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Traffic Related Emission (2nd Edition)

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A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Pollution Control".

Deadline for manuscript submissions: closed (30 May 2024) | Viewed by 14419

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Special Issue Editor

Dr. Xin Wang

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Guest Editor

School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
Interests: exhaust and brake emission measurement and control; particularly particles; non regulated pollutants; combustion and emission characteristics of alternative fuels
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Special Issue Information

Dear Colleagues,

This Special Issue is a follow-up of the first Special Issue entitled “Traffic-Related Emission” (https://www.mdpi.com/journal/atmosphere/special_issues/Traffic_Related_Emission) published in Atmosphere and will cover all aspects of traffic-related emission.

Globally, traffic-related emissions are critical in contributing to local air pollution issues. The increasing applications of cleaner fuels (including alternative fuels and traditional fuels meeting stricter standards) and emission control devices have largely alleviated the problem of traffic-related emissions. However, new challenges emerge, such as new toxic pollutants (ammonia, aldehydes, smaller exhaust particles, intermediate- and semi-VOCs), concerns over secondary contamination via atmospheric reactions, and life-cycle emission reduction capabilities. All these issues establish the necessity to continue engine emissions research, legislation, and policy assessment in this 'electrified' era.

The non-road sector is another source of air pollution but has been underestimated or unintendedly overlooked. Along with reducing on-road engine emissions, the impacts of non-road mobile machinery (NRMM) are attracting increasing focus. Especially with the outbreaks of several international incidents in the past few years, recent changes in marine emissions may significantly impact both global and coastal inventories.

In addition to engine emissions, non-exhaust emissions, primarily brake and tire particles from motor vehicles and rails, have been included or considered in the forthcoming regulations in Europe and China. Their control's priority may grow with the increase in gross vehicle weight and urban traffic congestion.

The scope of the second volume of this Special Issue will be consistent with the previous one, including all types of research on traffic-related emissions from motor vehicles, NRMMs, and non-exhaust sources (brake and tire wear particles as well as evaporative VOCs). In addition, new insights into the impacts of future vehicle technologies, including but not confined to electrification, hybridization, and e-fuels, on local air quality improvement and carbon footprint reduction are welcomed. Original research reporting cutting-edge technologies in emission control and fuel, life-cycle assessment of the carbon footprint, and forthcoming emission regulations with experimental data support are highly appreciated.

Dr. Xin Wang
Guest Editor

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Keywords

traffic-related emission
alternative fuel
internal combustion engine
motor vehicle
non-road mobile machinery (NRMM)
non-exhaust particles
life-cycle assessment

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Published Papers (9 papers)

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Research

13 pages, 2997 KiB

Open AccessEditor’s ChoiceArticle

Evaluating Real Driving Emissions of Compressed Natural Gas Taxis in Chongqing, China—A Typical Mountain Cities

by Wei Hu, Linfeng Duan, Min Tang, Rui Yuan, Gaiyan Lv, Pingjiang Lv, Zhenliang Li, Ling Li, Hualong Xu, Jiajia Ding and Dan Zhang

Atmosphere 2024, 15(6), 715; https://doi.org/10.3390/atmos15060715 - 14 Jun 2024

Viewed by 829

Abstract

Compressed natural gas (CNG) taxis represent the most ubiquitous and dynamically active passenger vehicles in urban settings. The pollutant emission characteristics of in-use CNG taxis driving on a typical mountain city before and after three-way catalyst (TWC) replacement was examined using a modular on-board portable emissions measurement system (PEMS), the OBS-ONE developed by Horiba. The results showed that the exhaust NO of CNG taxis equipped with deactivation TWC exceeded the emission limits, even higher than gasoline vehicles. The high emission rate of CNG taxis is mainly concentrated on road slopes between a 2% and 6% gradient and a deceleration rate in the interval of [0.5, 4], respectively, which results in higher emissions from CNG taxis traveling in the mountain city of Chongqing than other cities and vehicles. Moreover, the pollutant emission rates of the in-use CNG taxis were highly correlated with the velocity and the vehicle specific power (VSP). After a new TWC replacement, the emission factors of carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NOx), and particle number (PN) decreased by 85.21–89.11%, 68.71–85.49%, 60.91–81.11%, and 62.26–68.39%, respectively. Our results will provide guidance for urban environments to carry out the comprehensive management of in-use vehicles and emphasize the importance of TWC replacement for CNG taxis. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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17 pages, 2451 KiB

