Concentrations Of Xylene Research Articles

Evaluation of airborne exposure to volatile organic compounds of benzene, toluene, xylene, and ethylbenzene and its relationship to biological contact index in the workers of a petrochemical plant in the west of Iran.

Nowadays, workers in petrochemical industry might be exposed to organic volatile compounds, including benzene, toluene, ethylbenzene, and xylene (BTEX). The aim of this study was to investigate the concentration of BTEX contaminations and the biological index in employees of petrochemical sites in the west of Iran. The study was conducted as a cross-sectional study on 30 stations and 60 inhalation and biological samples collected in winter and summer. The NIOSH 2549 and 1501 methods were used for sampling and analyzing the inhaled samples. Gas chromatography-mass spectrometry (GC-MS) equipped with flame ionization detector and high-performance liquid chromatography (HPLC) was used to measure the volatile contaminations. The results showed that the mean concentrations of benzene, toluene, and xylene were significantly different in summer and winter. Significant and strong correlations were observed between the concentrations of benzene, toluene, and xylene and the biological values (r > 0.7). Moreover, the concentration of benzene (β = 0.836), toluene (β = 0.718), and xylene (β = 0.786) predicted the changes in their biological values. Given the hazardous concentrations of benzene and toluene in industrial plants and the correlation of the concentration levels and biological values, management and control strategies should be implemented to eliminate and reduce the pollutants and the effects.

Thermo-Chemical Treatment for Carcass Disposal and the Application of Treated Carcass as Compost

A mechanized thermo-chemical treatment system was developed to treat the undecomposed carcass and remediate livestock burial sites. Animal carcasses were thus processed via crushing, mixing, and treatment with quicklime treatment, heat treatment (200–500 °C), and mixing with sawdust. The machinery was applied to two sites where 16,000 chickens and 418 pigs had previously been buried in fiber-reinforced plastic storage bins. No dioxins were detected in the gas discharged during processing, and the concentration of total volatile organic compound, toluene, ethylbenzene, xylene, and styrene were 430.3, 139.0, 18.3, 21.4, and 10.4 μg/m3, respectively, which were below the air pollutant emission standards issued by the Korean Ministry of Environment. Korean standards stipulating the use of treated carcasses as compost (C, N, and P content, heavy metal concentration, Escherichia coli, and Salmonella) were met, but the germination index value was less than 70, not satisfying the criteria. Plant height, leaf length, leaf width, and dry weight of lettuce grown in soil amended with treated carcass product were significantly lower than those grown in low nutrient soil due to the poor germination index of the treated carcass. These results indicate that a composting process is required before the use of the treated carcass as a fertilizer. The addition of zeolite retarded the elution of ammonia from the carcasses and its efficiency was about 87.9%. It is expected that the mechanized thermo-chemical treatment process developed in this study could replace other technologies for the remediation of livestock burial sites.

Decomposition of xylene in strong ionization non-thermal plasma at atmospheric pressure

A large amount of volatile organic compounds (VOCs) produced by industry have caused serious environmental pollution. In this paper, the removal effect of simulated xylene by strong ionization dielectric barrier discharge (DBD) plasma at atmospheric pressure and its degradation mechanism and pathway were studied. The effect of gas residence time, and initial xylene concentration was studied. The results showed that higher voltage caused an increase in discharge power, and with the increase of voltage, the concentration of ozone and nitrogen oxide in the reactor increased. The degradation efficiency decreased from 98.1% to 80.2% when xylene concentration increased from 50 ppm to 550 ppm at 4kV. And with the increase of residence time from 0.301s to 1s, the degradation efficiency increased from 78.5% to 98.6%. According to GC-MS analysis, the degradation products were ethyl acetate and n-hexylmethylamine at 4kv. And the main intermediates are 2,4-2-tert-butylphenol, 2-aminopentane, 2-methyl-5 - (2-aminopropyl) - phenol and propionamide at 1.5kV.

