Concentrations Of Tetrachloroethene Research Articles

Life Cycle Assessment and Indoor Environmental Quality of Wooden Family Houses

This article analyzes in detail the impact of wooden houses on the environment using the life cycle assessment (LCA) methodology and at the same time evaluates the indoor environmental quality (IEQ) in these houses. The investigated detached family houses had a wooden structure. The first one had a bearing system made of a wooden frame; other materials were conventional. The second house was built entirely of log wood. Given the high risk of greenhouse gas emissions, the concentration of which in the atmosphere is causing global climate change, the global warming potential (GWP) indicator is crucial. According to results, the family house built entirely of wood and with a biomass boiler significantly reduces CO2 emissions and is therefore considered from the LCA point of view as a more suitable alternative compared to a house with a wooden frame structure. The building materials with the highest share involved in the creation of GWP include concrete structures (38–48%), ceramic roof tiles (33%) and plasterboard (15%). Plasterboard cladding (55%), concrete structures (17–19%), oriented strand board OSB (9–22%), impregnated wooden structures (31–52%) and plastic windows (9%) are the most involved in acidification potential (AP) and eutrophication potential (EP). Plasterboard structures (21%), impregnated wood materials (47.4%), reinforced concrete structures (12%) and mineral wool and roof tiles significantly contribute to the creation of photochemical ozone creation potential (POCP) and ozone depletion potential (ODP). The indoor environmental quality was evaluated through short-term measurements of basic physico-chemical parameters. Since both houses have different characteristics, the aim of this monitoring was to evaluate the actual state of IEQ in selected wooden houses under real conditions. Based on the recorded results, it can be stated that neither presented wooden house, in terms of thermal-humidity microclimate, concentration of CO2 and particulate matter, represents an environment with a negative impact on their occupants. With regards to volatile organic compounds (VOCs), the increased concentrations of xylenes and tetrachlorethylene in the log house were probably caused by the application of impregnation and protective coatings six months before monitoring. In this case, the concentration of tetrachloroethene, which is considered a potential carcinogen, was six times higher than the legislative limit. For VOCs, such as limonene, isobutylene and n-butylacetate, which were found in the wooden frame house, no limits are set. The legislative limits for xylenes and tetrachlorethylene in this house have not been exceeded, and therefore the IEQ cannot yet be considered harmful for health. The presence of all the mentioned VOCs in the interior air of the wooden frame house is more related to the activities of occupants, as this house has been inhabited for several years.

Carbon isotope forensics for methane source identification

AbstractMethane (CH4) in ecosystems originates from ancient petroleum formed deep within the earth and/or via microbial fermentation of organic carbon and subsequent reduction of carbon dioxide (CO2). Given the complexity of different ecosystems, origins of CH4 present can be difficult to determine. This issue was realized in a situation where an antimethanogenic in situ chemical reduction (ISCR) remedial amendment containing organic carbon plus zero‐valent iron was applied to treat chlorinated solvents in groundwater at a former dry cleaner facility. The technology rapidly and effectively reduced the concentration of tetrachloroethene in groundwater thus meeting project goals without the stoichiometric accumulation of catabolites such as trichloroethene (TCE), cis‐1,2‐dichloroethene, or vinyl chloride and without excessive methanogenesis (e.g., <2 mg/L) in the treated area. However, approximately 9 months after treatment, increased levels of CH4 (from 5 to 10 mg/L) were observed downgradient from the treated area. The applied remedial amendment contained approximately 60% (weight basis) fermentation organic carbon and was therefore a potential source of this CH4. However, there was <500 mg/L total organic carbon in groundwater emanating from the upgradient treatment area which was unlikely sufficient to produce that much CH4. Moreover, the soil gas also contained benzene, toluene, ethylbenzene, and xylenes and other gasoline constituents. These data suggested that the presence of three gasoline/diesel underground storage tanks that were previously closed in place with no active remediation performed could be the source of elevated CH4. Thirdly, there were sewer lines, utilities, multiple gasoline stations, and industrial activities in the immediate area. With an initial assumption that CH4 source(s) could include the ISCR amendment over stimulation of production, gasoline sourced CH4 from nearby leaking lines, or sewage from local fractured pipes, carbon isotope analyses—radiocarbon (Δ14C) and stable carbon (δ13C)—were coupled with CH4 and CO2 concentration data from groundwater samples to determine the origin of respired carbon. The δ13C range for carbon sources respired in the process would be approximately −26.5‰ to −33.0‰ for the ISCR amendment and total petroleum hydrocarbons (TPH) residuals, respectively. Δ14C is approximately 0‰ and −999‰ for the ISCR amendment (young carbon) and TPH (old carbon), respectively. The isotopic signature of respired gasses confirmed that elevated CH4 downgradient of the treated area originated primarily from sewer gasses (or fermentation of liquids released from sewer lines). This study provides an overview of the capability to apply carbon isotope geochemistry to confirmation of remedial protocols and sources of anthropogenic carbon pools that conclusively identify the origin of CH4 in a complex ecosystem undergoing a remedial action.

