Exhaust Gas Research Articles

Pollution characteristics, source analysis, and health risk assessment of polycyclic aromatic hydrocarbons in atmospheric PM2.5: a case study in Xi’an, China

ABSTRACT Air samples were collected at the Lianhu (urban) and Yanta (semi-urban) regions between January 2020 and December 2023 to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) in Xi’an, which is an important tourist city in China. The concentration of PAHs was ascertained using liquid chromatography. The concentration of Σ16PAHs in Xi’an was 0.13–105.02 ng/m3, while the concentration of Σ16PAHs for the sampling regions at Lianhu and Yanta were 0.13–105.02 ng/m3 and 0.34–82.64 ng/m3, respectively. PAHs with 4–5 rings were the predominant PAHs pollutants in Xi’an, mainly from coal combustion and automobile exhaust. Risks through inhalation to three groups, adult males, adult females, and children, were estimated. The incremental lifetime cancer risk (ILCR) value for local adults and children were less than 10−6, considered to be at a safe level. However, the ILCR is relatively close to the minimum risk threshold (10−6), and it still needs to be highly valued.

Flow Induced noise prediction in automobile exhaust systems using Computational Fluid Dynamics (CFD)

Flow Induced noise prediction in automobile exhaust systems using Computational Fluid Dynamics (CFD)

CO2 and O2 Separation Dual-Phase Membranes for Diesel Heavy-Duty Vehicles Applications

Diesel-engine Heavy-Duty Vehicle (HDV) exhaust gas mixture contains pollutants including unburned hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter. A catalyst-based emission control system is commonly used to eliminate the above pollutants. However, the excess of oxygen that exists in the exhaust gasses of diesel engines hinders the efficient and selective reduction of nitrogen oxides over conventional catalytic converters. The AdBlue® solution, which is currently used to eliminate nitrogen oxides, is based on ammonia. The latter is toxic in high concentrations. The aim of this work is to develop an Oxygen Reduction System (ORS) to remove oxygen from the exhaust gas of diesel engines, allowing the successful catalytic reduction of nitrogen oxides on a reduction catalyst without the need for ammonia. The ORS device consists of dense composite dual-phase membranes that allow the permeation of oxygen and carbon dioxide. Even though the oxygen concentration gradient across the membranes favors oxygen spontaneous diffusion from the atmosphere to the exhaust gas, the carbonate ion-based technology proposed herein utilizes the big difference in the concentration of carbon dioxide across the membrane to remove oxygen without any power consumption requirement. The results of this study are promising for the application of O2 reduction in diesel HDVs.

Analysis of vehicle carbon emission characteristics on expressways in mountainous plateau areas based on the coupled simulation of CarSim/TruckSim and MOVES.

Expressways in mountainous plateau areas exhibit complex driving conditions and harsh climatic characteristics that continuously impact vehicle carbon emissions throughout their entire lifecycle and determine the carbon emission levels of expressways during the operational period. To study the carbon emission characteristics of expressways in the western Sichuan Plateau mountainous area, a coupling simulation analysis method combining CarSim/TruckSim simulation software and the Motor Vehicle Emissions Simulator (MOVES) was employed to analyze the spatial distribution characteristics of vehicle-specific power (VSP). This analysis was based on the alignment data and operational environment of the Wenchuan‒Barkam Expressway in the mountainous area of the western Sichuan Plateau. A conversion formula was established to calculate the cumulative VSP per second and total carbon emissions of each unit. Statistical analysis was conducted on the distribution of carbon emissions equivalent per kilometer across the different alignment units. Distribution ranges of carbon emissions equivalent per kilometer for light-duty vehicles (LDVs) and heavy-duty vehicles (HDVs) at each alignment unit were 60‒240 g and 100‒1600 g, respectively. The grey relational analysis method was used to quantify the relationship between the carbon emissions equivalent per kilometer of alignment units, circular curves radius, and average grade. Based on the vertical variations in climatic changes with altitude in the mountainous plateau area, a comparative analysis was performed on the trends in the effects of altitude, season, and vehicle starting frequency on carbon emissions. Frequent vehicle starts significantly impacted carbon emissions, and this impact was significantly higher in winter than in summer. Carbon emissions equivalent of the LDV and HDV starting twice on average in summer were approximately 1.09- and 1.04-times higher, respectively, than that when vehicles were started 0.5 times; whereas, in winter, they were 1.17- and 1.07-times higher, respectively.