Assessment of BTEX Concentration around Fuel Station in Eastern Province Kingdom of Saudi Arabia

Aim: The aim of this study is to determine the benzene, toluene, ethylbenzene, and xylene (BTEX) concentration levels in and around the fuel station and its harmful health effects in the city of Dammam and Al Khobar, Saudi Arabia. Materials and Methods: Forty fuel-dispensing facilities were randomly selected on the basis of three different areas: residential, traffic intersection, and petrol pump locations (refueling stations). Samples were collected using coconut shell charcoal cartridges, and the portable ambient analyzer was used for measuring BTEX concentration. Results: Results shows that the average concentration of BTEX levels around fuel stations was 10.30, 4.09, and 2.47 ppm, respectively. All mean concentration values of BTEX around residential, traffic intersection, and fuel stations are exceeding the limits of air quality standards values (P < 0.01). The mean concentration of BTEX around the residential area, side street, and direct street was as follows: benzene 8, 12.2, and 11.5 ppm; toluene 2.5, 5.95, and 3.37 ppm; and xylene 2, 2.13, and 2.7 ppm. Hazard quotient was >1, which showed that carcinogenic probability has increased those exposed to this toxic chemical. Conclusion: Values for BTEX were greater than those found in the neighboring residential area of the city and even 100 m away from the fuel station which can have a negative impact on the health of several residences. The environmental contamination associated with BTEX in petrol fuel stations impulses the necessity of preventive programs to reduce further air quality deterioration and reduce the harmful health effects.

Life Cycle Assessment and Indoor Environmental Quality of Wooden Family Houses

This article analyzes in detail the impact of wooden houses on the environment using the life cycle assessment (LCA) methodology and at the same time evaluates the indoor environmental quality (IEQ) in these houses. The investigated detached family houses had a wooden structure. The first one had a bearing system made of a wooden frame; other materials were conventional. The second house was built entirely of log wood. Given the high risk of greenhouse gas emissions, the concentration of which in the atmosphere is causing global climate change, the global warming potential (GWP) indicator is crucial. According to results, the family house built entirely of wood and with a biomass boiler significantly reduces CO2 emissions and is therefore considered from the LCA point of view as a more suitable alternative compared to a house with a wooden frame structure. The building materials with the highest share involved in the creation of GWP include concrete structures (38–48%), ceramic roof tiles (33%) and plasterboard (15%). Plasterboard cladding (55%), concrete structures (17–19%), oriented strand board OSB (9–22%), impregnated wooden structures (31–52%) and plastic windows (9%) are the most involved in acidification potential (AP) and eutrophication potential (EP). Plasterboard structures (21%), impregnated wood materials (47.4%), reinforced concrete structures (12%) and mineral wool and roof tiles significantly contribute to the creation of photochemical ozone creation potential (POCP) and ozone depletion potential (ODP). The indoor environmental quality was evaluated through short-term measurements of basic physico-chemical parameters. Since both houses have different characteristics, the aim of this monitoring was to evaluate the actual state of IEQ in selected wooden houses under real conditions. Based on the recorded results, it can be stated that neither presented wooden house, in terms of thermal-humidity microclimate, concentration of CO2 and particulate matter, represents an environment with a negative impact on their occupants. With regards to volatile organic compounds (VOCs), the increased concentrations of xylenes and tetrachlorethylene in the log house were probably caused by the application of impregnation and protective coatings six months before monitoring. In this case, the concentration of tetrachloroethene, which is considered a potential carcinogen, was six times higher than the legislative limit. For VOCs, such as limonene, isobutylene and n-butylacetate, which were found in the wooden frame house, no limits are set. The legislative limits for xylenes and tetrachlorethylene in this house have not been exceeded, and therefore the IEQ cannot yet be considered harmful for health. The presence of all the mentioned VOCs in the interior air of the wooden frame house is more related to the activities of occupants, as this house has been inhabited for several years.

