Search

Benzene, toluene, ethylbenzene and xylene (BTEX) possess a negative impact on the environment and human beings due to their highly toxic and carcinogenic properties. In this study, persulfate (PS) activated by nano zero-valent iron (nZVI) coupled with chelated L-cysteine (L-cys) process was investigated for BTEX degradation in contaminated groundwater. BTEX degradation had a significant acceleration and improvement with the removal from 62.7 to 100% along with the increasing dosage of L-cys from 0.12 to 0.27 M in 24 h. Further, the compact nZVI catalytic cylinder and nZVI encapsulated L-cys catalytic cylinder were successfully manufactured by encapsulating nZVI, and nZVI and L-cys together with additives of cement, river sand, stearic acid (SA) and zeolite. The SEM image, XRD patterns and FTIR spectra showed that the manufactured catalytic cylinder had a porous structure and encapsulated nZVI and L-cys successfully. Six successive cycles of BTEX degradation were completed and the degradation rate decreased gradually in each cycle. The catalytic activity of nZVI encapsulated L-cys catalytic cylinder was superior to nZVI catalytic cylinder in each cycle. The electron paramagnetic resonance (EPR) results indicated that HO• was the dominant active species in the BTEX degradation process. Benzoic acid (BA) scavenge experiments showed that L-cys could increase the yield of HO• in the PS/nZVI system. The HO• yields of PS/nZVI encapsulated L-cys catalytic cylinder system were 3.2 to 4.8 fold higher than those of the PS/nZVI catalytic cylinder system. The possible mechanisms of PS activation by nZVI encapsulated L-cys catalytic cylinder were supposed. Homogeneous Fenton reaction and heterogeneous catalysis on the nZVI surface are two co-existence mechanisms in the PS/nZVI encapsulated L-cys catalytic cylinder system. The findings of this study provide new insights into the mechanism of nZVI encapsulated L-cys catalytic cylinder activating PS, showing its potential applications for the remediation of groundwater. HIGHLIGHTS PS/nZVI/L-cys system was applied to remediate BTEX contaminants.; The compact nZVI encapsulated L-cys catalytic cylinder was successfully manufactured.; Six successive cycles of BTEX degradation were completed.; Two co-existence mechanisms in the PS/nZVI encapsulated L-cys catalytic cylinder system were investigated.; PS/nZVI catalytic cylinder systems were recommended for BTEX-contaminated groundwater remediation.;

Microbial communities in groundwater ecosystems can develop the capacity to degrade complex mixtures of chemicals resulting from pollution by landfill leachate. Monitoring this natural attenuation requires insight into the metabolic potential and activity of microbial communities. We contrasted the metagenomes and metatranscriptomes from a leachate-polluted aquifer downstream of the Banisveld (the Netherlands) landfill with uncontaminated groundwater, which revealed changes in microbial genomic content and activity. Banisveld landfill leachate contains mono-aromatic hydrocarbons and the assessment of natural attenuation of these compounds in the aquifer had been a focal point of research. In the contaminated groundwater, active microbial functions were the ones involved in degradation of complex carbon substrates and organic pollutants. We found that benzylsuccinate synthase genes-involved in the catabolism of toluene-were highly expressed close to the source of contamination, confirming the ongoing natural attenuation of organic mono-aromatic hydrocarbon pollution in this aquifer. Additionally, metatranscriptomes were indicative of phosphorus limitation that can constrain total microbial activity and agree with the low phosphate concentrations (

The municipal solid waste transfer stations (MSWTSs) affects both the environment and human health. The present study aimed to investigatethe Concentrations of BTEX (benzene, toluene, ethylbenzene and xylene) the important group of VOCs, in the ambient air of municipal solid waste transfer station (MSWTS) of Hamadan city and to estimate stochastic cancer and non-cancer risk for inhalation exposure to BTEX compounds by Crystal Ball software. The average produced amount of solid waste in Hamadan in 2109 has been estimated to be over 150,000 tons. The solid waste mostly consisted of a complex mixture containing kitchen/food waste (56.85%), consumed plastics (11.33%), paper (2.88%), glass (1.20%) and other materials (27.74%), which collected from households and commercial areas. The findings revealed that BETX concentration in the ambient air of MSWTS in summer is higher as compared to the spring season. The 95% percentile lifetime cancer risk (LCR) value for benzene was estimated to be 8 × 10−4, which is higher than the recommended standards (10−6). The obtained 95% percentile hazard quotient (HQ) value for xylene was found to be higher than the suggested value of 1. Also, the total cumulative value of the 95th percentile HQs for (toluene, ethylbenzene and xylene) TEX was obtained to be about 3.39, which is higher than the acceptable value of HQ. The results of sensitivity analysis for LCR of benzene and HQs of TEX disclosed that the parameter of pollutants concentration has the highest effect on risk's variance. According to the values of cancer and non-cancer risk assessment, that were higher than safe levels and the major contribution of pollutant concentration in sensitivity analysis, it is concluded that the implementation and development of technical and engineering control measures must be regarded as an essential target to reduce workers exposure to the pollutants and to decrease the concentration of the pollutant in the ambient air of MSWTS. [ABSTRACT FROM AUTHOR]

The toxic air pollutants such as benzene, toluene, ethylbenzene and xylene (BTEX) as well as asbestos are considered hazardous because of their role in adverse impacts on human health. Accordingly, this research was conducted to evaluate the levels, seasonal variations, spatial mapping, potential sources, and health risk assessment of BTEX compounds as well as asbestos fibres in the ambient air of Tehran. Air samples were collected by the NIOSH1501 method at 15 different sample stations from March 2018 to February 2019. Charcoal glass tube was used to collect samples and BTEX concentration was further determined using GC-FID method. The sampling of asbestos fibres was carried out via a low volume peripheral pump with analysis performed according to the NIOSH 7400 method via phase contrast microscopy (PCM). The findings showed that the mean±SD concentrations of ∑BTEX were 33.44 ± 11.77 and 59.97 ± 33.76 µg/m3 in warm and cold seasons, respectively. It was 1.46 × 10−3 and 2.31 × 10−3 fibre/ml for asbestos in the warm and cold seasons, respectively. The spatial mapping indicated that the maximum levels of both pollutants were observed in sampling sites S1, S11, and S15, which were located close to factories downtown (S1) and heavy traffic roads (S11 and S15). The mean inhalation lifetime cancer risk (LTCR) value for benzene was 1.64 × 10−5, which was higher than US EPA and WHO recommended limits. Further, the excess lifetime cancer risk (ELCR) suggested that the exposure to asbestos fibre in Tehran would cause the risk of developing cancer in 0.5 to 3.53 people per every 1000 individuals. Hence, much suitable managing strategies are required to control the concentration of these pollutants in the ambient air of Tehran. [ABSTRACT FROM AUTHOR]

The combustion of biogas which contains significant amounts of monoaromatic hydrocarbons, i.e. benzene, ethylbenzene, toluene, and xylene (BTEX) can cause many technological, environmental, and health problems. Therefore, in these studies, a new physical absorption method based on deep eutectic solvents (DES) consisting of monoterpenes and carboxylic acids was developed for BTEX removal. A total of 39 DES were synthesized, of which seven were selected based on their affinity to BTEX, favorable physicochemical properties, and "green" character. Detailed structural (i.e. 1H NMR, 13C NMR, and FT-IR) and physicochemical experiments (i.e. melting point, density, viscosity, and surface tension) were performed for the DES. Then, DESs were used for the absorption process in both the laboratory and enlarged scale. BTEX absorption was monitored using two methods, including "in-situ" gas chromatography, and "online" sensors matrices. The crucial absorption parameters i.e. type of DES, temperature, and regeneration possibility were carefully studied. The mechanism of BTEX absorption was explained using experimental spectroscopic techniques and theoretical analysis based on the COSMO-RS model. The obtained results indicate that Eucalyptol:Octanoic acid can selectively capture BTEX from a biogas mixture due to the formation of electrostatic interaction. DES absorption capacity is 53.96 mg/g, which is comparable with commercially available absorbents. • Novel green monoterpenes based deep eutectic solvents (DES). • Efficient and selective capture of BTEX from biogas using DES. • Environmentally friendly method for biogas purification. • Detailed information on physical absorption mechanism by DES. [ABSTRACT FROM AUTHOR]