Tetrachloroethene. Documentation of proposed values of occupational exposure limits (OELs)

etrachloroethene is a colorless, volatile liquid used as a chlorinated solvent in chemical laundries, in metal, machine, aerospace and paint and varnish removers. It is an intermediate for the synthesis of chemical compounds. It has found use as a medium in heat exchangers, in veterinary medicine and for disinfection of grain by fumigation. The production volume of tetrachloroethene in the EU is 100,000–1,000,000 t / year. The monograph along with the proposed hygiene standard for tetrachloroethene was re-developed due to the setting of a new limit value in biological material (BLV) in SCOEL, including measurement of tetrachloroethene concentration in exhaled air and a decrease in BLV value in blood, compared to the one recommended by the Inter-Ministry Committee for OEL and OEL the value of permissible concentration of tetrachloroethene in biological material (DSB). According to SCOEL, for substances absorbed through the skin, including tetrachloroethene, there is a particular need to monitor workers' biological exposure to ensure the highest possible level of protection. According to the harmonized EU classification, tetrachloroethene is a category-2 carcinogen with risk phrase: Suspected of causing cancer. There is limited evidence of a carcinogenic effect of tetrachloroethene in humans and sufficient evidence of a carcinogenic effect in laboratory animals (hepatocellular carcinoma and hepatocellular adenoma and lymphocytic leukemia). In both humans and laboratory animals, the effects of acute and chronic exposure to tetrachloroethene are primarily associated with the central nervous system, liver and kidneys. Central nervous system disorders are manifested by headache, dizziness, impairment or abnormal coordination, and other disorders found with neuropsychological tests. Acute inhalation toxicity is also irritating to tetrachloroethene on the eyes and respiratory mucosa. The metabolites of tetrachloroethene are mainly responsible for its metabolites formed in the process of conjugation with glutathione in the liver and then activated in the kidneys with the participation of beta-lyase. The results of epidemiological studies do not clearly indicate the effect of tetrachloroethene on human reproduction or embryotoxic effects. Admittedly, effects on reproduction, embryotoxic and teratogenic effects of tetrachloroethene have been reported in some studies on laboratory animals, exposed to this substance in very high concentrations, though. In Poland, the maximum permissible concentration of tetrachloroethe at 85 mg/m3 and the maximum permissible instantaneous concentration at 170 mg / m3 are currently in force. The determined DSB value is 1.2 mg tetrachloroethene / L capillary blood in a sample taken 15–20 min after the end of work on the 4th and 5th day of exposure. The critical effect of tetrachloroete are disorders in the central nervous system. The value of the hygiene standard was derived based on the LOAEL value (lowest concentration causing harmful effects) of 680 mg /m3, obtained from a study on volunteers exposed to tetrachloroethene for 1 h. In volunteers at the tested concentration headache and drowsiness and slight eye irritation were noted. The proposed MAC value for tetrachloroethene is 85 mg/m3, and the MAC value is 170 mg/m3. It was proposed to take a concentration of 0.3 mg/l capillary blood collected before the last work shift on the 5th day of work as the DSB value of tetrachloroethene. It was recommended to label tetrachloroethene with the notation "skin" (absorption of the substance through the skin may be as important as when inhaled). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