Analysis and Evaluation of Potential Adsorbent for CO2 Capture in a CI Engine Exhaust: An Experimental Study

Analysis and Evaluation of Potential Adsorbent for CO2 Capture in a CI Engine Exhaust: An Experimental Study

Comparative Evaluation of the Effect of Exhaust Gas Recirculation Usage on the Performance Characteristics and Emissions of a Natural Gas/Diesel Compression-Ignition Engine Operating at Part-Load Conditions

The use of natural gas as an alternative fuel in dual-fuel compression-ignition engines can lead to a substantial reduction in the majority of pollutant emissions compared to fossil fuels, while the thermal efficiency of the engine can be maintained at adequate levels. Its usage has increased widely in recent years, and significant efforts have been made to investigate the inherent physical and chemical processes that take place during this engine’s combustion, as well as the parameters that affect the operation of the engine and use natural gas as energy source. The scope of this study is to investigate the effect of EGR temperature (cold and hot) and rate (10% and 20%) on the performance characteristics and emissions of a dual-fuel compression-ignition engine operating at a specific engine operating point under dual-fuel (diesel–natural gas) conditions. For this reason, a phenomenological two-zone combustion model was developed. The results of the model were validated against the experimental data obtained from a single-cylinder direct-injection, turbocharged compression-ignition dual-fuel research engine operated under part-load conditions (IMEP = 0.52 Mpa and engine speed = 1500 rpm) and at various replacement percentages of diesel using methane (which was treated as a natural gas surrogate). The model results were in good agreement with the experimental results, revealing the ability of the model to be used in the aforementioned EGR analysis. The results of the study revealed that engine operation with 10% cold EGR does not significantly affect the engine performance characteristics, and combined with the addition of 80% gaseous fuel energy, can lead to a substantial reduction in NO and soot emissions, with a moderate increase in CO emissions. On the other hand, a significant finding of the present work is that engine operation with hot EGR under the investigated operating conditions, even though it had a beneficial effect on NO-specific emissions, led to a reduction in engine efficiency and may raise issues regarding the mechanical strength of the engine.

Identification of particulate matter (PM10 and PM2.5) sources using bivariate polar plots and k-means clustering in a South American megacity: Metropolitan Area of Lima-Callao, Peru.

The identification of different air pollution sources is essential to effectively control atmospheric pollution, particularly in megacities of emerging countries with rapid economic development, such as the Metropolitan Area of Lima-Callao (MALC). The objective of this research was to identify the main sources of particulate matter pollution by applying bivariate polar plots and the k-means clustering algorithm. These statistical techniques were applied to hourly in situ data of four variables collected over a 5-year period (2015-2019) by the Automatic Air Quality Monitoring Network of the MALC: wind direction, wind speed, PM10, and PM2.5 concentrations. Average PM10 concentrations ranged from 34μgm-3 (CDM station) to 126.7μgm-3 (VMT station), while average PM2.5 concentrations ranged from 16.8μgm-3 (CDM station) to 41.2μgm-3 (ATE station). The diurnal variation of PM presented two peaks, one in the morning (from 0800 to 1000h) and the other at night (from 1900 to 2300h), with the highest concentrations of PM10 recorded at the ATE (0800h: 155.8μgm-3) and VMT (2100h: 154.6μgm-3) stations, and PM2.5 at the ATE station (0800h: 60.3μgm-3 and 2300h: 37.5μgm-3). The results showed that the contributions of PM10 are directly related to emissions from industrial activities, automotive fleet, construction, demolition, wind erosion, and the suspension and resuspension of particulates from unpaved roads. Meanwhile, high concentrations of PM2.5 are mainly attributed to vehicle exhaust emissions, industrial emissions, secondary particulate formation, and drag by the action of the winds. The major source of particulate matter contamination is the vehicle fleet, and within this, automobiles, station wagons, combi vans, and 2 and 3-wheel motorcycles are those that have the greatest contribution. These results were supported by non-parametric statistical tests such as Kruskal-Wallis and Mann-Whitney U and validated by the conditional bivariate probability function. The findings of this work may help to implement pollution prevention and control strategies in the future within this South American megacity.