BTEX species are abundant volatile organic compounds that are classified as main pollutants by several environmental protection agencies. In this study, a new 3D air pollution dispersion model with the capability of taking into account the BTEX's reactions was developed and evaluated. The Toxchem model is employed to estimate the amount of emitted BTEX from several area sources, followed by simulating the transport of the reactive species through a 3D model. Also, reduced mechanisms were developed, based on Master Chemical Mechanism (MCM), for the simulation of the atmospheric chemistry of BTEX. The application of the mechanism reduction method yielded a mechanism of 43 species and 45 reactions. Based on findings, the deviation of the reduced mechanism from the whole mechanism was < 4% throughout the simulation. In addition, the result showed that, during a 12 h period of simulation, the effect of the atmospheric chemical reaction on reducing the final concentration of benzene, toluene, ethylbenzene, m-xylene, o-xylene, and p-xylene was about 0.3, 1, 1.4, 5, 3.1, and 3.2%, respectively. Lastly, it was indicated that the estimated emission rates by Toxchem and simulated concentrations by the dispersion model were in good agreement with the reported experimental values. [ABSTRACT FROM AUTHOR]

Resolving three environmental challenges simultaneously—recycling bone waste, aggregation, oxidation of bare nZVI and benzene, toluene, ethylbenzene, and p-xylene (BTEX) contamination—was conducted by fabricating a highly stable and efficient activator of peroxymonosulfate. In this work, a novel heterogeneous catalyst, ostrich bone ash-supported nanoscale zero-valent iron (Fe0-OBA) prepared by pyrolysis of animal bones and reduced Fe2+ on the surface of it, was used for the activation of peroxymonosulfate (PMS). Advantageous properties such as extensive availability, low production cost, and high thermal stability make OBA an appealing carbonaceous material for heterogeneous catalysis. The TEM and SEM results revealed that the black ball-shaped nZVI particles were uniformly dispersed on the surface of OBA. The Fe0-OBA composite had a porous structure with a specific surface area of 109 m2 g−1 according to BET analysis. With BTEX as the refractory pollutant, the PMS-based Fe0-OBA system shows great degradation performance as compared to the homogeneous Fe2+/PMS system. The effects of various parameters, such as initial pH (2–9), temperature (25–45 °C), initial BTEX concentration (50–200 mg L−1), PMS dosage (0.5–1.25 mM), time of reaction (0–60 min), and Fe0-OBA dosage (0.5–5 g L−1) on the BTEX degradation, have been discussed in detail. The pseudo-first-order kinetic model can describe the BTEX degradation by the PMS-based Fe0-OBA system. The excellent stability of Fe0-OBA even after 10 years, while maintaining the degradation efficiency, shows the high potential of it in a wide range of practical applications. This study illustrated that Fe0-OBA could be an effective activator of PMS for the degradation of stubborn organic contaminants in water and wastewater. [ABSTRACT FROM AUTHOR]

Waste and wastewater containing hydrocarbons are produced worldwide by various oil-based industries, whose activities also contribute to the occurrence of oil spills throughout the globe, causing severe environmental contamination. Anaerobic microorganisms with the ability to biodegrade petroleum hydrocarbons are important in the treatment of contaminated matrices, both in situ in deep subsurfaces, or ex situ in bioreactors. In the latter, part of the energetic value of these compounds can be recovered in the form of biogas. Anaerobic degradation of petroleum hydrocarbons can be improved by various iron compounds, but different iron species exert distinct effects. For example, Fe(III) can be used as an electron acceptor in microbial hydrocarbon degradation, zero-valent iron can donate electrons for enhanced methanogenesis, and conductive iron oxides may facilitate electron transfers in methanogenic processes. Iron compounds can also act as hydrocarbon adsorbents, or be involved in secondary abiotic reactions, overall promoting hydrocarbon biodegradation. These multiple roles of iron are comprehensively reviewed in this paper and linked to key functional microorganisms involved in these processes, to the underlying mechanisms, and to the main influential factors. Recent research progress, future perspectives, and remaining challenges on the application of iron-assisted anaerobic hydrocarbon degradation are highlighted. [ABSTRACT FROM AUTHOR]

BTEX (benzene, toluene, ethylbenzene and xylenes) are considered as hazardous air pollutants in urban environment. The aim of this study was to measure BTEX concentration, analyze the ozone and secondary organic aerosol formation potentials of BTEX and assess its health risks for the first time in the Guangzhong Plain (GZP). BTEX samples were collected continuously in five cities in GZP using the gas chromatography-hydrogen flame ionization/mass spectrometry analysis system, from September 2017 to January 2018. Results showed that the average BTEX level was higher in autumn (50.16 ± 31.84 µg m−3) than in winter (15.08 ± 19.49 µg m−3) in GZP. Diurnal variation of BTEX exhibited higher values in nighttime (20:00–7:00) than that in daytime (8:00–19:00). Vehicle emission was the predominant source of BTEX; biomass, biofuels and coal burning can affect BTEX concentration in winter. The total ozone formation potential (OFP) of BTEX was 219.19 ± 155.79 µg m−3 in autumn and 64.78 ± 91.73 µg m−3 in winter with maximum potential by toluene. Toluene and xylenes contributed 81.58% and 77.18% of the total secondary organic aerosol formation potentials (SOAFP) in autumn and in winter, respectively. The value of HQ at five urban sites was < 1 indicating the non-carcinogenic risk is negligible for people residing near these areas. The lifetime cancer risk (LTCR) value of benzene inhalation (1.54 × 10−5–3.05 × 10−5) in GZP in autumn was higher than 1.0 × 10−6, representing a probable cancer risk. Much effort is required to control regional BTEX levels and mitigate their impact on environment and human health. [ABSTRACT FROM AUTHOR]

Oil exploration generates produced water that is characterized as hazardous and toxic waste. Produced water contains a mixture of various pollutants, including monoaromatic hydrocarbons BTEX (benzene, toluene, ethylbenzene, and xylene), compounds that are carcinogenic even in small concentrations. In this study, tannin iron complex (TA-FeIII), blended into polyethersulfone (PES) membrane was evaluated for the treatment of BTEX-containing wastewater. The membranes were fabricated using the non-solvent induced phase separation (NIPS) method and loading of the TA-FeIII complex on the membranes varied from 0-0.9 wt%. The fabricated membranes were characterized using various techniques such as scanning electron microscopy (SEM), water contact angle (WCA), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM) to check the surface morphology, hydrophilicity, surface functionality and surface roughness of the fabricated membranes, respectively. The TA-FeIII modified membranes showed increased pure water flux from 100 (PES 0) to ~150 (PES 0.9) L/(m2·h) at 100 kPa. The performance of the fabricated membranes was tested using 70 mg/L synthetic BTEX solution. Overall BTEX rejection > 70% was achieved at increasing TA-FeIII loadings compared to BTEX rejection < 65% for the pure PES membrane. Rejection of the BTEX compounds was mainly through the size exclusion mechanism. These modified TA-FeIII/PES UF membranes proved to be effective in the treatment of BTEX-containing water, and also have the potential to be applied in oily wastewater treatment. [ABSTRACT FROM AUTHOR]

In order to study the influence of freeze-thaw alternation process on biodegradation of BTEX in seasonal frozen soil area. The author took chernozem polluted by BTEX in Daqing area as the research object, through indoor simulation experiment, controlled - 15 °C ~ 5 °C, - 10 °C ~ 5 °C, - 5 °C ~ 5 °C and 5 °C, simulated freeze-thaw alternation and freezing process, combined with 16SrDNA DGGE technology to study the effect of different freezing factors Biodegradation and transformation of BTEX and change of microbial community structure. The results showed that the community structure of BTEX contaminated soil was affected by temperature, freezing and thawing frequency, freezing time and BTEX concentration. The results show that the change of microbial community structure under 5 °C low temperature is mainly controlled by the concentration of BTEX, and the microbial abundance is high under low concentration; the change of microbial community structure under freeze-thaw condition is affected by the triple effects of freeze-thaw temperature, freeze-thaw frequency and BTEX concentration. With the decrease of freeze-thaw temperature, the increase of freeze-thaw frequency, the increase of BTEX content, the decrease of microbial abundance and the increase of microbial evenness. Biodiversity studies showed that freeze-thaw temperature had the greatest impact on microbial community structure. When the temperature reached - 10 °C, the microbial community would not change. Stenotrophomonas, Arthrobacter sp. and uncultured Ethanoligenens were dominant in the environment containing BTEX under freeze-thaw conditions. [ABSTRACT FROM AUTHOR]