Application of phytoscreening to three hazardous waste sites in Arizona

The great majority of prior phytoscreening applications have been conducted in humid and temperate environments wherein groundwater is relatively shallow (~1–6m deep). The objective of this research is to evaluate its use in semi-arid environments for sites with deeper groundwater (>10m). To that end, phytoscreening is applied to three chlorinated-solvent hazardous-waste sites in Arizona. Contaminant concentrations were quantifiable in tree-tissue samples collected from two of the sites (Nogales, Park-Euclid). Contaminant concentrations were detectable, but not quantifiable, for the third site. Tree-tissue concentrations of tetrachloroethene (PCE) ranged from approximately 400–5000ug/kg wet weight for burrobrush, cottonwood, palo verde, and velvet mesquite at the Nogales site. In addition to standard trunk-core samples, leaf samples were collected to test the effectiveness of a less invasive sampling method. Leaf-sample concentrations were quantifiable, but several times lower than the corresponding core-sample concentrations. Comparison of results obtained for the test sites to those reported in the literature suggest that tree species is a major factor mediating observed results. One constraint faced for the Arizona sites was the relative scarcity of mature trees available for sampling, particularly in areas adjacent to industrial zones. The results of this study illustrate that phytoscreening can be used effectively to characterize the presence of groundwater contamination for semi-arid sites with deeper groundwater.

Occurrence of volatile organic compounds in shallow alluvial aquifers of a Mediterranean region: Baseline scenario and ecological implications

A regional survey of eight volatile organic compounds (VOCs), namely BTEX (benzene, toluene, ethylbenzene and p-xylene) and four chlorinated aliphatic hydrocarbons (CAHs: chloroform, 1,2-dichloroethane, trichloroethene and tetrachloroethene), was carried out at 174 sites, in 17 alluvial aquifers of Abruzzo, a Mediterranean region of southern Italy, from 2004 to 2009. Frequency of detection, concentration range, spatial distribution pattern, and temporal trend of contaminant concentration in each aquifer were analyzed as well as the relationships between VOC concentrations and the total amount of precipitation during the 90days preceding each sampling date. A review of published ecotoxicological data, providing an indication of the biological risk associated with the observed levels of VOC contamination, was presented and discussed. BTEX concentrations were under detection limits in all the investigated aquifers, indicating absence of contamination. In contrast, CAH contamination occurred in 14 out of 17 aquifers. The two most frequently detected compounds were chloroform and tetrachloroethene. No significant temporal trend was observed for chloroform and tetrachloroethene concentrations during the six years of observation, indicating the persistence of stable contaminations, except for some slightly decreasing trends observed in three out of 17 aquifers. In four aquifers chloroform and tetrachloroethene concentrations increased with precipitations in the preceding months. Spatial patterns of contamination differed among aquifers, indicating highly complex contaminant distributions at aquifer scale not related to single-plume geometries. Patterns of contamination by chloroform and tetrachloroethene in the most urbanized aquifers were likely associated with multiple sources of VOCs not clearly detectable at the scale used in this study. In five out of 17 aquifers, chloroform and tetrachloroethene co-occurred at concentrations that are lethal to groundwater-dwelling organisms under a short exposure period (four days). Future studies should therefore consider the possibility that in the other aquifers groundwater-dwelling organisms might be physiologically damaged by sublethal VOC concentrations.

Use of silicate minerals for long-term pH control during reductive dechlorination of high tetrachloroethene concentrations in continuous flow-through columns

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 6.5months. 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 84days 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.

