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Volatile organic compounds (VOCs) represent a broad class of chemicals, many of which can be found in indoor air including residential indoor air. VOCs derive from a variety of sources including cleaning products, cooking practices, fragrances and fresheners, hobbies and at-home work behaviors. This study examined residential indoor air in homes (n = 99) in southeast Louisiana using passive organic vapor monitors and gas chromatography/mass spectrometry to determine if select VOCs were present, at what concentrations, and if those posed any potential long-term health risks. Twenty-nine VOCs were targeted in cross-sectional analyses using a 48-h sampling period. Twelve VOCs were detected in most of the homes sampled including xylenes, pinenes, benzene, toluene, ethylbenzene, hexane, pentane, chloroform, and carbon tetrachloride. Concentrations of alkanes and BTEX compounds were highly correlated (Spearman's r > 0.63, p < 0.0001). Using health risk measures (i.e. reference concentrations [RfCs] and inhalation unit risks [IURs]) available from the USEPA non-cancer risk assessments and cancer risk assessments were developed for some of these VOCs. Alkanes and BTEX compounds likely come from the same indoor source(s). Using existing health standards published by the USEPA, no unacceptable non-cancer risks were evident except under extremely high concentrations. Lifetime cancer risks, on the other hand, may well be considered unacceptable for chloroform and benzene (upper IUR) and for the combination of chloroform, benzene, and carbon tetrachloride. These exceeded a 1 in 10,000 cancer risk threshold in 35–50% of our simulations. Further study of residential indoor air in low-income women's homes in this area is needed. Including a larger number of VOCs may reveal yet more potential health risks. [ABSTRACT FROM AUTHOR]

Background: Previous research shows that environmental and social factors contribute to the development of attention-deficit/hyperactivity disorder (ADHD).Objective: To determine the relationship between early-life exposure to common ambient air pollutants (benzene, toluene, ethylbenzene, and xylene, also known as BTEX), household material hardship (a measure of socio-economic status), and ADHD-suggestive behaviours in kindergarten-age children.Methods: Pollutant exposure estimated from the 2002 National Air Toxics Assessment at each child's residential ZIP code at enrolment was linked to the Early Childhood Longitudinal Study Birth Cohort (n = 4650). Material hardship was assigned as a composite score of access to food, health care, and housing. Kindergarten teachers rated children's behaviours and activity in the classroom using a five-point Likert scale. Children with summary scores in the bottom decile were classified as displaying ADHD-suggestive behaviours. Logistic regression models were constructed to estimate the association between both BTEX exposure and material hardship on ADHD-suggestive behaviours.Results: The odds of displaying ADHD-suggestive behaviours were greater in children with combined high-level exposure to BTEX and in those experiencing material hardship (odds ratio 1.54, 95% confidence interval [CI] 1.12, 2.11, and OR 2.12, 95% CI 1.25, 3.59, respectively), adjusting for covariates. These associations were stronger when restricting the study population to urban areas. There was no evidence of interaction between early life BTEX exposure and material hardship, although the effects of BTEX exposure were slightly greater in magnitude among those with higher material hardship scores.Conclusions: Children exposed to air toxics, material hardship, or both early in life are more likely to display signs of ADHD-suggestive behaviours as assessed by their kindergarten teachers. The associations between exposures to air pollution and to socio-economic hardship were observed in all children but were particularly strong in those living in urban areas. [ABSTRACT FROM AUTHOR]

Abstract This study characterized spatio-temporal variations in the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in the vicinity of gas and compressed natural gas (CNG) stations in Tehran, Iran. Health risk assessment (HRA) was computed using Monte Carlo simulations (MCS) for evaluating inhalation lifetime cancer risk (LTCR), the hazard quotient (HQ), and sensitivity analysis (SA) for BTEX exposure in different age groups (birth to <81) and as a function of distance (0–250 m) from the center of the stations. For all monitoring stations, the average values of benzene, toluene, ethylbenzene, and xylene in winter were 466.09 ± 132.25, 873.13 ± 233.51, 493.05 ± 141.22, and 910.57 ± 145.40 μg m−3, respectively. The mean wintertime ratios of T/B for the 12 stations ranged from 1.69 to 2.04. Furthermore, there was no significant relationship between the concentration of BTEX with either the specific month or distance from the center of stations (p > 0.05). Factors promoting BTEX formation in the study region were fuel evaporation and gas/CNG station emissions. The LTCRs for the target compounds in the winter for different age groups and distances from the center of stations was limited to 2.11 × 10−4 to 1.82 × 10−3 and 2.30 × 10−4 to 2.01 × 10−3, respectively, which exceeded proposed values by U.S. EPA. Moreover, the HQs for BTEX for three age groups and distances were limited to between 2.89 × 10−5 and 9.33 × 10−2, which were lower than the acceptable limit (HQs < 1). The results of this work are applicable to similar areas that are heavily populated with vehicular traffic. This study motivates a closer look at mitigation strategies to limit the health effects of carcinogenic emissions such as benzene and ethylbenzene from gas/CNG stations. Graphical abstract Image 1 Highlights • BTEX concentrations were measured in 12 gas/CNG stations in Tehran, Iran. • T:B ratios for the twelve stations ranged from 1.69 to 2.04. • BTEX levels not impacted by month or distance from the center of gas/CNG station. • LTCR for BTEX in different groups and distances ranged from 2.11 × 10−4 to 2.01 × 10−3. • HQ for BTEX in different groups and distances was less than the acceptable limit. This is the first such study investigating BTEX in this understudied, yet largely populated, region in the Middle East with attention geared towards spatial and diurnal trends, health effects of BTEX, and amount of BTEX emissions in gas stations versus CNG stations. [ABSTRACT FROM AUTHOR]

Abstract To develop a method to measure simultaneously the concentration of BTEX (benzene, toluene, ethylbenzene, m/p -xylene, o -xylene) in human whole blood with Purge and Trap-Gas Chromatography-Mass Spectrometry. The conditions of purge and trap were optimized, so that the BTEX in human whole blood could be enriched and desorbed, and then characteristic ions could be selected with gas chromatography–mass spectrometry combined with isotope internal standard for qualitative and quantitative analysis. After the parameters of purge and trap method were optimized, the BTEX in human whole blood could be simultaneously enriched, desorbed and measured accurately. The detection limit with this method ranges from 0.001 μg/L to 0.004 μg/L. The Linear range is from 0.021 μg/L to 10.99 μg/L. The recovery rate of low concentration (0.687 μg/L) solution is in the range of 79.21% to 85.92%; the recovery rate of high concentration (2.747 μg/L) solution is in the range of 93.21% to 102.07%. The analysis of the same sample is repeated for six times with its relative standard deviation ranging from 2.77% to 5.40%. With simple operation, short analysis period, good separation as well as required accuracy and precision, this method could analysis of BTEX concentration in human whole blood. Highlights • The purpose of this work was to provide a novel method for detecting BTEX concentration in human whole blood. [ABSTRACT FROM AUTHOR]

The source-receptor relationship of volatile organic compounds (VOCs) is an important environmental concern, particularly in large industrial cities; however, only a few studies have identified VOC sources using high spatial resolution data. In this study, 28 VOCs were monitored in Ulsan, the biggest multi-industrial city in Korea. Passive air samplers were seasonally deployed at eight urban and six industrial sites. The target compounds were detected at all sites. No significant seasonal variations of VOCs were observed probably due to the continuous emissions from major industrial facilities. Benzene, toluene, ethylbenzene, xylenes, and styrene accounted for 66-86% of the concentration of Σ28 VOCs. The spatial distribution of the individual VOCs clearly indicated that petrochemical, automobile, non-ferrous, and shipbuilding industries were major VOC sources. Seasonal wind patterns were found to play a role in the spatial distribution of VOCs. Diagnostic ratios also confirmed that the industrial complexes were the dominant VOC sources. The results of principal component analysis and correlation analyses identified the influence of specific compounds from each industrial complex on individual sites. To the best of our knowledge, this is the first comprehensive report on the seasonal distribution of VOCs with high spatial resolution in a metropolitan industrial city in Korea. [ABSTRACT FROM AUTHOR]

