Abstract  A new inexpensive modification approach enabled continuous on-line automatic analysis of volatile organic compounds (VOCs) in small (0.1-70 ml/min) sample streams while maintaining all capabilities on a purge-and-trap system. Commerically available automated VOC analyzers require large (liters-per-hour) sample streams. VOCs in laboratory experiments and small sample streams are usually monitored by grab analysis. This paper evaluates the performance of continuously and automatically monitoring VOCs in small sample streams on a modified purge-and-trap system. A 1 ml/min stream with 30 ppb (10(9)) trichloroethane and 260 ppb tetrachloroethene aqueous standards was monitored unattended for 3 days with 2-3% relative standard deviations. The competitive breakthrough of VOCs through liquid chromatography carbon minicolumns was studied.

Abstract  Ultrasound-assisted emulsification microextraction (USAEME) followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) for simultaneous extraction, preconcentration and determination of trace levels of aluminum, copper, iron and zinc in Oscillatoria, Juncus littoralis tissues and wetland water samples is presented. Sodium diethyldithiocarbamate trihydrate (Na-DDTC.3H(2)O) was used as a chelating agent and tetrachloroethylene was selected as an extraction solvent. The effective parameters of the USAEME method including volume of extraction solvent, ultrasonic time, salt concentration, temperature, concentration of ligand and pH were investigated by a fractional factorial design. The results showed that temperature had no considerable effect on the efficiency. A Box-Behnken design (BBD) was applied to optimize the effective parameters. The optimal conditions were obtained as 48 mu L for volume of extraction solvent, 6 min for ultrasonic time, 16.6 (w/v %) for salt concentration, 1440 mg L(-1) for concentration of the ligand and 7 for pH. The linear dynamic range (LDR) was 1-1000 mu g L(-1) with determination coefficient of 0.994-0.998. The limits of detection (LODs) and relative standard deviations (RSDs) were 0.64-0.91 mu g L(-1) and 2.6-5.3%, respectively. The method was successfully applied to the determination of Al, Cu, Fe and Zn in real environmental samples and satisfactory relative recoveries (92-99%) were obtained.

Abstract  Retention capacities were measured in the laboratory for n-hexane and tetrachloroethylene (PCE) in three soils at varying soil water contents. Two experimental techniques were used; 1) saturation/drainage experiments where the soil columns were saturated with the chemical and allowed to drain freely for 24 h, and 2) spill simulations where a known amount of chemical was spilled on the surface of the soil column and allowed to infiltrate for one hour. Results show that the retention capacities on a volume basis were independent of chemical type. However, the retention capacities did decrease with decreasing porosity and increasing soil water content. The decrease of retention capacity with respect to soil water content was significant, with the decreases ranging from 38% to 94%. The implication of this decrease is rapid chemical penetration into the subsurface. Retention capacities obtained from spill simulations were consistently lower than those obtained by the saturation/drainage experiments due to hysteresis.

Abstract  This study considers the assimilation problem of subsurface contaminants at the port of Rotterdam in the Netherlands. It involves the estimation of solute concentrations and biodegradation rates of four different chlorinated solvents. We focus on assessing the efficiency of an adaptive hybrid ensemble Kalman filter and optimal interpolation (EnKF-OI) and the exact second-order sampling formulation (EnKF(ESOS)) for mitigating the undersampling of the estimation and observation errors covariances, respectively. A multi-dimensional and multi-species reactive transport model is coupled to simulate the migration of contaminants within a Pleistocene aquifer layer located around 25m below mean sea level. The biodegradation chain of chlorinated hydrocarbons starting from tetrachloroethene and ending with vinyl chloride is modeled under anaerobic environmental conditions for 5 decades. Yearly pseudo-concentration data are used to condition the forecast concentration and degradation rates in the presence of model and observational errors. Assimilation results demonstrate the robustness of the hybrid EnKF-OI, for accurately calibrating the uncertain biodegradation rates. When implemented serially, the adaptive hybrid EnKF-OI scheme efficiently adjusts the weights of the involved covariances for each individual measurement. The EnKFESOS is shown to maintain the parameter ensemble spread much better leading to more robust estimates of the states and parameters. On average, a well tuned hybrid EnKF-OI and the EnKFESOS respectively suggest around 48 and 21% improved concentration estimates, as well as around 70 and 23% improved anaerobic degradation rates, over the standard EnKF. Incorporating large uncertainties in the flow model degrades the accuracy of the estimates of all schemes. Given that the performance of the hybrid EnKF-OI depends on the quality of the background statistics, satisfactory results were obtained only when the uncertainty imposed on the background information is relatively moderate.

