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Dry cleaning facilities using perchloroethylene produce a solid waste consisting of spent filtering powders with a high content of residual perchloroethylene, together with dyes and non-volatile residues. Untreated spent powders, classified as hazardous waste, cannot be disposed in landfill and incineration represents the only viable alternative. In this study, together with a full characterisation of the waste, the removal and recovery of the residual perchloroethylene by means of different heat treatments was investigated. In particular, tests of distillation and stripping with air and steam were carried out, evaluating the effectiveness of the treatments by quantifying the residual perchloroethylene in the samples treated. The results obtained show that the spent filtering powders contained about 25% wt. of perchloroethylene and that the maximum perchloroethylene recovery was obtained by steam stripping; approximately 98% after only 50 minutes. However, this treatment accounted for the production of a liquid mixture containing perchloroethylene and of a solid waste that required a further washing with boiling water to decrease the residual organic content below the eligibility criteria for landfill disposal., (© The Author(s) 2015.)

We studied the spatial and temporal distribution patterns of Chlorinated Volatile Organic Compounds (CVOCs) in the karst aquifers in northern Puerto Rico (1982-2013). Seventeen CVOCs were widely detected across the study area, with the most detected and persistent contaminated CVOCs including trichloroethylene (TCE), tetrachloroethylene (PCE), carbon tetrachloride (CT), chloroform (TCM), and methylene chloride (DCM). Historically, 471 (76%) and 319 (52%) of the 615 sampling sites have CVOC concentrations above the detection limit and maximum contamination level (MCL), respectively. The spatiotemporal patterns of the CVOC concentrations showed two clusters of contaminated areas, one near the Superfund site "Upjohn" and another near "Vega Alta Public Supply Wells." Despite a decreasing trend in concentrations, there is a general northward movement and spreading of contaminants even beyond the extent of known sources of the Superfund and landfill sites. Our analyses suggest that, besides the source conditions, karst characteristics (high heterogeneity, complex hydraulic and biochemical environment) are linked to the long-term spatiotemporal patterns of CVOCs in groundwater., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this paper we describe the application of a needle trap microextraction device packed with graphene nanoplatelets for the sampling and analysis of perchloroethylene in dry cleaning. The study was carried out in two phases. First the parameters for the sampling and analysis of perchloroethylene by NTD were evaluated and optimized in the laboratory. Then the sampler was used to determine the levels of perchloroethylene in a dry-cleaning shop. In the laboratory phase of the study the performance of the NTD packed with the proposed sorbent was examined in a variety of sampling conditions to evaluate the technique. The technique was also compared with NTDs packed with PDMS as well as SPME with Carboxen/PDMS-coated fibers. Both the NTDs and SPME performed better at lower sampling temperatures and relative humidity levels. The post-sampling storage times for a 95% recovery of the analyte were 5, 5 and 3 days for NTD-graphene, NTD-PDMS and SPME-CAR/PDMS respectively. The optimum desorption time was 3 min for NTDs packed with either graphene or PDMS and 1 min for SPME-CAR/PDMS. The limits of detection for the GC/MS detection system were 0.023 and 0.25 ng mL(-1) for NTDs packed with graphene and PDMS and 0.014 ng mL(-1) for SPME coated with CAR/PDMS. In the second stage of the study the evaluated technique was applied to the sampling and analysis of perchloroethylene in dry cleaning. In this environment the performance of the NTD-graphene as a field sampler for PCE was similar to that of the SPME-CA/PDMS, and better than the NIOSH 1003 method which had greater measurement variations. The results show that a NTD packed with carbonic graphene nanoplatelets and used as an active exhaustive sampling technique is effective for determination of VOC and HVOC occupational/environmental pollutants in air., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Phytoscreening has been demonstrated at a variety of sites over the past 15 years as a low-impact, sustainable tool in delineation of shallow groundwater contaminated with chlorinated solvents. Collection of tree cores is rapid and straightforward, but low concentrations in tree tissues requires sensitive analytics. Solid-phase microextraction (SPME) is amenable to the complex matrix while allowing for solvent-less extraction. Accurate quantification requires the absence of competitive sorption, examined here both in laboratory experiments and through comprehensive examination of field data. Analysis of approximately 2,000 trees at numerous field sites also allowed testing of the tree genus and diameter effects on measured tree contaminant concentrations. Collectively, while these variables were found to significantly affect site-adjusted perchloroethylene (PCE) concentrations, the explanatory power of these effects was small (adjusted R(2) = 0.031). 90th quantile chemical concentrations in trees were significantly reduced by increasing Henry's constant and increasing hydrophobicity. Analysis of replicate tree core data showed no correlation between replicate relative standard deviation (RSD) and wood type or tree diameter, with an overall median RSD of 30%. Collectively, these findings indicate SPME is an appropriate technique for sampling and analyzing chlorinated solvents in wood and that phytoscreening is robust against changes in tree type and diameter.

The purpose of this article is the assessment of occupational exposure to perchloroethylene (PCE) and its clinical repercussions for dry-cleaning employees. The authors measured atmospheric levels of PCE and blood levels in a population of 50 exposed employees then conducted a study of clinical symptomatology in exposed and non-exposed subjects linked with this solvent. Fifty employees and 95 controls were studied. The median value of atmospheric PCE was 7 ppm (0.22-33), and the median blood level of PCE was 73.6 μg/l (11.8-144). These levels were correlated statistically to the action of sludge scraping and to the existence of automatic scrapers (p < 0.01). Eight percent of PCE blood levels were higher than the biological levels recently set in France. The exposed population did not show excessive signs of drowsiness nor of pre-narcotic syndrome or other symptoms studied. Dry-cleaning employees were exposed to PCE at atmospheric levels lower than the French and American chronic recommended exposure levels but some results were higher than recommended values. For PCE blood levels for the general working population, results were respectively lower than French and American national recommended levels in 92% and 94% cases. Risk should be considered, however, carefully in women of childbearing age, as 64% exceeded the recommended blood levels for pregnant women. This exposure did not generate any studied neurobehavioral symptomatology.

