Search

Aromatic hydrocarbons like benzene, toluene, xylene, and ethylbenzene (BTEX) can escape into the environment from oil and gas operations and manufacturing industries posing significant health risks to humans and wildlife. Unlike conventional clean-up methods used, biological approaches such as bioremediation can provide a more energy and labour-efficient and environmentally friendly option for sensitive areas such as nature reserves and cities, protecting biodiversity and public health. BTEX contamination is often concentrated in the subsurface of these locations where oxygen is rapidly depleted, and biodegradation relies on anaerobic processes. Thus, it is critical to understand the anaerobic biodegradation characteristics as it has not been explored to a major extent. This review presents novel insights into the degradation mechanisms under anaerobic conditions and presents a detailed description and interconnection between them. BTEX degradation can follow four activation mechanisms: hydroxylation, carboxylation, methylation, and fumarate addition. Hydroxylation is one of the mechanisms that explains the transformation of benzene into phenol, toluene into benzyl alcohol or p-cresol, and ethylbenzene into 1-phenylethanol. Carboxylation to benzoate is thought to be the primary mechanism of degradation for benzene. Despite being poorly understood, benzene methylation has been also reported. Moreover, fumarate addition is the most widely reported mechanism, present in toluene, ethylbenzene, and xylene degradation. Further research efforts are required to better elucidate new and current alternative catabolic pathways. Likewise, a comprehensive analysis of the enzymes involved as well as the development of advance tools such as omic tools can reveal bottlenecks degradation steps and create more effective on-site strategies to address BTEX pollution. [Display omitted] • Fumarate addition is an alternative activation step in Ethylbenzene biodegradation. • Benzyl alcohol and cresol are two alternative intermediates in Toluene's pathway. • Omics tools can help to identifty bottleneck steps and unknown compounds. • Benzene methylation and hydroxylation are simultaneously activated mechanism. [ABSTRACT FROM AUTHOR]

Abstract We investigated the personal exposure of gas station employees to benzene, toluene, ethylbenzene, xylene, formaldehyde, and acetaldehyde at three full-service gas stations in Okayama, Japan. We also assessed both the indoor (offices) and ambient background concentrations. The personal exposure, indoor, and ambient concentrations of benzene were 57.3, 6.11, and 1.31 μg/m3, respectively, in spring and 17.0, 2.04, and 0.603 μg/m3, respectively, in winter. Those for toluene were 196, 25.8, and 2.66 μg/m3, respectively, in spring and 30.6, 5.31, and 1.23 μg/m3, respectively, in winter. The personal exposure concentrations of benzene, toluene, ethylbenzene, and xylene for a gas station employee were significantly higher than those for indoors and the ambient air. However, the personal exposure, indoor, and ambient concentrations of formaldehyde were 5.08, 10.1, and 4.29 μg/m3, respectively, in spring and 11.6, 24.1, and 6.04 μg/m3, respectively, in winter. The indoor concentrations of formaldehyde were significantly higher than both the personal exposure concentrations for gas station employees and the ambient concentrations. The excess lifetime cancer risk from benzene exposure was estimated to be 2.22 × 10−5, 2.43 × 10−6, and 2.56 × 10−7 for full-service gas station employees, self-service gas station employees, and self-service gas station users who are assumed to use the station once a week, respectively. Assuming the occupational exposure to toluene, ethylbenzene, and xylene at the gas station were comparable to the maximum 2-h average exposure levels in the present study, the total hazard quotient for non-carcinogenic risk was calculated to be much lower than 1 (2.72–5.56 × 10−3) based on the TLV-TWA (8-h). Highlights • Gas station employee's VOC exposure levels were higher than indoor and ambient air. • Indoor formaldehyde was higher than gas station employee's exposure and ambient air. • Exposure levels to TVOC in gas station showed sharp increase during refueling. • Excess lifetime cancer risk was estimated to be 2.2 × 10−5 for refueling employees. • Non-cancer risk of refueling employees were much lower than TLV-TWA (8-h). [ABSTRACT FROM AUTHOR]

