Presence Of Trichloroethylene Research Articles

Evaluation of alkaline activated sodium persulfate sustained release rod for the removal of dissolved trichloroethylene

The presence of trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) in the subsurface can generate a dissolved phase plume in groundwater. This study developed an alkaline activated sodium persulfate (SPS) sustained release oxidation rod (alkaline SPS SR-Rod) for long-term in situ chemical oxidation accelerated treatment of TCE dissolved from TCE DNAPL, by creating a greater concentration gradient at the TCE DNPL boundary. The dissolution of TCE DNAPL (1 mL) in water (280 mL) generated ~700 mg L−1, with a volumetric mass transfer coefficient (kLa) of 0.0187 d−1. The alkaline SPS SR-Rod system had a kLa of 0.013 d−1 for TCE dissolution at early stage, and thereafter aqueous TCE concentration remained below ~10 mg L−1 over 60 d of reaction. An SPS SR-Rod life-span of 186 d, for 90% of SPS released from the rod, was estimated. In the soil-water system, aqueous TCE was maintained < 3 mg L− 1 throughout the reaction and the soil oxidant demand was determined to be ~4 g-SPS/kg-soil in the alkaline SPS SR-Rod system. These results revealed that the use of the alkaline SPS SR-Rod can be effective as a method of treating dissolved TCE released from DNAPL contamination, and thereby accelerating TCE DNAPL removal.

Enhanced Performance of Supported Ternary Metal Catalysts for the Oxidation of Toluene in the Presence of Trichloroethylene

Chlorinated volatile organic compounds (CVOCs), even in small quantities, can cause Pt-based catalyst poisoning. Improving the low-temperature chlorine resistance of catalysts is of vital importance for industrial application, although it remains challenging. Considering actual industrial production, a TiO2-supported ternary metal catalyst was prepared in this work to study the catalytic oxidation of multicomponent VOCs (toluene and trichloroethylene (TCE)). Among all of the samples, PtWRu/TiO2 and PtWCr/TiO2 exhibited the best catalytic performance for toluene oxidation. In the mixed VOC oxidation, the PtWCr/TiO2 sample showed the best catalytic activity for toluene combustion (a toluene conversion of 90% was achieved at 258 °C and a space velocity of 40,000 mL g−1 h−1, and the specific reaction rate and turnover frequency at 215 °C were 44.9 × 10−6 mol gPt−1 s−1 and 26.2 × 10−5 s−1). The PtWRu/TiO2 sample showed the best catalytic activity for TCE combustion (a TCE conversion of 90% was achieved at 305 °C and a space velocity of 40,000 mL g−1 h−1, and the specific reaction rate and turnover frequency at 270 °C were 9.0 × 10−6 mol gPt−1 s−1 and 7.3 × 10–5 s−1). We concluded that the ternary metal catalysts could greatly improve chlorine desorption by increasing the active lattice oxygen mobility and surface acidity, thus reducing chlorinated byproducts and other serious environmental pollutants. This work may serve as a reasonable design reference for solving more practical industrial production emissions of multicomponent VOCs.

Electrochemical Oxidation of Perfluorooctanesulfonate by Magnéli Phase Ti4O7 Electrode in the Presence of Trichloroethylene

This study examined the degradation of perfluorooctanesulfonate (PFOS) in electrochemical oxidation (EO) processes in the presence of trichloroethylene (TCE). The EO experiment was performed in a gas-tight reactor using Magnéli phase titanium suboxide (Ti4O7) as the anode. The experimental data demonstrated that 75% of PFOS (2 μM) was degraded at 10 mA/cm2 current density in 30 min without TCE present in the solution, while the presence of 76 μM TCE apparently inhibited the degradation of PFOS, reducing its removal down to 53%. Defluorination ratio suggested that PFOS was significantly mineralized upon EO treatment, and it appeared to be not influenced by the presence of TCE. The respective pseudo-first order rate constants (kobs) of PFOS removal were 0.0471 and 0.0254 min-1 in the absence and presence of TCE. The degradation rates of both PFOS and TCE increased with current density rising from 2.5 to 20 mA/cm2. In the presence of TCE, chloride, chlorate, and perchlorate were formed that accounted for 79.7 %, 5.53%, and 1.51% of the total chlorine at 60 min. This work illustrates the promise of the Magnéli phase Ti4O7 electrode based electrochemical oxidation technology for degrading per- and polyfluoroalkyl substances (PFASs) and co-contaminants in groundwaters.