Harmful volatile organic compounds (VOCs) are present in drinking water due to anthropogenic activities, such as oil refining (e.g., benzene) and disinfection (e.g., the so-called trihalomethanes, THMs). Gas chromatography (GC)-based techniques are widely applied for analysis of these compounds in the laboratory but have some throughput drawbacks due to sample preparation and the extended analysis time (due to chromatographic separation). Selected ion flow tube mass spectrometry (SIFT-MS) is a direct-injection mass spectrometry (DIMS) technique that has potential to reduce sample preparation and analysis times through direct analysis of aqueous headspace with no preconcentration, drying, or other water management. This study applies headspace-SIFT-MS to the analysis of benzene, related petroleum aromatics, and THMs to evaluate the potential for enhanced sample throughput for drinking water analysis (10 samples per hour). Headspace-SIFT-MS achieved a limit of quantitation (LOQ) of 0.1 to 0.2 μg L−1 for benzene, toluene, ethylbenzene and xylenes (BTEX), and 1 to 2 μg L−1 for the THMs. These LOQs achieve the current European Union and United States regulatory limits but are higher than modern GC methods. Therefore, the potential application of SIFT-MS is envisaged to lie in rapid screening in the laboratory, or field-based real-time monitoring. [ABSTRACT FROM AUTHOR]

Toxic gaseous organic air pollutants such as benzene, toluene, ethylbenzene, and xylene isomers (m, p, and o-x) (BTEX) are considered hazardous due to its adverse impacts on human health and on climate change. This review identifies the major research questions addressed so far and the research gap in research articles, published between 2001 and 2022, focusing on the ambient BTEX concentrations in different locations in India along with its sources, ozone formation potential (OFP), and associated health risks. The ambient levels of BTEX were also compared with those of other Asian countries. A comparison of ambient BTEX levels with different microenvironments in India is also presented. BTEX concentrations were found in the range of 30.95 to 317.18 µg m−3 and multi-fold higher in urban environments than those measured in the rural air. In most reported studies, the order of occurrence of BTEX compounds was toluene > benzene > xylene isomers > ethylbenzene and winter had higher concentrations than in other seasons, including summer. As far as BTEX levels in classified areas of urban environments are concerned, traffic locations have shown the highest BTEX concentrations, followed by residential, commercial, and industrial locations. OFP indicated that xylene isomers and toluene contributed to ozone formation. The major gaps in reported studies on BTEX measurement are (1) source apportionment; (2) impact on lower tropospheric chemistry, human health, and climate change; and (3) removal techniques from air. [ABSTRACT FROM AUTHOR]

The oil pollutant in the Sava River aquifer in the residential area of Belgrade, Serbia was investigated in order to analyze the extent, origin and spatial distribution of the pollution, with the aim to estimate potential human health risks from exposure to the compounds detected. Analytical methods indicated that the dominant compounds in this oil pollutant were gasoline range organic compounds. Benzene, toluene, ethylbenzene and xylenes (BTEX) were identified as compounds of concern and quantified by headspace gas chromatography. The concentrations of benzene measured at all sampling points were higher than the remediation value while the maximum concentrations of BTEX quantified were among the highest concentrations of these compounds reported in the petroleum-contaminated aquifers in the world. The assessment of the human health risks from exposure to BTEX-covered industrial scenario for adult receptors and residential scenario for adult receptors and children. The exposure routes analyzed were dermal contact with and ingestion of contaminated water, considering both cancer and non-cancer effects. The analysis of the lifetime incremental cancer risk indicated the potential for adverse health effects for human exposure at the investigated location, and because of that it was interpreted as an unacceptable risk level or risks of high priority which required immediate consideration for remedial measures at this location. A complete set of mitigation measures was proposed including: groundwater decontamination treatment, installation of filters for tap water, development of the system for monitoring of BTEX in the groundwater and development of the emergency response capacities at this location. [ABSTRACT FROM AUTHOR]

Spills of petroleum or its derivatives in the environment lead to an enrichment of microorganisms able to degrade such compounds. The interactions taking place in such microbial communities are complex and poorly understood, since they depend on multiple factors, including diversity and metabolic potential of the microorganisms and a broad range of fluctuating environmental conditions. In our previous study, a complete characterization, based on high-throughput sequencing, was performed in a jet-fuel plume using soil samples and in in-situ microcosms amended with hydrocarbons and exposed for 120 days. Herein, we propose a metabolic model to describe the monoaromatic hydrocarbon degradation process that takes place in such jet-fuel-contaminated sites, by combining genome-centered analysis, functional predictions, and flux balance analysis (FBA). In total, twenty high/medium quality MAGs were recovered; three of them assigned to anaerobic bacteria (Thermincolales, Geobacter and Pelotomaculaceace) and one affiliated to the aerobic bacterium Acinetobacter radioresistens, potentially the main players of hydrocarbon degradation in jet-fuel plumes. Taxonomic assignment of the genes indicated that a putative new species of Geobacteria has the potential for anaerobic degradation pathway, while the Pelotomaculaceae and Thermincolales members probably act via syntrophy oxidizing acetate and hydrogen (fermentation products of oil degradation) via sulfate and/or nitrate reduction., Competing Interests: Declarations Competing interest The authors declare no competing interests. Ethical approval The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Petroleum hydrocarbons, including both aliphatic (gasoline, mineral oil) and aromatic compounds (BTEX), are known for their harmful effects on ecosystems and human health. Despite many studies, large-scale treatment of contaminated soils continues to be challenging, especially at lower temperatures. The use of metabolically-versatile, psychrotolerant, cold-active microorganisms, seems a promising, cost-effective and eco-friendly solution to boost remediation rates. In this study, a suitable microbial consortium was prepared and tested both in lab- and pilot-scale. To achieve the best bioremediation results, bacterial strains were isolated from BTEX-contaminated soil and then tested for the desired traits over a wide range of conditions. Of 5 preselected strains, 3 Pseudomonas strains capable of denitrification and aerobic/anaerobic degradation of hydrocarbons (up to 41.53±7.39 %), further characterized by a broad temperature (4-37 °C), pH (3-4 to 11) and salinity (0-8 %) tolerance, as well as resistance to freezing, were selected. Physiological studies were supported by genetic analyses, which indicated the presence of both alkB and xylM genes, and excluded similarity of the strains to the known opportunistic pathogens. To further confirm the applicability of the consortium, lab-scale analyses were followed by comprehensive pilot-scale tests on ~5 m 3 biopile/biocell, at different conditions. The results revealed increased efficacy of the consortium in bioremediation, when compared to biostimulated indigenous strains, for volatile hydrocarbons (93 % vs 88 %) and mineral oil (23 % vs 15 %), as well as 175 % and 136 % acceleration of remediation for the respective compounds in terms of time needed to complete the process. Moreover, the high survivability and metabolic activity of the consortium at different temperatures indicate the possibility of its year-round use for bioremediation of soil contaminated with petroleum hydrocarbons. The study proves the potential of specialized bacteria in the removal of pollutants, and emphasizes the role of bio-based strategies in addressing complex environmental challenges and remediation of contaminated sites., Competing Interests: Declaration of competing interest The authors declare no competing interests exist., (Copyright © 2024. Published by Elsevier B.V.)

