times deflected the groundwater plume downwards causing the extended thickness of the saturated zone to insulate the vadose zone from exposure to the TCE by upward diffusive transport. Comparison of attenuation coefficients calculated using the CompFlow Bio and Johnson and Ettinger [Johnson, P.C. and Ettinger, R.A., (1991), Heuristic model for predicting the intrusion rate of contaminant vapors into buildings. Environmental Science and Technology, 25, 1445-1452.] heuristic model exhibited fortuitous agreement for the base scenario problem geometry, with this agreement diverging for the alternative permeability realizations as well as when parameters such as the foundation slab fracture aperture, the indoor air pressure drop, the capillary fringe thickness, and the infiltration rate were varied over typical ranges.

Yu, Soonyoung; Unger, Andre J. A.; Parker, Beth

2009-07-01

221

The influence of different geotechnically relevant amendments on the reductive degradation of TCE by nZVI  

NASA Astrophysics Data System (ADS)

Trichloroethylene (TCE) was widely used as a cleaning and degreasing agent. Companies needing these agents were often situated in or close to built up areas, so spillage led to contaminated sites which now can only be remediated using in situ techniques. The situation is compounded by the fact that TCE tends to seep through ground water bodies forming pools at the bottom of the aquifer. When reacting with TCE, nanoscale zero valent iron (nZVI) is known to reduce it into non-toxic substances. The difficulty is to bring it in contact with the pollutant. Attempts using passive insertion into the groundwater via wells yielded mixed results. Reasons for this are that ZVI tends to coagulate, to sediment and to adsorb on the matrix of the aquifer. Also, in inhomogeneous aquifers a passive application of nZVI can be difficult and might not bring the desired results, due to existence of preferential flow paths. A possible solution to this problem is the physical in situ mixing of ZVI into the contaminant source. This can, in principle, be done by adapting jet grouting - a method that uses a high pressure slurry jet, consisting of water and geotechnical additives ("binders"), to mix and compact zones ("columns") in soil. These columns are commonly used to solve foundation problems but can also be used to solve the problem of delivering nZVI to TCE source zones. This paper examines the influence binders have on the degradation reaction between TCE and nZVI. The necessity of these binders is explained by the fact that the subsoil structure is rearranged during the jetting process leading to subsidence on the surface. These subsidences could result in damage to neighbouring structures. A series of batch experiments was conducted in this study. Contaminated groundwater was brought into contact with samples of slurries commonly used in geotechnical applications. We tested the effects of concresole, bentonite, zeolithe, fly ash, slag sand and cement on the kinetics of TCE degradation by nZVI. The degradation of TCE was measured using GC Headspace samples. Furthermore, additional experiments were conducted to investigate the interaction between binders and TCE as well as binders and nZVI. The results of these experiments led to the conclusion that jet grouting could be well suited for the delivery of nZVI to TCE contaminated source zones. Currently, soil column experiments and large-scale experiments in test facilities are performed to confirm the batch testing results.

Freitag, Peter; Schöftner, Philipp; Waldner, Georg; Reichenauer, Thomas G.; Nickel, Claudia; Spitz, Marcus; Dietzel, Martin

2014-05-01

222

Anaerobic biotransformation of chlorinated aliphatic hydrocarbons: Ugly duckling to beautiful swan  

SciTech Connect

For many years anaerobic biological processes were reputed to be more sensitive than aerobic processes to toxic substances such as chlorinated aliphatic hydrocarbons (CAH) and thus a poor choice for treating water containing these compounds. This was especially true for water containing perchloroethylene (PCE) or trichloroethylene (TCE) because vinyl chloride, a human carcinogen, is produced when these two compounds are degraded anaerobically. Aerobic treatment with organisms containing oxygenase enzyme systems, which could fortuitously degrade a wide variety of chlorinated aliphatics (but not PCE), was favored. Recently, however, several enrichments and organisms have been isolated that will convert PCE and TCE into ethene and ethane, as shown by field data. Because of this evidence, anaerobic processes are now considered a significant alternative treatment for CAH contamination. Recent work at the University of Iowa, Iowa City, has focused on the effect of mixtures of CAHs on biotransformation of individual organic compounds and the potential for a combined methanogen-iron (Fe(0)) system to improve CAH bioremediation. At the concentration ranges tested, the presence of a mixture of CAHs seems to decrease rate of transformation of individual organics. However, there are important exceptions; in some cases a mixture of CAHs seems to facilitate transformation of an individual organic compound. Combination of an active methanogenic population with Fe(0) increases the rate and extent of transformation of carbon tetrachloride and chloroform. Results with PCE and 1,1,1-trichloroethane are less clear.

Parkin, G.F.

1999-10-01

223

Both PCE-1/RX and OTX/CRX interactions are necessary for photoreceptor-specific gene expression.  

PubMed

RX, a homeodomain-containing protein essential for proper eye development (Mathers, P. H. Grinberg, A., Mahon, K. A., and Jamrich, M. (1997) Nature 387, 603-607), binds to the photoreceptor conserved element-1 (PCE-1/Ret 1) in the photoreceptor cell-specific arrestin promoter and stimulates gene expression. RX is found in many retinal cell types including photoreceptor cells. Another homeodomain-containing protein, CRX, which binds to the OTX element to stimulate promoter activity, is found exclusively in photoreceptor cells (Chen, S., Wang, Q. L., Nie, Z., Sun, H., Lennon, G., Copeland, N. G., Gillbert, D. J. Jenkins, N. A., and Zack, D. J. (1997) Neuron 19, 1017-1030; Furukawa, T., Morrow, E. M., and Cepko, C. L. (1997) Cell 91, 531-541). Binding assay and cell culture studies indicate that both PCE-1 and OTX elements and at least two different regulatory factors RX and CRX are necessary for high level, photoreceptor cell-restricted gene expression. Thus, photoreceptor specificity can be achieved by multiple promoter elements interacting with a combination of both photoreceptor-specific regulatory factors and factors present in closely related cell lineages. PMID:10625658

Kimura, A; Singh, D; Wawrousek, E F; Kikuchi, M; Nakamura, M; Shinohara, T

2000-01-14

224

Pilot testing of deep air sparging for remediation of TCE contaminated groundwater  

SciTech Connect

Air sparging has become a popular and successful method for remediating groundwater contaminated with various volatile and/or biodegradable contaminants. However, evaluation of air sparging has often been limited to shallow groundwater contamination, typically 25 feet or less below the groundwater table. The pilot test program described in this paper was developed to expand the application of air sparging to deeper contamination. In the case of the site that will be discussed, TCE contamination has been encountered at approximately 50 feet below groundwater, which is just above a clay confining layer. Since TCE can be very amenable to remediation by air sparging, the primary difficulty in the technology in this application is the challenges associated with implementation of a sparging system at this depth. The air sparging pilot test program developed for the site includes nested sparge wells, nested groundwater monitoring wells, a horizontal vapor extraction system, and soil gas monitoring points. The pilot system design also includes timer and pressure regulating controls to enable evaluation of multiple operating scenarios. These scenarios include testing of deep injection only, as well as multi-level air injection and various pulsing schemes between all of the injection wells. This variety of operational capabilities enables a thorough evaluation of the pilot system success and development of design parameters necessary to support full scale system design.

Swingle, T.P.; Goldsmith, P.M. [Parsons Engineering Science, Inc., Winter Park, FL (United States); Schulman, S. [CES/CEVR, Patrick AFB, FL (United States)

1996-12-31

225

In Situ Chemical Reduction of Aquifer Sediments: Enhancement of Reactive Iron Phases and TCE Dechlorination  

SciTech Connect

In situ chemical reduction of aquifer sediments is currently being used for chromate and TCE remediation by forming a permeable reactive barrier. The chemical and physical processes that occur during abiotic reduction of natural sediments by sodium dithionite were investigated. In different aquifer sediments, 15 to 25% of Fe{sup III} -oxides were dissolved/reduced, which produces primarily adsorbed Fe{sup II}, and some siderite. The sediment reduction rate ({approx} 5h) was the chemically controlled (58 kJ/mole) reduction of a minor phase (<20%). It was necessary to maintain neutral to high pH to maintain reduction efficiency and prevent iron mobilization, as reduction generated H{sup +}. Sequential extractions on reduced sediment showed that adsorbed ferrous iron and iron oxides on the clay size fraction controlled TCE reactivity, and not structural ferrous iron in clay. The mass and rate of field-scale reduction of aquifer sediments were generally predicted with laboratory data using a single reduction reaction.

Szecsody, Jim E.; Fruchter, Jonathan S.; Williams, Mark D.; Vermeul, Vince R.; Sklarew, Debbie S.

2004-07-29

226

In situ chemical reduction of aquifer sediments: enhancement of reactive iron phases and TCE dechlorination.  

PubMed

In situ chemical reduction of aquifer sediments is currently being used for chromate and TCE remediation by forming a permeable reactive barrier. The chemical and physical processes that occur during abiotic reduction of natural sediments during flow by sodium dithionite were investigated. In different aquifer sediments, 10-22% of amorphous and crystalline FeIII-oxides were dissolved/reduced, which produced primarily adsorbed FeII, and some siderite. Sediment oxidation showed predominantly one FeII phase, with a second phase being oxidized more slowly. The sediment reduction rate (3.3 h batch half-life) was chemically controlled (58 kJ mol(-1)), with some additional diffusion control during reduction in sediment columns (8.0 h half-life). It was necessary to maintain neutral to high pH to maintain reduction efficiency and prevent iron mobilization, as reduction generated H+. Sequential extractions on reduced sediment showed that adsorbed ferrous iron controlled TCE reactivity. The mass and rate of field-scale reduction of aquifer sediments were generally predicted with laboratory data using a single reduction reaction. PMID:15461176

Szecsody, Jim E; Fruchter, Jonathan S; Williams, Mark D; Vermeul, Vince R; Sklarew, Debbie

2004-09-01

227

Use of gene probes to assess the impact and effectiveness of aerobic in situ bioremediation of TCE  

SciTech Connect

Gene probe hybridization was used to determine distribution and expression of co-metabolic genes at a contaminated site as it underwent in situ methanotrophic bioremediation of trichloroethylene (TCE). The bioremediation strategies tested included a series of air, air:methane, and air:methane:nutrient pulses of the test plot using horizontal injection wells. During the test period, the levels of TCE reduced drastically in almost all test samples. Sediment core samples (n = 367) taken from 0 m (surface)-43 m depth were probed for gene coding for methanotrophic soluble methane monooxygenase (sMMO) and heterotrophic toluene dioxygenase (TOD), which are known to co-metabolize TCE. The same sediment samples were also probed for genes coding for methanol dehydrogenase (MDH) (catalyzing the oxidation of methanol to formaldehyde) to assess specifically changes in methylotrophic bacterial populations in the site. Gene hybridization results showed that the frequency of detection of sMMO genes were stimulated approximately 250% following 1% methane:air (v/v) injection. Subsequent injection of 4% methane:air (v/v) resulted in an 85% decline probably due to nutrient limitations, since addition of nutrients (gaseous nitrogen and phosphorus) thereafter caused an increase in the frequency of detection of sMMO genes. Detection of TOD genes declined during the process, and eventually they were non-detectable by the final treatment, suggesting that methanotrophs displaced the TOD gene containing heterotrophs. Active transcription of sMMO and TOD was evidenced by hybridization to mRNA. These analyses combined with results showing the concomitant decline in TCE concentrations, increases in chloride concentration and increases in methanotroph viable counts, provide multiple lines of evidence that TCE remediation was caused specifically by methanotrophs. Our results suggest that sMMO genes are responsible for most, if not all, of the observed biodegradation of TCE. This study demonstrates that the use of nucleic acid analytical methods provided a gene specific assessment of the effects of in situ treatment technologies.

Hazen, Terry C.; Chakraborty, Romy; Fleming, James M.; Gregory, Ingrid R.; Bowman, John P.; Jimenez, Luis; Zhang, Dai; Pfiffner, Susan M.; Brockman, Fred J.; Sayler, Gary S.

2009-03-15

228

Using slow-release permanganate candles to remove TCE from a low permeable aquifer at a former landfill.  

PubMed

Past disposal of industrial solvents into unregulated landfills is a significant source of groundwater contamination. In 2009, we began investigating a former unregulated landfill with known trichloroethene (TCE) contamination. Our objective was to pinpoint the location of the plume and treat the TCE using in situ chemical oxidation (ISCO). We accomplished this by using electrical resistivity imaging (ERI) to survey the landfill and map the subsurface lithology. We then used the ERI survey maps to guide direct push groundwater sampling. A TCE plume (100-600 ?g L(-1)) was identified in a low permeable silty-clay aquifer (K(h)=0.5 md(-1)) that was within 6m of ground surface. To treat the TCE, we manufactured slow-release potassium permanganate candles (SRPCs) that were 91.4 cm long and either 5. cm or 7.6 cm in dia. For comparison, we inserted equal masses of SRPCs (7.6-cm versus 5.1-cm dia) into the low permeable aquifer in staggered rows that intersected the TCE plume. The 5.1-cm dia candles were inserted using direct push rods while the 7.6-cm SRPCs were placed in 10 permanent wells. Pneumatic circulators that emitted small air bubbles were placed below the 7.6-cm SRPCs in the second year. Results 15 months after installation showed significant TCE reductions in the 7.6-cm candle treatment zone (67-85%) and between 10% and 66% decrease in wells impacted by the direct push candles. These results support using slow-release permanganate candles as a means of treating chlorinated solvents in low permeable aquifers. PMID:22784864

Christenson, Mark D; Kambhu, Ann; Comfort, Steve D

2012-10-01

229

Use of gene probes to assess the impact and effectiveness of aerobic In situ bioremediation of TCE.  

SciTech Connect

Gene probe hybridization was used to determine distribution and expression of co-metabolic genes at a contaminated site as it underwent in situ methanotrophic bioremediation of trichloroethylene (TCE). The bioremediation strategies tested consisted of a series of air, air:methane, and air:methane:nutrient pulses using a horizontal injection well. Sediment core samples (n=367) taken from 0 (surface)-43m depth were probed for genes coding for soluble methane monooxygenase (sMMO) and toluene dioxygenase (TOD), which are known to cometabolize TCE. The same samples were also probed for genes coding for methanol dehydrogenase (MDH) to access changes in methylotrophic bacterial populations. Hybridization results showed that the frequency of detection of sMMO genes were stimulated approximately 250% following 1% methane:air (v/v) injection. Subsequent 4% methane:air (v/v) injection resulted in an 85% decline probably due to nutrient limitations, since subsequent addition of nutrients (gaseous nitrogen and phosphorus) caused an increase in the frequency of detection of sMMO genes. Detection of TOD genes declined during the process becoming non-detectable by the final treatment. These patterns indicate methanotrophs displaced heterotrophs containing TOD genes. Active transcription of sMMO and TOD was evidenced by hybridization to mRNA. These analyses combined with studies showing the concomitant decline in TCE concentrations, increases in methanotroph viable counts, increased mineralization rates of TCE, and increases in chloride inventories provide multiple lines of evidence that TCE remediation was caused specifically by methanotrophs. This work suggests that sMMO genes are responsible for most, if not all, of the biodegradation of TCE observed. This study demonstrated that the use of nucleic acid analytical methods provided a gene specific assessment of the effects of in situ treatment technologies.

Hazen, Terry C.; Chakraborty, Romy; Fleming, James M.; Gregory, Ingrid R.; Bowman, John P.; Jimenez, Luis; Zhang, Dai; Pfiffner, Susan M.; Brockman, Fred J.; Sayler, Gary S.

2009-03-01

230

Development of KMnO(4)-releasing composites for in situ chemical oxidation of TCE-contaminated groundwater.  

PubMed

The objective of this study was to develop a controlled-oxidant-release technology combining in situ chemical oxidation (ISCO) and permeable reactive barrier (PRB) concepts to remediate trichloroethene (TCE)-contaminated groundwater. In this study, a potassium permanganate (KMnO4)-releasing composite (PRC) was designed for KMnO4 release. The components of this PRC included polycaprolactone (PCL), KMnO4, and starch with a weight ratio of 1.14:2:0.96. Approximately 64% (w/w) of the KMnO4 was released from the PRC after 76 days of operation in a batch system. The results indicate that the released KMnO4 could oxidize TCE effectively. The results from a column study show that the KMnO4 released from 200 g of PRC could effectively remediate 101 pore volumes (PV) of TCE-contaminated groundwater (initial TCE concentration = 0.5 mg/L) and achieve up to 95% TCE removal. The effectiveness of the PRC system was verified by the following characteristics of the effluents collected after the PRC columns (barrier): (1) decreased TCE concentrations, (2) increased ORP and pH values, and (3) increased MnO2 and KMnO4 concentrations. The results of environmental scanning electron microscope (ESEM) analysis show that the PCL and starch completely filled up the pore spaces of the PRC, creating a composite with low porosity. Secondary micro-scale capillary permeability causes the KMnO4 release, mainly through a reaction-diffusion mechanism. The PRC developed could be used as an ISCO-based passive barrier system for plume control, and it has the potential to become a cost-effective alternative for the remediation of chlorinated solvent-contaminated groundwater. PMID:24568784

Liang, S H; Chen, K F; Wu, C S; Lin, Y H; Kao, C M

2014-05-01

231

Acute Exposure to Perchlorethylene alters Rat Visual Evoked Potentials in Relation to Brain Concentration  

EPA Science Inventory

These experiments sought to establish a dose-effect relationship between the concentration of perchloroethylene (PCE) in brain tissue and concurrent changes in visual function. A physiologically-based pharmacokinetic (PBPK) model was implemented to predict concentrations of PCE ...

232

Experimental demonstration of an OpenFlow/PCE integrated control plane for IP over translucent WSON with the assistance of a per-request-based dynamic topology server.  

PubMed

To mitigate the potential scalability issues of an OpenFlow-based control plane, a seamless OpenFlow and Path Computation Element (PCE) integrated control plane is proposed, by means of an architecture in which the path computation function is formally decoupled from the controller so the controller can off-load the task to one or more dedicated PCEs using an open and standard interface and protocol, and where the PCE obtains its topology database by means of a dedicated dynamic topology server, which is accessed by the PCE on a per-request basis. The overall feasibility and performance metrics of this integrated control plane are experimentally verified and quantitatively evaluated on a real IP over translucent Wavelength Switched Optical Network (WSON) testbed. PMID:23481952

Liu, Lei; Casellas, Ramon; Tsuritani, Takehiro; Morita, Itsuro; Martínez, Ricardo; Muñoz, Raül

2013-02-25

233

Variability in carbon isotopic fractionation during biodegradation of chlorinated ethenes: implications for field applications.  

PubMed

Stable carbon isotopic analysis has the potential to assess biodegradation of chlorinated ethenes. Significant isotopic shifts, which can be described by Rayleigh enrichment factors, have been observed for the biodegradation of trichloroethlyene (TCE), cis-dichloroethylene (cDCE), and vinyl chloride (VC). However, until this time, no systematic investigation of isotopic fractionation during perchloroethylene (PCE) degradation has been undertaken. In addition, there has been no comparison of isotopic fractionation by different microbial consortia, nor has there been a comparison of isotopic fractionation by consortia generated from the same source, but growing under different conditions. This study characterized carbon isotopic fractionation during reductive dechlorination of the chlorinated ethenes, PCE in particular, for microbial consortia from two different sources growing under different environmental conditions in order to assess the extent to which different microbial consortia result in different fractionation factors. Rayleigh enrichment factors of -13.8@1000, -20.4@1000, and -22.4@1000 were observed for TCE, cDCE, and VC, respectively, for dechlorination by the KB-1 consortium. In contrast, isotopic fractionation during reductive dechlorination of perchloroethylene (PCE) could not always be approximated by a Rayleigh model. Dechlorination by one consortium followed Rayleigh behavior (epsilon = -5.2), while a systematic change in the enrichment factor was observed over the course of PCE degradation by two other consortia. Comparison of all reported enrichment factors for reductive dechlorination of the chlorinated ethenes shows significant variation between experiments. Despite this variability, these results demonstrate that carbon isotopic analysis can provide qualitative evidence of the occurrence and relative extent of microbial reductive dechlorination of the chlorinated ethenes. PMID:11351533

Slater, G F; Lollar, B S; Sleep, B E; Edwards, E A

2001-03-01

234

Efficient Bayesian updating with PCE-based particle filters based on polynomial chaos expansion and CO2 storage  

NASA Astrophysics Data System (ADS)

Underground flow systems, such as oil or gas reservoirs and CO2 storage sites, are an important and challenging class of complex dynamic systems. Lacking information about distributed systems properties (such as porosity, permeability,...) leads to model uncertainties up to a level where quantification of uncertainties may become the dominant question in application tasks. History matching to past production data becomes an extremely important issue in order to improve the confidence of prediction. The accuracy of history matching depends on the quality of the established physical model (including, e.g. seismic, geological and hydrodynamic characteristics, fluid properties etc). The history matching procedure itself is very time consuming from the computational point of view. Even one single forward deterministic simulation may require parallel high-performance computing. This fact makes a brute-force non-linear optimization approach not feasible, especially for large-scale simulations. We present a novel framework for history matching which takes into consideration the nonlinearity of the model and of inversion, and provides a cheap but highly accurate tool for reducing prediction uncertainty. We propose an advanced framework for history matching based on the polynomial chaos expansion (PCE). Our framework reduces complex reservoir models and consists of two main steps. In step one, the original model is projected onto a so-called integrative response surface via very recent PCE technique. This projection is totally non-intrusive (following a probabilistic collocation method) and optimally constructed for available reservoir data at the prior stage of Bayesian updating. The integrative response surface keeps the nonlinearity of the initial model at high order and incorporates all suitable parameters, such as uncertain parameters (porosity, permeability etc.) and design or control variables (injection rate, depth etc.). Technically, the computational costs for constructing the response surface depend on the number of parameters and the expansion degree. Step two consists of Bayesian updating in order to match the reduced model to available measurements of state variables or other past or real-time observations of system behavior (e.g. past production data or pressure at monitoring wells during a certain time period). In step 2 we apply particle filtering on the integrative response surface constructed at step one. Particle filtering is a strong technique for Bayesian updating which takes into consideration the nonlinearity of inverse problem in history matching more accurately than Ensemble Kalman filter do. Thanks to the computational efficiency of PCE and integrative response surface, Bayesian updating for history matching becomes an interactive task and can incorporate real time measurements.

Oladyshkin, S.; Class, H.; Helmig, R.; Nowak, W.

2011-12-01

235

Adverse Birth Outcomes and Maternal Exposure to Trichloroethylene and Tetrachloroethylene through Soil Vapor Intrusion in New York State  

PubMed Central

Background: Industrial spills of volatile organic compounds (VOCs) in Endicott, New York (USA), have led to contamination of groundwater, soil, and soil gas. Previous studies have reported an increase in adverse birth outcomes among women exposed to VOCs in drinking water. Objective: We investigated the prevalence of adverse birth outcomes among mothers exposed to trichloroethylene (TCE) and tetrachloroethylene [or perchloroethylene (PCE)] in indoor air contaminated through soil vapor intrusion. Methods: We examined low birth weight (LBW), preterm birth, fetal growth restriction, and birth defects among births to women in Endicott who were exposed to VOCs, compared with births statewide. We used Poisson regression to analyze births and malformations to estimate the association between maternal exposure to VOCs adjusting for sex, mother’s age, race, education, parity, and prenatal care. Two exposure areas were identified based on environmental sampling data: one area was primarily contaminated with TCE, and the other with PCE. Results: In the TCE-contaminated area, adjusted rate ratios (RRs) were significantly elevated for LBW [RR = 1.36; 95% confidence interval (CI): 1.07, 1.73; n = 76], small for gestational age (RR = 1.23; 95% CI: 1.03, 1.48; n = 117), term LBW (RR = 1.68; 95% CI: 1.20, 2.34; n = 37), cardiac defects (RR = 2.15; 95% CI: 1.27, 3.62; n = 15), and conotruncal defects (RR = 4.91; 95% CI: 1.58, 15.24; n = 3). In the PCE-contaminated area, RRs for cardiac defects (five births) were elevated but not significantly. Residual socioeconomic confounding may have contributed to elevations of LBW outcomes. Conclusions: Maternal residence in both areas was associated with cardiac defects. Residence in the TCE area, but not the PCE area, was associated with LBW and fetal growth restriction. PMID:22142966

Lewis-Michl, Elizabeth L.; Gomez, Marta I.

2011-01-01

236

Metal mobility during in situ chemical oxidation of TCE by KMnO4.  

PubMed

The potential for trace-metal contamination of aquifers as a side effect of In Situ Chemical Oxidation (ISCO) of chlorinated solvent contamination by KMnO(4) is investigated with column experiments. The experiments investigate metal mobility during in situ chemical oxidation of TCE by KMnO(4) under conditions where pH, flow rate, KMnO(4), TCE, and trace-metal concentrations were controlled. During ISCO, the injection of MnO(4) creates oxidizing conditions, and acidity released by the reactions causes a tendency toward low pH in aquifers. In order to evaluate the role of pH buffering on metal mobility, duplicate columns were constructed, one packed with pure silica sand, and one with a mixture of silica sand and calcite. Aqueous solutions of TCE and KMnO(4) (with 1 mg/L Cu, Pb, Zn, Mo, Ni, and Cr(VI)) were allowed to mix at the inlet to the columns. After the completion of the experiments, samples of Mn oxide were removed from the columns and analyzed by analytical scanning and transmission electron microscopy. In order to relate the results of the laboratory experiments to field settings, the analyses of Mn-oxide samples from the lab experiments were compared to samples of Mn oxide collected from a field-scale chemical-oxidation experiment that were also analyzed by analytical electron microscopy as well as time-of-flight secondary-ion mass spectroscopy. The pH ranged from 2.40 in the silica sand column to 6.25 in the calcite-containing column. The data indicate that aqueous Mo, Pb, Cu and Ni concentrations are attenuated almost completely within the columns. In contrast, Zn concentrations are not significantly attenuated and Cr(VI) is transported conservatively. The results indicate that within the range 2.40 to 6.25, metal mobility is not affected by pH. Comparison of analyses of Mn-oxide from the lab and field demonstrate that a variety of metals are sequestered from solution by Mn oxide. PMID:16876907

Al, Tom A; Banks, Vernon; Loomer, Diana; Parker, Beth L; Ulrich Mayer, K

2006-11-20

237

An Approach Using Gas Monitoring to Find the Residual TCE Location in the Unsaturated Zone of Woosan Industrial Complex (WIC), Korea  

NASA Astrophysics Data System (ADS)

An area accommodating various industrial facilities has fairly high probability of groundwater contamination with multiple chlorinated solvents such as trichloroethene (TCE), carbon tetrachloride (CT), and chloroform (CF). Source tracing of chlorinated solvents in the unsaturated zone is an essential procedure for the management and remediation of contaminated area. From the previous study on seasonal variations in hydrological stresses and spatial variations in geologic conditions on a TCE plume, the existence of residual DNAPLs at or above the water table has proved. Since TCE is one of the frequently detected VOCs (Volatile Organic Compounds) in groundwater, residual TCE can be detected by gas monitoring. Therefore, monitoring of temporal and spatial variations in the gas phase TCE contaminant at an industrial complex in Wonju, Korea, were used to find the residual TCE locations. As pilot tests, TCE gas samples collected in the unsaturated zone at 4 different wells were analyzed using SPME (Solid Phase MicroExtraction) fiber and Gas Chromatography (GC). The results indicated that detecting TCE in gas phase was successful from these wells and TCE analysis on gas samples, collected from the unsaturated zone, will be useful for source area characterization. However, some values were too high to doubt the accuracy of the current method, which needs a preliminary lab test with known concentrations. The modified experiment setups using packer at different depths are in process to find residual TCE locations in the unsaturated zone. Meanwhile, several PVD (polyethylene-membrane Passive Vapor Diffusion) samplers were placed under water table to detect VOCs by equilibrium between air in the vial and VOCs in pore water.

Koh, Y.; Lee, S.; Yang, J.; Lee, K.

2012-12-01

238

Carbon isotope fractionation during reductive dechlorination of TCE in batch experiments with iron samples from reactive barriers.  

PubMed

Reductive dechlorination of trichloroethene (TCE) by zero-valent iron produces a systematic enrichment of 13C in the remaining substrate that can be described using a Rayleigh model. In this study, fractionation factors for TCE dechlorination with iron samples from two permeable reactive barriers (PRBs) were established in batch experiments. Samples included original unused iron as well as material from a barrier in Belfast after almost 4 years of operation. Despite the variety of samples, carbon isotope fractionations of TCE were remarkably similar and seemed to be independent of iron origin, reaction rate, and formation of precipitates on the iron surfaces. The average enrichment factor for all experiments was -10.1 per thousand (+/- 0.4 per thousand). These results indicate that the enrichment factor provides a powerful tool to monitor the reaction progress, and thus the performance, of an iron-reactive barrier over time. The strong fractionation observed may also serve as a tool to distinguish between insufficient residence time in the wall and a possible bypassing of the wall by the plume, which should result in an unchanged isotopic signature of the TCE. Although further work is necessary to apply this stable isotope method in the field, it has potential to serve as a unique monitoring tool for PRBs based on zero-valent iron. PMID:14516939

Schüth, Christoph; Bill, Markus; Barth, Johannes A C; Slater, Gregory F; Kalin, Robert M

2003-10-01

239

Abiotic and Biotic Transformation of TCE under Sulfate Reducing Conditions: the Role of Spatial Heterogeneity (Monterey, CA)  

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 ...

240

Abiotic Removal of TCE and cis-DCE by Magnetite under Aerobic Conditions in Ground Water (Maryland)  

EPA Science Inventory

The former Twin Cities Army Ammunition Plant (TCAAP) is located just north of St. Paul, Minnesota. Disposal of chlorinated solvents at the Building102 site on the TCAAP contaminated groundwater in the shallow, unconsolidated sand aquifer with TCE and cis-DCE. Concentrations of ...

241

Application of fluorescent antibody and enzyme-linked immunosorbent assays for TCE and PAH degrading bacteria  

SciTech Connect

Historically, methods used to identify methanotrophic and polyaromatic hydrocarbon-degrading (PAH) bacteria in environmental samples have been inadequate because isolation and identification procedures are time-consuming and often fail to separate specific bacteria from other environmental microorganisms. Methanotrophic bacteria have been isolated and characterized from TCE-contaminated soils (Bowman et al. 1993; Fliermans et al., 1988). Fliermans et al., (1988) and others demonstrated that cultures enriched with methane and propane could cometabolically degrade a wide variety of chlorinated aliphatic hydrocarbons including ethylene; 1,2-cisdichloroethylene (c-DCE); 1,2-trans-dichloroethylene (t-DCE); vinyl chloride (VC); toluene; phenol and cresol. Characterization of select microorganisms in the natural setting is important for the evaluation of bioremediation potential and its effectiveness. This realization has necessitated techniques that are selective, sensitive and easily applicable to soils, sediments, and groundwater (Fliermans, et al., 1994). Additionally these techniques can identify and quantify microbial types in situ in real time

Brigmon, R.L.; Franck, M.; Brey, J.; Scott, D.; Lanclos, K.; Fliermans, C.

1996-07-01

242

Consideration of Treatment Performance Assessment Metrics for a TCE Source Area Bioremediation (SABRe project)  

NASA Astrophysics Data System (ADS)

Techniques for optimizing the removal of NAPL mass in source zones have advanced at a more rapid rate than strategies to assess treatment performance. Informed selection of remediation approaches would be easier if measurements of performance were more directly transferable. We developed a number of methods based on data generated from multilevel sampler (MLS) transects to assess the effectiveness of a bioaugmentation/biostimulation trial in a TCE source residing in a terrace gravel aquifer in the East Midlands, UK. In this spatially complex aquifer, treatment inferred from long screen monitoring well data was not as reliable as that from consideration of mass flux changes across transects installed in and downgradient of the source. Falling head tests were conducted in the MLS ports to generate the necessary hydraulic conductivity (K) data. Combining K with concentration provides a mass flux map that allows calculation of mass turnover and an assessment of where in the complex geology the greatest turnover occurred. Five snapshots over a 600-day period indicate a marked reduction in TCE flux, suggesting a significant reduction in DNAPL mass over that expected due to natural processes. However, persistence of daughter products suggested that complete dechlorination did not occur. The MLS fence data also revealed that delivery of both carbon source and pH buffer were not uniform across the test zone. This may have lead to the generation of niches of iron(III) and sulphate reduction as well as methanogenesis, which impacted on dechlorination processes. In the absence of this spatial data, it is difficult to reconcile apparent treatment as indicated in monitoring well data to on-going processes.