Abstract  Aqueous solutions of trichloroethylene (TCE) and tetrachloroethylene (PCE) were treated in a flow-through reactor equipped with ultrasound and ultraviolet light sources. The reactor was operated as sonolysis (US), photolysis (U'V), and simultaneous photosonolysis (UV/US) reactors; then as US, UV, and sequential UV/US reactors with the installation of a partition in the reactor. The reactor without the partition was simulated by using one continuously stirred-tank-reactor (1-CSTR) model, and the reactor with the partition was simulated by using the sequential CSTR model. Through model calibration, the decomposition rate constants and reactor efficiencies for the removal of TCE and PCE were evaluated. The results suggest that the combined effect of UV and US on the decomposition of TCE and PCE is synergistic in both the simultaneous and sequential UV/US modes, that the rate constants of sonolysis and photolysis are greater with the sequential combination than with the simultaneous combination, and that overall efficiency is higher for the reactor with the partition than for the one without it.

Abstract  In this study, sorption and the transport mechanism of surfactants in clayey soil was examined. The adsorption and desorption isotherms for sodium dodecyl sulfate (SDS) and biosurfactant (UH-biosurfactant) with sand and kaolinite were quantified. Kaolinite clay had the highest sorption capacity compared to blasting sand. Miscible displacement breakthrough experiments were done in order to determine the transport parameters. Transport parameters such as the dispersion coefficient (D) and the retardation factor (R) of the above-mentioned surfactant solutions were determined in clayey soils [sand (82.5 %) and kaolinite (17.5 %) mixture] with and without ionic strength. In this study 0.1 g/L NaCl was used as the electrolyte solution. A two-region transport convective-diffusive model was used to model the breakthrough curves of the surfactants. This model resulted in excellent descriptions of the data. Bromide ions were chosen as the tracer material in order to characterize the column. Perchloroethylene (PCE) is used in various kinds of industrial and commercial applications. SDS and UH-biosurfactant were used to flush the PCE contaminated soil. UH-biosurfactant solubilized more PCE compared to that of SDS in contaminated soils.

Abstract  There has been considerable interest in the use of Fe(0) for the treatment of highly chlorinated aliphatic hydrocarbons (CAHs). Because early field studies found little biological contribution to degradation, much of the recent research has focused on abiotic processes. However, previous experiments in our laboratory have demonstrated that the rate and extent of carbon tetrachloride (CT) and chloroform (CF) degradation were enhanced when Fe(0) and methanogenic enrichment or methanogenic pure cultures were incubated together. In this study, acetate- or lactate-enriched methanogenic cultures were added to columns containing a steel wool support medium. Fe(0) served as the sole exogenous electron donor. CT, tetrachloroethene (PCE), and 1,1,1,-trichlorothane (1,1,1,-TCA) were fed to columns alone and in mixtures in reduced mineral medium. Columns were operated for periods of up to 90 months. Based on extent of dechlorination, an enhancement was observed for CT and 1,1,1-TCA when methanogenic enrichment was used in conjunction with Fe(0). Enhancement was not observed with PCE and, in fact, addition of methanogenic enrichment may inhibit the abiotic reaction. Furthermore, the addition of methanogenic enrichment accelerates corrosion of Fe(0), which may decrease the lifetime of Fe(0) treatment systems. This research should be helpful in developing remediation strategies for sites contaminated with CAHs.