The simultaneous oxidation performance of benzene, toluene, ethylbenzene, and xylene (BTEX) by nanoscale calcium peroxide particles (nCaO2) activated with ferric ions (Fe(III)) and the mechanism of the enhancement of BTEX degradation by L-cysteine (L-cys) were investigated. The batch experimental results showed that the nCaO2/Fe(III)/L-cys process was effective in the destruction of BTEX in both ultrapure water and actual groundwater. A proper amount of L-cys could enhance BTEX degradation due to the promotion of Fe(II)/Fe(III) redox cycles by the participation of L-cys, but an excessive presence of L-cys would cause inhibition. Adding 1.0 mM L-cys to the nCaO2/Fe(III) system, the concentration of Fe(II) increased to 1.15 mM instantly. Simultaneously, the yield of HO• produced by the 1.0 mM L-cys-containing system was 0.066 mM at 180 min reaction, higher than that without L-cys (0.049 mM). When excess L-cys (5.0 mM) was added to the system, the amount of Fe(II) increased to 3.73 mM because excessive L-cys caused a large amount of Fe(III) in the system to be reduced. However, the yield of HO• decreased to 0.043 mM since excessive Fe(II) could conversely scavenge HO• to produce Fe(III) again. EPR tests and quenching results indicated that HO• was the dominant reactive species in the nCaO2/Fe(III)/L-cys system. For the removal of BTEX, the optimal molar ratio of nCaO2/Fe(III)/L-cys was 10.5/20/1 based on calculation by response surface methodology (RSM). Finally, the BTEX destruction pathway was proposed according to the detected intermediates by liquid chromatography-mass spectrometry (LC-MS). HIGHLIGHTS nCaO2/Fe(III) system with L-cysteine (L-cys) was applied to remediate mixed contaminants.; A suitable amount of L-cys promoted redox cycling (Fe(III) → Fe(II)).; The mechanism of enhancing or inhibiting hydroxyl radical generation was investigated.; Proposed BTEX destruction pathway in the nCaO2/Fe(III)/L-cys system.; nCaO2/Fe(III)/L-cys system was recommended for BTEX-contaminated actual groundwater remediation.;

A gasolina possui em sua composição mais de 200 substâncias potencialmente tóxicas, entre elas, o benzeno, tolueno, etilbenzeno e xilenos (BTEX). Esses agentes poluidores, quando vazados em postos de gasolina, encontram-se, inicialmente, na Zona Não Saturada nas formas adsorvidas e de vapor; em contato com a fase aquosa, se dissolvem parcialmente e atingem as regiões mais profundas, contaminando as águas subterrâneas. Dentre os tratamentos para remediação, destacam-se os processos oxidativos: reagente Fenton, peróxido de hidrogênio, permanganato e persulfato, tratados neste trabalho. A aplicação dessas técnicas de descontaminação promove total degradação de uma grande variedade de substâncias perigosas, resultando em compostos inócuos como gás carbônico e água. Entretanto, na maioria das vezes, sua aplicação leva a efeitos secundários indesejáveis ao meio ambiente como, por exemplo, a liberação de íons metálicos tóxicos. Visando estudar as alterações no solo e na água, foram realizados experimentos laboratoriais utilizando um Latossolo artificialmente impactado por gasolina e tratado com os agentes oxidativos (Fenton, peróxido de hidrogênio, persulfato de sódio e permanganato de potássio). Verificou-se que os tratamentos oxidativos resultam em diminuição do pH, redução dos teores de bases trocáveis e, por se tratar de processos pouco seletivos, ocasionam a degradação da matéria orgânica natural do solo. Essas alterações favorecem a dessorção de íons metálicos que são liberados para a fase aquosa em concentrações que excedem até centenas de vezes o limite estabelecido pela legislação, afetando o meio ambiente e alterando a qualidade das águas, tornando-as inadequadas para o consumo humano.

Members of the genus Pseudomonas are known to be widespread in hydrocarbon contaminated environments because of their remarkable ability to degrade a variety of petroleum hydrocarbons, including BTEX (benzene, toluene, ethylbenzene and xylene) compounds. During an enrichment investigation which aimed to study microaerobic xylene degradation in a legacy petroleum hydrocarbon-contaminated groundwater, a novel Gramstain-negative, aerobic, motile and rod-shaped bacterial strain, designated as MAP12T was isolated. It was capable of degrading benzene, toluene, meta- and para- xylene effectively under both aerobic and microaerobic conditions. The 16S rRNA gene sequence analysis revealed that strain MAP12T belongs to the genus Pseudomonas, with the highest 16S rRNA gene similarity to Pseudomonas linyingensis LYBRD3-7T (98.42%), followed by Pseudomonas sagittaria JCM 18195T (98.29%) and Pseudomonas alcaliphila JCM 10630T (98.08%). Phylogenomic tree constructed using a concatenated alignment of 92 core genes indicated that strain MAP12T is distinct from any known Pseudomonas species. The draft genome sequence of strain MAP12T is 4.36 Mb long, and the G+C content of MAP12T genome is 65.8%. Orthologous average nucleotide identity (OrthoANI) and digital DNA–DNA hybridization (dDDH) analyses confirmed that strain MAP12T is distinctly separated from its closest neighbors (OrthoANI < 89 %; dDDH < 36%). Though several members of the genus Pseudomonas are well known for their aerobic BTEX degradation capability, this is the first report of a novel Pseudomonas species capable of degrading xylene under microaerobic conditions. By applying genome-resolved metagenomics, we were able to partially reconstruct the genome of strain MAP12T from metagenomics sequence data and showed that strain MAP12T was an abundant member of the xylene-degrading bacterial community under microaerobic conditions. Strain MAP12T contains ubiquinone 9 (Q9) as the major respiratory quinone and diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine as major polar lipids. The major cellular fatty acids of strain MAP12T are summed feature 3 (C16:1ω6c and/or C16:1ω7c), C16:0 and summed feature 8 (C18:1ω6c and/or C18:1ω7c). The results of this polyphasic study support that strain MAP12T represents a novel species of the genus Pseudomonas, hence the name of Pseudomonas aromaticivorans sp. nov. is proposed for this strain considering its aromatic hydrocarbon degradation capability. The type strain is MAP12T (=LMG 32466, =NCAIM B.02668). [ABSTRACT FROM AUTHOR]

Oil leakage occurs at fuel service stations due to improper storage, which pollutes soil and, subsequently, can reach the groundwater. Many compounds of petroleum-derived fuels pose hazards to aquatic systems, and so must be treated to guarantee clean and safe consumption, which is a right proposed by the United Nations in their Sustainable Development Goal 6 (SDG 6: Clean Water and Sanitation). In this study, contaminated groundwater with emerging pollutants by petroleum-derived fuel was electrochemically treated in constantly mixed 0.5 L samples using three different anodes: Ni/BDD, Ti/Pt, Ti/RuO2. Parameters were investigated according to chemical oxygen demand (COD), energy consumption analysis, by applying different electrodes, current densities (j), time, and the use of Na2SO4 as an electrolyte. Despite a similar COD decrease, better degradation was achieved after 240 min of electrochemical treatment at Ti/RuO2 system (almost 70%) by applying 30 mA cm−2, even without electrolyte. Furthermore, energy consumption was lower with the RuO2 anode, and greater when 0.5 M of Na2SO4 was added; while the order, when compared with the other electrocatalytic materials, was Ti/RuO2 > Ti/Pt > Ni/BDD. Thereafter, aiming to verify the viability of treatment at a large scale, a pilot flow plant with a capacity of 5 L was used, with a double-sided Ti/RuO2 as the anode, and two stainless steel cathodes. The optimal conditions for the effective treatment of the polluted water were a j of 30 mA cm−2, and 0.5 M of Na2SO4, resulting in 68% degradation after 300 min, with almost complete removal of BTEX compounds (benzene, toluene, ethyl-benzene, and xylene, which are found in emerging pollutants) from the water and other toxic compounds. These significant results proved that the technology used here could be an effective SDG 6 electrochemical-based solution for the treatment of groundwater, seeking to improve the quality of water, removing contaminants, and focusing on Brazilian environmental legislations and, consequently, converting pollutants into effluent that can be returned to the water cycle. [ABSTRACT FROM AUTHOR]

