Trichloroethylene Research Papers - Academia.edu (original) (raw)

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- Water, Groundwater Contamination, Multidisciplinary, Tropical trees

Objective: To analyze a cluster of 30 industrial coworkers with Parkinson's disease and parkinsonism subjected to long-term (8 -33 years) chronic exposure to trichloroethylene. Methods: Neurological evaluations were conducted on the 30 coworkers, including a general physical and neurological examination and the Unified Parkinson's Disease Rating Scale. In addition, fine motor speed was quantified and an occupational history survey was administered. Next, animal studies were conducted to determine whether trichloroethylene exposure is neurotoxic to the nigrostriatal dopamine system that degenerates in Parkinson's disease. The experiments specifically analyzed complex 1 mitochondrial neurotoxicity because this is a mechanism of action of other known environmental dopaminergic neurotoxins. Results: The three workers with workstations adjacent to the trichloroethylene source and subjected to chronic inhalation and dermal exposure from handling trichloroethylene-soaked metal parts had Parkinson's disease. Coworkers more distant from the trichloroethylene source, receiving chronic respiratory exposure, displayed many features of parkinsonism, including significant motor slowing. Neurotoxic actions of trichloroethylene were demonstrated in accompanying animal studies showing that oral administration of trichloroethylene for 6 weeks instigated selective complex 1 mitochondrial impairment in the midbrain with concomitant striatonigral fiber degeneration and loss of dopamine neurons. Interpretation: Trichloroethylene, used extensively in industry and the military and a common environmental contaminant, joins other mitochondrial neurotoxins, MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and some pesticides, as a risk factor for parkinsonism.

- by Don Gash
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- Animal Studies, Mitochondria, Energy Metabolism, Dopamine

Microbiological degradation of perchloroethylene (PCE) under anaerobic conditions follows a series of chain reactions, in which, sequentially, trichloroethylene (TCE), cis-dichloroethylene (c-DCE), vinylchloride (VC) and ethene are generated. First-order degradation rate constants, partitioning coecients and mass exchange rates for PCE, TCE, c-DCE and VC were compiled from the literature. The parameters were used in a case study of pump-and-treat remediation of a PCE-contaminated site near Tilburg, The Netherlands. Transport, non-equilibrium sorption and biodegradation chain processes at the site were simulated using the CHAIN_2D code without further calibration. The modelled PCE compared reasonably well with observed PCE concentrations in the pumped water. We also performed a scenario analysis by applying several increased reductive dechlorination rates, re¯ecting dierent degradation conditions (e.g. addition of yeast extract and citrate). The scenario analysis predicted considerably higher concentrations of the degradation products as a result of enhanced reductive dechlorination of PCE. The predicted levels of the very toxic compound VC were now an order of magnitude above the maximum permissible concentration levels.

- by Don Gash
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- Electrochemistry, Neurochemistry, Oxidative Stress, Mitochondria

The reaction of trichloroethylene (C2HCI3) with water vapor or molecular hydrogen has been studied in a low-pressure [ca. 5 Torr (0.67 kPa)] microwave plasma tubular flow reactor. The experimental apparatus included feed introduction systems, a microwave plasma reactor, and full product analysis by flame ionization and thermal-conductivity gas chromatography, mass spectrometry, and specific ion or pH detection for hydrogen chloride [HCI]. Conversions of CeHC13 in the range 50 to almost 100% are achieved. Product analyses indicate conversion to HCI, some light hydrocarbons, nonparent chlorocarbons, and soot C(s). For the H20 case, carbon monoxide and trace carbon dioxide were produced in place of some light hydrocarbons and Cc~). At least 85 mole % of chlorine (CI) from the converted parent C2HCl s forms thermodynamically stable HCI at parent conversions of 80% or more. The remaining chlorine was present as nonparent chlorocarbons. Preliminary kinetic analyses were performed. The global reaction in the plasma was found to follow one-half-order kinetic dependence on each of C2HCl 3 and H20 or H 2. Elementary plasma reaction mechanisms are presented to account for CeHCI 3 conversion and the observed product distribution.

- by Robert Barat
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- Chemical Engineering, Thermodynamics, Carbon Dioxide, Kinetics

Basal spacing of smectitic clays contacted with chlorinated solvents was measured. Contact with pure solvents did not change basal spacing of water-saturated clays. But, DNAPL wastes decreased the basal spacing of water-saturated sodium... more

- by Mark Goltz
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- Multidisciplinary, Trichloroethylene, Tetrachloroethylene, Silicates

Objectives: To evaluate the antioxidative and therapeutic effects of spirulina on the trichloroethylene induced cutaneous irritation balb/c mice. Background: During recent years, an attention has been focused on the antioxidant potential of Spirulina species. Methods: Balb/c mice were randomized into the four groups. At the end of the each application, the rats were sacrifi ced and dorsal skin was taken. Histopathologic and immunohistochemical evaluations were conducted, oxidative stress was assessed by the measurement of malondialdehyde (MDA) levels, superoxide dismutase (SOD) activities and nitric oxide (NO) production. Results: There was a statistically signifi cant decreased disruption in epidermal integrity, oedema in intercellular dermis, disorganization in collagen fi bres and immunoreactivity in the pre acute dermatitis/ antioxidant and the post acute dermatitis/ treatment groups when compared to the acute dermatitis group (p<0.05).