Advanced oxidation processes for elimination of xylene from waste gases

The elimination of xylene was experimentally studied using advanced oxidation process in a two-step pilot plant photochemical unit with the use of UV irradiation combined with ozone (first step) and with hydrogen peroxide solution (second step). The influence of the initial xylene concentration and air flow rate was investigated. A mathematical model of the first step of the unit applying UV/O3 treatment was developed. Xylene conversion decreased with increasing its initial concentration and increasing flow rate of the air (lowering residence time in the unit). The highest xylene conversion (95 %) was achieved with the initial concentration 50 ppmv and the flow rate 57 m3· h−1. Based on the model results for the first photolytic step of the pilot plant unit, the main pathway of the elimination of xylene is its reaction with hydroxyl radicals which are formed both by the reaction of ozone with water/humidity but also by the reaction of singlet oxygen (formed by the decomposition of ozone) with water/humidity. Calculated figures-of-merit showed that the pilot plant unit is more energy-cost-efficient for the higher flow rates of the waste gas. The technology using advanced oxidation processes seems promising for the elimination of organic compounds from the air, although further studies are necessary.

Distributions and temporal changes of benzene, toluene, ethylbenzene, and xylene concentrations in newly decorated rooms in southeastern China, and the health risks posed

Air samples were collected from 227 newly decorated rooms in southeastern China, between November 2014 and July 2017. Benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations in the samples were determined. Temporal changes in the BTEX concentrations during decorating were investigated. Cancer and non-cancer risks posed by BTEX were evaluated. The mean BTEX concentrations decreased in the order xylene (0.476 ± 0.665 mg/m3) > benzene (0.327 ± 0.189 mg/m3) > toluene (0.325 ± 0.449 mg/m3) > ethylbenzene (0.140 ± 0.280 mg/m3). Benzene, toluene, and xylene concentrations in 86.7%, 42.7%, and 51.5%, respectively, exceeded Chinese regulatory standards. The BTEX concentrations positively correlated with temperature and humidity but negatively correlated with air pressure, and the highest concentrations were found in summer. The BTEX concentrations were higher in conference rooms and residences than classrooms and halls. The highest BTEX concentrations were found during painting and carpentry. The hazard quotient limit of 1 and the cancer risk limit of 1 × 10−6 were exceeded in 91.2% and 85.0%, respectively, of the rooms, and benzene and xylene were the dominant contributors. The results suggested that newly decorated rooms should not be used too soon after decoration is completed.

Toxicological Study and Genetic Basis of BTEX Susceptibility in Drosophila melanogaster.

Benzene, toluene, ethylbenzene and xylene, also known as BTEX, are released into environmental media by petroleum product exploratory and exploitative activities and are harmful to humans and animals. Testing the effects of these chemicals on a significantly large scale requires an inexpensive, rapidly developing model organism such as Drosophila melanogaster. In this study, the toxicological profile of benzene, toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene in D. melanogaster was evaluated. Adult animals were monitored for acute toxicity effects. Similarly, first instar larvae reared separately on the same compounds were monitored for the ability to develop into adult flies (eclosion). Further, the impact of fixed concentrations of benzene and xylene on apoptosis and mitosis were investigated in adult progenitor tissues found in third instar larvae. Toluene is the most toxic to adult flies with an LC50 of 0.166 mM, while a significant and dose-dependent decrease in fly eclosion was observed with benzene, p-xylene, and o-xylene. An increase in apoptosis and mitosis was also observed in animals exposed to benzene and p-xylene. Through Genome Wide Association Screening (GWAS), 38 regions of the D. melanogaster genome were identified as critical for responses to p-xylene. This study reveals the strength of D. Melanogaster genetics as an accessible approach to study BTEX compounds.

Petroleum hydrocarbon pollution in the Niger Delta: human health risk assessment of BTEX in biota

