Benzene, Toluene, Ethylbenzene And Xylene Research Articles

Spatial distribution of BTEX emission and health risk assessment in the ambient air of pars special economic energy zone (PSEEZ) using passive sampling

Benzene, toluene, ethylbenzene and xylene (BTEX) are a challenging group of volatile organic compounds in industrial and energy areas. Since these aromatics may cause serious diseases such as cancer and respiratory illnesses, they must be monitored. Pars Special Economic Energy Zone (PSEEZ) in Iran is the second largest energy zone of the world with numerous gas refineries and petrochemical complexes for producing a wide range of products. This study is focused on determination of BTEX concentration in the whole South Pars area (46 sampling points) which is the active site of PSEEZ using passive sampling. Then, the results of the passive sampling are used for providing spatial distribution of BTEX using GIS. The annual BTEX measurements revealed that benzene and toluene concentration violates the maximum permitted values at numerous points most of which are located in the vicinity of petrochemical complexes. Active sampling in these complexes not only confirms the results of passive sampling, but also suggests a more intensified BTEX pollution in the air quality of the area which reaches as high as 3500μg.m-3 and 18,000μg.m-3 for benzene and toluene, respectively, being far beyond the acceptable standards. Health risk analysis also confirms the intensity of BTEX at the selected points. This study suggests a reconsideration of the location of non-operational sites and personnel who are more vulnerable to BTEX contamination. Also, BTEX profile provided by GIS in this research gives a suitable plan for relocating.

BTEX levels in rural households: Heating system, building characteristic impacts and lifetime excess cancer risk assessment

BTEX (benzene, toluene, ethylbenzene, and xylene) are a group of toxic organic compounds that exposure to them can cause adverse short and long terms health effects. We measured the levels of BTEX in the indoor and outdoor air of rural areas in Ardebil, Iran. We further assessed their health risks and determinants parameters. BTEX were sampled by drawing air through activated charcoal tubes, using low flow SKC pumps. Samples were extracted by adding carbon disulfide and analyzed by subjecting the aromatic fraction to GC-FID. The results indicated that the concentrations of BTEX in the indoor air were significantly higher than those of outdoor (p-value<0.05). The mean indoor concentrations of benzene, toluene, ethylbenzene, and xylene were 41.69 ± 30.70, 96.73 ± 60.75, 38.73 ± 33.59, and 59.42 ± 35.99 μg m−3, while the mean outdoor concentrations of them were 8.94 ± 7.32, 36.93 ± 21.82, 7.66 ± 5.63, and 18.14 ± 10.25 μg m−3, respectively. The concentrations of BTEX in indoor and outdoor of the rural areas that used kerosene fuel for heating systems were significantly higher than those used natural gas. The results indicated that the tobacco smoke is a notable temporary source of indoor BTEX. The mean inhalation lifetime cancer risk (LTCR) value of benzene for residents of rural houses with the natural gas and kerosene heating systems were 28.6 × 10−6 and 97.2 × 10−6, while for ethylbenzene these figures stood out at 29.1 × 10−6 and 95.8 × 10−6, respectively. LTCR value for residents who used kerosene fuel for heating was higher than the World Health Organization (WHO) recommended limit.

Enhancing aromatics and olefins yields in thermo-catalytic pyrolysis of LDPE over zeolites: Role of staged catalysis and acid site density of HZSM-5

The present work deals with the thermo-catalytic pyrolysis of LDPE (low-density polyethylene) in lab-scale one- and two-stage test rigs over HZSM-5 catalysts featuring different acid site densities. In the first part of this work, the influence of catalyst-to-feed ratio and temperature (in conjunction with the acid site density of HZSM-5) on the product distribution was studied with an aim to identify the optimum operating conditions for the enhanced production of aromatics and light olefins. For this purpose, one-stage thermo-catalytic pyrolysis was performed in which catalysts were mixed with LDPE pellets for in-situ catalysis. In the one-stage catalytic pyrolysis, the catalyst sample with the highest acid site density gave the highest concentration of aromatics (ca. 55%) in the pyrolysis oil with a mono-aromatics fraction of over 50% that consisted mainly of BTEX (benzene, toluene, ethylbenzene and xylenes) compounds. The highest C2-C4 olefins concentration (ca. 65%) in the pyrolysis gas was obtained when the sample with the lowest acid site density was used. In the two-stage catalytic pyrolysis (ex-situ catalysis), the concentration of aromatics in the pyrolysis oil reached over 77% with a mono-aromatics fraction of ca. 72% that contained mainly BTEX compounds, when the most acidic catalyst was used. When the catalyst with the lowest number of strong acid sites was employed, the high content of C2-C4 olefins in the pyrolysis gas remained almost independent of the reactor configuration. These findings might provide important new insights for the chemical recycling of plastic wastes.

