BTEX Emissions Research Articles

Prediction of variables involved in TEG Dehydration using hybrid models based on boosting algorithms

The extraction of gas from fields often involves impurities, necessitating natural gas processing to separate these impurities. This process typically entails the removal of acid gases (such as carbon dioxide and hydrogen sulfide) and dehydration, commonly achieved through absorption using triethylene glycol (TEG). Efforts to minimize BTEX emissions and maintain optimal dry gas water content are pivotal for enhancing the economic and environmental sustainability of natural gas processing. In this study, the accurate prediction of BTEX and dry gas water contents is aimed by boosting-based methods and hybridization techniques. Four hybrid models, including XGBoost, CatBoost, HGBR, and LightGBoost, were developed in conjunction with the Arithmetic Optimization Algorithm (AOA) meta-heuristic algorithm to optimize and fine-tune hyperparameters. Through a comprehensive case study and comparison of various evaluation indices, the XGBoost-AOA hybrid model emerged as the most accurate in predicting both outputs. Hence, we recommend the XGBoost algorithm optimized with the AOA algorithm as the preferred approach for predicting BTEX and dry gas water contents in natural gas processing.

Analysis Study of Available Alternatives for Mitigation of Aromatic Hydrocarbon Emissions from a Glycol Dehydration Unit

A natural gas (NG) dehydration unit based on glycol absorption is considered one of the most important gas processing units, aiming to decrease water content and consequently adjust its dew point. However, during this process, not only water is absorbed by the glycol solvent, but also some aromatic compounds, including benzene, toluene, ethylbenzene, and xylene (BTEX), in addition to volatile organic compounds (VOC), are absorbed. These compounds are released during glycol regeneration into the atmosphere, resulting in environmental pollution and consequent catastrophic mental and physical health problems. This study aims to minimize BTEX emissions while ensuring efficient dew point control. Various strategies have been adopted to control BTEX emissions, but the present work focuses on optimizing operating conditions and investigating the influence of operational variables on BTEX emissions, as well as NG water content. LINGO optimization software and HYSYS (version 11) are used to find the plant’s optimum conditions for minimizing BTEX emissions and satisfying efficient dew point control. Simulation results show that stripping gas, triethylene glycol (TEG) circulation rate, and inlet feed gas temperature significantly affect BTEX emissions. The proposed optimum operating conditions in this work resulted in a reduction in BTEX emissions by about 81% while satisfying the required NG dew point. Furthermore, two quadratic equations are developed based on regression analysis for efficient calculation of the BTEX emissions and water dew point at any operational variables.

BTEX Assessment among Informal Charcoal-Burning Food Traders for Cleaner and Sustainable Environment

This study assessed the cleaner and sustainable environment by measuring emission levels of benzene, toluene, ethylbenzene, and xylene (BTEX) from informal food traders using charcoal as the primary source of energy at a flea market in Fordsburg, Johannesburg. Volatile organic compounds (VOCs) were measured using a real-time monitor (MiniRae 3000 photoionization detector); an indoor air quality (IAQ) monitor was used to monitor environmental parameters and passive samplers in the form of Radiello badges, which were used to determine BTEX emissions from charcoal used during food preparation. Measurements were taken at 1.5 m above ground assuming the receptor’s breathing circumference using PID and Radiello. PID data were downloaded and analyzed using Microsoft Excel(Version 2019). Radiellos were sent to the laboratory to determine the BTEX levels from the total VOCs. The total volatile organic compound (TVOC) concentration over the combustion cycle was 306.7 ± 62.8 ppm. The flaming phase had the highest VOC concentration (547 ± 110.46 ppm), followed by the ignition phase (339.44 ± 40.6 ppm) and coking with the lowest concentration (24.64 ± 14.3). The average BTEX concentration was 15.7 ± 5.9 µg/m3 corresponding to the entire combustion cycle. BTEX concentrations were highest at the flaming phase (23.6 µg/m3) followed by the ignition (13.4 µg/m3) and coking phase (9.45 µg/m3). Ignition phase versus the flaming phase, there was a significant difference at 95% at a p-value of 0.09; ignition phase versus the coking phase, there was a significant difference at 95% at a p-value of 0.039; and coking phase versus the flaming phase, there was a significant difference at 95% at a p-value of 0.025. When compared to the occupational exposure limits (OELs), none of the exposure concentrations (BTEX) were above the 8 h exposure limit. The findings of this study suggest that charcoal, as a source of energy, can still be a useful and sustainable fuel for informal food traders. Shortening the ignition and flaming phase duration by using a fan to supply sufficient air can further reduce exposure to VOCs.