Abstract A geochemical conceptual model was developed to interpret long-term field monitoring data of the chemical speciation related to BTEX biodegradation in a tropical iron-rich aquifer that was contaminated by a large volume of jet fuel. Biodegradation under dissimilatory iron reduction is widely favored due to the abundance of iron oxides in the sediment. Concomitantly with iron-reduction, the methanogenesis pathway plays an important role in the microbial degradation of BTEX. The conceptual model was proposed to link the geochemical zonation with BTEX mineralization and secondary reactions. The representativeness of the chemical speciation of the studied hydrocarbon-contaminated aquifer is best supported when PCO 2 is fixed and dissolved oxygen, potentially present due to mass transfer from entrapped air, is considered in the model. These findings emphasize the need of both constraints to properly interpret BTEX biodegradation in a tropical iron-rich aquifer. Highlights • The PCO 2 plays an important role in the chemical speciation of contaminated groundwater. • The oxygen released from entrapped air bubble governs the redox state and oxidation of by-products in the LNAPL source zone. • Estimate of biodegraded BTEX mass based on by-products concentration in the source zone does not provide accurate result. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel catalytic process is developed to aromatize lignin under methane. • BTEX yield is enhanced when methane is present over 1%Zn-0.5%Ga/ZSM-5. • Methane incorporation into formed aromatics is evidenced through isotopic labelling. • Benzylic position and aromatic ring are the preferred methane incorporation sites. • Aromatization performance is closely associated with catalyst's physical properties. Abstract Maximizing the production of aromatic hydrocarbons from lignin conversion by coupling methane activation without solvent was investigated over Zn-Ga modified zeolite catalyst. The co-loading of Zn and Ga greatly improves lignin conversion, arene yield along with BTEX (i.e., benzene, toluene, ethylbenzene, and xylene) selectivity, which gives 37.4 wt% yield of aromatic hydrocarbons with 62.2 wt% selectivity towards BTEX at 400 °C and 3.0 MPa. Methane presence has a negligible impact on lignin conversion, but improves arene yield and BTEX selectivity. Liquid 13C, 1H and 2H NMR investigations confirm the incorporation of methane into the final arene products. The NMR results reveal that methane might be incorporated into both the methyl group and aromatic ring, possibly via methylation of aryl moieties and co-aromatization of alkyl moieties. Pyridine and ammonia as probes for surface acidity analysis of the developed catalysts demonstrate that HZSM5 modification with Zn and Ga species could redistribute BAS (Brønsted acid sites) and LAS (Lewis acid sites) and significantly increase the fraction of weak acidic sites on the catalyst, rendering better catalytic performance on the depolymerization of lignin to arene products with higher BTEX selectivity. The results reported in this work may open a novel route to a promising technique for lignin valorization into aromatics and cost-efficient utilizations of biomass and natural gas resources. [ABSTRACT FROM AUTHOR]

The results of the research in the field of benzene, toluene, ethylbenzene and xylene isomers (BTEX) concentrations in exhaust gases of spark ignition engines under different operating conditions are presented in this paper. The aim of this paper is to gain a clearer insight into the impact of different engine working parameters on the concentrations of BTEX. The experimental investigation has been performed on the SCHENCK 230 W test stand with the controlled IC engine. The engine operating points have been chosen based on the results of a simulation and they are considered as the typical driving conditions according to the New European Driving Cycle. Concentration levels of BTEX compounds in exhaust gas mixtures have been determined by gas chromatography technique by using the combination of Supelcowax 10-Polyethylene glycol column and the PID detector. Based on the experimental research results, the emission model of BTEX compounds has been defined by the simulation of movement of a Fiat Punto Classic passenger car in accordance with the NEDC cycle. Using the results obtained within the simulation, the official statistics on the number of gasoline-powered cars on the territory of the Republic of Serbia and the European Commission data on the annual distance traveled by car, the amounts of BTEX compounds emitted annually per car have been estimated, as well as the emissions of the entire Serbian car fleet. [ABSTRACT FROM AUTHOR]

This study aimed to assess the prediction efficiencies of response surface methodology (RSM) and artificial neural network (ANN)-based models in terms of benzene, toluene, ethylbenzene, and xylenes (BTEX) removal from a polluted airstream using non-thermal plasma (NTP). The effect that key elements of the NTP process, including temperature, BTEX concentration, voltage and flow rate, had on the BTEX elimination efficiency was investigated using a central composite RSM design along with three ANN models including Feed-Forward Back Propagation Neural Network (FFBPNN), Cascade-Forward Back Propagation Neural Network (CFBPNN) and Elman-Forward Back Propagation Neural Network (EFBPNN) with the topology of 4-h-1. The RSM and ANN models were statistically compared using some indicators including Sum of Squared Errors (SSE), adjusted R², determination coefficient (R²), Root Mean Squared Error (RMSE), Absolute Average Deviation (AAD). According to the RSM output, voltage was the most efficient variable with a coefficient proportion of 8.28. Besides, FFBPNN was the best model among the considered ANN models. Also, the R² achieved for ANN (FFBPNN) and RSM models were 0.9736 and 0.9656 correspondingly. Therefore, it was concluded that the ANN (FFBPNN) represents a powerful tool for modeling the BTEX removal. [ABSTRACT FROM AUTHOR]

The effect of different microaeration flow rates and dosing points, and of effluent recirculation, on microaerobic BTEX degradation in an anaerobic bioreactor was assessed. Additionally, a sensitivity and recovery analysis for this system was performed during microaeration failure simulations. Under anaerobic conditions, BTEX removal efficiencies between 55 and 82% were achieved depending on the compound, being benzene the most recalcitrant one. Microaeration (0.5–2.0 mL air min −1 ) ensured high removal efficiencies (>83%) for all compounds, and the best results were obtained for the flow rate of 1.0 mL air min −1 , particularly for benzene, with a 30% increase in its removal efficiency. Effluent recirculation showed to be an important factor to improve mass transfer and, consequently, BTEX removal. Volatilization was negligible even under microaerobic conditions, suggesting that microbial activity was the main removal mechanism. Finally, after microaeration shutdown periods, the bioreactor could recover its prior performance within up to 2 days. [ABSTRACT FROM AUTHOR]

In the aim of BTEX leakage emergency, monolithic carbon foam (MCF) was designed and prepared via a simple method. Rice husk char (RHC) was chosen as raw material, polyurethane sponge (PUS) was used as sacrificed template to form inner channel, and corn starch and ZnO were employed as binder and reinforcing filler, respectively. The optimized preparation parameter was determined by adopting of Taguchi experimental design method. Both MCF-RHC and MCF-CAC were made from RHC and commercial activated carbon (CAC) under the same condition, and three reported monolithic carbon adsorbents were selected for comparative study with MCFs. The surface and structural properties were characterized by XRD, SEM, and N2 adsorption/desorption isotherm analyses. XRD analysis results reveal that MCF-RHC was the composites of carbon, SiO2, and ZnO, and MCF-RHC and MCF-CAC have good potential in organic adsorption. Hierarchical structure of MCF was constructed by inner macro-channel from burning up of PUS and micro- and meso-pores from resultant carbon composite, and these inner macro-channels play a more important role in benzene rapid adsorption. Specific surface area of MCF-RHC was 465.5 m2 g−1, which included micro- and meso-pores, which mainly come from RHC during the carbonization process. Adsorption kinetics study demonstrated that the benzene equilibrium uptake of MCF-RHC and MCF-CAC was similar, and both of data well fitted the pseudo-second-order kinetic model. However, MCF-RHC has the ability to absorb benzene more quickly, which meets the demand of absorbent utilizing in benzene leakage emergency. [ABSTRACT FROM AUTHOR]