Abstract Indoor potted plants are able to remove volatile organic compounds (VOC) from air, but only few studies have investigated the removal of compounds in mixtures. Here, we present a non-targeted pixel-based fingerprinting analysis documenting the removal of a complex mixture of gasoline VOCs by Hedera helix under dynamic chamber conditions allowing for air exchange and continuous gasoline exposure. For 15 days, the entire potted plant was exposed to gasoline; subsequently, the epigeous plant parts were removed and the soil microcosm (i.e. soil, plant roots and microorganisms) was exposed to gasoline for another eight days. Quantitative analysis was performed for heptane, 3-methylhexane, toluene, ethylbenzene and m,p-xylenes, and the CHEMSIC method (CHEMometric analysis of Selected Ion Chromatograms) was used for non-targeted pixel-based fingerprinting analysis. The quantitative analysis demonstrated that the presence of potted plants or pots without epigeous plant parts led to a reduction of selected VOCs by 16.7–22.6%. The CHEMSIC method confirmed this and revealed that all gasoline VOCs were reduced in concentration when H. helix was present. The estimate for the total VOC removal was in the range of 11–32%. The removal was highest for samples where the epigeous plant parts were absent and compounds known to be hard to degrade by microorganisms such as dimethylcyclopentanes were removed the least compared to compounds more easily degraded by microorganisms such as heptane when epigeous plant parts were removed. All findings support the conclusion that the soil microcosm was the main responsible for the removal of VOCs. Highlights • Potted Hedera helix was exposed to gasoline under dynamic conditions. • Data was analyzed by a non-targeted pixel-based fingerprinting approach. • All gasoline VOCs were reduced in concentration by H. helix. • Preferential removal of some compounds was observed. • The soil microcosm play a substantial role in removal of gasoline VOCs. [ABSTRACT FROM AUTHOR]

Benzene series are considered as air pollutants in refineries. However, the emissions of benzene series in fluid catalytic cracking (FCC) flue gas are poorly understand. In this work, we conduct stack tests on three typical FCC units. Benzene series, including benzene, toluene, xylene and ethyl benzene, are monitored in the flue gas. It shows that the coking degree of the spent catalysts affect the emissions of benzene series significantly, and there are four kinds of carbon-containing precursors in the spent catalyst. A fixed-bed reactor is used to conduct the regeneration simulation experiments, and the flue gas is monitored by TG-MS and FTIR. The emissions of toluene and ethyl benzene are mainly emitted in the early and middle stage of the reaction (250–650 °C), while the emission of benzene is mainly detected in the middle and late stage of the reaction (450–750 °C). Xylene group is not detected in the stack tests and regeneration experiments. Higher emissions of benzene series are released from the spent catalyst with lower C/H ratio during regeneration process. With the increase of oxygen content, the emissions of benzene series decrease, and the initial emission temperature is advanced. These insights can improve the refinery's awareness and control of benzene series in the future. [Display omitted] • Benzene series emissions are detected in FCC flue gas. • The main carbon-containing precursor in spent catalysts is aromatic carbon. • The emission characteristics of benzene series are presented. • The coking degree of spent catalyst affects benzene series emissions. • High O 2 content could decrease benzene series emissions. [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]

An effectively and functionally magnetic multi-walled carbon nanotube (MWCNTs) nano-composite (APCNT-KOH) was synthesized by a one-pot and facile method. The residual Fe catalyst particles of the as-prepared MWCNTs were utilized as magnetic materials through KOH activation. The resulting APCNT-KOH exhibited very high adsorption capacities for toluene (T), ethylbenzene (E), and xylene (X) (TEX) pollutants than many other adsorbents, because of their large specific surface area and high degree of surface activity. The adsorption process was found to be pH, ionic strength, and temperature dependent, and the maximum adsorption capacity was observed at pH 6 for TEX pollutants. The adsorption isotherm data were analyzed by applying the Langmuir, Freundlich, and Dubinin-Radushkevich isothermal models. The Langmuir model showed the best fit to the experimental isotherm data with a maximum adsorption capacity(q m , toluene = 63.34 mg/g, q m , ethylbenzene = 249.44 mg/g, q m , m-xylene = 227.05 mg/g, q m , o-xylene = 138.04 mg/g, q m , p-xylene = 105.59 mg/g). Adsorption kinetics of TEX on APCNT-KOH was appropriately described by the pseudo-second-order rate model. The desorption experiments revealed the typical adsorption-desorption hysteresis, indicating that the adsorption and desorption processes of TEX undergo different pathways due to porous structure changes before and after adsorption and desorption. Collective results demonstrate that the functionalized magnetic APCNT-KOH composites are highly-effective adsorbents for TEX removal, which provides a promising and green route for MWCNTs in wastewater treatment. [ABSTRACT FROM AUTHOR]