Based on the context of extensive petroleum hydrocarbon pollution in southern Nigeria, the concentrations of benzene, toluene, ethylbenzene and xylene (BTEX) in seafood were determined, and the health risks of these compounds were evaluated. Biota samples (Crayfish, Goby fish, Moonfish, Mudskipper, Mullet, Sardine and Tilapia) were collected from the Bonny Estuary from 2016 to 2018 and analyzed according to US EPA method 5030/8260C to determine the concentrations of BTEX. Risk assessment of BTEX to humans through the dietary route was conducted based on the lifetime cancer risk (LTCR) for benzene and the hazard quotient (HQ) for BTEX. The following BTEX concentration ranges were observed: benzene: < 0.01–0.36 mg/kg; toluene: 0.22–19.85 mg/kg; ethylbenzene: < 0.00–1.54 mg/kg; xylene: < 0.00–7.28 mg/kg. The median LTCR for benzene in children and adults was 0.65 and 0.30, respectively, which are higher than the limit recommended by the World Health Organization. The model showed that the LTCR is reducible by 99.9% and 66.6% if the concentration of benzene is 0.00001 mg/kg, and fresh seafood consumption is reduced to 10.4 g/day. The HQ for all BTEX compounds was greater than 1 (benzene: 1.0 × 104 (child), 4.9 × 103 (adult); toluene: 1.9 × 105 (child), 9.0 × 104 (adult); ethylbenzene: 9.4 × 103 (child), 4.4 × 103 (adult); xylene: 2.5 × 104 (child), 1.2 × 104 (adult)), which signifies a high non-cancer health risk to humans. These results are a reflection of the high level of petroleum hydrocarbon pollution in southern Nigeria and the debilitating human health consequences that could accompany it.

Emission fluxes of styrene monomers and other chemicals for products containing expanded polystyrene beads.

Styrene in indoor air can adversely affect human health. In this study, styrene monomer and other chemical emission fluxes for products containing expanded polystyrene beads (pillows, cushions, and soft toys) were measured at various temperatures to simulate typical product use. The contributions of the products to styrene and other chemical concentrations in indoor air and human exposure to these chemicals were estimated, and health risk assessments were performed. The styrene monomer emission fluxes for the samples at 25°C were between 25.3 and 8.73×103 μg/(m2 h). The styrene emission fluxes for the product surfaces increased strongly as the temperature increased, from between 124 and 2.44×104 μg/(m2 h) at 36°C (simulating human body temperature) to between 474 and 4.59×104 μg/(m2 h) at 50°C (simulating inside an automobile in summer). The hexane, heptane, toluene, octane, ethylbenzene, m- and p-xylene, o-xylene, and dodecane emission fluxes at 25°C for the sample that emitted the analytes most readily were high. The maximum estimated styrene and xylene concentrations in indoor air caused by emissions from expanded polystyrene beads at 36°C in a bedroom and automobile were higher than the relevant guidelines. The maximum contribution of a product containing expanded polystyrene beads in a living room, bedroom, or automobile could cause the total volatile organic compound concentration in air to exceed the advisable value (400 μg/m3). The estimated maximum hazard quotients for styrene, toluene, and xylene emitted by a product containing expanded polystyrene beads at 36°C in a bedroom were 0.59, 0.30, and 0.37, respectively. These non-carcinogenic risk values for single products could contribute to the non-carcinogenic risk thresholds being exceeded when multiple products and other sources of chemicals are taken into consideration. The estimated styrene concentrations suggest that products containing expanded polystyrene beads are important sources of styrene to indoor air.

Optical and gas-sensing property enhancement of membranes based on lithium iron phosphate particles with different dispersants

Lithium iron phosphate (LiFePO4) membranes were fabricated by coating LiFePO4 particles dispersed in various dispersants on tin-diffused glass slides and alumina ceramic tubes for xylene gas detection. The influences of dispersants, including polyvinyl alcohol (PVA), sodium dodecylbenzene sulfonate (SDBS), and methyl methacrylate (MMA), on the optical properties and opto-electrical gas-sensing performance of the LiFePO4 particle-based membranes were investigated. The LiFePO4 particle-based membrane, prepared using PVA, exhibited less agglomeration, better transparency, optimum refractive index, and a higher response toward xylene gas at concentrations of 10 ppb to 1000 ppm in a planar optical waveguide sensor. However, in a resistance-type electrochemical sensing system at room temperature, the LiFePO4-PVA membrane exhibited low response even at high xylene concentrations. The membranes sensitivities increased in the order MMA < SDBS < PVA. After dispersing in PVA, the membrane sensitivity toward xylene was increased ~ 100 times, proving the positive effects of PVA on the optical properties and gas-sensing performance of LiFePO4 particles.

Monitoring the BTEX Volatiles during 3D Printing with Acrylonitrile Butadiene Styrene (ABS) Using Electronic Nose and Proton Transfer Reaction Mass Spectrometry.