- by Neslihan Gurbuz
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- Oxidative Stress, Antioxidants, Mice, Skin Diseases

Key attributes of the source zone and the expanding dissolved plume at a trichloroethene (TCE) site in Australia were evaluated using trends in groundwater monitoring data along with data from on-line volatile organic compound (VOC) samplers and passive flux meters (PFMs) deployed in selected wells. These data indicate that: (1) residual TCE source mass in the saturated zone, estimated using two innovative techniques, is small (∼ 10 kg), which is also reflected in small source mass discharge (∼ 3 g/day); (2) the plume is disconnecting, based on TCE concentration contours and TCE fluxes in wells along a longitudinal transect; (3) there is minimal biodegradation, based on TCE mass discharge of ∼ 6 g/day at a plume control plane ∼ 175 m from source, which is also consistent with aerobic geochemical conditions observed in the plume; and (4) residual TCE in the vadose zone provides episodic inputs of TCE mass to the plume during infiltration/recharge events. TCE flux data also suggest that the small residual TCE source mass is present in the low-permeability zones, thus making source treatment difficult. Our analysis, based on a synthesis of the archived data and new data, suggests that source treatment is unwarranted, and that containment of the large TCE plume (∼ 1.2 km long, ∼ 0.3 km wide; 17 m deep; ∼ 2000-2500 kg TCE mass) or institutional controls, along with a long-term flux monitoring program, might be necessary. The flux-based site management approach outlined in this paper provides a novel way of looking beyond the complexities of groundwater contamination in heterogeneous domains, to make intelligent and informed site decisions based on strategic measurement of the appropriate metrics.

- by Ravi Naidu
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- Australia, Groundwater Contamination, Multidisciplinary, Contaminant hydrology

Effective phytoremediation of heavy metal-or chlorinated solventcontaminated sites by fast-growing trees is strongly influenced by the choice of tree species and genotypes (e.g., clones, progenies). As evidenced in ongoing phytoremediation systems, genetic testing is necessary to match species and genotypes within species to site, microclimate, and contaminant conditions. Tree growth and arsenic uptake varied considerably between and within three species. At a toluene-contaminated site, two species were initially similar in vigor and emitted contaminants, but one species was eventually superior and had contaminants in leaf and branch tissues. At a trichloroethylene (TCE)-contaminated site, locally adapted clones greatly surpassed a clone widely planted for phytoremediation in more temperate regions. While 16 clones survived and grew rapidly in perchloroethylene (PCE)-contaminated soil, the five best clones were as much as twice the average size and supported more methanotrophs. At a hydrocarboncontaminated site, even five local clones varied considerably. In a landfill cap, 16 progenies and 32 local clones had comparable survival and tree size that exceeded two non-adapted clones. These and similar results elsewhere illustrate the considerable importance of field testing species and genotypes for appropriate prerequisites in order to reach the phytoremediation potential of fast-growing trees.

- by Angela Lindner
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- Arsenic, Genetic Testing, Tree growth, Trichloroethylene
- by Shams Tabrez
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- Multidisciplinary, Biological markers, Trichloroethylene, Mutagens

A multidimensional integral finite difference numerical simulator is developed for modeling the steam displacement of nonaqueous phase liquid (NAPL) contaminants in shallow subsurface systems. This code, named STM¾OC, considers three flowing phases, gas, aqueous, and NAPL; and three mass components, air, water, and an organic chemical. Interphase mass transfer of the components between any of the phases is calculated by assuming local chemical equilibrium between the phases, and adsorption of the chemical to the soil is included. Heat transfer occurs due to conduction and multiphase convection and includes latent heat effects. A general equation of state is implemented in the code for calculating the thermophysical properties of the NAPL/chemical. This equation of state is primarily based on corresponding states methods of property estimation using a chemical's critical constants. The necessary constants are readily available for several hundred hazardous organic liquid chemicals. In part 2 (Falta et al., this issue), the code is used to simulate two one-dimensional laboratory steam injection experiments and to examine the effect of NAPL properties on the steam displacement process. systems, they were developed for use in isothermal problems and do not consider heat transfer. This limitation precludes the use of these simulators for modeling steam injection processes.