Cai, Z.; Wilson, R. D.

2009-05-01

243

Analysis of sources of bulk conductivity change in saturated silica sand after unbuffered TCE oxidation by permanganate  

NASA Astrophysics Data System (ADS)

Time lapse resistivity surveys could potentially improve monitoring of permanganate-based in situ chemical oxidation (ISCO) of organic contaminants such as trichloroethene (TCE) by tracking changes in subsurface conductivity that result from injection of permanganate and oxidation of the contaminant. Bulk conductivity and pore fluid conductivity changes during unbuffered TCE oxidation using permanganate are examined through laboratory measurements and conductivity modeling using PHREEQC in fluid samples and porous media samples containing silica sand. In fluid samples, oxidation of one TCE molecule produces three chloride ions and one proton, resulting in an increase in fluid electrical conductivity despite the loss of two permanganate ions in the reaction. However, in saturated sand samples in which up to 8 mM TCE was oxidized, at least 94% of the fluid conductivity associated with the presence of protons was removed within 3 h of sand contact, most likely through protonation of silanol groups found on the surface of the sand grains. Minor conductivity effects most likely associated with pH-dependent reductive dissolution of manganese dioxide were also observed but not accounted for in pore-fluid conductivity modeling. Unaccounted conductivity effects resulted in an under-calculation of post-reaction pore fluid conductivity of 2.1% to 5.5%. Although small increases in the porous media formation factor resulting from precipitation of manganese dioxide were detected (about 3%), these increases could not be confirmed to be statistically significant. Both injection of permanganate and oxidation of TCE cause increases in bulk conductivity that would be detectable through time-lapse resistivity surveys in field conditions.

Hort, Ryan D.; Revil, André; Munakata-Marr, Junko

2014-09-01

244

Analysis of sources of bulk conductivity change in saturated silica sand after unbuffered TCE oxidation by permanganate.  

PubMed

Time lapse resistivity surveys could potentially improve monitoring of permanganate-based in situ chemical oxidation (ISCO) of organic contaminants such as trichloroethene (TCE) by tracking changes in subsurface conductivity that result from injection of permanganate and oxidation of the contaminant. Bulk conductivity and pore fluid conductivity changes during unbuffered TCE oxidation using permanganate are examined through laboratory measurements and conductivity modeling using PHREEQC in fluid samples and porous media samples containing silica sand. In fluid samples, oxidation of one TCE molecule produces three chloride ions and one proton, resulting in an increase in fluid electrical conductivity despite the loss of two permanganate ions in the reaction. However, in saturated sand samples in which up to 8mM TCE was oxidized, at least 94% of the fluid conductivity associated with the presence of protons was removed within 3h of sand contact, most likely through protonation of silanol groups found on the surface of the sand grains. Minor conductivity effects most likely associated with pH-dependent reductive dissolution of manganese dioxide were also observed but not accounted for in pore-fluid conductivity modeling. Unaccounted conductivity effects resulted in an under-calculation of post-reaction pore fluid conductivity of 2.1% to 5.5%. Although small increases in the porous media formation factor resulting from precipitation of manganese dioxide were detected (about 3%), these increases could not be confirmed to be statistically significant. Both injection of permanganate and oxidation of TCE cause increases in bulk conductivity that would be detectable through time-lapse resistivity surveys in field conditions. PMID:25064184

Hort, Ryan D; Revil, André; Munakata-Marr, Junko

2014-09-01

245

Affinity for risky behaviors following prenatal and early childhood exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study  

PubMed Central

Background Many studies of adults with acute and chronic solvent exposure have shown adverse effects on cognition, behavior and mood. No prior study has investigated the long-term impact of prenatal and early childhood exposure to the solvent tetrachloroethylene (PCE) on the affinity for risky behaviors, defined as smoking, drinking or drug use as a teen or adult. Objectives This retrospective cohort study examined whether early life exposure to PCE-contaminated drinking water influenced the occurrence of cigarette smoking, alcohol consumption, and drug use among adults from Cape Cod, Massachusetts. Methods Eight hundred and thirty-one subjects with prenatal and early childhood PCE exposure and 547 unexposed subjects were studied. Participants completed questionnaires to gather information on risky behaviors as a teenager and young adult, demographic characteristics, other sources of solvent exposure, and residences from birth through 1990. PCE exposure was estimated using the U.S. EPA's water distribution system modeling software (EPANET) that was modified to incorporate a leaching and transport model to estimate PCE exposures from pipe linings. Results Individuals who were highly exposed to PCE-contaminated drinking water during gestation and early childhood experienced 50-60% increases in the risk of using two or more major illicit drugs as a teenager or as an adult (Relative Risk (RR) for teen use = 1.6, 95% CI: 1.2-2.2; and RR for adult use = 1.5, 95% CI: 1.2-1.9). Specific drugs for which increased risks were observed included crack/cocaine, psychedelics/hallucinogens, club/designer drugs, Ritalin without a prescription, and heroin (RRs:1.4-2.1). Thirty to 60% increases in the risk of certain smoking and drinking behaviors were also seen among highly exposed subjects. Conclusions The results of this study suggest that risky behaviors, particularly drug use, are more frequent among adults with high PCE exposure levels during gestation and early childhood. These findings should be confirmed in follow-up investigations of other exposed populations. PMID:22136431

2011-01-01

246

Exposure of Daphnia magna to trichloroethylene (TCE) and vinyl chloride (VC): Evaluation of gene transcription, cellular activity, and life-history parameters.  

PubMed

Trichloroethylene (TCE) is a ubiquitous contaminant classified as a human carcinogen. Vinyl chloride (VC) is primarily used to manufacture polyvinyl chloride and can also be a degradation product of TCE. Very few data exist on the toxicity of TCE and VC in aquatic organisms particularly at environmentally relevant concentrations. The aim of this study was to evaluate the sub-lethal effects (10day exposure; 0.1; 1; 10µg/L) of TCE and VC in Daphnia magna at the gene, cellular, and life-history levels. Results indicated impacts of VC on the regulation of genes related to glutathione-S-transferase (GST), juvenile hormone esterase (JHE), and the vitelline outer layer membrane protein (VMO1). On the cellular level, exposure to 0.1, 1, and 10µg/L of VC significantly increased the activity of JHE in D. magna and TCE increased the activity of chitinase (at 1 and 10µg/L). Results for life-history parameters indicated a possible tendency of TCE to affect the number of molts at the individual level in D. magna (p=0.051). Measurement of VG-like proteins using the alkali-labile phosphates (ALP) assay did not show differences between TCE treated organisms and controls. However, semi-quantitative measurement using gradient gel electrophoresis (213-218kDa) indicated significant decrease in VG-like protein levels following exposure to TCE at all three concentrations. Overall, results indicate effects of TCE and VC on genes and proteins related to metabolism, reproduction, and growth in D. magna. PMID:25733190

Houde, Magali; Douville, Mélanie; Gagnon, Pierre; Sproull, Jim; Cloutier, François

2015-06-01

247

Competing TCE and cis-DCE degradation kinetics by zero-valent iron—experimental results and numerical simulation  

NASA Astrophysics Data System (ADS)

The successful dechlorination of mixtures of chlorinated hydrocarbons with zero-valent metals requires information concerning the kinetics of simultaneous degradation of different contaminants. This includes intraspecies competitive effects (loading of the reactive iron surface by a single contaminant) as well as interspecies competition of several contaminants for the reactive sites available. In columns packed with zero-valent iron, the degradation behaviour of trichloroethylene (TCE), cis-dichloroethylene (DCE) and mixtures of both was measured in order to investigate interspecies competition. Although a decreasing rate of dechlorination is to be expected, when several degradable substances compete for the reactive sites on the iron surface, TCE degradation is nearly unaffected by the presence of cis-DCE. In contrast, cis-DCE degradation rates decrease significantly when TCE is added. A new modelling approach is developed in order to identify and quantify the observed competitive effects. The numerical model TBC (Transport, Biochemistry and Chemistry, Schäfer et al., 1998a) is used to describe adsorption, desorption and dechlorination in a mechanistic way. Adsorption and degradation of a contaminant based on a limited number of reactive sites leads to a combined zero- and first-order degradation kinetics for high and low concentrations, respectively. The adsorption of several contaminants with different sorption parameters to a limited reactive surface causes interspecies competition. The reaction scheme and the parameters required are successfully transferred from Arnold and Roberts (2000b) to the model TBC. The degradation behaviour of the mixed contamination observed in the column experiments can be related to the adsorption properties of TCE and cis-DCE. By predicting the degradation of the single substances TCE and cis-DCE as well as mixtures of both, the calibrated model is used to investigate the effects of interspecies competition on the design of permeable reactive iron barriers. Even if TCE is present in only small concentrations (>3% of molar cis-DCE concentration) it is the contaminant limiting the residence time and the required thickness of the iron barrier.

Schäfer, Dirk; Köber, Ralf; Dahmke, Andreas

2003-09-01

248

Microbially enhanced dissolution and reductive dechlorination of PCE by a mixed culture: model validation and sensitivity analysis.  

PubMed

Reductive dechlorination catalyzed by organohalide-respiring bacteria is often considered for remediation of non-aqueous phase liquid (NAPL) source zones due to cost savings, ease of implementation, regulatory acceptance, and sustainability. Despite knowledge of the key dechlorinators, an understanding of the processes and factors that control NAPL dissolution rates and detoxification (i.e., ethene formation) is lacking. A recent column study demonstrated a 5-fold cumulative enhancement in tetrachloroethene (PCE) dissolution and ethene formation (Amos et al., 2009). Spatial and temporal monitoring of key geochemical and microbial (i.e., Geobacter lovleyi and Dehalococcoides mccartyi strains) parameters in the column generated a data set used herein as the basis for refinement and testing of a multiphase, compositional transport model. The refined model is capable of simulating the reactive transport of multiple chemical constituents produced and consumed by organohalide-respiring bacteria and accounts for substrate limitations and competitive inhibition. Parameter estimation techniques were used to optimize the values of sensitive microbial kinetic parameters, including maximum utilization rates, biomass yield coefficients, and endogenous decay rates. Comparison and calibration of model simulations with the experimental data demonstrate that the model is able to accurately reproduce measured effluent concentrations, while delineating trends in dechlorinator growth and reductive dechlorination kinetics along the column. Sensitivity analyses performed on the optimized model parameters indicate that the rates of PCE and cis-1,2-dichloroethene (cis-DCE) transformation and Dehalococcoides growth govern bioenhanced dissolution, as long as electron donor (i.e., hydrogen flux) is not limiting. Dissolution enhancements were shown to be independent of cis-DCE accumulation; however, accumulation of cis-DCE, as well as column length and flow rate (i.e., column residence time), strongly influenced the extent of reductive dechlorination. When cis-DCE inhibition was neglected, the model over-predicted ethene production ten-fold, while reductions in residence time (i.e., a two-fold decrease in column length or two-fold increase in flow rate) resulted in a more than 70% decline in ethene production. These results suggest that spatial and temporal variations in microbial community composition and activity must be understood to model, predict, and manage bioenhanced NAPL dissolution. PMID:23774611

Chen, Mingjie; Abriola, Linda M; Amos, Benjamin K; Suchomel, Eric J; Pennell, Kurt D; Löffler, Frank E; Christ, John A

2013-08-01

249

Microbially enhanced dissolution and reductive dechlorination of PCE by a mixed culture: Model validation and sensitivity analysis  

NASA Astrophysics Data System (ADS)

Reductive dechlorination catalyzed by organohalide-respiring bacteria is often considered for remediation of non-aqueous phase liquid (NAPL) source zones due to cost savings, ease of implementation, regulatory acceptance, and sustainability. Despite knowledge of the key dechlorinators, an understanding of the processes and factors that control NAPL dissolution rates and detoxification (i.e., ethene formation) is lacking. A recent column study demonstrated a 5-fold cumulative enhancement in tetrachloroethene (PCE) dissolution and ethene formation (Amos et al., 2009). Spatial and temporal monitoring of key geochemical and microbial (i.e., Geobacter lovleyi and Dehalococcoides mccartyi strains) parameters in the column generated a data set used herein as the basis for refinement and testing of a multiphase, compositional transport model. The refined model is capable of simulating the reactive transport of multiple chemical constituents produced and consumed by organohalide-respiring bacteria and accounts for substrate limitations and competitive inhibition. Parameter estimation techniques were used to optimize the values of sensitive microbial kinetic parameters, including maximum utilization rates, biomass yield coefficients, and endogenous decay rates. Comparison and calibration of model simulations with the experimental data demonstrate that the model is able to accurately reproduce measured effluent concentrations, while delineating trends in dechlorinator growth and reductive dechlorination kinetics along the column. Sensitivity analyses performed on the optimized model parameters indicate that the rates of PCE and cis-1,2-dichloroethene (cis-DCE) transformation and Dehalococcoides growth govern bioenhanced dissolution, as long as electron donor (i.e., hydrogen flux) is not limiting. Dissolution enhancements were shown to be independent of cis-DCE accumulation; however, accumulation of cis-DCE, as well as column length and flow rate (i.e., column residence time), strongly influenced the extent of reductive dechlorination. When cis-DCE inhibition was neglected, the model over-predicted ethene production ten-fold, while reductions in residence time (i.e., a two-fold decrease in column length or two-fold increase in flow rate) resulted in a more than 70% decline in ethene production. These results suggest that spatial and temporal variations in microbial community composition and activity must be understood to model, predict, and manage bioenhanced NAPL dissolution.

Chen, Mingjie; Abriola, Linda M.; Amos, Benjamin K.; Suchomel, Eric J.; Pennell, Kurt D.; Löffler, Frank E.; Christ, John A.

2013-08-01

250

Large-scale production of bacterial consortia for remediation of chlorinated solvent-contaminated groundwater.  

PubMed

Chlorinated solvents such as perchloroethylene (PCE) and trichloroethylene (TCE) continue to be significant groundwater contaminants throughout the USA. In many cases efficient bioremediation of aquifers contaminated with these chemicals requires the addition of exogenous microorganisms, specifically members of the genus Dehalococcoides (DHC). This process is referred to as bioaugmentation. In this study a fed-batch fermentation process was developed for producing large volumes (to 3,200 L) of DHC-containing consortia suitable for treating contaminated aquifers. Three consortia enriched from three different sites were grown anaerobically with sodium lactate as an electron donor and PCE or TCE as an electron acceptor. DHC titers in excess of 10(11) DHC/L could be reproducibly obtained at all scales tested and with all three of the enrichment cultures. The mean specific DHC growth rate for culture SDC-9 was 0.036 +/- 0.005 (standard error, SE)/h with a calculated mean doubling time of 19.3 +/- 2.7 (SE) h. Finished cultures could be concentrated approximately tenfold by membrane filtration and stored refrigerated (4 degrees C) for more that 40 days without measurable loss of activity. Dehalogenation of PCE by the fermented cultures was affected by pH with no measurable activity at pH <5.0. PMID:19521729

Vainberg, Simon; Condee, Charles W; Steffan, Robert J

2009-09-01

251

Thermally Activated Persulfate Oxidation of Trichloroethylene (TCE) and 1,1,1Trichloroethane (TCA) in Aqueous Systems and Soil Slurries  

Microsoft Academic Search

Under thermally activated conditions (i.e., temperature of 40?99°C), there is considerable evidence that the persulfate anion () can be converted to a powerful oxidant known as the sulfate free radical (), which could be used in situ to destroy groundwater contaminants. In this laboratory study only limited trichloroethylene (TCE) degradation and no 1,1,1-trichloroethane (TCA) degradation was observed at 20°C. However,

Chen Ju Liang; Clifford J. Bruell; Michael C. Marley; Kenneth L. Sperry

2003-01-01

252

Field performance of air-sparging system for removing TCE from groundwater  

SciTech Connect

The removal of volatile organic compounds from groundwater by air sparging (AS) is well-established, although reliable methods for predicting the time required to reach site closure have not been established. To develop and improved understanding of mass transfer processes that limit AS performance, two extended controlled shutdowns of an operating AS system were performed. Monitoring of TCE concentrations in source zone groundwater indicated tailing and rebound behavior similar to that observed for pump-and-treat systems. A simple two-compartment model provided a reasonable description of the 3-year AS history, using parameters calibrated from data collected during the first shutdown period. Comparison of the calibrated rate constants with parameters estimated from laboratory soil columns suggest that, for the study site, aqueous diffusion to discrete air channels has a stronger influence on system performance than rate-limited desorption. Predictions based on the calibrated model indicated that restoration of the source zone to drinking water standards would require approximately 1 decade for the current AS system.

Rabideau, A.J.; Blayden, J.M.; Ganguly, C. [State Univ. of New York, Buffalo, NY (United States). Dept. of Civil, Structural, and Environmental Engineering] [State Univ. of New York, Buffalo, NY (United States). Dept. of Civil, Structural, and Environmental Engineering

1999-01-01

253

Degradation of TCE using Persulfate (PS) and Peroxymonosulfate (PMS): Effect of Inorganic Ions in Groundwater  

E-print Network

Abstract — The objective of this study was to investigate the effects of inorganic ions on persulfate (PS) and peroxymonosulfate (PMS) oxidation to degrade trichloroethylene (TCE) in groundwater. First, the groundwater samples, which was taken from Wonju, Korea, were analyzed, and the highest concentration of target ions (Mg 2+, Ca 2+, Fe 2+, Mn 2+, Cl-, HCO 3) in those samples were used for the batch experiment. Based on batch test, all of target ions did not neither increase nor decrease the reactivity of both PS and PMS. Because of the fluctuation of groundwater compositions, it could be worthwhile to evaluate which ions increase or decrease the reactivity of oxidants. Therefore, a batch system with an excess of target ion was tested. The results showed that ferrous ion increased the reactivity of both PS and PMS. However, chloride ion increased the reactivity of PMS, but it inhibited the reactivity of PS. Moreover, residual concentration of PMS and PS were remained approximately 97~98%, and the pH of system was dramatically reduced when PMS was used. The last of target ions (Mg 2+, Ca 2+, Mn 2+, HCO 3) will be also tested with the condition of an excess.

Ki-man Park; Hong-kyun Lee; Si-hyun Do; Sung-ho Kong

254

Simulating an exclusion zone for vapour intrusion of TCE from groundwater into indoor air.  

PubMed

This paper is an extension of the work by Yu et al. (2009) to examine exposure pathways of volatile organic compounds (VOCs) originating from a NAPL source zone located below the water table, and their potential impact on multiple residential dwellings down-gradient of the source zone. The three-dimensional problem geometry is based on the Rivett (1995) field experiment in the Borden aquifer, and contains houses located both above and adjacent to the groundwater plume in order to define an exclusion zone. Simulation results using the numerical model CompFlow Bio indicate that houses which are laterally offset from the groundwater plume are less affected by vapour intrusion than those located directly above the plume due to limited transverse horizontal flux of TCE within the groundwater plume, in agreement with the ASTM (2008) guidance. Uncertainty in the simulated indoor air concentration is sensitive to heterogeneity in the permeability structure of a stratigraphically continuous aquifer, with uncertainty defined as the probability of simulated indoor air concentrations exceeding the NYSDOH (2005) regulatory limit. Within this uncertainty framework, this work shows that the Johnson and Ettinger (1991), ASTM (2008) and CompFlow Bio models all delineate an identical exclusion zone at a 99.9% confidence interval of indoor air concentrations based on the probability of exceedence. PMID:23026643

Wang, Xiaomin; Unger, Andre J A; Parker, Beth L

2012-10-01

255

Simulating an exclusion zone for vapour intrusion of TCE from groundwater into indoor air  

NASA Astrophysics Data System (ADS)

This paper is an extension of the work by Yu et al. (2009) to examine exposure pathways of volatile organic compounds (VOCs) originating from a NAPL source zone located below the water table, and their potential impact on multiple residential dwellings down-gradient of the source zone. The three-dimensional problem geometry is based on the Rivett (1995) field experiment in the Borden aquifer, and contains houses located both above and adjacent to the groundwater plume in order to define an exclusion zone. Simulation results using the numerical model CompFlow Bio indicate that houses which are laterally offset from the groundwater plume are less affected by vapour intrusion than those located directly above the plume due to limited transverse horizontal flux of TCE within the groundwater plume, in agreement with the ASTM (2008) guidance. Uncertainty in the simulated indoor air concentration is sensitive to heterogeneity in the permeability structure of a stratigraphically continuous aquifer, with uncertainty defined as the probability of simulated indoor air concentrations exceeding the NYSDOH (2005) regulatory limit. Within this uncertainty framework, this work shows that the Johnson and Ettinger (1991), ASTM (2008) and CompFlow Bio models all delineate an identical exclusion zone at a 99.9% confidence interval of indoor air concentrations based on the probability of exceedence.

Wang, Xiaomin; Unger, Andre J. A.; Parker, Beth L.

2012-10-01

256

Effects of Reduced Sulfur Compounds on Pd-catalytic Hydrodechlorination of TCE in Groundwater by Cathodic H2 under Electrochemically-induced Oxidizing Conditions  

PubMed Central

Reduced sulfur compounds (RSCs) poison Pd catalysts for catalytic hydrodechlorination of contaminants in anoxic groundwater. This study investigates the effects of RSCs on Pd-catalytic hydrodechlorination of trichloroethylene (TCE) in oxic groundwater. Water electrolysis in an undivided electrolytic cell is used to produce H2 for TCE hydrodechlorination under oxidizing conditions. TCE is efficiently hydrodechlorinated to ethane, with significant accumulation of H2O2 under acidic conditions. Presence of sulfide at concentrations less than 93.8 ?M moderately inhibits TCE hydrodechlorination and H2O2 production. Presence of sulfite at low concentrations (? 1 mM) significantly enhances TCE decay, while at high concentration (3 mM) inhibits initially and enhances afterwards when sulfite concentration declines to less than 1 mM. Using radical scavenging experiments and electron spin resonance assay, SO3•? which is generated from sulfite under oxidizing conditions is validated as the new reactive species contributing to the enhancement. This study reveals a distinct mechanism of effect of sulfite on TCE hydrodechlorination by Pd and H2 in oxic groundwater and presents an alternative approach to increasing resistance of Pd to RSCs poisoning. PMID:23962132

Yuan, Songhu; Chen, Mingjie; Mao, Xuhui; Alshawabkeh, Akram N.

2014-01-01

257

Field and lab trials of PCE-based OSNR-aware dynamic restoration in multi-domain GMPLS-enabled translucent WSON.  

PubMed

Dynamic lightpath restoration is a key issue in wavelength switched optical networks (WSON). On the other hand, the introduction of the path computation element (PCE) and the generalized multi-protocol label switching (GMPLS) architectures into WSON as control plane technologies is expected to bring more intelligence and to enable the dynamic computation and control of end-to-end lightpaths in a cost-efficient manner. In this paper, for the first time and through a lab trial with four domains and a field trial located in Japan and Spain, we experimentally present PCE-based optical signal to noise ratio (OSNR)-aware dynamic restoration in multi-domain GMPLS-enabled translucent WSON, assessing the overall feasibility of the proposed techniques and quantitatively evaluating the service disruption time and path computation latency during end-to-end lightpath restoration. PMID:22274241

Liu, Lei; Casellas, Ramon; Tsuritani, Takehiro; Morita, Itsuro; Okamoto, Shuichi; Martínez, Ricardo; Muñoz, Raül

2011-12-19

258

Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Effects of Hydrostratigraphy on Transport of PCE, Operable Unit 1, Savage Superfund Site, Milford, New Hampshire  

USGS Publications Warehouse

The Savage Municipal Well Superfund site in the Town of Milford, New Hampshire, was underlain by a 0.5-square mile plume (as mapped in 1994) of volatile organic compounds (VOCs), most of which consisted of tetrachloroethylene (PCE). The plume occurs mostly within highly transmissive stratified-drift deposits but also extends into underlying till and bedrock. The plume has been divided into two areas called Operable Unit 1 (OU1), which contains the primary source area, and Operable Unit 2 (OU2), which is defined as the extended plume area outside of OU1. The OU1 remedial system includes a low-permeability barrier wall that encircles the highest detected concentrations of PCE and a series of injection and extraction wells to contain and remove contaminants. The barrier wall likely penetrates the full thickness of the sand and gravel; in many places, it also penetrates the full thickness of the underlying basal till and sits atop bedrock. From 1998 to 2004, PCE concentrations decreased by an average of 80 percent at most wells outside the barrier wall. However, inside the barrier, PCE concentrations greater than 10,000 micrograms per liter (ug/L) still exist (2008). The remediation of these areas of recalcitrant PCE presents challenges to successful remediation. The U.S. Geological Survey (USGS), in cooperation with the New Hampshire Department of Environmental Services (NHDES) and the U.S. Environmental Protection Agency (USEPA), Region 1, is studying the solute transport of VOCs (primarily PCE) in contaminated groundwater in the unconsolidated sediments (overburden) of the Savage site and specifically assisting in the evaluation of the effectiveness of remedial operations in the OU1 area. As part of this effort, the USGS analyzed the subsurface stratigraphy to help understand hydrostratigraphic controls on remediation. A combination of lithologic, borehole natural gamma-ray and electromagnetic (EM) induction logging, and test drilling has identified 11 primary hydrostratigraphic units in OU1. These 11 units consist of several well-sorted sandy layers with some gravel that are separated by poorly sorted cobble layers with a fine-grained matrix. Collectively these units represent glacial sediments deposited by localized ice-margin fluctuations. For the most part, the units are semi-planar, particularly the cobble units, and truncated by an undulating bedrock surface. The lowermost unit is a basal till that ranges in thickness from zero to greater than 10 feet and mantles the bedrock surface. The 11 units have different lithologic and hydraulic characteristics. The hydraulic conductivity of the well-sorted sand and gravel units is typically greater than the conductivity of the poorly sorted cobble units and the basal till. The hydraulic conductivity ranges from 5 to greater than 500 feet per day. Lateral and vertical variation in lithology and hydraulic conductivity are inferred by variations in borehole natural gamma-ray counts and estimates of hydraulic conductivity. The comparison of hydrostratigraphic units with the spatial distribution of PCE concentrations suggests that solute transport away from source areas is primarily lateral within the permeable sandy units in the middle to lower parts of the aquifer. Along the centerline of the interior barrier area, highest PCE concentrations are in the sandy units to the east of suspected source areas.

Harte, Philip T.

2010-01-01

259

Structural Magnetic Resonance Imaging in an adult cohort following prenatal and early postnatal exposure to tetrachloroethylene (PCE)-contaminated drinking water.  

PubMed

This population-based retrospective cohort study examined Structural Magnetic Resonance Imaging (MRI) of the brain 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 Geographic Information System (GIS) methodology. Brain imaging was performed on 26 exposed and 16 unexposed subjects. Scans were acquired on a Philips 3T whole body scanner using the ADNI T1-weighted MP-RAGE scan. The scans were processed by FreeSurfer version 4.3.1 software to obtain measurements of specific brain regions. There were no statistically significant differences between exposed and unexposed subjects on the measures of white matter hypointensities (?: 127.5mm(3), 95% CI: -259.1, 1514.0), white matter volumes (e.g. total cerebral white matter: ?: 21230.0mm(3), 95% CI: -4512.6, 46971.7) or gray matter volumes (e.g. total cerebral gray matter: ?: 11976.0mm(3), 95% CI: -13657.2, 37609.3). The results of this study suggest that exposure to PCE during gestation and early childhood, at the levels observed in this population, is not associated with alterations in the brain structures studied. PMID:23571160

Janulewicz, Patricia A; Killiany, Ronald J; White, Roberta F; Martin, Brett M; Winter, Michael R; Weinberg, Janice M; Aschengrau, Ann

2013-01-01

260

Structural Magnetic Resonance Imaging in an Adult Cohort Following Prenatal and Early Postnatal Exposure to Tetrachloroethylene (PCE)-contaminated Drinking Water  

PubMed Central

This population-based retrospective cohort study examined Structural Magnetic Resonance Imaging (MRI) of the brain 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 Geographic Information System (GIS) methodology. Brain imaging was performed on 26 exposed and 16 unexposed subjects. Scans were acquired on a Philips 3T whole body scanner using the ADNI T1-weighted MP-RAGE scan. The scans were processed by FreeSurfer version 4.3.1 software to obtain measurements of specific brain regions. There were no statistically significant differences between exposed and unexposed subjects on measures of white matter hypointensities (?: 127.5 mm3, 95% CI: ?259.1, 1514.0), white matter volumes (e.g. total cerebral white matter: ?: 21230.0 mm3, 95% CI: ?4512.6, 46971.7) or gray matter volumes (e.g. total cerebral gray matter: ?: 11976.0 mm3, 95% CI: ?13657.2, 37609.3). The results of this study suggest that exposure to PCE during gestation and early childhood, at the levels observed in this population, is not associated with alterations in the brain structures studied. PMID:23571160

Janulewicz, Patricia A; Killiany, Ronald J; White, Roberta F; Martin, Brett M; Winter, Michael R; Weinberg, Janice M; Aschengrau, Ann

2013-01-01

261

Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach.  

PubMed

The typically elevated natural attenuation capacity of riverbed-hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed-hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool-riffle-glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter are anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed-hyporheic zone CHC dechlorination may provide only a partial, somewhat patchy barrier to CHC groundwater plume discharges to a surface water receptor; and, monitoring requirements to assess the variability in CHC attenuation within a reach are expected to be onerous. Further research on transient hyporheic zone dechlorination is recommended. PMID:25461025

Freitas, Juliana G; Rivett, Michael O; Roche, Rachel S; Durrant Neé Cleverly, Megan; Walker, Caroline; Tellam, John H

2015-02-01

262

A Dechlorinating Community Resulting From In Situ Biostimulation of a TCE-contaminated Deep Fracture Basalt Aquifer  

SciTech Connect

Sodium lactate additions to a trichloroethene (TCE) residual source area in deep, fractured basalt at a U.S. Department of Energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase TCE to ethene, and the continued depletion of the residual source since 1999. The bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using PCR-amplified 16S rRNA genes. A clone library of bacterial amplicons was predominated by those from members of the class Clostridia (57 of 93 clones), of which a phylotype most similar to that of the homoacetogen Acetobacterium sp. strain HAAP-1 was most abundant (32 of 93 clones). The remaining Bacteria consisted of phylotypes affiliated with Sphingobacteria, Bacteroides, Spirochaetes, Mollicutes, and Proteobacteria and candidate divisions OP11 and OP3. The two proteobacterial phylotypes were most similar to those of the known dechlorinators Trichlorobacter thiogenes and Sulfurospirillum multivorans. Although not represented by the bacterial clones generated with broad-specificity bacterial primers, a Dehalococcoides-like phylotype was identified with genus-specific primers. Only four distinct phylotypes were detected in the groundwater archaeal library, including predominantly a clone affiliated with the strictly acetoclastic methanogen Methanosaeta concilii (24 of 43 clones). A mixed culture that completely dechlorinates TCE to ethene was enriched from this groundwater, and both communities were characterized by terminal restriction fragment length polymorphism (T-RFLP). According to T-RFLP, the laboratory enrichment community was less diverse overall than the groundwater community, with 22 unique phylotypes as opposed to 43 and a higher percentage of Clostridia, including the Acetobacterium population. Bioreactor archaeal structure was very similar to that of the groundwater community, suggesting that methane is generated primarily via the acetoclastic pathway, using acetate generated by lactate fermentation and acetogenesis in both systems.