We describe a concept study in which the changes of concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds and styrene within a 3D printer enclosure during printing with different acrylonitrile butadiene styrene (ABS) filaments were monitored in real-time using a proton transfer reaction mass spectrometer and an electronic nose. The quantitative data on the concentration of the BTEX compounds, in particular the concentration of carcinogenic benzene, were then used as reference values for assessing the applicability of an array of low-cost electrochemical sensors in monitoring the exposure of the users of consumer-grade fused deposition modelling 3D printers to potentially harmful volatiles. Using multivariate statistical analysis and machine learning, it was possible to determine whether a set threshold limit value for the concentration of BTEX was exceeded with a 0.96 classification accuracy and within a timeframe of 5 min based on the responses of the chemical sensors.

Preparation of PP-g-(AA-MAH) Fibers Using Suspension Grafting and Melt-Blown Spinning and its Adsorption for Aniline.

This paper uses polypropylene (PP) as the matrix and acrylic acid (AA) and maleic anhydride (MAH) as functional monomers to prepare PP-g-(AA-MAH) fibers by suspension grafting and melt-blown spinning technology that are easy to industrially scale-up. The fibers can be used to adsorb aniline. Results showed that the grafting ratio reached the maximum of 12.47%. The corresponding optimal conditions were grafting time of 3 h, AA: MAH = 0.75, total monomer content of 55%, benzoyl peroxide 1.4%, xylene concentration of 6 mL/g PP, and deionized water content of 8 mL/g PP. Owing to its good fluidity and thermal stability, the product of suspension grafting can be used for melt-blown spinning. Infrared spectroscopic and nuclear magnetic resonance spectroscopic analyses indicated that AA and MAH were successfully grafted onto PP fibers. After grafting, the hydrophilicity of PP-g-(AA-MAH) fiber increased. Therefore, it had higher absorptivity for aniline and the adsorption capacity could reach 42.2 mg/g at 45 min and pH = 7. Moreover, the PP-g-(AA-MAH) fibers showed good regeneration performance.

Research on emissions controlling of coal-made Fischer–Tropsch process diesel/methanol unconventional pollutants

ABSTRACT Thirty unconventional gaseous substances in Fischer–Tropsch process diesel/methanol-mixed fuel with different methanol blending ratios were measured and classified for diesel engine pollutant discharge. The measurement results showed high concentrations of several unconventional pollutants, including propylene, 1,3 butadiene, acrolein, benzene, toluene, ethylbenzene, and xylene, accounting for approximately 83% of the total concentration. The methanol blending ratio was increased from 0 to 15%, the amounts of unconventional pollutants such as olefins, alkanes, and aromatic hydrocarbons were decreased by 38.4%, 27.7%, and 23.7%, respectively, and the amounts of aldehydes and ketones were increased by 31.2%. The amounts of unconventional pollutants such as 1,3 butadiene, n-hexane, and benzene were decreased by 36.6%, 28.8%, and 29.2%, and the amount of acrolein was increased by 28.7%. At maximum torque, aromatic hydrocarbon emissions were reduced by 23.8%, aldehyde and ketone emissions were reduced by 44.8%, olefin emissions were increased by 142.8%, and alkane emissions were reduced by 14.5%; compared to maximum torque conditions, olefins under calibration category emissions were increased by 41.2%, alkane emissions were increased by 8.8%, aromatic hydrocarbon emissions were increased by 9.5%, and aldehyde and ketone emissions were increased by 25%.

Indoor and outdoor concentrations of benzene, toluene, ethylbenzene and xylene in some Italian schools evaluation of areas with different air pollution