Background: Births during 1968-1985 at Camp Lejeune were exposed to drinking water contaminated with trichloroethylene (TCE), tetrachloroethylene (PCE), and benzene., Methods: We conducted a cross-sectional study to evaluate associations between residential prenatal exposure to contaminated drinking water at Camp Lejeune during 1968-1985 and preterm birth, small for gestational age (SGA), term low birth weight (TLBW), and mean birth weight (MBW) deficit. Birth certificates identified mothers residing at Camp Lejeune at delivery. We analyzed exposure data for the entire pregnancy and individual trimesters. For each period examined, births were categorized as unexposed if mothers did not reside at Camp Lejeune or if their residence on base received uncontaminated drinking water. Ground water contaminant fate/transport and distribution system models provided monthly estimated contaminant levels at residences. For PCE and TCE, the exposed group was divided into four levels: < median value, ≥ median value, ≥75th percentile, and ≥90th percentile. For benzene, the exposed group was categorized as <1 part per billion (ppb) versus ≥1 ppb because of sparse data. Magnitude of effect estimates and exposure response relationships were used to assess associations. Confidence intervals (CIs) indicated precision of estimates., Results: For the highest TCE exposure category during the entire pregnancy, odds ratios (ORs) were 1.5 (95% CI: 1.2, 1.9) and 1.3 (95% CI: 0.8, 2.2) for SGA and TLBW, respectively, and reduced MBW β = -78.3 g (95% CI: -115.0, -41.7). The OR =1.3 (95% CI: 1.0, 1.6) for preterm birth and the highest PCE exposure category during the entire pregnancy. Monotonic exposure-response relationships were observed for benzene exposure during the entire pregnancy and TLBW (highest category OR =1.5, 85% CI: 0.9, 2.3). Although a monotonic association between benzene and adjusted MBW difference was also observed (highest category β = -36.2 g, 95% CI: -72.3, -0.1), the association disappeared when TCE was also added to the model. We found no evidence suggesting any other associations between outcomes and exposures., Conclusion: Findings suggested associations between in utero exposures to TCE and SGA, TLBW and reduced MBW; benzene and TLBW; and PCE and preterm birth.

The hydrofluoroolefin 2,3,3,3-tetrafluoropropene (HFO-1234yf) has been introduced to replace 1,1,1,2-tetrafluoroethane (HFC-134a) as refrigerant in mobile, including vehicle, air conditioning systems because of its lower global warming potential. HFO-1234yf is volatile at ambient temperatures; however, high production volumes and widespread handling are expected to release this fluorocarbon into terrestrial and aquatic environments, including groundwater. Laboratory experiments explored HFO-1234yf degradation by (i) microbial processes under oxic and anoxic conditions, (ii) abiotic processes mediated by reactive mineral phases and zerovalent iron (Fe(0), ZVI), and (iii) cobalamin-catalyzed biomimetic transformation. These investigations demonstrated that HFO-1234yf was recalcitrant to microbial (co)metabolism and no transformation was observed in incubations with ZVI, makinawite (FeS), sulfate green rust (GR(SO4)), magnetite (Fe(3)O(4)), and manganese oxide (MnO2). Sequential reductive defluorination of HFO-1234yf to 3,3,3-trifluoropropene and 3,3-dichloropropene with concomitant stoichiometric release of fluoride occurred in incubations with reduced cobalamins (e.g., vitamin B12) indicating that biomolecules can transform HFO-1234yf at circumneutral pH and at ambient temperature. Taken together, these findings suggest that HFO-1234yf recalcitrance in aquifers should be expected; however, HFO-1234yf is not inert and a biomolecule may mediate reductive transformation in low redox environments, albeit at low rates.

The migration of volatile contaminants from groundwater and soil into indoor air is a potential health threat at thousands of contaminated sites across the country. This phenomenon, known as vapor intrusion, is characterized by spatial and temporal heterogeneity. This study examined short-term fluctuations in concentrations of tetrachloroethylene (PCE) in the indoor air of residential homes due to vapor intrusion in a community in San Antonio, Texas, that sits atop an extensive, shallow plume of contaminated groundwater. Using a community-based design, we removed potential indoor sources of PCE and then collected twelve 3-day passive indoor air samples in each of the 20 homes. Results demonstrated a one-order-of-magnitude variability in concentration across both space and time among the study homes, although all measured concentrations were below risk-based screening levels. We found that within any given home, indoor concentrations increase with the magnitude of the barometric pressure drop (P=0.048) and humidity (P<0.001), while concentrations decrease as wind speed increases (P<0.001) and also during winter (P=0.001). In a second analysis to examine sources of spatial variability, we found that indoor air PCE concentrations between homes increase with groundwater concentration (P=0.030) and a slab-on-grade (as compared with a crawl space) foundation (P=0.028), whereas concentrations decrease in homes without air conditioners (P=0.015). This study offers insights into the drivers of temporal and spatial variability in vapor intrusion that can inform decisions regarding monitoring and exposure assessment at affected sites.

Long-term monitoring (LTM) of groundwater remedial projects is costly and time-consuming, particularly when using phytoremediation, a long-term remedial approach. The use of trees as sensors of groundwater contamination (i.e., phytoscreening) has been widely described, although the use of trees to provide long-term monitoring of such plumes (phytomonitoring) has been more limited due to unexplained variability of contaminant concentrations in trees. To assess this variability, we developed an in planta sampling method to obtain high-frequency measurements of chlorinated ethenes in oak (Quercus rubra) and baldcypress (Taxodium distichum) trees growing above a contaminated plume during a 4-year trial. The data set revealed that contaminant concentrations increased rapidly with transpiration in the spring and decreased in the fall, resulting in perchloroethene (PCE) and trichloroethene (TCE) sapwood concentrations an order of magnitude higher in late summer as compared to winter. Heartwood PCE and TCE concentrations were more buffered against seasonal effects. Rainfall events caused negligible dilution of contaminant concentrations in trees after precipitation events. Modeling evapotranspiration potential from meteorological data and comparing the modeled uptake and transport with the 4 years of high frequency data provides a foundation to advance the implementation of phytomonitoring and improved understanding of plant contaminant interactions.

Meconium is the earliest stool of newborns, and is a complex matrix that reflects the degree of exposure of the fetus to xenobiotics. To investigate fetal exposure to volatile organic compounds, an analytical method was developed to identify and quantify BTEX (benzene, toluene, ethylbenzene, and o,m,p-xylene) and two chlorinated solvents (trichloroethylene and tetrachloroethylene) in meconium. Headspace-solid-phase microextraction coupled with gas chromatography-mass spectrometry was selected because it is simple, sensitive, can be automated, and requires no extensive sample preparation. Several extraction variables were optimized (fiber type, incubation time, temperature of fiber, and use of salt). Because meconium is a complex matrix, quantification by SPME was considered carefully because of potential interference, for example competitive adsorption. Calibration in water was compared with calibration in meconium using external and internal methods (with isotope-labeled compounds). In meconium, limits of quantification were determined to be in the range 0.064-0.096 ng g(-1) for the investigated compounds. All target compounds were determined in "real-case" meconium samples.