T. Wood; D. E. Cummings

2004-12-01

263

Occurrence of mental illness following prenatal and early childhood exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study  

PubMed Central

Background While many studies of adults with solvent exposure have shown increased risks of anxiety and depressive disorders, there is little information on the impact of prenatal and early childhood exposure on the subsequent risk of mental illness. This retrospective cohort study examined whether early life exposure to tetrachloroethylene (PCE)-contaminated drinking water influenced the occurrence of depression, bipolar disorder, post-traumatic stress disorder, and schizophrenia among adults from Cape Cod, Massachusetts. Methods A total of 1,512 subjects born between 1969 and 1983 were studied, including 831 subjects with both prenatal and early childhood PCE exposure and 547 unexposed subjects. Participants completed questionnaires to gather information on mental illnesses, demographic and medical characteristics, other sources of solvent exposure, and residences from birth through 1990. PCE exposure originating from the vinyl-liner of water distribution pipes was assessed using water distribution system modeling software that incorporated a leaching and transport algorithm. Results No meaningful increases in risk ratios (RR) for depression were observed among subjects with prenatal and early childhood exposure (RR: 1.1, 95% CI: 0.9-1.4). However, subjects with prenatal and early childhood exposure had a 1.8-fold increased risk of bipolar disorder (N = 36 exposed cases, 95% CI: 0.9-1.4), a 1.5-fold increased risk post-traumatic stress disorder (N = 47 exposed cases, 95% CI: 0.9-2.5), and a 2.1-fold increased risk of schizophrenia (N = 3 exposed cases, 95% CI: 0.2-20.0). Further increases in the risk ratio were observed for bipolar disorder (N = 18 exposed cases, RR; 2.7, 95% CI: 1.3-5.6) and post-traumatic stress disorder (N = 18 exposed cases, RR: 1.7, 95% CI: 0.9-3.2) among subjects with the highest exposure levels. Conclusions The results of this study provide evidence against an impact of early life exposure to PCE on the risk of depression. In contrast, the results provide support for an impact of early life exposure on the risk of bipolar disorder and post-traumatic stress disorder. The number of schizophrenia cases was too small to draw reliable conclusions. These findings should be confirmed in investigations of other similarly exposed populations. PMID:22264316

2012-01-01

264

Modelling of geochemical and isotopic changes in a column experiment for degradation of TCE by zero-valent iron.  

PubMed

Zero-valent iron (ZVI) permeable-reactive barriers have become an increasingly used remediation option for the in situ removal of various organic and inorganic chemicals from contaminated groundwater. In the present study a process-based numerical model for the transport and reactions of chlorinated hydrocarbon in the presence of ZVI has been developed and applied to analyse a comprehensive data set from laboratory-scale flow-through experiments. The model formulation includes a reaction network for the individual sequential and/or parallel transformation of chlorinated hydrocarbons by ZVI, for the resulting geochemical changes such as mineral precipitation, and for the carbon isotope fractionation that occurs during each of the transformation reactions of the organic compounds. The isotopic fractionation was modelled by formulating separate reaction networks for lighter ((12)C) and heavier ((13)C) isotopes. The simulation of a column experiment involving the parallel degradation of TCE by hydrogenolysis and beta-elimination can conclusively reproduce the observed concentration profiles of all collected organic and inorganic data as well as the observed carbon isotope ratios of TCE and its daughter products. PMID:18267347

Prommer, Henning; Aziz, Lidia H; Bolaño, Nerea; Taubald, Heinrich; Schüth, Christoph

2008-04-01

265

Modelling of geochemical and isotopic changes in a column experiment for degradation of TCE by zero-valent iron  

NASA Astrophysics Data System (ADS)

Zero-valent iron (ZVI) permeable-reactive barriers have become an increasingly used remediation option for the in situ removal of various organic and inorganic chemicals from contaminated groundwater. In the present study a process-based numerical model for the transport and reactions of chlorinated hydrocarbon in the presence of ZVI has been developed and applied to analyse a comprehensive data set from laboratory-scale flow-through experiments. The model formulation includes a reaction network for the individual sequential and/or parallel transformation of chlorinated hydrocarbons by ZVI, for the resulting geochemical changes such as mineral precipitation, and for the carbon isotope fractionation that occurs during each of the transformation reactions of the organic compounds. The isotopic fractionation was modelled by formulating separate reaction networks for lighter ( 12C) and heavier ( 13C) isotopes. The simulation of a column experiment involving the parallel degradation of TCE by hydrogenolysis and ?-elimination can conclusively reproduce the observed concentration profiles of all collected organic and inorganic data as well as the observed carbon isotope ratios of TCE and its daughter products.

Prommer, Henning; Aziz, Lidia H.; Bolaño, Nerea; Taubald, Heinrich; Schüth, Christoph

2008-04-01

266

In situ redox manipulation of subsurface sediments from Fort Lewis, Washington: Iron reduction and TCE dechlorination mechanisms  

SciTech Connect

Pacific Northwest National Laboratory (PNNL) conducted a bench-scale study to determine how effective chemically treated Ft. Lewis sediments can degrade trichloroethylene (TCE). The objectives of this experimental study were to quantify: (1) sediment reduction and oxidation reactions, (2) TCE degradation reactions, and (3) other significant geochemical changes that occurred. Sediment reduction and oxidation were investigated to determine the mass of reducible iron in the Ft. Lewis sediments and the rate of this reduction and subsequent oxidation at different temperatures. The temperature dependence was needed to be able to predict field-scale reduction in the relatively cold ({approximately}11 C) Ft. Lewis aquifer. Results of these experiments were used in conjunction with other geochemical and hydraulic characterization to design the field-scale injection experiment and predict barrier longevity. For example, the sediment reduction rate controls the amount of time required for the dithionite solution to fully react with sediments. Sediment oxidation experiments were additionally conducted to determine the oxidation rate and provide a separate measure of the mass of reduced iron. Laboratory experiments that were used to meet these objectives included: (1) sediment reduction in batch (static) systems, (2) sediment reduction in 1-D columns, and (3) sediment oxidation in 1-D columns. Multiple reaction modeling was conducted to quantify the reactant masses and reaction rates.

JE Szecsody; JS Fruchter; DS Sklarew; JC Evans

2000-03-21

267

Heterogeneous carbonaceous matter in sedimentary rock lithocomponents causes significant trichloroethylene (TCE) sorption in a low organic carbon content aquifer/aquitard system.  

PubMed

This study evaluated the effects of heterogeneous thermally altered carbonaceous matter (CM) on trichloroethylene (TCE) sorption for a low fraction organic carbon content (foc) alluvial sedimentary aquifer and aquitard system (foc=0.046-0.105%). The equilibrium TCE sorption isotherms were highly nonlinear with Freundlich exponents of 0.46-0.58. Kerogen+black carbon was the dominant CM fraction extracted from the sediments and accounted for >60% and 99% of the total in the sands and silt, respectively. Organic petrological examination determined that the kerogen included abundant amorphous organic matter (bituminite), likely of marine origin. The dark calcareous siltstone exhibited the greatest TCE sorption among aquifer lithocomponents and accounted for most sorption in the aquifer. The results suggest that the source of the thermally altered CM, which causes nonlinear sorption, was derived from parent Paleozoic marine carbonate rocks that outcrop throughout much of New York State. A synthetic aquifer-aquitard unit system (10% aquitard) was used to illustrate the effect of the observed nonlinear sorption on mass storage potential at equilibrium. The calculation showed that >80% of TCE mass contained in the aquifer was sorbed on the aquifer sediment at aqueous concentration <1000 ?gL(-1). These results show that sorption is likely a significant contributor to the persistence of a TCE groundwater plume in the aquifer studied. It is implied that sorption may similarly contribute to TCE persistence in other glacial alluvial aquifers with similar geologic characteristics, i.e., comprised of sedimentary rock lithocomponents that contain thermally altered CM. PMID:25168960

Choung, Sungwook; Zimmerman, Lisa R; Allen-King, Richelle M; Ligouis, Bertrand; Feenstra, Stanley

2014-10-15

268

Degradation of multi-DNAPLs by a UV/persulphate/ethanol system with the additional injection of a base solution.  

PubMed

This study was conducted to investigate the inhibited influences on and solution to the degradation of four types of dense non-aqueous phase liquids (DNAPLs) (i.e. perchloroethylene [PCE], trichloroethylene [TCE], chloroform [CF], and carbon tetrachloride [CT]) all at the same instance in groundwater (GW). Degradations of DNAPLs in de-ionized water (DW) and GW were carried out by applying an ultraviolet radiation-activated persulphate (UV/PS) system. PCE and TCE were degraded by over 90% and CT was only degraded by 25% in both DW and GW. However, CF was degraded by over 90% in DW, while it was only degraded by 50% in GW. First of all, degradations with an inorganic anion (either Cl(-) or [Formula: see text]) indicated that the lower degradation of CF in GW was caused by the existence of the chloride ion. Moreover, the low CF degradation in GW was overcome by the additional injection of a base solution (sodium hydroxide [NaOH]) into the UV/PS system. The results showed that PCE, TCE, and CF were degraded by over 90%, respectively, when a molar ratio of [base]0:[PS]0 was larger than 0.5:1, but CT was still not effectively degraded in the UV/PS system. To achieve effective CT degradation, UV/PS with the ethanol (EtOH) system was evaluated and it was found that it degraded CT over 90%. However, at this time, CF was not effectively degraded in the UV/PS/EtOH system. Finally, degradations of DNAPLs in the UV/PS/EtOH system with the additional injection of a base solution were conducted and it showed that multi-DNAPLs were degraded by over 90%, respectively, when the molar ratio of [PS]0:[EtOH]0:[base]0 was 1:1:3. PMID:25342163

Jung, Jae-Gu; Do, Si-Hyun; Kwon, Yong-Jae; Kong, Sung-Ho

2015-04-01

269

Time series geophysical monitoring of permanganate injections and in situ chemical oxidation of PCE, OU1 area, Savage Superfund Site, Milford, NH, USA.  

PubMed

In situ chemical oxidation (ISCO) treatment with sodium permanganate, an electrically conductive oxidant, provides a strong electrical signal for tracking of injectate transport using time series geophysical surveys including direct current (DC) resistivity and electromagnetic (EM) methods. Effective remediation is dependent upon placing the oxidant in close contact with the contaminated aquifer. Therefore, monitoring tools that provide enhanced tracking capability of the injectate offer considerable benefit to guide subsequent ISCO injections. Time-series geophysical surveys were performed at a superfund site in New Hampshire, USA over a one-year period to identify temporal changes in the bulk electrical conductivity of a tetrachloroethylene (PCE; also called tetrachloroethene) contaminated, glacially deposited aquifer due to the injection of sodium permanganate. The ISCO treatment involved a series of pulse injections of sodium permanganate from multiple injection wells within a contained area of the aquifer. After the initial injection, the permanganate was allowed to disperse under ambient groundwater velocities. Time series geophysical surveys identified the downward sinking and pooling of the sodium permanganate atop of the underlying till or bedrock surface caused by density-driven flow, and the limited horizontal spread of the sodium permanganate in the shallow parts of the aquifer during this injection period. When coupled with conventional monitoring, the surveys allowed for an assessment of ISCO treatment effectiveness in targeting the PCE plume and helped target areas for subsequent treatment. PMID:22459605

Harte, Philip T; Smith, Thor E; Williams, John H; Degnan, James R

2012-05-01

270

Desulfitobacterium sp. strain PCE1, an anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene or ortho-chlorinated phenols.  

PubMed

A strictly anaerobic bacterium, strain PCE1, was isolated from a tetrachloroethene-dechlorinating enrichment culture. Cells of the bacterium were motile curved rods, with approximately four lateral flagella. They possessed a gram-positive type of cell wall and contained cytochrome c. Optimum growth occurred at pH 7.2-7.8 and 34-38 degrees C. The organism grew with L-lactate, pyruvate, butyrate, formate, succinate, or ethanol as electron donors, using either tetrachloroethene, 2-chlorophenol, 2,4,6-trichlorophenol, 3-chloro-4-hydroxy-phenylacetate, sulfite, thiosulfate, or fumarate as electron acceptors. Strain PCE1 also grew fermentatively with pyruvate as the sole substrate. L-Lactate and pyruvate were oxidized to acetate. Tetrachloroethene was reductively dechlorinated to trichloroethene and small amounts ( 5%) of cis-1,2-dichloroethene and trans-1,2-dichloroethene. Chlorinated phenolic compounds were dechlorinated specifically at the ortho-position. On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulfitobacterium dehalogenans. PMID:8593100

Gerritse, J; Renard, V; Pedro Gomes, T M; Lawson, P A; Collins, M D; Gottschal, J C

1996-02-01

271

Time series geophysical monitoring of permanganate injections and in situ chemical oxidation of PCE, OU1 area, Savage Superfund Site, Milford, NH, USA  

USGS Publications Warehouse

In situ chemical oxidation (ISCO) treatment with sodium permanganate, an electrically conductive oxidant, provides a strong electrical signal for tracking of injectate transport using time series geophysical surveys including direct current (DC) resistivity and electromagnetic (EM) methods. Effective remediation is dependent upon placing the oxidant in close contact with the contaminated aquifer. Therefore, monitoring tools that provide enhanced tracking capability of the injectate offer considerable benefit to guide subsequent ISCO injections. Time-series geophysical surveys were performed at a superfund site in New Hampshire, USA over a one-year period to identify temporal changes in the bulk electrical conductivity of a tetrachloroethylene (PCE; also called tetrachloroethene) contaminated, glacially deposited aquifer due to the injection of sodium permanganate. The ISCO treatment involved a series of pulse injections of sodium permanganate from multiple injection wells within a contained area of the aquifer. After the initial injection, the permanganate was allowed to disperse under ambient groundwater velocities. Time series geophysical surveys identified the downward sinking and pooling of the sodium permanganate atop of the underlying till or bedrock surface caused by density-driven flow, and the limited horizontal spread of the sodium permanganate in the shallow parts of the aquifer during this injection period. When coupled with conventional monitoring, the surveys allowed for an assessment of ISCO treatment effectiveness in targeting the PCE plume and helped target areas for subsequent treatment.

Harte, Philip T.; Smith, Thor E.; Williams, John H.; Degnan, James R.

2012-01-01

272

Time series geophysical monitoring of permanganate injections and in situ chemical oxidation of PCE, OU1 area, Savage Superfund Site, Milford, NH, USA  

NASA Astrophysics Data System (ADS)

In situ chemical oxidation (ISCO) treatment with sodium permanganate, an electrically conductive oxidant, provides a strong electrical signal for tracking of injectate transport using time series geophysical surveys including direct current (DC) resistivity and electromagnetic (EM) methods. Effective remediation is dependent upon placing the oxidant in close contact with the contaminated aquifer. Therefore, monitoring tools that provide enhanced tracking capability of the injectate offer considerable benefit to guide subsequent ISCO injections. Time-series geophysical surveys were performed at a superfund site in New Hampshire, USA over a one-year period to identify temporal changes in the bulk electrical conductivity of a tetrachloroethylene (PCE; also called tetrachloroethene) contaminated, glacially deposited aquifer due to the injection of sodium permanganate. The ISCO treatment involved a series of pulse injections of sodium permanganate from multiple injection wells within a contained area of the aquifer. After the initial injection, the permanganate was allowed to disperse under ambient groundwater velocities. Time series geophysical surveys identified the downward sinking and pooling of the sodium permanganate atop of the underlying till or bedrock surface caused by density-driven flow, and the limited horizontal spread of the sodium permanganate in the shallow parts of the aquifer during this injection period. When coupled with conventional monitoring, the surveys allowed for an assessment of ISCO treatment effectiveness in targeting the PCE plume and helped target areas for subsequent treatment.

Harte, Philip T.; Smith, Thor E.; Williams, John H.; Degnan, James R.

2012-05-01

273

Investigation of the potential source area, contamination pathway, and probable release history of chlorinated-solvent-contaminated groundwater at the Capital City Plume Site, Montgomery, Alabama, 2008-2010  

USGS Publications Warehouse

Detection of the organic solvent perchloroethylene (PCE) in a shallow public-supply well in 1991 and exposure of workers in 1993 to solvent vapors during excavation activities to depths near the water table provided evidence that the shallow aquifer beneath the capital city of Montgomery, Alabama, was contaminated. Investigations conducted from 1993 to 1999 by State and Federal agencies confirmed the detection of PCE in the shallow aquifer, as well as the detection of the organic solvent trichloroethylene (TCE) and various inorganic compounds, but the source of the groundwater contamination was not determined. In May 2000 the U.S. Environmental Protection Agency proposed that the site, called the Capital City Plume (CCP) Site, be a candidate for the National Priorities List. Between 2000 and 2007, numerous site-investigation activities also did not determine the source of the groundwater contamination. In 2008, additional assessments were conducted at the CCP Site to investigate the potential source area, contamination pathway, and the probable release history of the chlorinated-solvent-contaminated groundwater. The assessments included the collection of (1) pore water in 2008 from the hyporheic zone of a creek using passive-diffusion bag samplers; (2) tissue samples in 2008 and 2009 from trees growing in areas of downtown Montgomery characterized by groundwater contamination and from trees growing in riparian zones along the Alabama River and Cypress Creek; and (3) groundwater samples in 2009 and 2010. The data collected were used to investigate the potential source area of contaminants detected in groundwater, the pathway of groundwater contamination, and constraints on the probable contaminant-release history. The data collected between 2008 and 2010 indicate that the PCE and TCE contamination of the shallow aquifer beneath the CCP Site most likely resulted from the past use and disposal of industrial wastewater from printing operations containing chlorinated solvents into the sanitary sewer and (or) stormwater systems of Montgomery. Moreover, chlorinated-solvent use and disposal occurred at least between the 1940s and 1970s at several locations occupied by printing operations. The data also indicate that PCE and TCE contamination continues to occur in the shallow subsurface near potential release areas and that PCE and TCE have been transported to the intermediate part of the shallow aquifer.

Landmeyer, James E.; Miller, Scott; Campbell, Bruce G.; Vroblesky, Don A.; Gill, Amy C.; Clark, Athena P.

2011-01-01

274

Plume persistence caused by back diffusion from thin clay layers in a sand aquifer following TCE source-zone hydraulic isolation  

Microsoft Academic Search

This paper concludes that back diffusion from one or a few thin clayey beds in a sand aquifer can cause contaminant persistence above MCLs in a sand aquifer long after the source zone initially causing the plume is isolated or removed. This conclusion is based on an intensive case study of a TCE contaminated site in Florida, with the processes

Beth L. Parker; Steven W. Chapman; Martin A. Guilbeault

2008-01-01

275

A three-electrode column for Pd-catalytic oxidation of TCE in groundwater with automatic pH-regulation and resistance to reduced sulfur compound foiling.  

PubMed

A hybrid electrolysis and Pd-catalytic oxidation process is evaluated for degradation of trichloroethylene (TCE) in groundwater. A three-electrode, one anode and two cathodes, column is employed to automatically develop a low pH condition in the Pd vicinity and a neutral effluent. Simulated groundwater containing up to 5 mM bicarbonate can be acidified to below pH 4 in the Pd vicinity using a total of 60 mA with 20 mA passing through the third electrode. By packing 2 g of Pd/Al(2)O(3) pellets in the developed acidic region, the column efficiency for TCE oxidation in simulated groundwater (5.3 mg/L TCE) increases from 44 to 59 and 68% with increasing Fe(II) concentration from 0 to 5 and 10 mg/L, respectively. Different from Pd-catalytic hydrodechlorination under reducing conditions, this hybrid electrolysis and Pd-catalytic oxidation process is advantageous in controlling the fouling caused by reduced sulfur compounds (RSCs) because the in situ generated reactive oxidizing species, i.e., O(2), H(2)O(2) and OH, can oxidize RSCs to some extent. In particular, sulfite at concentrations less than 1 mM even greatly increases TCE oxidation by the production of SO(4)(•-), a strong oxidizing radical, and more OH. PMID:23121896

Yuan, Songhu; Chen, Mingjie; Mao, Xuhui; Alshawabkeh, Akram N

2013-01-01

276

A Three-electrode Column for Pd-Catalytic Oxidation of TCE in Groundwater with Automatic pH-regulation and Resistance to Reduced Sulfur Compound Foiling  

PubMed Central

A hybrid electrolysis and Pd-catalytic oxidation process is evaluated for degradation of trichloroethylene (TCE) in groundwater. A three-electrode, one anode and two cathodes, column is employed to automatically develop a low pH condition in the Pd vicinity and a neutral effluent. Simulated groundwater containing up to 5 mM bicarbonate can be acidified to below pH 4 in the Pd vicinity using a total of 60 mA with 20 mA passing through the third electrode. By packing 2 g of Pd/Al2O3 pellets in the developed acidic region, the column efficiency for TCE oxidation in simulated groundwater (5.3 mg/L TCE) increases from 44 to 59 and 68% with increasing Fe(II) concentration from 0 to 5 and 10 mg/L, respectively. Different from Pd-catalytic hydrodechlorination under reducing conditions, this hybrid electrolysis and Pd-catalytic oxidation process is advantageous in controlling the fouling caused by reduced sulfur compounds (RSCs) because the in situ generated reactive oxidizing species, i.e., O2, H2O2 and •OH, can oxidize RSCs to some extent. In particular, sulfite at concentrations less than 1 mM even greatly increases TCE oxidation by the production of SO4•?, a strong oxidizing radical, and more •OH. PMID:23121896

Yuan, Songhu; Chen, Mingjie; Mao, Xuhui; Alshawabkeh, Akram N.

2013-01-01

277

Application of a long-lasting colloidal substrate with pH and hydrogen sulfide control capabilities to remediate TCE-contaminated groundwater.  

PubMed

A long-lasting emulsified colloidal substrate (LECS) was developed for continuous carbon and nanoscale zero-valent iron (nZVI) release to remediate trichloroethylene (TCE)-contaminated groundwater under reductive dechlorinating conditions. The developed LECS contained nZVI, vegetable oil, surfactants (Simple Green™ and lecithin), molasses, lactate, and minerals. An emulsification study was performed to evaluate the globule droplet size and stability of LECS. The results show that a stable oil-in-water emulsion with uniformly small droplets (0.7 ?m) was produced, which could continuously release the primary substrates. The emulsified solution could serve as the dispensing agent, and nZVI particles (with diameter 100-200 nm) were distributed in the emulsion evenly without aggregation. Microcosm results showed that the LECS caused a rapid increase in the total organic carbon concentration (up to 488 mg/L), and reductive dechlorination of TCE was significantly enhanced. Up to 99% of TCE (with initial concentration of 7.4 mg/L) was removed after 130 days of operation. Acidification was prevented by the production of hydroxide ion by the oxidation of nZVI. The formation of iron sulfide reduced the odor from produced hydrogen sulfide. Microbial analyses reveal that dechlorinating bacteria existed in soils, which might contribute to TCE dechlorination. PMID:25463237

Sheu, Y T; Chen, S C; Chien, C C; Chen, C C; Kao, C M

2015-03-01

278

Geochemistry of a Tetrachloroethene and Trichloroethene Plume at the Borden Aquifer  

Microsoft Academic Search

Under favourable redox conditions biodegradation is one of the processes that controls PCE and TCE attenuation at the Borden sand aquifer. This paper presents geochemistry data obtained in a study which main aim is to evaluate the fate of a PCE and TCE plume in the Borden forested area. Selected multilevel piezometers for five transects in a Tetrachloroethene (PCE) and

I. Vargas; R. Aravena; B. Parker; L. Wassenaar

2004-01-01

279

Demonstration of low latency Intra/Inter Data-Centre heterogeneous optical sub-wavelength network using extended GMPLS-PCE control-plane.  

PubMed

This paper reports on the first user/application-driven multi-technology optical sub-wavelength network for intra/inter Data-Centre (DC) communications. Two DCs each with distinct sub-wavelength switching technologies, frame based synchronous TSON and packet based asynchronous OPST are interconnected by a WSON inter-DC communication. The intra/inter DC testbed demonstrates ultra-low latency (packet-delay <270 µs and packet-delay-variation (PDV)<10 µs) flexible data-rate traffic transfer by point-to-point, point-to-multipoint, and multipoint-to-(multi)point connectivity, highly suitable for cloud based applications and high performance computing (HPC). The extended GMPLS-PCE-SLAE based control-plane enables innovative application-driven end-to-end sub-wavelength path setup and resource reservation across the multi technology data-plane, which has been assessed for as many as 25 concurrent requests. PMID:23482117

Rofoee, Bijan Rahimzadeh; Zervas, Georgios; Yan, Yan; Simeonidou, Dimitra; Bernini, Giacomo; Carrozzo, Gino; Ciulli, Nicola; Levins, John; Basham, Mark; Dunne, John; Georgiades, Michael; Belovidov, Alexander; Andreou, Lenos; Sanchez, David; Aracil, Javier; Lopez, Victor; Fernández-Palacios, Juan P

2013-03-11

280

MICROSCOPIC OBSERVATION AND QUANTIFICATION OF ENHANCED DNAPL REMOVAL BY COSOLVENT-AIR FLOODING  

EPA Science Inventory

The simultaneous injection of cosolvent and air has been suggested to improve sweep efficiency of cosolvent flooding for dense nonaqueous phase liquid (DNAPL) remediation. Glass micromodel experiments were conducted to investigate the factors that influence perchloroethylene (PCE...

281

Persulfate oxidation for in situ remediation of TCE. I. Activated by ferrous ion with and without a persulfate–thiosulfate redox couple  

Microsoft Academic Search

The objective of the laboratory study is to examine the conditions under which transition metal ions (e.g., ferrous ion, Fe2+) could activate the persulfate anion (S2O82?) to produce a powerful oxidant known as the sulfate free radical (SO4?) with a standard redox potential of 2.6 V. The SO4? is capable of destroying groundwater contaminants in situ such as trichloroethylene (TCE).

Chenju Liang; Clifford J. Bruell; Michael C. Marley; Kenneth L. Sperry

2004-01-01

282

Manganese valence in oxides formed from in situ chemical oxidation of TCE by KMnO4.  

PubMed

Batch and column experiments designed to simulate in situ chemical oxidation (ISCO) in a sand aquifer were conducted to create Mn-oxides (MnOx) by oxidation of trichloroethylene (TCE) with permanganate (MnO4-). Electron energy-loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) were used to quantify Mn valence in the oxides. The valence of Mn in the MnOx generated in near-source ISCO conditions was 2.2 and 2.3 when formed at low (<3) and neutral (6-7) pH conditions, respectively. There is no significant difference between these values. Valence was found to be sensitive to the preparation method and to aging. When formed in the presence of excess MnO4-, or aged for 3 months, Mn valence ranged from 2.5 to 3.6. Aging in a lower pH environment inhibited Mn oxidation. The EELS and XPS methods provided similar results, but there was a slight bias to higher values for XPS. This work demonstrates that MnO2(s) may not be the main product of MnO4- reaction with chlorinated solvents as is commonly assumed and that the efficiency of ISCO treatment may be greater than previously known. PMID:20617842

Loomer, Diana B; Al, Tom A; Banks, Vernon J; Parker, Beth L; Mayer, K Ulrich

2010-08-01

283

Localized Plasticity in the Streamlined Genomes of Vinyl Chloride Respiring Dehalococcoides  

E-print Network

VC), a human carcinogen and abundant groundwater pollutant.carcinogen [1] – and other chloroethenes, such as trichloroethene (TCE) and tetrachloroethene (PCE), are among the most frequently detected groundwater

McMurdie, Paul J.

2010-01-01

284

Efficient Degradation of TCE in Groundwater Using Pd and Electro-generated H2 and O2: A Shift in Pathway from Hydrodechlorination to Oxidation in the Presence of Ferrous Ions  

PubMed Central

Degradation of trichloroethylene (TCE) in simulated groundwater by Pd and electro-generated H2 and O2 is investigated in the absence and presence of Fe(II). In the absence of Fe(II), hydrodechlorination dominates TCE degradation, with accumulation of H2O2 up to 17 mg/L. Under weak acidity, low concentrations of oxidizing •OH radical are detected due to decomposition of H2O2, slightly contributing to TCE degradation via oxidation. In the presence of Fe(II), the degradation efficiency of TCE at 396 ?M improves to 94.9% within 80 min. The product distribution proves that the degradation pathway shifts from 79% hydrodechlorination in the absence of Fe(II) to 84% •OH oxidation in the presence of Fe(II). TCE degradation follows zeroth-order kinetics with rate constants increasing from 2.0 to 4.6 ?M/min with increasing initial Fe(II) concentration from 0 to 27.3 mg/L at pH 4. A good correlation between TCE degradation rate constants and •OH generation rate constants confirms that •OH is the predominant reactive species for TCE oxidation. Presence of 10 mM Na2SO4, NaCl, NaNO3, NaHCO3, K2SO4, CaSO4 and MgSO4 does not significantly influence degradation, but sulfite and sulfide greatly enhance and slightly suppresses degradation, respectively. A novel Pd-based electrochemical process is proposed for groundwater remediation. PMID:22315993

Yuan, Songhu; Mao, Xuhui; Alshawabkeh, Akram N.

2012-01-01

285

Plume persistence caused by back diffusion from thin clay layers in a sand aquifer following TCE source-zone hydraulic isolation  

NASA Astrophysics Data System (ADS)

This paper concludes that back diffusion from one or a few thin clayey beds in a sand aquifer can cause contaminant persistence above MCLs in a sand aquifer long after the source zone initially causing the plume is isolated or removed. This conclusion is based on an intensive case study of a TCE contaminated site in Florida, with the processes evaluated using numerical modeling. At this site, the TCE DNAPL zone formed decades ago, and was hydraulically isolated by means of an innovative system performing groundwater extraction, treatment and re-injection. Treated water is re-injected in a row of injection wells situated a short distance downgradient of the extraction wells, creating a clean-water displacement front to efficiently flush the downgradient plume. This scheme avoids the creation of stagnation zones typical of most groundwater pump-and-treat systems, thereby minimizing the time for aquifer flushing and therefore downgradient cleanup. The system began operation in August 2002 and although the performance monitoring shows substantial declines in concentrations, detectable levels of TCE and degradation products persist downgradient of the re-injection wells, long after the TCE should have disappeared based on calculations assuming a nearly homogenous sand aquifer. Three hypotheses were assessed for this plume persistence: 1) incomplete source-zone capture, 2) DNAPL occurrence downgradient of the re-injection wells, and 3) back diffusion from one or more thin clay beds in the aquifer. After careful consideration, the first two hypotheses were eliminated, leaving back diffusion as the only plausible hypothesis, supported by detailed measurements of VOC concentrations within and near the clay beds and also by numerical model simulations that closely represent the field site hydrogeologic conditions. The model was also used to simulate a more generalized, hypothetical situation where more thin clayey beds occur in a sand aquifer with an underlying aquitard. While there is no doubt that DNAPL source mass reduction can eventually improve downgradient groundwater quality, the magnitude and time scale over which the improvement occurs is the major uncertainty given current characterization approaches. This study shows that even one thin clay bed, less than 0.2 m thick, can cause plume persistence due to back diffusion for several years or even decades after the flux from the source is completely isolated. Thin clay beds, which have a large storage capacity for dissolved and sorbed contaminant mass, are common in many types of sandy aquifers. However, without careful inspection of continuous cores and sampling, such thin clay beds, and their potential for causing long-term back-diffusion effects, can easily go unnoticed during site characterization.

Parker, Beth L.; Chapman, Steven W.; Guilbeault, Martin A.

2008-11-01

286

Plume persistence caused by back diffusion from thin clay layers in a sand aquifer following TCE source-zone hydraulic isolation.  