Abstract  Solubility experiments of ethoxylates surfactants denoted as CiEOj (where C-i = hydrocarbon tail, EOj = oxyethylene groups, i = 6 to 8 and j = 3 to 5) in sub- and supercritical carbon dioxide were carried out at different temperatures, pressures, and concentrations in a Cailletet apparatus as a representative model for dry cleaning system. For a variety of compositions, results are reported for binary systems within temperature and pressure ranges 01(260 to 310) K and (2.0 to 10) MPa respectively. In each experiment, the surfactants reach equilibrium with carbon dioxide at different concentrations. The data show that with all the surfactants upon increasing concentration, the liquid-liquid (L-L) curve shifts to lower temperatures. Therefore, the one-phase solution gap is reduced in pressure and temperature at higher concentrations. When the length of the hydrocarbon tail remains constant and the ethoxylated chain is increased from three to five groups, the L-L curve once again shifts to lower temperatures and the two phases start earlier. This effect can be attributed to the higher surfactant's polarity due to the increase in j. On the other hand, when the number of ethoxylated groups j remains constant and the length of the hydrocarbon tail is increased from six to eight carbon atoms, no significant shift in the L-L curve is observed. That signals the fact that the appearance of two phases is directly related to the number of ethoxylated group which determine the polarity of the molecule. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  In textile finishing the possibility of substituting detrimental chemicals for less aggressive and biodegradable ones has been investigated intensely for years. Stricter and stricter regulations are passed. Many chemicals are forbidden or their maximum permissible amount to be used is restricted. New methods, effective chemicals, water purification and recycling and its reintroduction into the process are beeng introduced. It concerns short liquor ratios and new dye groups are introduced. Similar measures are also taken in the textile care. Eutrophin phosphates are substituted for other builders. By introduction of enzymes and bleaching activators efficient washing at lower temperatures resulting in lower detergent, water and energy consumption is facilitated. Hardly degradable surfactants have been substituted for biodegradable ones. Permissible perchlorethylene consumption should not exceed 2% of the amount in cleaned textile goods. Possibilities to use new environment-friendly solvents are examined. Sewn-in labels in textile products determine regulations of the textile care, mark quality and sometimes ecological value. Special eco-symbols provide information whether a textile product is manufactured in an environment-friendly way, and whether it contains detrimental substances.

Abstract  Catalytic hydrodechlorination is an effective and environmentally friendly alternative for the destruction of chlorine-containing organics. Since the byproducts are waste materials (HCl and Cl-2), it is important to find and apply inexpensive or natural materials having catalytic activity in hydrodechlorination. A potential catalyst of this type, the calcined "red mud" originated from the alumina process, was studied in comparison with other iron-containing catalysts, such as single (Fe2O3) and mixed oxides (Fe2O3/Al2O3) and modified zeolite (Fe-ZSM5). The red mud is a dangerous waste formed in large amount, nevertheless, it contains catalytically active oxides. The hydrodechlorination reactions were carried out in a fixed-bed flow reactor in the temperature range of 200-400 degrees C using hydrogen as reducing agent. The structure of the catalysts was characterized by XRD, IR and adsorption methods. The metal and chlorine contents of the used samples were also determined. The efficiency of the reductive destruction of 1,2-dichloroethane (DCE), 1, 1,2-trichlorethane (TRCE), 1, 1,2,2-tetrachloroethane (TCE), trichloroethene (TRCEE) and tetrachloroethene (TCEE) over mixed oxide originating from red mud is comparable to that obtained for synthetic catalysts. The solids used are not only catalysts, but reactants as well in these reactions. Therefore, these processes could be considered as gas-solid reactions. (c) 2005 Elsevier B.V. All rights reserved.

Abstract  The photodegradation of dichloromethane and of tetrachloroethylene in dilute aqueous solutions and of 1,2-dibromo-3-chloropropane (DBCP) in contaminated groundwater was carried out by illumination with natural, concentrated and simulated sunlight in the presence of air and suspended TiO2 or TiO2 Coated on silica gel. With tetrachloroethylene in homogeneous aqueous solutions, illumination with a high pressure mercury lamp resulted in photodegradation even in the absence of any additive, but the rate was significantly enhanced in the presence of powdered TiO2. The TiO2-promoted degradation of tetrachloroethylene with light of 313 nm or with natural sunlight was further increased by the addition of hydrogen peroxide. The rate of the homogeneous photolysis of tetrachloroethylene by illumination with light longer than 300 nm was not affected by the presence of nitrate ion. Using concentrated sunlight, the Tate of the photodegradation of aqueous tetrachloroethylene in the presence of H2O2 and suspended TiO2 was approximately linear with the light intensity, up to a light flux of about 80 kW m-2. With DBCP in polluted well-water from California, illumination in the presence of TiO2 resulted in a decrease in the halocarbon content of the water from the initial high concentration of 2.9 +/- 0.2 ppb to 0.4 +/- 0.1 ppb.

