Abstract  Experimental data obtained in vivo with the closed-chamber gas uptake technique have been reported for a series of volatile chemicals. Pharmacokinetic analyses of these data have been performed either by using a two-compartment model or physiological models. In the former the transfer rate of chemical from ambient air to body is defined by the clearance of uptake. In the latter models the transfer rate depends on alveolar ventilation, cardiac output, and blood: air partition coefficient. In this communication we describe the quantitative relationship between clearance of uptake and alveolar ventilation, cardiac output, and blood: air partition coefficient. Theoretical values of clearance of uptake were calculated for a variety of volatile chemicals using literature data on alveolar ventilation, cardiac output, and blood: air partition coefficient. For most chemicals the experimentally determined values in rats and mice were about 60% of the theoretical values. This suggests that the inhalatory uptake rate of chemical may be overestimated if literature values of alveolar ventilation are used in physiological pharmacokinetic models for rodents.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. The objective of this research was to identify chemical, physical, bacteriological, and viral contaminants, and their sources, which present the greatest health threat in public ground water supplies in the USA; and to classify (prioritize) such contaminants and relative to their health concerns. The developed contaminant prioritization methodology was based on frequency of occurrence and adverse health effects. Adverse health effects were based on carcinogenic potency, toxicity, hazardous chemical priorities and drinking water standards. Application of the methodology for wellhead protection areas, (WHPAs) revealed that approximately 200 different contaminants have been detected in the nation's public ground water supplies. The seven chemical constituents with the highest priority were arsenic, chromium, cadmium, carbon tetrachloride, chloroform, 1, 1-dichloroethylene, and ethylene dibromide. Other contaminants of concern were trichloroethylene, nitrates, barium, 1,1,

Abstract  OBJECTIVES: The exposure of seven workers and three on-site study examiners to N-methyl-2-pyrrolidone (NMP) was studied in an adhesive bonding compound and glue production facility.

METHODS: Airborne NMP was analysed by personal and stationary sampling on activated charcoal tubes. NMP and its main metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI), were analysed in pre-shift and post-shift spot urine samples by gas chromatography-mass spectrometry. The workers were examined with respect to irritation of the eyes, the mucous membranes and the skin, and health complaints before and after the work-shift were recorded.

RESULTS: The time-weighted average concentration of NMP in most work areas varied between 0.2 and 3.0 mg/m3. During the manual cleaning of stirring vessels, valves and tools, 8-h TWA exposures of up to 15.5 mg/m3 and single peak exposures of up to 85 mg/m3) were observed. NMP and its metabolites were detected in two pre-shift urine specimens. NMP and 5-HNMP concentrations in post-shift urine samples of five workers and three on-site study examiners were below 125 microg/g creatinine and 15 mg/g creatinine, respectively, while two vessel-cleaning workers showed significantly higher urinary NMP concentrations of 472 and 711 microg/g creatinine and 5-HNMP concentrations of 33.5 and 124 mg/g creatinine. 2-HMSI was detectable in four post-shift samples (range: 1.6-14.7 mg/g creatinine). The vessel cleaner with the highest NMP exposure reported irritation of the eyes, the upper respiratory tract and headaches.

CONCLUSIONS: The results of this study indicate a relatively low overall exposure to NMP in the facility. An increased uptake of NMP occurred only during extensive manual vessel cleaning. Health complaints associated with NMP exposure were recorded in one case and might be related to an excessive dermal exposure due to infrequent and inadequate use of personal protective equipment.

Abstract  Sixty laboratories of five different countries participated in a large-scale interlaboratory comparison test for the determination of halogenated hydrocarbons in water. Participants used their in-house method with 44 laboratories applying head space GC ECD analysis and 5 using liquid/liquid extraction. A set of two artificially produced samples was prepared; the halogenated hydrocarbons investigated were trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, trichloromethane, terrachloromethane, 1,1-dichloroethylene, dichloromethane, dibromochloromethane, bromodichloromethane, 1,2-dichloroethane and tribromomethane. The procedure of sample preparation, storage and distribution was monitored by an extensive quality assurance system including homogeneity tests, stability tests, and trend analysis of the submitted data. The analytical results submitted by the participants exhibited RSD values of up to 35% and outlier rates of up to 19%. The percentage of false positive and false negative results was at the highest 12% for selected substances. Recovery rates varying from 86% to 106% proved the correctness of the analytical results submitted by the participants and showed that the procedure developed in this study for sample preparation and distribution is well suited for the performance of large-scale interlaboratory comparison tests of halogenated hydrocarbons in water.