Cytotoxicity of benzene, toluene, ethylbenzene and xylenes (BTEX) to human lung cells was explored using three different exposure methods: Method 1 – in normal 96-well plates using DMSO as a carrier vehicle, we exposed (a) human lung carcinoma A549 cells, (b) A549 cells over-expressed with cytochrome P450 2E1 cells, and (c) normal lung fibroblast LL-24 cells to benzene, toluene, ethylbenzene and xylene individually and in a mixture which models car exhaust gases for between 1–88 h. We found that the order of the BTEX potency is benzene < toluene < ethylbenzene = m- xylene with acute BTEX toxicity to A549 ≈ LL-24 > CYP2E1 over-expressed A549 cells. A significant difference was found between inter-assay responses for all 24 h exposures ( P < 0.005) suggesting a poor assay repeatability. No sign of potency increase was found from 6 to 72 h exposures. Method 2 – Using sealed vials to expose A549 cells to benzene, toluene and ethylbenzene, we observed a twenty-fold increase in their cytotoxicity, but also with no time-course effect. Method 3 – Using air exposed hanging-drop cell culture, we were able to see both an increase of demonstration of toxicity and a time-course effect from 1 to 12 h exposure. We conclude that exposing cells in sealed and unsealed media using DMSO as a carrier vehicle was not suitable for BTEX exposure studies. Hanging-drop air exposure has more potential. It should be noted that if there are any changes in their exposure matrixes, its exposure mass distribution in cells could differ. [ABSTRACT FROM AUTHOR]

Highlights: [•] Removal of ethylbenzene was enhanced significantly by Tween-20 and Zn (II). [•] The metal ion Zn (II) improved dissolving of the surfactant Tween-20. [•] The optimum dosages of the surfactant and zinc ion were evaluated. [•] The toxicities of Tween-20 and Zn (II) to biofilms in the biofilter were examined. [Copyright &y& Elsevier]

Abstract: The levels of PBDEs, alternate BFRs and dechloranes in European Eel (Anguilla anguilla) samples (elvers, yellow and silver eels) were investigated to compare the contamination of eels from the rivers Elbe and Rhine and to estimate the BFR contamination throughout the eel’s life cycle. PBDEs were the dominating flame retardants (FRs) in muscle tissues of yellow and silver eels, while the alternate BFR 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE) and the Dechlorane 602 were the dominating FRs in elvers (juvenile eels). Concentrations of FRs in silver eels from river Rhine were generally higher than concentrations in other eels analysed with up to 46ngg−1 wet weight (ww) ∑PBDEs. The concentrations in yellow and silver eels from river Elbe were similar with an average of 9.0±5.1ngg−1 ww and 8.1±3.7ngg−1 ww respectively. PBDE concentrations in elvers were comparably low (0.02 (BDE-100) to 0.1 (BDE-183) ngg−1 ww), which lead to the conclusion that these contaminants were mostly ingested within the rivers. Among the alternate BFRs and dechloranes, DPTE as well as the Dechlorane 602 and Dechlorane Plus (DP) were found in all life cycle stages and rivers with concentrations between 0.01ngg−1 ww and 0.7ngg−1 ww. Dechlorane 603 could only be detected in silver eels from river Rhine. Pentabromoethylbenzene (PBEB) was only found in yellow and silver eels and bis(2-ethylhexyl)tetrabromophthalate (BEHTBP) could only be detected in elvers. These are the first reports of Dec-602 and 603 in aquatic organisms from Europe. The results of this study show the lasting relevance of PBDEs as contaminants in rivers and river-dwelling species but also the growing relevance of emerging contaminants such as alternate BFRs and dechloranes. [Copyright &y& Elsevier]