Concerns about the environmental impact of shale energy exploration (i.e., hydraulic fracturing and other well stimulation techniques) have risen due to its rapid expansion in the United States and other countries. Soils in shale basins engaged in unconventional oil and gas development can become contaminated by volatile organic compounds (VOCs), such as benzene, toluene, ethylbenzene, and xylenes (BTEX) through mishandling of chemical additives, products, and/or waste fluids. In this study, room temperature ionic liquids (RTILs) were evaluated as solvents in an effort to increase sensitivity and to reduce and normalize matrix effects associated with varying soil compositions during analysis. Headspace gas chromatography mass spectrometry (HS-GC-MS) experiments demonstrated that hydrophilic RTILs 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][ESO 4 ], 1-ethyl-3-methylimidazolium diethyl phosphate [EMIM][DEP], and tris(2-hydroxyethyl) methylammonium methylsulfate [MTEOA][MeOSO 3 ] normalized the response for BTEX compounds between 2 different soils, sandy loam and sandy clay loam. Furthermore, the optimization of the HS equilibration time to 30 min resulted in the reduction of matrix effects in certified reference soils of sand, clay, and loam textures. Limits of detection and limits of quantification were in the sub- to mid- pg g −1 level in soil. For determination at 1 g of certified BTEX reference soil, the relative standard deviation was within 10% and percent recoveries were above 80% for toluene, ethylbenzene, and xylenes. This method reduces the need to characterize and matrix-match soil texture for calibration purposes. It also reduces the analysis time and increases precision and accuracy for the quantification of BTEX in variable soil matrices relative to standard methods. [ABSTRACT FROM AUTHOR]

Urinary benzene, toluene, ethylbenzene, and xylenes (BTEX) can be used as a reliable biomarker of exposure to these pollutants. This study was aimed to investigate the urinary BTEX concentration in operators of healthcare waste (HCW) autoclaves. This cross-sectional study was conducted in selected hospitals in Tehran, Iran between April and June 2017. Twenty operators (as the case group) and twenty control subjects were enrolled in the study. Personal urine samples were collected at the beginning and end of the work shift. Urinary BTEX were measured by a headspace gas chromatography-mass spectrometry (GC/MS). A detailed questionnaire was used to gather information from subjects. Results showed that the median of urinary benzene, toluene, ethylbenzene, m-p xylene, and o-xylene levels in the exposed group were 3.26, 3.36, 0.84, 3.94 and 4.48 μg/L, respectively. With the exception of ethylbenzene, subjects in the exposed group had significantly higher urinary BTEX levels than control group ( p  < 0.05). Urinary BTEX concentrations in the exposed case group were 2.5-fold higher than in the control group. There was a significant relationship between the amount of generated waste per day and the urinary BTEX in the exposed group. Smoking status and type of autoclave used were also identified as predictors of urinary BTEX concentrations. The healthcare waste treatment autoclaves can be considered as a significant BTEX exposure source for operators working with these treatment facilities. The appropriate personal protection equipment and control measures capable in reducing BTEX exposure should be provided to HCW workers to reduce their exposures to BTEX. [ABSTRACT FROM AUTHOR]

Although the Atoyac River has been classified as highly polluted by environmental authorities, several communities are settled on its banks, affecting around 1.5 million persons, as well as farmland, due to an environmental distribution of toxics in the area. Our aim was to demonstrate that this environment affects important physiological processes that have an impact in health, so we conducted a study of schoolchildren from small communities on the banks of the river and in another similar town located far from it. 91 and 93 students, boys and girls, were studied from each site for oxidative stress index (OSI), calculated from the total antioxidant capacity and the total oxidative status, BTEX metabolite excretion and relevant metabolic polymorphisms participating in the bioactivation‐detoxification of most VOC: CYP2E1 RsaI, NQO1 C609T, and null polymorphisms of GSTT1 and GSTM1. Results showed that OSI was significantly higher in children living by the river (5.23 ± 3.4 vs 2.59 ± 1.46, 95% C.I.). At this site, OSI was correlated with diminished metabolite excretion and a diminished antioxidant capacity; an association with genotypes CYP2E1RsaI (c2c2), GSTT1 present and NQO1*2 (CC) was also observed. Furthermore, boys at this site exhibited a diminished BMI compared to boys from the other community who were younger. In conclusion: children living at polluted sites like this, show early biological effects that might lead to health problems in their adult life. Environmental protection should be enforced to protect people's health in these sites where not even environmental monitoring is done. Environ. Mol. Mutagen. 59:639–652, 2018. © 2018 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Solid or sludgy hydrocarbon waste is a by-product of oil and gas exploration and production. One commonly used method of disposing of this waste is landfarming. Landfarming involves spreading hydrocarbon waste on soils, tilling it into the soil, and allowing it to biodegrade. We used a dynamic flux chamber to measure fluxes of methane, a suite of 54 nonmethane hydrocarbons, and light alcohols from an active and a remediated landfarm in eastern Utah. Fluxes from the remediated landfarm were not different from a polytetrafluoroethylene (PTFE) sheet or from undisturbed soils in the region. Fluxes of methane, total nonmethane hydrocarbons, and alcohols from the landfarm in active use were 1.41 (0.37, 4.19) (mean and 95% confidence limits), 197.90 (114.72, 370.46), and 4.17 (0.03, 15.89) mg m−2 hr−1, respectively. Hydrocarbon fluxes were dominated by alkanes, especially those with six or more carbons. A 2-ha landfarm with fluxes of the magnitude we observed in this study would emit 95.3 (54.3, 179.7) kg day−1 of total hydrocarbons, including 11.2 (4.3, 33.9) kg day−1 of BTEX (benzene, toluene, ethylbenzene, and xylenes). Implications: Solid and sludgy hydrocarbon waste from the oil and gas industry is often disposed of by landfarming, in which wastes are tilled into soil and allowed to decompose. We show that a land farm in Utah emitted a variety of organic compounds into the atmosphere, including hazardous air pollutants and compounds that form ozone. We calculate that a 2-ha landfarm facility would emit 95.0 ± 66.0 kg day−1 of total hydrocarbons, including 11.1 ± 1.5 kg day−1 of BTEX (benzene, toluene, ethylbenzene, and xylenes). [ABSTRACT FROM AUTHOR]

Multi-storey parking structures have potentially high concentrations of benzene (B), toluene (T), ethylbenzene (E) and xylene (X) – known as BTEX which could cause adverse health effects to humans. This study sought to estimate BTEX exposure concentrations among car park workers and to evaluate the extent to which, if at all, changes in urine metabolites are associated with BTEX exposure. Personal BTEX samples were collected from workers. Pre-shift and post-shift urinary metabolites, trans,trans-muconic acid (t,t-MA), hippuric acid (HA) and methyl hippuric acid were assessed using standard procedures. Linear regression models were used to examine associations between BTEX exposure concentrations and changes in urinary metabolites. BTEX concentrations in the car park on Sunday were lower than other days of the week, for instance median concentrations of toluene were 23.3 µg/m3 on Sunday and 48.3 µg/m3 during average weekdays (Tuesday–Friday). Benzene and toluene concentrations adjusted for day of week differences were associated with changes from pre-shift to post-shift in urine t,t-MA and HA, respectively. Car park workers were more likely to be exposed to lower concentrations of BTEX during weekdays compared to weekends. Provision of personal chemical safety protection and rigorous evaluation of its effectiveness in reducing BTEX exposure should be provided to protect workers of car parks. [ABSTRACT FROM AUTHOR]

This paper presents a numerical model to investigate the migration of BTEX (benzene, toluene, ethylbenzene, and xylene) within a fractured aquifer system at the scale of a single fracture under the coupled effect of various transport processes such as dissolution, sorption, biodegradation. The developed model also considers the influence of equilibrium- and kinetic-controlled sorption scenarios on BTEX transport. Further, the transport characteristics of dissolved BTEX within the fracture-matrix system (FMS) are obtained by carrying out the spatial moment analysis on the concentration profiles simulated. In this study, the spatial moment analysis is conducted to estimate the following transport characteristics of dissolved BTEX: (a) velocity within the fracture, (b) dispersion coefficient within the fracture, (c) dissolved mass within the matrix. In order to investigate the sensitivity of various input parameters, two sensitivity indices are computed based on the variation in the velocity of dissolved BTEX constituent within the fracture (SI_vel) and on the variation in the dissolved mass of BTEX constituents within the matrix (SI_mat). Results from the present simulation study suggest that the sorption and biodegradation reactions influence the concentration distribution of highly soluble BTEX constituents (benzene, toluene) within the FMS significantly. The influence of biodegradation on the migration of BTEX within the FMS is found to be more when it co-occurs with the sorption reaction. The effect of sorption and biodegradation reactions on the mobility and dispersion coefficient of dissolved BTEX constituents within the FMS is found to be significant during the early simulation period. [ABSTRACT FROM AUTHOR]