Abstract  Samples of fabrics made for collapsible potable water storage tanks by five manufacturers were used to evaluate leaching of organics under three test conditions: control medium (pH = 8.3) at 20-degrees-C; low-pH medium (pH = 5.8, Cl2 = 10 mg/L); and control medium at 50-degrees-C. The extraction procedures were basically those described in National Sanitation Foundation standard 61. Results indicated the presence of trace amounts of organic compounds, but the concentrations were well below existing health standards. The type and magnitude of the organics depended on the material used and the test conditions.

Abstract  Solutions containing hydrofluoric acid (HF), hydrochloric acid (HCl), and hydrogen peroxide (H2O2) were investigated as novel acidic, NOx-free etching mixtures for texturing of monocrystalline silicon wafers. High etch rates of up to 13.3 nm s(-1) were observed at room temperature, which are comparable to the etch rates of KOH-IPA solutions. The silicon surface was investigated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), indicating pyramidal textures for diamond wire and SiC-slurry sawn as well as saw-damage etched (polished) wafers. Non-stirred baths generate random pyramidal structures while constantly stirred solutions generate novel random inverted pyramidal surface structures. The light trapping efficiency of wafers etched by the HF-HCI-H2O2 solutions was compared by UV/vis-reflectivity measurements to KOH/i-propanol specimens indicating lower reflectivities for the HF-HCI-H2O2-treated samples. Using the 'wafer ray tracer' (pvlighthouse.com) the light absorption properties of monomodal and random inverted pyramid structures were simulated and compared to well-known random and monomodal textures for PERC solar cells, clearly indicating the best performance for random inverted pyramids. Besides, simulation of a PERC solar cell on a roof top at our university was performed, indicating improved performance, especially for random inverted pyramid textures. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  Chlorinated ethenes are among the most common environmental contaminants and are known or suspected carcinogens. This class of compounds includes perchloroethene (PCE), trichloroethene (TCE), and their breakdown products, including dichloroethene (DCE) isomers and vinyl chloride (VC). Engineers and scientists must be able to measure concentrations of these chemicals in water samples to assess site contamination, monitor clean-up progress, and test possible remediation technologies. Gas chromatography with flame ionization detection (GC/FID) is a common method for measuring these contaminants in environmental samples. In this study, we tested the hypothesis that FID response factors are equal for all chlorinated ethene compounds. The rationale for the investigation was that if the hypothesis is correct, a single calibration curve can be used for GC/FID analysis of all chlorinated ethene compounds, saving time and money during sample analysis. Based on our measurements, a single calibration curve (FID response versus mass of analyte injected) is applicable to analysis of PCE, TCE, and all three DCE isomers (r(2) = 0.990, n = 50 measurements), allowing for simplified quantification of those chemicals. However, the apparent FID response factor for VC was lower by similar to 40%, indicating that a separate calibration curve would need to be used to accurately estimate the VC concentration in water samples. The difference in the apparent VC response factor is caused predominantly by losses of VC to volatilization during the analysis.