Field Evidence of Dissolution and Degradation Rates Enhancement During ISCR and ENA Treatments of Chlorinated Solvents

AbstractThis article presents field tests comparing two methods of treatment of chlorinated solvents undertaken at the same site. The site is an automobile factory where two chlorinated solvents (CS) plumes were identified. At the first source, in situ chemical reduction (ISCR) was applied, while at the second one, enhanced natural attenuation (ENA) was used. A set of specific multilevel sampling wells were installed approximately 20 m downgradient of the sources to estimate the efficiency of the treatments. The presence of a low‐permeability layer (source 1) or a thick oil lens (source 2) in the top part of the aquifer prevented the CS from reaching the bottom of the aquifer. These layers led to difficulties treating the contamination. At the ISCR and ENA treatment zones, the concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) did not change significantly, while the concentration of metabolites (cis‐1,2‐DCE, vinyl chloride, and ethene) significantly increased 50 to 150 days after treatment. Due to high concentration of CS in the source zone, a mass balance calculation, including chlorine, was possible. It showed that around 1 to 2 percent of the injected products were used to reduce the CS. A detailed analysis and 1D analytical modeling of CS concentrations showed that the treatment led to a large (two to three times) increase in dissolution of the organic phase. This explains why, despite an efficient treatment, the PCE and TCE concentrations remained virtually unchanged. Degradation rates also increased due to the treatment. Due to some differences in the source‐zone chemistry, it was not possible to differentiate between the ISCR and ENA efficiencies. © 2013 Wiley Periodicals, Inc.

Carbon and Chlorine Isotope Ratios of Chlorinated Ethenes Migrating through a Thick Unsaturated Zone of a Sandy Aquifer

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.

Dehalorespiration Model That Incorporates the Self-Inhibition and Biomass Inactivation Effects of High Tetrachloroethene Concentrations

In the vicinity of dense nonaqueous phase liquid (DNAPL) contaminant source zones, aqueous concentrations of tetrachloroethene (PCE) in groundwater may approach saturation levels. In this study, the ability of two PCE-respiring strains (Desulfuromonas michiganensis and Desulfitobacterium strain PCE1) to dechlorinate high concentrations of PCE was experimentally evaluated and depended on the initial biomass concentration. This suggests high PCE concentrations permanently inactivated a fraction of biomass, which, if sufficiently large, prevented dechlorination from proceeding. The toxic effects of PCE were incorporated into a model of dehalorespirer growth by adapting the transformation capacity concept previously applied to describe biomass inactivation by products of cometabolic TCE oxidation. The inactivation growth model was coupled to the Andrews substrate utilization model, which accounts for the self-inhibitory effects of PCE on dechlorination rates, and fit to the experimental data. The importance of incorporating biomass inactivation and self-inhibition effects when modeling reductive dechlorination of high PCE concentrations was demonstrated by comparing the goodness-of-fit of the Andrews biomass inactivation and three alternate models that do capture these factors. The new dehalorespiration model should improve our ability to predict contaminant removal in DNAPL source zones and determine the inoculum size needed to successfully implement bioaugmentation of DNAPL source zones.

SAW RFID-Tags for Mass-Sensitive Detection of Humidity and Vapors

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.

Distribution of volatile organic compounds around a polluted river

The objectives of this study were to investigate the species and the concentration distribution of volatile organic compounds around a heavily polluted river. Air samples were collected seasonally at different locations near the polluted river. Samples were then analyzed by gas chromatography (electron capture detector for chlorinated organic compounds and flame ionization detector for ordinary hydrocarbons). The data was then analyzed by the statistical product and service solutions software. The results showed that total of 26 species of volatile organic compounds were identified. Each individual had its own concentration distribution pattern at different seasons and aliphatic volatile organic compounds displayed much higher concentrations than most benzenoic volatile organic compounds. In aliphatic volatile organic compounds, 1,2-dibromo-3-chloropropane, hexachlorobutadiene and 1,2-dibromoetane had much higher concentrations at the nearby environment of the river and they have been claimed to be carcinogenic to some experimental animals and possibly to human. Therefore, It is in doubt that for a long term, the volatile organic compounds evaporating out of the stream may threat the health of the residents living very close to the river. The concentrations of tetrachloroethene, 1,1,2,2-tetrachloroethane, hexachlorobutadiene, dibromoetane, dichlorobenzene and sec-butylbenzene appeared at the nearby environment of the river had significant correlations (P < 0.05) with those of each other or many other volatile organic compounds.