The purpose of this study was to measure the concentration of carbon black and BTEXs at three photocopy centers and to assess the health risk following exposure. Air samples were collected by sampling in the breathing zone of workers during the class and examination periods. The results found that the concentration of carbon black before operation was higher than morning and afternoon in both class and examination periods. These levels are considerably lower than the suggested limited value set by OSHA. Toluene had the highest concentration but did not exceed of recommended exposure limit by NIOSH. The carbon black and toluene concentrations were higher in examination period than during the normal class period. The results from interview indicate that cough and sneeze are the highest symptom among workers. Carbon black and toluene concentrations in photocopy centers should be concerned in terms of indoor air quality and human health. [ABSTRACT FROM AUTHOR]

Gasohol blend spills with variable ethanol content exert different electron acceptor demands in groundwater and the distinct dynamics undergone by these blends underscores the need for field-based information to aid decision-making on suitable remediation technologies for each gasohol blend spill. In this study, a comparison of two gasohol releases (E10 (10:90 ethanol and gasoline, v/v) and E25 (25:75 ethanol and gasoline, v/v) under monitored natural attenuation (MNA) and nitrate biostimulation, respectively) was conducted to assess the most effective remediation strategy for each gasohol release. Microbial communities were assessed to support geochemical data as well as to enable the characterization of important population shifts that evolve during biodegradation processes in E25 and E10 field experiments. Results revealed that natural attenuation processes sufficiently supported ethanol and BTEX compounds biodegradation in E10 release, due to the lower biochemical oxygen demand they exert relative to E25 blend. In E25 release, nitrate reduction was largely responsible for BTEX and ethanol biodegradation, as intended. First-order decay constants demonstrated that ethanol degradation rates were similar (p < 0.05) for both remediation technologies (2.05 ± 0.15 and 2.22 ± 0.23, for E25 and E10, respectively) whilst BTEX compounds exhibited different degradation rates (p > 0.05) that were higher for the experiment under MNA (0.33 ± 0.06 and 0.43 ± 0.03, for E25 and E10, respectively). Therefore, ethanol content in different gasohol blends can influence the decision-making on the most suitable remediation technology, as MNA processes can be applied for the remediation of gasohol blends with lower ethanol content (i.e., 10% v/v), once the aquifer geochemical conditions provide a sufficient electron acceptor pool. To the best of our knowledge, this is the first field study to monitor two long-term gasohol releases over various time scales in order to assess feasible remediation technologies for each scenario. [ABSTRACT FROM AUTHOR]

Volatile Organic Compounds are a cause of concern for human health. It is particularly the case for BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylenes). Gravimetric sensors are good candidates for their detection but they have to be functionalized by a sensitive film to become active. In this work, organosilicate thin films (SiOCH) deposited by plasma enhanced chemical vapor deposition are investigated. This work aims at understanding the role of their chemical composition on gas adsorption and to propose an optimized material for BTEX detection. Through the synthesis and characterization of various SiOCH thin films, the role of hydrophobicity, carbon content and specific chemical bonding is highlighted. This led to an optimized film presenting both high affinity (partition coefficient toward toluene higher than 15000) and rapid temporal response. [ABSTRACT FROM AUTHOR]

To take advantage of the road pavement network where non-point source (NPS) pollution such as benzene, toluene, ethyl-benzene, and xylene (BTEX) from vehicle traffic exhaust via wet and dry atmospheric deposition occurs, the asphalt pavement may be used as a media to control the NPS pollution. An experiment to prepare an adsorptive porous reactive pavement (PRP) was initiated to explore the potential to reduce environmental NPS vehicle pollution. The PRP was prepared and studied as follows: various activated carbons (AC) were initially screened to determine if they were suitable as an additive in the porous asphalt mixture; various mixtures of a selected AC were incorporated with the design of porous asphalt concrete (PAC) to produce PRP, and the PRP formulations were tested to ensure that they comply with the required specifications; qualified specimens were subsequently tested to determine their adsorption capacity for BTEX in aqueous solution, as compared to conventional PAC. The PRP08 and PRP16 samples, named for the design formulations of 0.8% and 1.6% of AC (by wt. in the formulation), exhibited low asphalt drain-down and low abrasion loss and also met all regulated specifications. The BTEX adsorption capacity measurements of PRP08 and PRP16 were 33–46%, 36–51%, 20–22%, and 6–8% respectively, higher than those obtained from PACs. Based on the test results, PRPs showed good physical performance and adsorption and may be considered as a potential method for controlling the transport of NPS vehicle pollutants. [ABSTRACT FROM AUTHOR]

BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylenes) are toxic hydrocarbons that can be found in groundwater due to accidental spills. Bioelectrochemical systems (BES) are an innovative technology to stimulate the anaerobic degradation of hydrocarbons. In this work, single chamber BESs were used to assess the degradation of a BTEX mixture at different applied voltages (0.8 V, 1.0 V, 1.2 V) between the electrodes. Hydrocarbon degradation was linked to current production and to sulfate reduction, at all the tested potentials. The highest current densities (about 200 mA/m 2 with a maximum peak at 480 mA/m 2 ) were observed when 0.8 V were applied. The application of an external voltage increased the removal of toluene, m -xylene and p -xylene. The highest removal rate constants at 0.8 V were: 0.4 ± 0.1 days −1 , 0.34 ± 0.09 days −1 and 0.16 ± 0.02 days −1 , respectively. At the end of the experiment, the microbial communities were characterized by high throughput sequencing of the 16S rRNA gene. Microorganisms belonging to the families Desulfobulbaceae , Desulfuromonadaceae and Geobacteraceae were enriched on the anodes suggesting that both direct electron transfer and sulfur cycling occurred. The cathodic communities were dominated by the family Desulfomicrobiaceae that may be involved in hydrogen production. [ABSTRACT FROM AUTHOR]

The present study investigated the impacts of water matrix constituents (CO 3 2− , HCO 3 − , Cl − , Br − , PO 4 3− , HPO 4 2− , H 2 PO 4 − , NO 3 − , SO 4 2− and natural organic matters (NOM) on the oxidation of a mixture of benzene, toluene, ethylbenzene, and xylenes (BTEX) by thermally activated persulfate (PS). In the absence of matrix constituents, the BTEX oxidation rates decreased in the following order: xylenes > toluene ≈ ethylbenzene > benzene. HCO 3 − /CO 3 2− and NOM inhibited the BTEX oxidation and the inhibiting effects became more pronounced as the HCO 3 − /CO 3 2− /NOM concentration increased. SO 4 2− , NO 3 − , PO 4 3− and H 2 PO 4 − did not affect the BTEX oxidation while HPO 4 2− slightly inhibited the reaction. The impacts of Cl − and Br − were complex. Cl − inhibited the benzene oxidation while 100 mM and 500 mM of Cl − promoted the oxidation of m-xylene and p-xylene. Br − completely suppressed the benzene oxidation while 500 mM of Br − strongly promoted the oxidation of xylenes. Detailed explanations on the influence of each matrix constituent were discussed. In addition, various halogenated degradation byproducts were detected in the treatments containing Cl − and Br − . Overall, this study indicates that some matrix constituents such as NOM, HCO 3 − , CO 3 2− , H 2 PO 4 − , Cl − and Br − may reduce the BTEX removal efficiency of sulfate radical-based advanced oxidation process (SR-AOP) and the presence of Cl − and Br − may even lead to the formation of toxic halogenated byproducts. [ABSTRACT FROM AUTHOR]

Both a low concentration of dissolved oxygen and the toxicity of a high concentration of BTEX inhibit the bioremediation of BTEX in groundwater. A novel method of preparing encapsulated oxygen-releasing beads (encap-ORBs) for the biodegradation of BTEX in groundwater was developed. Experimental results show that the integrality and oxygen-releasing capacity of encap-ORBs exceeded those of ORBs. The use of polyvinyl alcohol (PVA) with high M.W. to prepare encap-ORBs improved their integrality. The encap-ORBs effectively released oxygen for 128 days. High concentration of BTEX (480 mg L −1 ) inhibited the biodegradation by the free cells. Immobilization of degraders in the encap-ORB alleviated the inhibition. Scanning electron microscope analysis reveals that the BTEX degraders grew on the surface of encap-ORB after bioremediation. The above results indicate that the encap-ORBs were effective in the bioremediation of BTEX at high concentration in groundwater. [ABSTRACT FROM AUTHOR]