Abstract: Little information is available about the toxicity of toluene, ethylbenzene and xylene acting on macrophytes, and their toxicity data are rarely used in regulation and criteria decisions. The results extended the knowledge on toxic effects of toluene, ethylbenzene and xylene on aquatic plants. The responses of Hydrilla verticillata to these pollutants were investigated. Chlorophyll levels, lipid peroxidation, and antioxidant enzymes (superoxide dismutase and guaiacol peroxidase) showed diverse responses at different concentrations of toluene, ethylbenzene and xylene. The linear regression analyses were performed respectively, suggesting the concentrations of toluene, ethylbenzene and xylene expected to protect aquatic macrophytes were 7.30mgL−1, 1.15mgL−1 and 2.36mgL−1, respectively. This study emphasized that aquatic plants are also sensitive to organic pollutants as fishes and zooplanktons, indicating that macrophytes could be helpful in predicting the toxicity of these pollutants and should be considered in regulation and criteria decisions for aquatic environment protection. [Copyright &y& Elsevier]

Abstract: Laboratory experiments were performed to investigate the partitioning behavior of a set of diverse volatile organic compounds (VOCs). After equilibration at a temperature of 25°C, the VOC concentrations were measured by headspace method in combination with gas chromatography/mass spectrometry (GC/MS). The obtained data were used to determine the partition coefficients (KP ) of VOCs in a gas–liguid–solid system. The results have shown that the presence and nature of solid materials in the working solution control the air–water partitioning of dissolved VOCs. The air/solution partitioning of BTEX and C9–C10 aldehydes was most affected in the presence of diesel soot. KP values decreased by a factor ranging from 1.5 for toluene to 3.0 for ethylbenzene. The addition of mineral dust in the working solution exhibited greater influence on the partitioning of short aldehydes. KP values decreased by a factor of 1.8. The experimental partition coefficients were used to develop a predictive model for partitioning of BTEX and n-aldehydes between air, water and solid phases. [Copyright &y& Elsevier]

Abstract: Glutathione pathway was specifically studied in rats exposed by inhalation to a range of ethylbenzene vapours (5–2000ppm). Urines were collected during exposure (6h) and over the 18h following the exposure. The potential metabolites coming from either side-chain or ring oxidation were synthesized: 1-, 2-phenylethylmercapturic acids (1-, and 2-PEMA) and 2-, 3- and 4-ethylphenylmercapturic acids (2-, 3-, and 4-EPMA). Their synthesis was fully described and the molecules characterized. Urine samples were analysed using a selective HPLC–fluorescence method. Among the five metabolites, 2-PEMA was never observed in any urine sample. By contrast, 1-PEMA was discovered in its two diastereomeric forms, and it was shown that one of them was mainly present. 2-EPMA, 3-EPMA and 4-EPMA (in the ratio 1:2:6) were also found, and their combined excretion levels were similar to that of 1-PEMA. The atmospheric concentrations and urinary excretions yielded very close correlations which allow us to consider these mercapturic acids as novel ethylbenzene exposure biomarkers. [Copyright &y& Elsevier]

Abstract: The degradation of volatile organic compounds in a commercially available non-thermal plasma based air purifying system was investigated. Several studies exist that interrogate the degradation of VOCs in closed air systems using a non-thermal plasma combined with a heterogeneous catalyst. For the first time, however, our study was performed under realistic conditions (normal indoor air, 297.5K and 12.5gm−3 water content) on an open system, in the absence of an auxiliary catalyst, and using standard operating air flow rates (up to 320Lmin−1). Cyclohexene, benzene, toluene, ethylbenzene and the xylene isomers were nebulized and guided through the plasma air purifier. The degradation products were trapped by activated charcoal tubes or silica gel tubes, and analyzed using gas chromatography mass spectrometry. Degradation efficiencies of 11±1.6% for cyclohexene, <2% for benzene, 11±2.4% for toluene, 3±1% for ethylbenzene, 1±1% for σ-xylene, and 3±0.4% for m-/ρ-xylene were found. A fairly wide range of degradation products could be identified. On both trapping media, various oxidized species such as alcohols, aldehydes, ketones and one epoxide were observed. The formation of adipaldehyde from nebulized cyclohexene clearly indicates an ozonolysis reaction. Other degradation products observed suggests reactions with OH radicals. We propose that mostly ozone and OH radicals are responsible for the degradation of organic molecules in the plasma air purifier. [Copyright &y& Elsevier]