The impact of composition on the physical properties and evaporative mass transfer of a PCE–diesel immiscible liquid

The impact of immiscible-liquid composition on mass transfer between immiscible liquid and vapor phases was evaluated for a complex mixture of chlorinated solvents and petroleum hydrocarbons. A mixture of tetrachloroethene and diesel was discovered at a site in Tucson, Arizona. Partitioning of tetrachloroethene into a layer of diesel has been observed, with resultant concentrations of tetrachloroethene up to approximately 15% by weight. The density, viscosity, surface tension, and interfacial tension were measured for tetrachloroethene–diesel mixtures with tetrachloroethene fractions ranging from 7% to 32%, and the results indicated that immiscible-liquid composition did impact the physical properties of the tetrachloroethene–diesel mixture. The results of batch phase-partitioning experiments were compared to predictions based on Raoult’s Law, and the analysis indicated that immiscible-liquid/vapor and immiscible-liquid/water partitioning were both essentially ideal. Flow-cell experiments were conducted to characterize steady-state tetrachloroethene removal from the tetrachloroethene–diesel mixture via vapor extraction. The effluent concentrations for the experiment conducted with free-phase immiscible liquid were comparable to equilibrium values. Conversely, the effluent concentrations were significantly lower for the experiment wherein a residual saturation of immiscible liquid was distributed within sand. The lower concentrations for the latter experiment were attributed to dilution effects associated with a nonuniform distribution of immiscible liquid within the flow cell.

Bioremediation of a former dry cleaner using potassium lactate

AbstractChlorinated solvents were released to the surficial groundwater underneath a former dry cleaning building, resulting in a groundwater plume consisting of high concentrations of trichloroethene (TCE) and cis‐1,2‐dichloroethene (cis‐1,2‐DCE) and low concentrations of tetrachloroethene (PCE) and vinyl chloride. The initial remedial action included chemical oxidation via injection of 14,400 gallons of Fenton's Reagent in March 2002, and an additional 14,760 gallons in April 2002. A sharp reduction of contaminant concentrations in groundwater was observed the following month; however, rebound of contaminant concentrations was evident as early as October 2002. A source area of PCE‐impacted soils was excavated in June 2004. Following the excavation, Golder Associates Inc. (2007) implemented a biostimulation plan by injecting 55 gallons of potassium lactate (PURASAL® HiPure P) in September 2005, and again in February 2006. Comparing the preinjection and postinjection site conditions, the potassium lactate treatments were successful in accomplishing a 40 to 70 percent reduction in mass within four months following the second injection. Elevated vinyl chloride concentrations have persisted through both injection events; however, significant vinyl chloride reduction has been observed in one well with the highest total organic carbon (TOC) concentrations following each injection. © 2008 Wiley Periodicals, Inc.

PCE, TCE, and TCA Vapors in Subslab Soil Gas and Indoor Air: A Case Study in Upstate New York

AbstractA comprehensive investigation of subsurface vapor intrusion into buildings in the Village of Endicott in upstate New York provided an unusually rich data set for studying the relationship between subslab soil gas and indoor air concentrations. The study concludes that vapor intrusion into buildings with basement foundations and concrete floors generally results in ratios of subslab soil gas to indoor air concentrations greater than 100:1 at this site. The data set also shows that ambient background‐ and indoor‐contaminant vapor sources can result in measured indoor air concentrations that could be mistakenly ascribed to subsurface‐contaminant vapor sources and erroneous conclusions regarding the relationship between subslab soil gas and indoor air concentrations. By separating the measured subslab soil gas concentrations of tetrachloroethene, trichloroethene, and 1,1,1‐trichloroethane into low‐ and high‐range data subsets, the influence of background and indoor sources of these compounds was more easily discerned.