Among the several ways used in wastewater treatment, the photocatalysis process is a more novel and alternative process that is increasingly employed in recent years. This work aims to improve the performance of the photocatalyst process by using air bubbles in removing the BTEX from produced water as an indicator of process efficiency. The study also shows the effect of influencing factors (pH and residence time) on the photocatalysis process. The study was done in a rectangular column with dimensions of 200 mm width, 30 mm depth, and 1500 mm height. Commercial titanium oxide (TiO2) coated on a plate by the varnish was used as a source of the photocatalyst. The experiment was carried out under different values of gas flow rate (0-3 L/min) to evaluate its effect on the photocatalyst process, the effect of other variables of pH (3-11), and irradiation time (30-120) min was also studied. A new method of the coating was adopted by using an alumina plate with varnish as an adhesive. The characteristics results show that the coated plate has hydrophilic properties and that there is no significant change in the crystal structure of the TiO2 nanoparticles and the varnish before and after 60 h of the photocatalytic process, indicating that the plate is still effective after 60 h usage under different conditions. The results also show that the introduction of air bubbles enhances the removal efficiency of BTEX significantly and the best removal effectiveness of BTEX was 93% when pH = 5 after 90 min and 90% when pH = 3 after 120 min. The removal rate also reached 86% when pH = 7 after 120 min all at a flow rate of 3 L/min. The percentage of removal decreased at pH = 9 and 11, reaching 64% and 50%, respectively after 120 min and a flow rate of 3 L/min. [ABSTRACT FROM AUTHOR]

The aim of this paper is to quantify the amounts of volatile organic compounds (VOCs) emitted from a coke oven in a steel plant in Taiwan and estimate the emission factors of VOCs using an innovative sampling technique. The identification of VOCs emissions was referred to in the AP-42 report issued by the USEPA and the field measurement data of fugitive emissions. VOCs were sampled using a self-designed closed sampling system. A total of six emission points, including quenching emissions, charge lid emissions, combustion stack emissions, door emissions, charging emissions, and coke pushing emissions, were identified in the coking process after comparing with the report of AP-42, and the emission factor of VOCs was 0.030 kg/ton-coke. It showed that the emission factor of VOCs via field measurement was approximately 56% of that reported by Taiwan EPA. Therefore, VOCs emissions estimated by the Taiwan EPA would be highly overestimated than those from the coke oven in the site. [ABSTRACT FROM AUTHOR]

Persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides were measured in water samples from six sites on the Aoös River in southern Albania via gas chromatography. Samples were collected in September 2017 (fall) and March 2018 (spring), before and after heavy flooding of the river in December 2017, respectively. The total PCBs lowest concentration increased from 0.6 µg L−1 to 0.62 µg L−1 and highest concentration increased from 32.64 µg L−1 to 36.57 µg L−1, respectively before and after heavy floods. The total BTEX lowest concentration increased from 1.6 µg L−1 to 1.82 µg L−1 and total highest concentration increased from 45.4 µg L−1 to 49.32 µg L−1. Pesticides total lowest concentration increased from 1.37 µg L−1 to 1.53 µg L−1 and highest concentration increased from 269.57 µg L−1 to 289.26 µg L−1. In contrast, the total PAH lowest concentration remained constant 0.01 µg L−1 and the highest concentration decreased from 0.45 µg L−1 to 0.25 µg L−1. Concentrations of PCBs, BTEX and Pesticides increased after winter floods in 2017, while the concentration of PAH decreased. This study was the first to investigate the seasonal variability of various POPs in the Aoös River. I found that the levels of the selected POPs were higher than the recommended standard values, suggesting significant pollution of the river, particularly after the occurrence of winter flood events. [ABSTRACT FROM AUTHOR]

Exposure to indoor air pollutants is one of the primary environmental health stressors, especially given that people in developed economies tend to spend approximately 80-90% of their time within enclosed living spaces. Concentrations of indoor air pollutants are determined by the ability of outdoor source pollutants to infiltrate indoors and emissions from indoor sources such as building materials, and furniture. The variability of species and the levels of contamination within and between different indoor microenvironments can be very wide and this poses real problems for modelling and exposure estimation. Personal exposure levels are likely to vary even more widely given differences between and within individuals in behaviour and activities. The aim of this study is to assess the negative impact on human health of various chemical contaminants in schools and kindergartens in Southeast Bulgaria. The studies in this paper cover the most vulnerable groups of residents between 5 years and 15 years old. The evaluation is based on a web based INTERA computational platform (http://www.intera. cperi.certh.gr). The data shows that the impact on boys is most pronounced for the inhabitants of the site in the village Karamantsi (Mineralni Bani municipality, region of Haskovo), followed by secondary schools in Haskovo and Kardzhali, which achieve doses up to 8.1-17 pg.m-3. The measures calculated by the platform show that the main sources are organic carbonyl compounds found in building materials including new coverings. It also found seasonal variability with higher levels observed in warmer months. [ABSTRACT FROM AUTHOR]

A series of Y zeolites with different pore properties was prepared as a support for hydrocracking catalysts for the production of BTEX (benzene, toluene, ethyl-benzene, and xylene) from tetralin. Some important characterizations, including N2 adsorption–desorption, NH3-TPD, Py-IR, and HRTEM, were applied to obtain the properties of different catalysts. Meanwhile, the tetralin hydrocracking performances of those catalysts were investigated on a high-pressure fixed-bed microreactor. The results showed that Si/Al ratio is the core property of zeolites and that the increase in the Vmicro/Vmeso of zeolites could facilitate the formation of BTEX products by hydrocracking tetralin. The method of hydrocracking tetralin was proposed. It was also found that the hydrogenation–cracking path was controlled by aromatic saturation thermodynamics, and strong acidity aided the backward shift of equilibrium temperature. [ABSTRACT FROM AUTHOR]

The study investigated the emissions of volatile organic compounds (VOCs) from a mining soil amended with sewage sludge and irrigated with wastewater with or without tomato plants. The aim is to find out whether amendment and irrigation change VOC emissions from the soil and whether tomato changes emissions compared to uncultivated soil. Soil and plant experiments were done in assembled pots. All pots were placed inside a closed glass chamber inside an isolated and windowless room. Experiments with soil without plants were done independently from experiments with soil and plants. An aspirating pump coupled with Tenax adsorbent tubes was used for sampling of VOCs emitted from pots. Volatile organic compounds trapped in the tubes were quantified by gas chromatography–mass spectrometry detection. The study detected a total of nine VOCs emitted from the polluted soil: benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, styrene, benzene-1,2,4-trimethyl and tetrachloroethylene, among which the most abundant were toluene, m-xylene and styrene. Differences between pots with or without amendments (C and A-pots) showed a general tendency to a decline of VOCs emissions in the mining soil amended with sewage sludge. Plants contributed to increase significantly the emissions of all VOCs in both A and C-pots. The soil amended with sewage sludge reduced the emission of VOCs: styrene in pots without plants and benzene and xylenes in pots with plants. Tomato plants contributed to increase significantly the emissions of all VOCs except styrene in both amended and non-amended soils.Article Highlights: The addition of sewage sludge to a contaminated soil reduces atmospheric emissions of VOCs. Growing tomato plants in soil increases emissions of soil pollutants. Repeated irrigation of soils with wastewater is a higher source of soil contamination by VOCs than sludge. The application of tomato plants is useful for soil remediation, but is not recommended for food use. The plants contribute to significant increases in benzene, toluene and ethylbenzene emissions. [ABSTRACT FROM AUTHOR]

Cases of oil spillage and leakage in marine environments are increasing, and generating a need to quickly assess the presence of these contaminants in seawater. This work aims to estimate the concentrations of benzene, toluene, ethylbenzene and xylenes (BTEX) dissolved in seawater in cases of oil spillage using experimental factorial planning. The study factors were oil °API and oil/seawater contact time after spillage. The models obtained were able to satisfactorily estimate BTEX concentrations, with accuracy greater than 99.3% within the ranges studied, with R² correlation coefficients ranging from 0.992 to 0.997. The models presented forecast efficiency higher than 88%, with low relative errors, ranging from 0.1% to 12%. The concentrations of benzene dissolved in seawater found experimentally with only one hour of spillage, for the two types of oils studied, were higher than allowed by Brazilian legislation, demonstrating real environmental risk in cases of spillage of these types of oil into the sea. These results can corroborate the development of a risk assessment in oil spills within the studied ranges and serve as a useful analytical tool for emergencies. [ABSTRACT FROM AUTHOR]