The air quality of indoor environments is an aspect of great importance and of growing interest, particularly considering the length of time that people stay in confined spaces. The objective of this study was to study the indoor and outdoor concentrations of benzene, toluene, ethylbenzene and xylene (BTEX) in 8 Italian schools, many of which are located in some of the most highly polluted areas in Italy. This wanted to provide useful information for understanding the status of air quality in sensitive indoor and outdoor areas (schools) and to support the development of recommendations and indications useful to territorial administrations in the improvement of environmental quality strategies. The sampling campaigns were performed with passive samplers from 2014 to 2015, studying both the hot and cold seasons. A common sampling and analytical protocol was applied in all the study areas. Passive sampler data were also compared with BTEX measurements from fixed-site monitoring stations selected as references for each school. Our findings showed the prevalence of low BTEX concentrations with relatively high values limited to toluene, ethylbenzene and xylene in a few monitoring sites and periods. The mean concentration values of benzene, toluene, ethylbenzene and xylene varied from 0.10 μg/m3 to 10.75 μg/m3, from 0.10 μg/m3 to 28.18 μg/m3, from 0.10 μg/m3 to 11.1 μg/m3 and from 0.10 μg/m3 to 14.45 μg/m3, respectively. In indoor environments, the concentrations were equal to or higher than the values measured outdoors in most cases, frequently reporting I/O ratios greater than 1.

Comparing BTEX concentration related to surgical smoke in different operating rooms

The available evidence on the indoor air quality of operating rooms (ORs) in the Low- and Middle-income Countries (LMICs) is very scarce. Moreover, there is no study on the comparing the concentration of indoor air pollutants in different ORs. Therefore, this study aimed to measure and compare the benzene, toluene, ethylbenzene and xylene (BTEX) concentrations in the air of different ORs in hospitals of Sabzevar, Iran. Moreover, carcinogenic and non-carcinogenic risk of exposure to these pollutants were assessed using Monte Carlo simulations technique. This cross-sectional study was based on volatile organic compounds (VOCs) passive sampling of eight ORs including General surgery, Curettage, Eye surgery, Neurosurgery, Orthopedic, Laparoscopic, Cesarean and Ear, nose, throat (ENT) in two monthly campaigns from November 2019 to February 2020. One-way ANOVA and Post-hoc analyses were used to compare the concentration of BTEX compounds in different ORs. The overall mean (standard deviation (SD)) of benzene, toluene, ethylbenzene, xylene and total BTEX concentrations were 10.0 (1.8), 7.2 (1.9), 1.8 (0.6), 0.4 (0.2) and 19.4 (4.1) μg/m3. The Curettage OR had the highest (12.93 μg/m3) and ENT OR had the lowest (7.42 μg/m3) benzene concentrations. The highest concentrations of toluene, ethylbenzene and total BTEX were observed in General surgery OR. The cancer risks of exposure to benzene in all ORs were higher than the acceptable range recommended by Unite State Environmental Protection Agency (USEPA, 1 × 106). However, the hazard quotient (HQ) values for all ORs were at safe level (HQ < 1). Overall, our study suggested that the concentrations of BTEX compounds were significantly difference in different ORs and benzene had a carcinogenic risk for personnel and surgical staff in different ORs.

Exposure levels of volatile organic compounds and potential health risks for passengers and workers at an intercity bus terminal

This work focuses on the concentration and health effects of volatile organic compounds (VOCs) at an intercity bus terminal in Taipei City, Taiwan. In this study, 36 VOCs were detected in the bus terminal, including 19 hazardous air pollutants. The measurement results indicate that ethanol, acetone, toluene, and methyl tert-butyl ether (MTBE) were the main VOCs dominating this bus terminal. Moreover, the average concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds was 106.0 μg/m3 inside the bus terminal, contributing to approximately 70% of the hazardous air pollutants. The measurement results suggest that traffic emissions, especially from diesel buses, were the major pollution sources in the bus terminal. The cancer risk for 1,3-butadiene, benzene, ethylbenzene, and naphthalene exceeded the suggested value by the U.S. EPA. In addition, the individual chronic hazard quotient of benzene was higher than the recommended level. The findings of this work imply that bus terminal workers face a potential health risk, which is a matter of concern.