Time-Resolved Experiments on the Chlorine Atom Initiated Oxidation of Tetrachloroethene (Cl2CCCl2)

We report time-resolved measurements relevant to the atmospheric oxidation of tetrachloroethene (Cl 2 C= CCl 2 ) and pentachloroethane (CCl 3 CCl 2 H). Cl atoms were produced by photolysis of Cl 2 at 351 nm, using the output from a pulsed excimer laser, in the presence of C 2 Cl 4 and a large excess of O 2 . Experiments were performed with and without NO present. The formation of the reaction products C(O)Cl 2 and CCl 3 C(O)Cl was followed, in real time, via absorption of infrared radiation provided by tunable diode lasers. Contrary to the finding of Hasson and Smith (J. Phys. Chem. A 1999, 103, 2031) but in agreement with the results of Thiiner et al. (J. Phys. Chem. A 1999, 103, 8657), the relative yields of C(O)Cl 2 and CCl 3 C(O)Cl were found to be independent of the concentration of C 2 Cl 4 . However, as found in both previous studies, the relative yields were sensitive to whether the CCl 3 CCl 2 O radical was formed by the reaction between CCl 3 CCl 2 O 2 and NO or by the mutual reaction of two CCl 3 CCl 2 O 2 radicals. From the results it was possible to estimate the branching ratio k 5 a /(k 5 a + k 5 b ) for decomposition of the CCl 3 CCl 2 O radical by the pathways CCl 3 CCl 2 O (+M) → CCl 3 C(O)Cl + Cl (+M) and CCl 3 CCl 2 O (+M) → CCl 3 + C(O)Cl 2 (+M). With CCl 3 CCl 2 O formed from CCl 3 CCl 2 O 2 + NO, (k 5 a /[k 5 a + k 5 b ]) = 0.69 ′ 0.13, whereas with 2CCl 3 CCl 2 O formed from 2CCl 3 CCl 2 O 2 , (k 5 a /[k 5 a + k 5 b ]) = 0.91 ′ 0.21. Attempts to use literature values of the rate constants in modeling, (a) how the concentration of CCl 3 C(O)Cl varied with time following the initiation of reaction and (b) how the yield of CCl 3 C(O)Cl depended on the initial concentration of tetrachloroethene, were not successful. Agreement between the experimental results and the calculations could only be obtained using rate constants for the reactions between CCl 3 CCl 2 O 2 and NO and between CCl 3 CCl 2 O 2 and NO 2 that were appreciably larger than previous values.

Organic pollutants in the Odra river ecosystem

The paper presents the results of the analysis of water and bottom sediment samples from different locations along the Odra river, collected during eight campaigns in the years 1997–2000. All the basic organic pollutants were determined. Pollution of water with PCBs was negligible while with PAHs was not critical. Concentrations of volatile organochlorine compounds in water were the highest in Brzeg Dolny and its surroundings. Concentrations of tetrachloroethene were exceptionally high in the Szczecin Lagoon. The Odra sediments were non-polluted or only slightly polluted with PCBs, pesticides and different classes of volatile organic pollutants. However, PAHs were present in rather large concentrations, especially in the upper course of the Odra river. The data obtained contributed to the evaluation of pollutants discharges to the Baltic sea via Szczecin Lagoon as well as to the characterization of pollution sources (point sources and area sources) in the Odra catchment area.

ART in‐well air stripping—An innovative technology succeeds where other technologies have failed

AbstractAccelerated Remediation Technologies LLC (ART) developed a proprietary (patent‐pending) effective remediation technology that is based on verified and established concepts. The ART technology combines in‐situ air stripping, air sparging, soil vapor extraction, enhanced bioremediation/oxidation, and Dynamic Subsurface CirculationTM in an innovative wellhead system. The system is designed to accommodate a 4‐inch well and is cost‐effective when compared with other remediation technologies. The air‐sparging component results in lifting the water table. This lifting of the water in the well causes a net reduction in head at the well location. Vacuum pressure (the vapor‐extraction component) is applied on top of the well point to extract vapor from the subsurface. The negative pressure from the vacuum extraction results in water suction that creates additional water lifting (mounding). A submersible pump is placed at the bottom of the well to recirculate water to the top for downward discharge through a spray head. The water cascades down the interior of the well similar to what occurs in an air‐stripping tower. Enhanced stripping via air sparging near the bottom of the well occurs simultaneously. In essence, the well acts as a subsurface air‐stripping tower. The pumped‐and‐stripped, highly oxygenated water flows down well annulus and over the “mounded” water back in to the aquifer, which creates a circulation zone around the well to further enhance cleanup.The ART technology has been implemented at several sites nationwide, including industrial laundry facilities, manufacturing plants, and service stations, and has achieved significant reductions in contaminant concentrations. Specifically, a concentration of tetrachloroethene (PCE) decreased from 2,700 to 240 μg/l, in 13 days. In less than three months, the concentrations dropped further to 79 μg/l, which is within the range of background levels. Other sites utilizing the technology have exhibited similar reduction trends in complex subsurface environments. © 2002 Wiley Periodicals, Inc.