Investigation of the Spatiotemporal Distribution of PM10, PM2.5, and PM1 from Motor Vehicles in Roadside Environments

This study examines the spatial and temporal distribution of PM10, PM2.5, and PM1 concentrations in Padang City, Indonesia, focusing on the impact of motor vehicle emissions. Measurements were conducted at distances ranging from 5 m to 100 m from major roadways and at different times of the day to evaluate the effects of traffic patterns and meteorological conditions on air quality. The findings revealed that Particulate Matter (PM) concentrations are significantly higher near roads, with PM10 peaking at over 55 μg/m³ in the afternoon at 5 m from the roadway. Similarly, PM2.5 and PM1 also reach the maximum levels of 45 μg/m³ and 35 μg/m³, respectively, during peak traffic hours. While meteorological factors, such as temperature, wind speed, relative humidity, and pressure, exhibit weak correlations with the PM levels, traffic volume emerges as the primary contributor to air pollution. These results underscore the need for effective traffic management and emission reduction strategies to mitigate pollution and protect public health. The current study’s recommendations include enhancing roadside air quality monitoring, and conducting further research on seasonal variations and the specific contributions of different vehicle types to PM pollution dynamics.

Efficient Purification of Auto-Exhaust Soot Particles Using Hexagonal Fe2O3 Nanosheets Decorated with Non-Noble Metals (Ni)

Purification of soot particles from automobile exhaust has closely to do with the synergistic effect between catalyst metals. Here, several binary Ni-Fe oxide catalysts were elaborately prepared via a modified solvothermal method. A non-noble-metal (Ni)-modified hexagonal Fe2O3 nano-sheet catalyst (Ni−Fe2O3) was prepared. The introduced heteroatoms replace some of the Fe atoms, which take up the surface of the [FeO6] octahedron, and the synergistic effect formed between the heteroatoms which are on the surface and the adjacent Fe atoms promotes the formation of coordination unsaturated ions of the activated reactants. The optimal performance was obtained with the Ni-Fe2O3-20 composition, with catalytic soot oxidation resulting in T50, SCO2m, Ea and TOF of 366 °C, 99.1%, 72.7 kJ mol−1 and 0.156 min−1 (at 310 °C), respectively. The combination of Ni and Fe2O3 cells increases the ratio of Fe3+/Fe2+, making the interaction among electrons between the Ni, which was proved highly dispersed over the catalyst, and the Fe2O3 strong. Both exist on the catalyst surface in the form of NiFe2O4. Ni atoms and Fe2O3, which demonstrate a synergistic effect, promoting the formation of coordination unsaturated ions of the activated reactants and generating more oxygen vacancies, thus promoting the adsorption of NO and accelerating the ignition of soot in O2 at a low temperature. The novel Ni-Fe2O3-X oxide cocatalyst is an improved noble-free catalyst that promotes the synergistic effect between heteroatoms and metal oxides through surface regulation. This is of great significance for the further development of economic and efficient catalysts for soot particle removal from automobile exhaust.