The contribution of atmospheric precipitation to volatile organic compound (VOC) removal from the atmosphere remains a matter of scientific debate. The aim of this study was to examine the potential of rainwater for benzene, toluene, ethylbenzene and xylene (BTEX) scavenging from ambient air. To that end, air and rainwater samples were collected simultaneously during several rain events that occurred over two distinct time periods in the summer and autumn of 2015. BTEX concentrations in the gaseous and aqueous phases were determined using proton transfer reaction mass spectrometry. The results reveal that the registered amounts of BTEX in rainwater samples were higher than those predicted by Henry's law. Additional analysis, including physico-chemical characterization and source apportionment, was performed and a possible mechanism underlying the BTEX adsorption to the aqueous phase was considered and discussed herein. Finally, regression multivariate methods (MVA) were successfully applied (with relative errors from 20%) to examine the functional dependency of BTEX enrichment factor on gaseous concentrations, physico-chemical properties of rainwater and meteorological parameters. [ABSTRACT FROM AUTHOR]

The widespread use of unconventional drilling involving hydraulic fracturing ('fracking') has allowed for increased oil-and-gas extraction, produced water generation, and subsequent spills of produced water in Colorado and elsewhere. Produced water contains BTEX (benzene, toluene, ethylbenzene, xylene) and naphthalene, all of which are known to induce varying levels of toxicity upon exposure. When spilled, these contaminants can migrate through the soil and contaminant groundwater. This research modeled the solute transport of BTEX and naphthalene for a range of spill sizes on contrasting soils overlying groundwater at different depths. The results showed that benzene and toluene were expected to reach human health relevant concentration in groundwater because of their high concentrations in produced water, relatively low solid/liquid partition coefficient and low EPA drinking water limits for these contaminants. Peak groundwater concentrations were higher and were reached more rapidly in coarser textured soil. Risk categories of 'low,' 'medium,' and 'high' were established by dividing the EPA drinking water limit for each contaminant into sequential thirds and modeled scenarios were classified into such categories. A quick reference guide was created that allows the user to input specific variables about an area of interest to evaluate that site's risk of groundwater contamination in the event of a produced water spill. A large fraction of produced water spills occur at hydraulic-fracturing well pads; thus, the results of this research suggest that the surface area selected for a hydraulic-fracturing site should exclude or require extra precaution when considering areas with shallow aquifers and coarsely textured soils. [ABSTRACT FROM AUTHOR]

In this study, a non-pathogenic, BTEX-degrading Microbacterium esteraromaticum SBS1-7 was isolated from estuarine sediment in Thailand via an enrichment technique. M. esteraromaticum SBS1-7 was able to degrade all six BTEX components, in both liquid medium and soil slurry system, when BTEX was supplied as an individual component or a mixture. It exhibited a high level of tolerance towards a wide range of hydrocarbons and also utilized alkanes and naphthalene. Detection of metabolites produced during BTEX and naphthalene degradation revealed highly extensive biodegradation pathways used by M. esteraromaticum SBS1-7. Toluene was metabolized via activities of both monooxygenase (toluene 4-monooxygenase or T4MO) and dioxygenases (toluene dioxygenase or TDO and naphthalene 1,2-dioxygenase or NDO). Benzene was metabolized via phenol, possibly by an activity of T4MO. Ethylbenzene was converted into styrene and 1-phenethyl alcohol by a well-documented activity of NDO. Dioxidation of ethylbenzene, possibly by ethylbenzene dioxygenase or EBDO, was also found. All xylene isomers were converted into their corresponding alcohols via an activity of NDO while naphthalene was metabolized via dioxidation reaction by the same enzyme. This study is, by far, the first direct evidence of BTEX biodegradation by a non-pathogenic, rhizosphere bacterium M. esteraromaticum . [ABSTRACT FROM AUTHOR]

Groundwater contamination by organic aromatic compounds such as gasoline fuel is a serious worldwide problem because of their carcinogenic and mutagenic potential. This study evaluated the use of Fe 3 O 4 − carbon black (CB) composites for persulfate (PS) oxidation of benzene, toluene, ethylene, and xylene (BTEX) and methyl tert -butyl ether (MTBE) compounds from the aqueous solution. The characterization results of environmental scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and a superconducting quantum interference device magnetometry evidenced the successful synthesis of Fe 3 O 4 − CB composites. In addition, the in vitro cytotoxic activity and apoptotic response of these composites were investigated before and after the Fe 3 O 4 −CB/PS processes test of the BTEX and MTBE samples was performed. The effects of various operating parameters were evaluated to optimize the oxidation process, including the PS concentration, initial pH, and Fe 3 O 4 − CB amount. The results showed that increasing PS and Fe 3 O 4 − CB dosage could accelerate BTEX and MTBE oxidation when PS and Fe 3 O 4 − CB concentrations increased to 15 g L −1 and 1.0 g L −1 , respectively, at a pH of 3.0. The degradation rate of BTEX and MTBE was strongly pH-dependent. Methyl thiazolyl tetrazolium assay was employed to perform a cytotoxicity study after Fe 3 O 4 −CB/PS processing treatment of BTEX and MTBE degradation products on the zebrafish ( Danio rerio ) embryonic cell line (ZF4), which revealed that a weak effect and apoptosis in cell viability ultimately leads to cell death. The results suggested that Fe 3 O 4 −CB assisted persulfate oxidation without elevating the temperature is a suitable and economic alternative for the ex-situ treatment of BTEX- and MTBE-contaminated aquatic environments. [ABSTRACT FROM AUTHOR]

BTEX (benzene, toluene, ethylbenzene and xylene) compounds are common water resource and potable water pollutants that are often left undetected and untreated by municipal treatment systems in spite of the negative repercussions associated with their ingestion. The US EPA has classified these pollutants as priority pollutant, yet they are persistently present in a variety of water resources. In this review paper, we highlight the sources and reported concentrations of BTEX compounds in water and explore historical remediation techniques that have been applied such as bioremediation and natural attenuation. We also highlight emerging possibilities and future directions for remediation techniques, such as nanotechnology-based materials and novel green materials (tannins) that can be applied to ensure removal of these compounds in water. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate benzene, toluene, ethylbenzene, and xylene (BTEX) exposure among workers at four stations of a major oil distribution company. Personal BTEX exposure samples were collected over working shift (8 h) for 50 workers at four stations of a major oil distribution company in Iran. Measured mean values for workers across four sites were benzene (2437, 992, 584, and 2788 μg/m 3 respectively), toluene (4415, 2830, 1289, and 9407 μg/m 3 ), ethylbenzene (781, 522, 187, and 533 μg/m 3 ), and xylene (1134, 678, 322, and 525 μg/m 3 ). The maximum mean concentration measured across sites for benzene was 2788 μg/m 3 (Station 4), toluene was 9407 μg/m 3 (Station 4), ethylbenzene was 781 μg/m 3 (Station 1) and xylene was 1134 μg/m 3 (Station 1). The 8 h averaged personal exposure benzene concentration exceeded the recommended value of 1600 μg/m 3 established by the Iranian Committee for Review and Collection of Occupational Exposure Limit and American Conference of Governmental Industrial Hygienists. Mean values for excess lifetime cancer risk for exposure to benzene were then calculated across workers at each site. Estimates of excess risk ranged from 1.74 ± 4.05 (Station 4) to 8.31 ± 25.81 (Station 3). Risk was assessed by calculation of hazard quotients and hazard indexes, which indicated that xylene and particularly benzene were the strongest contributors. Tanker loading was the highest risk occupation at these facilties. Risk management approaches to reducing exposures to BTEX compounds, especially benzene, will be important to the health of workers in Iran. [ABSTRACT FROM AUTHOR]