Performance investigation of Zeolitic Imidazolate Framework – 8 (ZIF-8) in the removal of trichloroethylene from aqueous solutions

The presence of trichloroethylene in the groundwater has caused major concerns on a global scale. In this study, the effect of different parameters such as contact time (15–120 min), pH (3–12), adsorbent dose (0.05–0.35 g/L), and the initial concentration of TCE (5–50 μg/L) was studied. The structure of the adsorbent was determined by XRD, SEM, FT-IR, BET, and TEM. In this study, Freundlich and Langmuir isotherm models were used to calculate the equilibrium constants. Residual Trichloroethylene was measured using the GC-Mass. The removal rate of trichloroethylene increased with increasing contact time and adsorbent dosage while it decreased after an increase in pH and initial concentration of trichloroethylene. The best pH and adsorbent dose for the removal of trichloroethylene was 7.5 and 0.313 g/L, respectively. The optimum removal efficiency for TCE removal by ZIF-8 adsorbent was 96.29%. Kinetic studies showed that adsorption of TCE by ZIF-8 follows a pseudo second order. Langmuir isotherm with an R2 of 0.9926 for TCE was the best graph for the experimental data. The maximum adsorption capacity was 136.33 mg/g. The results showed that ZIF-8 adsorbent could be effective in removal of trichloroethylene from aqueous solution.

Cyclodextrin-enhanced 1,4-dioxane treatment kinetics with TCE and 1,1,1-TCA using aqueous ozone

Enhanced reactivity of aqueous ozone (O3) with hydroxypropyl-β-cyclodextrin (HPβCD) and its impact on relative reactivity of O3 with contaminants were evaluated herein. Oxidation kinetics of 1,4-dioxane, trichloroethylene (TCE), and 1,1,1-trichloroethane (TCA) using O3 in single and multiple contaminant systems, with and without HPβCD, were quantified. 1,4-Dioxane decay rate constants for O3 in the presence of HPβCD increased compared to those without HPβCD. Density functional theory molecular modeling confirmed that formation of ternary complexes with HPβCD, O3, and contaminant increased reactivity by increasing reactant proximity and through additional reactivity within the HPβCD cavity. In the presence of chlorinated co-contaminants, the oxidation rate constant of 1,4-dioxane was enhanced. Use of HPβCD enabled O3 reactivity within the HPβCD cavity and enhanced 1,4-dioxane treatment rates without inhibition in the presence of TCE, TCA, and radical scavengers including NaCl and bicarbonate. Micro-environmental chemistry within HPβCD inclusion cavities mediated contaminant oxidation reactions with increased reaction specificity.

Determination of trichloroethylene by using self-referenced SERS and gold-core/silver-shell nanoparticles.

A surface-enhanced Raman scattering (SERS) method has been developed to determine the concentration of trichloroethylene (TCE) in environmental water. Au-core/Ag-shell nanoparticles containing 4-mercaptophenylboronic acid (4-MPBA) between the core and shell are used as the SERS substrate. 4-MPBA serves as an internal reference with a Raman shift at 534cm-1. TCE reacts with 4-mercaptopyridine (4-MPy) in a so-called Fujiwara reaction. With the presence of TCE in water, the consumption of 4-MPy results in a change in the intensity of its Raman signal at 1220cm-1. The ratio of the Raman shift at 1220cm-1 and 534cm-1 decreases linearly in the 0.2 to 1.0μM TCE concentration range, and the detection limit of TCE is as low as 8ppb (60nM). The method has been successfully applied to the determination of TCE in spiked lake water. Graphical abstract Gold-core/silver-shell nanoparticles with internal reference embedded have been fabracated to improve the quantitative measurement of SERS. These nanoparticles as SERS substrates, are used to indirectly quantify the concentration of trichloroethylene (a typical halogenated organic compound) by the consumption of 4-mercaptopyridine through the Fujiwara reaction.

Anaerobic Bioremediation Performance and Indigenous Microbial Communities in Treatment of Trichloroethylene/Nitrate-Contaminated Groundwater

Abstract To meet recommended drinking water standards, developing effective methods for eliminating mixed contamination of trichloroethylene (TCE) and nitrate, the two most common groundwater contaminants, is critical. However, many previous studies examined bioremediation performance only for single contaminants. In this study, the performance of indigenous microbial communities on anaerobic removal of TCE/nitrate mixed contamination in groundwater was investigated. Central composite design (CCD) and response surface methodology (RSM) predicted that for bioremoval of 3.87 mg/L TCE combined with 50 mg/L nitrate-N, the optimal conditions were: pH 8.01, 20.18°C, and a powder activated carbon (PAC) dosage of 4.04% (w/v). Under these conditions, 100% of both TCE and nitrate could be removed with no by-product accumulation after 14 days. Presence of TCE and nitrate did not inhibit bioremoval performance for mixed contaminations, although pH and temperature had a more significant influence on mixed compared to ...