Pollution analysis of micro/nano meters glass particles and benzene produced from the friction cleaning process for the recovery of waste glass

Friction cleaning can effectively remove the paint coating (adhesive organic impurities) on the surface of waste glass, and promote the closed-loop recovery of urban silicic acid resources in industrial applications. However, due to a large number of mechanical collisions and wear during use, it is easy to produce powder dust and organic waste gas, and the pollution characteristics and mechanism have not been studied. In this study, the ball milling experiment was designed and the pollutants were tested and evaluated. The results show that a large number of micro/nano meters glass particles with an average size of less than 4.5μm are generated by low-speed ball milling, and the risk of inhalation is as high as 50.75mg/kg·m3. Main organic waste gases include cyclopropane, hexane, but-2-ene, and benzene with the value of Incremental lifetime cancer risk reaching 3.4×10-2 indicating definite carcinogenic risks for benzene exposure. The C-C bond between hydroxyl acrylic acid molecules and the C-O bond between phenolic propylene oxide molecules are easily broken to form small molecular chains, and the complex product is due to the complex cross-linking with the silane coupling agent. It is suggested that a special dust collector for micro/nano meters glass particles should be added while adopting an activated carbon catalytic combustion process to treat VOCs in the exhaust gas. This study revealed the contamination of micro/nano meters glass particles and benzene during friction cleaning to remove organic coatings in waste glass recycling.

Hazardous gas emissions from drop-in biofuels: mutagenicity, cytotoxicity, and unregulated pollutants

This study investigates cancer-related mutations (TA98 and YG5185 strains/Ames test), cell death (human A549 cell line/MTT assay) and unregulated pollutants (16 PAH, 13 carbonyls) from the gas exhaust emissions from a last-mile delivery vehicle following the WLTC driving cycle, operating with hydrotreated vegetable oil and biodiesel. Both biofuels were used pure and blended 20% by volume with diesel fuel. Gas phase samples were collected using XAD-2 Amberlite® resin. Total carbonyl emission factors for the different fuels ranged from 9.4±0.4 (HVO100) to 14.8±1.6mg/km (B20), while PAH emission factors ranged from 1.8±0.5 (B100) to 4.3±0.9mg/km (HVO20). The ester group in biodiesel demonstrated a significant impact on increasing carbonyl emissions. All fuels were cytotoxic at the highest concentration of exhaust gases, causing more than 30% cell death in human cell line A549 (HVO100≈ HVO20> B100≈ B20> ULSD). No significant correlation was found between cytotoxicity and most of PAH and carbonyls. A strong correlation between PAH and mutagenicity (Pearson correlation coefficient higher than 0.6 for PAH with 3 or more rings) was observed with strain YG5185, particularly when using the metabolic activator. These results indicate that the exhaust gases from the tested biofuels pose potential health risks, particularly in chronic exposure scenarios.

Exhaust gas after treatment using air preheating and selective catalytic reduction by urea to reduce NOx in diesel engine

Exhaust gas after treatment using air preheating and selective catalytic reduction by urea to reduce NOx in diesel engine

Performance of a 3DOM TiO2 Fog Seal Layer in Degrading NOx from Vehicle Exhaust

Performance of a 3DOM TiO2 Fog Seal Layer in Degrading NOx from Vehicle Exhaust

Comprehensive investigation of the effects on fuel, performance and emission properties of modify fuel blends addition of graphene nanoplatelets to ternary fuel blends (diesel, waste cooking biodiesel, and butanol) in a diesel engine

Comprehensive investigation of the effects on fuel, performance and emission properties of modify fuel blends addition of graphene nanoplatelets to ternary fuel blends (diesel, waste cooking biodiesel, and butanol) in a diesel engine

Structure optimization of a polygonal automobile exhaust thermoelectric generator considering in-vehicle compatibility

Structure optimization of a polygonal automobile exhaust thermoelectric generator considering in-vehicle compatibility

Applying quantitative structure-activity relationship (QSAR) models to extend the mixture toxicity prediction of scrubber water.