The effect of dissolved organic matter (DOM) and oil on the removal of the water-soluble compounds benzene, toluene, ethylbenzene, and xylene isomers (BTEX) by two low-cost biosorbents Macrocystis pyrifera and Ulva expansa) was evaluated. DOM decreased the adsorption capacity of toluene, ethylbenzene, and xylenes of the two biosorbents. In contrast, the removal of benzene increased under the same conditions in single and multi-solute systems: this effect was dominant in U. expansa biomass treatments. In the presence of DOM and oil in solutions, the removal of BTEX notoriously increased, being oil that contributed the most. Solubility and hydrophobicity of pollutants played a key role in the adsorption process. The attractions between BTEX molecules and biosorbents were governed by π-π and hydrophobic interactions. Affinities of biosorbents for BTEX were mainly in the order of X > E > T > B. The Langmuir and Sips equations adjusted the adsorption isotherms for BTEX biosorption in deionized and natural water samples, but in the case of oily systems, the Freundlich equation seemed to have a better fit. The biosorption processes followed a pseudo-second-order rate in all the cases. [ABSTRACT FROM AUTHOR]

There is a growing concern over the contamination of surface water and the associated environmental and public health consequences from the recent proliferation of hydraulic fracturing in the USA. Petroleum hydrocarbon-derived contaminants of concern [benzene, toluene, ethylbenzene, and xylenes (BTEX)] and various dissolved cations and anions were spatially determined in surface waters around 15 coalbed methane fracking wells in Sullivan County, IN, USA. At least one BTEX compound was detected in 69% of sampling sites (n = 13) and 23% of sampling sites were found to be contaminated with all of the BTEX compounds. Toluene was the most common BTEX compound detected across all sampling sites, both upstream and downstream from coalbed methane fracking wells. The average concentration of toluene at a reservoir and its outlet nearby the fracking wells was ~2× higher than other downstream sites. However, one of the upstream sites was found to be contaminated with BTEX at similar concentrations as in a reservoir site nearby the fracking well. Calcium (~60 ppm) and sulfates (~175 ppm) were the dominant cations and anions, respectively, in surface water around the fracking sites. This study represents the first report of BTEX contamination in surface water from coalbed methane hydraulic fracturing wells. [ABSTRACT FROM AUTHOR]

Conversions of benzoates in orange and apple juices affected by thermal processing (100C for 10 min) were investigated. The instrumental determination was carried out by gas chromatography-mass spectrometry (GC-MS) using a direct injection of samples (5 µl) into the column. The products of benzoic acid reduction, but no benzene, were found in all samples. New scientific evidence indicating the presence of threshold amounts of toluene and benzyl alcohol in orange juice containing benzoates were demonstrated. Benzoic acid, threshold amount of benzyl alcohol, but no toluene, was detected in apple juice. Volt-amperometric assessment showed that reducing ability of redox systems was the main factor determining differences in results obtained for orange and apple juices in respect of the products of benzoic acid conversions. The effect of ascorbic acid on benzyl alcohol and toluene formation from benzoates was investigated using the model system (5% solution of ascorbic acid and sodium benzoate). Practical Applications The scientific knowledge could provide the possibility to control the toxic substance formation in fruit products containing benzoates. This field of study is especially important for establishing a scientific base for fruit products manufactured in accordance with HACCP regulations. The article is important for food producers and scientists who are working in the area of canned fruit products. The article content will improve the concepts of using additives and will improve the theory of chemical safety of canned foodstuffs. [ABSTRACT FROM AUTHOR]

The spatiotemporal variability of ambient volatile organic compounds (VOCs) in Tehran, Iran, is not well understood. Here we present the design, methods, and results of the Tehran Study of Exposure Prediction for Environmental Health Research (Tehran SEPEHR) on ambient concentrations of benzene, toluene, ethylbenzene, p -xylene, m -xylene, o -xylene (BTEX), and total BTEX. To date, this is the largest study of its kind in a low- and middle-income country and one of the largest globally. We measured BTEX concentrations at five reference sites and 174 distributed sites identified by a cluster analytic method. Samples were taken over 25 consecutive 2-weeks at five reference sites (to be used for temporal adjustments) and over three 2-week campaigns in summer, winter, and spring at 174 distributed sites. The annual median (25 th –75 th percentile) for benzene, the most carcinogenic of the BTEX species, was 7.8 (6.3–9.9) μg/m 3 , and was higher than the national and European Union air quality standard of 5 μg/m 3 at approximately 90% of the measured sites. The estimated annual mean concentrations of BTEX were spatially highly correlated for all pollutants (Spearman rank coefficient 0.81–0.98). In general, concentrations and spatial variability were highest during the summer months, most likely due to fuel evaporation in hot weather. The annual median of benzene and total BTEX across the 35 sites in the Tehran regulatory monitoring network (7.7 and 56.8 μg/m 3 , respectively) did a reasonable job of approximating the additional 144 city-wide sites (7.9 and 58.7 μg/m 3 , respectively). The annual median concentrations of benzene and total BTEX within 300 m of gas stations were 9.1 and 67.3 μg/m 3 , respectively, and were higher than sites outside this buffer. We further found that airport did not affect annual BTEX concentrations of sites within 1 km. Overall, the observed ambient concentrations of toxic VOCs are a public health concern in Tehran. [ABSTRACT FROM AUTHOR]

Emissions of BTEX (benzene, toluene, ethylbenzene and xylene) from the petrochemical industry are characterized by a low pollutants concentration and the absence of oxygen. Biodegradation of these pollutants using nitrate as the electron acceptor is of key interest to reuse the residual gas for inertization purposes. However, the biological mineralization of BTEX is often limited by their recalcitrant nature and the toxicity of the secondary metabolites produced. The potential of an anoxic biotrickling filter for the treatment of a model O 2 -free BTEX-laden emission at inlet individual concentrations of ~ 700 mg m − 3 was here evaluated. A UV oxidation step was also tested both in the recycling liquid and in the inlet gas emission prior to biofiltration. Removal efficiencies > 90% were achieved for both toluene and ethylbenzene, corresponding to elimination capacities (ECs) of 1.4 ± 0.2 g m − 3 h − 1 and 1.5 ± 0.3 g m − 3 h − 1 , respectively, while ~ 45% of xylene (EC = 0.6 ± 0.1 g m − 3 h − 1 ) was removed at a liquid recycling rate of 2 m h − 1 . Benzene biodegradation was however limited by the accumulation of toxic metabolites in the liquid phase. The oxidation of these intermediates in the recycling liquid by UV photolysis boosted benzene abatement, achieving an average EC of 0.5 ± 0.2 g m − 3 h − 1 and removals of ~ 40%. However, the implementation of UV oxidation as a pretreatment step in the inlet gas emission resulted in the deterioration of the BTEX biodegradation capacity of the biotrickling filter. Finally, a high bacterial diversity was observed throughout the entire experiment, the predominant phyla being Proteobacteria and Deinococcus-thermus . [ABSTRACT FROM AUTHOR]

BTEX are known for their ability to deteriorate human health. A monitoring study was conducted at Gorakhpur, for a span of one year. BTEX were sampled by drawing air through activated charcoal tubes, using a low flow SKC model 220 pump. Samples were extracted with CS 2 followed by subjecting the aromatic fraction to GC-FID. The mean concentration of BTEX was highest at agricultural (54.3 μg m −3 ) followed by industrial (18.2 μg m −3 ), roadside (12.3 μg m −3 ) and residential site (6.1 μg m −3 ). Toluene levels were higher than benzene at all the sites except agricultural site, where benzene concentration exceeded toluene. Seasonal variation showed highest BTEX concentration during winters (32.56 μg m −3 ) followed by monsoon (19.90 μg m −3 ) and summers (14.44 μg m −3 ). At each site, BTEX levels increased with decrease in temperature. Benzene and toluene levels were plotted against indoor temperature, which revealed a significant linear correlation (p < 0.001) for each plot. BTEX concentrations were compared between different sites using Student’s t and Mann Whitney U tests. Value of integrated lifetime cancer risk (ILTCR) was higher than 10 −6 for benzene at all the sites, while for ethylbenzene, it was only higher at agricultural site. Cumulative hazard index (HI) was lower than 1.0 at all the sites. [ABSTRACT FROM AUTHOR]