- by Iraj Javandel and +1
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- Environmental Engineering, Civil Engineering, Mass Transfer, Water resources

A retrospective cohort study was carried out in a cardboard factory in Germany to investigate the association between exposure to trichloroethene (TRI) and renal cell cancer. The study group consisted of 169 men who had been exposed to TRI for at least 1 year between 1956 and 1975. The average observation period was 34 years. By the closing day of the study (December 31, 1992) 50 members of the cohort had died, 16 from malignant neoplasms. In 2 out of these 16 cases, kidney cancer was the cause of death, which leads to a standard mortality ratio of 3.28 compared with the local population. Five workers had been diagnosed with kidney cancer: four with renal cell cancers and one with a urothelial cancer of the renal pelvis. The standardized incidence ratio compared with the data of the Danish cancer registry was 7.97 (95% CI: 2.59 -18.59). After the end of the observation period, two additional kidney tumors (one renal cell and one urothelial cancer) were diagnosed in the study group. The control group consisted of 190 unexposed workers in the same plant.

- by Kurt Ulm
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- Adolescent, Renal cell Carcinoma, Statistical Significance, Cohort Study

Hybrid plasma catalyst technology has great potential for indoor air purification. However, humidity is a critical parameter in plasma catalytic processes. In this work, several catalysts were tested downstream of a DC corona discharge and the effect of humidity was investigated on both ozone and toluene removal. Next, sorption measurements onto the catalysts were performed for toluene, trichloroethylene and acetone, using an equilibrium partitioning in closed system procedure to explain the obtained results in a quantitative manner.

- by jim van durme
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- Environmental Engineering, Chemical Engineering, Technology, Catalysis
- by Louis Bloemen
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- Archives, Industry, Incidence, Retrospective Studies

Organically modified silica that rapidly and reversibly swells to >3 times their dry volume have been recently described. Here, these organosilica materials were demonstrated to have the ability absorb trichloroethylene (TCE), perchloroethylene (PCE), methyl t-butyl ether (MTBE), toluene, naphthalene, acetone, 1,4-dioxane, and 1-butanol from water. Direct experimental comparisons indicated that swellable organically modified silica (SOMS) has in many instances greater capacity than activated carbon and molecular sieves and possesses the ability to capture a wide range of dissolved polar and non-polar organic contaminants. The absorption of organic species to SOMS is enhanced by matrix expansion leading to non-selective capture of organics beyond what could only be attributed to physisorption. This process appears to be facilitated by initial adsorption events unlatching the collapsed matrix leading to the opening of nanometer-scale pores within the tensioned SOMS material, thus providing volume for absorption. Partition coefficients for the absorption of organic species from water by SOMS ranged from 2.8 × 10 5 to 1.0 × 10 2 , and vary depending on polarity of the contaminant, concentration, and the total mass of contaminant absorbed. Maximum capacity exceed three times the dry weight of the absorbent under conditions of high contaminant concentration. SOMS was repeatedly regenerated with mild thermal treatment (60-110 • C) in air to evaporate absorbates from the matrix which could be subsequently collected. Only a slight decrease in effectiveness is observed after regeneration. Absorption is equally effective from salt water. Minimal loss of capacity and affinity is lost when extracting environmentally relevant concentrations of TCE from a topsoil/water mixture, presumably due to a molecular sieving effect.

- by Paul Edmiston
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- Chemical Engineering, Analytical Chemistry, Activated Carbon, Silica
- by R. Baan and +1
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- Carcinogens, Lancet Oncology, Occupational Exposure, Neoplasms

Henry's law constants for 12 chlorinated volatile organic compounds (CVOCs) were measured as a function of temperature ranging from 8 to 93°C, using the modified equilibrium partitioning in closed system (EPICS) method. The chlorinated compounds include tetrachloroethylene, trichloroethylene, cis-1,2dichloroethylene, vinyl chloride, 1,1,1-trichloroethane, 1,1-dichloroethane, 1,2-dichloroethane, chloroethane, carbon tetrachloride, chloroform, dichloromethane, and chloromethane. The variation in Henry's constants for these compounds as a function of temperature ranged from around 3-fold (chloroethane) to 30-fold (1,2-dichloroethane). Aqueous solubilities of the pure compounds were measured over the temperature range of 8-75°C. The temperature dependence of Henry's constant was predicted using the ratio of pure vapor pressure to aqueous solubility, both of which are functions of temperature. The calculated Henry's constants are in a reasonable agreement with the measured results. With the improved data on Henry's law constants at high temperatures measured in this study, it will be possible to more accurately model subsurface remediation processes that operate near the boiling point of water.