Marine organisms are constantly exposed to complex chemical mixtures from natural and anthropogenic sources. One source that has raised concerns is the discharge water from ships equipped with exhaust gas cleaning systems, commonly known as scrubbers. During operation, ships with scrubbers discharge large volumes of scrubber water, known to adversely affect marine organisms, into the environment. Scrubber water is highly acidic and contains a complex mixture of contaminants, including metals and polycyclic aromatic hydrocarbons (PAHs), at high concentrations. To assess the effect from these mixtures, critical values for individual mixture components can be determined from ecotoxicological studies and then compared to measured exposure concentrations. However, for several substances identified in scrubber water, for instance many alkylated PAHs, ecotoxicological studies are unavailable, preventing the determination of critical values. In this study, Quantitative Structure-Activity Relationship (QSAR) models have been used to amend and complement experimental data to estimate the mixture toxicity of scrubber water. Our results show that the combined predicted ecotoxicological response of an amended list of 50 substances measured in scrubber water from the substance groups metals (n=10), PAHs (n=16) and their alkylated derivatives (n=24), still underestimates the response observed in whole effluent toxicity tests. This suggests that there are additional substances and/or synergistic effects in the scrubber water mixtures that contribute to the overall toxicity. Thus, to accurately describe the toxicity of scrubber water, measurements and toxicity assessments must extend far beyond the usual suspects of 16 PAHs and a limited selection of metals. Here, QSAR models and advanced chemical screening-based methods are valuable tools for identifying substances of concern.

PI/SiO2@ZIF-8 nanofiber membrane with excellent high temperature exhaust gas filtration performance and efficiently formaldehyde adsorption capacity

PI/SiO2@ZIF-8 nanofiber membrane with excellent high temperature exhaust gas filtration performance and efficiently formaldehyde adsorption capacity

A comparative analysis of ozone disinfection mainstream processes in wastewater treatment plants: Exergy and exergoeconomic viewpoints

A comparative analysis of ozone disinfection mainstream processes in wastewater treatment plants: Exergy and exergoeconomic viewpoints

Synthesis of EPB/TiO2 Activated Carbon Composite Using Microwaves Activation for Purification of Motor Vehicle Exhaust Emissions

The palm oil plantation industry generates waste besides palm oil products, including empty palm bunch (EPB). This research examines the emission reduction capabilities of motor vehicle exhaust gases using a composite of activated carbon from EPB-AC/TiO2. Surface morphology characterization of the composite is conducted using Brunauer-Emmett-Teller (BET) and Scanning Electron Microscope (SEM). EPB-AC exhibits an average reduction effectiveness of HC gas based on particle size (50, 100, 150, 200 mesh) sequentially at 34.49%, 37.43%, 39.98%, and 43.56%. The average effectiveness of EPB-AC in reducing CO gas sequentially is 70.29%, 71.30%, 72.86%, and 74%. For CO2 gas, EPB-AC has an average reduction sequentially at 52.6%, 54.25%, 56.52%, and 58.54%. On the other hand, the EPB-AC/TiO2 composite exhibits an average reduction effectiveness of HC gas based on particle size sequentially at 42.38%, 43.42%, 45.1%, and 46.57%. The average effectiveness of the EPB-AC/TiO2 composite in reducing CO gas sequentially is 71.24%, 73.52%, 75.54%, and 76.9%. For CO2 gas, the EPB-AC/TiO2 composite has an average reduction sequentially at 54.93%, 54.25%, 59.76%, and 63.05%. Therefore, the best reduction results occur at a particle size of 200 mesh.

A comprehensive investigation of EGR (exhaust gas recirculation) effects on energy distribution and emissions of a turbo-charging diesel engine under World Harmonized transient cycle

A comprehensive investigation of EGR (exhaust gas recirculation) effects on energy distribution and emissions of a turbo-charging diesel engine under World Harmonized transient cycle