Abstract: Unlike previous photocatalytic oxidation (PCO) studies incorporated with adsorption, this study investigates the feasibility of applying a tandem PCO-adsorption hybrid technique regarding low-level monoaromatic compound removal. The PCO efficiencies decreased as the hydraulic diameter (HD) increased. A PCO reactor of a medium HD size was selected for further experiments. Under conditions relevant to the use of the PCO system, the CO level measured during the PCO process was minimal in comparison to indoor CO levels. Trace level formations of formaldehyde and acetaldehyde were observed during the photocatalytic process, but these compounds were undetectable at the activated carbon unit outlet. The degradation efficiencies, obtained from the PCO unit, exhibited a dependence on both the inlet concentration (IC) and relative humidity (RH), whereas those from the PCO-adsorption hybrid system did not. Under specific conditions, the PCO unit presented a high degradation efficiency of close to, or exceeding 90%, in regards to ethyl benzene, o-xylene, and m,p-xylene. However, the benzene air concentrations, after being treated by the PCO unit, substantially exceeded the USEPA inhalation reference concentration guideline of 30μgm−3 (corresponding to 0.01ppm). In contrast, the PCO-adsorption hybrid system presented a high removal efficiency of close to 100% regarding all compounds, regardless of the IC or RH range. Consequently, it is suggested that the PCO-adsorption hybrid system has a synergistic advantage of photocatalysis and adsorption in regards to the BTEX elimination process. [Copyright &y& Elsevier]

Bisphenol A (BPA) is a recognized endocrine-disrupting chemical (EDC), and its analogues also exert negative effects on health. The structure–affinity relationship between the structures of nine bisphenol (BP) analogues and the conformational changes of bovine serum albumin (BSA) was studied by various characterization methods and molecular docking. BPs including BPA and its analogues, bisphenol B (BPB), bisphenol C (BPC), bisphenol AP (BPAP), bisphenol M (BPM), bisphenol P (BPP), bisphenol Z (BPZ), diethylstilbestrol (DES) and dienestrol (DS) interacted with BSA. At the concentration of 3.85 × 10−5 mol l−1, DS was found to lead to 64% quenching, while BPAP, BPM and DES quenched 60%, 59% and 55% of BSA fluorescence, respectively. The values of Δ H (−19.31–135.42 kJ mol−1) and Δ S (12.52–495.63 J mol−1 K−1) indicated that hydrophobic interactions and hydrogen bonds played important roles in the binding process. The binding constants of DS (8.87 × 104 l mol−1), DES (3.05 × 104 l mol−1), BPAP (1.52 × 104 l mol−1), BPC (1.16 × 104 l mol−1) and BPM (1.10 × 104 l mol−1) to BSA were greater than that of BPA (1.18 × 103 l mol−1) to BSA, indicating that they may exert more negative effects than BPA. The molecular structure differences of these BPs partly affected their ability to bind to BSA. The binding constants of BPB/BPP to BSA were smaller due to the steric hindrance of ethyl and benzene ring. BPs with conjugated double bond structures (DS and DES) and benzene ring structures (BPM, BPP, BPAP) had a greater influence on the conformation of BSA. [Display omitted] • The structure-activity relationships between BPs structure and BSA conformation changes were studied. • The type of substituents were the main factors affecting the structure-activity relationship. • BPs exhibited the stronger affinity to BSA and induced the greater changes in BSA conformation. [ABSTRACT FROM AUTHOR]

High-impact polystyrene (HIPS) flame retarded with decabromodiphenyl ether (DDE), has been reacted in supercritical water from 380 to 450°C and 21.5 to 31.0MPa pressure in a batch reactor. Different concentrations of sodium hydroxide additive were used in situ to neutralize the corrosive inorganic bromine species released during the reactions. It appeared that supercritical water conditions lowered the decomposition temperature of both the fire-retardant DDE and HIPS. The reaction products included oils (up to 76wt%), char (up to 18wt%) and gas (up to 2.4wt%) which was mainly methane. The presence of the alkaline water led to up to 97wt% debromination of the product oil, producing virtually bromine-free oil feedstock. The removal of antimony from the oil product during processing was of the order of 98wt%. The oil consisted of many single- and multiple-ringed aromatic compounds, many of which had alkyl substituents and/or aliphatic C n -bridges (n =1–4). The major single-ringed compounds included toluene, xylenes, ethylbenzene, propylbenzene and α-methylstyrene. Bibenzyl (diphenylethane), stilbene, diphenylmethane, diphenylpropane, diphenylcyclopropane, diphenylpropene, diphenylbutane, diphenylbutene and diphenylbuta-1,3-diene were the major C n -bridged compounds. Diphenyl ether and acetophenone were the major oxygenated compounds found. The process thus has the potential to produce bromine-free and antimony-free oils from fire-retardant plastics. [Copyright &y& Elsevier]