An assessment of atmospheric concentrations and spatiotemporal variation of BTEX and associated pollutants in India

Benzene, toluene, ethylbenzene, and xylene (BTEX) pollution poses a serious threat to public health and the environment because of its respiratory and neurological effects, carcinogenic properties, and adverse effects on air quality. BTEX exposure is a matter of grave concern in India owing to the growing vehicular and development activities, necessitating the assessment of atmospheric concentrations and their spatial variation. This paper presents a comprehensive assessment of ambient concentrations and spatiotemporal variations of BTEX in India. The study investigates the correlation of BTEX with other criteria pollutants and meteorological parameters, aiming to identify interrelationships and diagnostic indicators for the source characterization of BTEX emissions. Additionally, the paper categorizes various regions in India according to the Air Quality Index (AQI) based on BTEX pollution levels. The results reveal that the northern zone of India exhibits the highest levels of BTEX pollution compared to central, eastern, and western regions. In contrast, the southern zone experiences the least pollution with BTEX. Seasonal analysis indicates that winter and post-monsoon periods, characterized by lower temperatures, are associated with higher BTEX levels due to the accumulation of localized emissions. When comparing the different zones in India, high traffic emissions and localized activities, such as solvent use and solvent evaporation, are found to be the primary sources of BTEX. The findings of the current study aid in source characterization and identification, and better understanding of the region's air quality problems, which helps in the development of focused BTEX pollution reduction and control strategies.

BTEX in indoor air of barbershops and beauty salons: Characterization, source apportionment and health risk assessment

BackgroundVolatile organic compounds, mainly BTEX, are among the pollutants of concern in beauty salons and barbershops that threaten both staff personnel and clients' health. This study aimed to determine the concentration of BTEX in barbershops and beauty salons and assess the carcinogenic and non-carcinogenic risks based on the actual risk coefficients. Also, possible sources of BTEX were determined. MethodSamples were collected by passive sampling. Quantitative and qualitative measurements of BTEX compounds were performed using gas chromatography-mass spectrometry (GC-MASS). Subsequently, the health risks were assessed according to the US Environmental Protection Agency. SPSS24 software and positive matrix factorization (PMF) analysis were used for statistical analysis and source apportionment respectively. ResultsToluene is the most abundant compound in beauty salons, with a maximum concentration of 219.4 (μg/m3) in beauty salons. Results indicated that the mean ELCR value estimated for benzene regarding female staff exposure (1.04 × 10−5) was higher than that for men (4.05 × 10−6). Also, ELCR values of ethylbenzene for staff exposure were 2.08 × 10−6 and 3.8 × 10−6 for men and women, respectively, and possess possible carcinogenesis risks. ConclusionUse of solvents and cosmetic products, improper heating systems, and type of service are the sources that probably contribute to BTEX emissions in beauty salons. It is necessary to follow health guidelines and conduct continuous monitoring for their implementation, in addition to setting a mandated occupational regulation framework or air quality requirements, to improve the health conditions in beauty salons.