Contaminant concentrations in trees have been used to delineate groundwater contaminant plumes (i.e., phytoscreening); however, variability in tree composition hinders accurate measurement of contaminant concentrations in planta, particularly for long-term monitoring. This study investigated in planta passive sampling devices (PSDs), termed solid phase samplers (SPSs) to be used as a surrogate tree core. Characteristics studied for five materials included material-air partitioning coefficients (Kma) for chlorinated solvents, sampler equilibration time and field suitability. The materials investigated were polydimethylsiloxane (PDMS), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyoxymethylene (POM) and plasticized polyvinyl chloride (PVC). Both PDMS and LLDPE samplers demonstrated high partitioning coefficients and diffusivities and were further tested in greenhouse experiments and field trials. While most of the materials could be used for passive sampling, the PDMS SPSs performed best as an in planta sampler. Such a sampler was able to accurately measure trichloroethylene (TCE) and tetrachloroethylene (PCE) concentrations while simultaneously incorporating simple operation and minimal impact to the surrounding property and environment., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The long-term buffering potential of three silicate minerals (diopside, fayalite and forsterite) present as fine particles in porous quartz sand medium was evaluated in flow-through column experiments over a period of 6.5 months. The columns were operated with PCE concentrations close to saturation and inoculated with the organohalide-respiring consortium SDC-9™, which is able to completely dechlorinate PCE to ethene at high concentrations. In the absence of pH buffering agents, fermentation and organohalide respiration drove the pH close to 6.1, leading to severe inhibition of PCE dechlorination. Forsterite and fayalite were able to maintain the pH close to 7.5 and 6.5, respectively, and to sustain the production of VC and ethene. Diopside gradually lost its buffering capacity during the first 84 days due to the formation of a low reactive leached layer but dechlorination to cis-DCE was still achieved. Among the three minerals tested, forsterite was identified as the best buffering agent. Its presence led to the best PCE removal performance and the highest relative abundance of Dehalococcoides. This study showed that forsterite and fayalite are promising sources of long-term pH buffering for in situ bioremediation of source-zone PCE., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The use of compound specific multi-isotope approach (C and Cl) in the characterization of a chlorinated ethenes contaminated fractured aquifer allows the identification of several sources and contaminant plumes, as well as the occurrence of biodegradation and mixing processes. The study site is located in Spain with contamination resulting in groundwater concentrations of up to 50mg/L of trichloroethene (TCE), the most abundant chlorinated ethene, and 7 mg/L of tetrachloroethene (PCE). The potential sources of contamination including abandoned barrels, an underground tank, and a disposal lagoon, showed a wide range in δ(13)C values from -15.6 to -40.5‰ for TCE and from -18.5 to -32.4‰ for PCE, allowing the use of isotope fingerprinting for tracing of the origin and migration of these contaminants in the aquifer. In contrast, there is no difference between the δ(37)Cl values for TCE in the contaminant sources, ranging from +0.53 to +0.66‰. Variations of δ(37)Cl and δ(13)C in the different contaminant plumes were used to investigate the role of biodegradation in groundwater. Moreover, the isotopic data were incorporated into a reactive transport model for determination of whether the isotope pattern observed downstream from the tank's source could be explained by the simultaneous effect of mixing and biodegradation. The results demonstrate that a multi-isotope approach is a valuable tool for characterization of complex sites such as fractured bedrock aquifer contaminated by multiple sources, providing important information which can be used by consultants and site managers to prioritize and design more successful remediation strategies., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Widespread contamination of groundwater by chlorinated ethenes and their biological dechlorination products necessitates the reliable monitoring of liquid matrices; current methods approved by the U.S. Environmental Protection Agency (EPA) require a minimum of 5 mL of sample volume and cannot simultaneously detect all transformative products. This paper reports on the simultaneous detection of six chlorinated ethenes and ethene itself, using a liquid sample volume of 1 mL by concentrating the compounds onto an 85-µm carboxen-polydimenthylsiloxane solid-phase microextraction fiber in 5 min and subsequent chromatographic analysis in 9.15 min. Linear increases in signal response were obtained over three orders of magnitude (∼0.05 to ∼50 µM) for simultaneous analysis with coefficient of determination (R(2)) values of ≥ 0.99. The detection limits of the method (1.3-6 µg/L) were at or below the maximum contaminant levels specified by the EPA. Matrix spike studies with groundwater and mineral medium showed recovery rates between 79-108%. The utility of the method was demonstrated in lab-scale sediment flow-through columns assessing the bioremediation potential of chlorinated ethene-contaminated groundwater. Owing to its low sample volume requirements, good sensitivity and broad target analyte range, the method is suitable for routine compliance monitoring and is particularly attractive for interpreting the bench-scale feasibility studies that are commonly performed during the remedial design stage of groundwater cleanup projects.

In situ treatment of dense nonaqueous phase liquids (DNAPL) by enhanced reductive dechlorination (ERD) can be limited by contaminant toxicity, low pH, and challenges in effectively delivering electron donor. Flushing emulsified vegetable oil (EVO), colloidal Mg(OH)2 buffer, and a bioaugmentation culture (BC) through a zone containing neat tetrachloroethene (PCE) was effective in reducing contaminant toxicity, limiting pH declines, and accelerating bioenhanced dissolution of the DNAPL. In the effluent of porous media columns with little fine material, PCE concentrations reached a maximum of 40-50 times PCE aqueous solubility in water, demonstrating NAPL PCE was distributed throughout the 1.5 m column length. In a column treated with only EVO+BC, reductive dechlorination was limited. However, a single injection of EVO+Mg(OH)2+BC was effective in reducing PCE to below detection for over 400 days with a large increase in Cl(-) and dichloroethene (DCE), accelerating bioenhanced DNAPL dissolution. Dechlorination rates gradually increased over time with the rate of total ethene (TE) release from the Mg(OH)2+EVO+BC column reaching 5-6 times the TE release rate from the EVO+BC column. The accelerated dechlorination was likely due to both Mg(OH)2 addition which limited pH declines from HCl, volatile fatty acids (VFAs), and inorganic carbon (IC) production, and formation of a mixed PCE-vegetable oil NAPL which provided a readily accessible electron donor, resulting in rapid PCE degradation with reduced PCE toxicity.