- by Ronald Falta and +1
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- Thermodynamics, Multidisciplinary, Volatile Organic Compounds, Vapor Pressure

Dichloroacetic acid (DCA) is a compound found in chlorinated drinking water. In addition, the compound is a metabolite of several halogenated solvents, including trichloroethylene (TCE) and perchloroethylene (PCE). Exposure to DCA is of concern because high doses of the compound have been shown to cause cancer in laboratory animals. Dosages of TCE administered to animals in cancer studies are designed to elicit maximal DCA formation in vivo, whereas levels of DCA to which individuals are exposed in drinking water are very low. Analysis of DCA in biological samples has been quite challenging. Derivatizing reagents commonly used to convert DCA into a more volatile form for analysis by gas chromatography (GC) have been found to convert trichloroacetic acid (TCA), a major metabolite of TCE and PCE, into DCA. High-performance liquid chromatography (HPLC) analysis does not require derivatization of DCA and can thus avoid this problem. However, the most popular stationary phases in HPLC columns do not retain small, polar compounds such as DCA well. The liquid chromatography/tandem mass spectrometry (LC/MS/MS) method described in this paper uses hydrophilic interaction liquid chromatography (HILIC), a type of chromatography that is able to retain these small, polar compounds. Method validation was performed using the United States Food and Drug Administration (USFDA) and International Conference on Harmonziation (ICH) Guidance for Industry: Bioanalytical Method Validation as a guide. Levels of DCA found in rats dosed with 2 g/kg TCE were 17.2 ng/mL (liver), 262.4 ng/mL (kidney), 175.1 ng/mL (lung), and 39.5 ng/mL (blood). Copyright © 2005 John Wiley & Sons, Ltd.

- by Lawrence Lash
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- Kinetics, Drug metabolism, Enzymes, Kidney

Isotope Ratio Mass Spectrometry (IRMS) is a specialized technique used to provide information about the geographic, chemical, and biological origins of substances. The ability to determine the source of an organic substance stems from the relative isotopic abundances of the elements which comprise the material. Because the isotope ratios of elements such as carbon, hydrogen, oxygen, sulfur, and nitrogen can become locally enriched or depleted through a variety of kinetic and thermodynamic factors, measurement of the isotope ratios can be used to differentiate between samples which otherwise share identical chemical compositions. Several sample introduction methods are now available for commercial isotope ratio mass spectrometers. Combustion is most commonly used for bulk isotopic analysis, whereas gas and liquid chromatography are predominately used for the real-time isotopic analysis of specific compounds within a mixture. Here, highlights of advances in instrumentation and applications within the last three years are provided to illustrate the impact of this rapidly growing area of research. Some prominent new applications include authenticating organic food produce, ascertaining whether or not African elephants are guilty of night-time raids on farmers' crops, and linking forensic drug and soil samples from a crime scene to a suspected point of origin. For the sake of brevity, we focus this Minireview on the isotope ratio measurements of lighter-elements common to organic sources; we do not cover the equally important field of inorganic isotope ratio mass spectrometry. His research interests include ion trap development, forensic applications of isotope ratio mass spectrometry and the construction of miniature, portable mass spectrometers. He also teaches workshops on Forensic Applications of Mass Spectrometry.

- by Bruno Varela
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- Engineering, Environmental Science, Stable Isotope Analysis, Mass Spectrometry

The authors outline a theory of conditionals of the form If A then C and If A then possibly C. The 2 sorts of conditional have separate core meanings that refer to sets of possibilities. Knowledge, pragmatics, and semantics can modulate these meanings. Modulation can add information about temporal and other relations between antecedent and consequent. It can also prevent the construction of possibilities to yield 10 distinct sets of possibilities to which conditionals can refer. The mental representation of a conditional normally makes explicit only the possibilities in which its antecedent is true, yielding other possibilities implicitly. Reasoners tend to focus on the explicit possibilities. The theory predicts the major phenomena of understanding and reasoning with conditionals.

- by Ruth M J Byrne
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- Psychology, Cognitive Science, Logic, Semantics

Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h(-1) were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h(-1) were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient...

- by Ljiljana Rajic
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- Water, Catalysis, Water Purification, Multidisciplinary

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

- by John Cherry
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- Groundwater, Environmental Monitoring, Ground Water, Trichloroethylene

A variety of column experiments have been completed for the purpose of selecting and evaluating suitable surfactants for remediation of nonaqueous phase liquids (NAPLs). The various NAPLs tested in the laboratory experiments were tetrachloroethylene (PCE), trichloroethylene (TCE), jet fuel (JP4) and a dense nonaqueous phase liquid from a site at Hill Air Force Base, UT. Both Ottawa sand and Hill field soil were used in these experiments. Surfactant candidates were first screened using phase behavior experiments and only the best ones were selected for the subsequent column experiments. Surfactants which showed high contaminant solubilization, fast coalescence times, and the absence of liquid crystal phases and gels during the phase behavior experiments were tested in soil column experiments. The primary objective of the soil column experiments was to identify surfactants that recovered at least 99% of the contaminant. The secondary objective was to identify surfactants that show low adsorption and little or no loss of hydraulic conductivity during the column experiments. Results demonstrated that up to 99.9% of the contaminants were removed as a result of surfactant flooding of the soil columns. The addition of xanthan gum polymer to the surfactant solution was shown to increase remediation efficiency as a lower volume of surfactant was required for recovering a given volume of NAPL. Based on these experimental results, guidelines for designing highly efficient and robust surfactant floods have been developed and applied to a field demonstration.