Measurement of BTEX (benzene, toluene, ethylbenzene and xylene) concentration at gas stations

Background: Fuel stations are one of the major sources of air pollution with volatile organic compounds, especially the four main petrol compounds benzene, toluene, ethylbenzene, and xylene (BTEX). BTEX in gasoline enters the air of gas stations due to high evaporation of gasoline. Therefore, determining the concentration of these compounds in gas stations in crowded and busy cities is one of the important priorities of environmental health, which is doubly important in terms of its negative effects on health. Methods: In this descriptive cross-sectional study, a total of 39 samples were collected from 13 gas stations. Sampling was performed in autumn 2018 in three working shifts (morning, noon, and night). The method NIOSH-1501 (i.e., using charcoal sorbent tubes and SKC pump with a flow rate of 0.2 L/min) was used for sampling the BTEX compounds. The mean difference and correlation of BTEX compounds based on meteorological parameters and the number of nozzles in gas stations were assessed using one-way ANOVA and correlation tests. Results: The mean and standard deviation of benzene, toluene, ethylbenzene, and xylene concentrations in the air of fuel stations were 2.784±1.461, 3.495±1.390, 2.091±0.811, and 1.140±0.419 mg/m3, respectively. The relationship between BTEX compounds and meteorological parameters such as humidity and exposure time is very important. There is a strong correlation between the concentrations of BTEX compounds. The highest correlation was observed between benzene and toluene and the lowest one was observed between benzene and xylene. In this study, no significant relationship was observed between air temperature and concentration of BTEX compounds, but there was a relationship between relative humidity and the concentration of BTEX compounds. Conclusion: The average benzene concentration in the air at the fuel stations was about 5.5 times the standard limit. Authorities should improve fuel quality and reduce its evaporation through engineering measures to overcome the issue.

Ambient BTEX Concentrations during the COVID-19 Lockdown in a Peri-Urban Environment (Orléans, France)

During the period from 17 March to 10 May 2020, France saw dramatic shifts in domestic, industrial and transport activities as a national lockdown was introduced. So far, studies have generally focused on urban settings, by contrast, this work reports data for a peri-urban location. Air samples were collected and analyzed using a fully automated GC-MS-FID system in an air quality monitoring station situated in the suburbs of Orléans, France. Average concentrations of BTEX (benzene, toluene, ethylbenzene, and xylenes) before, during, and after lockdown, were 402 ± 143, 800 ± 378 and 851 ± 445 pptv, respectively. Diurnal variation in BTEX and correlations between each of its components were analyzed to determine its various sources. The toluene/benzene (T/B) and m,p-xylene/ethylbenzene (MP/E) ratios, photochemical ages were used to explore whether the BTEX were from local or more distant sources. Together with a host of complementary measurements including NOx, O3, black carbon, meteorological parameters, and anthropogenic activities, we were able to make some inferences on the sources of BTEX. The results suggest that although anomalous local anthropogenic activity can lead to significant changes in BTEX concentrations, pollution levels in Orléans are mostly dependent on meteorological conditions, specifically whether the winds are coming from the Paris region. It appears, based on these measurements, that the pollution in the Orléans area is very much tied to the nearby megacity of Paris, this may be true for other peri-urban sites with implications for city planning and pollution mitigation strategies.