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

Chlorinated-solvent compounds are among the most common groundwater contaminants in the United States. A majority of the many sites contaminated by chlorinated-solvent compounds are located in metropolitan areas, and most such areas have one or more chlorinated-solvent contaminated sites. Thus, contamination of groundwater by chlorinated-solvent compounds may pose a potential risk to the sustainability of potable water supplies for many metropolitan areas. The impact of chlorinated-solvent sites on metropolitan water resources was assessed for Tucson, Arizona, by comparing the aggregate volume of extracted groundwater for all pump-and-treat systems associated with contaminated sites in the region to the total regional groundwater withdrawal. The analysis revealed that the aggregate volume of groundwater withdrawn for the pump-and-treat systems operating in Tucson, all of which are located at chlorinated-solvent contaminated sites, was 20% of the total groundwater withdrawal in the city for the study period. The treated groundwater was used primarily for direct delivery to local water supply systems or for reinjection as part of the pump-and-treat system. The volume of the treated groundwater used for potable water represented approximately 13% of the total potable water supply sourced from groundwater, and approximately 6% of the total potable water supply. This case study illustrates the significant impact chlorinated-solvent contaminated sites can have on groundwater resources and regional potable water supplies., (© 2013, National Ground Water Association.)

This study comprises the first application of the Passive Flux Meter (PFM) for the measurement of chlorinated aliphatic hydrocarbon (CAH) mass fluxes and Darcy water fluxes in groundwater at a European field site. The PFM was originally developed and applied to measurements near source zones. The focus of the PFM is extended from near source to plume zones. For this purpose, 48 PFMs of 1.4 m length were constructed and installed in eight different monitoring wells in the source and plume zone of a CAH-contaminated field site located in France. The PFMs were retrieved, sampled, and analyzed after 3 to 11 weeks of exposure time, depending on the expected contaminant flux. PFM evaluation criteria include analytical, technical, and practical aspects as well as conditions and applicability. PFM flux data were compared with so-called traditional soil and groundwater concentration data obtained using active sampling methods. The PFMs deliver reasonable results for source as well as plume zones. The limiting factor in the PFM applicability is the exposure time together with the groundwater flux. Measured groundwater velocities at the field site range from 2 to 41 cm/day. Measured contaminant flux data raise up to 13 g/m(2)/day for perchloroethylene in the plume zone. Calculated PFM flux averaged concentration data and traditional concentration data were of similar magnitude for most wells. However, both datasets need to be compared with reservation because of the different sampling nature and time. Two important issues are the PFM tracer loss during installation/extraction and the deviation of the groundwater flow field when passing the monitoring well and PFM. The demonstration of the PFM at a CAH-contaminated field site in Europe confirmed the efficiency of the flux measurement technique for source as well as plume zones. The PFM can be applied without concerns in monitoring wells with European standards. The acquired flux data are of great value for the purpose of site characterization and mass discharge modeling, and can be used in combination with traditional soil and groundwater sampling methods.

Halocarbons including chloroform (CHCl3), trichloroethylene (C2HCl3), tetrachloroethylene (C2Cl4), chlorodibromomethane (CHBr2Cl) and bromoform (CHBr3) were measured in the Yellow Sea (YS) and the East China Sea (ECS) during spring 2011. The influences of chlorophyll a, salinity and nutrients on the distributions of these gases were examined. Elevated levels of these gases in the coastal waters were attributed to anthropogenic inputs and biological release by phytoplankton. The vertical distributions of these gases in the water column were controlled by different source strengths and water masses. Using atmospheric concentrations measured in spring 2012 and seawater concentrations obtained from this study, the sea-to-air fluxes of these gases were estimated. Our results showed that the emissions of C2HCl3, C2Cl4, CHBr2Cl, and CHBr3 from the study area could account for 16.5%, 10.5%, 14.6%, and 3.5% of global oceanic emissions, respectively, indicating that the coastal shelf may contribute significantly to the global oceanic emissions of these gases., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Exposure to perchlorethylene, especially for dry cleaning workers and for people living near dry cleaning shops, could lead to several diseases and disorders. This study examines the value of solid-phase microextraction (SPME) for sampling perchlorethylene in the atmosphere of dry cleaning shops. Carboxen/polydimethylsiloxane (CAR/PDMS) in 0.5-cm retracted mode was selected. There were no significant differences between sampling rates at different temperatures (range of 20 to 30 °C) and air velocities (2 to 50 cm/s). On the opposite, relative humidity (RH) had a significant effect on sampling rates. Method reproducibility was realized in the laboratory and field conditions and was 6.2 % and 7 to 11 %, respectively. Repeatability was also determined as 8.9 %. Comparison of the results according to the American Industrial Hygiene Association exposure assessment strategy showed the SPME sampler yields more conservative results in comparison with traditional standard method.

Abstract: 1,2-dichloroethane and tetrachlorethylene were studied in four different unsaturated porous media to determine the impact of the properties of media and fluids on the infiltration aided by digital image analysis technique. The results indicated that the whole process of NAPLs migration can be recorded dynamically using the digital image analysis technique. The unstable flow "fingering" occurred in the process of infiltration. Fingering mechanisms such as splitting, coalescing, and shielding were observed in the process of fingering. Front morphology of the infiltration was influenced by the properties of porous media and fluids. The vertical migration rates and the growth rates of area development were positively correlated to the size of medium particle and the density of the NAPLs (except for toluene) in the process of infiltrating. The number of fingers and the wavelength of fingering were also closely correlated with the properties of media and fluid. DNAPLs infiltrated faster compared with LNAPLs, which resulted in larger pollution area within the same infiltration time. It can be concluded that the environmental risk of DNAPLs is significantly greater than the LNAPLs.

Background: Recent studies suggest that occupational exposures such as noise and organic solvents may affect blood pressure. The aim of this study was to investigate interaction of noise and mixed organic solvents on blood pressure., Methods: Four hundred seventy-one workers of a car manufacturing plant were divided into four groups: group one or G1 workers exposed to noise and mixed organic solvents in the permitted limit or control group, G3 exposed to noise only, G2 exposed to solvents only, and G4 workers exposed to noise and mixed organic solvents at higher than the permitted limit or co-exposure group. Biological interaction of two variables on hypertension was calculated using the synergistic index., Results: The workers of co-exposure group (G4), noise only group (G3), and solvents only group (G2) had significantly higher mean values of SBP and DBP than workers of control group (G1) or office workers (P < 0.05). Also logistic regression analysis showed a significant association between hypertension and exposure to noise and mixture of organic solvents. Odds ratio for hypertension in the co-exposure group and the noise only and solvents only exposed groups was 14.22, 9.43, and 4.38, respectively, compared to control group. In this study, the estimated synergism index was 1.11., Conclusions: Our results indicate that exposure to noise or a mixture of organic solvents may be associated with the prevalence of hypertension in car manufacturing company workers and co-exposure to noise and a mixture of solvents has an additive effect in this regard. Therefore appropriate preventive programs in these workers recommended., (Copyright © 2012 Wiley Periodicals, Inc.)