Abstract  Chlorine-containing organic compounds (Cl-VOC) require special attention due to their distinct toxicity, high stability and persistence in the environment. Removal of Cl-VOC by catalytic oxidation over a wide variety of catalysts has been presented in literature. This paper reviews the state of the art in this subject, including different model compounds, nature of catalysts, and oxidation activity. Catalyst selectivity (CO2 vs. CO and HCl vs. Cl-2), by-products formation and the causes of deactivation are also analyzed as the most important factors in the catalyst selection for practical applications.

Abstract  High concentrations of tetrachloroethylene were discovered in groundwater samples taken from the Honkala aquifer in the municipality of Sakyla in southwestern Finland. The contamination was traced to a dry-cleaning laundry located close to a tributary esker which is connected to the Sakylanharju esker in the northeastern part of the area. The Weichselian and Holocene sediments of the area include till, sand and gravel and also glacial and postglacial clay deposits. The groundwater flows west towards Pyhajarvi (a lake in the municipality of Sakyla). A study was launched to test the applicability of numerical groundwater models in developing an overview of groundwater flow and contaminant transport in the area and prediction of the timing of natural attenuation. Modelling was conducted with the MODFLOW, MODFLOWP and MT3D codes, the resulting simulations indicating a natural attenuation time of more than 30 years would be required for the aquifer. Active aquifer restoration would require pumping and treatment of the polluted groundwater.

Abstract  One-port surface acoustic wave (SAW) devices with defined reflector patterns give characteristic signal patterns in the time domain making them identifiable and leading to so-called RFID-Tags. Each sensor responds with a burst of signals, their timed positions giving the identification code, while the amplitudes can be related to the analyte concentration. This paper presents the first combination of such a transducer with chemically sensitive layer materials. These include crosslinked polyvinyl alcohol for determining relative humidity and tert-butylcalix[4]arene for detecting solvent vapors coated on the free space between the reflectors. In going from the time domain to the frequency domain by Fourier transformation, changes in frequency and phase lead to sensor responses. Hence, it is possible to measure the concentration of tetrachloroethene in air down to 50 ppm, as well as 1% changes in relative humidity.

Abstract  Excitation into either the metal-to-ligand charge-transfer, MLCT, band or the ligand field, LF, band of W(CO)(4)(phen) promoted an electron transfer to paraquat, PQ(2+). This process was observed spectroscopically by the appearance of the characteristic bands of the well-known radical cation PQ(*)(+). Both nanosecond and picosecond flash photolysis were used to further examine the electron-transfer reaction. Excitation of W(CO)(4)(phen) in the presence of 10 mM PQ(2+) using a 355 nm, 30 ps pulse revealed the formation of PQ(*)(+) within the pulse. This suggests the rate of electron transfer is above diffusion control and that either there must be some preassociation between the reactants prior to excitation or the reaction is mediated by formation of a solvent radical (in a "hot" electron transfer(?)). A 355 nm, 10 ns pulse was also used to excite W(CO)(4)(phen) in the presence of 10 mM PQ(2+). Again, PQ(*)(+) was formed promptly and persisted for times on the order of microseconds. Subsequently, competition between back electron transfer (tau = 17 &mgr;s) and net reaction was observed. The possibility of electron transfer to "inert" halocarbons was also investigated. Picosecond and nanosecond flash photolysis of W(CO)(4)(phen) using both 355 and 532 nm excitation in a halogenated solvent, C(2)Cl(4), yielded a spectrum indicative of the prompt formation (<30 ps) of reduced C(2)Cl(4). Available estimates of potentials require this to arise from a hot (not vibrationally relaxed) electron transfer.