Urbanisation development affects urban vegetation both directly and indirectly. Since this process usually involves a dramatic change in land use, it is seen as likely to cause ecological pressure on local ecosystems. All forms of human activity, including urbanisation of areas close to residential buildings, significantly impact air quality. This study aims to identify and characterise different measurement solutions of VOCs, allowing the quantification of total and selective compounds in a direct at source (in situ) manner. Portable devices for direct testing can generally be divided into detectors, chromatographs, and electronic noses. They differ in parameters such as operating principle, sensitivity, measurement range, response time, and selectivity. Direct research allows us to obtain measurement results in a short time, which is essential from the point of view of immediate reaction in the case of high concentrations of tested compounds and the possibility of ensuring the well-being of people. The paper also attempts to compare solutions and devices available on the market and assess their application. [ABSTRACT FROM AUTHOR]

Abstract Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O2 conc. 8 mg l−1) and micro-aerobic/oxygen-limited (O2 conc. 0.5 mg l−1) conditions using either individual (8 mg‧l−1) or a mixture of compounds (~ 1.3 mg‧l−1 of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l−1 per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.

Members of the genus Pseudomonas are known to be widespread in hydrocarbon contaminated environments because of their remarkable ability to degrade a variety of petroleum hydrocarbons, including BTEX (benzene, toluene, ethylbenzene and xylene) compounds. During an enrichment investigation which aimed to study microaerobic xylene degradation in a legacy petroleum hydrocarbon-contaminated groundwater, a novel Gram-stain-negative, aerobic, motile and rod-shaped bacterial strain, designated as MAP12T was isolated. It was capable of degrading benzene, toluene, meta- and para- xylene effectively under both aerobic and microaerobic conditions. The 16S rRNA gene sequence analysis revealed that strain MAP12T belongs to the genus Pseudomonas, with the highest 16S rRNA gene similarity to Pseudomonas linyingensis LYBRD3-7T (98.42%), followed by Pseudomonas sagittaria JCM 18195T (98.29%) and Pseudomonas alcaliphila JCM 10630T (98.08%). Phylogenomic tree constructed using a concatenated alignment of 92 core genes indicated that strain MAP12T is distinct from any known Pseudomonas species. The draft genome sequence of strain MAP12T is 4.36 Mb long, and the G+C content of MAP12T genome is 65.8%. Orthologous average nucleotide identity (OrthoANI) and digital DNA–DNA hybridization (dDDH) analyses confirmed that strain MAP12T is distinctly separated from its closest neighbors (OrthoANI < 89 %; dDDH < 36%). Though several members of the genus Pseudomonas are well known for their aerobic BTEX degradation capability, this is the first report of a novel Pseudomonas species capable of degrading xylene under microaerobic conditions. By applying genome-resolved metagenomics, we were able to partially reconstruct the genome of strain MAP12T from metagenomics sequence data and showed that strain MAP12T was an abundant member of the xylene-degrading bacterial community under microaerobic conditions. Strain MAP12T contains ubiquinone 9 (Q9) as the major respiratory quinone and diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine as major polar lipids. The major cellular fatty acids of strain MAP12T are summed feature 3 (C16:1ω6c and/or C16:1ω7c), C16:0 and summed feature 8 (C18:1ω6c and/or C18:1ω7c). The results of this polyphasic study support that strain MAP12T represents a novel species of the genus Pseudomonas, hence the name of Pseudomonas aromaticivorans sp. nov. is proposed for this strain considering its aromatic hydrocarbon degradation capability. The type strain is MAP12T (=LMG 32466, =NCAIM B.02668).

Volatile organic compounds including benzene, toluene, ethyl benzene, and xylene (BTEX) in the atmosphere have severe health and environmental implications. These variables are trace elements in the atmosphere. There are not enough measurement and analysis studies related to atmospheric BTEX variation globally, and studies are even less in developing countries like India. The present study analyses BTEX variations over an eastern Indian site, Bhubaneswar. The continuous measurement of BTEX is first of its kind over Bhubaneswar. The study analyses 2 years of BTEX data (2017–2018), and attempts to find the relation with meteorological parameters, the significance of the ratio between components, along with the analysis of transported air masses. To account for the pattern of emissions in association with BTEX variability over Bhubaneswar, we have also developed emission details from the transportation sector for the year 2018 and analyzed the emission patterns of CO and NOx for the year 2018. The results indicated that BTEX concentrations are maintained at the site via transportation from other regions, with significant local generation of BTEX, which is smaller in comparison to the transported emission.

The widespread application of the hydrocarbons benzene, toluene, ethylbenzene and xylene (BTEX) has led to their consideration as major aquatic environmental pollutants, and exposure to these hydrocarbons has become a serious concern given their detrimental health effects on aquatic species. We investigated in the present study the impact of chronic exposure to BTEX on the testis of the freshwater leech Erpobdella johanssoni. The results revealed that BTEX induced severe histological alterations revealed by vacuolar degeneration in the spermatogenic cysts, and a complete loss of normal cysts was observed. The cytophore was grossly destroyed, and extensive necrosis and detached germ cells from cytophore were observed. Interestingly, BTEX exposure induced a significant increase in malondialdehyde (MDA) levels by 85.71% in the testicular tissue of treated leeches compared to the control (P

The aim of this study was to compare the concentrations of the benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in the urine of smokers and the control group considering the role of age, weight, job, history of waterpipe and cigarette smoking, and driving time. The chemicals in the urine of 99 smokers and 31 nonsmokers were extracted by liquid-liquid extraction method and their concentrations were measured by liquid injection GC/MS. The mean concentration of benzene, toluene, ethylbenzene, m-xylene, o-xylene, p-xylene, and total BTEX in waterpipe smokers were found to be 471.40, 670.90, 127.91, 167.64, 90.62, 46.04, and 1574.50 ng/g. creatinine, respectively. For the waterpipe&cigarette smokers, the concentration of the compounds were 708.00, 959.00, 146.40, 192.50, 93.30, 53.07, and 2152.00 ng/g.creatinine, respectively. For nonsmokers the concentrations of these compounds were 88.12, 140.40, 36.68, 57.29, 31.53, 26.21, and 380.30 ng/g.creatinine, respectively. Driving time, waterpipe smoking and cigarette smoking were positively associated with BTEX concentration (p

Abstract Background and Aim :The release of volatile organic compounds from stationary and mobile sources increases the concentration of these compounds in the environment. These compounds are potentially hazardous to the environment and human health. The selection of management and engineering systems has become essential for controlling the release of these pollutants. The aim of this study was to use an advanced catalytic ozonation process to reduce the concentration of these pollutants in industrial emissions. Materials and Methods:In this experimental study, the ozonation process in the presence of a catalyst bed containing ZnO nanocomposites coated on zeolite was used to treat the air contaminated with BTEX compounds as indicators of volatile organic compounds on a laboratory scale. In this study, the synthesis of nanocomposites was done using the chemical co-deposition method. SEM, XRD, BET, and FT-IR analyses were performed to investigate the structural properties of the nanocomposites. The initial concentrations of BTEX (50-200 ppm), the flow of the polluted air (5-20 l/h), humidity (0-75%), and ozone dose (0.25-1 g/h) were studied. The concentration of the BTEX compounds was measured by a Gas Chromatography (GC) device according to the NIOSH Guideline 1501. Results:The results of SEM, XRD, BET, and FT-IR indicated the proper synthesis of nanocomposites. Based on the laboratory results, the optimal process conditions were the initial concentration of pollutants equal to 50 ppm, the inlet flow rate of polluted air equal to 5 l/h, relative humidity of 25-35%, and the inlet concentration of ozone equal to 1 g/h. Under these conditions, the removal efficiencies of benzene, toluene, ethylbenzene, and xylene were 98, 96, 92, and 91%, respectively. Simple ozonation and adsorption processes had lower efficiencies than catalytic ozonation and the synergistic effect of the process was evident. Conclusion:Based on the obtained results, the process has the ability to reduce the concentration of BTEX compounds to the specified standards. This process can be used to treat polluted air in BTEX emitting industries that threaten human health and the environment. Article type:Research article Keywords: Volatile Organic Compounds; BTEX; Nanocomposite; Zinc Oxide; Ozone; Polluted Air

