Abstract  The document presents a compilation of measured values for physiological parameters used in pharmacokinetic modeling. The physiological parameters include body weight, tissue volumes, cardiac output distribution, and respiration parameters. Reference values for use in risk assessment are given for each of the physiological parameters based on analyses of valid measurements obtained from the literature and other reliable sources. The proposed reference values are for generic mice and rats without regard to sex or strain. Reference values for humans are without regard to age or sex. Differences between the sexes in mice, rats, and humans are accounted for by scaling the reference parameters within species on the basis of body weight. Reference physiological parameters are for a 0.025 kg mouse, 0.25 kg rat, and a 70 kg man.

Abstract  Previous studies have demonstrated that alpha-tocopheryl hemisuccinate (TS) protects hepatocyte suspensions from chemical-induced toxicity. It has been suggested that TS cytoprotection is related to unique properties of the TS molecule or is dependent on the cellular release and activity of unesterified alpha-tocopherol (T). To test the unique cytoprotective nature of TS in vivo, the protective ability of T and tocopherol esters against carbon tetrachloride (CCl4)-induced hepatotoxicity in rats was examined. Hepatoprotection [determined by serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and histopathology] was not observed after T (or tocopheryl acetate and tocopheryl nicotinate) administration, even though this treatment resulted in a fivefold elevation in hepatic T content. Only pretreatment with TS (100 mg/kg, intraperitoneally) resulted in partial hepatoprotection against CCl4 (2.9 g/kg, orally) toxicity. These findings suggest that hepatoprotection results not from the cellular accumulation of T but rather from the intact TS molecule. To test this hypothesis, the hepatoprotective capacity of cholesteryl hemisuccinate (CS), unesterified cholesterol, and cholesteryl acetate (CA) was examined against CCl4 toxicity. As observed with the tocopherol derivatives, pretreatment with unesterified cholesterol or CA demonstrated no protective ability. However, when rats were pretreated with CS (100 mg/kg), the hepatotoxic effects of CCl4 (elevated serum AST and ALT levels and centrilobular necrosis) were completely prevented. The prevention of CCl4-induced hepatotoxicity by CS and TS do not appear to result from an alteration in hepatic drug metabolism. These data dearly demonstrate that CS and TS are unique and powerful cytoprotective agents against CCl4 hepatotoxicity in vivo. Furthermore, the protection observed is not the result of cellular T accumulation, but rather appears to depend on the hepatocellular accumulation of the intact TS molecule.

Abstract  The public depends on competent risk assessment from the federal government and the scientific community to grapple with the threat of pollution. When risk reports turn out to be overblown--or when risks are overlooked--public skepticism abounds. This comprehensive and readable book explores how the U.S. Environmental Protection Agency (EPA) can improve its risk assessment practices, with a focus on implementation of the 1990 Clean Air Act Amendments. With a wealth of detailed information, pertinent examples, and revealing analysis, the volume explores the "default option" and other basic concepts. It offers two views of EPA operations: The first examines how EPA currently assesses exposure to hazardous air pollutants, evaluates the toxicity of a substance, and characterizes the risk to the public. The second, more holistic, view explores how EPA can improve in several critical areas of risk assessment by focusing on cross-cutting themes and incorporating more scientific judgment. This comprehensive volume will be important to the EPA and other agencies, risk managers, environmental advocates, scientists, faculty, students, and concerned individuals.

Abstract  The effects of trichloroethylene (79016) and 1,1,1-trichloroethane (71556) on plasma lipoproteins of rats were studied and related to the changes in liver and plasma transaminase activities. The effects were compared with effects of carbon-tetrachloride (56235). Male Fischer-344-rats were used in the study. The solvents were dissolved in 1 milliliter of olive-oil/kilogram of body weight and injected intraperitoneally at 19 hours before sacrifice. On the administration of carbon-tetrachloride at 30 to 1000mg/kg, very low density lipoproteins (VLDL) and high density lipoproteins (HDL) were dose dependently reduced, but the reduction in low density lipoproteins (LDL) was not dose dependent. Injection of trichloroethylene at 30 to 30mg/kg decreased the lipid contents of VLDL and LDL fractions. Trichloroethylene at 1000mg/kg increased VLDL and LDL. The HDL was decreased with increasing doses of trichloroethylene at 30 to 1000mg/kg. VLDL and LDL were increased by treatment with 100 or 300mg/kg 1,1,1-trichloroethane. HDL levels rose at 100 but fell at 1000mg/kg. Liver to body weight ratios were raised with increasing doses of the three compounds. Plasma GOT and GPT activities rose at much higher doses of solvents than dose levels which produce the changes in lipoproteins and the increases in liver weights.