- by Gary Pope and +1
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- Multidisciplinary, Contaminant hydrology, Xanthan Gum, Laboratory experiment

The objective of this study was to characterize the temporal behavior of contaminant mass discharge, and the relationship between reductions in contaminant mass discharge and reductions in contaminant mass, for a very heterogeneous, highly contaminated source-zone field site. Trichloroethene is the primary contaminant of concern, and several lines of evidence indicate the presence of organic liquid in the subsurface. The site is undergoing groundwater extraction for source control, and contaminant mass discharge has been monitored since system startup. The results show a significant reduction in contaminant mass discharge with time, decreasing from approximately 1 to 0.15 kg/d over five years. Two methods were used to estimate the mass of contaminant present in the source area at the initiation of the remediation project. One was based on a comparison of two sets of core data, collected 3.5 years apart, which suggests that a significant (~80%) reduction in aggregate sedimentphase TCE concentrations occurred between sampling events. The second method was based on fitting the temporal contaminant mass discharge data with a simple exponential source-depletion function. Relatively similar estimates, 784 and 993 kg, respectively, were obtained with the two methods. These data were used to characterize the relationship between reductions in contaminant mass discharge (CMDR) and reductions in contaminant mass (MR). The observed curvilinear relationship exhibits a reduction in contaminant mass discharge essentially immediately upon the initiation of mass reduction. This behavior is consistent with a system wherein significant quantities of mass are present in hydraulically poorly accessible domains for which mass removal is influenced by rate-limited mass transfer. The results obtained from the present study are compared to those obtained from other field studies to evaluate the impact of system properties and conditions on mass-discharge and mass-removal behavior. The results indicate that factors such as domain scale, hydraulicgradient status (induced or natural), and flushing-solution composition had insignificant impact on the CMDR-MR profiles and thus on underlying mass-removal behavior. Conversely, source-zone age, through its impact on contaminant distribution and accessibility, was implicated as a critical factor influencing the nature of the CMDR-MR relationship.

- by Kenneth Carroll
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- Groundwater, Multidisciplinary, Contaminant hydrology, Trichloroethylene
- by George Hoag
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- Multidisciplinary, Iron, Infrared, X ray diffraction

Stable hydrogen isotopes of two chlorinated solvents, trichloroethylene (TCE) and 1,1,1trichloroethane (TCA), provided by five different manufacturers, were determined and compared to their carbon and chlorine isotopic signatures. The isotope ratio for d 2 H of different TCEs ranged between + 466.9xand + 681.9x , for d 13 C between À 31.57xand À 27.37x , and for d 37 Cl between À 3.19xand + 3.90x . In the case of the TCAs, the isotope ratio for d 2 H ranged between À 23.1xand + 15.1x , for d 13 C between À 27.39xand À 25.84x , and for d 37 Cl between À 3.54x and + 1.39x . As well, a column experiment was carried out to dechlorinate tetrachloroethylene (PCE) to TCE using iron. The dechlorination products have completely different hydrogen isotope ratios than the manufactured TCEs. Compared to the positive values of d 2 H in manufactured TCEs (between + 466.9xand + 681.9x ), the dechlorinated products had a very depleted d 2 H (less than À 300x ). This finding has strong implications for distinguishing dechlorination products (PCE to TCE) from manufactured TCE. In addition, the results of this study show the potential of combining 2 H/ 1 H analyses with 13 C/ 12 C and 37 Cl/ 35 Cl for isotopic fingerprinting applications in organic contaminant hydrogeology. D

- by Shaun Frape
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- Hydrogen, Environmental Monitoring, Multidisciplinary, Contaminant hydrology

A new type of transverse flow, hollow fiber module was evaluated for membrane separation. First, small sections of fabric were woven using silicone rubber hollow fiber membranes and monofilament nylon. Water deoxygenation experiments were conducted on each fabric in a flat cell, yielding mass transfer coefficient (k) values. An optimal fabric construction was identified based on k values exceeding 0.01 cm/s at moderate velocities, low pressure drop, and high membrane packing density.

- by Charles Gooding
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- Engineering, Mass Transfer, Membrane Science, Oxygen Transfer

A respirometry technique can be applied as an effective method to determine the net maximum specific growth rate of autotrophic biomass under both normal conditions and when inhibition occurs. The net maximum specific growth rate of uninhibited autotrophic biomass, expressed as (μ A − b A ), is approximately 0.8 per day [Proceeding of the International Congress on CHISA, Prague, 2002, p. 1].