Equilibrium study of benzene, toluene, ethylbenzene, and xylene (BTEX) from gas streams by black pine cones-derived activated carbon

Considering environmental emissions, benzene, toluene, ethylbenzene, and xylene (BTEX) are widely used as raw materials in industrial processes. They also affect humans via inhalation, which must be reduced due to their toxicity before further operation. Notably, the leading technologies have tried to remove BTEX emissions with several methods. Continuous innovation of adsorbents is constantly developing in the adsorption mechanism, which has been developed based on waste biomass. Pinus nigra cones is a lignocellulosic raw material that is fast-growing on various soils and found abundant in nature as a precursor. It may be cheaply found available from some natural product vendors. It was used to prepare activated carbon by chemical activation with phosphoric acid (H3PO4), potassium hydroxide (KOH), sulfuric acid (H2SO4), lithium hydroxide (LiOH), zinc chloride (ZnCl2), sodium hydroxide (NaOH) as the activating agents between at 550–850 °C for 2 h. Fourier transforms infrared spectrometer (FT-IR), thermogravimetric analyzer (TGA), scanning electron microscopy (SEM), and N2 gas adsorption–desorption analyzer were used for KAS-ACs characterization. The high BTEX adsorption capacities by ZnCl2 activated carbons were slightly higher than (SBET: 1849 m2/g for KAS-AC91, and Vtotal: 0.44 cm3/g) others. ANOVA results show a high correlation for the KAS-ACs production with ZnCl2, and there was a statistically significant difference between the mean of Vmicro (cm3/g) with activation temperatures p-values<0.05. The removal capacities at 5 μg/L have been done to evaluate using Tenax TA tubes were 92, 96, 88, and 94.08% for benzene, toluene, ethylbenzene, and xylene, respectively. The maximum adsorption capacity for benzene, toluene, ethylbenzene, and xylene onto the KAS-AC91 in the following order: Xylenes (181 μg/g)>Toluene (206 μg/g)>Benzene (171 μg/g)>Ethylbenzene(201 μg/g). This suggests that the KAS-AC91 is an efficient BTEX adsorbent and represents a promising attempt to enhance BTEX adsorption in indoor air quality.

Identify Primary Air Pollution Sources of BTEX by Using Positive Matrix Factorization (PMF): A Case Study of Ho Chi Minh City, Vietnam.

Ho Chi Minh City (HCMC) is one of the main socioeconomic and financial centers of Vietnam. The city also faces serious air pollution. However, the city polluted with benzene, toluene, ethylbenzene, and xylene (BTEX) has rarely been studied. We used positive matrix factorization (PMF) to analyze BTEX concentrations measured at two sampling locations to identify the main sources of BTEX in HCMC. The locations represented residential area (i.e., To Hien Thanh) and industrial area (i.e., Tan Binh Industrial Park). At the To Hien Thanh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 6.9, 14.4, 4.9, and 12.7µg/m3, respectively. At the Tan Binh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 9.8, 22.6, 2.4, and 9.2µg/m3, respectively. The results showed that PMF was a reliable model for source apportionment in HCMC. Traffic activities were the main sources of BTEX. Besides, industrial activities also contributed to BTEX emissions, especially the location near the industrial park. The majority of BTEXs at the To Hien Thanh sampling site come from traffic sources accounting for 56.2%. Activities from traffic and photochemical reactions (42.7%) and industrial sources (40.5%) were the main sources affecting BTEX emissions at the sampling site of Tan Binh Industrial Park. This study can be used as a reference for mitigation solutions to reduce the BTEX emission in HCMC.

BTEX profile and health risk at the largest bulk port in Latin America, Paranaguá Port