Abstract  Concentrations of 4 chlorinated hydrocarbons, C2H3Cl3 (1,1,1-trichloroethane), CCl4 (tetrachloromethane), C2HCl3 (trichloroethene) and C2Cl4 (tetrachloroethene) have been measured in needles of Scots pine (Pinus sylvestris L.) growing close to two industrial sites and in a rural area in northern Britain. Pentane extracts of pine needles sampled over 14 months were analysed using gas chromatography with electron capture detection. Geometric mean concentrations were not significantly different among the sites, with values (in ng g(-1) dry weight) of 7-15 for C2H3Cl3, 3.2-6.5 for CCl4, 70-240 for C2HCl3 and 11-26 for C2Cl4. There was no evidence of accumulation with needle age, but more exposed sites (e.g. those higher in the canopy) showed significantly larger concentrations. The influence of possible local sources could not be detected.

Abstract  Measured concentrations of relatively nonreactive, anthropogenic halocarbon tracers (CFC-11, CFC-12, CFC-113) were used to infer the time since recharge, or age, of groundwater collected from the Upper Glacial and Magothy Aquifers underlying Brookhaven National Laboratory on Long island, NY. On the basis of the reconstructed historical atmospheric concentrations of CCl4, the initial CCl4 concentration for the precipitation that recharged the aquifer was estimated as a function of age. Correlation of measured and estimated initial CCl4 concentrations within the aquifer, over inferred ages of 0-50 yr, suggested that CCl4 was being removed in situ with a half-life of 14 +/- 4 yr. Groundwater samples collected at the water table had CCl4 concentrations that were less than or equal to 50% of equilibrium with contemporary atmospheric concentrations, suggesting that removal was also significant in the unsaturated zone. Soil gas profiles confirmed that atmospheric CCl4 was being removed from the unsaturated zone, with only similar to 25% of the initial CCl4 being present in the gas phase at a depth of 30 cm, and with no evidence for removal of CFC-11, CFC-12, or CFC-113. A time-series of soil gas profiles collected before and after a major rainfall event indicated that most removal occurred in the top 15 cm of soil. The flux of CCl4 into the soil was estimated to be similar to 8600 +/- 5100 pmol m(-2) d(-1), and removal of CCl4 in soils therefore has the potential to significantly affect the global atmospheric lifetime of this compound. The observed degradation in bulk aerobic environments raises questions concerning the conventional wisdom that CCl4 is degraded significantly only within reducing environments.

Abstract  Carbon tetrachloride (CCl4) induced hepatotoxicity and chloroform (CHCl3) induced nephrotoxicity were evaluated in male Sprague‐Dawley rats pretreated with acetone (A), methyl ethyl ketone (MEK), and methyl isobutyl ketone (MiBK). Dose‐response relationships for A, MEK, and MiBK potentiation of CCl4‐induced hepatotoxicity and CHCl3‐induced nephrotoxicity were compared. A, MEK, and MiBK pretreatment at a dosage of 6.8 mmol/kg, given daily for 3 d, markedly potentiated CCl4‐induced liver toxicity as indicated by a decrease in the CCI4 ED50 to 3.4, 4.6, and 1.8 mmol/kg, respectively, compared to vehicle‐pretreated rats (17.1 mmol/kg). Similarly, pretreatment with these ketones (13.6 mmol/kg) potentiated CHCl3 kidney toxicity but to a lesser degree; CHCl3 ED50 values for vehicle‐, A‐, MEK‐, and MiBK‐pretreated rats were 3.4, 1.6, 2.1, and 2.2 mmol/kg, respectively. Our results indicate a potency ranking profile for the potentiation of CCI4 hepatotoxicity of MiBK >A> MEK and of A > MEK ≥ MiBK for CHCl3 nephrotoxicity. These dissimilar ranking profiles could be due to differences in mechanisms of action for the two target sites.