Abstract  [1] Difficulties associated with identifying the dense nonaqueous phase liquid (DNAPL) source zone architecture at the field scale, combined with the computational costs of field-scale DNAPL dissolution simulations, have motivated the development of a number of simplified models that rely upon upscaled (i.e., domain-averaged) mass transfer coefficients to approximate field-scale dissolution processes. While conceptually attractive, these upscaled models have yet to be fully evaluated for prediction of mass recovery from a range of nonuniform, three-dimensional DNAPL source zones. This study compares upscaled model predictions of flux-weighted downstream concentrations and source longevity to predictions derived from three-dimensional multiphase numerical simulation of tetrachloroethene (PCE)-NAPL dissolution for realizations of a statistically homogeneous, nonuniform aquifer. Although the functional forms of the upscaled models are generally shown to be mathematically equivalent, upscaled model flux-weighted concentration predictions varied by over one order of magnitude, with variations attributed to the dependence of the upscaled model parameters on the specific source zone scenario used for model calibration. Replacement of upscaled model calibration parameters with source zone parameters that can be obtained from site characterization information ( specifically, the initial flux-weighted concentration and source zone ganglia-to-pool (GTP) mass ratio) reduced the root-mean-square error between upscaled and numerical model predictions by approximately 80%. Application of this modified model to a range of source zone scenarios (0.4 < GTP < infinity) demonstrates the efficacy of the model for use as a screening tool to relate DNAPL mass removal and flux-weighted concentrations when mass removal is less than 80%.

Abstract  Remediation of source zones at sites contaminated with dense non-aqueous-phase liquids using aggressive in situ flushing technologies, such as the addition of chemical additives known as cosolvents, have been implemented and successfully demonstrated in recent field tests. However, treatment of the waste fluids generated from such cleanup technologies has not received much attention. The purpose of this laboratory research was to evaluate the feasibility of using sonication as a method for treating waste fluids produced during in situ alcohol flushing at a site contaminated with a dense non-aqueous-phase liquid. Experimental results showed that sonochemical destruction of perchloroethylene (PCE) followed pseudo first-order kinetics and that increasing ethanol cosolvent percentages in the aqueous effluent resulted in decreasing degradation rates of PCE in solution. The energy efficiency (G = degradation/energy input) of the sonication treatment also decreased as the ethanol volume fraction increased. Overall, sonication was seen to degrade PCE in aqueous solutions, becoming less effective as the cosolvent fraction increased.

Abstract  A simple, rapid and inexpensive procedure for extraction and analysis of volatile halocarbons in water samples was presented using the headspace single-drop microextraction (HS-SDME) technique and gas chromatography with microcell electron capture detector (GC-muECD). Operation parameters, such as extraction solvent, headspace volume, organic drop volume, salt concentration, temperature and sampling time, were studied and optimized. Extraction of 10 volatile halocarbon compounds was achieved using the optimized method. Calibration curves of 10 target compounds yielded good linearity in the respective range of concentration (R-2 greater than or equal to 0.9968, chlorodibromomethane in the concentration range of 0.05-50 mug/L). The limits of detection were found between 0.002 (tetrachloroethene) and 0.374 mug/L (1,1,2-trichloroethane), and relative standard deviations (RSD%) ranged between 4.3 (chloroform) and 9.7% (1,1,2,2-tetrachloroethane). Spiked recoveries of tap water and ground water agreed well with the known values between 118.97 (20.0 mug/L of 1,1,2-trichloroethane) and 82.61% (10.0 mug/L of tetrachloroethene), demonstrating that the HS-SDME combined GC-muECD was a useful and reliable technique for the rapid determination of volatile halocarbon compounds in water samples.

Abstract  The pulp and paper industry produces large quantities of organic and chlorinated organic wastes. Those compounds that are toxic and/or mutagenic, difficult to degrade, and have a propensity to bioaccumulate pose a serious human health hazard. Of prime concern are chlorophenols, chlorinated aliphatic hydrocarbons, and resin acids. Under anaerobic conditions, highly chlorinated aromatic and aliphatic compounds can be reductvely dechlorinated to lightly chlorinated compounds, or completely mineralized. In the aerobic environment, highly chlorinated compounds, such as pentachlorophenol, are slowly degraded, whereas tetrachloroethylene is inert. In contrast, mono- and dichlorinated compounds are rapidly degraded by aerobic microorganisms. Sequential anaerobic-aerobic biological treatment of pulp mill wastes holds the greatest promise for complete mineralization of hazardous chlorinated wastes. This biological treatment process also will degrade other components of pulp mill waste such as chlorinated dioxins and furans, chloroacetones, and the potent mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone. Methanogenic activity is sensitive to sulfur compounds, resin acids, and oxidants. Physical removal of these compounds or pretreatment prior to effluent entry into the anaerobic reactor will be required to ensure maximum anaerobic digestion. Resin acids can be degraded aerobically but not anaerobically. Resin acids should be removed from the effluent stream and collected as a tall-oil byproduct or degraded separately. The development of new pulping procedures, such as oxygen delignification, and the replacement or partial replacement of chlorine by chlorine dioxide or hydrogen peroxide for pulp bleaching can greatly reduce the emission of toxic chlorinated compounds. Decreased risks to human health and improved environmental quality will be achieved through the adoption of alternative pulping and bleaching methods coupled with effective anaerobic-aerobic treatment technologies.