Port-related activities have a detrimental impact on the air quality both at the point of source and for considerable distances beyond. These activities include, but are not limited to, heavy cargo traffic, onboard, and at-berth emissions. Due to differences in construction, operation, location, and policies at ports, the site-specific air pollution cocktail could result in different human health risks. Thus, monitoring and evaluating such emissions are essential to predict the risk to the community. Environmental agencies often monitor key pollutants (PM2.5, PM10, NO2, SO2), but the volatile organic carbons (VOCs) most often are not, due to its analytical challenging. This study intends to fill that gap and evaluate the VOC emissions caused by activities related to the port of Paranaguá - one of the largest bulk ports in Latin America - by characterizing BTEX concentrations at the port and its surroundings. At seven different sites, passive samplers were used to measure the dispersion of BTEX concentrations throughout the port and around the city at weekly intervals from November 2018 to January 2019. The average and uncertainty of BTEX concentrations (µg m-3) were 0.60 ± 0.43, 5.58 ± 3.80, 3.30 ± 2.41, 4.66 ± 3.67, and 2.82 ± 1.95 for benzene, toluene, ethylbenzene, m- and p-xylene, and o-xylene, respectively. Relationships between toluene and benzene and health risk analysis were used to establish the potential effects of BTEX emissions on the population of the city of Paranaguá. Ratio analysis (T/B, B/T, m,p X/Et, and m,p X/B) indicate that the BTEX levels are mainly from fresh emission sources and that photochemical ageing was at minimum. The cancer risk varied across the sampling trajectory, whereas ethylbenzene represented a moderate cancer risk development for the exposed population in some of the locations. This study provided the necessary baseline data to support policymakers on how to change the circumstances of those currently at risk, putting in place a sustainable operation.

Associated health risk assessment due to exposure to BTEX compounds in fuel station workers.

The purpose of this review study was to assess the risk of exposure to BTEX compounds in gas station workers and operators. The main components of BTEX compounds are Benzene, Toluene, Ethyl benzene and Xylene. Petroleum, coal large quantities in crude oil and its products are the most important sources of BTEX compounds. These compounds have both high solubility (found in surface and underground waters) and evaporate quickly. Gas stations are one of the most important sources of emission of these compounds in communities. Workers who work in these places have a lot of exposure to these compounds. Exposure to these dangerous compounds can cause many problems for workers. This study was a narrative review article. According to different databases: PubMed, Web of Science, Springer, Cochran and Science Direct, 451 articles were retrieved. 55 full-text articles entered into the analysis process. Finally, 32 articles were selected in this study. The search was restricted to English-language papers published between 1 February 1995 and 13 August 2022. The results of our study showed that the carcinogenic risk (ILCR) for gas station workers in Bangkok (1.82 ∗ 10-4 - 2.50 ∗ 10-4), Shiraz (6.49∗10-7 - 1.27 ∗ 10-5), Brazil (1.82 ∗ 10-4), Ardabil (390∗10-6 ± 1884 ∗ 10-6) and Johannesburg (3.78 ∗ 10-4) was high. The non-cancer risk for oil industry workers of Dilijan (Iran) who were exposed to toluene was also reported in the range of 10-6∗176. The health of gas station workers is affected by exposure to BTEX and gasoline vapor emissions. According to the result this study, BTEX compounds cause genotoxic changes, chromosomal and genetic abnormalities. Genotoxicity at high levels in gas station workers can cause cancerous and non-cancerous risks. Improving the production process of diesel fuel and gasoline in refineries, using periodical examinations of workers and operators at gas and fuel stations, using Euro 4 and 5 fuels, and replacing worn out cars can play an important role in reducing the emission of BTEX compounds and thus reducing health risks and carcinogenic.

Probabilistic human health risk assessment and contributions to ozone and SOA formation potentials associated with BTEX and formaldehyde emissions in a tropical city (Salvador, Bahia, Brazil)

Probabilistic human health risk assessment and contributions to ozone and SOA formation potentials associated with BTEX and formaldehyde emissions in a tropical city (Salvador, Bahia, Brazil)

BTEX Atmospheric Levels and Health Risk in an Urban Site in Ciudad del Carmen, Campeche