Open AccessArticle

Analysis of Particle Number Emissions in a Retrofitted Heavy-Duty Spark Ignition Engine Powered by LPG

by Vicente Bermúdez, Pedro Piqueras, Enrique José Sanchis and Brayan Conde

Atmosphere 2024, 15(6), 704; https://doi.org/10.3390/atmos15060704 - 12 Jun 2024

Viewed by 562

Abstract

This study aims to examine the particle number (PN) emissions of a retrofitted heavy-duty spark ignition (HD-SI) engine powered by liquefied petroleum gas (LPG) under both steady-state and transient conditions. The engine was tested under seven steady-state operating points to investigate the PN behavior and particle size distribution (PSD) upstream and downstream of the three-way catalyst (TWC). This analysis intends to assess the impact of including particles with diameters ranging from 10 nm to 23 nm on the total particle count, a consideration for future regulations. The study employed the World Harmonized Transient Cycle (WHTC) for transient conditions to encompass the same engine working region as is used in the steady-state analysis. A Dekati FPS-4000 diluted the exhaust sample to measure the PSD and PN for particle diameters between 5.6 nm and 560 nm using the TSI-Engine Exhaust Particle Sizer (EEPS) 3090. The findings indicate that PN levels tend to increase downstream of the TWC under steady-state conditions in operating points with low exhaust gas temperatures and flows (equal to or less than 500 °C and 120 kg/h). Furthermore, the inclusion of particles with diameters between 10 nm and 23 nm leads to an increase in PN emissions by 17.70% to 40.84% under steady conditions and by an average of 40.06% under transient conditions, compared to measurements that only consider particles larger than 23 nm. Notably, in transient conditions, most PN emissions occur during the final 600 s of the cycle, linked to the most intense phase of the WHTC. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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19 pages, 1666 KiB

Open AccessArticle

Influence of Vertical Load, Inflation Pressure, and Driving Speed on the Emission of Tire–Road Particulate Matter and Its Size Distribution

by Stefan Schläfle, Meng Zhang, Hans-Joachim Unrau and Frank Gauterin

Atmosphere 2024, 15(4), 502; https://doi.org/10.3390/atmos15040502 - 19 Apr 2024

Cited by 1 | Viewed by 1509

Abstract

As fleet electrification progresses, vehicles are continuously becoming heavier, while the used electric motors, with their high torques, enable longitudinal dynamics to be maintained or even increased. This raises the question of what effect electric vehicles have on the emission of tire–road particulate matter (PM). To answer this question, investigations were carried out in this study on a tire internal drum test bench with real road surfaces. In addition to the vertical load, the tire inflation pressure and the driving speed were varied. PM emissions were recorded in real time, resulting in emission factors (emission per kilometer driven) for different load conditions. This allows statements to be made about both the effect on the total emission and on the particle size distribution. It was shown that the PM emission increases linearly with the vertical load at constant longitudinal dynamics. If the tire inflation pressure is increased, the emission also increases linearly, and the increases in emission are equally large for both influences. A clear influence of the driving speed on the emission factor could not be determined. With regard to the particle size distribution, the following correlations were found: higher vertical load and higher tire inflation pressure result in a larger mean particle diameter, while a higher driving speed reduces it. Thus, this study contributes to a better understanding of the expected changes in tire-road PM emissions as a result of electrification. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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13 pages, 2520 KiB

Open AccessArticle

Characteristics of Vehicle Tire and Road Wear Particles’ Size Distribution and Influencing Factors Examined via Laboratory Test

by Chongzhi Zhong, Jiaxing Sun, Jing Zhang, Zishu Liu, Tiange Fang, Xiaoyu Liang, Jiawei Yin, Jianfei Peng, Lin Wu, Qijun Zhang and Hongjun Mao

Atmosphere 2024, 15(4), 423; https://doi.org/10.3390/atmos15040423 - 29 Mar 2024

Cited by 1 | Viewed by 2049

Abstract

With the implementation of strict emission regulations and the use of cleaner fuels, there has been a considerable reduction in exhaust emissions. However, the relative contribution of tire wear particles (TWPs) to particulate matters is expected to gradually increase. This study conducted laboratory wear experiments on tires equipped on domestically popular vehicle models, testing the factors and particle size distribution of TWPs. The results showed that the content of tire wear particle emission was mainly ultrafine particles, accounting for 94.80% of particles ranging from 6 nm to 10 μm. There were at least two concentration peaks for each test condition and sample, at 10~13 nm and 23~41 nm, respectively. The mass of TWP emission was mainly composed of fine particles and coarse particles, with concentration peaks at 0.5 μm and 1.3–2.5 μm, respectively. Both the number and mass of TWPs exhibited a bimodal distribution, with significant differences in emission intensity among different tire samples. However, there was a good exponential relationship between PM₁₀ mass emissions from tire wear and tire camber angle. The orthogonal experimental results showed that the slip angle showed the greatest impact on TWP emission, followed by speed and load, with the smallest impact from inclination angle. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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19 pages, 3782 KiB