Membrane fouling generated by small molecular-weight aromatic compounds with poor biodegradability is a major barrier to advanced petrochemical wastewater treatment using nanofiltration (NF) technology. In this study, the fouling behavior of ten BTEX with different substituent existing in petrochemical wastewater on the NF membrane was systematically investigated. By examining the effect of the number, position, and type of substituents on the permeability of NF membranes and membrane resistance analysis, combined with XDLVO theory and correlation analysis, we found that stronger dipole-dipole interactions of BTEX with higher polarity and hydrogen bonding effects between substituents and the membrane surface were verified to be the main forces driving the attachment to the surface of membranes. Furthermore, by analyzing the effect of common inorganic ions in petrochemical wastewater on membrane fouling, it was found that electron-donating substituents (-CH 3 , -C 2 H 5 , and -NH 2) enhanced the electron cloud density of the benzene ring, a process that exacerbated membrane fouling by strengthening electrostatic interactions between the benzene ring and Ca2+ ions. The fouling potential of electron-withdrawing substituted (-NO 2 , -OH) BTEX exhibited the opposite trend. Overall, this study provides a theoretical basis for developing effective membrane fouling control strategies in NF advanced treatment of petrochemical wastewater. Aromatic chemicals in petrochemical effluent are difficult to degrade, and their accumulation will cause significant harm to humans and ecological systems. Determine the composition of small molecule BTEX in petrochemical wastewater, gain an in-depth comprehension of the membrane fouling behavior of nanofiltration membrane filtration, identify the primary forces causing irreversible membrane surface fouling using experimental data and model fitting, and propose viable anti-fouling membrane modification strategies. Establish a technical foundation for membrane fouling management in the long-term operation of petrochemical wastewater membrane treatment. [Display omitted] • Systematically evaluated the NP fouling behavior of ten BTEX present in petrochemical wastewater. • Type of substituents may emerge as a potentially critical determinant of membrane fouling. • XDLVO theory and correlation analysis identified polarity and H-bonding as key factors in NF treatment of BTEX. • Ca2+ exacerbated NP membrane fouling by BTEX with electron-donating substituents. [ABSTRACT FROM AUTHOR]

Soil–water pollution is of serious concern worldwide. There is a public outcry against the continually rising problems of pollution to ensure the safest and healthiest subsurface environment for living beings. A variety of organic pollutants causes serious soil–water pollution, toxicity and, therefore, the removal of a wide range of organic pollutants from contaminated matrix through the biological process rather than physico-chemical methods is an urgent need to protect the environment and public health. Being an ecofriendly technology, bioremediation can solve the problems of soil–water pollution due to hydrocarbons as it is a low-cost and self-driven process that utilises microorganisms and plants or their enzymes to degrade and detoxify pollutants and thus, promote sustainable development. This paper describes the updates on the bioremediation and phytoremediation techniques which have been recently developed and demonstrated at the plot-scale. Further, this paper provides details of wetland-based treatment of BTEX contaminated soils and water. The knowledge acquired in our study contributes extensively towards understanding the impact of dynamic subsurface conditions on engineered bioremediation techniques.

This study aims to identify sources of groundwater contamination in a refinery area using integrated compound-specific stable isotope analysis (CSIA), oil fingerprinting techniques, hydrogeological data, and distillation analysis. The investigations focused on determination of the origin of benzene, toluene, ethylbenzene, and xylenes (BTEX), and aliphatic hydrocarbons as well. Groundwater and floating oil samples were collected from extraction wells for analysis. Results indicate presence of active leaks in both the northern and southern zones. In the northern zone, toluene was found to primarily originate from oil products like aviation turbine kerosene (ATK or aviation fuel), kerosene, regular gasoline, and diesel fuel. Additionally, stable isotope ratios of carbon and hydrogen for ethylbenzene, o-xylene (ortho xylene) and p-xylene (para xylene) in zone A suggested the pollution originated from gasoline within the northern zone. The origin of super gasoline (with higher octane) identified in southern zone using δ13C and δ2H values of toluene in the floating oil and groundwater samples. Further, biodegradation of toluene likely occurred in southern zone according to δ13C and δ2H. The findings underscore the critical importance of integrating CSIA and fingerprinting techniques to effectively address the challenges of source identification and relying solely on each method independently is insufficient. Accordingly, comparing the GC-MS results of floating oil samples with ATK and jet fuel (JP4) standards can be effectively utilized for source differentiation. However, this method showed no practical application to distinguish different types of diesel or gasoline. The accuracy and reliability of source identification of BTEX compounds may significantly improve when hydrogeological data incorporates with stable isotopes analysis. Additionally, the results of this study will elevate the procedures for fuel-related contaminants source identification of the polluted groundwater that is crucial to develop effective remediation strategies. • The study aimed to differentiate the specific types of diesel and gasoline with benzene, toluene, ethylbenzene, and xylenes compounds (BTEX) in a heavily-polluted aquifer. • The major method was the integration of compound-specific isotope analysis (CSIA) along with oil fingerprinting techniques and hydrogeological data analysis. • Determination of toluene origins from gasoline and diesel in zone A and super gasoline in zone B. • This study emphasizes the critical importance of integrating CSIA and fingerprinting techniques to accurately identify sources of contamination in complex environments. [ABSTRACT FROM AUTHOR]

The application of Monitored Natural Attenuation (MNA) technology has been widespread, while there is a paucity of data on groundwater with multiple co-contaminants. This study focused on high permeability, low hydraulic gradient groundwater with co-contamination of benzene, toluene, ethylbenzene, and xylenes (BTEX), chlorinated aliphatic hydrocarbons (CAHs), and chlorinated aromatic hydrocarbons (CPs). The objective was to investigate the responses of microbial communities during natural attenuation processes. Results revealed greater horizontal variation in groundwater microbial community composition compared to vertical variation. The variation was strongly correlated with the total contaminant quantity (r = 0.722, p < 0.001) rather than individual contaminants. BTEX exerted a more significant influence on community diversity than other contaminants. The assembly of groundwater microbial communities was primarily governed by deterministic processes (βNTI < −2) in high contaminant concentration zones, while stochastic processes (|βNTI| < 2) dominated in low-concentration zones. Moreover, the microbial interactions shifted at different depths indicating the degradation rate variation in the vertical. This study makes fundamental contribution to the understanding for the effects of groundwater flow and material fields on indigenous microbial communities, which will provide a scientific basis for more precise adoption of microbial stimulation/augmentation to accelerate the rate of contaminant removal. [Display omitted] • Groundwater microbial community composition vary more horizontally. • Contaminants concentration correlate more with microbial community than their risk. • BTEX impacts community diversity more than CAHs in multi-contaminated groundwater. • Stochasticity increases progressively with decreasing contamination. • Groundwater microbial interactions vary across different depths. [ABSTRACT FROM AUTHOR]

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]