Benzene, toluene, ethylbenzene, and xylenes (BTEX) were measured in ambient air in an urban site of Ciudad del Carmen, Campeche during spring 2022. Samples were collected during the morning (from 07:00 to 08:00 h), midday (from 14:00 to 15:00 h) and afternoon (from 18:00 to 19:00 h) using glass tubes packed with activated carbon, at a controlled air flow of 1.5 L/min. Samples were analyzed by gas chromatography with flame ionization detection. The relative abundance in ambient air of BTEX was the following: benzene (9.197 μg/m^3) &gt; toluene (8.953 μg/m^3) &gt; xylenes (7.789 μg/m^3) &gt; ethylbenzene (7.538 μg/m^3). The statistical analysis revealed that BTEX compounds had strong correlations between each other, indicating that they were originated from common sources. From the meteorological analysis, it was found that the prevailing winds blew from the east and southeast, indicating that vehicular emissions coming from avenues located in these directions may have contributed to the BTEX levels in the study site. Principal component analysis and BTEX ratios (T/B and X/Ebz) revealed that vehicular emissions and fresh local air masses influenced the BTEX concentrations during the study period. From the health risk analysis, cancer risk coefficients exceeded the acceptable level (1 × 10 -6), thus exposed population may be at a possible risk of developing cancer in the lifetime due to the inhalation of BTEX at the measured concentrations. These results will be a useful tool for local authorities in order to establish control measures focused on the reduction of BTEX emissions and the improvement of the air quality in the study area.

An Innovative Method for BTEX Emission Inventory and Development of Mitigation Measures in Developing Countries—A Case Study: Ho Chi Minh City, Vietnam

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are carcinogenic pollutants. However, the average concentration in 1 h of some pollutants belonging to BTEX, such as benzene, in Ho Chi Minh City (HCMC) is higher than the national standard QCVN 06:2009/BTNMT by about ten times. This research is the first to calculate the emission of BTEX for developing countries on a city scale. This paper developed a method to calculate cold emission factors based on hot emission factors for BTEX. Five spreadsheets developed and calculated these cold emission factors for five vehicle categories. A comprehensive emission inventory (EI) for BTEX was conducted in HCMC to determine the cause of BTEX pollution. An innovative methodology with bottom-up and top-down combination was applied to conduct BTEX EI, in which the EMISENS model was utilized to generate the EI for road traffic sources, and the emission factors method was utilized for other emission sources. Among emission reasons, motorcycles contribute the highest to HCMC air pollution, responsible for 93%, 90%, 98.9%, and 91.5% of benzene, toluene, ethylbenzene, and xylene, respectively. Cars contributed 5%, 6%, 0.8%, and 6.5% of benzene, toluene, ethylbenzene, and xylene, respectively. For LDVs, the emission from benzene, toluene, ethylbenzene, and xylene accounted for 1%, 2%, 0.2%, and 1.9%. The major reasons for point sources were metal production, which had 1%, 2%, and 0.1% for benzene, toluene, ethylbenzene, and xylenes emissions. The area source had a minority emission of total BTEX in Ho Chi Minh City. Our findings can be used to invest in the most significant sources to reduce BTEX in HCMC. Our approach can be applied in similar urban areas in BTEX EI. This research also developed nine measures to reduce BTEX in HCMC for human health protection.

Inhalation risk to PAHs and BTEX during barbecuing: The role of fuel/food type and route of exposure

The manuscript presents an innovative and holistic approach to quantifying PAHs and BTEX emissions from the grilling process and indicates a novel driven–toxicity-based solution to recognize health effects related to BBQ emissions. The exposure scenario includes the type of grilling device, food type, and individual attitudes, but also a keen understanding of the broad health implications related to the gaseous/particulate PAHs emission, or age-related effects. The calculated incremental lifetime cancer risk (ILCR) associated with the exposure to PAH congeners and BTEX indicates an unacceptable level in the case of charcoal and briquette grilling with the highest values for professional cooks. The sum of 15 PAH concentrations in grilled foods was highest for meat grilling over charcoal briquettes – 382,020.39 ng/m3 and lowest for meat grilling on a gas grill – 1442.16 ng/m3. The emissions of BTEX from lump charcoal grilling were 130 times higher compared to the gaseous grill. In all considered scenarios lump-charcoal and charcoal briquettes grilling derive the ILCR above the 10−4, indicating negative effects of traditional grills on human health. The paper completes knowledge of wide-ranging health implications associated with BBQs, a topic that is almost completely unaddressed among the scientific community and policymakers.

Laser-based selective BTEX sensing using deep neural networks.