Gas stations constitute important point sources of soil and groundwater pollution. The leaking of hydrocarbons into the soil is a significant environment issue due to the wide-ranging occurrence of leaks and the high levels and toxicity of pollutants involved in the contamination of groundwater for human use. This study introduces a compact system developed to treat groundwater contaminated with benzene, toluene, ethyl benzene, and xylenes (BTEX) and total petroleum hydrocarbon (TPH) leaked from gas station tanks. The system comprises three units: (1) suction and volatilization of volatile organic compounds (VOCs), (2) aeration tank (to remove volatile organic substances), and (3) an adsorption packed-bed filter (activated carbon (AC) and rice husk ash, 50% each, to remove TPH). Contaminated groundwater was characterized in a pilot study and in the field. Levels of BTEX and of TPH decreased by 96% with an 8-h retention time. The results obtained show that the remediation system is highly efficient and yielded water that met the discharge standards defined in the Brazilian legislation, that is, maximum benzene, toluene, and xylene levels of 5, 170, and 300 μg/L, respectively. [ABSTRACT FROM PUBLISHER]

Sulfate reducing conditions are widely observed in groundwater plumes associated with petroleum hydrocarbon releases. This leads to sulfate depletion in groundwater which can limit biodegradation of hydrocarbons (usually benzene, toluene, ethylbenzene, xylenes [ BTEX] compounds) and can therefore result in extended timeframes to achieve groundwater cleanup objectives by monitored natural attenuation. Under these conditions, sulfate addition to the subsurface can potentially enhance BTEX biodegradation and facilitate enhanced natural attenuation. However, a delivery approach that enables effective contact with the hydrocarbons and is able to sustain elevated and uniform sulfate concentrations in groundwater remains a key challenge. In this case study, sulfate addition to a groundwater plume containing predominantly benzene by land application of agricultural gypsum and Epsom salt is described. Over 4 years of groundwater monitoring data from key wells subjected to pilot-scale and site-wide land application events are presented. These are compared to data from pilot testing employing liquid Epsom salt injections as an alternate sulfate delivery approach. Sulfate land application, sulfate retention within the vadose zone, and periodic infiltration following ongoing precipitation events resulted in elevated sulfate concentrations (>150 mg/L) in groundwater that were sustained over 12 months between application events and stimulated benzene biodegradation as indicated by declines in dissolved benzene concentration, and compound-specific isotope analysis data for carbon in benzene. Long-term groundwater benzene concentration reductions were achieved in spite of periodic rebounds resulting from water table fluctuations across the smear zone. Land application of gypsum is a potentially cost-effective sulfate delivery approach at sites with open, unpaved surfaces, relatively permeable geology, and shallow hydrocarbon impacts. However, more research is needed to understand the fate and persistence of sulfate and to improve the likelihood of success and effectiveness of this delivery approach. [ABSTRACT FROM AUTHOR]

Benzene, toluene, ethylbenzene, o-, m-, and p-xylenes (BTEX) are ubiquitous outdoor and indoor air pollutants associated with both environmental and health effects. The objective of this exploratory study was to determine the magnitude and variability of urinary BTEX levels among residents of two areas located in the same city (Nicosia, Cyprus). The two areas differed with respect to their proximity to an industrial cluster and an intercity-highway. First morning urine voids were collected during a random campaign from selected households in the two urban areas (n = 48). Urinary BTEX measurements were obtained using headspace solid phase micro extraction coupled with gas chromatography-mass spectrometry. The majority of participants were females (65%) and non-smokers (85%) with a mean age of 49 years. Median urinary BTEX levels were: 118 ng L −1 , 124 ng L −1 , 9 ng L −1 , 29 ng L −1 and 28 ng L −1 for benzene, toluene, ethylbenzene, (p + m)-xylene and o-xylene, respectively. With the exception of benzene, participants from area 2 (closer to the industrial cluster and an intercity road than area 1) had significantly (p < 0.05) higher urinary BTEX levels than those from area 1 (regression analysis). The residence location (in area 2) was the sole significant (p < 0.05) predictor of urinary BTEX levels after adjusting for sex, smoking, age, body mass index, and educational level. This observational study showed differences in BTEX exposures between two urban areas of the same city. This baseline BTEX dataset may prove useful for future activities of natural gas extraction and handling nearby urban settings. [ABSTRACT FROM AUTHOR]

Benzene, toluene, ethylbenzene, and xylenes are some of the most hazardous constituents found in commercial gasoline samples; therefore, these components must be monitored to avoid toxicological problems. We propose a new routine method of ultrafast gas chromatography coupled to flame ionization detection for the direct determination of benzene, toluene, ethylbenzene, and xylenes in commercial gasoline. This method is based on external standard calibration to quantify each compound, including the validation step of the study of linearity, detection and quantification limits, precision, and accuracy. The time of analysis was less than 3.2 min, with quantitative statements regarding the separation and quantification of all compounds in commercial gasoline samples. Ultrafast gas chromatography is a promising alternative method to official analytical techniques. Government laboratories could consider using this method for quality control. [ABSTRACT FROM AUTHOR]

Environmental pollution with petroleum products has become a major problem worldwide, and is a consequence of industrial growth. The development of sustainable methods for the removal of petroleum substances and their derivatives from aquatic and terrestrial environments and from air has therefore become extremely important today. Advanced technologies and materials dedicated to this purpose are relatively expensive; sorption methods involving mineral sorbents are therefore popular and are widely described in the scientific literature. Mineral materials are easily available, low-cost, universal adsorbents and have a number of properties that make them suitable for the removal of petroleum substances. This review describes recent works on the use of natural, synthetic and modified mineral adsorbents for the removal of petroleum substances and their derivatives from roads, water and air. [ABSTRACT FROM AUTHOR]

Mass transfer of light non-aqueous phase liquids (LNAPLs) trapped in porous media is a complex phenomenon. Water table fluctuations have been identified as responsible for generating significant variations in the concentration of dissolved hydrocarbons. Based on field evidence, this work presents a conceptual model and a numerical solution for mass transfer from entrapped LNAPL to groundwater controlled by both LNAPL saturation and seasonal water table fluctuations within the LNAPL smear zone. The numerical approach is capable of reproducing aqueous BTEX concentration trends under three different scenarios – water table fluctuating within smear zone, above the smear zone and partially within smear zone, resulting in in-phase, out-of-phase and alternating in-phase and out-of-phase BTEX concentration trend with respect to water table oscillation, respectively. The results demonstrate the model's applicability under observed field conditions and its ability to predict source zone depletion. [ABSTRACT FROM AUTHOR]

Gasoline spills from underground storage tanks are a worldwide environmental problem. BTEX and MtBE are the compounds of gasoline that present the highest degree of migration due to their chemical properties, and are therefore able to impact groundwater reservoirs. In situ chemical oxidation (ISCO) is an emerging technology for groundwater remediation. Several compounds such as permanganate and hydrogen peroxide among others have been used as oxidants, a strong impact of pH on the relative stabilities and reduction potentials having been in each case determined. This paper presents a study of stability and degradation of BTEX and MtBE at different pH ranges of a novel oxidant for ISCO, potassium ferrate (K 2 FeO 4 ). To carry out this study, BTEX and MtBE solutions were prepared in different phosphate buffers (pH 5,8; 7; 9; 10 and 11) in concentration ratio of (FeO 4 −2 )/(BTEX + MtBE) = 100:1. Each solution was analyzed at different times by gas chromatography with photoionization and tandem mass spectrometer detector. The results show a higher degree of degradation at pH 7 for Benzene and Toluene, and at pH 9 for Ethyl benzene and Xylenes, while MtBE proved recalcitrant to degradation by ferrate. The most favorable pH for stability of FeO 4 −2 solution was confirmed in 9–10. [ABSTRACT FROM AUTHOR]

Genotoxicity model is developed to assess the individual subacute toxicity of benzene, toluene, ethylbenzene, and xylene (BTEX) at very low levels as in a landfill gas. Golden Pothos ( Epipremnum aureum), a higher plant, was tested under variation of benzene 54-5656 ng/L, toluene 10-4362 ng/L, ethylbenzene 28-4997 ng/L, xylene 53-4845 ng/L, for 96 h. DNA fragmentation in plant leaves were investigated via comet assay. The results show that DNA migration ratio increased with the BTEX concentrations, but at different rates. The 50% effective concentration (EC) of DNA fragmentation from the dose-response relationships indicated toluene has the highest EC value and followed by benzene, xylene and ethylbenzene. Alternatively, ethylbenzene has the highest toxicity unit and followed by xylene, benzene and toluene as described by toxicity unit (TU). In conclusion, comet assay of Pothos can be used in differentiating DNA fragmentation against very low levels of BTEX in the atmosphere. Pothos is recommended for genotoxicity assessment of a low BTEX contaminated atmosphere. [ABSTRACT FROM AUTHOR]