Influence of relative humidity in sensing halogenated hydrocarbons with Reflectometric Interference Spectroscopy (RIfS)

For stand-alone sensor systems apart from defined laboratory circumstances sensors are required, which show a high stability against perturbing environmental influences like the relative humidity (r.h.). We present a portable sensor system, which is capable to quantify tetrachloroethene (TCE) in humid air. The system works highly reproducible and shows only negligible cross-sensitivity towards relative humidity. This allows a single calibration valid from 0 to 80% r.h.. Therefore, referencing with an extra sensor for humidity is not necessary. Binary mixtures of TCE and freone R113 were quantified for 0 and 40% r.h. with a root mean square error of prediction of approximately 3% with respect to the maximum concentration of TCE and R113. The sensitive elements used in the experiments consisted of thin polymer films on glass substrates. The measurements were performed with the optical measurement technique RIfS (Reflectometric Interference Spectroscopy).

Biodegradation of High Concentrations of Tetrachloroethene in a Continuous Flow Column System

A long-term (2.5 years) study of the anaerobic biodegradation of high concentrations of perchloroethylene (PCE) was carried out in a continuously operated laboratory column filled with sand which was inoculated with biomass from an anaerobic digester. Concentrations of PCE fed to the column were increased from 12 IM to over 600 IM over 21 months, with methanol added as electron donor. Vinyl chloride (VC) was the terminal product of PCE dechlorination for the first 21 months at which point significant conversion of VC to ethylene (ETH) was detected. The onset of ETH production coincided with acetogenesis becoming the primary pathway for methanol metabolism. ETH production occurred in the column in the presence of PCE and TCE. Varying methanol:PCE molar ratios from 1.4 to 7.5 had little effect on the transformation of PCE and TCE to VC. The degradation of VC to ETH was much more sensitive, and VC accumulated when the methanol:PCE molar ratio dropped below 5.0. Withdrawal of PCE from the system for a 5 month period and maintenance of the column on methanol alone did not result in the loss of PCE degradation capability of the consortium.

Global Distribution of Tetrachloroethene in the Troposphere: Measurements and Modeling

The tropospheric concentrations of the anthropogenic trace compound tetrachloroethene (perchloroethylene, per, PCE, C[sub 2]Cl[sub 4]) were measured over 8 years between 1982 and 1989 in both hemispheres at remote sampling sites representing the baseline level of tetrachloroethene. Air sampling was performed by adsorption on Tenax, thermal desorption, and gas chromatographic separation with electron capture detection (HRGC-ECD). The mean atmospheric concentrations of tetrachloroethene in both northern subhemispheres and the Southern Hemisphere are regarded as representative for these tropospheric boxes: 21 [+-] 5 pptv (154 [+-] 40 ng/m[sup 3]) for the box 90-30[degrees]N, 7 [+-] 3 pptv (51 [+-] 26 ng/m[sup 3]) for the box 30-0[degrees]N, and 2.2 [+-] 0.5 pptv (16 [+-] 4 ng/m[sup 3]) for the Southern Hemisphere. The measured atmospheric distribution of tetrachloroethene can be described by a simple two-box model of the troposphere. The measurements served for the optimization of the exchange parameters in a three-box model as well. Global fluxes of tetrachloroethene within the troposphere and in exchange with the stratosphere and the oceans are estimated. 66 refs., 2 figs., 8 tabs.