A mid-infrared absorption-based laser sensor is developed for selective and simultaneous benzene, toluene, ethylbenzene, and xylenes (BTEX) measurements under ambient conditions. The sensor is based on a distributed feedback inter-band cascade laser emitting near 3.3 µm. Wavelength tuning and deep neural networks were employed to differentiate the broadband absorbance of BTEX species. The sensor was validated with gas mixtures and real-time measurements were demonstrated at a temporal resolution of 1 s. Minimum detection limits for BTEX in air are 8, 20, 5, and 46 ppm, respectively. This sensor can be utilized to monitor BTEX emissions in the petrochemical, rubber, and paint industries to avoid hazardous health effects.

BTEX Emissions in the Logistics of Middle Distillates: Diesel Oil

Besides technological processes; logistics; and the use of petrol and light solvents, which are widely known as pollutants, the sources of BTEX hydrocarbon contributing to air pollution may also include other petroleum products and fuels that feature higher boiling points and that have not yet been associated with this issue. In this study, the contents of benzene; toluene; ethylbenzene; and o-, m-, and p-xylene were evaluated in 25 commercial samples of diesel oils; the gaseous phase in thermodynamic equilibrium with liquid diesel oil at 40 °C was then evaluated. Based on the experimental results, it was found that benzene concentration in the gaseous phase is five to more than fifteen times higher than the limits set by regulations for benzene concentration in the air at a work place (1.6 mg/m3) and cannot be compared with the limits set by regulations for annual average basal levels of benzene concentration in the air (5 µg/m3). The research revealed that diesel oil is a potential source of environmental contamination from BTEX hydrocarbons, in particular benzene.

Reliability-Based Robust Multi-Objective Optimization (RBRMOO) of Chemical Process Systems: A Case Study of TEG Dehydration Plant

Natural gas (NG) production has significantly increased in the past decade as new unconventional oil and gas wells are being discovered. NG as obtained from the wellhead requires processing before being considered as pipeline grade. The process consists of the removal of acidic gases followed by dehydration. NG processing is associated with toxic emission having substantial environmental and health impact. Difficulty in NG processing arises from varied flow rate and uncertain feed composition that provides a challenge in efficient design as well as finding the optimal operating condition. The present work used a stochastic approach to characterize natural gas composition and its importance on the product and waste emission is studied. Under the uncertain feed composition, optimal operating condition of the controllable variables was attained by a reliability-based robust multi-objective optimization (RBRMOO) technique that mitigates BTEX emission while fulfilling NG pipeline specification. Chemical process simulator is used to find the impact of the control process settings and variation of uncertain feed condition on NG dehydration and BTEX emission. The best prediction models were developed using machine learning algorithm, chosen from a family of metamodels. RBRMOO is performed using metaheuristic algorithm to determine the optimal process condition of the control variables. The impact of uncertain feed composition in process modeling and subsequent optimization demonstrates optimal process condition where the rate of emission is lower by ~83 ton/yr when compared to that from the deterministic model where median value of uncertain feed composition is used for analysis, portraying the limitations of traditional sustainability assessment methods that do not account for uncertainty.

Study of the effectiveness of landfill final cover in reducing BTEX emissions

Study of the effectiveness of landfill final cover in reducing BTEX emissions

Emission of BTEX compounds from the frying process: Quantification, environmental effects, and probabilistic health risk assessment

Frying is one of the cooking methods which generates mono aromatic hydrocarbons, including benzene, toluene, ethylbenzene, and xylene (BTEX); subsequently, it affects health through carcinogenic (CR) and non-carcinogenic risks (n-CR). However, their environmental effects known by secondary organic aerosols (SOA) and ozone formation potential (OFP) were also attended by many scientists. Therefore, this study quantified the BTEX emissions from 4 types of most commonly used edible oils (canola, corn, sunflower, and blend) under various frying conditions of temperatures and food additives. Furthermore, the effects of the chemicals in the light of health (CR and n-CR) and environment (SOA and OFP) were also investigated. The study results showed that higher temperatures could significantly increase the emissions, while the addition of food ingredients significantly reduces the emissions. The rank order of emitted chemical was obtained as T > B > E > X. The blend had the most emission among oils, followed by, in descending order, corn, sunflower, and canola. In association with environmental effects, the orders of X > T > E > B and T ∼ E > X > B were obtained for OFP and SOA, respectively. THQ for blend, corn, canola, and sunflower oils was higher than 1 (1.76, 1.35, 1.27, and 1.002, respectively), showing a considerable n-CR when the hood was off. In this respect, TCR for the oils (1.78 × 10−4, 1.45 × 10−4, 1.39 × 10−4, and 1.05 × 10−4, respectively) shown the probable risk for all oils. Moreover, hood switching reduced the risk by about 11–81%.