From carbon dots to multipods — The role of nickel particle shape and size

In an attempt to synthesize carbon tripod structures in high yield, we have observed that a wide range of carbon structures are formed as the Ni particle size and shape varied. In using trichloroethylene (TCE), acetylene and their mixtures as a carbon source to make carbon materials over Ni nanoparticle catalysts in a chemical vapor deposition (CVD) process, we have observed that the Ni particle size and shape impacts dramatically on the carbon structure formed. The synthesis of the Ni catalyst was achieved by reduction of Ni(acetate)2 with hydrazine (35%). Ex-situ TEM analysis of the reduced NiO particles revealed that the Ni particles underwent a morphological change in the presence of TCE (and H2) with change in (i) temperature (350–750°C) and (ii) H2 flow rate (20–150mL/min) and that this affected the shape of the carbon material that formed. In the absence of TCE only particle sintering occurred. At T=350°C the Ni particles are covered by carbon to form carbon dots. With an increase in T the carbon shapes changed to a bimodal (400°C) and then to a tripod-like structure (450°C) and eventually multipod-like structures (500°C). Carbon fibers were mainly observed for T>500°C. Similar shape changes were observed at 450°C as a function of reaction time and H2 flow rate. It was also found that when acetylene or an acetylene/trichloroethylene mixture was used at T=450°C, helical and linear fibers were produced. The TEM data reveal that the fragmentation and sintering of the Ni (by the carbon source and other factors) to give differently sized Ni particles, especially as it is affected by H2, determines the morphology of the carbon materials grown from the Ni. The TCE has the ability to restructure the Ni particles and this leads to the unusual carbon shapes observed. Thus the carbon and the catalyst influence each other during the growth of the carbon materials.

Effect of trichloroethylene and tetrachloroethylene on methane oxidation and community structure of methanotrophic consortium

The methane oxidation rate and community structure of a methanotrophic consortium were analyzed to determine the effects of trichloroethylene (TCE) and tetrachloroethylene (PCE) on methane oxidation. The maximum methane oxidation rate (Vmax ) of the consortium was 326.8 μmol·g-dry biomass−1·h−1, and it had a half-saturation constant (Km ) of 143.8 μM. The addition of TCE or PCE resulted in decreased methane oxidation rates, which were decreased from 101.73 to 5.47–24.64 μmol·g-dry biomass−1·h−1 with an increase in the TCE-to-methane ratio, and to 61.95–67.43 μmol·g-dry biomass−1·h−1 with an increase in the PCE-to-methane ratio. TCE and PCE were non-competitive inhibitors for methane oxidation, and their inhibition constants (Ki ) were 33.4 and 132.0 μM, respectively. When the methanotrophic community was analyzed based on pmoA using quantitative real-time PCR (qRT-PCR), the pmoA gene copy numbers were shown to decrease from 7.3 ± 0.7 × 108 to 2.1–5.0 × 107 pmoA gene copy number · g-dry biomass−1 with an increase in the TCE-to-methane ratio and to 2.5–7.0 × 107 pmoA gene copy number · g-dry biomass−1 with an increase in the PCE-to-methane ratio. Community analysis by microarray demonstrated that Methylocystis (type II methanotrophs) were the most abundant in the methanotrophic community composition in the presence of TCE. These results suggest that toxic effects caused by TCE and PCE change not only methane oxidation rates but also the community structure of the methanotrophic consortium.