Abstract  The release of industrial contaminants into the subsurface has led to a rapid degradation of groundwater resources. Contamination caused by Dense Non-Aqueous Phase Liquids (DNAPLs) is particularly severe owing to their limited solubility, slow dissolution and in many cases high toxicity. A greater insight into how the DNAPL source zone behavior and the contaminant release towards the aquifer impact human health risk is crucial for an appropriate risk management. Risk analysis is further complicated by the uncertainty in aquifer properties and contaminant conditions. This study focuses on the impact of the DNAPL release mode on the human health risk propagation along the aquifer under uncertain conditions. Contaminant concentrations released from the source zone are described using a screening approach with a set of parameters representing several scenarios of DNAPL architecture. The uncertainty in the hydraulic properties is systematically accounted for by high-resolution Monte Carlo simulations. We simulate the release and the transport of the chlorinated solvent perchloroethylene and its carcinogenic degradation products in randomly heterogeneous porous media. The human health risk posed by the chemical mixture of these contaminants is characterized by the low-order statistics and the probability density function of common risk metrics. We show that the zone of high risk (hot spot) is independent of the DNAPL mass release mode, and that the risk amplitude is mostly controlled by heterogeneities and by the source zone architecture. The risk is lower and less uncertain when the source zone is formed mostly by ganglia than by pools. We also illustrate how the source zone efficiency (intensity of the water flux crossing the source zone) affects the risk posed by an exposure to the chemical mixture. Results display that high source zone efficiencies are counter-intuitively beneficial, decreasing the risk because of a reduction in the time available for the production of the highly toxic subspecies. (C) 2015 Elsevier Ltd. All rights reserved.

Abstract  The possible hazards of occupational exposure on the reproductive health of workers is of great interest. In this review, epidemiological study designs suitable for reproductive studies and sources of outcome and exposure data are described with a few examples. Studies have been conducted on hormonal changes, semen quality, fertility, and various outcomes of pregnancy, e.g, spontaneous abortion, congenital malformations, perinatal mortality birthweight, and health and development of the children. Also, sex distribution of children has been investigated as a possible risk indicator in some recent studies. In epidemiological studies, retrospective or prospective cohort design, case referent and nested case referent designs have been used. The validity of epidemiological studies depend on reliable data on the health effect and the exposure. The registers on congenital malformations and on births and other outcomes of pregnancy are useful sources of data for epidemiological studies. The coverage of the register and the accuracy of its contents should be known if the register is used for research. Personal interview of the worker is an important source of information, although recall problems may weaken the quality of the data. The reliability of the answers may be increased by using a few complementary questions on possible medical confirmation of the event. If both the interview and register data are available, the reliability of the information increases, the same concerns exposure information also. Examples of some conducted studies are given.

Abstract  Dense nonaqueous phase liquid (DNAPL) contamination is a major environmental problem. Cosolvent flooding is proposed as a remedial alternative to water flooding. The efficacy of cosolvent flooding is a function of the degree of contact between the injected remedial fluid and the resident DNAPL. Poor contact may result from remedial fluids traveling in preferential flow paths which bypass trapped DNAPL. Thus, the motivation for this study was to use the preferential flow of air in porous media to enhance contact between the injected cosolvent and resident DNAPL. The study evaluated concurrent injection of cosolvent and air to improve the spatial extent of DNAPL removal in porous media. A 70% ethanol/30% water (v/v) cosolvent was injected simultaneously with air into a micron-model containing residual tetrachloroethylene (PCE). Double drainage displacement was observed as a dominant DNAPL removal mechanism in the initial period of the cosolvent-air flooding (i.e., gas displaced PCE that displaced water). The residual PCE residing in the preferential paths traversed by air was readily displaced. In addition to this initial PCE mobilization, air flowing through the preferential flow paths displaced cosolvent from these paths into other flow paths and facilitated dissolution of PCE.

Abstract  In recent years, considerable interest has been given to the in situ degradation of hazardous contaminants by stimulating indigenous microorganisms. Optimization of environmental conditions, especially oxidation-reduction potential (ORP), for metabolism of hazardous constituents by indigenous microorganisms may assist in cost- effective mitigation by enhanced bioremediation. Pseudomonas cepacia, the predominant species, was selected as the microorganism of study to evaluate ORP effects on biodegradation of carbon tetrachloride (CT), a common contaminant in many sites. Titanium (III) citrate was used to poise ORP at desired levels. Results indicate that initial ORP appears to be critical for initiating the CT degradation process. Substantial CT degradation occurred when cultures were poised at negative ORP conditions, while negligible CT removal was observed at oxidative ORP conditions. Accumulation of chloroform (CF) produced by CT metabolism was not observed, which may be attributed to its metabolism by P. cepacia and another pathway that preclude CF generation. The maximum biodegradation rate was found to occur at approximately -150 mv(2) and an overall substrate removal rate constant, K, of 6.9 x 10(-3) h(-1) was observed al an initial CT concentration of 323 mu g/L.