• Microwave-assisted pyrolysis tandem catalytic reforming system was developed. • ZSM-5 with different SiO 2 /Al 2 O 3 ratios on product distribution was investigated. • A high yield for valuable BTEX was achieved under microwave irradiation. • Catalyst stability, inactivation and regeneration performances were studied. • The reaction mechanism of plastic depolymerization was analyzed. The recycling and processing of plastic waste to promote resource sustainability has emerged as a global concern. Selectivily upcycling polyolefins into valuable monocyclic aromatic hydrocarbons (MAHs) is a promising strategy to promote a circular economy but limited by low yield and selectivity. In this study, one-step microwave-triggered tandem pyrolysis coupling ZSM-5 catalytic reforming technology was explored, which is efficient for selectively transforming plastic into benzene, toluene, ethylbenzene, and xylene (BTEX) riched oil products. Pyrolysis and catalytic processes were achieved by mixing plastic and ZSM-5 with graphite, respectively, and placing them in the bottom and top layers of the reactor. Results indicate the mass ratio of plastic or ZSM-5 to graphite and microwave irradiation power would influence the selectivity and yield of MAHs. After careful investigation, the optimum reaction conditions are deemed to be 600 W, and the mass ratio of LDPE and ZSM-5 to graphite is 3:1 and 1:1, respectively, and delightful selectivity and yield of MAHs of 82.06% and 28.12 wt% are obtained under the above conditions. More importantly, the BTEX accounted for a significant amount in the MAHs with the selectivity and yield of 70.53% and 24.17 wt%, demonstrating a strong ability to produce high-value BTEX, which is attributed to the ZSM-5 providing a sufficient active site for reforming the pyrolysis vapors and promote the formation of BTEX by cracking, aromatization and Diels-Alder reactions. Additionally, gas products are rich in C 2 H 4 , C 3 H 6 and C 4 H 8 olefin monomers accounting for around 60% of the gas products, which also manifest high value. Besides, the ZSM-5 can be stabilized by exceeding three successive cycles, and this strategy is also suitable for the catalytic upcycling of PP and mixed plastics to produce MAHs selectively. Therefore, this one-step microwave-triggered tandem pyrolysis coupling ZSM-5 catalytic reforming technology provides a potential waste resource utilization method to convert plastic waste into high-value petrochemical products. [ABSTRACT FROM AUTHOR]

This study was conducted to identify the ability of strain PS of Bacillus sp. on BTEX biodegradation process in saline and hypoxic condition. Despite numerous reports that have assessed BTEX biodegradation in saline environments and hypoxic conditions separately, it is the first time that BTEX biodegradation is investigated by considering these two limiting biodegradation conditions simultaneously. Taguchi's design of experiment methodology was applied to evaluate the influence of four factors (BTEX initial concentration, nitrate initial concentration, salinity and cell mass) on BTEX biodegradation. The chemical analyses, carried out with GC, showed that the most effective factors on biodegradation of the BTEX is initial BTEX and nitrate concentration. Cell mass and salinity only slightly influenced on the biodegradation. The 15 mg/L initial BTEX concentration at 5% salinity can be degraded by strain PS of Bacillus sp. at optimum condition containing 200 mg/L nitrate and 3 × 107 cells/mL cell mass after 10 days. [ABSTRACT FROM AUTHOR]

This paper deals about an approach to remediation for treating soils and groundwater contaminated with hydrocarbons in a tropical aquifer caused because of leaks from underground tanks in a gas station of Venezuela. Ex situ and in situ remediation treatment options were designed, recommending the ex situ remediation due to microbial inhibition produced by the presence of heavy metals and multiple strata with different soil materials in the interface between the unsaturated and saturated zones, where the most significant hydrocarbon concentrations were found. Under these conditions, ex situ bioremediation option based on two coupled bioreactors can overcome environmental limiting factors by optimizing temperature, oxygen supply, nutrient status, contaminant bioavailability, and microbial population. Ex situ remediation included for soil treatment, a Soil‐Slurry Sequencing Batch Reactor (SS‐SBR) and Upflow Anaerobic Filter separated in three phases (UAF‐3SS). For groundwater treatment SBR‐UAF‐3SS sequence was established. The first phase was represented by SS‐SBR for ex situ bioremediation of soils, configuring COD removal efficiency of 80%. It was set that SS‐SBR performs functions for groundwater treatment operating as SBR, removing 60% COD. For the second phase, an upflow anaerobic filter separate in three phases (UAF‐3SS) designed to ensure 99% COD removal efficiency. [ABSTRACT FROM AUTHOR]

Exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) and styrene have been reported in tire manufacturing. This research was designed to evaluate the exposure to BTEX and styrene and their health risks in tire manufacturing in Iran. The health risk estimation was done by the United States Environment Protection Agency (USEPA) method using the Monte-Carlo simulation. Results showed that the concentration of benzene in some units, such as cement making; cement spraying, and tire building was more than the standard level. The units of cement spraying and calendaring had the highest and lowest cancer and no-cancer risks, respectively. [ABSTRACT FROM AUTHOR]

Xylene is a typical petrochemical industry pollutant. The fate of xylene spilled into soil was investigated in laboratory-scale batch and column experiments. The results show that free xylene in the soil evaporated quickly (7.2–10.4 mg h−1), but any fraction adsorbed onto the soil particles evaporated much more slowly (2.3–2.4 mg h−1). The retention of xylene in the soil was mainly controlled by its adsorption onto the soil minerals. The adsorption was best described using a pseudo-second-order kinetic model and Langmuir model. Adsorption up to 530 mg kg−1 was observed, and minerals such as quartz and kaolinite were the key adsorbents. Adsorption of xylene was promoted by the presence of dissolved organics up to about 50 mg L−1, but it was significantly inhibited by cobalt-bearing compounds which are often used as catalysts in the petrochemical industry. The release of xylene from soil would be facilitated by intense rainfall and cobalt-bearing compounds but would be inhibited with the increase of rainwater acidity. This study reveals the environmental behavior of xylene in soil and provides scientific guidance for pollution control and risk assessment of BTEX contaminated sites. [ABSTRACT FROM AUTHOR]

Pars special economic energy zone (PSEEZ) in Iran is the second largest energy zone in the world with more than 60,000 operational and non-operational personnel. Considering the nature of the activities being done in PSEEZ, it is rational to expect that a wide range of hazardous materials be present in the air composition of this area. It is shown in this research that Benzene-Toluene-Ethylbenzene-Xylene (BTEX) are the most challenging in PSEEZ and benzene concentration violates the standards in all sampling points. The study area is divided into three subzones of gas refineries, petrochemical complexes and non-operational areas. In the gas refineries, benzene concentration is recorded to be 480 times higher than the standard for exposure limit. The concentration of benzene in petrochemical complexes is also about 160 times higher than the standard limit. Considering the vicinity of the petrochemical complexes the cumulative impacts of BTEX will also worsen the situation regarding BTEX cancer risk. In non-operational areas, benzene concentration reaches 40 times higher than the standard limit which is a serious health challenge. Comparing the data of BTEX distribution with AQI proves that AQI solely is not an appropriate index for assessing the air quality in PSEEZ and defining local indices for air quality assessment with taking hazardous chemicals such as BTEX into account. Moreover, some other pollutants such as heavy metals and H2S are detected in the air quality in significant amounts which raise the need to a reconsideration in location of unprotected non-operational personnel. [ABSTRACT FROM AUTHOR]

Objectives Our objectives were to (i) determine correlations between measurements of THC and of BTEX-H, (ii) apply these linear relationships to predict BTEX-H from measured THC, (iii) use these correlations as informative priors in Bayesian analyses to estimate exposures. Methods We used a Bayesian left-censored bivariate framework for all 3 objectives. First, we modeled the relationships (i.e. correlations) between THC and each BTEX-H chemical for various overarching groups of measurements using linear regression to determine if correlations derived from linear relationships differed by various exposure determinants. We then used the same linear regression relationships to predict (or impute) BTEX-H measurements from THC when only THC measurements were available. Finally, we used the same linear relationships as priors for the final exposure models that used real and predicted data to develop exposure estimate statistics for each individual exposure group. Results Correlations between measurements of THC and each of the BTEX-H chemicals (n = 120 for each of BTEX, 36 for n -hexane) differed substantially by area of the Gulf of Mexico and by time period that reflected different oil-spill related exposure opportunities. The correlations generally exceeded 0.5. Use of regression relationships to impute missing data resulted in the addition of >23 000 n -hexane and 541 observations for each of BTEX. The relationships were then used as priors for the calculation of exposure statistics while accounting for censored measurement data. Conclusions Taking advantage of observed relationships between THC and BTEX-H allowed us to develop robust exposure estimates where a large amount of data were missing, strengthening our exposure estimation process for the epidemiologic study. [ABSTRACT FROM AUTHOR]