Abstract  EPA's TEAM Study of personal exposure to volatile organic compounds (VOC) in air and drinking water of 650 residents of seven U.S. cities resulted in the identification of a number of possible sources encountered in peoples' normal daily activities and in their homes. A follow-up EPA study of publicaccess buildings implicated other potential sources of exposure. To learn more about these potential sources, 15 building materials and common consumer products were analyzed using a headspace technique to detect organic emissions and to compare relative amounts. About 10–100 organic compounds were detected offgassing from each material. Four mixtures of materials were then chosen for detailed study: paint on sheetrock; carpet and carpet glue; wallpaper and adhesives; cleansers and a spray pesticide. The materials were applied as normally used, allowed to age 1 week (except for the cleansers and pesticides, which were used normally during the monitoring period), and placed in an environmentally controlled chamber. Organic vapors were collected on Tenax-GC over a 4-h period and analyzed by GC-MS techniques. Emission rates and chamber concentrations were calculated for 17 target chemicals chosen for their toxic, carcinogenic or mutagenic properties. Thirteen of the 17 chemicals were emitted by one or more of the materials. Elevated concentrations of chloroform, carbon tetrachloride, 1,1,1-trichloroethane, n-decane, n-undecane, p-dichlorobenzene, 1,2-dichloroethane and styrene were produced by the four mixtures of materials tested. For some chemicals, these amounts were sufficient to account for a significant fraction of the elevated concentrations observed in previous indoor air studies. We conclude that common materials found in nearly every home and place of business may cause elevated exposures to toxic chemicals.

Abstract  Three hundred chemicals were tested for mutagenicity, under code, in Salmonella typhimurium, using a preincubation protocol. All tests were performed in the absence of exogenous metabolic activation, and in the presence of liver S-9 from Aroclor-induced male Sprague-Dawley rats and Syrian hamsters. The results and data from these tests are presented.

Abstract  The results of the US Environmental Protection Agency, Office of Drinking Water, sampling and analysis of volatile organic compounds (VOCs) in finished water supplies that use groundwater sources are discussed. Concentrations of 29 VOCs in addition to five trihalomethanes and total organic carbon from 945 water supplies were measured. The five most frequently found compounds other than trihalomethanes were trichloroethylene, 1,1 ,1-trichloroethane, tetrachloroethylene, cis- and/or trans-1 ,2-dichloroethylene, and 1,1-dichloroethane. Approximately half of the samples were taken from a random list of water systems, which were subdivided into two sets of systems - those serving fewer than 10,000 persons and those serving more than 10,000 persons. The nonrandom samples were taken from systems selected by the states, using groundwater sources that were likely to show VOCs in drinking water. Large systems in the random sample had a significantly higher frequency of occurrence of VOC contamination than small systems and were also more likely to have higher levels of contamination. (Author 's abatract)

Abstract  Chemically inert substances can be transformed in the body to active intermediates that mediate a variety of toxicities including cellular necrosis, methemoglobinemia, porphyria, tumor formation and mutagenic effects. In addition, many hypersensitive reactions and fetotoxic reactions and probably mediated by active intermediates. In some instances the active intermediate apparently acts by combining reversibly with vitally important intracellular components but in others the intermediate acts by combining covalently with tissue macromolecules. This paper is concerned with some of the factors that affect covalent binding and toxicity of drugs.

Abstract  The influences of amphiphiles, including humic acid (HA) and various types of surfactants, on dechlorination of carbon tetrachloride (CTC) and chloroform (CF) by the nano-scale Fe particles were investigated. Since the amphiphiles would modify the surface tension between the liquid-liquid and solid-liquid interface, in the presence of amphiphile matrix solution the Fe corrosion rate and the parent compound dechlorination rate would be different from those in the ultrapure water. Among the four amphiphile solutions, Fe corrosion rate was the highest in the anionic surfactant sodium dodecyl sulfate (SDS) solution, presumably due to the existence of chemisorption between the hydrophilic head of SDS and Fe particles. The dechlorination rates of CTC and CF could be described with the pseudo-first order kinetic model. The influences of amphiphiles on the dechlorination reaction rate were related to the species of parent compound and concentration of the matrix solution. The influences of HA on the dechlorination of CTC and CF were the most significant compared to other matrix solutions. At relatively low HA concentration (<0.1 g L(-1)), the HA molecules (serving as electron transfer mediator) would significantly accelerate the dechlorination rate of CF. The two-parameter regression with energy of the lowest unoccupied molecular orbital (E(LUMO)) and HA concentration as the descriptors was developed to predict the specific reduction rate constants of chlorinated methanes in HA solution. The analysis of variance (ANOVA) indicated the existence of significant relationship between the dechlorination rate constants and the two descriptors.