Spatiotemporal distribution characteristics and potential sources of VOCs at an industrial harbor city in southern Taiwan: Three-year VOCs monitoring data analysis

Kaohsiung City is the largest harbor city in Taiwan. The Linhai Special Industrial Complex (LSIC), which is the largest heavy industrial zone in Taiwan, and other industrial zones and storage station of petrochemicals are adjacent to the Kaohsiung Port. Volatile organic compounds (VOCs), which are discharged from industrial processes in this large industrial area, are likely to cause the poor ambient air quality and atmospheric visibility in Kaohsiung City. This study uses the continuous monitoring data of 54 VOCs during 2018–2020 at eight air quality monitoring stations in the industrialized city to evaluate the spatiotemporal distributions and seasonal variations of VOC concentrations. Principal component analysis and ratios of benzene, toluene, ethylbenzene and xylenes (BTEX) are used to track the potential sources of VOCs for different stations. The highest average concentration of total volatile organic compounds (TVOC) was observed in winter (32.54 ppb), while the lowest TVOC concentration was observed in summer (25.84 ppb), which is related to the prevailing wind directions of monsoons. Kaohsiung is located in the weak monsoon wake area, and air pollutants are easily accumulated in the winter. The southwest wind prevailing in summer results in good diffusion and frequent rainfalls. However, the Qijin station close to the seashore has the highest average TVOC concentration among the eight stations. The seasonal prevailing winds caused the average TVOC concentrations in summer (41.3 ppb) to be higher than that in winter (31.62 ppb) at the Qijin station. It was attributed to the fact that the Qijin Peninsula is vulnerable to VOC emissions from ship sailing in the Taiwan Strait, the processing and export zone, and the shipbuilding yards nearby the Kaohsiung Harbor. Comparing the BTEX ratios of Kaohsiung City with the data of Hong Kong, we found that VOCs were mainly from industrial emissions in Kaohsiung City, which were significantly different from Hong Kong that VOCs were mainly emitted from traffic emissions. Overall, VOCs in Kaohsiung City have been decreased from 2018 to 2020; however, according to the analytical results of ozone formation potential, toluene and m,p-xylenes are the most potential photochemical precursors for ozone formation. The government should enforce and regulate aromatic hydrocarbons from industrial emission sources to reduce the potential formation of ozone.

PDMS-coated γCD-MOF solid-phase microextraction fiber for BTEX analysis with boosted performances

Owing to the ubiquitous occurrence and chemotoxicity of BTEX (benzene, toluene, ethylbenzene and xylene), the development of stable and accurate analysis methods that can assess environment risks and can generate monitoring data rapidly is urgent. In this work, a new strategy was proposed for efficient detection of BTEX. By creatively utilizing thermal deposition method, a robust SPME fiber was fabricated, where the γCD-MOF acted as the adsorbent, while PDMS functionalized as the adhesive and protective coating. Benefiting from the protection of PDMS, the γCD-MOF fiber presented significantly better extraction performance and exhibited long-term structural stabilities in aqueous or methanol samples up to a week. The stable and improved properties of γCD-MOF demonstrated that the PDMS protected the MOF components from the adverse effects of solvent. The detection limits of PDMS modified γCD-MOF fiber for BTEX was as low as 0.13–0.29 ng L−1 that accompanied with wide linear range of 1–1000 ng L−1, which was significantly superior to commercial PDMS fiber and other MOF-based fibers. Besides, the feasibility of the proposed method was verified by the quantitative determination of BTEX in real water samples. This work presents an effective strategy for creating ultrasensitive and stable SPME fibers based on γCD-MOF for applications in aqueous samples or other poor solvent.

Application of Steam Enhanced Extraction Method on BTEX Contaminated Soil in A Nigerian Petroleum Depot and Automobile Workshop Sites in Ilorin Metropolis, Nigeria

The contamination of soil in the environment is a natural consequence of industrialization and urbanization. Organic chemical pollutants dissolve into groundwater, absorb and adsorb into soil grains. Benzene, toluene, ethylbenzene and xylene (BTEX) are major causes of contaminated soil. This is due to fuel leakages or spillages, various forms of hydrocarbon burning/combustion and land disposal petroleum base oil. Contaminated soil samples were excavated from two different locations within the Ilorin metropolis; pipelines and products marketing company, a Nigerian petroleum depot, Ilorin depot and auto mechanic workshop of over ten years. Steam enhanced extraction method was employed through injection of steam to contaminated soil from steam generator into soil pot where contaminated soil was placed. The condensation of steam on soil particles provides energy to release desorbed contaminants molecules from the soil and the mobilized contaminants vapor was transferred into the recovery pot via the pipe that was connected to the soil pot. After the remediation process, the steamed soil samples were taken to the laboratory where the sonication extraction technique was used to extract the contaminants (BTEX) from the steamed soil samples of 30, 60 and 90 minutes respectively. The extract from the steamed soil samples of 30, 60 and 90 minutes was subjected to Gas Chromatography fitted with flame ionization detector analysis to determine the exact amount of BTEX removed after the remediation process. Pre-treated soil sample of auto mechanics workshop was found to be 4.5004 x 10-1 mg/kg and post-treated soil samples were found to be 1.8164 x10-1 mg/kg, 8.7519 x10-1 mg/kg and 5.7006 x10-2 mg/kg for 30, 60 and 90 minutes respectively after remediation process while Pre-treated soil sample of a Nigerian petroleum depot was found to be 6.6049 x 10-1 mg/kg and post-treated soil samples were found to be 2.9320 x10-1 mg/kg, 1.9855 x10-1 mg/kg and 1.0237 x10-1 mg/kg for 30, 60 and 90 minutes respectively after the remediation process. This study established the effectiveness of the remediation process of hydrocarbon contaminated soil using steam enhanced extraction method an In situ remediation technique.