PubMed

This paper concludes that back diffusion from one or a few thin clayey beds in a sand aquifer can cause contaminant persistence above MCLs in a sand aquifer long after the source zone initially causing the plume is isolated or removed. This conclusion is based on an intensive case study of a TCE contaminated site in Florida, with the processes evaluated using numerical modeling. At this site, the TCE DNAPL zone formed decades ago, and was hydraulically isolated by means of an innovative system performing groundwater extraction, treatment and re-injection. Treated water is re-injected in a row of injection wells situated a short distance downgradient of the extraction wells, creating a clean-water displacement front to efficiently flush the downgradient plume. This scheme avoids the creation of stagnation zones typical of most groundwater pump-and-treat systems, thereby minimizing the time for aquifer flushing and therefore downgradient cleanup. The system began operation in August 2002 and although the performance monitoring shows substantial declines in concentrations, detectable levels of TCE and degradation products persist downgradient of the re-injection wells, long after the TCE should have disappeared based on calculations assuming a nearly homogenous sand aquifer. Three hypotheses were assessed for this plume persistence: 1) incomplete source-zone capture, 2) DNAPL occurrence downgradient of the re-injection wells, and 3) back diffusion from one or more thin clay beds in the aquifer. After careful consideration, the first two hypotheses were eliminated, leaving back diffusion as the only plausible hypothesis, supported by detailed measurements of VOC concentrations within and near the clay beds and also by numerical model simulations that closely represent the field site hydrogeologic conditions. The model was also used to simulate a more generalized, hypothetical situation where more thin clayey beds occur in a sand aquifer with an underlying aquitard. While there is no doubt that DNAPL source mass reduction can eventually improve downgradient groundwater quality, the magnitude and time scale over which the improvement occurs is the major uncertainty given current characterization approaches. This study shows that even one thin clay bed, less than 0.2 m thick, can cause plume persistence due to back diffusion for several years or even decades after the flux from the source is completely isolated. Thin clay beds, which have a large storage capacity for dissolved and sorbed contaminant mass, are common in many types of sandy aquifers. However, without careful inspection of continuous cores and sampling, such thin clay beds, and their potential for causing long-term back-diffusion effects, can easily go unnoticed during site characterization. PMID:18775583

Parker, Beth L; Chapman, Steven W; Guilbeault, Martin A

2008-11-14

287

Depression of calcium dynamics in cardiac myocytes--a common mechanism of halogenated hydrocarbon anesthetics and solvents.  

PubMed

Individual halogenated hydrocarbons (HC) have recently been demonstrated to depress Ca2+ dynamics in cardiomyocytes during excitation-contraction coupling. In the present study, eight widely used HC were systematically compared for their effects on Ca2+ dynamics in neonatal rat cardiomyocytes by means of spectrofluorometric analysis of fura-2-Ca(2+)-binding. Cells were exposed to dichloromethane (DCM), dichloroethane (DCE), 1,1,2-trichloroethane (112-TCE), trichloroethylene (TRI), halothane (HAL), 1,1,1-trichloroethane (111-TCE), perchloroethylene (PER), or pentachlorethane (PCE) in an environmentally controlled chamber. All HC tested decreased the height of electrically induced cytosolic free Ca2+ ([Ca2+]i) transients in a concentration-dependent and reversible manner (IC50 0.15-18.06 mM) without significant effects on diastolic [Ca2+]i. The increase in [Ca2+]i induced by depolarization with 90 mM KCl was inhibited to a lesser degree. Investigations with thapsigargin (100 nM) and ryanodine (1 microM)-inhibitors of Ca2+ release from the sarcoplasmic reticulum-provided evidence that the tonic Ca2+ response after KCl depolarization depends mainly on sarcolemmal Ca2+ influx. The potency of the eight HC to inhibit Ca2+ dynamics in cardiomyocytes correlated with their octanol/water partition coefficients. Results support the hypothesis that alteration of Ca2+ dynamics in cardiomyocytes is a common mechanism of cardiotoxic HC actions. PMID:8072012

Hoffmann, P; Heinroth, K; Richards, D; Plews, P; Toraason, M

1994-05-01

288

Abstract Pseudomonas stutzeri OX1 naphthalene-oxi-dation activity is induced 3.0-fold by tetrachloroethylene  

E-print Network

(PCE) and trichloroethylene (TCE) are suspected carcinogens, regulated to levels of five parts per billion under the Safe Drinking Water Act. These compounds are the most common groundwater pollutants degradation of TCE and PCE (McCarty 1997); VC is a known human carcinogen (McCarty 1997) whereas both VC

Wood, Thomas K.

289

CROWTM PROCESS APPLICATION FOR SITES CONTAMINATED WITH LIGHT NON-AQUEOUS PHASE LIQUIDS AND CHLORINATED HYDROCARBONS  

SciTech Connect

Western Research Institute (WRI) has successfully applied the CROWTM (Contained Recovery of Oily Wastes) process at two former manufactured gas plants (MGPs), and a large wood treatment site. The three CROW process applications have all occurred at sites contaminated with coal tars or fuel oil and pentachlorophenol (PCP) mixtures, which are generally denser than water and are classified as dense non-aqueous phase liquids (DNAPLs). While these types of sites are abundant, there are also many sites contaminated with gasoline, diesel fuel, or fuel oil, which are lighter than water and lie on top of an aquifer. A third site type occurs where chlorinated hydrocarbons have contaminated the aquifer. Unlike the DNAPLs found at MGP and wood treatment sites, chlorinated hydrocarbons are approximately one and a half times more dense than water and have fairly low viscosities. These contaminants tend to accumulate very rapidly at the bottom of an aquifer. Trichloroethylene (TCE) and perchloroethylene, or tetrachloroethylene (PCE), are the major industrial chlorinated solvents that have been found contaminating soils and aquifers. The objective of this program was to demonstrate the effectiveness of applying the CROW process to sites contaminated with light non-aqueous phase liquids (LNAPLs) and chlorinated hydrocarbons. Individual objectives were to determine a range of operating conditions necessary to optimize LNAPL and chlorinated hydrocarbon recovery, to conduct numerical simulations to match the laboratory experiments and determine field-scale recoveries, and determine if chemical addition will increase the process efficiency for LNAPLs. The testing consisted of twelve TCE tests; eight tests with PCE, diesel, and wood treatment waste; and four tests with a fuel oil-diesel blend. Testing was conducted with both vertical and horizontal orientations and with ambient to 211 F (99 C) water or steam. Residual saturations for the horizontal tests ranged from 23.6% PV to 0.3% PV. Also conducted was screening of 13 chemicals to determine their relative effectiveness and the selection of three chemicals for further testing.

L.A. Johnson, Jr.

2003-06-30

290

Competitive Sorption and Desorption of Chlorinated Organic Solvents (DNAPLs) in Engineered Natural Organic Matter  

SciTech Connect

The effects of artificially accelerated geochemical condensation and maturation of natural organic matter on the sorption and desorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) were studied. The sorption and desorption of TCE in the presence and absence of the competing PCE and 1,2-dichlorobenzene (DCB) were also examined. A sphagnum peat comprising geologically young organic matter was artificially ''aged'' using superheated water, thus increasing the aromaticity and the degree of condensation of its associated organic matter. The sorption of all solutes tested were increased remarkably and their respective desorptions reduced, by the aged peat. The sorption capacities and isotherm nonlinearities of the peat for both TCE and PCE were found to increase as treatment temperature increased. In the competitive sorption studies, both PCE and DCB were found to depress TCE sorption, with PCE having greater effects than DCB, presumably because the molecular structure o f the former is more similar to that of TCE.

Tang, Jixin; Weber, Walter J., Jr.

2004-03-31

291

Field assessment of carboxymethyl cellulose stabilized iron nanoparticles for in situ destruction of chlorinated solvents in source zones.  

PubMed

This study pilot-tested carboxymethyl cellulose (CMC) stabilized zero-valent iron (ZVI) nanoparticles (with a trace amount of Pd catalyst) for in situ destruction of chlorinated ethenes such as perchloroethylene (PCE) and trichloroethylene (TCE) and polychlorinated biphenyls (PCBs) that had been in groundwater for decades. The test site was located in a well-characterized secondary source zone of PCBs and chlorinated ethenes. Four test wells were installed along the groundwater flow direction (spaced 5 ft apart), including one injection well (IW), one up-gradient monitoring well (MW-3) and two down-gradient monitoring wells (MW-1 and MW-2). Stabilized nanoparticle suspension was prepared on-site and injected into the 50-ft deep, unconfined aquifer. Approximately 150 gallons of 0.2 g/L Fe-Pd (CMC = 0.1 wt%, Pd/Fe = 0.1 wt%) was gravity-fed through IW-1 over a 4-h period (Injection #1). One month later, another 150 gallons of 1.0 g/L Fe-Pd (CMC = 0.6 wt%, Pd/Fe = 0.1 wt%) was injected into IW-1 at an injection pressure <5 psi (Injection #2). When benchmarked against the tracer, approximately 37.4% and 70.0% of the injected Fe was detected in MW-1 during injection #1 and #2, respectively, confirming the soil mobility of the nanoparticles through the aquifer, and higher mobility of the particles was observed when the injection was performed under higher pressure. Rapid degradation of PCE and TCE was observed in both MW-1 and MW-2 following each injection, with the maximum degradation being observed during the first week of the injections. The chlorinated ethenes concentrations gradually returned to their pre-injection levels after approximately 2 weeks, indicating exhaustion of the ZVI's reducing power. However, the injection of CMC-stabilized nanoparticle and the abiotic reductive dechlorination process appeared to have boosted a long-term in situ biological dechlorination thereafter, which was evidenced by the fact that PCE and TCE concentrations showed further reduction after two weeks. After 596 days from the first injection, the total chlorinated ethenes concentration decreased by about 40% and 61% in MW-1 and MW-2, respectively. No significant long-term reduction of PCB 1242 was observed in MW-1, but a reduction of 87% was evident in MW-2. During the 596 days of testing, the total concentrations of cis-DCE (dichloroethylene) and VC (vinyl chloride) decreased by 20% and 38% in MW-1 and MW-2, respectively. However, the combined fraction of cis-DCE and VC in the total chlorinated ethenes (PCE, TCE, cis-DCE and VC) increased from 73% to 98% and from 62% to 98%, respectively, which supports the notion that biological dechlorination of PCE and TCE was active. It is proposed that CMC-stabilized ZVI-Pd nanoparticles facilitated the early stage rapid abiotic degradation. Over the long run, the existing biological degradation process was boosted with CMC as the carbon source and hydrogen from the abiotic/biotic processes as the electron donor, resulting in the sustained enhanced destruction of the chlorinated organic chlorinated ethenes in the subsurface. PMID:20106501

He, Feng; Zhao, Dongye; Paul, Chris

2010-04-01

292

The Relationship between Multiple Myeloma and Occupational Exposure to Six Chlorinated Solvents  

PubMed Central

Objectives Few studies have examined whether exposure to chlorinated solvents is associated with increased risk of multiple myeloma (MM). Using occupational exposure information, we evaluated associations between the risk of MM and exposure to six chlorinated solvents: 1,1,1-trichloroethane (TCA), trichloroethylene (TCE), methylene chloride (DCM), perchloroethylene (PCE), carbon tetrachloride, and chloroform. Methods MM cases were identified through cancer registries and controls were identified in the general population. In-person interviews obtained lifetime occupational histories and additional information on jobs with likely solvent exposure. We reviewed each job and assigned exposure metrics of probability, frequency, intensity, and confidence using job-exposure matrices modified by job-specific questionnaire information. We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between MM and having ever been exposed to each, and any, chlorinated solvent and also analyzed whether associations varied by duration and cumulative exposure. We also considered all occupations that were given the lowest confidence scores as unexposed and repeated all analyses. Results Risk of MM was significantly elevated for subjects ever exposed to TCA (OR (95% CI): 1.8 (1.1–2.9)). Ever-exposure to TCE or DCM also entailed elevated, but not statistically significant, risks of MM; these became statistically significant when occupations that had low confidence scores were considered unexposed (TCE: 1.7 (1.0–2.7); DCM: 2.0 (1.2–3.2)). Increasing duration and cumulative exposure to TCE were associated with significantly increasing risk of MM when jobs given low confidence were considered unexposed. Increasing cumulative exposure to PCE was also associated with increasing MM risk. We observed non-significantly increased MM risks with exposure to chloroform; however, few subjects were exposed. Conclusions Evidence from this relatively large case-control study suggests that exposures to certain chlorinated solvents may be associated with increased incidence of MM; however, the study is limited by relatively low participation (52%) among controls. PMID:20833760

Gold, Laura S; Stewart, Patricia A; Milliken, Kevin; Purdue, Mark; Severson, Richard; Seixas, Noah; Blair, Aaron; Hartge, Patricia; Davis, Scott; De Roos, Anneclaire J

2011-01-01

293

HEALTH ASSESSMENT DOCUMENT FOR TETRACHLOROETHYLENE (PERCHLOROETHYLENE)  

EPA Science Inventory

Tetrachloroethylene (PERC) is believed to exert its adverse effects upon humans via metabolism by the liver. Concern that PERC is likely to be a human carcinogen is based upon the evidence of the National Cancer Institute bioassay, in which PERC induced a statistically significan...

294

Competition for sorption and degradation of chlorinated ethenes in batch zero-valent iron systems.  

PubMed

The sorption and degradation of the chlorinated ethenes tetrachloroethene (PCE, 5 mg L(-1)) and trichloroethene (TCE, 10 mg L(-1)) were investigated in zero-valent iron systems (ZVI, 100 g L(-1)) in the presence of compounds common to contaminated groundwater with varying physicochemical properties. The potential competitors were chlorinated ethenes, monocyclic aromatic hydrocarbons, and humic acids. The effect of a complex matrix was tested with landfill contaminated groundwater. Nonlinear Freundlich isotherms adequately described chloroethene sorption to ZVI. In the presence of the more hydrophobic PCE (5 mg L(-1)), TCE sorption and degradation decreased by 33% and 30%, respectively, while TCE (10 mg L(-1)) decreased PCE degradation by 30%. In the presence of nonreactive hydrophobic hydrocarbons (i.e., benzene, toluene, and m-xylene at 100 mg L(-1)), TCE and PCE sorption decreased by 73% and 55%, respectively. The presence of the hydrocarbons had no effect on TCE degradation and increased PCE reduction rates by 50%, suggesting that the displacement of the chloroethenes from the sorption sites by the aromatic hydrocarbons enhanced the degradation rates. Humic acids did not interfere significantly with chloroethene sorption or with TCE degradation but lowered PCE degradation kinetics by 36% when present at high concentrations (100 mg L(-1)). The landfill groundwater with an organic carbon content of 109 mg L(-1) C had no effect on chloroethene sorption but inhibited TCE and PCE degradation by 60% and 70%, respectively. PMID:15212263

Dries, Jan; Bastiaens, Leen; Springael, Dirk; Agathos, Spiros N; Diels, Ludo

2004-05-15

295

Desorption Behavior of Trichloroethene and Tetrachloroethene in U.S. Department of Energy Savannah River Site Unconfined Aquifer Sediments  

SciTech Connect

The DOE Savannah River Site (SRS) is evaluating the potential applicability of the monitored natural attenuation (MNA) process as a contributor to the understanding of the restoration of its unconfined groundwater aquifer known to be contaminated with the chlorinated hydrocarbon compounds trichloroethylene (TCE) and tetrachloroethylene (PCE). This report discusses the results from aqueous desorption experiments on SRS aquifer sediments from two different locations at the SRS (A/M Area; P-Area) with the objective of providing technically defensible TCE/PCE distribution coefficient (Kd) data and data on TCE/PCE reversible and irreversible sorption behavior needed for further MNA evaluation.

Riley, Robert G.; Szecsody, Jim E.; Mitroshkov, Alexandre V.; Brown, Christopher F.

2006-06-21

296

Decontamination systems information and research program. Quarterly technical progress report, October 1--December 31, 1992  

SciTech Connect

It is estimated that over 3700 hazardous waste sites are under the jurisdiction of the Department of Energy (DOE). These sites were primarily generated from 45 years worth of environmental pollution from the design and manufacture of nuclear materials and weapons, and contain numerous types of wastes including: (1) volatile, low-volatile and nonvolatile organics, (2) radionuclides (e.g., uranium, plutonium and cesium), (3) nonradioactive heavy metals (e.g., chromium, nickel, and lead), and (4) toxic chemicals. These contaminants affect several media including soils (saturated and unsaturated), groundwater, vegetation, and air. Numerous and diverse DOE hazardous waste sites can be enumerated from soils contaminated by organics such as trichloroethylene (TCE) and perchloroethylene (PCE) at the Savannah River site to biota and vegetation contaminated by radionuclides such as radiocesium and radiostrontium at the Oak Ridge site. Over the next 30 years, the Department of Energy (DOE) is committed to bringing all its facilities into compliance with applicable Federal, State, and local environmental laws and regulations. This clean-up task is quite complex involving numerous sites containing various radioactive, organic and inorganic contaminants. To perform this clean-up effort in the most efficient manner at each site will require that DOE managers have access to all available information on pertinent technologies; i.e., to aid in maximum technology transfer. The purpose of this effort is to systematically develop a databast of those currently available and emerging clean-up technologies.

Not Available

1993-01-01

297

Decontamination systems information and research program  

SciTech Connect

It is estimated that over 3700 hazardous waste sites are under the jurisdiction of the Department of Energy (DOE). These sites were primarily generated from 45 years worth of environmental pollution from the design and manufacture of nuclear materials and weapons, and contain numerous types of wastes including: (1) volatile, low-volatile and nonvolatile organics, (2) radionuclides (e.g., uranium, plutonium and cesium), (3) nonradioactive heavy metals (e.g., chromium, nickel, and lead), and (4) toxic chemicals. These contaminants affect several media including soils (saturated and unsaturated), groundwater, vegetation, and air. Numerous and diverse DOE hazardous waste sites can be enumerated from soils contaminated by organics such as trichloroethylene (TCE) and perchloroethylene (PCE) at the Savannah River site to biota and vegetation contaminated by radionuclides such as radiocesium and radiostrontium at the Oak Ridge site. Over the next 30 years, the Department of Energy (DOE) is committed to bringing all its facilities into compliance with applicable Federal, State, and local environmental laws and regulations. This clean-up task is quite complex involving numerous sites containing various radioactive, organic and inorganic contaminants. To perform this clean-up effort in the most efficient manner at each site will require that DOE managers have access to all available information on pertinent technologies; i.e., to aid in maximum technology transfer. The purpose of this effort is to systematically develop a databast of those currently available and emerging clean-up technologies.

Not Available

1993-01-01

298

SRS Data Report for Lynntech Soil Ozone Treatment Demonstration Adjacent to the 321-M Solvent Storage Tank Pad  

SciTech Connect

At large industrial sites like the A/M Area of the Savannah River Site (SRS), undissolved dense non-aqueous phase liquid (DNAPL) in soil and groundwater is the most significant barrier to successful clean up. DNAPL acts as a reservoir that will continue to generate contaminant levels far above remediation concentration goals well into the future. In an effort to achieve remediation goals and reduce future costs, the SRS DNAPL program is evaluating technologies that will recycle or destroy DNAPL. In situ oxidation is one class of DNAPL destruction technologies. A demonstration of this class of technologies was conducted at SRS in the winter of 1999 and spring of 2000 employing ozone as the oxidant. Lynntech Inc. through a Small Business Innovative Research grant partnered with the Savannah River Site to demonstrate their soil ozone treatment technology. The Savannah River Site provided the demonstration location and field support of the test. This demonstration involved treating a small vadose zone DNAPL plume in the A/M Area over a 29 day period. Approximately 2000 pounds of DNAPL (perchloroethylene [PCE] and trichloroethylene [TCE]) were removed through the soil vapor extraction unit (SVEU). Soil core data indicate that approximately 300 pounds of DNAPL were removed from the test site. This report documents the data collected by SRS personnel during the demonstration of Lynntech's Soil Ozone Treatment Technology.

Vangelas, K.M.

2000-08-29

299

Technology status report: Off-gas treatment technologies for chlorinated volatile organic compound air emissions  

SciTech Connect

The purpose of this document is to review technologies for treatment of air streams that contain chlorinated volatile organic compounds (CVOCS) and to describe a Department of Energy Office of Technology Development program that is planned to demonstrate innovative technologies for the abatement of CVOC emissions. This report describes the first phase of testing of off-gas treatment technologies. At least one more phase of testing is planned. Guidance for the preparation of this document was provided by a predecisional draft outline issued by the Department of Energy's Office of Technology Development. The report is intended to evaluate the technical and regulatory aspects, public acceptance, and estimated costs of technologies selected for development and testing. These technologies are compared to currently practiced or baseline methods for treatment of CVOC-laden airstreams. A brief overview is provided rather than detailed cost and data comparisons because many of these technologies have not yet been field tested. A description of other promising technologies for the treatment of CVOC emissions is also included. Trichloroethylene (TCE) and perchloroethylene (PCE) were used for industrial cleaning and solvent applications for several decades. These chemicals can be classified as CVOCS. As a result of past standard disposal practices, these types of compounds are persistent groundwater and soil contaminants throughout the United States and the Department of Energy Complex.

Rossabi, J.; Haselow, J.S.

1992-04-15

300

Technology status report: Off-gas treatment technologies for chlorinated volatile organic compound air emissions  

SciTech Connect

The purpose of this document is to review technologies for treatment of air streams that contain chlorinated volatile organic compounds (CVOCS) and to describe a Department of Energy Office of Technology Development program that is planned to demonstrate innovative technologies for the abatement of CVOC emissions. This report describes the first phase of testing of off-gas treatment technologies. At least one more phase of testing is planned. Guidance for the preparation of this document was provided by a predecisional draft outline issued by the Department of Energy`s Office of Technology Development. The report is intended to evaluate the technical and regulatory aspects, public acceptance, and estimated costs of technologies selected for development and testing. These technologies are compared to currently practiced or baseline methods for treatment of CVOC-laden airstreams. A brief overview is provided rather than detailed cost and data comparisons because many of these technologies have not yet been field tested. A description of other promising technologies for the treatment of CVOC emissions is also included. Trichloroethylene (TCE) and perchloroethylene (PCE) were used for industrial cleaning and solvent applications for several decades. These chemicals can be classified as CVOCS. As a result of past standard disposal practices, these types of compounds are persistent groundwater and soil contaminants throughout the United States and the Department of Energy Complex.

Rossabi, J.; Haselow, J.S.

1992-04-15

301

Sensitive and Specific In-Situ Sensor for Monitoring Contaminated Water  

SciTech Connect

We report on the development of a high-sensitivity and high-specificity sensor, combining membrane extraction, pre-concentration, and gas-chromatographic differential mobility spectrometry (GC/DMS), for in situ detection of chlorinated hydrocarbons in water. Direct in-situ detection was achieved by membrane conversion of aqueous analyte to vapor, followed by vapor spectroscopy using GC/DMS analyzer. The limit of detection (LOD) reaches 0.37 parts per billion in volume (ppbv), or 0.54 ug/L, for aqueous trichloroethylene (TCE) and 1.6 ug/L for perchloroethylene (PCE) by incorporating a preconcentrator between the membrane extraction and GC/DMS detection systems. The high specificity was achieved using two-dimensional separation parameters of GC retention time and DMS compensation voltage. The presence of co-contaminants and foreign contaminants, such as benzene, toluene, CCl4, and CHCl3 did not interfere with the identification of chlorinated hydrocarbons. This highly-sensitive and -specific sensor paves the way for developing field-deployable sensors for in-situ and real-time monitoring of chlorinated hydrocarbons in groundwater and surface water.

Du, Yongzhai [ORNL] [ORNL; Watson, David B [ORNL] [ORNL; Whitten, William B [ORNL] [ORNL; Li, Haiyang [ORNL] [ORNL; Nazarov, Erkinjun [Sionex Corp] [Sionex Corp; Xu, Jun [ORNL] [ORNL

2010-01-01

302

Interim report on testing of off-gas treatment technologies for abatement of atmospheric emissions of chlorinated volatile organic compounds  

SciTech Connect

The purpose of this report is to briefly summarize the results to date of the off-gas treatment program for atmospheric emissions of chlorinated volatile organic compounds (CVOCs), in particular trichloroethylene (TCE) and perchloroethylene (PCE). This program is part of the Department of Energy`s Office of Technology Development`s Integrated Demonstration for Treatment of Organics in Soil and Water at a Non-Arid Site. The off-gas treatment program was initiated after testing of in-situ air stripping with horizontal wells was completed. That successful test expectedly produced atmospheric emissions of CVOCs that were unabated. It was decided after that test that an off-gas treatment program would complement the Integrated Demonstration not only because off-gas treatment is an integral portion of remediation of CVOC contamination in groundwater and soil but also because several technologies were being developed across the US to mitigate CVOC emissions. A single platform for testing off-gas treatment technologies would facilitate systematic and unbiased evaluation of the emerging technologies.

Haselow, J.S.; Jarosch, T.R.; Rossabi, J.; Burdick, S.; Lombard, K.

1993-12-01

303

Initial field test of High-Energy Corona process for treating a contaminated soil-offgas stream  

SciTech Connect

The High-Energy Corona (HEC) technology for treating process offgases has been under development at Pacific Northwest Laboratory (PNL) since 1991. The HEC process uses high-voltage electrical discharges in air to ionize the air, forming a low-temperature plasma that would be expected to destroy a wide variety of organic compounds in air. The plasma contains strong oxidants, possibly including hydroxyl radicals, hydroperoxy radicals, superoxide radicals, various excited as well as ionized forms of oxygen, high-energy electrons, and ultraviolet (UV) light. Because the high-voltage plasma is produced near ambient temperatures and pressures, yet exhibits extremely rapid destruction kinetics with relatively low power requirements, the HEC technique appears promising as a low-cost treatment technique (Virden et al. 1992). As part of the Volatile Organic Compound (VOC) Nonarid Integrated Demonstration (ID) at the DOE Savannah River Site, research activities were initiated in December 1991 to develop a prototype HEC process for a small-scale field demonstration to treat a soil-offgas stream contaminated with trichloroethylene (TCE) and perchloroethylene (PCE) at varying concentrations. Over an 18-month period, the HEC technology was developed on a fast track, through bench and pilot scales into a trailer-mounted system that was tested at the Nonarid ID. Other national laboratories, universities, and private companies have also participated at the Nonarid ID to demonstrate a number of conventional, emerging and innovative approaches for treating the same soil-offgas stream.

Shah, R R; Garcia, R E; Jeffs, J T; Virden, J W; Heath, W O

1995-04-01

304

Vibrational Spectroscopic and X-Ray Diffraction Studies of Cerium Zirconium Oxides with Ce\\/Zr Composition Ratio=1 Prepared by Reduction and Successive Oxidation of t?-(Ce 0.5Zr 0.5)O 2 Phase  

Microsoft Academic Search

Cerium zirconium oxides with the composition CeZrO4 were prepared by oxidizing in O2 at 873 K precursors with the composition CeZrO3.5+? (?<0.3). The precursors were prepared by reducing the t?-(Ce0.5Zr0.5)O2 phase at 873?Tred.?1573 K. The CeZrO4 compounds together with the precursors were characterized by powder X-ray diffraction and IR and Raman spectroscopies. In the case of 1323?Tred.?1573 K, the precursors

Takahisa Omata; Haruo Kishimoto; Shinya Otsuka-Yao-Matsuo; Norikazu Ohtori; Norimasa Umesaki

1999-01-01

305

Green remediation: enhanced reductive dechlorination using recycled rinse water as bioremediation substrate  

SciTech Connect

Enhanced reductive dechlorination (ERD) has rapidly become a remedy of choice for use on chlorinated solvent contamination when site conditions allow. With this approach, solutions of an organic substrate are injected into the affected aquifer to stimulate biological growth and the resultant production of reducing conditions in the target zone. Under the reducing conditions, hydrogen is produced and ultimately replaces chlorine atoms on the contaminant molecule causing sequential dechlorination. Under suitable conditions the process continues until the parent hydrocarbon precursor is produced, such as the complete dechlorination of trichloroethylene (TCE) to ethene. The process is optimized by use of a substrate that maximizes hydrogen production per unit cost. When natural biota are not present to promote the desired degradation, inoculates can be added with the substrate. The in-situ method both reduces cost and accelerates cleanup. Successful applications have been extended from the most common chlorinated compounds perchloroethylene (PCE) and TCE and related products of degradation, to perchlorate, and even explosives such as RDX and trinitrotoluene on which nitrates are attacked in lieu of chloride. In recent work, the process has been further improved through use of beverage industry wastewaters that are available at little or no cost. With material cost removed from the equation, applications can maximize the substrate loading without significantly increasing total cost. The extra substrate loading both accelerates reaction rates and extends the period of time over which reducing conditions are maintained. In some cases, the presence of other organic matter in addition to simple sugars provides for longer performance times of individual injections, thereby working in a fashion similar to emulsified vegetable oil. The paper discusses results of applications at three different sites contaminated with chlorinated ethylenes. The applications have included wastewaters of both natural fruit juices and corn syrup solutions from carbonated beverages. Cost implications include both the reduced cost of substrate and the cost avoidance of needing to pay for treatment of the wastewater. (authors)

Dawson, Gaynor; McKeon, Tom [CALIBRE Systems, Inc., Bellevue, WA (United States)

2007-07-01

306

The pseudophase approach to assessing chemical partitioning in air-water-cyclodextrin systems.  

PubMed

Henry's Law constants (HLCs) of several common, subsurface hydrophobic organic pollutants (HOPs) including trichloroethylene (TCE), perchloroethylene (PCE) and benzene, toluene, ethylbenzene, and o-xylene (BTEX), were measured using a static headspace phase ratio (SHPR) method over a range of temperatures (35, 45, 55, and 65 degrees C) and experimentally and operationally relevant cyclodextrin (CD) concentrations (0, 10, 20, 50, and 100 g L(-1)). In aqueous CD solutions, HLC values decrease according to a power law relationship with increasing CD concentration due to an apparent solubility enhancement caused by HOP partitioning to the hydrophobic cavity of CD molecules. The temperature dependence of air-water partitioning under the influence of CD was well described by the van't Hoff equation for all HOPs tested. A three-phase equilibrium model was used to interpret air-water-CD partitioning data, treating CD as a pseudophase. Our results show that HOP CD-water partition coefficients decrease linearly with increasing temperature. CD-water partition coefficients were generally independent of CD concentration, with a few exceptions. Comparison of our results for hydroxypropyl-beta-CD and TCE to those from another study showed several major discrepancies, which were attributed to differences in the experimental methods employed. Our attempt to correlate CD-water partition coefficients with HOP chemical properties indicates that correlations based on individual chemical descriptors (e.g., aqueous solubility, octanol-water partition coefficient, molecular volume or ET (30) polarity index) will not be sufficient to obtain accurate estimates of HOP CD-water partition coefficients for other compounds with differing chemical structures. PMID:19475975

Gao, Heng; Blanford, William J; Birdwell, Justin E

2009-04-15

307

Applications of Monitored Natural Attenuation in the USA (Presentation)  

EPA Science Inventory

Monitored Natural Attenuation (MNA) is widely applied in the USA to control the risk associated with ground water contamination from chlorinated solvents such a tetrachloroethylene (PCE) and trichloroethylene (TCE). MNA relies on the natural processes of degradation, sorption an...

308

Applications of Monitored Natural Attenuation in the USA (Abstract)  

EPA Science Inventory

Monitored Natural Attenuation (MNA) is widely applied in the USA to control the risk associated with ground water contamination from chlorinated solvents such a tetrachloroethylene (PCE) and trichloroethylene (TCE). MNA relies on the natural processes of degradation, sorption an...

309

IN-PLACE REGENERATION OF SVE LOADED GAC USING FENTON'S REAGENTS  

EPA Science Inventory

Ten out of the 25 most frequently detected groundwater contaminants at hazardous waste sites are chlorinated volatile organic compounds (VOCs) 1. Trichloroethylene (TCE) and tetrachloroethylene (PCE) are among the top three 1. Granular activated carbon (GAC) adsorption is widel...

310

IN-PLACE REGENERATION OF SVE LOADED GAC USING FENTON'S REAGENTS  

EPA Science Inventory

Ten out of the 25 most frequently detected groundwater contaminants at hazardous waste sites are chlorinated volatile organic compounds (VOCs) 1 . Trichloroethylene (TCE) and tetrachloroethylene (PCE) are among the top three 1 . Granular activated carbon (GAC) adsorption is w...

311

DEMONSTRATION BULLETIN: AQUADETOX®/ SVE SYSTEM and AWD Technologies, Inc.  

EPA Science Inventory

The AWD technology simultaneously treats groundwater and soil-gas contaminated with volatile or ganic compounds (VOC), such as trichloroethylene (TCE) and tetrachloroethylene (PCE). This technology integrates two processes: (1) AquaDetox®, a moderate vacuum (pressure about 50 ...