Trichloroethylene (TCE) biodegradation and its effect on sulfate reducing activity in enriched sulfidogenic cultures prevenient from a UASB maintained at 20 °C

Enriched sulfidogenic microorganisms sampled from a UASB reactor operated at room temperature were evaluated on their sulfate reducing activity (SRA) in the presence of trichloroethylene (TCE) (200, 500 and 900 μM) in order to determine the degree of inhibition on the sulfidogenic microorganisms. The microcosms were incubated at initial sulfate (SO4−2) concentration of 6000 mg/L with a mixture of volatile fatty acids (VFA's) as substrate (acetate, propionate and butyrate). SRA in the microcosms before TCE addition ranged from 400 ± 258 to 8290 ± 630 mg COD-H2S g−1 VSS d−1, after TCE addition the SRA ranged from 5 to 1500 mg COD-H2S g−1 VSS d−1. The lowest SRA observed was due to the highest TCE biodegradation (over 90%) yielding ethene as product of the TCE biodegradation within two weeks. The sulfide (H2S) concentration in the microcosms was varied from 40 to 700 mg/L, except for the transient interruption of sulfate reduction when TCE was biodegraded. The SRA in the microcosms was low but steadily observed in the enrichments after TCE biodegradation suggesting that it is possible to maintain a high biogenic sulfide production in the presence of the pollutant. Therefore the enrichments could be useful for further applications such as heavy metals precipitation along with biodegradation of moderate TCE concentrations.

Temperature dependent (37–15 °C) anaerobic digestion of a trichloroethylene-contaminated wastewater

The impact of a trichloroethylene (TCE) contaminated wastewater on the microbial community structure of an anaerobic granular biomass at 15°C compared to 37°C was investigated. Four expanded granular sludge bed (EGSB) bioreactors (R1–R4) were employed in pairs at 37 and 15°C. The influents of one of each pair were supplemented with increasing concentrations of TCE (max. 60mgl−1). At 37°C, stable operation was maintained with 88% COD removal and >99% TCE removal at maximum influent TCE concentrations. R3 performance decreased at influent TCE concentration of 60mgl−1, although TCE removal rates of >97% were recorded. Archaeal community analysis via clone library and quantitative polymerase chain reaction (qPCR) analysis, and bacterial community analysis via denaturing gradient gel electrophoresis (DGGE), indicated that temperature resulted in a greater change in community structure than the presence of TCE, and clones related to cold adaptation of biomass were identified at 15°C.

Mobility Enhancement of Mn Oxide during Permanganate Oxidation of TCE

Manganese (Mn) oxide precipitation during in situ permanganate oxidation of organic compounds can cause pore clogging, reduce permeability, and increase resistance to mass transfer. Stability of Mn oxide is required to enhance oxidation effectiveness. Batch tests were conducted at eight polyphosphate (PP) to permanganate () mass ratios (0 to 8) at three MnO4−1 concentrations (500, 1000, or 2000 mg/L) for identifying mass ratios to maximize stability of Mn oxide produced in the presence of trichloroethylene (TCE). In general, stability of Mn oxide was the maximum at mass ratio of approximately 4. Three column tests were designed to investigate the impact of PP on overall removal of 4.6 or 7.0 g TCE emplaced as nonaqueous phase liquid within the column porous media. Water flush, chemical flush using alone (1000 mg/L), and chemical flush using (1000 mg/L) and PP (4000 mg/L) were conducted. Mass removal of TCE and changes in media permeability were estimated over a period of 78 to 312 h (12 to 49 pore volumes [PVs]). Column tests demonstrated enhanced removal (~90%) of TCE during chemical flush with and PP in 12 PVs as compared with approximately 64% during ‐only flush and approximately 26% during water flush. Pressure drop changes across the column captured change in media permeability and revealed that water flush and PP and flush caused significantly lower flow resistance as compared with ‐only flush. These results indicate that PP was capable of mobilizing Mn oxide away from the reaction zones, thereby reducing pore clogging and enabling better and long‐term contact between TCE and the aqueous phase.

Sonolysis of trichloroethylene and carbon tetrachloride in aqueous solution

Herein, the ultrasonic degradation of trichloroethylene (TCE) and carbon tetrachloride (CT) are reported. The degradation rate for TCE increased by 27% with a decrease in the initial concentration of TCE from 10 to 1 mg L −1, while the degradation rate of CT was not influenced significantly (<3%) at varying initial concentrations. The addition of t-BuOH, a hydroxyl radical scavenger, decreased the degradation rate of TCE to 22–33%. However, this addition did not affect the degradation rate of CT. Sonolysis of aqueous mixtures of TCE and CT indicated that the degradation rate of TCE was enhanced significantly in the presence of CT, while the degradation rate of CT was slightly inhibited in the presence of TCE. The enhancement of TCE degradation is attributed to both the increase of hydroxyl radical concentration by scavenging of CT for hydrogen atoms and the generation of chlorine-containing radicals such as CCl 3 , CCl 2 , Cl , and HClO from pyrolysis of CT during sonolysis of CT.