The isotope evolution of tetrachloroethene (PCE) during its transport from groundwater toward the soil surface was investigated using laboratory studies and numerical modeling. During air-water partitioning, carbon and chlorine isotope ratios evolved in opposite directions, with a normal isotope effect for chlorine (ε = -0.20‰) and an inverse effect for carbon (ε = +0.46‰). During the migration of PCE from groundwater to the unsaturated zone in a 2D laboratory system, small shifts of carbon and chlorine isotope ratios (+0.8‰) were observed across the capillary fringe. Numerical modeling showed that these shifts are due to isotope fractionation associated with air-water partitioning and gas-phase diffusion. Carbon and chlorine isotope profiles were constant throughout the unsaturated zone once a steady state was reached. However, depending on the thickness of the unsaturated zone and its lithology, depletion in heavy isotopes may occur with distance during the transient migration of contaminants. Additionally, variations of up to +1.5‰ were observed in the unsaturated zone for chlorine isotopes during water table fluctuations. However, at steady state, it is possible to link a groundwater plume to gas-phase contamination and/or to differentiate sources of contamination based on isotope ratios.

Perchloroethylene (PCE) is the main solvent used in the dry cleaning industry worldwide. The aim of the present work was to evaluate the genotoxic potential of occupational exposure to PCE in dry cleaning workers. The study was carried out in 59 volunteers (30 workers, 29 controls). The genotoxic effect was evaluated by analyzing chromosome aberrations (CAs), and micronuclei (MN) and DNA damage (assessed by the comet assay) in peripheral blood lymphocytes. Environmental monitoring of exposure was carried out on personal breathing zone air samples collected during two consecutive working days by measuring the concentration of PCE air levels. The mean PCE concentration in workplace air of dry cleaning workers was 31.40 mg/m(3). There were no significant differences in CA frequency between dry cleaning workers and the controls, but analysis showed a significant association of CA frequency with employment duration and frequency of exposure to PCE. The MN frequency and DNA damage detected by alkaline comet assay were significantly increased in dry cleaning workers compared to the controls. The results suggest that (a) chronic occupational exposure to dry cleaning solvents below permissible occupational exposure limit of 70 mg/m(3) (i.e., ~10.3 ppm) may lead to an increased risk of genetic damage among dry cleaning workers, and (b) CA, MN tests, and comet assay are useful to monitor populations exposed to low doses of PCE.

The impact of co-solutes on sorption of tetrachloroethene (PCE) by two porous media with low organic-carbon contents was examined by conducting batch experiments. The two media (Borden and Eustis) have similar physical properties, but significantly different organic-carbon (OC) contents. Sorption of PCE was nonlinear for both media, and well-described by the Freundlich equation. For the Borden aquifer material (OC=0.03%), the isotherms measured with a suite of co-solutes present (1,2-dichlorobenzene, bromoform, carbon tetrachloride, and hexachloroethane) were identical to the isotherms measured for PCE alone. These results indicate that there was no measurable impact of the co-solutes on PCE sorption for this system. In contrast to the Borden results, there was a measurable reduction in sorption of PCE by the Eustis soil (OC=0.38%) in the presence of the co-solutes. The organic-carbon fractions of both media contain hard-carbon components, which have been associated with the manifestation of nonideal sorption phenomena. The disparity in results observed for the two media may relate to relative differences in the magnitude and geochemical nature of these hard-carbon components., (Copyright © 2012. Published by Elsevier Ltd.)

Chlorinated ethenes (CEs) are ubiquitous groundwater contaminants, yet there remains a need for a method to efficiently monitor their in situ degradation. We report here the first field application of combined stable carbon and chlorine isotope analysis of tetrachloroethene (PCE) and trichloroethene (TCE) to investigate their biodegradation in a heavily contaminated aquifer. The two-dimensional Compound Specific Isotope Analysis (2D-CSIA) approach was facilitated by a recently developed gas chromatography-quadrupole mass spectrometry (GCqMS) method for δ(37)Cl determination. Both C and Cl isotopes showed evidence of ongoing PCE transformation. Applying published C isotope enrichment factors (ε(C)) enabled evaluation of the extent of in situ PCE degradation (11-78%). We interpreted C and Cl isotopes using a numerical reactive transport model along a 60-m flow path. It revealed that combined PCE and TCE mass load was dechlorinated by less than 10%, and that cis-dichloroethene was not further dechlorinated. Furthermore, the 2D-CSIA approach allowed estimation of Cl isotope enrichment factors ε(Cl) (-7.8 to -0.8‰) and characteristic ε(Cl)/ε(C) values (0.42-1.12) for reductive PCE dechlorination at this field site. This investigation demonstrates the benefit of 2D-CSIA to assess in situ degradation of CEs and the applicability of Cl isotope fractionation to evaluate PCE and TCE dechlorination.

Background: Perchloroethylene (PCE) is the most widely used solvent in dry cleaning., Objectives: The aim was to evaluate PCE pollution and to identify the most reliable biological indicators for the assessment of workers' exposure., Methods: The study was performed in 40 dry cleaning shops covering a total of 71 subjects. Environmental monitoring was carried out with personal diffusive samplers (Radiello) for the entire work shift; biological monitoring was performed by measuring PCE in urine and blood and trichloroacetic acid (TCA) in urine on Thursday evening at end-of shift and on Friday morning pre-shift., Results: The mean concentration of PCE in air was 52.32 mg/m3, about 30% of the TLV-TWA and the mean value of the PCE inpre-shift blood samples was 0.304 mg/l, slightly more than 50% of the BEI. In dry cleaning shops employing less than 3 persons PCE in air exceeded the TLV-TWA in 7.8% of cases; the size of the shops was inversely related to pollution. Statistically significant correlations were found between PCE exposure and PCE in blood end-of-shift (r = 0.67) and pre-shift (r = 0.70), and PCE in urine end-of-shift (r = 0.68); no correlation was found between exposure and PCE in urine pre-shift and urinary TCA., Conclusions: Dry cleaning shops still register conditions of exposure and pollution by PCE, although to a lesser extent than in the past. The most reliable indicators for biological monitoring are CE in end-of-shift urine and PCE in blood both at end-of-shift and pre-shift at the end of the workweek.