Abstract  A new method for the simultaneous determination of 12 volatile organic compounds (trans-1,2-dichloroethene, 1,1,1-trichloroethane, benzene, 1,2-dichloroethane, trichloroethene, toluene, 1,1,2-trichloroethane, tetrachloroethene, ethylbenzene, m-, p-, o-xylene) in water samples by headspace solid phase microextraction (HS-SPME)-gas chromatography mass spectrometry (GC-MS) was described, using a 100 mm PDMS (polydimethylsiloxane) coated fibre. The response surface methodology was used to optimise the effect of the extraction time and temperature, as well as the influence of the salt addition in the extraction process. Optimal conditions were extraction time and temperature of 30 min and -20 degrees C, respectively, and NaCl concentration of 4 mol L(-1). The detection limits were in the range of 1.1 x 10(-3)-2.3 mu g L(-1) for the 12 volatile organic compounds (VOCs). Global uncertainties were in the range of 4-68%, when concentrations decrease from 250 mu g L(-1) down to the limits of quantification. The method proved adequate to detect VOCs in six river samples.

Abstract  A series of laboratory scale batch slurry experiments were conducted in order to establish a data set for oxidant demand by sandy and clayey subsurface materials as well as to identify the reaction kinetic rates of permanganate (MnO(4)(-)) consumption and PCE oxidation as a function of the MnO(4)(-) concentration. The laboratory experiments were carried out with 31 sandy and clayey subsurface sediments from 12 Danish sites. The results show that the consumption of MnO(4)(-) by reaction with the sediment, termed the natural oxidant demand (NOD), is the primary reaction with regards to quantification of MnO(4)(-) consumption. Dissolved PCE in concentrations up to 100 mg/l in the sediments investigated is not a significant factor in the total MnO(4)(-) consumption. Consumption of MnO(4)(-) increases with an increasing initial MnO(4)(-) concentration. The sediment type is also important as NOD is (generally) higher in clayey than in sandy sediments for a given MnO(4)(-) concentration. For the different sediment types the typical NOD values are 0.5-2 g MnO(4)(-)/kg dry weight (dw) for glacial meltwater sand, 1-8 g MnO(4)(-)/kg dw for sandy till and 5-20 g MnO(4)(-)/kg dw for clayey till. The long term consumption of MnO(4)(-) and oxidation of PCE can not be described with a single rate constant, as the total MnO(4)(-) reduction is comprised of several different reactions with individual rates. During the initial hours of reaction, first order kinetics can be applied, where the short term first order rate constants for consumption of MnO(4)(-) and oxidation of PCE are 0.05-0.5 h(-1) and 0.5-4.5 h(-1), respectively. The sediment does not act as an instantaneous sink for MnO(4)(-). The consumption of MnO(4)(-) by reaction with the reactive species in the sediment is the result of several parallel reactions, during which the reaction between the contaminant and MnO(4)(-) also takes place. Hence, application of low MnO(4)(-) concentrations can cause partly oxidation of PCE, as the oxidant demand of the sediment does not need to be met fully before PCE is oxidised.

Abstract  The determination of vinyl acetate at parts per 10(9) by volume (ppbv) levels in air by gas chromatography/mass spectrometry (GC/MS) was achieved by optimizing the GC conditions and choosing specific extraction solvents that are sufficiently pure. The ideal solvent should not give rise to fragment ions at m/z 43, in order to rule out any possible interference during the monitoring of the same vinyl acetate ion. Traces of acetone and butan-2-one in solvents suitable for this GC/MS determination may also mislead the detection of vinyl acetate. A 440 mu l volume of a mixture of tetrachloroethylene containing 9% acetonitrile allowed the recovery of more than 90% of the ester with a detection limit of 1.5 ppbv in air together with a good linearity of response.