Abstract  Three different flow regimes were carried out in a pilot-scale horizontal subsurface flow constructed wetland-treating sulfate rich wastewater contaminated with monochlorobenzene (MCB) and perchloroethene (PCE). The three regimes were continuous flow, 7-day cycle discontinuous flow, and 2.5-day cycle discontinuous flow. The results show that intensifying the tidal regime (2.5-day cycle) significantly enhanced MCB removal before 2 m from the inlet and increasing PCE removal efficiency at 0.5 m. The PCE dechlorination process was promoted with tidal operation, especially under the 2.5-day cycle regime, with significant increases of cis-1,2- dichloroethenes (DCEs), vinyl chloride (VC), and ethene, but trans-1,2-DCE was significantly decreased after tidal operation. Due to the high sulfate concentration in the influent, sulfide was observed in pore water up to 20 and 23 mg L(-1) under continuous flow and 7-day cycle regime, respectively. However, sulfide concentrations decreased to less than 4 mg L(-1) under intensified tidal operation (2.5-day cycle). The increase of oxygen concentration in pore water through intensified tidal operation resulted in better MCB removal performance and the successful inhibition of sulfate reduction. In conclusion, intensifying tidal operation is an effective approach for the treatment of chlorinated hydrocarbons and inhibiting sulfide accumulation in horizontal subsurface flow constructed wetland.

Abstract  Laboratory studies and model results were utilized to design packed tower and hollow fiber air stripping units which were field tested with a contaminant-laden surfactant stream. Field units were operated at a 1.9 liter/min liquid flow rate with air/liquid ratios ranging from 20 to 50 and system temperatures ranging from 10 to 37degreesC. Tri- and tetrachloroethylene were analyzed. as the target components. When properly operated, the field units successfully met or exceeded the targeted 90% removal efficiency. As expected, high air to liquid flow rates and higher system temperatures achieved high removal efficiencies while solutions with high surfactant and contaminant concentrations were the most difficult to treat.

Abstract  In this study we examined the relative importance of side reactions, i.e. the formation of volatile fatty acids (VFA), and the reduction of alternative electron acceptors (nitrate, sulfate, Fe(III)), in enhanced dechlorination microcosms, amended with different electron donors, namely lactate, butyrate, and H(2)+acetate mixture. Dechlorination reactions proceeded at low rates and consequently, nearly all of the reducing equivalents (over 99%) available from electron donor consumption were channeled to (side) reactions other than dechlorination. The relevance of these side reactions was more evident with lactate which was consumed at higher rate than other electron donors. Correspondingly, high levels of VFA and soluble Fe(II) accumulated in the supernatant of lactate-amended microcosms. Ecotoxicity experiments (Lepidium sativum germination tests) also indicated that the supernatant was much more toxic/inhibitory than that of other microcosms. Among the electron donors tested, the H(2)+acetate mixture, yielded the most promising results in terms of extent of dechlorination, negligible accumulation of by-products, and residual groundwater toxicity. Fluorescent In situ Hybridization analysis (FISH) confirmed that H(2)+acetate-amended microcosms were dominated by Dehalococcoides spp., while a higher biodiversity was observed in the cultures fed with lactate or butyrate. Overall, the average amount of donor that was required for the removal of 1micromol of chloride from the contaminant differed greatly among the donors, namely 2.13meq/micromolCl(-) for lactate, 1.01meq/micromolCl(-) for butyrate, and 0.39meq/micromolCl(-) for H(2)+acetate mixture. Interestingly, dechlorinating activity was observed under sulfate-reducing conditions; this suggests that it may not be necessary to deplete the sulfate from the groundwater, for instance by supplying an excess electron donor, in order to achieve substantial dechlorination. Finally, in this study we found that the pathway of anaerobic lactate degradation shifted from the production of acetate and H(2) during active sulfate reduction to acetate and propionate upon sulfate depletion. Energetic considerations that support this finding were presented.