312

Generalized solution to multispecies transport equations coupled with a first-order reaction network  

E-print Network

at complex field sites because most field problems involve multiple reactive contaminants. Examples include nuclear waste sites contaminated with radioactive species and their daughter products and hazardous waste sites contaminated with chlorinated solvents such as PCE (tetrachloroethylene) and TCE

Clement, Prabhakar

313

BIODEGRADATION OF CHLORINATED SOLVENTS: REACTIONS NEAR DNAPL AND ENZYME FUNCTION  

EPA Science Inventory

Chlorinated solvents are among the most common organic chemical groundwater contaminants at DOE sites, as well as at DOD and industrial facilities. Included are the solvents trichloroethene (TCE), tetrachloroethene (PCE), and carbon tetrachloride (CT). Commonly these contaminan...

314

MICROBIAL UTILIZATION OF VADOSE ZONE ORGANIC CARBON FOR REDUCTIVE DECHLORINATION OF TETRACHLOROETHENE  

EPA Science Inventory

Aqueous extracts from a calcareous spodosol were used as the primary substrate to study the reductive dechlorination of tetrachloroethene (PCE). A comparison was made between extracts obtained using pure water and water saturated with trichloroethene (TCE). The latter solutions w...

315

SURFACTANT-ENHANCED SOLUBILIZATION OF TETRACHLOROETHYLENE AND DEGRADATION PRODUCTS IN PUMP AND TREAT REMEDIATION  

EPA Science Inventory

Experiments were conducted to investigate the enhanced solubilization of tetrachloroethylene (PCE), trichloroethylene (TCE), and 1,2-dichloroethylene (DCE) in nonionic surfactant solutions of Triton X-100, Brij-30, Igepal CA-720, and Tergitol NP-10 (alkylpolyoxyethylenes). urfact...

316

Contributions of Fe Minerals to Abiotic Dechlorination  

EPA Science Inventory

Most applications of enhanced in situ bioremediation are based on biological reductive dechlorination. Anaerobic metabolism can also produce reactive minerals that allow for in situ biogeochemical transformation of chlorinated organic contaminants such as PCE, TCE, and cis-DCE. ...

317

CONTROLLED RELEASE, BLIND TEST OF DNAPL REMEDIATION BY ETHANOL FLUSHING  

EPA Science Inventory

A dense nonaqueous phase liquid (DNAPL) source zone was established within a sheet-pile isolated cell through a controlled release of perchloroethylene (PCE) to evaluate DNAPL remediation by in-situ cosolvent flushing. Ethanol was used as the cosolvent, and the main remedia...

318

Degradation of Environmental Contaminants with Water-Soluble Cobalt Catalysts: An Integrative Inorganic Chemistry Investigation  

ERIC Educational Resources Information Center

We present an integrative laboratory investigation incorporating skills from inorganic chemistry, analytical instrumentation, and physical chemistry applied to a laboratory-scale model of the environmental problem of chlorinated ethylenes in groundwater. Perchloroethylene (C[subscript 2]Cl[subscript 4], PCE) a common dry cleaning solvent,…

Evans, Alexandra L.; Messersmith, Reid E.; Green, David B.; Fritsch, Joseph M.

2011-01-01

319

EFFECTS OF FOUR TRIHALOMETHANES ON DNA STRAND BREAKS, RENAL HYALINE DROPLET FORMATION AND SERUM TESTOSTERONE IN MALE F-344 RATS  

EPA Science Inventory

All four possible trihalomethanes (THMs) containing bromine and chlorine, as well as perchloroethylene (PCE), were evaluated for their ability to produce DNA strand breaks, a2u-globulin rich renal deposits, and testosterone changes in male F-344 rats. Rats received daily equimola...

320

Biodegradation of chlorinated aliphatic hydrocarbon mixtures in a single-pass packed-bed reactor  

Microsoft Academic Search

Aliphatic chlorinated compounds, such as trichloroethylene (TCE) and tetrachloroethylene (PCE), are major contaminants of\\u000a ground water. A single-pass packed-bed bioreactor was utilized to study the biodegradation of organic waste mixtures consisting\\u000a of PCE, TCE, and other short-chain chlorinated organics. The bioreactor consisted of two 1960-mL glass columns joined in a\\u000a series. One column was packed with sand containing a microbial

L. W. Lackey; T. J. Phelps; P. R. Bienkowski; D. C. White

1993-01-01

321

Radiolytic and thermal dechlorination of organic chlorides adsorbed on molecular sieve 13X.  

PubMed

Reductive dechlorination of chlorobenzene (PhCl), trichloroethylene (TCE), tetrachloroethylene (PCE), 1- and 2-chlorobutanes, chloroform, carbon tetrachloride, and 1,1,1- and 1,1,2-trichloroethanes adsorbed on molecular sieve 13X was investigated. The molecular sieve adsorbing the organic chlorides was irradiated with gamma-rays, heated, or allowed to stand at room temperature in a sealed ampule and was then soaked in water. The dechlorination yields were determined from the Cl- concentrations of the supernatant aqueous solutions. It was found that the chlorinated alkanes adsorbed on the molecular sieve are readily dechlorinated on standing at room temperature. The dechlorination at room temperature was limited for TCE and PCE. PhCl was quite stable even at 200 degrees C. gamma-Radiolysis was examined for PhCl, TCE, and PCE at room temperature. The radiation chemical yields of the dechlorination, G(Cl-), were 1.9, 40, and 30 for PhCl, TCE, and PCE, respectively. After 5 h of heating at 200 degrees C, the dechlorination yields for TCE and PCE were 24.5 and 4.3%, respectively. TCE is much more reactive than PCE in the thermal dechlorination, whereas their radiolytic dechlorination yields are comparable. The pH of the supernatant solutions decreased along with the dechlorination. PMID:11393996

Yamamoto, Y; Tagawa, S

2001-05-15

322

Using trees to remediate groundwaters contaminated with chlorinated hydrocarbons. 1997 annual progress report  

Microsoft Academic Search

'Metabolism of Chlorinated Hydrocarbons Laboratory and field tests with poplar in tissue culture, bioreactors, and field sites have shown that, unlike bacteria, these plants are able to carry out complete degradation of fully chlorinated alkanes and alkenes to carbon dioxide and chloride. Carbon dioxide was produced as a product of the degradation of trichloroethylene (TCE), carbon tetrachloride (CT), and perchloroethylene

M. P. Gordon; L. A. Newman; S. E. Strand

1997-01-01

323

Monitoring the decontamination of a site polluted by DNAPLs  

NASA Astrophysics Data System (ADS)

The aim of this study is to monitor the decontamination of a site polluted by DNAPLs coming from an automotive industry. The contamination was caused by the poor management of the waste generated by the industrial activity, which was discharged into a seepage pit. As a result, soil contamination was produced in the seepage pit area and a plume of DNAPLs-contaminated groundwater was generated. To recover the original environmental quality, a dual action was proposed: in the first place, the removal of the source of contamination and in the second one, the treatment of the DNAPLs plume. The elimination of the source of contamination consisted on a selective excavation of the seepage pit and an offsite management of the contaminated land. To restore the groundwater quality, a passive treatment system using a permeable reactive barrier (PRB) of zero valent iron (ZVI) was implemented. In order to determine the efficiency of the remediation actions, a chemical, isotopic and hydrogeological control of the main solvents detected in groundwater (perchloroethylene -PCE-, trichloroethene -TCE- and cis-dichloroethylene -cis-DCE-) has been established. Results show a decrease in PCE concentration that has been attributed to the removal of the source more than to a degradation process. However, the presence of PCE by-products, TCE and cis-DCE, might indicate a possible PCE biotic degradation. ?13CPCE values analyzed upstream and downstream of the barrier don't show isotopic changes associated to the PRB (values are around -20‰ in all the sampling points). TCE might have experienced a natural advanced degradation process according to the high concentration of cis-DCE found prior the installation of the PRB and the isotopic enrichment in ?13CTCE in some specific areas of the plume (-19.9‰ in the source and -16‰ before the barrier). Slight isotopic changes have been observed in the water flow in a far distance after the barrier (-15.4‰). ?13Ccis-DCE experienced an enrichment upstream to downstream of the barrier (from -15.5‰ to -11.5‰) indicating that a possible abiotic degradation due to the PRB is being produced. However, an enrichment in ?13Ccis-DCE from the focus area to the barrier (from -19.9‰ to -15.5‰) was also detected, suggesting that biotic degradation of cis-DCE is occurring in the field. As a conclusion, preliminary concentration and isotopic results seem to indicate that the PRB does not intercept the whole contaminated plume. The installation of a monitoring system of multilevel piezometers of new construction around the PRB has been proposed in order to study in detail the underground sections most affected by pollution and help to define patterns of migration of DNAPLs in the subsurface, giving the possibility to improve the design of the ZVI-PRB.

Audí-Miró, C.; Espinola, R.; Torrentó, C.; Otero, N.; Rossi, A.; Palau, J.; Soler, A.

2012-04-01

324

Methods for environmental monitoring of DOE waste disposal and storage sites. Semiannual progress report, April 1, 1988--September 30, 1988  

SciTech Connect

Perchloroethylene (PCE) is a persistent environmental contaminant whose chemical stability and hydrophobicity have made it difficult to remove from contaminated groundwater. PCE is also toxic and has been implicated as a carcinogen. This study was aimed at assessing methods for biological degradation of PCE. As a part of the study, the authors have characterized possible products of the degradation of PCE, and have determined the effects of detergents and solvents on the water solubility of PCE and on the toxic effects of PCE on bacteria. The authors have also isolated PCE-resistant microorganisms from monitoring wells at Y-12. To date all of the PCE-resistant bacteria isolated from the monitoring wells have been of the genus Bacillus. One of these isolates appears to be able to degrade PCE, as indicated by the disappearance of PCE from cultures of growing cells. The organism does not grow on PCE as the sole carbon source, so degradation of the solvent must occur by cometabolism.

Hadden, C.T.; Benson, S.B.; Osborne, T.R.; Revis, N.W.

1988-12-31

325

COMMUNICATION TO THE EDITOR Aerobic Degradation of Mixtures of  

E-print Network

(TCE) INTRODUCTION Both tetrachloroethylene (PCE) and trichloroethylene (TCE) are suspected carcinogens and are the most common groundwater pollutants at hazardous waste sites (McCarty, 1997). These effective solvents carcinogen (McCarty, 1997). Both VC and cis-DCE are U.S. Environmental Protection Agency priority pollut

Wood, Thomas K.

326

Vibrational Spectroscopic and X-Ray Diffraction Studies of Cerium Zirconium Oxides with Ce/Zr Composition Ratio=1 Prepared by Reduction and Successive Oxidation of t?-(Ce0.5Zr0.5)O2 Phase  

NASA Astrophysics Data System (ADS)

Cerium zirconium oxides with the composition CeZrO4 were prepared by oxidizing in O2 at 873 K precursors with the composition CeZrO3.5+? (?<0.3). The precursors were prepared by reducing the t?-(Ce0.5Zr0.5)O2 phase at 873?Tred.?1573 K. The CeZrO4 compounds together with the precursors were characterized by powder X-ray diffraction and IR and Raman spectroscopies. In the case of 1323?Tred.?1573 K, the precursors were identified as having the pyrochlore-type Ce2Zr2O7+2? phase with ?<0.06. When the reduction temperature was decreased, the ordering level between Ce and Zr ions was decreased in the pyrochlore-type phase. The CeZrO4 compounds obtained by oxidizing the pyrochlore-type precursors were identified as the ?-CeZrO4 phase in which Ce and Zr ions are in an ordered arrangement similar to that of the pyrochlore-type structure. The space group of the ? phase was not the same as that of the pyrochlore-type structure. In the case of Tred.?1123 K, cubic CaF2-related-type (Ce0.5Zr0.5)O(3.5+?)/2 phases with 0.1t?-(Ce0.5Zr0.5)O2 phase identical to the starting sample appeared. The structural difference between t?meta and t? phases was estimated to be in their oxygen parameter, z, for the 4d site in the space group of P42/nmc. The oxygen parameter for the t?meta phase is closer to 0.25 than that for t? phase. It was shown that the temperature and holding time for precursor preparation and the oxygen content ? are important factors for the structure of the reoxidized CeZrO4 compound.

Omata, Takahisa; Kishimoto, Haruo; Otsuka-Yao-Matsuo, Shinya; Ohtori, Norikazu; Umesaki, Norimasa

1999-11-01

327

Compound-specific isotope analysis: Questioning the origins of a trichloroethene plume  

USGS Publications Warehouse

Stable carbon isotope ratios of trichloroethene (TCE), cis-1,2- dichloroethene, and trans-1,2-dichloroethene were determined by use of gas chromatography-combustion-isotope ratio mass spectroscopy to determine whether compound-specific stable carbon isotopes could be used to help understand the origin and history of a TCE groundwater plume in Fort Worth, TX. Calculated ??13C values for total chlorinated ethenes in groundwater samples, which can approximate the ??13C of a spilled solvent if all degradation products are accounted for, were useful for determining whether separate lobes of the plume resulted from different sources. Most notably, values for one lobe, where tetrachloroethene (PCE) has been detected periodically, were outside the range for manufactured TCE but within the range for manufactured PCE, whereas values for a separate lobe, which is downgradient of reported TCE spills, were within the range for manufactured TCE. Copyright ?? Taylor & Francis Group, LLC.

Eberts, S.M.; Braun, C.; Jones, S.

2008-01-01

328

DNAPLs at DOE sites: Background and assessment of characterization technologies  

SciTech Connect

The Characterization, Monitoring, and Sensor Technology Integrated Program (CMST-IP) within the Office of Technology Development (OTD) has responsibility for identification, evaluation, and delivery of technologies needed for the work of the Department of Energy`s Office of Environmental Restoration and Waste Management. This report addresses part of that responsibility by providing summary information on DNAPL site characterization. A dense nonaqueous phase liquid (DNAPL) is a source of contamination that can persist in the subsurface for decades before dissipating completely into the vapor phase and groundwater. The DNAPL chemicals of particular concern to the DOE are chlorinated volatile organic compounds (Cl VOCS) such as carbon tetrachloride (CCl{sub 4}), trichloroethylene (TCE), and perchloroethylene (PCE). These Cl VOCs were used in multiple ton quantities at DOE sites and were often released to the subsurface. The predicted fate of released Cl VOC liquid is downward movement through the soil under the force of gravity. As it moves, some of the Cl VOC liquid becomes trapped in the soil pores as residual saturation. The liquid also moves rapidly downward if small fractures are present. This migration continues until an impermeable or semi-permeable layer is encountered. Then lateral movement or spreading occurs. The downward and lateral migration in the subsurface leads to DNAPL pools, lenses, and residual saturation that can cause long-term contamination of groundwater at levels well above drinking water standards. Although Cl VOCs have been detected as dissolved components in the groundwater and as vapor in the soil gas at several DOE sites, direct evidence of their presence as DNAPL is sparse and no measurements of the amounts of DNAPL present within a given volume of subsurface have been made. Consequently, unresolved DNAPL issues exist at DOE sites.

Junk, G.A.; Haas, W.J. Jr.

1993-12-01

329

A theoretical model of air and steam co-injection to prevent the downward migration of DNAPLs during steam-enhanced extraction  

NASA Astrophysics Data System (ADS)

When steam is injected into soil containing a dense volatile non-aqueous phase liquid contaminant the DNAPL vaporized within the heated soil region condenses and accumulates ahead of the steam condensation front. If enough DNAPL accumulates, gravitational forces can overcome trapping forces allowing the liquid contaminant to flow downward. By injecting air with steam, a portion of the DNAPL vapor remains suspended in equilibrium with the air, decreasing liquid contaminant accumulation ahead of the steam condensation front, and thus reducing the possibility of downward migration. In this work, a one-dimensional theoretical model is developed to predict the injection ratio of air to steam that will prevent the accumulation of volatile DNAPLs. The contaminated region is modeled as a one-dimensional homogeneous porous medium with an initially uniform distribution of a single component contaminant. Mass and energy balances are combined to determine the injection ratio of air to steam that eliminates accumulation of the contaminant ahead of the steam condensation front, and hence reduces the possibility of downward migration. The minimum injection ratio that eliminates accumulation is defined as the optimum injection ratio. Example calculations are presented for three DNAPLs, carbon tetrachloride (CCl 4), trichloroethylene (TCE), and perchloroethylene (PCE). The optimum injection ratio of air to steam is shown to depend on the initial saturation and the volatility of the liquid contaminant. Numerical simulation results are presented to validate the model, and to illustrate downward migration for ratios less than optimum. Optimum injection ratios determined from numerical simulations are shown to be in good agreement with the theoretical model.

Kaslusky, Scott F.; Udell, Kent S.

2002-04-01

330

A theoretical model of air and steam co-injection to prevent the downward migration of DNAPLs during steam-enhanced extraction.  

PubMed

When steam is injected into soil containing a dense volatile non-aqueous phase liquid contaminant the DNAPL vaporized within the heated soil region condenses and accumulates ahead of the steam condensation front. If enough DNAPL accumulates, gravitational forces can overcome trapping forces allowing the liquid contaminant to flow downward. By injecting air with steam, a portion of the DNAPL vapor remains suspended in equilibrium with the air, decreasing liquid contaminant accumulation ahead of the steam condensation front, and thus reducing the possibility of downward migration. In this work, a one-dimensional theoretical model is developed to predict the injection ratio of air to steam that will prevent the accumulation of volatile DNAPLs. The contaminated region is modeled as a one-dimensional homogeneous porous medium with an initially uniform distribution of a single component contaminant. Mass and energy balances are combined to determine the injection ratio of air to steam that eliminates accumulation of the contaminant ahead of the steam condensation front, and hence reduces the possibility of downward migration. The minimum injection ratio that eliminates accumulation is defined as the optimum injection ratio. Example calculations are presented for three DNAPLs, carbon tetrachloride (CCl4), trichloroethylene (TCE), and perchloroethylene (PCE). The optimum injection ratio of air to steam is shown to depend on the initial saturation and the volatility of the liquid contaminant. Numerical simulation results are presented to validate the model, and to illustrate downward migration for ratios less than optimum. Optimum injection ratios determined from numerical simulations are shown to be in good agreement with the theoretical model. PMID:11999630

Kaslusky, Scott F; Udell, Kent S

2002-04-01

331

Development of an integrated, in-situ remediation technology. Draft topical report for task No. 9. Part II. Entitled: TCE degradation using non-biological methods, September 26, 1994--May 25, 1996  

SciTech Connect

Contamination in low permeability soils poses a significant technical challenge to in-situ remediation efforts. Poor accessibility to the contaminants and difficulty in delivery of treatment reagents have rendered existing in-situ treatments such as bioremediation, vapor extraction, pump and treat rather ineffective when applied to low permeability soils present at many contaminated sites. The technology is an integrated in-situ treatment in which established geotechnical methods are used to install degradation zones directly in the contaminated soil and electro-osmosis is utilized to move the contaminants back and forth through those zones until the treatment is completed. The use of zero valence iron for reductive dechlorination of aliphatic chlorinated hydrocarbons is currently under investigation by a number of research groups as a potential method of in-situ treatment of contaminated ground water. The reaction appears to involve the transfer of electrons to chloro-aliphatic compounds by the oxidation of zero valence iron to ferrous iron (Fe{sup +2}). Our studies have indicated that this reaction is consistent with those of corrosion, and as such, can be influenced or increased by the presence of small amounts of metals (5% by weight) such as copper, tin, silver, gold and palladium coated on the iron surface. Incomplete coverage of the iron surface with a more electropositive metal results in an open galvanic cell, which increases the oxidation of iron and facilitates and increases the concurrent reduction of trichloroethylene and other chlorinated aliphatic compounds to the corresponding alkenes and alkanes. Our results show that plating more electropositive metals onto certain iron surfaces results in approximately a factor of ten increase in the dechlorination rate of small organochlorine compounds such as TCE.

Orth, R.G.; McKenzie, D.E.

1997-04-01

332

Degradation of Perchloroethylene and Dichlorophenol by Pulsed-Electric  

E-print Network

% of 108 sampled finished drinking water sites (Syracuse Research Corpora- tion, 1992). Damage the number of PED-treatment cycles, rather than the tested voltages and frequencies. Using this two) as well as in groundwater supplies, and water stan- dard limits are set to 0.30 g/L (United States

Wood, Thomas K.

333

Dechlorination of TCE with palladized iron  

DOEpatents

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products.

Fernando, Quintus (Tucson, AZ); Muftikian, Rosy (Tucson, AZ); Korte, Nic (Grand Junction, CO)

1997-01-01

334

Reclamation of elemental sulfur from flue gas biodesulfurization waste sludge.  

PubMed

Perchloroethylene (PCE) extraction was used to reclaim elemental sulfur from flue gas biodesulfurization sludge. The sludge was generated from a biodesulfurization system that concurrently treated the flue gas scrubbing solution and wastewater of citric acid production. The sludge contained approximately 40-60% elemental sulfur; other components included flue gas dust, biomass, inorganic salts, and flocculants. The sulfur was extracted with PCE at 80 degrees C, and then separated from the sludge by hot filtration. The elemental sulfur was then recovered from the PCE solution by recrystallization and centrifugation. When the dried sludge with particle size less than 0.2 mm was used in the PCE extraction, more than 90% of the elemental sulfur in the sludge could be recovered with a contact time of 15 min and a PCE-to-sludge ratio of 5 mL PCE/g sludge. The recovered sulfur generally had purities of 98-99.9% and could be directly used in many industries. Reuse of the PCE solvent in the extraction protocol through four cycles did not adversely influence the sulfur recovery efficiency. The results indicated that the PCE extraction was an effective method for the sulfur recovery from the biodesulfurization sludge. PMID:20480860

Wang, Chengwen; Wang, Yujue; Zhang, Yanqi; Zhao, Qi; Wang, Ran

2010-05-01

335

Human Health Effects of Tetrachloroethylene: Key Findings and Scientific Issues  

PubMed Central

Background: The U.S. Environmental Protection Agency (EPA) completed a toxicological review of tetrachloroethylene (perchloroethylene, PCE) in February 2012 in support of the Integrated Risk Information System (IRIS). Objectives: We reviewed key findings and scientific issues regarding the human health effects of PCE described in the U.S. EPA’s Toxicological Review of Tetrachloroethylene (Perchloroethylene). Methods: The updated assessment of PCE synthesized and characterized a substantial database of epidemiological, experimental animal, and mechanistic studies. Key scientific issues were addressed through modeling of PCE toxicokinetics, synthesis of evidence from neurological studies, and analyses of toxicokinetic, mechanistic, and other factors (tumor latency, severity, and background rate) in interpreting experimental animal cancer findings. Considerations in evaluating epidemiological studies included the quality (e.g., specificity) of the exposure assessment methods and other essential design features, and the potential for alternative explanations for observed associations (e.g., bias or confounding). Discussion: Toxicokinetic modeling aided in characterizing the complex metabolism and multiple metabolites that contribute to PCE toxicity. The exposure assessment approach—a key evaluation factor for epidemiological studies of bladder cancer, non-Hodgkin lymphoma, and multiple myeloma—provided suggestive evidence of carcinogenicity. Bioassay data provided conclusive evidence of carcinogenicity in experimental animals. Neurotoxicity was identified as a sensitive noncancer health effect, occurring at low exposures: a conclusion supported by multiple studies. Evidence was integrated from human, experimental animal, and mechanistic data sets in assessing adverse health effects of PCE. Conclusions: PCE is likely to be carcinogenic to humans. Neurotoxicity is a sensitive adverse health effect of PCE. Citation: Guyton KZ, Hogan KA, Scott CS, Cooper GS, Bale AS, Kopylev L, Barone S Jr, Makris SL, Glenn B, Subramaniam RP, Gwinn MR, Dzubow RC, Chiu WA. 2014. Human health effects of tetrachloroethylene: key findings and scientific issues. Environ Health Perspect 122:325–334;?http://dx.doi.org/10.1289/ehp.1307359 PMID:24531164

Hogan, Karen A.; Scott, Cheryl Siegel; Cooper, Glinda S.; Bale, Ambuja S.; Kopylev, Leonid; Barone, Stanley; Makris, Susan L.; Glenn, Barbara; Subramaniam, Ravi P.; Gwinn, Maureen R.; Dzubow, Rebecca C.; Chiu, Weihsueh A.

2014-01-01

336

Chlorine isotope fractionation during reductive dechlorination of chlorinated ethenes by anaerobic bacteria.  

PubMed

Chlorine isotope fractionation during reductive dechlorination of trichloroethene (TCE) and tetrachloroethene (PCE) to cis-1,2-dichloroethene (cDCE) by anaerobic bacteria was investigated. The changes in the 37Cl/35Cl ratio observed during the one-step reaction (TCE to cDCE) can be explained by the regioselective elimination of chlorine accompanied by the Rayleigh fractionation. The fractionation factors (alpha) of the TCE dechlorination by three kinds of anaerobic cultures were approximately 0.994-0.995 at 30 degrees C. The enrichment of 37Cl in the organic chlorine during the two-step reaction (PCE to cDCE) can be explained by the random elimination of one chlorine atom in the PCE molecule followed by the regioselective elimination of one chlorine atom in the TCE molecule. The fractionation factors for the first step of the PCE dechlorination with three kinds of anaerobic cultures were estimated to be 0.987-0.991 at 30 degrees C using a mathematical model. Isotope fractionation during the first step would be the primary factor for the chlorine isotope fractionation during the PCE dechorination to cDCE. The developed models can be utilized to evaluate the fractionation factors of regioselective and multistep reactions. PMID:12387413

Numata, Masahiko; Nakamura, Noboru; Koshikawa, Hiromoto; Terashima, Yutaka

2002-10-15

337

Bio-reduction of tetrachloroethen using a H2-based membrane biofilm reactor and community fingerprinting.  

PubMed

Chlorinated ethenes in drinking water could be reductively dechlorinated to non-toxic ethene by using a hydrogen based membrane biofilm reactor (H2-MBfR) under denitrifying conditions as it provides an appropriate environment for dechlorinating bacteria in biofilm communities. This study evaluates the reductive dechlorination of perchloroethene (PCE) to non-toxic ethene (ETH) and comparative community analysis of the biofilm grown on the gas permeable membrane fibers. For these purposes, three H2-MBfRs receiving three different chlorinated ethenes (PCE, TCE and DCE) were operated under different hydraulic retention times (HRTs) and H2 pressures. Among these reactors, the H2-MBfR fed with PCE (H2-MBfR 1) accomplished a complete dechlorination, whereas cis-DCE accumulated in the TCE receiving H2-MBfR 2 and no dechlorination was detected in the DCE receiving H2-MBfR 3. The results showed that 95% of PCE dechlorinated to ETH together with over 99.8% dechlorination efficiency. Nitrate was the preferred electron acceptor as the most of electrons generated from H2 oxidation used for denitrification and dechlorination started under nitrate deficient conditions at increased H2 pressures. PCR-DGGE analysis showed that Dehalococcoides were present in autotrophic biofilm community dechlorinating PCE to ethene, and RDase genes analysis revealed that pceA, tceA, bvcA and vcrA, responsible for complete dechlorination step, were available in Dehalococcoides strains. PMID:24731873

Karata?, Serdar; Hasar, Halil; Ta?kan, Ergin; Özkaya, Bestamin; ?ahinkaya, Erkan

2014-07-01

338

Path Computation Element (PCE) 1. What is QoS?  

E-print Network

there is stricter service demands that can't be provided by the default systems For example: o Video Streaming o VoIP o Cloud Computing 4 #12;Qualities of traffic Low throughput Dropped Packets Errors Latency

339

CONCURRENT INJECTION OF COSOLVENT AND AIR FOR ENHANCED PCE REMOVAL  

EPA Science Inventory

The goal of this study was to use preferential flow of air to improve the dynamics of cosolvent displacement in order to enhance DNAPL displacement and dissolution. The concurrent injection of cosolvent and air was evaluated in a glass micromodel for a DNAPL remediation technolog...

340

In situ bioremediation via horizontal wells. Revision 1  

SciTech Connect

The test consisted of methane mixed with air into the contaminated aquifer via a horizontal well and extraction from the vadose zone via a parallel horizontal well. This configuration has the advantage of simultaneously stimulating methanotrophic activity in both the groundwater and vadose zone, and inhibiting spread of the contaminant plume. Groundwater was monitored biweekly from 13 wells for a variety of chemical and microbiological parameters. Groundwater from wells in affected areas showed increases in methanotrophs of more than 1 order of magnitude every 2 weeks for several weeks after 1% methane-in-air injection was started. Some wells had increases as much as 7 orders of magnitude. Simultaneous with the increase in methanotrophs was a decrease in water and soil gas concentrations of trichloroethylene (TCE) and tetrachloroethane (PCE). Two wells declined in TCE/PCE concentration in the water by more than 90% to below 2 ppb. All of the wells in the affected zone showed significant decreases in contaminants in less than one month. Chloride concentrations in the water were inversely correlated with TCE/PCE concentration. Four of five vadose zone piezometers declined from concentration as high as 10,000 ppm to less than 5 ppm in less than 6 weeks. The fifth cluster also declined by more than 95%. After only three months on injection, a decline in TCE/PCE in the sediment of more than 30% was also observed, with TCE/PCE being undetectable in most sediments at the end of the 14-month test. Gene probes and direct isolation from the water and sediment revealed that the right types of methanotrophs were being stimulated and that isolates could degrade TCE at a high rate.

Hazen, T.C.; Looney, B.B.; Enzien, M.; Dougherty, J.M.; Wear, J.; Fliermans, C.B.; Eddy, C.A.

1993-12-01

341

Quantitative evaluation of perchlorethylene in groundwater before and after its oxidation by helical solid sorbent extraction and gas chromatography.  

PubMed

An integrated method of dynamic extraction of perchloroethylene (PCE) with polydimethylsiloxane (PDMS) helical solid sorbent followed by injection into a gas chromatograph was developed for the determination of the real concentration of PCE in groundwater before and after its degradation by oxidation with KMnO(4). The main parameters (agitation, temperature, salts, pH) that affect the extraction efficiency have been evaluated and optimized. The increase of the extracted amount of PCE due to the presence of the salts could be partially compensated by the opposite effect of the insoluble MnO(2), and of the presence of HCl and the global effect of the matrix would be less important for the reproducibility of the PCE extraction. The quantitative analysis of PCE was carried out with the external standard method using the calibration-curve technique. The limit of detection for PCE was found of 0.05 mg L(-1) using flame ionization detector. The solubility of PCE in water was studied by extraction of PCE with PDMS helical solid sorbent from standard solution with different amounts of PCE added into the same volume of water and was found to decrease with settling time, because the fine droplets created during the agitation of the mixture were slowly merged in drops on the bottle walls and were not transferred into the extraction vial for GC analysis. The limit of solubility was evaluated using a graphical method and was estimated at 224.2+/-15.7 mg L(-1) of PCE in water at 25 degrees C. PMID:19285337

Draga, Marius; Ciucanu, Ionel; Agotici, Vlad; Fernandez, Aurora; Barna, Radu

2009-05-01

342

Electrical impedance tomography of the 1995 OGI perchloroethelyne release  

SciTech Connect

Goal is to determine if electrical impedance tomography (EIT) might be useful to map free product DNAPL (dense nonaqueous phase liquids) contamination. EIT was used to image the plume resulting from a release of 189 liters (50 gallons) of perchloroethylene (PCE) into a saturated aquifer constructed of sand with two layers of bentonite. Images were made in 4 planes, before, during, and after the release, to generate a detailed picture of the spatial and temporal development of the plume. Information of the EI (both in phase and out of phase voltages) was used at several different frequencies to produce images. Some frequency dispersion was observed in the images before and after the PCE release. Laboratory measurements of organic contamination in soil indicate detectable dispersion. A search for this effect in EIT images reveals weak evidence, the signal appearing just above the measurement uncertainty, of a change in the reactance in the soil because of the PCE.

Dailey, W.; Ramirez, A.

1996-10-01

343

Using ²²²Rn as a naturally occurring tracer to estimate NAPL contamination in an aquifer.  