Abstract  In this experiment, we studied the different changes in activities and protein levels of each subform of hepatic cytochrome P450 and glutathione S-transferase (GST), in chemical-induced liver injury in rats. Rats were administered 1,1-dichloroethylene (DCE), allyl alcohol (AA), bromobenzene (BB) and N,N-dimethylformamide (DMF) p.o. once every two days for 7 times, and decapitated 18 hr after the last administration. DCE and AA showed stronger hepatic toxicity than BB and DMF, as serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were higher in DCE and AA treated rats than in BB and DMF groups. Anti-cytochrome P450 inhibitable activity of toluene metabolism and/or immunoblot analysis showed that CYP2E1 and CYP2B1/2 were induced by BB and DMF, but not by the other two chemicals; CYP2C11 was greatly decreased by all of the four toxicants; and CYP1A1/2 was slightly reduced by the four treatments. These changes were reflected in testosterone metabolism. Formation of 6 beta- and 7 alpha-hydroxytestosterone from testosterone was enhanced only in DMF-treated rats, whereas that of 2 alpha- and 16 alpha-hydroxytestosterone was reduced by all of the four chemicals. Serum GST activity was increased only in BB and DMF treated rats, but liver cytosolic GST activity was enhanced by all of the four hepatotoxicants, with higher values in BB and DMF groups than in DCE and AA groups. Immunoblot analysis demonstrated that GST Yp was induced by BB and DMF treatments, and Ya and Yc were increased only by BB. GST Yk and Yb1 were not affected by the treatments. The different change patterns of enzymes by a specific toxin and the similar modifying effect on a specific enzyme by different toxins were discussed in relation to the liver damage and to the heterogeneous distribution of enzymes in liver.

Abstract  This position paper delineates the expert recommendations of the Regulatory Affairs Committee of the American Society for Veterinary Clinical Pathology for the use of preclinical, clinical pathology endpoints in assessment of the potential for drug-induced hepatic injury in animals and humans. Development of these guidelines has been based on current recommendations in the relevant preclinical and human clinical trial literature; they are intended to provide a method for consistent and rigorous interpretation of liver-specific data for the identification of hepatic injury in preclinical studies and potential liability for hepatic injury in human patients.

Abstract  By using physiologically based pharmacokinetic (PBPK) modeling coupled with Monte Carlo simulation, the interindividual variability in the concentrations of chemicals in a worker's exhaled breath and urine were estimated and compared with existing biological exposure indices (BEIs). The PBPK model simulated an exposure regimen similar to a typical workday, while exposure concentrations were set to equal the ambient threshold limit values (TLVs) of six industrial solvents (benzene, chloroform, carbon tetrachloride, methylene chloride, methyl chloroform, and trichloroethylene). Based on model predictions incorporating interindividual variability, the percentage of population protected was derived using TLVs as the basis for worker protection. Results showed that current BEIs may not protect the majority or all of the workers in an occupational setting. For instance, current end-expired air indices for benzene and methyl chloroform protect 95% and less than 10% of the worker population, respectively. Urinary metabolite concentrations for benzene, methyl chloroform, and trichloroethylene were also estimated. The current BEI recommendation for phenol metabolite concentration at the end-of-shift sampling interval was estimated to protect 68% of the worker population, while trichloroacetic acid (TCAA) and trichloroethanol (TCOH) concentrations for methyl chloroform exposure were estimated to protect 54% and 97%, respectively. The recommended concentration of TCAA in urine as a determinant of trichloroethylene exposure protects an estimated 84% of the workers. Although many of the existing BEIs considered appear to protect a majority of the worker population, an inconsistent proportion of the population is protected. The information presented in this study may provide a new approach for administrative decisions establishing BEIs and allow uniform application of biological monitoring among different chemicals.