PH dependence of persulfate activation by EDTA/Fe(III) for degradation of trichloroethylene

The ability of free ferrous ion activated persulfate (S 2O 8 2−) to generate sulfate radicals (SO 4 − ) for the oxidation of trichloroethylene (TCE) is limited by the scavenging of SO 4 − with excess Fe 2+ and a quick conversion of Fe 2+ to Fe 3+. This study investigated the applicability of ethylene-diamine-tetra-acetic acid (EDTA) chelated Fe 3+ in activating persulfate for the destruction of TCE in aqueous phase under pH 3, 7 and 10. Fe 3+ and EDTA alone did not appreciably degrade persulfate. The presence of TCE in the EDTA/Fe 3+ activated persulfate system can induce faster persulfate and EDTA degradation due to iron recycling to activate persulfate under a higher pH condition. Increasing the pH leads to increases in pseudo-first-order-rate constants for TCE, S 2O 8 2− and EDTA degradations, and Cl generation. Accordingly, the experiments at pH 10 with different EDTA/Fe 3+ molar ratios indicated that a 1/1 ratio resulted in a remarkably higher degradation rate at the early stage of reaction as compared to results by other ratios. Higher persulfate dosage under the EDTA/Fe 3+ molar ratio of 1/1 resulted in greater TCE degradation rates. However, increases in persulfate concentration may also lead to an increase in the rate of persulfate consumption.

Biodegradation of trichloroethylene (TCE) by methanotrophic community

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

Trichloroethylene Degradation by Zero Valent Iron Activated Persulfate Oxidation

The present study describes the use of zero valent iron (Fe0 ) as a source for ferrous ion activated persulfate (PS) oxidation of trichloroethylene (TCE). The experimental results indicated that in the absence of TCE there was a lag time for persulfate decomposition when the reaction was activated by Fe0 . An initial pH drop in the Fe0 /PS system to acidic conditions was accompanied by the persulfate decomposition and a decrease in oxidation-reduction potential (ORP) values. Furthermore, in the TCE/Fe0 /PS system, the rapid TCE degradation was accompanied by the rapid persulfate decomposition and chloride ion formation as evidence of TCE mineralization. SEM images of Fe0 before and after persulfate oxidation exhibited significant corrosions of Fe0 . Acicular aggregate formation in the absence of TCE and coarse aggregate formation in the presence of TCE were observed. Moreover, the XRD spectrum revealed the formation of magnetite over the surface of Fe0 after contact with persulfate. Thus, Fe0 activated pe...

Competitive Effects of Trichloroethylene on Cr(VI) Removal by Zero-Valent Iron

Eleven columns were set up under various groundwater geochemistry conditions to investigate the competitive effect of trichloroethylene (TCE) on hexavalent chromium [Cr(VI)] removal by zero-valent iron ( Fe0 ) . They were found to be electron competitors in the redox reactions. In the presence of TCE, the Cr(VI) removal capacities of Fe0 were decreased by about 40% when compared with their respective Cr(VI) removal capacities with identical groundwater geochemistry but without TCE. The specific reaction rate constant ( kSA ) of TCE was decreased by about 50% when Cr(VI) was singly applied. The kSA of TCE was further decreased by 75% in the presence of both Cr(VI) and carbonate. However, there was no apparent effect on the kSA of TCE when Cr(VI), hardness and carbonate were all present. It revealed that TCE was a stronger electron competitor of Cr(VI) and the degradation of TCE became more favorable when both hardness and carbonate were present. This suggests that the passivated precipitates formed on the ...

Hindered gas-phase partitioning of trichloroethylene from aqueous cyclodextrin systems: implications for treatment and analysis.

Chemically enhanced flushing has shown great promise for attenuating subsurface nonaqueous phase liquid (NAPL) contamination. One particular chemically enhanced remediation technology is cyclodextrin enhanced flushing (CDEF). CDEF has been demonstrated as a viable alternative to conventional and innovative remediation methods. However, the presence of cyclodextrin (CD) in solution complicates the treatment and analysis of volatile organic compounds, such as trichloroethylene (TCE). The principal reason for the complications is the presence of TCE in three compartments instead of two, i.e., the aqueous solution, the vapor phase, and complexed inside the soluble CD molecule. Aqueous TCE-CD systems were examined at various concentration and temperature conditions and their respective Henry's law constants were measured. The presence of CD significantly decreased Henry's law constant of TCE. On the basis of these results, a quantitative model was developed to predict the additional effort that becomes necessary when air-stripping TCE from CDEF flushing solution. The modeling results demonstrate that the presence of CD requires significantly higher gas flow rates or longer residence times of the flushing solution inside an air stripper. Similarly, current gas chromatographic purge-and-trap methods for TCE analysis in CD solution appear to underestimate the aqueous phase TCE concentration if the CD concentration of the sample is not accounted for. Although this model was developed specifically for CD-TCE systems, it is likely that these results have implications for other VOCs and other solubilization enhancing agents, such as surfactants or cosolvents.