Abstract: In the present work, a sample pre-treatment technique for the determination of trace concentrations of benzene, toluene, ethyl benzene and xylene (BTEX) in aqueous samples has been developed and applied to analysis of the selected analytes in environmental water samples. The extraction procedure is based on coupling polypropylene hollow-fiber liquid phase microextraction (HF-LPME) with gas chromatography by flame ionization detection (GC-FID). The effective parameters such as organic solvent, extraction time, agitation speed and salting effect were investigated. Good reproducibilities of the extraction performance were obtained, with the RSD values ranging from 2.02 to 4.61% (n =5). The method provided 41.47–128.01 fold preconcentration of the target analytes. The limits of detections for the BTEX were in the range of 0.005–03μgml−1. In addition, sample clean-up was achieved during LPME due to the selectivity of the hollow fiber, which prevented undesirable large molecules from being extracted. Real samples (River and waste waters) containing BTEX were examined using this method with good linearity and precision (RSDs most lower than 6.00%, n = 5). All experiments were carried out at room temperature, 22±0.5°C. [Copyright &y& Elsevier]

Abstract: In this study, a full-scale biosparging investigation was conducted at a petroleum-hydrocarbon spill site. Field results reveal that natural attenuation was the main cause of the decrease in major contaminants [benzene, toluene, ethylbenzene, and xylenes (BTEX)] concentrations in groundwater before the operation of biosparging system. Evidence of the occurrence of natural attenuation within the BTEX plume includes: (1) decrease of DO, nitrate, sulfate, and redox potential, (2) production of dissolved ferrous iron, sulfide, methane, and CO2, (3) decreased BTEX concentrations along the transport path, (4) increased microbial populations, and (5) limited spreading of the BTEX plume. Field results also reveal that the operation of biosparging caused the shifting of anaerobic conditions inside the plume to aerobic conditions. This variation can be confirmed by the following field observations inside the plume due to the biosparging process: (1) increase in DO, redox potential, nitrate, and sulfate, (2) decrease dissolved ferrous iron, sulfide, and methane, (3) increased total cultivable heterotrophs, and (4) decreased total cultivable anaerobes as well as methanogens. Results of polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequence analysis reveal that three BTEX biodegraders (Candidauts magnetobacterium, Flavobacteriales bacterium, and Bacteroidetes bacterium) might exist at this site. Results show that more than 70% of BTEX has been removed through the biosparging system within a 10-month remedial period at an averaged groundwater temperature of 18°C. This indicates that biosparging is a promising technology to remediate BTEX contaminated groundwater. [Copyright &y& Elsevier]

A trace analytical method of benzene, toluene, ethylbenzene and xylenes (BTEX) in water has been developed by using headspace solid-phase microextraction (HS-SPME) coupled to cryo-trap gas chromatography–mass spectrometry (GC–MS). The chromatographic peak shape for BTEX was improved by using cryo-trap equipment. The HS-SPME experimental procedures to extract BTEX from water were optimized with a 75μm carboxen/polydimethylsiloxane (CAR/PDMS)-coated fiber at a sodium chloride concentration of 267gl−1, extraction for 15min at 25°C and desorption at 290°C for 2min. Good linearity was verified in a range of 0.0001–50μgl−1 for each analyte (r 2 =0.996–0.999). The limits of detection (LODs) of BTEX in water reached at sub-ngl−1 levels. LODs of benzene, toluene, ethylbenzene, m/p-xylene and o-xylene were 0.04, 0.02, 0.05, 0.01 and 0.02ngl−1, respectively. The proposed analytical method was successfully used for the quantification of trace BTEX in ground water. The results indicate that HS-SPME coupled to cryo-trap GC–MS is an effective tool for analysis of BTEX in water samples at the sub-ngl−1 level. [Copyright &y& Elsevier]