- by Jan BAEYENS
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- Engineering, Biomass, Population Dynamics, Activated Sludge

Trichloroethylene (TCE) is one of the most common and persistent groundwater contaminants encountered at hazardous waste sites around the world. A growing body of evidence indicates that iron sulfides play an important role in degrading TCE in natural environments and in engineered systems designed for groundwater cleanup. In this study, we investigate transformation processes of iron sulfides and consequent impacts on TCE degradation using batch experimental techniques, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). Our results show that mackinawite is highly reactive toward TCE and no detectable mineralogical changes were detected during the course of reaction. However, freeze-dried FeS transformed to a mixture of mackinawite and greigite during the freeze drying process, with further mineralogical changes during reaction with TCE to lepidocrocite, goethite and pyrite. Newly formed lepidocrocite is a transient phase, with conversion to goethite over time. TCE transformation kinetics show that freeze-dried FeS is 20-50 times less reactive in degrading TCE than non-freeze-dried FeS, and the TCE degradation rate increases with pH (from 5.4 to 8.3), possibly due to an increase of surface deprotonation or electron transfer at higher pH. Results suggest that freeze drying could cause FeS particle aggregation, decreased surface area and availability of reactive sites; it also could change FeS mineralogy and accelerate mineral transformation. These aspects could contribute to the lower reactivity of freeze-dried FeS toward TCE degradation. Modeling results show that FeS transformation in natural environments depends on specific biogeochemical conditions, and natural FeS transformation may affect mineral reactivity in a similar way as compared to the freeze drying process. Rapid transformation of FeS to FeS 2 could significantly slow down TCE degradation in both natural and engineered systems.

- by Richard Wilkin
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- Geology, Geochemistry, Kinetics, Transmission Electron Microscopy

The potential of trichloroethylene (TCE) to induce and non-aromatic growth substrates to support TCE degradation in five strains (Pseudomonas mendocina KR1, Ralstonia pickettii PKO1, Pseudomonas putida F1, Burkholderia cepacia G4, B. cepacia PR1) of toluene-oxidizing bacteria was examined. LB broth and acetate did not support TCE degradation in any of the wild-type strains. In contrast, fructose supported the highest specific levels of TCE oxidation observed in each of the strains tested, except B. cepacia G4. We discuss the potential mechanisms and implications of this observation. In particular, cells of P. mendocina KR1 degraded significant amounts of TCE during cell growth on non-aromatic substrates. Apparently, TCE degradation was not completely constrained by any given factor in this microorganism, as was observed with P. putida F1 (TCE was an extremely poor substrate) or B. cepacia G4 (lack of oxygenase induction by TCE). Our results indicate that multiple physiological traits are required to enable useful TCE degradation by toluene-oxidizing bacteria in the absence of aromatic cosubstrates. These traits include oxygenase induction, effective TCE turnover, and some level of resistance to TCE mediated toxicity.

- by Chris Yeager
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- Microbiology, Kinetics, Biodegradation, Pseudomonas

High Dimensional Model Representation (HDMR) is under active development as a set of quantitative model assessment and analysis tools for capturing high-dimensional input-output system behavior. HDMR is based on a hierarchy of component functions of increasing dimensions. The Random-Sampling High Dimensional Model Representation (RS-HDMR) is a practical approach to HDMR utilizing random sampling of the input variables. To reduce the sampling effort, the RS-HDMR component functions are approximated in terms of a suitable set of basis functions, for instance, orthonormal polynomials. Oscillation of the outcome from the resultant orthonormal polynomial expansion can occur producing interpolation error, especially on the input domain boundary, when the sample size is not large. To reduce this error, a regularization method is introduced. After regularization, the resultant RS-HDMR component functions are smoother and have better prediction accuracy, especially for small sample sizes (e.g., often few hundred). The ignition time of a homogeneous H 2 /air combustion system within the range of initial temperature, 1000 < T 0 < 1500 K, pressure, 0.1 < P < 100 atm and equivalence ratio of H 2 /O 2 , 0.2 < R < 10 is used for testing the regularized RS-HDMR.