Treatment Efficiency of Drill Cuttings Using Thermal Desorption Technology

Aim: The aim of this study was to analyze and determine the treatment efficiency of drill cuttings using the Thermal Desorption Technology.&#x0D; Study Design: Drill cuttings were obtained from a work-over drilling operation with samples obtained at a depth of 2,750m from a typical well for this baseline study. The aim is to analyze the physical and chemical characteristics of the drill cuttings in a laboratory before and after the thermal desorption processes. A second drill cutting sample from another field location at the same depth of 2,750m was used for comparison during the analysis.&#x0D; Place and Duration of Study: Port Harcourt, Rivers state, Nigeria (Laboratory analysis was done at Anal Concept Ltd, Port Harcourt, Rivers state, Nigeria and the thermal desorption unit is situated at the Initiates Plc, Etche LGA, Rivers state, Nigeria).&#x0D; Methodology: A representative sample feedstock of cuttings was collected before and after the thermal treatment. The drill cutting sample was taken from a mixing tank by using a cup and auger. The samples of the cuttings were made for each case of the grab samples, and the samples later transferred into 500mL glass bottles. The sample contaminants were analyzed in a chemical laboratory using standard methods for determining the pH level, Electrical Conductivity, Moisture Content, Organic Pollutants and Heavy Metals.&#x0D; Results: The result showed significant reductions in all the pollutant concentrations after the drill cuttings were treated with the Thermal Desorption Unit. Moisture Content (MC) and the Total Petroleum Hydrocarbon (TPH) decreased significantly by 86% and 93% respectively. The concentration of the combination of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) reduced drastically by 98% and the heavy metals concentration levels were also reduced after treatment with the TDU. Also, the laboratory analysis result of the treated drill cuttings shows that the pH level, Electrical Conductivity, Moisture Content, Organic Pollutants and Heavy Metals concentrations did not exceed the recommended Department of Petroleum Resources (D.P.R) limits.&#x0D; Conclusion: This research reveals that the thermal desorption technology is the most economical, efficient and environmentally friendly method of waste management due to its contaminant removal efficiency. This method enhances product recovery and subsequent recycling which helps to reduce environmental impact and prevent economic losses.

Increased aromatics production by co-feeding waste oil sludge to the catalytic pyrolysis of cellulose

In this study, the use of oil sludge as the co-feeding feedstock on the catalytic pyrolysis of cellulose over various catalysts, such as Ni/HZSM-5, HZSM-5, HBeta, HY, and Al-MCM-41, was attempted for the first time. To know the catalytic co-pyrolysis effect, thermogravimetric analysis and pyrolyzer-gas chromatography/mass spectrometry measurement were utilized. Thermogravimetric analysis results indicated that Ni/HZSM-5 led to the lowest apparent activation energy (97.6 kJ/mol), followed by HY, HBeta, HZSM-5, and Al-MCM-41, suggesting the effective role of Ni providing the additional cracking and benzene, toluene, ethylbenzene and xylenes (BTEXs) formation. In addition, BTEXs production amount analyzed by pyrolyzer-gas chromatography/mass spectrometry was also highest by the use of Ni/HZSM-5 due to its proper pore size of HZSM-5 on BTEXs formation and additional effect of Ni. The experimental BTEXs yields on the catalytic co-pyrolysis of cellulose and oil sludge were higher than their theoretical values over all catalysts, suggesting their synergy effect. The highest synergistic effect was also achieved when 1/3 of cellulose/oil sludge mixture was applied as the feedstock.