A controlled field experiment on groundwater contamination by a multicomponent DNAPL: dissolved-plume retardation

A natural gradient emplaced-source (ES) controlled field experiment was conducted at the Borden aquifer research site, Ontario, to study the transport of dissolved plumes emanating from residual dense nonaqueous-phase liquid (DNAPL) source zones. The specific objective of the work presented here is to determine the effects of solute and co-solute concentrations on sorption and retardation of dissolved chlorinated solvent-contaminant plumes. The ES field experiment comprised a controlled emplacement of a residual multicomponent DNAPL below the groundwater table and intensive monitoring of dissolved-phase plumes of trichloromethane (TCM), trichloroethylene (TCE), and perchloroethylene (PCE) plumes continuously generated in the aquifer down gradient from gradual source dissolution. Estimates of plume retardation (and dispersion) were obtained from 3-D numerical simulations that incorporated transient source input and flow regimes monitored during the test. PCE, the most retarded solute, surprisingly exhibited a retardation factor ∼3 times lower than observed in a previous Borden tracer test by Mackay et al. [Water Resour. Res. 22 (1986) 2017] conducted ∼150 m away. Also, an absence of temporal trend in PCE retardation contrasted with the previous Borden test. Supporting laboratory studies on ES site core indicated that sorption was nonlinear and competitive, i.e. reduced sorption of PCE was observed in the presence of TCE. Consideration of the effects of relatively high co-solute (TCE) concentration (competitive sorption) in addition to PCE concentration effects (nonlinear sorption) was necessary to yield laboratory-based PCE retardation estimates consistent with the field plume values. Concentration- and co-solute-based sorption and retardation analysis was also applied to the previous low-concentration pulse injection test of Mackay et al. [Water Resour. Res. 22 (1986) 2017] and was able to successfully predict the temporal field retardation trends observed in that test. While it is acknowledged that other “nonideal transport” effects may contribute, our analysis predicts differences in the PCE retardation magnitude and trend between the two experiments that are consistent with field observations based on the marked solute concentration differences that resulted from contrasting source conditions. Solute and co-solute concentration effects have heretofore received little attention, but may have wide significance in aquifers contaminated by point-source pollutants because many plumes contain mixed solutes over wide concentration ranges in strata that are likely subject to nonlinear sorption.

Identification of trichloroethylene and its metabolites in human seminal fluid of workers exposed to trichloroethylene.

We have investigated the potential of the male reproductive tract to accumulate trichloroethylene (TCE) and its metabolites, including chloral, trichloroethanol (TCOH), trichloroacetic acid (TCA), and dichloroacetic acid (DCA). Human seminal fluid and urine samples from eight mechanics diagnosed with clinical infertility and exposed to TCE occupationally were analyzed. In in vivo experimental studies, TCE and its metabolites were determined in epididymis and testis of mice exposed to TCE (1000 ppm) by inhalation for 1 to 4 weeks. In other studies, incubations of monkey epididymal microsomes were performed in the presence of TCE and NADPH. Our results showed that seminal fluid from all eight subjects contained TCE, chloral, and TCOH. DCA was present in samples from two subjects, and only one contained TCA. TCA and/or TCOH were also identified in urine samples from only two subjects. TCE, chloral, and TCOH were detected in murine epididymis after inhalation exposure with TCE for 1 to 4 weeks. Levels of TCE and chloral were similar throughout the entire exposure period. TCOH levels were similar at 1 and 2 weeks but increased significantly after 4 weeks of TCE exposure. Chloral was identified in microsomal incubations with TCE in monkey epididymis. CYP2E1, a P450 that metabolizes TCE, was localized in human and monkey epididymal epithelium and testicular Leydig cells. These results indicated that TCE is metabolized in the reproductive tract of the mouse and monkey. Furthermore, TCE and its metabolites accumulated in seminal fluid, and suggested associations between production of TCE metabolites, reproductive toxicity, and impaired fertility.