In this work, biosurfactant-containing oxygen-releasing beads (BS-ORBs) were prepared and used for the bioremediation of BTEX in groundwater. The response surface methodology (RSM) was utilized to optimize the BS-ORBs. The results reveal that the optimal proportions of polyvinyl alcohol (PVA), biochar, CaO 2 , alginate, biosurfactant, and citrate were 33%, 32.5%, 13%, 13%, 5.8%, and 2.6% (w/w), respectively. The integrality ratio of optimized BS-ORB was 3.81%. The regression equation obtained from RSM accurately predicted the integrality ratio (R 2 = 0.994). The BS-ORBs continuously released oxygen (>0.5 mg/L) for 128 days. The concentration of the biosurfactant was maintained above 30 mg/L for 58 days. Batch experiments indicated that adding BS-ORB improved the bioremedation of the groundwater that contained high levels of BTEX (120 mg/L) for three cycles. These results indicate that the BS-ORBs are a potential oxygen-releasing material for the biomediation of groundwater that is contaminated with a high concentration of BTEX. [ABSTRACT FROM AUTHOR]

BTEX (benzene, toluene, ethylbenzene and xylenes) compounds are the most frequently encountered subsurface contaminants among the various petroleum hydrocarbons. In this study, a new strain, able to degrade BTEX compounds, was isolated from oil contaminated groundwater. Phylogenetic analysis revealed that the isolated strain was most closely related to Pseudomonas zhaodongensis with 98% 16SrRNA gene sequence similarity. A series of batch experiments were carried out to investigate the ability of the new strain for removing BTEX compounds using single and mixed substrates. The optimized values of pH, temperature, and inorganic nutrients (as percent of BTEX concentration) were 7.6, 28.9 °C, and 200%, respectively which were obtained by using the response surface methodology for the biodegradation of BTEX. Results showed that the identified strain was able to completely degrade benzene, toluene, and ethylbenzene in the single substrate batch experiments while m-xylene remained non-degradable. Results of dual-substrate experiments revealed co-metabolism of m-xylene in the presence of benzene and toluene. Dioxygenase was found to be the key enzyme incorporating in the co-metabolism of m-xylene. Within the mixed substrate batch experiments all BTEX compounds can be degraded. An increase in the production of cell growth due to the degradation of benzene and toluene accelerated the degradation process of m-xylene in the mixed substrate experiments. [ABSTRACT FROM AUTHOR]

Carbon nanospheres were covalently modified with hydroxy-terminated poly(dimethylsiloxane) to give a new sorbent (referred to as CNS-PDMS). It was applied as the extraction phase in a sol-gel based solid-phase microextraction fiber for benzene, toluene, ethylbenzene and o-xylene (BTEX). Due to the unique properties of CNS and the performance of the sol-gel coating technology, this fiber possesses a porous surface, a long operational lifespan (at least 200 times), and high thermal stability (up to 350°C). Its extraction capability is higher than that of commercial polydimethylsiloxane (PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibers. Following desorption, the BTEX were quantified by GC with FID detection. The detection limits (at an S/N ratio of 3) range from 1 to 10 pg mL, and the limits of quantification (at an SNR of 10) are between 3 and 30 pg mL. The repeatability of a single fiber (for n = 5) is between 3.9 and 6.3%, and the fiber-to-fiber reproducibility (for n = 3) ranges from 5.3 to 8.2%, respectively. The relative recoveries in the real water samples ranged from 92.5% to 99.5%. The results demonstrate that the method is highly effective for analyzing BTEX in water samples. [ABSTRACT FROM AUTHOR]

BTEX are recognized for their contribution as toxic and carcinogenic human health effects, and enhancement of the global greenhouse effect. Thus, an investigation of ambient BTEX was conducted at selected locations in Gorakhpur for a span of one year in order to ascertain the contagion levels. The concentrations of BTEX were measured at four locations in the city of Gorakhpur, which covers residential, agricultural, roadside and industrial areas with the help of low volume sampler. The samples were extracted with carbon disulphide by occasional agitation and the aromatic fraction was subjected to GC-FID. The average concentration of total BTEX in all samples was 50.8 μg/m 3 and the total range was from 10.9 μg/m 3 to 208.1 μg/m 3 with the median of 44.8 μg/m 3 . The BTEX concentrations were found to be 27.8, 35.9, 65.6 and 68.6 μg/m 3 at residential, agricultural, roadside and industrial sites respectively. The maximum concentration of total BTEX was found to be 61.9 μg/m 3 in winter season, followed by 47.9 μg/m 3 in summer and 42.7 μg/m 3 in monsoon season. The industrial site (35%) had the highest BTEX contribution followed by roadside (33%), agricultural (18%) and residential site (14%). The concentration of BTEX decreased in the order toluene > benzene > ethylbenzene > xylene. The integrated lifetime cancer risk for benzene at all sites, and ethylbenzene at roadside area was found to be higher than the acceptable value and ranges between 1.0E-05 and 7.6E-06, although the non-cancer health risk was found to be within acceptable limit along all the sites. Risk assessment can be used as a tool to ascertain influence on public health and also to encourage risk preclusion approaches directed towards effectual reduction of adverse health effects. [ABSTRACT FROM AUTHOR]

In this study, we prepared Bi 1-x Ba x FeO 3 MNPs (x = 0.03, 0.08, 0.12) via a rapid sol gel procedure to improve heterogeneous photo-Fenton catalytic degradation of toluene under visible light irradiation. We found that Ba-substitution in BiFeO 3 magnetic nanoparticles (BFO MNPs) can play an important role in improving the photo-Fenton catalytic degradation of toluene from aqueous solution. Increasing the Ba doping level up to 12%, greatly affect in iron redox cycling and oxygens vacancies as compared to pure BFO MNPs. The iron redox cycling and existence of oxygen on the surface of Ba doped BFO had been affected by the photo-Fenton process. The scavenger effect evident from the study results confirmed that the photo-Fenton catalytic degradation of toluene from aqueous solution was mainly controlled by the formation characteristics of hydroxyl radical ( OH) and also partially by the formation of other active species such singlet oxygen ( 1 O 2 ). The proposed radical reaction mechanism was also discussed. The degradation of toluene was partial in the dark but almost complete under visible light irradiation by the photo-Fenton catalytic degradation reaction. Bi 1-x Ba x FeO 3 (x = 0.12) showed the highest photo-Fenton catalytic degradation efficiency with a toluene removal of 98%, total organic carbon (TOC) and chemical oxygen demand (COD) reduction of 85% and 94%, respectively, after 40 min of visible light irradiation. [ABSTRACT FROM AUTHOR]

A series of Cs exchanged phosphomolybdic (PMA) catalysts were synthesised by the ion exchange method. The prepared materials were characterized by various physico-chemical techniques such as X-ray diffraction, FT-IR, Raman spectroscopy, pyridine adsorbed FT-IR spectroscopy, 31 P NMR, BET surface area, nitrogen isotherms, TEM and STEM analysis. XRD results show crystallites of the Keggin ion of heteropolyacid catalysts. FT-IR and Raman spectra data reveal that the Keggin structure of PMA catalyst is maintained even after the exchange of the protons with Cs ions. Pyridine adsorbed FT-IR spectra show that available Brønsted acidic sites increases after Cs is incorporated in PMA. TEM analysis shows that the spherical shape remains intact after Cs exchange and STEM analysis shows a uniform distribution of elements in the Cs exchanged PMA catalyst. Nitrogen isotherms studies reveal a type IV isotherms for the Cs exchanged catalyst. The Cs exchanged phosphomolybdic acid (CsPMA) showed better catalytic performance than the phosphomolybdic acid (PMA) catalyst when evaluated for the C H bond activation of toluene to benzaldehyde. The catalyst was easily recovered and reused for five cycles with stable activity. [ABSTRACT FROM AUTHOR]