PubMed

The naturally occurring radioisotope (222)Rn was used as a partitioning tracer to evaluate the presence and amount of a non-aqueous phase liquid (NAPL) in an aquifer. The batch experiment results of a diesel contaminated soil showed that the emanation rate of (222)Rn decreased to 31%, relative to a background rate. Batch experiment results of water contaminated by gasoline, diesel, PCE and TCE were similar. A field study to examine TCE contamination was conducted using 54 groundwater samples in Wonju city, Republic of Korea. Estimates of TCE contamination ranged from <0.001 mg/L to 14.3mg/L, and (222)Rn concentrations ranged from 1.89 Bq/L to 444. Results of (222)Rn analysis showed that TCE contamination was mainly restricted to an asphalt laboratory area and that the (222)Rn values of a NAPL-contaminated aquifer were correlated with TCE analytical results. PMID:23602707

Yoon, Yoon Yeol; Koh, Dong Chan; Lee, Kil Yong; Cho, Soo Young; Yang, Jae Ha; Lee, Kang Kun

2013-11-01

344

Degradation of Perchloroethene by zero-valent iron evaluated by carbon isotope fractionation  

NASA Astrophysics Data System (ADS)

Perchloroethene (PCE) is a widely spread groundwater contaminant in formally used industrial sites. Zero valent iron (ZVI) is used for in situ chemical reduction (ISCR) of PCE contaminants in the groundwater. A key factor in the application of in situ remediation technologies is a proper monitoring of contaminant reduction. The measurement of the stable isotope ratio is a promising method that is already used for quantifying microbial degradation of chlorinated contaminants. The carbon isotope ratio of PCE, measured by - isotope ratio mass spectrometry coupled to a gas chromatograph via a combustion interface (GC-C-IRMS), increases during degradation of PCE and can be directly related to the degree of degradation. It can be used to directly quantify chemical degradation and thus serves as a useful monitoring tool for groundwater remediation. An experiment to determine the carbon isotopic fractionation factor was performed as a lab experiment using Nanofer Star (NANOIRON). Two different PCE concentrations (c1: 220mgL-1, c2: 110mgL-1) mixed with 0.5 g of ZVI were sealed under deoxygenated conditions in 250 ml glas bottles locked with mininert caps. The bottles were incubated on a shaker for 865 h. Samples were taken weekly to measure the change in the carbon isotopic ratio of PCE as well as its concentration. Results showed a strong increase in the carbon isotope ratio (?-value) of PCE (start: -27 o end: -4 ), which indicates a significant dechlorination process of PCE. Beside PCE also one degradation product (Trichloroethylene - TCE) was measured. TCE was further dechlorinated as indicated by the ?-value change of TCE from -26 o to -4 oȦn unexpected intermediate value of -45 o for TCE was observed in the experiment. This fluctuation could be induced by the time depending concentration due to degradation and conversation processes. Furthermore, it seems that the progress of the ?-value is affected by the starting concentration of PCE (?-value of c1 < c2) as there is a higher ratio of PCE to ZVI.

Leitner, Simon; Watzinger, Andrea; Reichenauer, Thomas G.

2014-05-01

345

Natural Attenuation of Chlorinated Solvents and Fuel Components (BTEX and MTBE) in Ground Water  

EPA Science Inventory

Monitored Natural Attenuation is widely used in the USA to deal with ground water contamination from fuel components such as the BTEX compounds or MTBE or TBA and from chlorinated solvents such as PCE, TCE, and TCA. This presentation reviews the theory and practice of MNA in the...

346

Building Partnerships Whether sharing information across disciplines,  

E-print Network

: arsenic in drinking water, groundwater contamination by hydrocarbon solvents like TCE and PCE, and mine communities have relied on groundwater to service homes, businesses, and agricultural needs. But the area's expanding population is rapidly outgrowing its groundwater supplies, and local water agencies are eyeing

Fay, Noah

347

ANNUAL REPORT. DEVELOPMENT OF RADON AS A NATURAL TRACER FOR MONITORING THE REMEDIATION OF NAPL CONTAMINATION IN THE SUBSURFACE  

EPA Science Inventory

Dense non-aqueous phase liquids (DNAPLs) such as trichloroethene (TCE) and perchloroethene (PCE) present long-term challenges in terms of quantification in the subsurface at many DOE facilities. Over the past year we have continued investigating a potentially lower-cost method fo...

348

PHYSIOLOGICALLY-BASED TOXICOKINETIC MODELING OF THREE WATERBORNE CHLOROETHANES IN CHANNEL CATFISH, ICTALURUS PUNCTATUS  

EPA Science Inventory

A physiologically-based toxicokinetic model for fish was used to describe the uptake and disposition of three chlorinated ethanes in channel catfish (Ictalurus punctatus). atfish were simultaneously exposed to 1,1,2,2-tetrachloroethane (TCE), pentachloroethane (PCE), and hexachlo...

349

Aerobic/anaerobic/aerobic sequenced biodegradation of a mixture of chlorinated ethenes, ethanes and methanes in batch bioreactors.  

PubMed

A novel aerobic/anaerobic/aerobic treatment was implemented in batch reactors containing aquifer materials from a site contaminated by tetrachloroethylene (PCE), trichloroethylene (TCE), vinyl chloride (VC), 1,1,2-trichloroethane (1,1,2-TCA) and chloroform (CF). Consortia grown aerobically on methane, propane, n-pentane and n-hexane completely biodegraded the chlorinated solvent mixture, via aerobic cometabolism of VC, CF, TCE and 1,1,2-TCA, followed by PCE reductive dechlorination (RD) to 1,2-cis-dichlorothylene (cis-DCE) or TCE, and cis-DCE/TCE cometabolism in a further aerobic phase. n-Hexane was the best substrate. No electron donor was supplied for RD, which likely utilized cellular material produced during the aerobic phase. Chloride release was stoichiometric with chlorinated solvent biodegradation. According to the Lepidium sativum ecotoxicity test, a decreased toxicity was observed with propane, n-pentane and n-hexane, but not methane. A kinetic study of PCE RD allowed to estimate the PCE maximum specific rate (0.57 ± 0.07 mg mg(protein)(-1) day(-1)) and half-saturation constant (6.7 ± 1.5 mg L(-1)). PMID:23201903

Frascari, Dario; Fraraccio, Serena; Nocentini, Massimo; Pinelli, Davide

2013-01-01

350

Oxidation of tri- and perchloroethene in aqueous solution with ozone and hydrogen peroxide in a tube reactor  

Microsoft Academic Search

The reaction between trichloroethene (TCE) and perchloroethene (PCE) as micropollutants in water with ozone and hydrogen peroxide has been studied in a tube reactor. During the course of the reaction the micropollutants were nearly completely mineralized, as indicated by a stoichiometrical release of the organic chlorine as chloride ions. A mathematical model describing the kinetics of the oxidation was developed

Matthias Sunder; Dietmar-Christian Hempel

1997-01-01

351

7 Cometabolic Bioremediation T. C. Hazen  

E-print Network

7 Cometabolic Bioremediation T. C. Hazen Lawrence Berkeley National Laboratory, Berkeley, CA, USA.1007/978-3-540-77587-4_185, # Springer-Verlag Berlin Heidelberg, 2010 #12;Abstract: Cometabolic bioremediation is probably the most under bioremediation has been used on some of the most recalcitrant contami- nants, e.g., PCE, TCE, MTBE, TNT, dioxane

Hazen, Terry

352

EFFECT OF FENTON'S REAGENT ON SUBSURFACE MICROBIOLOGY AND BIODEGRADATION CAPACITY  

EPA Science Inventory

Microcosm studies were conducted to determine the effect of Fenton's reagent on subsurface microbiology and biodegradation capacity in a DNAPL (PCE/TCE) contaminated aquifer previously treated with the reagent. Groundwater pH declined from 5 to 2.4 immediately after the treatmen...

353

Quantification of groundwater contamination in an urban area using integral pumping tests  

Microsoft Academic Search

In this paper, the integral groundwater investigation method is used for the quantification of PCE and TCE mass flow rates at an industrialized urban area in Linz, Austria. In this approach, pumping wells positioned along control planes perpendicular to the groundwater flow direction are operated for a time period on the order of days and sampled for contaminants. The concentration

S. Bauer; M. Bayer-Raich; T. Holder; C. Kolesar; D. Müller; T. Ptak

2004-01-01

354

Installation Name ____________________________________________________________ Site Name / I.D. ____________________________________________________________  

E-print Network

chlorinated solvents (e.g., TCE, PCE) and BTEX compounds are efficiently removed by air stripping used to remove volatile contaminants from a water stream. It is divided into the following sections: 1 used for the removal of volatile, dissolved contaminants having low solubility, in order to meet

US Army Corps of Engineers

355

JOURNAL OF BACTERIOLOGY, Aug. 2009, p. 52245231 Vol. 191, No. 16 0021-9193/09/$08.00 0 doi:10.1128/JB.00085-09  

E-print Network

, California 946085 Received 23 January 2009/Accepted 2 June 2009 Members of the genus "Dehalococcoides in Clostridium kluyveri. Chlorinated organic compounds, such as tetrachloroethene (PCE) and trichloroethene (TCE and the environment (5, 37). To date, only bacteria of the genus "Dehalococcoides" have been shown to completely

Alvarez-Cohen, Lisa

356

Chloroethene degradation and expression of Dehalococcoides dehalogenase genes in cultures originating from Yangtze sediments.  

PubMed

The anaerobic Dehalococcoides spp. is the only microorganism known to completely dechlorinate the hazardous compounds tetrachloroethene (PCE) or trichloroethene (TCE) via dichloroethene (DCE) and vinyl chloride (VC) to the terminal product, ethene. In this study, growth of Dehalococcoides spp. (DHC) and the expression of DHC dehalogenase genes were demonstrated for Yangtze enrichment cultures. Reductive dechlorination of chloroethenes occurred in Yangtze sediment without the addition of any external auxiliary substrates. All Yangtze enrichment cultures completely dechlorinated PCE and cis-DCE to ethene. To investigate expression of the dehalogenase genes pceA, tceA, vcrA, and bvcA, a protocol for messenger RNA (mRNA) extraction followed by reverse transcription and quantitative PCR analysis was established. During dechlorination, an increase in gene copy numbers of pceA, tceA, and vcrA was observed. However, temporary formation of mRNA was only measured in the case of the dehalogenase genes tceA and vcrA. Comparison of DHC dehalogenase patterns indicated that the Yangtze DHC community does not match any of the previously published enrichment cultures that were obtained from contaminated areas in the USA or Europe. PMID:25233916

Kranzioch, Irene; Ganz, Selina; Tiehm, Andreas

2015-02-01

357

Cjestmir de Boer, Juergen Braun, Norbert Klaas, Stefan Steiert Universitt Stuttgart  

E-print Network

of the Environment, State of Baden-Württemberg, Germany Granular reactive iron (Fe0) is used in Permeable Reactive barrier. The concentration decreases rapidly from the injection point (observed in 1-D and 2-D) Column Barriers (PRB) Fe0 can reduce chlorinated hydrocarbons such as TCE and PCE Nano-scale Fe0 particles

Cirpka, Olaf Arie

358

Evaluation of a permeable reactive barrier technology for use at Rocky Flats Environmental Technology Site (RFETS)  

Microsoft Academic Search

Three reactive materials were evaluated at laboratory scale to identify the optimum treatment reagent for use in a Permeable Reactive Barrier Treatment System at Rocky Flats Environmental Technology Site (RFETS). The contaminants of concern (COCS) are uranium, TCE, PCE, carbon tetrachloride, americium, and vinyl chloride. The three reactive media evaluated included high carbon steel iron filings, an iron-silica alloy in

BRIAN P

2000-01-01

359

Groundwater contamination and risk assessment of industrial complex in Busan Metropolitan City, Korea  

Microsoft Academic Search

In Korea, the potential of groundwater contamination in urban areas is increasing by industrial and domestic waste waters, leakage from oil storage tanks and sewage drains, leachate from municipal landfill sites and so on. Nowadays, chlorinated organic compounds such as trichloroethylene (TCE) and tetrachloroethylene (PCE), which are driving residential area as well as industrial area, are recognized as major hazardous

S.-Y. Hamm; S. M. Ryu; J.-Y. Cheong; Y.-J. Woo

2003-01-01

360

Dechlorination of chlorinated hydrocarbons by bimetallic Ni/Fe immobilized on polyethylene glycol-grafted microfiltration membranes under anoxic conditions.  

PubMed

In this study, the dechlorination of chlorinated hydrocarbons including trichloroethylene (TCE), tetrachloroethylene (PCE) and carbon tetrachloride (CT) by bimetallic Ni/Fe nanoparticles immobilized on four different membranes was investigated under anoxic conditions. Effects of several parameters including the nature of membrane, initial concentration, pH value, and reaction temperature on the dechlorination efficiency were examined. The scanning electron microscopic images showed that the Ni/Fe nanoparticles were successfully immobilized inside the four membranes using polyethylene glycol as the cross-linker. The agglomeration of Ni/Fe were observed in poly(vinylidene fluoride), Millex GS and mixed cellulose ester membranes, while a relatively uniform distribution of Ni/Fe was found in nylon-66 membrane because of its hydrophilic nature. The immobilized Ni/Fe nanoparticles exhibited good reactivity towards the dechlorination of chlorinated hydrocarbons, and the pseudo-first-order rate constant for TCE dechlorination by Ni/Fe in nylon-66 were 3.7-11.7 times higher than those in other membranes. In addition, the dechlorination efficiency of chlorinated hydrocarbons followed the order TCE>PCE>CT. Ethane was the only end product for TCE and PCE dechlorination, while dichloromethane and methane were found to be the major products for CT dechlorination, clearly indicating the involvement of reactive hydrogen species in dechlorination. In addition, the initial rate constant for TCE dechlorination increased upon increasing initial TCE concentrations and the activation energy for TCE dechlorination by immobilized Ni/Fe was 34.9 kJ mol(-1), showing that the dechlorination of TCE by membrane-supported Ni/Fe nanoparticles is a surface-mediated reaction. PMID:22115467

Parshetti, Ganesh K; Doong, Ruey-an

2012-01-01

361

Induction of toluene oxidation activity in Pseudomonas mendocina KR1 and Pseudomonas sp. strain ENVPC5 by chlorinated solvents and alkanes.  

PubMed

Toluene oxidation activity in Pseudomonas mendocina KR1 and Pseudomonas sp. strain ENVPC5 was induced by trichloroethylene (TCE), and induction was followed by the degradation of TCE. Higher levels of toluene oxidation activity were achieved in the presence of a supplemental growth substrate such as glutamate, with levels of activity of up to 86% of that observed with toluene-induced cells. Activity in P. mendocina KR1 was also induced by cis-1,2-dichloroethylene, perchloroethylene, chloroethane, hexane, pentane, and octane, but not by trans-1,2-dichloroethylene. Toluene oxidation was not induced by TCE in Burkholderia (Pseudomonas) cepacia G4, P. putida F1, Pseudomonas sp. strain ENV110, or Pseudomonas sp. strain ENV113. PMID:7574658

McClay, K; Streger, S H; Steffan, R J

1995-09-01

362

SURFACE-ALTERED ZEOLITES AS PERMEABLE BARRIERS FOR IN SITU TREATMENT OF CONTAMINATED GROUNDWATER  

SciTech Connect

This report summarizes experiments to develop and test surfactant-modified zeolite/zero-valent iron (SMZ/ZVI) pellets for permeable reactive barriers to treat groundwater contamination. Coating a glass foam core with a mixture of hexadecyltrimethylammonium surfactant, zeolite, and ZVI produced a high hydraulic conductivity, mechanically stable pellet. Laboratory experiments showed that the pellets completely removed soluble chromate from aqueous solution, and reduced perchloroethylene (PCE) concentrations more than pellets that lacked surfactant. Based upon the laboratory results, they predicted a 1-m-wide SMZ/ZVI barrier that would reduce PCE concentrations by four orders of magnitude. Thirteen cubic meters (470 cubic feet) of SMZ/ZVI pellets were manufactured and emplaced in a permeable barrier test facility. A controlled plume of chromate and PCE was allowed to contact the barrier for four weeks. The entire plume was captured by the barrier. No chromate was detected downgradient of the barrier. The PCE broke through the barrier after four weeks, and downgradient concentrations ultimately exceeded 10% of the influent PCE. The less-than-expected PCE reduction was attributed to insufficient surfactant content, the large size, and pH-altering characteristics of the bulk-produced pellets. The pellets developed here can be improved to yield a performance- and cost-competitive permeable barrier material.

Robert S. Bowman; Pengfei Zhang; Xian Tao

2002-03-01

363

Multilayer fiber optic chemical sensors employing organically modified SiO2 and mixed TiO2/SiO2 sol gel membranes  

NASA Astrophysics Data System (ADS)

Fiber-optic sensors have been developed that incorporate multi-layer organically modified silica sol-gel membranes. pH sensors use a single layer hydrophilic organo-silica sol-gel membrane with a covalently attached pH sensitive dye, hydroxypyrene trisulfonic acid. The hydrophilic coating is made by copolymerizing silanol-terminated polydimethylsiloxane and tetraethylorthosilicate with 3-aminopropyltriethoxysilane. Unlike previous methods, which use acid as a catalyst, we have found that a base catalyst produces optically transparent gels. The sol-gel coated sensors are simple to make and require drying and aging times of as little as one day. Sensors made using these gels exhibit very good long-term stability, fast response times and no dye leaching. pCO2 sensors were fabricated using the same pH sensitive sol-gel layer overcoated with a hydrophobic high organic content sol- gel membrane. The response of the pH and pCO2 sensors is very fast due to the high porosity of the sol-gel membranes. Although in-situ sensors have been described for a number of organic and inorganic species, many volatile organochloride compounds (VOCs), such as perchloroethylene (PCE) and trichloroethylene (TCE), have been difficult to measure using current fiber-optic sensor transduction schemes. One of the optical sensors described here is a multilayer (3-4) sol-gel system that incorporates a TiO2/SiO2 membrane to degrade VOCs into smaller, detectable products. Upon exposure to UV light, TiO2, a semiconductor with a bandgap of 3.2 eV, produces highly reactive electron-hole pairs that are capable of photodegrading most organic compounds. The VOCs mentioned above are sensitive to degradative oxidation on TiO2 surfaces. During photodegradation of VOCs a number of products are formed including H+, HCl, CO2 and a number of smaller hydrocarbons. These products are produced in the TiO2 membrane and on TiO2 surfaces and the products diffuse into the nearby indicator membrane where they are detected. Carbon dioxide and protons produced are detected by the pH sensitive indicator layer described above. pH and CO2 sensors, and preliminary data for the measurement of VOCs will be presented.

Nivens, Delana A.; Schiza, Maria V.; Angel, S. M.

1997-05-01

364

Interplay between subsurface structural heterogeneity and multi-species reactive transport in human health risk predictions  

NASA Astrophysics Data System (ADS)

The increasing presence of toxic chemicals released in the subsurface has led to a rapid growth of social concerns and to the need to develop and employ models that can predict the impact of groundwater contamination in human health under uncertainty. Monitored natural attenuation is a common remediation action in many contamination cases and represents an attractive decontamination method. However, natural attenuation can lead to the production of subspecies of distinct toxicity that may pose challenges in pollution management strategies. The actual threat that these contaminants pose to human health and ecosystems greatly depends on the interplay between the complexity of the geological system and the toxicity of the pollutants and their byproducts. In this work, we examine the interplay between multispecies reactive transport and the heterogeneous structure of the contaminated aquifer on human health risk predictions. The structure and organization of hydraulic properties of the aquifer can lead to preferential flow channels and fast contamination pathways. Early travel times, associated to channeling effects, are intuitively perceived as an indicator for high risk. However, in the case of multi-species systems, early travel times may also lead a limited production of daughter species that may contain higher toxicity as in the case of chlorinated compounds. In this work, we model a Perchloroethylene (PCE) contamination problem followed by the sequential first-order production/biodegradation of its daughter species Trichloroethylene (TCE), Dichloroethylene (DCE) and Vinyl Chlorine (VC). For this specific case, VC is known to be a highly toxic contaminant. By performing numerical experiments, we evaluate transport for two distinct three-dimensional aquifer structures. First, a multi-Gaussian hydraulic conductivity field and secondly, a geostatistically equivalent connected field. These two heterogeneity structures will provide two distinct ranges of mean travel times and other higher order statistics. Uncertainty on the hydraulic conductivity field is considered through a Monte Carlo scheme, and the total risk (TR) for human health related to the mixtures of the four carcinogenic plumes is evaluated. Results show two distinct spatio-temporal behavior of the TR estimation. At a fixed environmentally sensitive location, aquifers with a high degree of connectivity display a lower TR. On the other hand, at the same environmentally sensitive location, the poorly connected aquifer yields higher TR. Our results reflect the interplay between the characteristic reactive time for each component and the characteristic travel time of the plume since the production of VC depends on these factors.

Henri, C.; Fernandez-Garcia, D.; de Barros, F.

2013-12-01

365

Dehalorespiration model that incorporates the self-inhibition and biomass inactivation effects of high tetrachloroethene concentrations.  

PubMed

In the vicinity of dense nonaqueous phase liquid (DNAPL) contaminant source zones, aqueous concentrations of tetrachloroethene (PCE) in groundwater may approach saturation levels. In this study, the ability of two PCE-respiring strains (Desulfuromonas michiganensis and Desulfitobacterium strain PCE1) to dechlorinate high concentrations of PCE was experimentally evaluated and depended on the initial biomass concentration. This suggests high PCE concentrations permanently inactivated a fraction of biomass, which, if sufficiently large, prevented dechlorination from proceeding. The toxic effects of PCE were incorporated into a model of dehalorespirer growth by adapting the transformation capacity concept previously applied to describe biomass inactivation by products of cometabolic TCE oxidation. The inactivation growth model was coupled to the Andrews substrate utilization model, which accounts for the self-inhibitory effects of PCE on dechlorination rates, and fit to the experimental data. The importance of incorporating biomass inactivation and self-inhibition effects when modeling reductive dechlorination of high PCE concentrations was demonstrated by comparing the goodness-of-fit of the Andrews biomass inactivation and three alternate models that do capture these factors. The new dehalorespiration model should improve our ability to predict contaminant removal in DNAPL source zones and determine the inoculum size needed to successfully implement bioaugmentation of DNAPL source zones. PMID:21182287

Huang, Deyang; Becker, Jennifer G

2011-02-01

366

Microbial degradation of chloroethenes in groundwater systems  

NASA Astrophysics Data System (ADS)

The chloroethenes, tetrachloroethene (PCE) and trichloroethene (TCE) are among the most common contaminants detected in groundwater systems. As recently as 1980, the consensus was that chloroethene compounds were not significantly biodegradable in groundwater. Consequently, efforts to remediate chloroethene-contaminated groundwater were limited to largely unsuccessful pump-and-treat attempts. Subsequent investigation revealed that under reducing conditions, aquifer microorganisms can reductively dechlorinate PCE and TCE to the less chlorinated daughter products dichloroethene (DCE) and vinyl chloride (VC). Although recent laboratory studies conducted with halorespiring microorganisms suggest that complete reduction to ethene is possible, in the majority of groundwater systems reductive dechlorination apparently stops at DCE or VC. However, recent investigations conducted with aquifer and stream-bed sediments have demonstrated that microbial oxidation of these reduced daughter products can be significant under anaerobic redox conditions. The combination of reductive dechlorination of PCE and TCE under anaerobic conditions followed by anaerobic microbial oxidation of DCE and VC provides a possible microbial pathway for complete degradation of chloroethene contaminants in groundwater systems. Résumé Les chloroéthanes, tétrachloroéthane (PCE) et trichloroéthane (TCE) sont parmi les polluants les plus communs trouvés dans les aquifères. Depuis les années 1980, on considère que les chloroéthanes ne sont pas significativement biodégradables dans les aquifères. Par conséquent, les efforts pour dépolluer les nappes contaminées par des chloroéthanes se sont limités à des tentatives de pompage-traitement globalement sans succès. Des travaux ultérieurs ont montré que dans des conditions réductrices, des micro-organismes présents dans les aquifères peuvent, par réduction, dégrader les PCE et TCE en composés moins chlorés, comme le dichloréthane (DCE) et le chlorure de vinyl (VC). Bien que des études de laboratoire réalisées avec des micro-organismes adaptés aux composés halogénés montrent que la réduction complète en éthane est possible, dans la plupart des nappes la réaction de déchloration par réduction s'arrête apparemment au DCE et au VC. Cependant, des recherches récentes menées sur des sédiments d'un aquifère et d'alluvions ont démontré que l'oxydation microbienne de ces descendants réduits peut se produire de manière significative dans des conditions de redox anérobies. La déchloration par réduction de PCE et de TCE dans des conditions anérobies suivie par une oxydation microbienne anérobie des DCE et VC fournit une piste microbienne possible pour obtenir une dégradation complète des chloroéthanes polluants dans les aquifères. Resumen Los cloroetanos (tetracloroetano PCE y tricloroetano TCE) son contaminantes muy habituales en los acuíferos. Hasta 1980 se consideraba que los cloroetanos no eran biodegradables y, por tanto, los métodos de rehabilitación en acuíferos contaminados con cloroetanos se limitaban al pump-and-treat, generalmente con poco éxito. Posteriormente se vio que, en condiciones reductoras, algunos microorganismos pueden reducir PCE y TCE a unos subproductos menos clorados, como el dicloroetano (DCE) y el cloruro de vinilo (VC). Aunque estudios de laboratorio recientes sugieren que la reducción completa a etano es posible, en la mayoría de los sistemas acuíferos la decloración suele detenerse en los DCE o VC. Sin embargo, investigaciones más recientes en acuíferos y sedimentos fluviales demuestran que la oxidación microbiana de estos subproductos puede ser importante bajo condiciones redox anaerobias. La combinación de la reducción de PCE y TCE en condiciones anaerobias seguida de la oxidación microbiana anaerobia de DCE y VC proporciona un método potencial para la degradación total de los cloroetanos en los sistemas acuíferos.

Bradley, Paul M.

367

Prenatal and Early Childhood Exposure to Tetrachloroethylene and Adult Vision  

PubMed Central

Background: Tetrachloroethylene (PCE; or perchloroethylene) has been implicated in visual impairments among adults with occupational and environmental exposures as well as children born to women with occupational exposure during pregnancy. Objectives: Using a population-based retrospective cohort study, we examined the association between prenatal and early childhood exposure to PCE-contaminated drinking water on Cape Cod, Massachusetts, and deficits in adult color vision and contrast sensitivity. Methods: We estimated the amount of PCE that was delivered to the family residence from participants’ gestation through 5 years of age. We administered to this now adult study population vision tests to assess acuity, contrast sensitivity, and color discrimination. Results: Participants exposed to higher PCE levels exhibited lower contrast sensitivity at intermediate and high spatial frequencies compared with unexposed participants, although the differences were generally not statistically significant. Exposed participants also exhibited poorer color discrimination than unexposed participants. The difference in mean color confusion indices (CCI) was statistically significant for the Farnsworth test but not Lanthony’s D-15d test [Farnsworth CCI mean difference = 0.05, 95% confidence interval (CI): 0.003, 0.10; Lanthony CCI mean difference = 0.07, 95% CI: –0.02, 0.15]. Conclusions: Prenatal and early childhood exposure to PCE-contaminated drinking water may be associated with long-term subclinical visual dysfunction in adulthood, particularly with respect to color discrimination. Further investigation of this association in similarly exposed populations is necessary. PMID:22784657

Getz, Kelly D.; Janulewicz, Patricia A.; Rowe, Susannah; Weinberg, Janice M.; Winter, Michael R.; Martin, Brett R.; Vieira, Veronica M.; White, Roberta F.

2012-01-01

368

Urban\\/industrial pollution for the New York City-Washington, D. C., corridor, 1996-1998: 2. A study of the efficacy of the Montreal Protocol and other regulatory measures  

Microsoft Academic Search

Background concentrations, emission rates, and trends in emission rates for five trace gases are inferred for the northeastern United States from continuous atmospheric observations at Harvard Forest in central New England for 1996-1998. Mixing ratios of gases regulated by the Montreal Protocol (CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2F-CClF2), CH3CCl3, and halon-1211 (CBrClF2)) are referenced to CO and PCE (perchloroethylene, tetrachloroethene,

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

2003-01-01

369

Urban\\/industrial pollution for the New York City–Washington, D. C., corridor, 1996–1998: 2. A study of the efficacy of the Montreal Protocol and other regulatory measures  

Microsoft Academic Search

Background concentrations, emission rates, and trends in emission rates for five trace gases are inferred for the northeastern United States from continuous atmospheric observations at Harvard Forest in central New England for 1996–1998. Mixing ratios of gases regulated by the Montreal Protocol (CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2F-CClF2), CH3CCl3, and halon-1211 (CBrClF2)) are referenced to CO and PCE (perchloroethylene, tetrachloroethene,

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

2003-01-01

370

Experimental and numerical investigation of DNAPL infiltration and spreading in a 2-D sandbox by means of light transmission method  

NASA Astrophysics Data System (ADS)

Chlorinated solvents such as trichloroethene (TCE) and tetrachloroethene (PCE) are widespread groundwater contaminants often referred to as dense non-aqueous phase liquids (DNAPLs). Accuracy description of the spreading behavior and configuration for subsurface DNAPL migration is important, especially favourable for design effective remediation strategies. In this study, a 2-D experiment was conducted to investigate the infiltration behavior and spatial distribution of PCE in saturated porous media. Accusand 20/30 mesh sand (Unimin, Le Sueur, MN) was used as the background medium with two 70/80 and 60/70 mesh lenses embedded to simulate heterogeneous conditions. Dyed PCE of 100 ml was released into the flow cell at a constant rate of 2ml/min using a Harvard Apparatus syringe pump with a 50 ml glass syringe for two times, and 5 ml/min water was continuously injected through the inlet at the left side of the sandbox, while kept the same effluent rate at right side to create hydrodynamic condition. A light transmission (LT) system was used to record the migration of PCE and determine the saturation distribution of PCE in the sandbox experiment with a thermoelectrically air-cooled charged-coupled device (CCD) camera. All images were processed using MATLAB to calculate thickness-averaged PCE saturation for each pixel. Mass balance was checked through comparing injected known mounts of PCE with that calculated from LT analysis. Results showed that LT method is effective to delineate PCE migration pathways and quantify the saturation distribution. The relative errors of total PCE volumes calculated by LT analysis at different times were within 15% of the injected PCE volumes. The simulation are conducted using the multiphase modeling software T2VOC, which calibrated by the LT analysis results of three recorded time steps to fit with the complete spatial-temporal distribution of the PCE saturation. Model verification was then performed using the other eight recorded time steps. Simulated results showed that the model could successfully reproduce the migration pathways and distribution configuration observed from the laboratory experiment and LT analysis, excepted for a smaller pool height on the lenses, and a lower saturation values in PCE accumulation area due to local heterogeneities. Due to the influence of water flow, the PCE distribution was asymmetrical, and the PCE distribution area, pool height as well as PCE saturation in the accumulation region at right side was much greater. Acknowledge: This work is financially supported by the National Nature Science Foundation of China grants No. 41030746 and 41172206.

Zheng, F.; Shi, X.; Wu, J.; Gao, Y. W.

2013-12-01

371

TRANSPORT OF TRICHLOROETHYLENE (TCE) IN NATURAL SOIL BY ELECTROOSMOSIS  

EPA Science Inventory

Contamination in low permeability soils poses a significant technical challenge to in-situ remediation, primarily due to low mobilization of the contaminants and difficulty in uniform delivery of treatment reagents. An alternative approach using electroosmosis (EO) is used to mob...

372

Biofouling effects on in situ TCE bioremediation by phenol utilizers  

SciTech Connect

In situ bioremediation involves stimulating the growth of bacteria within the contaminated region of an aquifer to break down the contaminants. This large bacteria population often can have the unwanted effect of clogging the porous media. The clogging reduces the porosity and the hydraulic conductivity of the soil. These hydrodynamic changes can affect the flow of groundwater used to deliver nutrients to the bacteria in the contaminated region of the aquifer. The authors developed a mathematical model to study the impact of biofouling on a recirculation well flow system used to mix nutrients with contaminated groundwater. The insights gained from this examination can aid in designing a system to minimize biofouling problems.