Biomass Growth and Its Control in the Process of Biofiltration of Air Contaminated with Xylene on a Biotrickling Column Filled with Expanded Clay

Biofiltration of air polluted with xylene vapors was carried out for nearly two years in a large laboratory-scale installation with a volume of the bed of expanded clay equal to 32 dm3. During the experiment, different xylene inlet concentrations were applied, within the range from 300 to over 1500 mg/m3 at a linear gas flow rate of 0.008, 0.016, and 0.033 m/s, as well as 0.12 and 0.24 dm3 of medium dispensed every 3 h on top of the bed. The progress of the process was followed by measuring the xylene concentration at the inlet and outlet of the column, column mass, and gas flow resistance. The capability to purify air polluted with xylene with an average efficiency of approx. 90% was demonstrated. The process was interrupted by a significant increase in gas flow resistance, caused by a large growth of biomass, resulting in an increase in the mass of the bed by more than 45%. Both intensive rinsing of the bed with a stream of water, causing its fluidization, and rinsing and mixing after removing the bed from the column allowed to reduce flow resistance to a value close to the initial one. To ensure the supply of biogenic elements, it was necessary to periodically spray the bed with a solution of the medium in an amount of up to about 0.1 dm3/h/m3 of purified air.

A rapid removal of xylene vapor from environmental air based on bismuth oxide coupled to heterogeneous graphene/ graphene oxide by UV photo-catalectic degradation-adsorption procedure

• UV photo-catalectic degradation coupled to adsorption (UV-PCDA) was used for efficient removal of xylene from air. • Xylene was semi degradated to main fragments by bismuth oxide nanoparticles and UV irradiation. • The fragments of xylene adsorbed on the surface of graphene/graphene oxide (NG/NGO). A simple and fast method based on bismuth oxide nanoparticles coupled to heterogeneous graphene/ graphene oxide (BONPs-NG/NGO) was used for the rapid removal of xylene vapor from environmental air by UV photo-catalectic degradation-adsorption procedure (UV-PCDA). By dynamic system, the xylene vapor in pure air was generated in the chamber and flowed to BONPs-NG/NGO sorbent inside in quartz glass tube with UV lamp radiation (QGT-UV) at optimized conditions. In the present of BONPs and UV irradiation, xylene and intermediates ( o-xylene, p-xylene, m-xylene ) were semi degradated to main fragments by radicals and adsorbed on the surface of NG/NGO (200 mg). After degradation, the main fragments of xylene determined with gas chromatography (GC–MS). Based on the results, the removal efficiency of xylene based on BONPs and BONPs-NG/NGO were obtained 38.8 % and 98.7 %, respectively. By static system in presence of UV irradiation, the capacity adsorption of xylene with 200 mg of BONPs-NG/NGO and NG/NGO was obtained 223 mg g −1 and 134.6 mg g -1 in 85 °C for 10 min, respectively. The validation of methodology was obtained by spiking of different concentrations of standard xylene in pure air.

Seasonal Variation, Sources, and Health Risk Assessment of Indoor/Outdoor BTEX at Nursery Schools in Hanoi, Vietnam

There is an increasing research interest in indoor air quality at schools as children who are among the most sensitive to air pollution spend a lot of time indoors. This study aims to estimate BTEX levels, sources, and assess their health risk at ten preschools in Hanoi, Vietnam. Two sampling campaigns were conducted in November and December, 2017, and May and June, 2018, with a total of 80 samples collected. BTEX were sampled by mini air samplers, and the analysis was performed by using GC/MS. During class, indoor concentrations of benzene, toluene, ethylbenzene, and xylene were within the range of 1.22–6.01, 1.6–63.4, 0.94–6.34, and 0.86–3.52 μg m−3, while corresponding values obtained in the absence of children were 1.62–6.90, 1.20–125.3, 0.58–25.1, and 0.60–6.65 μg m−3, respectively. Indoor/outdoor ratios of BTEX varied from school to school, and ranged from 0.4 to 14.2, implying the presence of indoor emission sources. Insignificant indoor sources of benzene were found in all examined schools, whereas there were sources of toluene, ethylbenzene, and xylenes, probably associated with paint’s solvents, glues, and cleaning agents. Outdoor BTEX originated from the common sources, being mainly composed of automobile traffic. There was insignificant cancer and non-carcinogenic risk to children at the monitored preschools, with LCR values within the range of 0.059–6.6 × 10−5, and HQ values below 0.31. Monte Carlo simulation revealed that indoor and outdoor concentrations of BTEX influenced the most the results on lifetime cancer risk for indoors and outdoors, with a typical contribution of more than 90% to LCR variance.