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

A simple, fast and green direct analytical methodology has been developed to evaluate the concentration level of volatile organic compounds (VOCs) in indoor areas of vehicle repair shops using membrane devices as passive samplers. VOCs retained in the samplers were directly determined without any sample pre-treatment and avoiding the use of solvents by head space (HS) coupled to gas chromatography-mass spectrometry (GC-MS) in only 20 min. Benzene, toluene, tetrachloroethene, m,p-xylene and o-xylene were found at concentration levels from 0.1 to 11.2 mg m(-3)., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The reactivities of various types of iron mixtures to degrade chlorinated hydrocarbons (PCE, TCE and 1,1,1-TCA) in the form of non-aqueous phase liquids were investigated. The iron mixtures included a mixture of Fe(II) and Portland cement (Fe(II)-C), a mixture of Fe(II), Fe(III) and Ca(OH)(2) (Fe(II/III)-L), and a mixture of Fe(II), Fe(III), Ca(OH)(2), and Portland cement (Fe(II/III)-C). When the same amount of Fe(II) was used, Fe(II)-C was more reactive with chlorinated ethylenes (i.e. PCE and TCE) than Fe(II/III)-L. The reductive pathway for high concentrations of total PCE (i.e. above solubility) with Fe(II)-C was determined to be a combination of two-electron transfer, β-elimination and hydrogenolysis. Increasing the cement dose from 5% to 10% in Fe(II)-C did not affect PCE dechlorination rates, but it did favor the β-elimination pathway. In addition, when Fe(II/III)-C with 5%C was used, PCE dechlorination was similar to that by Fe(II)-C, but this mixture did not effectively degrade TCE. A modified second-order kinetic model was developed and shown to appropriately describe degradation of TCE at high concentrations. Fe(II/III)-L effectively degraded high concentrations of 1,1,1-TCA at rates that were similar to those obtained with Fe(II)-C using 10% C. Moreover, both increasing cement doses and the presence of Fe(III) increased dechlorination rates of 1,1,1-TCA, which was mainly through the hydrogenolysis pathway. The reactivity of Fe(II/III)-L was strongly dependent on the target compound (i.e. less reactivity with TCE, more with 1,1,1-TCA). Therefore, Fe(II/III)-L could be a potential mixture for degrading 1,1,1-TCA, but it should be modified to degrade TCE more effectively., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The permeable reactive barrier (PRB) remediation technology has proven to be more cost-effective than conventional pump-and-treat systems, and has demonstrated the ability to rapidly reduce the concentrations of specific chemicals of concern (COCs) by up to several orders of magnitude in some scenarios. This study derives new steady-state analytical solutions to multispecies reactive transport in a PRB-aquifer (dual domain) system. The advantage of the dual domain model is that it can account for the potential existence of natural degradation in the aquifer, when designing the required PRB thickness. The study focuses primarily on the steady-state analytical solutions of the tetrachloroethene (PCE) serial degradation pathway and secondly on the analytical solutions of the parallel degradation pathway. The solutions in this study can also be applied to other types of dual domain systems with distinct flow and transport properties. The steady-state analytical solutions are shown to be accurate and the numerical program RT3D is selected for comparison. The results of this study are novel in that the solutions provide improved modeling flexibility including: 1) every species can have unique first-order reaction rates and unique retardation factors, and 2) daughter species can be modeled with their individual input concentrations or solely as byproducts of the parent species. The steady-state analytical solutions exhibit a limitation that occurs when interspecies reaction rate factors equal each other, which result in undefined solutions. Excel spreadsheet programs were created to facilitate prompt application of the steady-state analytical solutions, for both the serial and parallel degradation pathways., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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

Geographic information systems (GIS) based techniques are cost-effective and efficient methods used by state agencies and epidemiology researchers for estimating concentration and exposure. However, budget limitations have made statewide assessments of contamination difficult, especially in groundwater media. Many studies have implemented address geocoding, land use regression, and geostatistics independently, but this is the first to examine the benefits of integrating these GIS techniques to address the need of statewide exposure assessments. A novel framework for concentration exposure is introduced that integrates address geocoding, land use regression (LUR), below detect data modeling, and Bayesian Maximum Entropy (BME). A LUR model was developed for tetrachloroethylene that accounts for point sources and flow direction. We then integrate the LUR model into the BME method as a mean trend while also modeling below detects data as a truncated Gaussian probability distribution function. We increase available PCE data 4.7 times from previously available databases through multistage geocoding. The LUR model shows significant influence of dry cleaners at short ranges. The integration of the LUR model as mean trend in BME results in a 7.5% decrease in cross validation mean square error compared to BME with a constant mean trend.

Investigation and numerical simulation, based on RT3D (reactive transport in 3-dimensions)were used to identify the source of tetrachloroethylene (PCE) and trichloroethylene (TCE) in the groundwater of a city in the north of China and reverse the input intensity. Multiple regressions were applied to analyze the influenced factors of input intensity of PCE and TCE using Stepwise function in Matlab. The results indicate that the factories and industries are the source of the PCE and TCE in groundwater. Natural attenuation was identified and the natural attenuation rates are 93.15%, 61.70% and 61.00% for PCE, and 70.05%, 73.66% and 63.66% for TCE in 173 days. The 4 source points identified by the simulation have released 0.910 6 kg PCE and 95.693 8 kg TCE during the simulation period. The regression analysis results indicate that local precipitation and the thickness of vadose zone are the main factors influencing organic solution transporting from surface to groundwater. The PCE and TCE concentration are found to be 0 and 5 mg x kg(-1) from surface to 35 cm in vadose zone. All above results suggest that PCE and TCE in groundwater are from the source in the surface. Natural attenuation occurred when PCE and TCE transporting from the surface to groundwater, and the rest was transported to groundwater through vadose zone. Local precipitation was one of the critical factors influencing the transportation of PCE and TCE to aquifer through sand, pebble and gravel of the Quaternary.

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

The reliability in measurement results obtained during environmental monitoring is crucial for the assessment and further planning of remediation efforts on the respective contaminated sites by the responsible authorities. A case study concerned with groundwater contaminated with perchloroethylene, trichloroethylene and 1,1,2-trichlorotrifluoroethane including their degradation products which involves private contract laboratories and an independent provider of quality assurance (QA) is presented. The experience gained with biannual monitoring campaigns over 14 years indicates that the selection of contractors on basis of accreditation status and successful performance in interlaboratory comparisons are not sufficient. Rather the auditing of the contractors by the QA provider prior to each campaign and the crosschecking of selected monitoring samples by the QA provider led to a lasting improvement of reliability in the contractors' measurement results. A mean deviation of 20% from the reference value determined by the QA provider for the crosschecked samples was reached.