Evaluation of potential human health risks from exposure to volatile organic compounds in contaminated urban groundwater in the Sava river aquifer, Belgrade, Serbia.

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.

One-year monitoring of aromatic volatile organic compounds (VOCs) in urban areas of Malaysia

VOCs have been one of the important limiting factors of O3 photochemical production in the urban tropical region. This study aims to determine the variation and composition of aromatic VOCs as well as their contribution to the O3 formation. The hourly data of benzene, toluene, ethylbenzene and xylenes (BTEX) and ozone (O3) were retrieved from January until December 2019 at three continuous air quality monitoring stations (S1, S2 and S3) operated by the Malaysian Department of Environment (DOE). Aromatic VOCs is detected by using an online gas chromatography analyser (GC 5000BTX). The annual average ΣBTEX concentrations ranged from 14.53 ± 12.43 μg m-3 to 25.04 ± 24.04 μg m-3 during the observation period, with toluene as the most dominant species with an average concentration of 10.65 ± 12.12 μg m-3. The O3 formation potential (OFP) was calculated and the results indicated that toluene is the highest contributor of O3-forming potential, followed by m, p-xylene, o-xylene, ethylbenzene and benzene with the value of 127.8 μg m-3 (40.90 %), 103.0 μg m-3 (32.97 %), 48.66 μg m-3 (15.58 %), 26.17 μg m-3 (8.38 %) and 6.74 μg m-3 (2.15 %), respectively. Since the study of VOCs in Malaysia is quite limited, a more comprehensive study is currently underway to integrate the research on variation of VOCs in ambient air and its impact on the environment and human health.

Determination of BTEX Compounds in Contaminated Water Using the Novel Vacuum-Assisted-Total Vaporization SPME Method and GO-APTES Fiber.

A novel and reliable microextraction technique was used for the fast determination of benzene, toluene, ethylbenzene and xylenes (BTEX) from contaminated water without any extra steps for the preparation or extraction of the aqueous sample. Vacuum-assisted-total vaporization-solid-phase microextraction (SPME) eliminated one of the partitioning steps in conventional headspace SPME and caused an increase in the sensitivity and speed of the method. A home-made graphene oxide/3-aminopropyl-triethoxysilane nanocomposite SPME fiber was synthesized and used as the extraction phase for efficient extraction. Several crucial parameters were optimized, such as the vaporization time and temperature, extraction time and desorption conditions. At the optimum experimental conditions, a linear wide range calibration curve over a wide range of 1-5,000ngmL-1 and a relative standard deviation (n = 6) of 6.6-7.3% were obtained. The result of the determination of BTEX as a human health risk from real samples, using the proposed method, revealed an acceptable agreement with a valid method.

Enhanced selectivity of benzene-toluene-ethyl benzene and xylene (BTEX) in direct conversion of n-butanol to aromatics over Zn modified HZSM5 catalysts

The sustainable aromatics production from renewable source is indispensable to circumvallate the dependence on fossil fuel for commodity chemicals. Direct conversion of n-butanol to aromatics using xZn-HZSM5 (0–10 wt%, SiO 2 /Al 2 O 3 = 23, 55 and 280) catalysts was proposed in the present investigation. Characterization studies revealed the formation of different Zn species depending on the Zn loading. Furthermore, XPS analysis confirmed strong interaction of Zn species with the electronegative oxygen atom of zeolite framework. Zn deposition enhanced the selectivities of aromatics and BTEX. The presence of Zn species suppressed the hydride transfer reaction and promoted the dehydrogenation reaction resulting in higher selectivities of aromatics and BTEX. The rising temperature and declining in WHSV enhanced the selectivities of aromatics and BTEX. The high pressure had adverse effect on the selectivities of aromatics. The maximum selectivity of total aromatics (74.83%) and BTEX (68.75%) were achieved at 723 K, 1 bar pressure and 0.75 h −1 of WHSV. The coke analysis revealed the formation of polynuclear aromatic coke at high pressure. The alkyl substitute aromatics and polynuclear aromatics were formed predominately on pure HZSM5 (55) than 5Zn-HZSM5 (55). A plausible reaction mechanism was suggested considering the products distribution. • Direct conversion of n-butanol to aromatics and BTEX using Zn-HZSM5. • Characterization results revealed formation of different Zn species, ZnOH + and ZnO. • Zn species suppress hydride transfer reaction and promotes dehydrogenation reaction. • The maximum selectivity of aromatics (74.83%) and BTEX (68.75%) were achieved. • High reaction pressure results in the formation of polynuclear aromatic type coke.