Abstract: Hazardous Air Pollutants (HAPs) have a potential to be distributed into different component of environment with varying persistence. In the current study fourteen HAPs have been quantified in the air using TO-17 method in an industrial area of Mumbai. The distribution of these HAPs in different environmental compartments have been calculated using multi media mass balance model, TaPL3, along with long range transport potential and persistence. Results show that most of the target compounds partition mostly in air. Phenol and trifluralin, partition predominantly into soil while ethyl benzene and xylene partition predominantly into vegetation compartment. Naphthalene has the highest persistence followed by ethyl benzene, xylene and 1,1,1 trihloro ethane. Long range transport potential is maximum for 1,1,1 trichloroethane. Assessment of human health risk in terms of non-carcinogenic hazard and carcinogenic risk due to exposure to HAPs. have been estimated for industrial workers and residents in the study area considering all possible exposure routes using the output from TaPL3 model. The overall carcinogenic risk for residents and workers are estimated as high as unity along with very high hazard potential. [Copyright &y& Elsevier]

The biodegradability of alkylate compounds in serum bottles was investigated in the presence and absence of ethanol or benzene, toluene, ethylbenzene, and p-xylene (BTEX). The biomass was acclimated to three different alkylates, 2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane in porous pot reactors. The alkylates were completely mineralized in all three sets of experiments. They degraded more slowly in the presence of BTEX than in their absence because BTEX inhibited the microbial utilization of alkylates. However, in the presence of ethanol, their slower biodegradation was not related to inhibition by the ethanol. Throughout the experiments alkylates, ethanol, and BTEX concentrations did not change in the sterile controls. [Copyright &y& Elsevier]

The potential environmental impact of aromatic and halogenated chemicals from the petrochemical and steel industry is of growning concern. The present paper deals with the modelling and experimental determination of density and speed of sound at the range 278.15–323.15 of six aromatic and halogenated compounds (Benzene, Toluene, Ethylbenzene, Fluorobenzene, 2-Fluorotoluene and Chlorobenzene). Fitting equations were applied to the data in order to correlate for later computer based design. The estimation of the studied properties was made by the application of different theoretical procedures. The Mchaweh–Nasrifar–Moshfeghian model (MNM), an equation of state based on the generalized van der Waals theory which combines the Staverman–Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the Free Length Theory showed a good response at the studied conditions. [Copyright &y& Elsevier]

Abstract: An analytical method capable of determining trace levels of BTEX-aromatics (benzene, toluene, ethylbenzene, m-, p- and o-xylenes) in the atmosphere with as high resolution as possible has been developed. The method is based on the preconcentration of air samples using a multibed tube (Carbopack C, Carbograph 1) at ambient temperature, followed by thermal desorption, and analysis of aromatic species by a β-cyclodextrin capillary chromatography coupled with mass spectrometry. The resolution achieved was sufficient for individual separation of BTEXs as well as m- and p-xylenes. The BTEX-ratios have been determined in an air tunnel and in on-road, suburban and rural forest atmosphere. The ethylbenzene/m-xylene ratios could provide a deep insight into anthropogenic related NMHC patterns at different locations and under different meteorological conditions and may reflect photochemical processes in the best way. [Copyright &y& Elsevier]

Abstract: Fenton’s destruction of benzene, toluene, ethylbenzene, and xylene (BTEX) was investigated in soil slurry batch reactors. The purpose of the investigation was to quantify the enhancement of oxidation rates and efficiency by varying process conditions such as iron catalyst (Fe(II) or Fe(III); 2, 5, and 10mM), hydrogen peroxide (H2O2; 30, 150, 300mM), and metal chelating agents (l-ascorbic acid, gallic acid, or N-(2-hydroxyethyl)iminodiacetic acid). Rapid contaminant mass destruction (97% after 3h) occurred in the presence of 300mM H2O2 and 10mM Fe(III). An enhanced removal rate (>90% removal after 15min and 95% removal after 3h) was also observed by combining Fe(III), N-(2-hydroxyethyl)iminodiacetic acid and 300mM H2O2. The observed BTEX mass removal rate constants (3.6–7.8×10−4 s−1) were compared to the estimated rate constants (4.1–10.1×10−3 s−1). The influence of non-specific oxidants loss (by reaction with iron hydroxides and soil organic matter) was also explored. [Copyright &y& Elsevier]