Redevelopment of large contaminated brownfields (megasites) is often hampered by a lack of communication and harmonization among diverse stakeholders with potentially conflicting interests. Decision support is required to provide integrative yet transparent evaluation of often complex spatial information to stakeholders with different areas of expertise. It is considered crucial for successful redevelopment to identify a shared vision of how the respective contaminated site could be remediated and redeveloped. We describe a framework of assessment methods and models that analyzes and visualizes site- and land use-specific spatial information at the screening level, with the aim to support the derivation of recommendable land use layouts and to initiate further and more detailed planning. The framework integrates a GIS-based identification of areas to be remediated, an estimation of associated clean-up costs, a spatially explicit market value appraisal, and an assessment of the planned future land use's contribution to sustainable urban and regional development. Case study results show that derived options are potentially favorable in both a sustainability and an economic sense and that iterative re-planning is facilitated by the evaluation and visualization of economic, ecological and socio-economic aspects. The framework supports an efficient early judgment about whether and how abandoned land may be assigned a sustainable and marketable land use., (Copyright © 2011 Elsevier B.V. All rights reserved.)

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

An electronic nose principally composed of a photo ionization detector (PID) was developed for rapid detection of volatile chlorinated hydrocarbons (VCHs) in contaminated soil. Removal of interference gas such as benzene homologues with a pre-filtration tube was analyzed with gas chromatography (GC). A standard gas generator was applied to generate different concentrations of perchloroethylene (PCE) and trichloroethylene (TCE) gas, with which the determine precision and reproducibility of the electronic nose were evaluated by comparison with GC. Finally, simulated contamination soil with three typical paddy soils in Yangtze river delta region were used for ventilation purification experiments, the change of VCHs concentrations in the ventilation gas was monitored, based on which the applicability of the electronic nose was evaluated for on-line detection of the on-going of the ventilation purification process. Results showed that a halogenated hydrocarbon RAE-SEP tube was effective to remove interference gas, with 80%-97% of benzene homologues such as benzene and ethyl benzene being removed while more than 90% of VCHs passed through. With PCE or TCE gas, a linear dependence was derived between the data determined with the electronic nose and GC, the linear slope being 1.012 and R2 > 0.99. The electronic nose showed data consistent with GC (R2 > 0.99, n = 47) when applied for monitoring the remediation progress in a soil ventilation process. The electronic nose is therefore possibly applicable for rapid determination of soil pollution by VCHs, improving the efficiency of pollution diagnosis and remediation.

We have used a novel gas chromatography/mass spectrometry (GC/MS)-based approach to quantify perchloroethylene (PCE) residues in dry-cleaned fabrics. Residual PCE was extracted from fabric samples with methanol and concentration was calculated by the gas chromatographic peak area, standardized using PCE calibration data. Extracts examined were from samples of 100% wool, polyester, cotton, or silk, which were dry cleaned from one to six times in seven different Northern Virginia dry-cleaning establishments. Additional experiments were conducted to investigate the kinetics of PCE release in the extraction solvent and to the open air. We found that polyester, cotton, and wool retained ≥ µM levels of PCE, that these levels increased in successive dry-cleaning cycles, and that PCE is slowly volatilized from these fabrics under ambient room air conditions. We found that silk does not retain appreciable PCE. Measured differences across dry-cleaning establishments and fabric type suggest more vigorous monitoring of PCE residues may be warranted. Environ. Toxicol. Chem. 2011;30:2481-2487. © 2011 SETAC., (Copyright © 2011 SETAC.)

Compound-specific isotope analysis (CSIA) can potentially be used to relate vapor phase contamination by volatile organic compounds (VOCs) to their subsurface sources. This field and modeling study investigated how isotope ratios evolve during migration of gaseous chlorinated ethenes across a 18 m thick unsaturated zone of a sandy coastal plain aquifer. At the site, high concentrations of tetrachloroethene (PCE up to 380 μg/L), trichloroethene (TCE up to 31,600 μg/L), and cis-1,2-dichloroethene (cDCE up to 680 μg/L) were detected in groundwater. Chlorinated ethene concentrations were highest at the water table and steadily decreased upward toward the land surface and downward below the water table. Although isotopologues have different diffusion coefficients, constant carbon and chlorine isotope ratios were observed throughout the unsaturated zone, which corresponded to the isotope ratios measured at the water table. In the saturated zone, TCE became increasingly depleted along a concentration gradient, possibly due to isotope fractionation associated with aqueous phase diffusion. These results indicate that carbon and chlorine isotopes can be used to link vapor phase contamination to their source even if extensive migration of the vapors occurs. However, the numerical model revealed that constant isotope ratios are only expected for systems close to steady state.

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

A series of chitosan-stabilized Pd-NZVI (nano-zero-valent-iron) catalysts for dechlorination with variation in their composition and in the nature of the polymer has been prepared. The synthesis procedures and palladium and chitosan contents were optimized. It was demonstrated by the XPS method that Fe and Pd in Fe-Pd/chitosan samples exist in the metallic state. The positive shift of the binding energy as compared with the bulk metal shows that the iron metal in the surface layers exists as very small nanoparticles. The prepared materials were characterized also by the XAS method. The presence of O and N atoms in the first coordination shell of the central Fe atom in the Fe-Pd/chitosan samples certifies the binding of the Fe metal particles with the chitosan surface via OH and NH(2) groups. The samples are characterized by the high stability of the nanoparticles as compared to unstabilized Pd-NZVI. The materials were tested to evaluate their catalytic activity in the perchloroethene (PCE) dechlorination reaction. Some samples of chitosan-stabilized Pd-NZVI revealed a good performance in PCE degradation as compared to unstabilized Pd-NZVI., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

At buildings with potential for vapor intrusion of volatile organic chemicals (VOCs) from the subsurface, the ability to accurately distinguish between vapor intrusion and indoor sources of VOCs is needed to support accurate and efficient vapor intrusion investigations. We have developed a method for application of compound-specific stable isotope analysis (CSIA) for this purpose that uses an adsorbent sampler to obtain sufficient sample mass from the air for analysis. Application of this method to five residences near Hill Air Force Base in Utah indicates that subsurface and indoor sources of tricholorethene and tetrachloroethene often exhibit distinct carbon and chlorine isotope ratios. The differences in isotope ratios between indoor and subsurface sources can be used to identify the source of these chemicals when they are present in indoor air.