Field evaluation of a low-uptake VOC passive sampler suitable for long-term deployments

Passive samplers have proven to be effective for continuous monitoring of volatile organic compounds (VOCs) in ambient air in remote, urban and industrial environments. Thermal desorption tubes fitted with endcaps that facilitate passive uptake through diffusion are now routinely used for monitoring fugitive benzene emissions from refineries and petrochemical facilities across North America (EPA Method 325A/B). However, deployment periods of 14 days are typically employed to minimize the risk of poor retention, requiring 26 deployments per year to return an annual average concentration for comparison with chronic exposure health-based standards. Here, we explore extending the deployment duration of these passive samplers to one, two and three months by limiting VOC uptake rates using an alternative diffusive endcap featuring a smaller cross-sectional area. Field testing was performed beside a major highway during two separate three-month campaigns. Uptake rates for benzene, toluene, ethylbenzene and xylenes (BTEX) were observed to remain linear for deployments of up to three months when using the low-uptake endcaps. Application of the low-uptake endcaps and the uptake rates determined here will enable annual average concentrations of BTEX to be calculated using only four tube deployments per year. The cost savings associated with this decreased deployment frequency will facilitate increased spatial resolution during future exposure assessment studies. The stability of selected air toxics within the tubes was also assessed and the results suggest that while aromatic VOCs are stable for storage times of at least 70 days, chloroform and trichloroethylene begin to degrade within two weeks of sampling.

High-sensitive metal oxide gas sensor for BTEX gases based on ternary composite of Ce x Mn1−x O2/SnO2

A sensitive gas sensor based on a ternary composite of Ce x Mn1−x O2/SnO2 was used for BTEX detection. The ternary Ce x Mn1−x O2/SnO2 was synthesized via hydrothermal and immersion method and characterized by high resolution transmission electron microscopy and x-ray photoelectron spectroscopy. The gas sensor performances were measured on a designed flow-through microsystem consisted of a dynamic multiple gas handling unit, a test gas preheater, an olive-like test chamber and a data analysis apparatus. The developed gas sensor shows a high sensitivity towards BTEX (benzene, toluene, ethylbenzene and xylene) gases with a linear ranging from 100 to 600 ppb at optimal temperature. The sensor exhibited relative selectivity to BTEX gases compared to other VOC components. The sensing mechanism can be concluded as the ‘spillover effects’ of Ce x Mn1−x O2 and heterogeneous effect at the interphase of the Ce x Mn1−x O2–SnO2. The gas sensor developed in this paper provide a possible further application in BTEX gases, especially in ppb-level detection.

Benzene, Toluene, Ethylbenzene and Xylene (BTEX) Concentrations in Urban Areas Impacted by Chemical and Petrochemical Industrial Emissions.

The Metropolitan Region of Rio de Janeiro is the second largest urban and industrial region in Brazil. While the south and south-east areas are affected by vehicular emissions, the districts and cities located in the northern area are subjected to industrial emissions and have the poorest air quality of the region. In this study, BTEX concentrations were determined in the District of Irajá, a residential area located in the north of the city of Rio de Janeiro, approximately 25km from the industrial zone, as well as in the District of Jardim Primavera, in the city of Duque de Caxias. The mean values for total BTEX concentrations were 38.4 ± 11.7 and 44.6 ± 29.3μgm-3, in Irajá and Jardim Primavera, respectively, which are higher than those previously reported for other areas. The benzene/toluene rates, (approximately 0.5 for both sampling sites), were also higher than typical values that were determined for diesel and gasoline emissions through dynamometer experiments.