The objectives of this research are to investigate the remediation efficiency and electrokinetic behavior of ethylbenzene-contaminated clay by a surfactant-aided electrokinetic (SAEK) process under a potential gradient of 2 V cm-1. Experimental results indicated that the type of processing fluids played a key role in determining the removal performance of ethylbenzene from clay in the SAEK process. A mixed surfactant system consisted of 0.5% SDS and 2.0% PANNOX 110 showed the best performance of ethylbenzene removed in the SAEK system. The removal efficiency of ethylbenzene was determined to be 63–98% in SAEK system while only 40% was achieved in an electrokinetic system with tap water as processing fluid. It was found that ethylbenzene was accumulated in the vicinity of anode in an electrokinetic system with tap water as processing fluid. However, the concentration front of ethylbenzene was shifted toward cathode in the SAEK system. The electroosmotic permeability and power consumption were 0.17 × 10-6–3.01 × 10-6 cm2 V-1 s-1 and 52–123 kW h m-3, respectively. The cost, including the expense of energy and surfactants, was estimated to be 5.15–12.65 USD m-3 for SAEK systems, which was 2.0–4.9 times greater than that in the system of electrokinetic alone (2.6 USD m-3). Nevertheless, by taking the remediation efficiency of ethylbenzene and the energy expenditure into account for the overall process performance evaluation, the system SAEK was still a cost-effective alternative treatment method. [Copyright &y& Elsevier]

Volatile organic compounds (VOCs) have been determined to be human risk factors in urban environments, as well as primary contributors to the formation of photochemical oxidants. Ambient air quality measurements of 54 VOCs including hydrocarbons, halogenated hydrocarbons and carbonyls were conducted in or near 13 urban locations in the United States during September 1996 to August 1997. Air samples were collected and analyzed in accordance with US Environmental Protection Agency-approved methods. The target compounds most commonly found were benzene, toluene, xylene and ethylbenzene. These aromatic compounds were highly correlated and proportionally related in a manner suggesting that the primary contributors were mobile sources in all the urban locations studied. Concentrations of total hydrocarbons ranged between 1.39 and 11.93 parts per billion, by volume (ppbv). Ambient air levels of halogenated hydrocarbons appeared to exhibit unique spatial variations, and no single factor seemed to explain trends for this group of compounds. The highest halogenated hydrocarbon concentrations ranged from 0.24 ppbv for methylene chloride to 1.22 ppbv for chloromethane. At participating urban locations for the year of data considered, levels of carbonyls were higher than the level of the other organic compound groups, suggesting that emissions from motor vehicles and photochemical reactions strongly influence ambient air concentrations of carbonyls. Of the most prevalent carbonyls, formaldehyde and acetaldehyde were the dominant compounds, ranging from 1.5–7.4 ppbv for formaldehyde, to 0.8–2.7 ppbv for acetaldehyde. [Copyright &y& Elsevier]

Refinery effluents represent an emission source of hydrocarbons (HCs) and other constituents to the environment. Thus, characterisation of effluent quality in terms of concentrations of key parameters relative to permitted standards is important and for total petroleum hydrocarbons (TPH), the specific composition of the HC mixture can affect its toxicity to aquatic organisms. Therefore, this study was designed to analyse TPH, benzene, toluene, ethyl benzene, xylenes (BTEX), polycyclic aromatic hydrocarbons (PAHs), (bio) chemical oxygen demand, total nitrogen, total suspended solids and selected metals before, and after, treatment steps to demonstrate removal efficiencies across 13 refineries with variable wastewater treatment systems. Final discharge concentrations of the measured parameters were by 97% within the so called Best Available Technique Associated Emission Levels (BAT-AELs). Further, TPH composition was characterised using high-resolution two-dimensional gas chromatography (GCxGC) analysis to understand the mass distribution by carbon number and specific chemical class. Measurements were compared to SimpleTreat model predictions for validation. SimpleTreat successfully predicted the shape of the effluent composition since it is essentially a removal constant applied to the influent composition. The predictions were of similar magnitude as, or were greater than, the effluent concentrations since SimpleTreat is based on typical performance and is intended to be conservative. This was especially true for aromatic constituents. Reduction in potential HC exposures also coincided with a decrease in predicted toxicity using a mechanistic oil toxicity model, PETROTOX. Overall, the results indicate that EU petroleum refineries are likely to achieve a high performance level regarding effluent treatment. [Display omitted] • EU refinery WWTP performance meet EU Industrial Emissions Directive BAT-AELs. • GCxGC analysis was used to monitor hydrocarbon composition change during treatment. • Final effluents discharged from oil refineries have generally low bioavailability. [ABSTRACT FROM AUTHOR]