MacDonald, T.R.; Kitanidis, P.K. [Stanford Univ., CA (United States). Civil Engineering Dept.

1995-12-31

373

TCE REMOVAL FROM CONTAMINATED SOIL AND GROUND WATER  

EPA Science Inventory

Widespread use of trichloroethylene (TEE) in the U.S. has resulted in its frequent detection in soil and groundwater. EE 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,...

374

A review of potential neurotoxic mechanisms among three chlorinated organic solvents  

SciTech Connect

The potential for central nervous system depressant effects from three widely used chlorinated solvents, trichloroethylene (TCE), perchloroethylene (PERC), and dichloromethane (DCM), has been shown in human and animal studies. Commonalities of neurobehavioral and neurophysiological changes for the chlorinated solvents in in vivo studies suggest that there is a common mechanism(s) of action in producing resultant neurotoxicological consequences. The purpose of this review is to examine the mechanistic studies conducted with these chlorinated solvents and to propose potential mechanisms of action for the different neurological effects observed. Mechanistic studies indicate that this solvent class has several molecular targets in the brain. Additionally, there are several pieces of evidence from animal studies indicating this solvent class alters neurochemical functions in the brain. Although earlier evidence indicated that these three chlorinated solvents perturb the lipid bilayer, more recent data suggest an interaction between several specific neuronal receptors produces the resultant neurobehavioral effects. Collectively, TCE, PERC, and DCM have been reported to interact directly with several different classes of neuronal receptors by generally inhibiting excitatory receptors/channels and potentiating the function of inhibitory receptors/channels. Given this mechanistic information and available studies for TCE, DCM, and PERC, we provide hypotheses on primary targets (e.g. ion channel targets) that appear to be most influential in producing the resultant neurological effects. - Research Highlights: > Comparison of neurological effects among TCE, PERC, and DCM. > Correlation of mechanistic findings to neurological effects. > Data support that TCE, PERC, and DCM interact with several ion channels to produce neurological changes.

Bale, Ambuja S., E-mail: bale.ambuja@epa.gov; Barone, Stan; Scott, Cheryl Siegel; Cooper, Glinda S.

2011-08-15

375

SUBCHRONIC TOXICITY OF TETRACHLOROETHYLENE (PERCHLOROETHYLENE) ADMINISTERED IN THE DRINKING WATER OF RATS  

EPA Science Inventory

The study provides data on the effects of tetrachloroethylene in drinking solutions. The acute oral LD(50) was determined in male and female Charles River rats and found to be 3835 mg/kg for males and 3005 mg/kg for females. Male and female rats received theoretical daily doses o...

376

Subchronic toxicity of tetrachloroethylene (perchloroethylene) administered in the drinking water of rats  

SciTech Connect

This study provides data on the effects of tetrachloroethylene in drinking solutions. The acute oral LD50 in male and female Charles River rats was found to be 3835 mg/kg for males and 3005 mg/kg for females. Male and female rats received theoretical daily doses of 14,400, and 1400 mg tetrachloroethylene/kg body wt/day for 90 consecutive days. There were no compound-related deaths. Body weights were significantly lower in male and female rats at the higher doses. There were no consistent dose-related effects on any of the hematological, clinical chemistry, or urinalysis parameters. 5'-Nucleotidase activity was increased in a dose-dependent manner, suggesting possible hepatotoxicity; however, other serum indicators of hepatic function were unaffected by the treatment. There were no gross pathological effects observed. Liver and kidney body weight ratios, but not brain weight ratios, were elevated at the higher doses. There was no other evidence of compound-related toxicity. These data suggest that exposure of humans to reported levels of tetrachloroethylene in drinking water (approximately 1 microgram/liter) does not constitute a serious health hazard.

Hayes, J.R.; Condie, L.W. Jr.; Borzelleca, J.F.

1986-07-01

377

70 FR 75884 - National Perchloroethylene Air Emission Standards for Dry Cleaning Facilities  

Federal Register 2010, 2011, 2012, 2013, 2014

...form of encryption, and be free of any defects or viruses. For additional information...40,000 per machine, depending on the size of the existing machine and the level of control...cleaners; (2) our uncertainty of the size of the affected population; and (3)...

2005-12-21

378

r/g 2499u Form 24 for 06/03/2013 Test of PCE, PCE Antenna Feeder (), and ATV Control Panel Commands  

E-print Network

Collection 06:05-06:10 FE-3 REMINDER- read reminders 06:10-06:20 CDR,FE-2, FE-4 Calf Volume Measurement 06 36 Crew Handover 09:00-09:15 FE-5 Private Medical Conference 09:10-09:20 FE-2 URAGAN. Photo Spectral

Waliser, Duane E.

379

FY02 Final Report on Phytoremediation of Chlorinated Ethenes in Southern Sector Sediments of the Savannah River Site  

SciTech Connect

This final report details the operations and results of a 3-year Seepline Phytoremediation Project performed adjacent to Tims Branch, which is located in the Southern Sector of the Savannah River Site (SRS) A/M Area. Phytoremediation is a process where interactions between vegetation, associated microorganisms, and the host substrate combine to effectively degrade contaminated soils, sediments, and groundwater. Phytoremediation is a rapidly developing technology that shows promise for the effective and safe cleanup of certain hazardous wastes. It has the potential to remediate numerous volatile organic compounds (VOCs). Extensive characterization work has demonstrated that two VOCs, tetrachloroethylene (PCE) and trichloroethylene (TCE) are the major components of the VOC-contaminated groundwater that is migrating through the Southern Sector and Tims Branch seepline area (WSRC, 1999). The PCE and TCE are chlorinated ethenes (CE), and have been detected in seepline soils and ground water adjacent to the ecologically-sensitive Tims Branch seepline area.

Brigmon, R..L.

2004-01-30

380

Survey of subsurface treatment technologies for environmental restoration sites at Sandia National Laboratories, New Mexico.  

SciTech Connect

This report provides a survey of remediation and treatment technologies for contaminants of concern at environmental restoration (ER) sites at Sandia National Laboratories, New Mexico. The sites that were evaluated include the Tijeras Arroyo Groundwater, Technical Area V, and Canyons sites. The primary contaminants of concern at these sites include trichloroethylene (TCE), tetrachloroethylene (PCE), and nitrate in groundwater. Due to the low contaminant concentrations (close to regulatory limits) and significant depths to groundwater ({approx}500 feet) at these sites, few in-situ remediation technologies are applicable. The most applicable treatment technologies include monitored natural attenuation and enhanced bioremediation/denitrification to reduce the concentrations of TCE, PCE, and nitrate in the groundwater. Stripping technologies to remove chlorinated solvents and other volatile organic compounds from the vadose zone can also be implemented, if needed.

McGrath, Lucas K.; Ho, Clifford Kuofei; Wright, Jerome L.

2003-08-01

381

Microbial based chlorinated ethene destruction  

DOEpatents

A mixed culture of Dehalococcoides species is provided that has an ability to catalyze the complete dechlorination of polychlorinated ethenes such as PCE, TCE, cDCE, 1,1-DCE and vinyl chloride as well as halogenated ethanes such as 1,2-DCA and EDB. The mixed culture demonstrates the ability to achieve dechlorination even in the presence of high source concentrations of chlorinated ethenes.

Bagwell, Christopher E. (Aiken, SC); Freedman, David L. (Clemson, SC); Brigmon, Robin L. (North Augusta, SC); Bratt, William B. (Atlanta, GA); Wood, Elizabeth A. (Marietta, GA)

2009-11-10

382

Reduction of trichloroethylene in a model aquifer with methanotrophic bacteria  

E-print Network

for Methane Mineralization by Methanotrophic Bacteria ? Enzyme Reactions are a) Methane Monooxygenase, b) Methanol Dehydrogenase, c) Formaldehyde Dehydrogenase, d) Formate Dchydrogenase (Adapted From Dalton and Leak, 1985) . . . . . 9 FIG. 4 Proposed... was found. Apparently, reductive dechlorinazation by anaerobic bacteria was converting PCE and TCE to more hazardous chemicals in a natural environment. Purely aerobic methods appeared to require an aromatic compound such as phenol to oxidize low...

Hicks, Duane Dee

1990-01-01

383

Characterization of microbial community structure and population dynamics of tetrachloroethene-dechlorinating tidal mudflat communities.  

PubMed

Tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants that also impact tidal flats, especially near urban and industrial areas. However, very little is known about dechlorinating microbial communities in tidal flats. Titanium pyrosequencing, 16S rRNA gene clone libraries, and dechlorinator-targeted quantitative real-time PCR (qPCR) characterized reductive dechlorinating activities and populations in tidal flat sediments collected from South Korea's central west coast near Kangwha. In microcosms established with surface sediments, PCE dechlorination to TCE began within 10 days and 100% of the initial amount of PCE was converted to TCE after 37 days. cis-1,2-Dichloroethene (cis-DCE) was observed as dechlorination end product in microcosms containing sediments collected from deeper zones (i.e., 35-40 cm below ground surface). Pyrosequencing of bacterial 16S rRNA genes and 16S rRNA gene-targeted qPCR results revealed Desulfuromonas michiganensis-like populations predominanted in both TCE and cis-DCE producing microcosms. Other abundant groups included Desulfuromonas thiophila and Pelobacter acidigallici-like populations in the surface sediment microcosms, and Desulfovibrio dechloracetivorans and Fusibacter paucivorans-like populations in the deeper sediment microcosms. Dehalococcoides spp. populations were not detected in these sediments before and after incubation with PCE. The results suggest that tidal flats harbor novel, salt-tolerant dechlorinating populations and that titanium pyrosequencing provides more detailed insight into community structure dynamics of the dechlorinating microcosms than conventional 16S rRNA gene sequencing or fingerprinting methods. PMID:21053056

Lee, Jaejin; Lee, Tae Kwon; Löffler, Frank E; Park, Joonhong

2011-07-01

384

Phytoscreening for chlorinated solvents using rapid in vitro SPME sampling: Application to urban plume in Verl, Germany  

USGS Publications Warehouse

Rapid detection and delineation of contaminants in urban settings is critically important in protecting human health. Cores from trees growing above a plume of contaminated groundwater in Verl, Germany, were collected in 1 day, with subsequent analysis and plume mapping completed over several days. Solid-phase microextraction (SPME) analysis was applied to detect tetrachloroethene (PCE) and trichloroethene (TCE) to below nanogram/liter levels in the transpiration stream of the trees. The tree core concentrations showed a clear areal correlation to the distribution of PCE and TCE in the groundwater. Concentrations in tree cores were lower than the underlying groundwater, as anticipated; however, the tree core water retained the PCE:TCE signature of the underlying groundwater in the urban, populated area. The PCE:TCE ratio can indicate areas of differing degradation activity. Therefore, the phytoscreening analysis was capable not only of mapping the spatial distribution of groundwater contamination but also of delineating zones of potentially differing contaminant sources and degradation. The simplicity of tree coring and the ability to collect a large number of samples in a day with minimal disruption or property damage in the urban setting demonstrates that phytoscreening can be a powerful tool for gaining reconnaissance-level information on groundwater contaminated by chlorinated solvents. The use of SPME decreases the detection level considerably and increases the sensitivity of phytoscreening as an assessment, monitoring, and phytoforensic tool. With rapid, inexpensive, and noninvasive methods of detecting and delineating contaminants underlying homes, as in this case, human health can be better protected through screening of broader areas and with far faster response times. ?? 2011 American Chemical Society.

Limmer, M.A.; Balouet, J.-C.; Karg, F.; Vroblesky, D.A.; Burken, J.G.

2011-01-01

385

R & D Project: Permeable reactive barrier (PRB) in Rheine - latest results  

Microsoft Academic Search

As part of an R&D Project, Mull und Partner Ingenieurgesellschaft mbH (M&P) is operating a full-scale permeable reactive barrier (PRB) in Rheine with two different reactive iron media. The measured results during the first months of operation revealed a significant reduction in the contaminants PCE, TCE and cis-1,2-DCE. The initial significant generation of hydrogen is increasingly compensated by microbial activity

M. Ebert; W. Möller; M. Wegner

386

Phytoscreening for chlorinated solvents using rapid in vitro SPME sampling: application to urban plume in Verl, Germany.  

PubMed

Rapid detection and delineation of contaminants in urban settings is critically important in protecting human health. Cores from trees growing above a plume of contaminated groundwater in Verl, Germany, were collected in 1 day, with subsequent analysis and plume mapping completed over several days. Solid-phase microextraction (SPME) analysis was applied to detect tetrachloroethene (PCE) and trichloroethene (TCE) to below nanogram/liter levels in the transpiration stream of the trees. The tree core concentrations showed a clear areal correlation to the distribution of PCE and TCE in the groundwater. Concentrations in tree cores were lower than the underlying groundwater, as anticipated; however, the tree core water retained the PCE:TCE signature of the underlying groundwater in the urban, populated area. The PCE:TCE ratio can indicate areas of differing degradation activity. Therefore, the phytoscreening analysis was capable not only of mapping the spatial distribution of groundwater contamination but also of delineating zones of potentially differing contaminant sources and degradation. The simplicity of tree coring and the ability to collect a large number of samples in a day with minimal disruption or property damage in the urban setting demonstrates that phytoscreening can be a powerful tool for gaining reconnaissance-level information on groundwater contaminated by chlorinated solvents. The use of SPME decreases the detection level considerably and increases the sensitivity of phytoscreening as an assessment, monitoring, and phytoforensic tool. With rapid, inexpensive, and noninvasive methods of detecting and delineating contaminants underlying homes, as in this case, human health can be better protected through screening of broader areas and with far faster response times. PMID:21848303

Limmer, Matt A; Balouet, Jean-Christophe; Karg, Frank; Vroblesky, Don A; Burken, Joel G

2011-10-01

387

Sustainable remediation: electrochemically assisted microbial dechlorination of tetrachloroethene-contaminated groundwater.  

PubMed

Microbial electric systems (MESs) hold significant promise for the sustainable remediation of chlorinated solvents such as tetrachlorethene (perchloroethylene, PCE). Although the bio-electrochemical potential of some specific bacterial species such as Dehalcoccoides and Geobacteraceae have been exploited, this ability in other undefined microorganisms has not been extensively assessed. Hence, the focus of this study was to investigate indigenous and potentially bio-electrochemically active microorganisms in PCE-contaminated groundwater. Lab-scale MESs were fed with acetate and carbon electrode/PCE as electron donors and acceptors, respectively, under biostimulation (BS) and BS-bioaugmentation (BS-BA) regimes. Molecular analysis of the indigenous groundwater community identified mainly Spirochaetes, Firmicutes, Bacteroidetes, and ? and ?-Proteobacteria. Environmental scanning electron photomicrographs of the anode surfaces showed extensive indigenous microbial colonization under both regimes. This colonization and BS resulted in 100% dechlorination in both treatments with complete dechlorination occurring 4 weeks earlier in BS-BA samples and up to 11.5??A of current being generated. The indigenous non-Dehalococcoides community was found to contribute significantly to electron transfer with ?61% of the current generated due to their activities. This study therefore shows the potential of the indigenous non-Dehalococcoides bacterial community in bio-electrochemically reducing PCE that could prove to be a cost-effective and sustainable bioremediation practice. PMID:24119162

Patil, Sayali S; Adetutu, Eric M; Rochow, Jacqueline; Mitchell, James G; Ball, Andrew S

2014-01-01

388

Sustainable remediation: electrochemically assisted microbial dechlorination of tetrachloroethene-contaminated groundwater  

PubMed Central

Microbial electric systems (MESs) hold significant promise for the sustainable remediation of chlorinated solvents such as tetrachlorethene (perchloroethylene, PCE). Although the bio-electrochemical potential of some specific bacterial species such as Dehalcoccoides and Geobacteraceae have been exploited, this ability in other undefined microorganisms has not been extensively assessed. Hence, the focus of this study was to investigate indigenous and potentially bio-electrochemically active microorganisms in PCE-contaminated groundwater. Lab-scale MESs were fed with acetate and carbon electrode/PCE as electron donors and acceptors, respectively, under biostimulation (BS) and BS-bioaugmentation (BS-BA) regimes. Molecular analysis of the indigenous groundwater community identified mainly Spirochaetes, Firmicutes, Bacteroidetes, and ? and ?-Proteobacteria. Environmental scanning electron photomicrographs of the anode surfaces showed extensive indigenous microbial colonization under both regimes. This colonization and BS resulted in 100% dechlorination in both treatments with complete dechlorination occurring 4 weeks earlier in BS-BA samples and up to 11.5 ?A of current being generated. The indigenous non-Dehalococcoides community was found to contribute significantly to electron transfer with ?61% of the current generated due to their activities. This study therefore shows the potential of the indigenous non-Dehalococcoides bacterial community in bio-electrochemically reducing PCE that could prove to be a cost-effective and sustainable bioremediation practice. PMID:24119162

Patil, Sayali S; Adetutu, Eric M; Rochow, Jacqueline; Mitchell, James G; Ball, Andrew S

2014-01-01

389

Anaerobic reductive dechlorination of tetrachloroethene: how can dual Carbon-Chlorine isotopic measurements help elucidating the underlying reaction mechanism?  

NASA Astrophysics Data System (ADS)

Chlorinated ethenes (CEs) such as tetrachloroethene (PCE) are common persistent groundwater contaminants. Among clean-up strategies applied to sites affected by such pollution, bioremediation has been considered with a growing interest as it represents a cost-effective, environmental friendly approach. This technique however sometimes leads to an incomplete and slow biodegradation of CEs resulting in an accumulation of toxic metabolites. Understanding the reaction mechanisms underlying anaerobic reductive dechlorination would thus help assessing PCE biodegradation in polluted sites. Stable isotope analysis can provide insight into reaction mechanisms. For chlorinated hydrocarbons, carbon (C) and chlorine (Cl) isotope data (?13C and ?37Cl) tend to show a linear correlation with a slope (m ? ?C/?Cl) characteristic of the reaction mechanism [1]. This study hence aims at exploring the potential of a dual C-Cl isotope approach in the determination of the reaction mechanisms involved in PCE reductive dechlorination. C and Cl isotope fractionation were investigated during anaerobic PCE dechlorination by two bacterial consortia containing members of the Sulfurospirillum genus. The specificity in these consortia resides in the fact that they each conduct PCE reductive dechlorination catalysed by one different reductive dehalogenase, i.e. PceADCE which yields trichloroethene (TCE) and cis-dichloroethene (cDCE), and PceATCE which yields TCE only. The bulk C isotope enrichment factors were -3.6±0.3 o for PceATCE and -0.7±0.1o for PceADCE. The bulk Cl isotope enrichment factors were -1.3±0.2 o for PceATCE and -0.9±0.1 o for PceADCE. When applying the dual isotope approach, two m values of 2.7±0.1 and 0.7±0.2 were obtained for the reductive dehalogenases PceATCE and PceADCE, respectively. These results suggest that PCE can be degraded according to two different mechanisms. Furthermore, despite their highly similar protein sequences, each reductive dehalogenase seems to catalyse PCE reductive dechlorination according to a different mechanism. In another study, an m value of 2.5±0.8 was found for PCE anaerobic dechlorination by a bacterial consortium dominated by species closely related to Desulfitobacterium aromaticivorans strain UKTL (consortia A) [2]. This value is indistinguishable from the one found for PceATCE within a 95% confidence interval although the reductive dehalogenase protein sequence of consortia A is distinctly different from the sequences of our two cultures. This suggests that the reaction mechanism is not related to the similarities between reductive dehalogenases. References 1. Abe, Y., et al., Carbon and Chlorine Isotope Fractionation during Aerobic Oxidation and Reductive Dechlorination of Vinyl Chloride and cis-1,2-Dichloroethene. Environmental Science & Technology, 2009. 43(1): p. 101-107. 2. Wiegert, C., et al., Carbon and Chlorine Isotope Fractionation During Microbial Degradation of Tetra- and Trichloroethene. Environmental Science & Technology, 2013. 47(12): p. 6449-6456.

Badin, Alice; Buttet, Géraldine; Maillard, Julien; Holliger, Christof; Hunkeler, Daniel

2014-05-01

390

Uptake and fate of organohalogens from contaminated groundwater in woody plants  

SciTech Connect

The emerging technology of phytoremediation uses green plants for low-cost, low-tech remediation processes in which selected plants and natural or engineered microorganisms work together to metabolize, convert, absorb, accumulate, sequester, or otherwise render harmless multiple environmental contaminants. For many organic contaminants, such as tricholoroethylene (TCE) and tetrachloroethylene (PCE), there is evidence that plants can degrade a portion of the organohalogen that is taken up to form less volatile compounds, such as trichloroacetic acid (TCAA), which are sequestered in the plant tissue while the remainder is passed out of the leaf tissue with the transpiration stream. Analysis of leaves from trees in uncontaminated areas gives TCAA concentrations that are typically under 100 ng/g TCAA, while in contaminated areas concentrations run as high as 1,000 ng/g. Hybrid poplar plants fed by TCE- and PCE-spiked nutrient solutions in a greenhouse showed elevated TCAA levels in the leaves within a week, as well as evidence for evapotranspiration of the TCE and PCE.

Sytsma, L.; Mulder, J.; Schneider, J. [Argonne National Lab., IL (United States)] [and others

1997-12-31

391

Use of Mini-Sprinklers to Strip Trichloroethylene and Tetrachloroethylene from Contaminated Ground Water.  

SciTech Connect

Berisford, Y.C., P.B. Bush, J.I. Blake, and C.L. Bayer. 2003. Use of mini-sprinklers to strip trichloroethylene and tetrachloroethylene from contaminated ground water. J. Env. Qual. 32:801-815. Three low-volume mini-sprinklers were tested for their efficacy to strip trichloroethylene (TCE) and tetrachloroethylene (PCE) from water. Deionized water spiked with TCE and PCE was pumped through a mini-sprinkler supported on top of a 1.8-m-tall. Water was collected in collection vessels at 0.61 and 1.22 m above the ground on support columns that were spaced at 0.61-m intervals from the riser base, and samples were composited per height and distance from the riser. Overall, air-stripping reduced dissolved concentrations of TCE and PCE by 99.1 to 100 and 96.9 to 100%, respectively. Mini-sprinklers offer the advantages of (i) easy setup in series that can be used on practically any terrain; (ii) operation over a long period of time that does not threaten aquifer depletion; (iii) use in small or confined aquifers in which the capacity is too low to support large irrigation or pumping systems; and (iv) use in forests in which the small, low-impact droplets of the mini-sprinklers do not damage bark and in which trees can help manage (via evapotransporation) excess waste water.

Brerisford, Yvette, C.; Bush, Parshall, B.; Blake, John, I.; Bayer, Cassandra L.

2003-01-01

392

Natural attenuation of chlorinated solvents at Area 6, Dover Air Force Base: Groundwater biogeochemistry  

USGS Publications Warehouse

Monitored natural attenuation (MNA) has recently emerged as a viable groundwater remediation technology in the United States. Area 6 at Dover Air Force Base (Dover, DE) was chosen as a test site to examine the potential for MNA of tetrachloroethene (PCE) and trichloroethene (TCE) in groundwater and aquifer sediments. A "lines of evidence" approach was used to document the occurrence of natural attenuation. Chlorinated hydrocarbon and biogeochemical data were used to develop a site-specific conceptual model where both anaerobic and aerobic biological processes are responsible for the destruction of PCE, TCE, and daughter metabolites. An examination of groundwater biogeochemical data showed a region of depleted dissolved oxygen with elevated dissolved methane and hydrogen concentrations. Reductive dechlorination likely dominated in the anaerobic portion of the aquifer where PCE and TCE levels were observed to decrease with a simultaneous increase in cis-1,2-dichloroethene (cis-DCE), vinyl chloride (VC), ethene, and dissolved chloride. Near the anaerobic/aerobic interface, concentrations of cis-DCE and VC decreased to below detection limits, presumably due to aerobic biotransformation processes. Therefore, the contaminant and daughter product plumes present at the site appear to have been naturally attenuated by a combination of active anaerobic and aerobic biotransformation processes. ?? 2002 Elsevier Science B.V. All rights reserved.

Witt, M.E.; Klecka, G.M.; Lutz, E.J.; Ei, T.A.; Grosso, N.R.; Chapelle, F.H.

2002-01-01

393

Comparative analysis of risk-based cleanup levels and associated remediation costs using linearized multistage model (cancer slope factor) vs. threshold approach (reference dose) for three chlorinated alkenes  

SciTech Connect

The chlorinated alkenes 1,1-dichloroethene (1,1-DCE), tetrachloroethene (PCE), and trichloroethene (TCE) are common environmental contaminants found in soil and groundwater at hazardous waste sites. Recent assessment of data from epidemiology and mechanistic studies indicates that although exposure to 1,1-DCE, PCE, and TCE causes tumor formation in rodents, it is unlikely that these chemicals are carcinogenic to humans. Nevertheless, many state and federal agencies continue to regulate these compounds as carcinogens through the use of the linearized multistage model and resulting cancer slope factor (CSF). The available data indicate that 1,1-DCE, PCE, and TCE should be assessed using a threshold (i.e., reference dose [RfD]) approach rather than a CSF. This paper summarizes the available metabolic, toxicologic, and epidemiologic data that question the use of the linear multistage model (and CSF) for extrapolation from rodents to humans. A comparative analysis of potential risk-based cleanup goals (RBGs) for these three compounds in soil is presented for a hazardous waste site. Goals were calculated using the USEPA CSFs and using a threshold (i.e., RfD) approach. Costs associated with remediation activities required to meet each set of these cleanup goals are presented and compared.

Lawton, L.J. [Geraghty and Miller, Inc., Andover, MA (United States); Mihalich, J.P. [Geraghty and Miller, Inc., Langhorne, PA (United States)

1995-12-31

394

Permeable Adsorptive Barrier (PAB) for the remediation of groundwater simultaneously contaminated by some chlorinated organic compounds.  

PubMed

In this paper, a Permeable Reactive Barrier (PRB) made with activated carbon, namely a Permeable Adsorptive Barrier (PAB), is put forward as an effective technique for the remediation of aquifers simultaneously contaminated by some chlorinated organic compounds. A design procedure, based on a computer code and including different routines, is presented as a tool to accurately describe mass transport within the aquifer and adsorption/desorption phenomena occurring inside the barrier. The remediation of a contaminated aquifer near a solid waste landfill in the district of Napoli (Italy), where Tetrachloroethylene (PCE) and Trichloroethylene (TCE) are simultaneously present, is considered as a case study. A complete hydrological and geotechnical site characterization, as well as a number of dedicated adsorption laboratory tests for the determination of activated carbon PCE/TCE adsorption capacity in binary systems, are carried out to support the barrier design. By means of a series of numerical simulations it is possible to determine the optimal barrier location, orientation and dimensions. PABs appear to be an effective remediation tool for the in-situ treatment of an aquifer contaminated by PCE and TCE simultaneously, as the concentration of both compounds flowing out of the barrier is everywhere lower than the regulatory limits on groundwater quality. PMID:24747934

Erto, A; Bortone, I; Di Nardo, A; Di Natale, M; Musmarra, D

2014-07-01

395

Effects of land use on the spatial distribution of trace metals and volatile organic compounds in urban groundwater, Seoul, Korea  

NASA Astrophysics Data System (ADS)

To investigate the urban groundwater contamination by eight trace metals and 69 volatile organic compounds (VOCs) in relation to land use in Seoul, a total of 57 groundwater samples collected from wells were examined using a non-parametric statistical analysis. Land use was classified into five categories: less-developed, residential, agricultural, traffic, and industrial. A comparison of analyzed data with US EPA and Korean standards for drinking water showed that some metals and VOCs exceeded the standards in a few localities, such as Fe ( N=5), Mn ( N=6), Cu ( N=1), TCE ( N=6), PCE ( N=8), 1,2-DCA ( N=1), and 1,2-dichloropropane ( N=1). Among the 69 investigated VOCs, 19 compounds such as some gasoline-related compounds (e.g., toluene) and chlorinated compounds (e.g., chloroform, PCE, TCE) were detected in groundwater. Non-parametric statistical analysis showed that the concentrations of most trace metals (Fe, Mn, As, Cr, Pb, Cd) and some VOCs (especially, TCE, PCE, chloroform; toluene, carbon tetrachloride, bromodichloromethane, CFC113) are significantly higher in the industrial, residential, and traffic areas ( P<0.05), indicating that anthropogenic contamination of urban groundwater by those chemicals is growing. Those chemicals can be used as effective indicators of anthropogenic contamination of groundwater in urban areas and therefore a special attention is warranted for a safe water supply in those areas. The results of this study suggest that urban groundwater quality in urban areas is closely related with land use.

Park, Seong-Sook; Kim, Soon-Oh; Yun, Seong-Taek; Chae, Gi-Tak; Yu, Soon-Young; Kim, Seungki; Kim, Young

2005-10-01

396

Insights into the use of time-lapse GPR data as observations for inverse multiphase flow simulations of DNAPL migration  

USGS Publications Warehouse

Perchloroethylene (PCE) saturations determined from GPR surveys were used as observations for inversion of multiphase flow simulations of a PCE injection experiment (Borden 9??m cell), allowing for the estimation of optimal bulk intrinsic permeability values. The resulting fit statistics and analysis of residuals (observed minus simulated PCE saturations) were used to improve the conceptual model. These improvements included adjustment of the elevation of a permeability contrast, use of the van Genuchten versus Brooks-Corey capillary pressure-saturation curve, and a weighting scheme to account for greater measurement error with larger saturation values. A limitation in determining PCE saturations through one-dimensional GPR modeling is non-uniqueness when multiple GPR parameters are unknown (i.e., permittivity, depth, and gain function). Site knowledge, fixing the gain function, and multiphase flow simulations assisted in evaluating non-unique conceptual models of PCE saturation, where depth and layering were reinterpreted to provide alternate conceptual models. Remaining bias in the residuals is attributed to the violation of assumptions in the one-dimensional GPR interpretation (which assumes flat, infinite, horizontal layering) resulting from multidimensional influences that were not included in the conceptual model. While the limitations and errors in using GPR data as observations for inverse multiphase flow simulations are frustrating and difficult to quantify, simulation results indicate that the error and bias in the PCE saturation values are small enough to still provide reasonable optimal permeability values. The effort to improve model fit and reduce residual bias decreases simulation error even for an inversion based on biased observations and provides insight into alternate GPR data interpretations. Thus, this effort is warranted and provides information on bias in the observation data when this bias is otherwise difficult to assess. ?? 2006 Elsevier B.V. All rights reserved.

Johnson, R.H.; Poeter, E.P.

2007-01-01

397

Stable carbon isotope evidence for intrinsic bioremediation of tetrachloroethene and trichloroethene at area 6, Dover Air Force Base.  