Level of air BTEX in urban, rural and industrial regions of Bandar Abbas, Iran; indoor-outdoor relationships and probabilistic health risk assessment

This study focused on the measurement of BTEX (benzene, toluene, ethylbenzene and xylene) concentrations in the air of various regions and indoor-outdoor environments in Bandar Abbas, Iran. Air samples were taken actively and analyzed by gas chromatography-mass spectrometry (GC-MS) during two one-month periods i.e., Feb 2020 (period I) and Sep/Oct 2020 (period II). The mean air temperature and the levels of all BTEX compounds were higher in period II. The highest total BTEX (t-BTEX) levels (median [min-max]) were found in the urban region (18.00 [5.21–67.24] μg m−3), followed by industrial region (7.00 [2.05–14.76] μg m−3) and rural region (2.81 [ND-7.38] μg m−3). The significant positive correlations between all BTEX compounds and T/B ratio >1 indicated the vehicular traffic as the main source of emission. At 95th percentile probability, the non-cancer risk of t-BTEX in urban region was only less than one order of magnitude below the threshold level of unity (1.91E-01) and the cancer risk of benzene exceeded the recommended level of 1.0E-06 by U.S. EPA in urban (7.69E-06) and industrial (2.97E-06) regions. It was found that the indoor/outdoor ratio of BTEX concentration in beauty salon and hospital was greater than 1. Overall, the current levels of BTEX in the ambient air of study area, especially near urban roadside and in some indoor environments, should not be overlooked and appropriate mitigation actions should be undertaken.

Effects of water produced by oil segment on aquatic organisms after treatment using advanced oxidative processes

ABSTRACT The water produced (PW) by the petroleum industry is a potential contaminant to aquatic biota, due to its complex mixture that may contain polycyclic aromatic hydrocarbons (PAHs), organic chemical compounds, including benzene, toluene, ethylbenzene and xylene (BTEX), metals and other components that are known to be toxic. The aim of this investigation was to examine the acute toxicity produced by a PW sample in aquatic organisms Vibrio fischeri and Daphnia similis prior to and after 4 treatments using advanced oxidative processes such as photocatalysis, photoelectrocatalysis, ozonation and photoelectrocatalytic ozonation. Data demonstrated that exposure to PW was toxic to both organisms, as evidenced by reduced luminescence in bacterium Vibrio fischeri and induced immobility in Daphnia similis. After treatment of PW with 4 different techniques, the PW remained toxic for both tested organisms. However, photoelectrocatalysis was more efficient in decreasing toxicity attributed to PW sample. Therefore, data demonstrate the importance of treating PW for later disposal in the environment in order to mitigate ecotoxicological impacts. Further photoelectrocatalysis appeared to be a promising tool for treating PW samples prior to disposal and exposure of aquatic ecosystems.

Monoaromatic Hydrocarbon Bioremediation of Hydrocarbon-contaminated Soil Using HBB5 Biosurfactant Produced by Pseudomonas xiamenensis

Biodegradation of benzene toluene ethylbenzene and xylenes (BTEX) is a slow and complex process. However, many microbial organisms have been shown to possess the capacity to biodegrade various components of a hydrocarbon. This study was aimed at investigating the role of biosurfactant on soil polluted with these monoaromatics. Samples were collected and analyzed using standard techniques. The biodegradation set up was carried out using five earthen pots; each containing unpolluted soil, polluted soil alone, polluted soil + poultry wastes, polluted soil + HBB5 biosurfactant and polluted soil + poultry wastes + HBB5 biosurfactant. The biodegradation of BTEX were periodically monitored every seven days for 28 days using gas chromatograph-mass spectrometer coupled with head space (GC-MS-HS). The respective initial and final concentrations of BTEX (ppm) were as follows; 0.7936 and 0.2063, 0.9733 and 0.0231, 0.9526 and &lt;0.0001, 0.9241 and &lt;0.0001 with degradation efficiencies of 74.0%, 97.6%, 100% and 100% for polluted soil alone, polluted soil + poultry wastes, polluted soil + HBB5 biosurfactant and polluted soil + poultry wastes + HBB5 biosurfactant respectively. The microbial counts increased greatly, and the concentrations of the limiting nutrients reduced during the experimental period. The effective treatments for bioremediation increased in the following order: polluted soil alone &lt; polluted soil + poultry waste &lt; polluted soil + HBB5 biosurfactant &lt; polluted soil + poultry waste + HBB5 biosurfactant. Results clearly showed that application of HBB5 biosurfactant only or in combination with poultry wastes has the ability to degrade ethylbenzene and xylenes (BTEX) and thus, can be employed in the clean-up of crude oil contaminated soil.