Optimizing TEG Dehydration Process under Metamodel Uncertainty

Natural gas processing requires the removal of acidic gases and dehydration using absorption, mainly conducted in tri-ethylene glycol (TEG). The dehydration process is accompanied by the emission of volatile organic compounds, including BTEX. In our previous work, multi-objective optimization was undertaken to determine the optimal operating conditions in terms of the process parameters that can mitigate BTEX emission using data-driven metamodeling and metaheuristic optimization. Data obtained from a process simulation conducted using the ProMax® process simulator were used to develop a metamodel with machine learning techniques to reduce the computational time of the iterations in a robust process simulation. The metamodels were created using limited samples and some underlying phenomena must therefore be excluded. This introduces the so-called metamodeling uncertainty. Thus, the performance of the resulting optimized process variables may be compromised by the lack of adequately accounting for the uncertainty introduced by the metamodel. In the present work, the bias of the metamodel uncertainty was addressed for parameter optimization. An algorithmic framework was developed for parameter optimization, given these uncertainties. In this framework, metamodel uncertainties are quantified using real model data to generate distribution functions. We then use the novel Better Optimization of Nonlinear Uncertain Systems (BONUS) algorithm to solve the problem. BTEX mitigation is used as the objective of the optimization. Our algorithm allows the determination of the optimal process condition for BTEX emission mitigation from the TEG dehydration process under metamodel uncertainty. The BONUS algorithm determines optimal process conditions compared to those from the metaheuristic method, resulting in BTEX emission mitigation up to 405.25 ton/yr.

Concentrations, sources, and health risk associated with exposure to BTEX at ten sites located in an urban-industrial area in the Bajio Region, Mexico

The purpose of this study was to study the spatial and temporal variation of BTEX in the ambient air of Leon, Guanajuato, Mexico, to assess the inhalation health risk to the local population from exposure to these compounds. BTEX were monitored using passive samplers during two sampling seasons (rainy 2019 and cold dry 2020), and samples were analyzed by gas chromatography with flame ionization detection. BTEX ratios and meteorological analysis suggested that the concentrations were mainly influenced by vehicular and local sources located to the SE of the study area. The sum of average concentrations of BTEX in rainy and cold dry seasons were of 3.52 ± 0.36 µg m−3 and 4.11 ± 0.38 µg m−3, respectively. Mean concentrations were of 0.74, 1.59, 0.48, and 0.69 µg m−3, for benzene, toluene, ethylbenzene, and p-xylene, respectively. The highest levels of BTEX were found in sites with an urban land-use type of medium-intensity industrial zones with high population density. The lower BTEX concentrations found during the rainy season were probably due to higher solar radiation and temperatures that favored their photochemical degradation. Bi-variate and multivariate analysis showed that the BTEX species were strongly correlated with each other and with temperature and solar radiation, indicating that they originated from common sources. Benzene and toluene correlated strongly with CO and SO2, indicating that they could originate from vehicular exhaust emissions and high-sulfur fuel combustion sources. The health risk assessment showed that the Leon city adult population is at possible risk of developing cancer in their lifetime due to exposure to the measured benzene levels, but indicated no risk of contracting respiratory and cardiovascular diseases due to inhalation of BTEX. The results suggest the need for BTEX emissions reduction policies in the study area, as well as the establishment of a Mexican standard that regulates the maximum permissible limit of these pollutants in ambient air in order to protect the health of the population.