PubMed

Area 6 at Dover Air Force Base (Dover, DE) has been the location of an in-depth study by the RTDF (Remediation Technologies Development Forum Bioremediation of Chlorinated Solvents Action Team) to evaluate the effectiveness of natural attenuation of chlorinated ethene contamination in groundwater. Compound-specific stable carbon isotope measurements for dissolved PCE and TCE in wells distributed throughout the anaerobic portion of the plume confirm that stable carbon isotope values are isotopically enriched in 13C consistent with the effects of intrinsic biodegradation. During anaerobic microbial reductive dechlorination of chlorinated hydrocarbons, the light (12C) versus heavy isotope (13C) bonds are preferentially degraded, resulting in isotopic enrichment of the residual contaminant in 13C. To our knowledge, this study is the first to provide definitive evidence for reductive dechlorination of chlorinated hydrocarbons at a field site based on the delta13C values of the primary contaminants spilled at the site, PCE and TCE. For TCE, downgradient wells show delta13C values as enriched as -18.0/1000 as compared to delta13C values for TCE in the source zone of -25.0 to -26.0/1000. The most enriched delta13C value on the site was observed at well 236, which also contains the highest concentrations of cis-DCE, VC, and ethene, the daughter products of reductive dechlorination. Stable carbon isotope signatures are used to quantify the relative extent of biodegradation between zones of the contaminant plume. On the basis of this approach, it is estimated that TCE in downgradient well 236 is more than 40% biodegraded relative to TCE in the proposed source area. PMID:11347596

Sherwood Lollar, B; Slater, G F; Sleep, B; Witt, M; Klecka, G M; Harkness, M; Spivack, J

2001-01-15

398

HEALTH RISK ASSESSMENT OF PCE EMISSIONS FROM DRY CLEANING ACTIVITIES IN FRANCE  

E-print Network

, A CICOLELLA1 1 National Institute for Industrial Environment and Risks, parc technologique ALATA, BP 2, 60550 is based on the human risk assessment process formalised in 1983 by the National Research Council (NRC) of the American National Academy of Sciences (NAS). It aims, within a structured and transparent framework

Paris-Sud XI, Université de

399

Business-driven PCE for inter-carrier QoS connectivity services  

Microsoft Academic Search

New value added services such as gaming on demand, premium VoIP and videoconferencing and cloud computing services impose strong Quality of Service guarantee requirement. However, ensure such a Quality of Service through multiple carriers, remains a challenge for Network Service Providers, particularly, when confidentiality issues and business policies are involved. In this paper, we discuss a novel bottom-up approach which

Nabil Bachir Djarallah; Helia Pouyllau

2011-01-01

400

Numerical Simulation of the Anaerobic Transformation of Tetrachloroethene to cis-Dichloroethene in a Continuous Flow Aquifer Column  

NASA Astrophysics Data System (ADS)

The anaerobic reductive dechlorination of tetrachloroethene (PCE) to cis-dichloroethene (c-DCE) in a laboratory column study was numerically simulated and compared with experimental observations. The column study was conducted with continuous flow and injection of PCE in synthetic groundwater. The column was packed with aquifer solids from the Hanford DOE site and bioaugmented with the Evanite (EV) dechlorinating enrichment culture. After the column was bioaugmented and fed lactate as an electron donor, c-DCE concentrations in the column effluent exceeded the influent PCE concentration. This high c-DCE concentration resulted from enhanced PCE desorption and transformation. A 1-D reactive transport model was developed that included the processes of dispersion, advection, rate-limited sorption and desorption, reductive dechlorination kinetics with competitive inhibition and microbial growth and decay. The model was validated by mass balances, comparisons with analytical solutions and batch kinetic models. Previously determined kinetic and inhibition constants for the EV culture of Yu and Semprini (2004) were input into the model simulations. Initial biomass concentration was assumed to be exponentially distributed along the column. The sorption parameters including the aquifer: water distribution coefficients (Kds) and first-order mass transfer coefficients for PCE, trichloroethene (TCE), and c-DCE were determined in batch laboratory studies. The system of model equations was solved numerically using COMSOL 3.3, which employs finite-element methods. The reactive transport model successfully simulated the initial results of continuous flow column experiment. The increase in c-DCE above the influent PCE concentration was simulated and TCE was shown not to accumulate in the column effluent. The simulations showed that microbial kinetic values generated in previous studies and the sorption parameters generated in batch tests, when used in a transport model, did a reasonable job estimating PCE, TCE, and c-DCE concentration histories in the column effluent. Currently a sensitivity analysis is being performed to better understand why some differences, such as the more rapid breakthrough of c-DCE, was observed in the experimental data, but not in the model simulations.

Mustafa, N.; Azizian, M.; Dolan, M.; Semprini, L.

2007-12-01

401

Lowering temperature to increase chemical oxidation efficiency: the effect of temperature on permanganate oxidation rates of five types of well defined organic matter, two natural soils, and three pure phase products.  

PubMed

In situ chemical oxidation (ISCO) is a soil remediation technique to remove organic pollutants from soil and groundwater with oxidants, like KMnO4. However, also natural organic compounds in soils are being oxidized, which makes the technique less efficient. Laboratory experiments were performed to investigate the influence of temperature on this efficiency, through its effect on the relative oxidation rates - by permanganate - of natural organic compounds and organic pollutants at 16 and 15°C. Specific types of organic matter used were cellulose, oak wood, anthracite, reed - and forest peat, in addition to two natural soils. Dense Non-Aqueous Phase Liquid-tetrachloroethene (DNAPL-PCE), DNAPL trichloroethene (DNAPL-TCE) and a mixture of DNAPL-PCE, -TCE and -hexachlorobutadiene were tested as pollutants. Compared to 16°C, oxidation was slower at 5°C for the specific types of organic matter and the natural soils, with exception of anthracite, which was unreactive. The oxidation rate of DNAPL TCE was lower at 5°C too. However, at this temperature oxidation was fast, implying that no competitive loss to natural organic compounds will be expected in field applications by lowering temperature. Oxidation of DNAPL-PCE and PCE in the mixture proceeded at equal rates at both temperatures, due to the dissolution rate as limiting factor. These results show that applying permanganate ISCO to DNAPL contamination at lower temperatures will limit the oxidation of natural organic matter, without substantially affecting the oxidation rate of the contaminant. This will make such remediation more effective and sustainable in view of protecting natural soil quality. PMID:24974015

de Weert, J P A; Keijzer, T J S; van Gaans, P F M

2014-12-01

402

Enhanced utilization of oxidants for in situ chemical oxidation of chlorinated and aromatic hydrocarbons  

NASA Astrophysics Data System (ADS)

Potentially viable strategies were sought for enhanced utilization of potassium permanganate (KMnO4) and Fenton's reagent during in situ chemical oxidation (ISCO). An innovative concept of controlled release of oxidant was introduced and organic-coated, completely or partially microencapsulated KMnO4 (MEPP) particles (874 +/- 377 mum) were created to serve a material that can be specifically targeted to a contaminant source zone. Paraffin wax was employed as the coating material because it is biodegradable, inert to KMnO4, insoluble in water and yet soluble in hydrophobic contaminants such as perchloroethylene (PCE). KMnO4 was released very slowly into water, but the oxidant was rapidly released into PCE. The estimated times for 90% release of the oxidant were 1.6 months, 19.3 years, and 472 years for paraffin wax to KMnO4 mass ratios of 1:1, 2:1 and 5:1, respectively. The MEPP particles preferentially accumulated at the PCE-water interface, and the KMnO4 was rapidly released into PCE (<3 min) as the paraffin wax completely dissolved. These findings suggest that enhanced contact between the target contaminant and the locally high concentrations of KMnO 4 could be achieved at the interfacial region between PCE and water. Fenton's oxidative destruction was investigated for aromatic hydrocarbons (benzene, toluene, ethylbenzene, and o-xylene; BTEX) present as dissolved and adsorbed phases, and chlorinated hydrocarbon (PCE) present mostly as dense non-aqueous phase liquid (DNAPL) (>93% of total PCE mass) in batch reactors (soil: solution = 1 g/L). An enhanced mass removal was observed by combining 300 mM H2O2, 2 mM Fe(III) and 2 mM N-(2-hydroxyethyl)iminodiacetic acid (HEIDA) at near-neutral pH. The PCE degradation was maximal at 600 mM H2O2, 5 mM Fe(III) and 5 mM HEIDA at pH 3. The observed BTEX mass removal rate constants (3.6--7.8 x 10-4 s-1) were compared to the estimated ones (4.1--10.1 x 10-3 s-1) using a semi-quantitative kinetic model. The model sensitivity analyses indicate that iron oxides and soil organic matter could play important roles in the non-specific losses of both H 2O2 and ·OH. These findings suggest that system design could be optimized with respect to process variables in remediation of contaminated soils and groundwater with Fenton's reagent.

Kang, Namgoo

403

Probabilistic Health Risk Assessment of Chemical Mixtures: Importance of Travel Times and Connectivity  

NASA Astrophysics Data System (ADS)

Subsurface contamination cases giving rise to groundwater pollutions are extensively found in all industrialized countries. Under this pressure, risk assessment methods play an important role in population protection by (1) quantifying the potential impact on human health of an aquifer contamination and (2) helping and driving decisions of groundwater-resource managers. Many reactive components such as chlorinated solvents or nitrates potentially experience attenuation processes under common geochemical conditions. This represents an attractive and extensively used remediation solution but leads often to the production of by-products before to reach a harmless chemical form. This renders mixtures of contaminants a common issue for groundwater resources managers. In this case, the threat posed by these contaminants to human health at a given sensitive location greatly depends on the competition between reactive and advective-dispersive characteristic times. However, hydraulic properties of the aquifer are known to be spatially variable, which can lead to the formation of preferential flow channels and fast contamination pathways. Therefore, the uncertainty on the spatial distribution of the aquifer properties controlling the plume travel time may then play a particular role in the human health risk assessment of chemical mixtures. We investigate here the risk related to a multispecies system in response to different degrees of heterogeneity of the hydraulic conductivity (K or Y =ln(K)). This work focuses on a Perchloroethylene (PCE) contamination problem followed by the sequential first-order production/biodegradation of its daughter species Trichloroethylene (TCE), Dichloroethylene (DCE) and Vinyl Chlorine (VC). For this specific case, VC is known to be a highly toxic contaminant. By performing numerical experiments, we evaluate transport through three-dimensional mildly (?Y 2=1.0) and highly (?Y 2=4.0) heterogeneous aquifers. Uncertainty on the hydraulic conductivity field is considered through a Monte Carlo scheme, and statistics of the total risk for human health (RT) related to the mixtures of the four carcinogenic plumes are evaluated. Results show two distinct spatiotemporal behavior of the RT estimation. Simulations in highly heterogeneous aquifers display a lower mean of RT close to the injection and higher further away. We explain this by the distinct ranges of travel times and connectivity metrics related to the two sets of aquifers. A high ?Y 2 trends to decrease the travel time (and increase the connectivity). Early travel times, associated to channeling effects, are intuitively perceived as an indicator for high risk. However, in our case, early travel times lead a limited production of highly toxic daughter species and a lower total risk. Our results reflect then the interplay between the characteristic reactive time for each component and the characteristic travel time of the plume since the production of VC depends on these factors.

Henri, Christopher V.; Fernàndez-Garcia, Daniel; de Barros, Felipe P. J.

2014-05-01

404

Assessment of subsurface chlorinated solvent contamination using tree cores at the front street site and a former dry cleaning facility at the Riverfront Superfund site, New Haven, Missouri, 1999-2003  

USGS Publications Warehouse

Tree-core sampling has been a reliable and inexpensive tool to quickly assess the presence of shallow (less than about 30 feet deep) tetrachloroethene (PCE) and trichloroethene (TCE) contamination in soils and ground water at the Riverfront Superfund Site. This report presents the results of tree-core sampling that was successfully used to determine the presence and extent of chlorinated solvent contamination at two sites, the Front Street site (operable unit OU1) and the former dry cleaning facility, that are part of the overall Riverfront Superfund Site. Traditional soil and ground-water sampling at these two sites later confirmed the results from the tree-core sampling. Results obtained from the tree-core sampling were used to design and focus subsequent soil and ground-water investigations, resulting in substantial savings in time and site assessment costs. The Front Street site is a small (less than 1-acre) site located on the Missouri River alluvium in downtown New Haven, Missouri, about 500 feet from the south bank of the Missouri River. Tree-core sampling detected the presence of subsurface PCE contamination at the Front Street site and beneath residential property downgradient from the site. Core samples from trees at the site contained PCE concentrations as large as 3,850 mg-h/kg (micrograms in headspace per kilogram of wet core) and TCE concentrations as large as 249 mg-h/kg. Soils at the Front Street site contained PCE concentrations as large as 6,200,000 mg/kg (micrograms per kilogram) and ground-water samples contained PCE concentrations as large as 11,000 mg/L (micrograms per liter). The former dry cleaning facility is located at the base of the upland that forms the south bank of the Missouri River alluvial valley. Tree-core sampling did not indicate the presence of PCE or TCE contamination at the former dry cleaning facility, a finding that was later confirmed by the analyses of soil samples collected from the site. The lateral extent of PCE contamination in trees was in close agreement with the extent of subsurface PCE contamination determined using traditional soil and ground-water sampling methods. Trees growing in soils containing PCE concentrations of 60 to 5,700 mg/kg or larger or overlying ground water containing PCE concentrations from 5 to 11,000 mg/L generally contained detectable concentrations of PCE. The depth to contaminated ground water was about 20 to 25 feet below the land surface. Significant quantitative relations [probability (p) values of less than 0.05 and correlation coefficient (r2) values of 0.88 to 0.90] were found between PCE concentrations in trees and subsurface soils between 4 and 16 feet deep. The relation between PCE concentrations in trees and underlying ground water was less apparent (r2 value of 0.17) and the poor relation is thought to be the result of equilibrium with PCE concentrations in soil and vapor in the unsaturated zone. Based on PCE concentrations detected in trees at the Front Street site and trees growing along contaminated tributaries in other operable units, and from field hydroponic experiments using hybrid poplar cuttings, analysis of tree-core samples appears to be able to detect subsurface PCE contamination in soils at levels of several hundred micrograms per liter or less and PCE concentrations in the range of 8 to 30 mg/L in ground water in direct contact with the roots. Loss of PCE from tree trunks by diffusion resulted in an exponential decrease in PCE concentrations with increasing height above the land surface in most trees. The rate of loss also appeared to be a function of the size and growth characteristics of the tree as some trees exhibited a linear loss with increasing height. Diffusional loss of PCE in small (0.5-inch diameter) trees was observed to occur at a rate more than 10 times larger than in trees 6.5 inches in diameter. Concentrations of PCE also exhibited directional variability around the tree trunks and concentration differe

Schumacher, John G.; Struckhoff, Garrett C.; Burken, Joel G.

2004-01-01

405

78 FR 15721 - Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Request; NESHAP for Perchloroethylene Dry Cleaning Facilities (Renewal) AGENCY: Environmental...Title: NESHAP for Perchloroethylene Dry Cleaning Facilities (Renewal). ICR Numbers...or operators of perchloroethylene dry cleaning facilities. Estimated Number of...

2013-03-12

406

Isolation and Characterization of “Dehalococcoides” sp. Strain MB, Which Dechlorinates Tetrachloroethene to trans-1,2-Dichloroethene? †  

PubMed Central

In an attempt to understand the microorganisms involved in the generation of trans-1,2-dichloroethene (trans-DCE), pure-culture “Dehalococcoides” sp. strain MB was isolated from environmental sediments. In contrast to currently known tetrachloroethene (PCE)- or trichloroethene (TCE)-dechlorinating pure cultures, which generate cis-DCE as the predominant product, Dehalococcoides sp. strain MB reductively dechlorinates PCE to trans-DCE and cis-DCE at a ratio of 7.3 (±0.4):1. It utilizes H2 as the sole electron donor and PCE or TCE as the electron acceptor during anaerobic respiration. Strain MB is a disc-shaped, nonmotile bacterium. Under an atomic force microscope, the cells appear singly or in pairs and are 1.0 ?m in diameter and ?150 nm in depth. The purity was confirmed by culture-based approaches and 16S rRNA gene-based analysis and was corroborated further by putative reductive dehalogenase (RDase) gene-based, quantitative real-time PCR. Although strain MB shares 100% 16S rRNA gene sequence identity with Dehalococcoides ethenogenes strain 195, these two strains possess different dechlorinating pathways. Microarray analysis revealed that 10 putative RDase genes present in strain 195 were also detected in strain MB. Successful cultivation of strain MB indicates that the biotic process could contribute significantly to the generation of trans-DCE in chloroethene-contaminated sites. It also enhances our understanding of the evolution of this unusual microbial group, Dehalococcoides species. PMID:19633106

Cheng, Dan; He, Jianzhong

2009-01-01

407

Probabilistic approach to estimating indoor air concentrations of chlorinated volatile organic compounds from contaminated groundwater: a case study in San Antonio, Texas.  

PubMed

This paper describes a probabilistic model, based on the Johnson-Ettinger algorithm, developed to characterize the current and historic exposure to tricholorethylene (TCE) and tetrachlorethylene (PCE) in indoor air from plumes of groundwater contamination emanating from the former Kelly Air Force Base in San Antonio, Texas. We estimate indoor air concentration, house by house, in 30?101 homes and compare the estimated concentrations with measured values in a small subset of homes. We also compare two versions of the Johnson-Ettinger model: one used by the Environmental Protection Agency (EPA) and another based on an alternative parametrization. The modeled mean predicted PCE concentration historically exceeded PCE screening levels (0.41 ug/m(3)) in 5.5% of houses, and the 95th percentile of the predicted concentration exceeded screening levels in 85.3% of houses. For TCE, the mean concentration exceeded the screening level (0.25 ug/m(3)) in 49% of homes, and the 95th percentile of the predicted concentration exceeded the screening level in 99% of homes. The EPA model predicts slightly lower indoor concentrations than the alternative parametrization. Comparison with measured samples suggests both models, with the inputs selected, underestimate indoor concentrations and that the 95th percentiles of the predicted concentrations are closer to measured concentrations than predicted mean values. PMID:21162557

Johnston, Jill E; Gibson, Jacqueline MacDonald

2011-02-01

408

Process for removing halogenated aliphatic and aromatic compounds from petroleum products. [Polychlorinated biphenyls; methylene chloride; perchloroethylene; trichlorofluoroethane; trichloroethylene; chlorobenzene  

DOEpatents

A process for removing halogenated aliphatic and aromatic compounds, e.g., polychlorinated biphenyls, from petroleum products by solvent extraction. The halogenated aliphatic and aromatic compounds are extracted from a petroleum product into a polar solvent by contracting the petroleum product with the polar solvent. The polar solvent is characterized by a high solubility for the extracted halogenated aliphatic and aromatic compounds, a low solubility for the petroleum product and considerable solvent power for polyhydroxy compound. The preferred polar solvent is dimethylformamide. A miscible polyhydroxy compound, such as, water, is added to the polar extraction solvent to increase the polarity of the polar extraction solvent. The halogenated aliphatic and aromatic compounds are extracted from the highly-polarized mixture of polyhydroxy compound and polar extraction solvent into a low polar or nonpolar solvent by contacting the polyhydroxy compound-polar solvent mixture with the low polar or nonpolar solvent. The halogenated aliphatic and aromatic compounds in the low polar or nonpolar solvent by physical means, e.g., vacuum evaporation. The polar and nonpolar solvents are recovered for recycling. The process can easily be designed for continuous operation. Advantages of the process include that the polar solvent and a major portion of the nonpolar solvent can be recycled, the petroleum products are reclaimable and the cost for disposing of waste containing polychlorinated biphenyls is significantly reduced. 2 tables.

Googin, J.M.; Napier, J.M.; Travaglini, M.A.

1982-03-31

409

Electrochemical SERS detection of chlorinated hydrocarbons in aqueous solutions  

SciTech Connect

An [ital in] [ital situ] method for the determination of trichloroethylene (TCE), perchlorethylene (PCE), chloroform (CHCl[sub 3]) and carbon tetrachloride (CCl[sub 4]) in aqueous solution is described. The method is based on ESERS-a combination of electrochemical methods and surface-enhanced Raman scattering (SERS). Electrochemistry prepares the surface of a copper electrode for SERS and concentrates the analyte on the surface. The formation of common reaction products for chloroalkanes and for chloroalkenes prevents unequivocal differentiation within a specific class of chlorinated hydrocarbons. However, spectroscopic selectivity between the chloroalkane and chloroalkene classes is excellent, while differences in electrochemical response provide a secondary means for differentiating analyte class. Sensitivity was found to be: [lt]1 ppm for TCE; 15 ppm for PCE; 15 ppm for CHCl[sub 3]; and 10 ppm for CCl[sub 4]. Application of the method to groundwater contaminated with TCE has been demonstrated. In combination with a fiber-optic waveguide, the ESERS technique offers potential for remote detection of chlorinated hydrocarbons in groundwater and remediation process streams.

Storey, J.M.E.; Shelton, R.D.; Barber, T.E.; Wachter, E.A. (Health Sciences Research Division, Oak Ridge, National Laboratory, Oak Ridge, Tennessee 37831-6113 (United States))

1994-10-01

410

Reductive capacity of natural reductants.  

PubMed

Reductive capacities of soil minerals and soil for Cr(VI) and chlorinated ethylenes were measured and characterized to provide basic knowledge for in-situ and ex-situ treatment using these natural reductants. The reductive capacities of iron-bearing sulfide (pyrite), hydroxide (green rust; GR(SO4)), and oxide (magnetite) minerals for Cr(VI) and tetrachloroethylene (PCE) were 1-3 orders of magnitude greater than those of iron-bearing phyllosilicates (biotite, vermiculite, and montmorillonite). The reductive capacities of surface soil collected from the plains of central Texas were similar and slightly greater than those of iron-bearing phyllosilicates. The reductive capacity of iron-bearing soil minerals for Cr(VI) was roughly 3-16 times greater than that for PCE, implying that Cr(VI) is more susceptible to being reduced by soil minerals than is PCE. GR(SO4) has the greatest reductive capacity for both Cr(VI) and PCE followed by magnetite, pyrite, biotite, montmorillonite, and vermiculite. This order was the same for both target compounds, which indicates that the relative reductive capacities of soil minerals are consistent. The reductive capacities of pyrite and GR(SO4) for chlorinated ethylenes decreased in the order: trichloroethylene (TCE) > PCE > cis-dichloroethylene (c-DCE) > vinyl chloride (VC). Fe(II) content in soil minerals was directly proportional to the reductive capacity of soil minerals for Cr(VI) and PCE, suggesting that Fe(II) content is an important factor that significantly affects reductive transformations of target contaminants in natural systems. PMID:12630469

Lee, Woojin; Batchelor, Bill

2003-02-01

411

Acoustically enhanced nonaqueous phase liquid remediation in porous media  

NASA Astrophysics Data System (ADS)

Groundwater contamination, caused by the presence of dense nonaqueous phase liquids (DNAPLs), remains a remediation challenge due to their low aqueous solubilities and residual phase immobility. To combat this challenge, the application of acoustic waves for remediation of water saturated porous media contaminated by DNAPL ganglia is proposed and investigated in this study. Experiments are performed to first determine the effects of acoustic waves on the transport of a conservative tracer in a water-saturated column packed with glass beads. From resulting experimental tracer data, the addition of acoustic waves, in the frequency range between 60 to 245 Hz, to a steady background fluid flow (base case) is found to enhance solute transport compared to the base case. Furthermore, the effective velocity of the solute is approximately inversely proportional to the frequency of the acoustic wave. Next, the effects of acoustic waves on the dissolution of trichloroethylene (TCE) DNAPL ganglia in a water saturated column, packed with glass beads are investigated. Acoustic waves with pressure amplitudes ranging from 0 to 1625 Pa and frequencies ranging from 0 to 285 Hz are employed to the interstitial fluid at the inlet of the packed column. Effluent dissolved TCE concentrations are observed to increase in the presence of acoustic pressure waves compared to the case where TCE dissolution without acoustic waves is monitored. The observed effluent dissolved TCE concentration increase is attributed to increased mass flux at the TCE-water interface, caused by acoustic waves. As an extension to the single component ganglia dissolution experiments, the impact of acoustic pressure waves on multicomponent DNAPL ganglia dissolution is also investigated. The multicomponent ganglia was composed of TCE and 1,1,2-trichloroethane (1,1,2-TCA) or TCE, 1,1,2-TCA, and tetrachloroethylene (PCE). Laboratory data from ganglia dissolution experiments with two and three component NAPL mixtures show that the greatest dissolution enhancement in the presence of acoustic waves is associated with the NAPL component having the smallest equilibrium aqueous solubility. Finally, square shaped acoustic waves are shown to lead to greater NAPL dissolution enhancement compared to sinusoidal and triangular acoustic waves. Finally, a pore network consisting of a monolayer of glass beads is used to investigate the effects of acoustic waves on the dissolution and mobilization of perchlorethylene (PCE) ganglia. (Abstract shortened by UMI.)

Vogler, Eric Todd

412

Characterization Report to Support the Phytoremediation Efforts for Southern Sector, Savannah River Site, Aiken, South Carolina  

SciTech Connect

In February, 1999, we conducted a small-scale characterization effort to support future remediation decisions for the Southern Sector of the upper Three Runs watershed. The study concentrated on groundwater adjacent to the seepline at Tim's Branch above and below Steed's Pond. the primary compounds of interest were the volatile organic contaminants (VOCs), trichlorethylene (TCE) and tetrachloroethylene (PCE). Due to the site topography and hydrogeology, samples collected north of Steed's Pond were from the M-Area (water table) aquifer; while those locations south of Steed's Pond provided samples from the Lost Lake aquifer. Results of the study suggest that the leading edge of the A/M Area plume in the Lost Lake aquifer may be approaching the seepline at Tim's Branch below Steed's Pond, south of Road 2. Neither TCE nor PCE were detected int he samples targeting the seepline of the water table aquifer. The concentrations found for both TCE and PCE associated with the Lost Lake aquifer outcrop region were slightly above the detection limit of the analytical instrument used. The findings of this study are consistent with the conceptual model for the organic contaminant plume in the A/M Area of the Savannah River Site (SRS) -- the plume in the Southern Sector is known to be depth discrete and primarily in the Lost lake Aquifer. The sites with detected VOCs are in the most upstream accessible reaches of Tim's Branch where water from the Lost Lake Aquifer crops out. Additional characterization efforts should be directed near this region to confirm the results and to support future planning for the dilute-distal portions of the A/M Area plume. These data, combined with existing groundwater plume data and future characterization results will provide key information to estimate potential contaminant flux to the seepline and to assess the effectiveness of potential clean-up activities such as phytoremediation.

Jerome, K.M.

1999-06-08

413

The effect of BTEX compounds on aerobic cometabolism of vinyl chloride by ethylene grown enrichment cultures  

SciTech Connect

There is mounting field evidence that groundwater contaminated with trichloroethylene (TCE) and tetrachloroethylene (PCE) can be efficiently treated in situ by stimulating anaerobic reductive dechlorination, producing primarily ethylene and/or ethane. However, persistence of vinyl chloride (VC), even at low levels, may result in the need for subsequent aerobic treatment. A recent study by Freedman and Herz (1995) indicated that ethylene and ethane can serve as the primary substrates for aerobic cometabolism of VC, thereby avoiding the need to add an exogenous primary substrate. At many sites where PCE and TCE are found, other organic contaminants are also prevalent in mixtures. Chief among these are BTEX compounds (benzene (BEN), toluene (TOL), ethylbenzene (EBZ) and o-xylene (XYL)). Except for TOL, a limited amount of BTEX biodegradation is typically expected under anaerobic conditions, so most of the BTEX that occurs with PCE and TCE is likely to reach the aerobic zone along with VC, ethylene, and ethane. The objective of this study was to determine the effect of BTEX compounds on aerobic biodegradation of ethylene and VC. In an ethylene-grown enrichment culture, addition of BEN, EBZ, and TOL (6-59 mg/L) inhibited the initial rate of ethylene and VC biodegradation by 75% and 67%, respectively. The lower concentration of XYL added (0.80 mg/L) had a minor effect. As the rate of BEN, EBZ, and TOL biodegradation improved with time, no further inhibition of VC and ethylene consumption was observed. A population of BTEX degrading organisms developed in the ethylene-grown culture, but this did not result in a faster rate of VC or ethylene use. Separately developed BEN- and TOL-grown enrichment cultures confirmed this. Neither aromatic enrichment culture was able to biodegrade VC or ethylene, but both were able to consume all of the other aromatic compounds.

Freedman, D.L.; Williamson, A.E.

1996-12-31

414

Refinement of the density-modified displacement method for efficient treatment of tetrachloroethene source zones  

NASA Astrophysics Data System (ADS)

A novel method to remediate dense nonaqueous phase liquid (DNAPL) source zones that incorporates in situ density conversion of DNAPL via alcohol partitioning followed by displacement with a low interfacial tension (IFT) surfactant flood has been developed. Previous studies demonstrated the ability of the density-modified displacement (DMD) method to recover chlorobenzene (CB) and trichloroethene (TCE) from heterogeneous porous media without downward migration of the dissolved plume or free product. However, the extent of alcohol (n-butanol) partitioning required for in situ density conversion of high-density NAPLs, such as tetrachloroethene (PCE), could limit the utility of the DMD method. Hence, the objective of this study was to compare the efficacy of two n-butanol delivery approaches: an aqueous solution of 6% (wt) n-butanol and a surfactant-stabilized macroemulsion containing 15% (vol) n-butanol in water, to achieve density reduction of PCE-NAPL in two-dimensional (2-D) aquifer cells. Results of liquid-liquid equilibrium studies indicated that density conversion of PCE relative to water occurred at an n-butanol mole fraction of 0.56, equivalent to approximately 5 ml n-butanol per 1 ml of PCE when in equilibrium with an aqueous solution. In 2-D aquifer cell studies, density conversion of PCE was realized using both n-butanol preflood solutions, with effluent NAPL samples exhibiting density reductions ranging from 0.51 to 0.70 g/ml. Although the overall PCE mass recoveries were similar (91% and 93%) regardless of the n-butanol delivery method, the surfactant-stabilized macroemulsion preflood removed approximately 50% of the PCE mass. In addition, only 1.2 pore volumes of the macroemulsion solution were required to achieve in situ density conversion of PCE, compared to 6.4 pore volumes of the 6% (wt) n-butanol solution. These findings demonstrate that use of the DMD method with a surfactant-stabilized macroemulsion containing n-butanol holds promise as an effective source zone remediation technology, allowing for efficient recovery of PCE-DNAPL while mitigating downward migration of the dissolved plume and free product.

Ramsburg, C. Andrew; Pennell, Kurt D.; Kibbey, Tohren C. G.; Hayes, Kim F.

2004-10-01

415

Permanganate Treatment of DNAPLs in Reactive Barriers and Source Zone Flooding Schemes - Final Report  

SciTech Connect

This study provides a detailed process-level understanding of the oxidative destruction of the organic contaminant emphasizing on reaction pathways and kinetics. A remarkable rise in the MnO{sup {minus}} consumption rate with TCA and PCE mixtures proves that the phase transfer catalysts have the ability to increase oxidation rate of DNAPLs either in pure phase or mixtures and that there is significant potential for testing the catalyzed scheme under field conditions. Secondly, as an attempt to enhance the oxidation of DNAPL, we are trying to exploit cosolvency effects, utilizing various alcohol-water mixtures to increase DNAPL solubilization. Preliminary results of cosolvency experiments indicate the enhancement in the transfer of nonaqueous phase TCE to TBA-water solution and the rate of TCE degradation in aqueous phase.

Schwartz, F.W.

2000-10-01

416

Superfund Record of Decision (EPA Region 5): FMC Corporation, Fridley, Minnesota (second remedial action), September 1987. Final report  

SciTech Connect

The FMC site, in the City of Fridley, Minnesota is approximately 1,000 feet east of the Mississippi River, just north of the City of Minneapolis, and upstream of the City of Minneapolis drinking-water intake. Investigation revealed historical waste-disposal practices and found contamination of the ground water and Mississippi River. Currently underlying ground water and alluvial aquifers with discharge to the Mississippi River are contaminated with trichloroethene (TCE), Porchloroethylene (PCE), benzene, toluene, xylene, and other volatile organic compounds (VOCs). TCE has been estimated to account for 98% of the contaminant loading. The selected remedial action for the site includes: ground-water pump and treatment with discharge to a sewer system; ground-water monitoring; and implementation of institutional controls with land-use restrictions to mitigate against near-term usage of contaminated ground water between the site and the Mississippi River.

Not Available

1987-09-30

417

Test plan for in situ bioremediation demonstration of the Savannah River Integrated Demonstration Project DOE/OTD TTP No.: SR 0566-01. Revision 3  

SciTech Connect

This project is designed to demonstrate in situ bioremediation of groundwater and sediment contaminated with chlorinated solvents. Indigenous microorganisms will be simulated to degrade trichloroethylene (TCE), tetrachloroethylene (PCE) and their daughter products in situ by addition of nutrients to the contaminated zone. in situ biodegradation is a highly attractive technology for remediation because contaminants are destroyed, not simply moved to another location or immobilized, thus decreasing costs, risks, and time, while increasing efficiency and public and regulatory acceptability. Bioremediation has been found to be among the least costly technologies in applications where it will work.

Hazen, T.C.

1991-09-18