- by Tucker Carrington and +1
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- Engineering, Algorithms, Fuzzy Logic, Kinetics

Temperature dependence of reductive trichloroethene (TCE) dechlorination was investigated in an enrichment culture (KB-1 TM ), using lactate or propionate as electron donors at a temperature interval from 4 to 60 1C. Dechlorination was complete to ethene at temperatures between 10 and 30 1C (lactate-amended) and between 15 and 30 1C (propionate-amended). Dechlorination stalled at cis-1,2-dichloroethene (cDCE) at 4 1C (lactate-amended), at and below 10 1C (propionate-amended), and at 40 1C with both electron donors. No dechlorination of TCE was observed at 50 and 60 1C. Concentrations of Dehalococcoides had increased or remained constant after 15 days of incubation at temperatures involving complete dechlorination to ethene. Temperature dependence of dechlorination rates was compared using zero order degradation kinetics and a Monod growth-rate model for multiple electron acceptor usage with competition. Maximum growth rates (m) and zero order degradation rates were highest for TCE dechlorination at 30 1C with lactate as substrate (m TCE of 7.0070.14 days À1 ). In general, maximum growth rates and dechlorination rates of TCE were up to an order of magnitude higher than rates for utilization of cis-dichloroethene (cDCE, m cDCE up to 0.1770.02 days À1 ) and vinyl chloride (VC, m VC up to 0.5270.09 days À1 ). Temperature dependence of maximum growth rates and degradation rates of cDCE and VC were similar and highest at 15-30 1C, with growth rates on cDCE being lower than on VC. This study demonstrates that bioaugmentation of chlorinated ethene sites may be more efficient at elevated temperatures.

- by Poul Bjerg
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- Water, Kinetics, Water Purification, Multidisciplinary

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 lg 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.

- by Reza Ahmadkhaniha
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- Exposure Assessment, Environmental Sciences, Exposure, CHEMICAL SCIENCES

The primary goals for most ground water capture systems (i.e., pump-and-treat systems) are that (1) all contaminants within zones of interest will eventually be captured and (2) the extraction and reinjection wells are best located and operated at optimal flow rates, creating hydraulically efficient flow systems. A new tool, MODular ALLocation (MODALL), is presented to aid in the design and assessment of capture systems. MODALL uses the MODFLOW-calculated cell-by-cell flow terms to evaluate internodal flow balances to determine the percentage of flow in each cell which has either originated from a given source(s) or flows to a specified sink(s). Output from MODALL can be easily displayed in isopleths of ''capture fraction'' (CF) to indicate the certainty or strength of capture in various areas. MODALL results are compared to the results from an analytical solution, a pathline analysis using MODPATH, and solute transport simulation with MT3DMS. A brief case study is also presented where MODALL is used to optimize an existing pump-and-treat system to more effectively and more efficiently contain a 5000-m long plume.

- by Liliana Cecan
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- Water, Environmental Monitoring, Software, Water Supply

A mesocosm system was designed to study evaporation kinetics and transport of TCE in flowing surface water. The airtight unit, with a total internal volume of 52.01 × 10−2 m3, was fabricated with glass and Teflon material, and was provided with 8.53 m long channel to simulate water flow in an open channel. The peristaltic pumps, connected to the inlet and the outlet of the mesocosm, provided a constant water flow through the channels. The experimental studies were conducted at two different velocities, 9.42 × 10−3 and 4.71 × 10–3 m/s, respectively. For both the velocities, a tracer (NaBr) test confirmed uniform water flow in the channels. The total length and the length between the sampling ports were found sufficient to record gradual decrease in TCE concentrations along the direction of the flow in the channels. The volatilization coefficient for TCE was found to be 0.49 and 1.07 h−1 for the experiments conducted at lower and higher water velocities, respectively. The TCE evaporation half life (t 1/2) and the corresponding evaporation half distance (d 1/2) were 1.41 h and 23.98 m for lower velocity, and 0.65 h and 21.96 m for higher velocity, respectively.

- by PRABHAKAR PANT
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- Kinetics, Evaporation, Water Pollution, Instrumentation

Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as electron donors by microorganisms. This review presented the current research trend in understanding biodegradation mechanisms with regard to their field applications. All the techniques used are evaluated, with the focus being on various factors that influence the process and the outcome.

- by PRABHAKAR PANT
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- Earth Sciences, Biodegradation, Environmental Sciences, Soil Microbiology

This paper focuses on the kinetics of photocatalytic removal and carbon mineralization of gaseous trichloroethylene (TCE) on near-UV irradiated TiO 2 Degussa P25. Experiments were carried out in a flat-plate photoreactor at TCE inlet concentrations of 100-500 ppmv, relative humidities (RH) of 0-62% and gas residence times of 2.5-60.3 s. Gas residence time distribution (RTD) curves revealed an axial dispersed plug flow in the photoreactor with Peclet numbers above 59.4. For all experimental conditions, the carbon mineralization efficiency (5.1-73.0%) was lower than the removal efficiency (8.6-99.9%) and dichloroacetylchloride (DCAC) was detected as a gas-phase degradation product. TCE removal efficiencies increased with lower TCE inlet concentrations, lower RH and higher gas residence times. Evaluating different kinetic models by least squares analysis, it was shown that the Langmuir-Hinshelwood (LH) model could not give an adequate fitting to the experimental results. A new kinetic model, explicitly taking into account electron-hole pair reactions, was developed based on linear TCE adsorption-desorption equilibrium and first order reaction kinetics. The new kinetic model described the experimental results in a more accurate way, as exemplified by a more randomly distributed set of residuals and by a reduction of the sum of squares (SSQ) by a factor 1.7-8.5. The effect of TCE gas-phase concentration, RH and light intensity on adsorption-desorption kinetics, electron-hole concentrations and chemical conversion rates is discussed. #

- by Alex De Visscher
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- Environmental Engineering, Chemical Engineering, Kinetics, Titanium dioxide

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

- by Anke Neumann
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- Microbiology, Kinetics, Medical Microbiology, Energy Metabolism

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.