Compound-specific online chlorine isotope analysis of chlorinated hydrocarbons was evaluated and validated using gas chromatography coupled to a regular quadrupole mass spectrometer (GC-qMS). This technique avoids tedious off-line sample pretreatments, but requires mathematical data analysis to derive chlorine isotope ratios from mass spectra. We compared existing evaluation schemes to calculate chlorine isotope ratios with those that we modified or newly proposed. We also tested systematically important experimental procedures such as external vs. internal referencing schemes, and instrumental settings including split ratio, ionization energy, and dwell times. To this end, headspace samples of tetrachloroethene (PCE), trichloroethene (TCE), and cis-dichloroethene (cDCE) at aqueous concentrations in the range of 20-500 μg/L (amount on-column range: 3.2-115 pmol) were analyzed using GC-qMS. The results (³⁷Cl/³⁵Cl ratios) showed satisfying to good precisions with relative standard deviations (n = 5) between 0.4‰ and 2.1‰. However, we found that the achievable precision considerably varies depending on the applied data evaluation scheme, the instrumental settings, and the analyte. A systematic evaluation of these factors allowed us to optimize the GC-qMS technique to determine chlorine isotope ratios of chlorinated organic contaminants.

The sorption of chlorinated solvents and degradation products on seven natural clayey till samples from three contaminated sites was investigated by laboratory batch experiments in order to obtain reliable sorption coefficients (K(d) values). The sorption isotherms for all compounds were nearly linear, but fitted by Freundlich isotherms slightly better over the entire concentration range. For chloroethylenes, tetrachloroethylene (PCE) was most strongly sorbed to the clayey till samples (K(d)=0.84-2.45Lkg(-1)), followed by trichloroethylene (TCE, K(d)=0.62-0.96Lkg(-1)), cis-dichloroethylene (cis-DCE, K(d)=0.17-0.82Lkg(-1)) and vinyl chloride (VC, K(d)=0.12-0.36Lkg(-1)). For chloroethanes, 1,1,1-trichloroethane (1,1,1-TCA) was most strongly sorbed (K(d)=0.2-0.45Lkg(-1)), followed by 1,1-dichloroethane (1,1-DCA, K(d)=0.16-0.24Lkg(-1)) and chloroethane (CA, K(d)=0.12-0.18Lkg(-1)). This is consistent with the order of hydrophobicity of the compounds. The octanol-water coefficient (logK(ow)) correlated slightly better with logK(d) values than logK(oc) values indicating that the K(d) values may be independent of the actual organic carbon content (f(oc)). The estimated logK(oc) or logK(d) for chlorinated solvents and degradation products determined by regression of data in this study were significantly higher than values determined by previously published empirical relationships. The site specific K(d) values as well as the new empirical relationship compared well with calculations on water and soil core concentration for cis-DCE and VC from the Rugårdsvej site. In conclusion, this study with a wide range of chlorinated ethenes and ethanes--in line with previous studies on PCE and TCE--suggest that sorption in clayey tills could be higher than typically expected., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In order to determine whether natural attenuation of chlorinated ethenes by microbial activity occurs in aquitards, sediments at a site contaminated with tetrachloroethene were vertically studied by drilling. The distribution of microbes (Dehalococcoides group and anaerobic hydrogen producers) and the ability of the sediments to sustain microbial dechlorination were determined in an aquitard as well as in an aquifer. Close-spaced sampling revealed the existence of large populations of Dehalococcoides and H(2)-producing bacteria, especially in the organic-rich clayey aquitard rather than in the aquifer. The vinyl chloride reductase gene was also detected in the clay layer. Furthermore, incubation experiments indicated that the clay sediment could sustain transformations of tetrachloroethene at least to vinyl chloride. In contrast, no significant transformation was observed in the aquifer sand. Our results indicate that dechlorination of tetrachloroethene by bacteria can take place in an organic-rich clayey aquitard, and that organic-rich clay may also be important in the natural attenuation in an adjacent aquifer, possibly supplying a carbon source or an electron donor., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Microbial reductive dechlorination of trichloroethene (TCE) and perchloroethene (PCE) in the vicinity of their dense non-aqueous phase liquid (DNAPL) has been shown to accelerate DNAPL dissolution. A three-layer diffusion-cell was developed to quantify this bio-enhanced dissolution and to measure the conditions near the DNAPL interface. The 12 cm long diffusion-cell setup consists of a 5.5 cm central porous layer (sand), a lower 3.5 cm DNAPL layer and a top 3 cm water layer. The water layer is frequently refreshed to remove chloroethenes at the upper boundary of the porous layer, while the DNAPL layer maintains the saturated chloroethene concentration at the lower boundary. Two abiotic and two biotic diffusion-cells with TCE DNAPL were tested. In the abiotic diffusion-cells, a linear steady state TCE concentration profile between the DNAPL and the water layer developed beyond 21 d. In the biotic diffusion-cells, TCE was completely converted into cis-dichloroethene (cis-DCE) at 2.5 cm distance of the DNAPL. Dechlorination was likely inhibited up to a distance of 1.5 cm from the DNAPL, as in this part the TCE concentration exceeded the culture's maximum tolerable concentration (2.5mM). The DNAPL dissolution fluxes were calculated from the TCE concentration gradient, measured at the interface of the DNAPL layer and the porous layer. Biotic fluxes were a factor 2.4 (standard deviation 0.2) larger than abiotic dissolution fluxes. This diffusion-cell setup can be used to study the factors affecting the bio-enhanced dissolution of DNAPL and to assess bioaugmentation, pH buffer addition and donor delivery strategies for source zones., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objectives: Tetrachloroethylene is the dominant solvent used in dry cleaning worldwide and many workers are potentially exposed. We report here on results of 1296 measurements of tetrachloroethylene undertaken in Nordic dry cleaning shops 1947-2001., Methods: We searched documents and files in the Nordic institutes of occupational health for air measurements of tetrachloroethylene. Repeated measurements from the same facility during a short time interval were registered only once using the time-weighted average. We registered also changes over time in occupational exposure limits (OELs) to tetrachloroethylene., Results: Only scattered measurements were available from the early years, and the exposure level seemed fairly stable up until the mid 1970s. The median exposure level was 20 p.p.m. in 1976 and decreased to 3 p.p.m. in 2000. Exposure levels in the four Nordic countries followed similar trends. In the late 1960s, the OELs varied between the Nordic countries from 30 to 100 p.p.m. Sweden was first to lower the limit, but limits gradually converged over time. At present, Denmark, Finland, and Sweden use 10 p.p.m., while Norway uses 6 p.p.m. Over time, the average observed exposure level was lower than the OEL in all countries, but in Denmark and Sweden, up to one-third of measured exposures exceeded the OEL. Overall, the stationary measurements for maintenance work showed 36 p.p.m., while the personal measurements showed 7.5 p.p.m. for dry cleaners and 6.25 p.p.m. for shop assistants., Conclusion: The Nordic data illustrate that it is possible over time to control chemical exposures even in an industry consisting of many small and scattered work places.

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 μg 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.