Abstract  Iron oxide-immobilized manganese oxide (MnO2) composite was prepared and the reactivity of persulfate (PS) with the composite as activator was investigated for degradation of carbon tetrachloride and benzene at various pH levels. Brunauer-Emmett-Teller (BET) surface area of the composite was similar to that of pure MnO2 while the pore volume and diameter of composite was larger than those of MnO2. Scanning electron microscopy couples with energy dispersive spectroscopy (SEM-EDS) showed that Fe and Mn were detected on the surface of the composite, and X-ray diffraction (XRD) analysis indicated the possibilities of the existence of various iron oxides on the composite surface. Furthermore, the analyses of X-ray photoelectron (XPS) spectra revealed that the oxidation state of iron was identified as 1.74. In PS/composite system, the same pH for the highest degradation rates of both carbon tetrachloride and benzene were observed and the value of pH was 9. Scavenger test was suggested that both oxidants (i.e. hydroxyl radical, sulfate radical) and reductant (i.e. superoxide anion) were effectively produced when PS was activated with the iron-immobilized MnO2.

Abstract  We investigated the dielectric and depolarized Rayleigh scattering behaviors of nitrobenzene (NO2-Bz), which is a benzene mono-substituted with a planar molecular frame bearing the large electric dipole moment 4.0 D, in non-polar solvents solutions, such as tetrachloromethane and benzene, at up to 3 THz for the dielectric measurements and 8 THz for the scattering experiments at 20 degrees C. The dielectric relaxation strength of the system was substantially smaller than the proportionality to the concentration in a concentrated regime and showed a Kirkwood correlation factor markedly lower than unity; g(K) similar to 0.65. This observation revealed that NO2-Bz has a tendency to form dimers, (NO2-Bz)(2), in anti-parallel configurations for the dipole moment with increasing concentration of the two solvents. Both the dielectric and scattering data exhibited fast and slow Debye-type relaxation modes with the characteristic time constants similar to 7 and similar to 50 ps in a concentrated regime (similar to 15 and similar to 30 ps in a dilute regime), respectively. The fast mode was simply attributed to the rotational motion of the (monomeric) NO2-Bz. However, the magnitude of the slow mode was proportional to the square of the concentration in the dilute regime; thus, the mode was assigned to the anti-parallel dimer, (NO2-Bz)(2), dissociation process, and the slow relaxation time was attributed to the anti-parallel dimer lifetime. The concentration dependencies of both the dielectric and scattering data show that the NO2-Bz molecular processes are controlled through a chemical equilibrium between monomers and anti-parallel dimers, 2NO(2)-Bz. (NO2-Bz)(2), due to a strong dipole-dipole interaction between nitro groups. (C) 2014 Author(s).

Abstract  The emission of volatile organic compounds (VOCs) from wastewater treatment plants (WWTPs) is becoming an environmental issue of increasing concern. As biological treatment has been considered as one important approach for VOC removal, lab-scale batch experiments were conducted in this study to investigate the fates of four chlorinated hydrocarbons, including chloroform, carbon tetrachloride, trichloroethylene (TCE), and tetrachloroethylene (PERC), in the biological treatment processes with respect to the effects of aeration and sludge addition. The VOC concentrations in the phases of air, water, and sludge under four simulated treatment stages (the first sedimentation, the forepart and rear part of aerobic biological treatment, and the second sedimentation) were analyzed. The results were used to understand the three-phase partitioning of these compounds and to estimate their potentials for volatilization and biological sorption and degradation in these technologies with the concept of fugacity. It was observed that the VOCs were mainly present in the water phase through the experiments. The effects of aeration or sludge addition on the fates of these VOCs occurred but appeared to be relatively limited. The concentration distributions of the VOCs were well below the reported partitioning coefficients. It was suggested that these compounds were unsaturated in the air and sludge phases, enhancing their potentials for volatilization and biological sorption/degradation through the processes. However, the properties of these chlorinated VOCs such as the volatility, polarity, or even biodegradability caused by their structural characteristics (e.g., the number of chlorine, saturated or unsaturated) may represent more significant factors for their fates in the aerobic biological treatment processes. These findings prove the complication behind the current knowledge of VOC pollutions in WWTPs and are of help to manage the adverse impacts on the environment and public health by the VOCs from these particular sources.

Abstract  In this study, persulfate (PS) activated by the citric acid (CA)-chelated-ferrous ion (Fe(II)) to stimulate the oxidation of trichloroethylene (TCE) in groundwater remediation was investigated. The experimental results showed that TCE can be completely degraded over 60 min with a PS/Fe(II)/CA/TCE molar ratio of 15:2:1:1, demonstrating the effectiveness of Fe(II)-CA activated PS oxidation on TCE degradation. The probe compound tests clearly identified the generation and intensity of the reactive oxygen species in PS/Fe(II)/CA system, namely sulfate radicals (center dot SO4-), hydroxyl radicals (center dot OH) and superoxide radical anions (O-2(-center dot)). Moreover, the free radical quenching studies further indicated the generation of these reactive oxygen species and OH is the predominant one in Fe(II)-CA-activated PS system. The TCE degradation rate decreased as the Cl-, HCO3- anions and HA increased over the tested range of ion strengths, owing to their significant scavenging function to center dot OH and center dot SO4- radicals. Briefly, Fe(II)-CA activated PS oxidation is a highly promising technique for remediation of the contaminated sites containing TCE, but more complex constituents existed in in-situ groundwater should be carefully considered for its practical application. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  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.