- by Felicia Cummings and +1
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- Minerals, Water Pollution, Multidisciplinary, Phylogeny

This work evaluates the possibility to tailor the gas separation properties of elastomeric block copolyamide membranes by means of room temperature ionic liquid (RTIL), based on the 1-n-alkyl-3methylimidazolium cation. Polymeric gel membranes were prepared by adding from 20 to 80 wt.% of 1-butyl-3-methylimidazolium trifluoromethanesulfonate, [BMIM][CF 3 SO 3 ] to Pebax Ò 1657 and Pebax Ò 2533.

- by Karel Friess and +1
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- Engineering, Environmental Science, Mass Transfer, Membrane Science

TCE dechlorination was often partial, or absent, but rarely complete to ethane. • Chlorine number reduction provided a convenient quantitative attenuation metric. • Dechlorination is driven by transient hyporheic zone flow and organic matter input. • Dechlorination is inhibited by no hyporheic zone, oxic and high sulphate conditions. • Attenuation will be poorly constrained without detailed reach-scale investigation.

- by Juliana G Freitas
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- Groundwater, Environmental Monitoring, Rivers, Trichloroethylene

It was recently demonstrated that some drugs modulate in vitro metabolism of trichloroethylene (TCE) in humans and rats. The objective was to assess in vivo interactions between TCE and three drugs: naproxen (NA), valproic acid (VA), and salicylic acid (SA). Animals were exposed to TCE by inhalation (50 ppm for 6 h) and administered a bolus dose of drug by gavage, equivalent to 10-fold greater than the recommended daily dose. Samples of blood, urine, and collected tissues were analyzed by headspace gas chromatography coupled to an electron capture detector for TCE and metabolites (trichloroethanol [TCOH] and trichloroacetate [TCA]) levels. Coexposure to NA and TCE significantly increased (up to 50%) total and free TCOH (TCOH total and TCOH free, respectively) in blood. This modulation may be explained by an inhibition of glucuronidation. VA significantly elevated TCE levels in blood (up to 50%) with a marked effect on TCOH total excretion in urine but not in blood. In contrast, SA produced an increase in TCOH total levels in blood at 30, 60, and 90 min and urine after coexposure. Data confirm in vitro observations that NA, VA, and SA affect in vivo TCE kinetics. Future efforts need to be directed to evaluate whether populations chronically medicated with the considered drugs display greater health risks related to TCE exposure.

- by Sami Haddad
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- Risk assessment, Environmental Sciences, CHEMICAL SCIENCES, Theoretical Models

Compound-specific stable isotope analysis (CSIA) using gas chromatography-isotope ratio mass spectrometry (GC/IRMS) has developed into a mature analytical method in many application areas over the last decade. This is in particular true for carbon isotope analysis, whereas measurements of the other elements amenable to CSIA (hydrogen, nitrogen, oxygen) are much less routine. In environmental sciences, successful applications to date include (i) the allocation of contaminant sources on a local, regional, and global scale, (ii) the identification and quantification of (bio)transformation reactions on scales ranging from batch experiments to contaminated field sites, and (iii) the characterization of elementary reaction mechanisms that govern product formation. These three application areas are discussed in detail. The investigated spectrum of compounds comprises mainly n-alkanes, monoaromatics such as benzene and toluene, methyl tert-butyl ether (MTBE), polycyclic aromatic hydrocarbons (PAHs), and chlorinated hydrocarbons such as tetrachloromethane, trichloroethylene, and polychlorinated biphenyls (PCBs). Future research directions are primarily set by the state of the art in analytical instrumentation and method development. Approaches to utilize HPLC separation in CSIA, the enhancement of sensitivity of CSIA to allow field investigations in the µg L -1 range, and the development of methods for CSIA of other elements are reviewed. Fur-thermore, an alternative scheme to evaluate isotope data is outlined that would enable estimates of position-specific kinetic isotope effects and, thus, allow one to extract mechanistic chemical and biochemical information.

- by Stefan B Haderlein and +1
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- Engineering, Environmental Science, Stable Isotope Analysis, Mass Spectrometry
- by Bruce Bugbee
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- Water, Multidisciplinary, Environmental science and technology, Carbon Isotopes