Abstract  Iron oxide-magnetite (Fe3O4) as a heterogeneous activator to activate persulphate anions [Formula: see text] for trichloroethylene (TCE) degradation was investigated in this study. The experimental results showed that TCE could be completely oxidized within 5 h by using 5 g L(-1) magnetite and 63 mM [Formula: see text] indicating the effectiveness of the process for TCE removal. Various factors of the process, including. [Formula: see text] and magnetite dosages, and initial solution pH, were evaluated, and TCE degradation fitted well to the pseudo-first-order kinetic model. The calculated kinetic rate constant was increased with increasing [Formula: see text] and magnetite dosages, but it was independent of solution pH. In addition, the changes of magnetite morphology examined by scanning electron microscopy and X-ray powder diffraction, respectively, confirmed the slight corrosion with α-Fe2O3 coated on the magnetite surface. The probe compounds tests clearly identified the generation of the reactive oxygen species in the system. While the free radical quenching studies further demonstrated that [Formula: see text] and •OH were the major radicals responsible for TCE degradation, whereas [Formula: see text] contributed less in the system, and therefore the roles of reactive oxygen species on TCE degradation mechanisms were proposed accordingly. To our best knowledge, this is the first time the performance and mechanism of magnetite-activated persulphate oxidation for TCE degradation are reported. The findings of this study provided a new insight into the heterogeneous catalysis mechanism and showed a great potential for the practical application of this technique in in situ TCE-contaminated groundwater remediation.

Abstract  LaMnO3+delta which is an environment-friendly and inexpensive material has been previously used as catalyst in Post-Plasma Catalysis (PPC) in the total oxidation of trichloroethylene (TCE) which is a solvent widely used in dry cleaning and degreasing processes. It has been shown that the process efficiency increases in moist air (RH = 18%).The issue we want to address herein is the effect of water on the location of chlorine at the surface of the catalyst as chlorine is able to alter the catalyst structure, activity and stability. Therefore, a combined Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) study has been carried out on the fresh LaMnO3+delta catalyst (LM) and used catalysts after performing PPC with TCE diluted in dry synthetic air (LMO) or with industrial air containing water (LM18; 18 stands for the Relative Humidity) and CO2 (about 560 ppmv) at a temperature of 150 C. XPS and ToF-SIMS results both show the presence of chlorine on the tested catalysts whose amount increases by exposure of the catalyst to the reactive mixture in dry synthetic air. XPS results reveal that chlorine is present as both chloride ion and covalent chlorine on LMO while organic chlorinated residues are absent on LM18 catalyst. ToF-SIMS study indicates that lanthanum excess as oxide(hydroxide) partially covering the perovskite mainly transforms into LaOCl and to a minor extent into LaCl3. Extent of Mn chlorination seems to be favored over LMO having a higher MnClx +/-/MnOCl +/- ionic ratio compared to LM18. Furthermore ToF-SIMS clearly identifies Cl chlorinated organic ions, mainly CH2Cl- and CHCl2-, on LMO which may contribute to the XPS Cl organic component. From the combined ToF-SIMS and XPS results it is found that water delays the surface degradation extent of the perovskite into related (oxy)(hydroxy)chlorinated inorganic phases by less molecular chlorine and related chlorine species on the catalyst surface. A reaction scheme of Cl removal over LaMnO3+delta emphasing the role of water is given taking into account the detection of ToF-SIMS ions representative of the successive Mn intermediate states. As a consequence water allows tuning the degradation pathways of the main intermediate of the reaction, dichloroacetyl chloride (DCAC), which decomposes to give phosgene, HCCl3 and CCl4 by a successive Cl incorporation over (oxy)(hydroxy)chorinated perovskite or/and Mn species while COx species are likely formed over the perovskite. (C) 2014 Elsevier B.V. All rights reserved.