Open AccessArticle

Study on the Emission Characteristics of Typical City Buses under Actual Road Conditions

by Jiguang Wang, Feng Xu, Xudong Chen, Jiaqiang Li, Li Wang, Bigang Jiang and Yanlin Chen

Atmosphere 2024, 15(2), 148; https://doi.org/10.3390/atmos15020148 - 24 Jan 2024

Viewed by 1334

Abstract

Five typical in-use city buses in Tangshan with different emission standards, fuel power types, and emission control technology routes were selected as the research objects. PEMSs (Portable Emissions Measurement Systems) and OBD (On-Board Diagnostic) remote monitoring technologies were used to conduct research on actual road conditions and emission characteristics. The research aimed to analyze the driving characteristics of different power types of bus engines and after-treatment systems, as well as their impact on emissions. The results indicated that the actual road driving is mainly in the urban and suburban areas of the local region. Additionally, the VSP (Vehicle Specific Power) was found to be distributed in the low- and medium-speed range of mode Bin0~Bin24. The emission rates of each pollutant showed an increasing trend with the increase in VSP. THC and NOx emissions of CNG and LNG buses are significantly higher than those of gas–electric hybrid buses. However, the PM emissions are lower. Therefore, it is necessary to strengthen the NOx emission control of CNG and LNG buses. With the improvement in emission standards and the use of hybrid technology, CO₂ and NOx emissions of China IV buses can be reduced by 13% and 53.5% compared with China III buses of the same tonnage. The CO₂ and NOx emissions of China V buses using natural gas combustion and an electric mixture are 20% and 18.8% lower than those of China V buses of the same tonnage using only natural gas. In the actual operation of the diesel–electric hybrid bus equipped with the SCR (Selective Catalytic Reduction) system, the working time of the engine is about 35.5 ± 5%, and the working time of the SCR system only accounts for 65.5 ± 12%. The low working conditions of the SCR system and the low temperature of SCR system are the reasons for the high NOx concentration at the rear end of the SCR system when the hybrid electric bus is running at low speeds. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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26 pages, 9431 KiB

Open AccessArticle

Quantitative Analysis of the Impacts of Ash from Lubricating Oil on the Nanostructure of Diesel Particulate Matter

by Legang Wu, Jia Yang, Haohao Wang, Dongxia Yang, Yunshan Ge and Ping Ning

Atmosphere 2024, 15(1), 130; https://doi.org/10.3390/atmos15010130 - 20 Jan 2024

Viewed by 1303

Abstract

Microscopic analyses of the effects of ash on particulate matter oxidation are rather scarce. In this study, three different lubricating oils with varying ash contents were used to investigate their effects on the nanostructure of diesel particulate matter. The nanostructure and nanostructure parameters, including fringe length, fringe separation distance, and fringe tortuosity, were studied using high-resolution transmission electron microscopy. The results show that all samples obtained from blending with different lubricant oil present typical core–shell structures. The inner cores remain relatively unchanged, whereas the thickness of the outer shells increases with the increasing ash content in the lubricant oil under the same working conditions. The fringe length increases and the fringe separation distance decreases with the rising ash content in the lubricant oil operating in the same working conditions. The fringe tortuosity decreases when the ash content in the lubricant oil increases from 0.92% to 1.21%, but shows little change when the ash content in the lubricant oil increases from 1.21% to 1.92%. Based on the effects of ash on the nanostructure parameters, it can be inferred that the oxidation activity of particles decreases with increasing ash content in the lubricant oil. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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21 pages, 7748 KiB

Open AccessArticle

Characteristics of Suspended Road Dust According to Vehicle Driving Patterns in an Urban Area and PM₁₀ Content in Silt

by Hojun Yoo, Jeongyeon Cho, Sungjin Hong and Intai Kim

Atmosphere 2024, 15(1), 5; https://doi.org/10.3390/atmos15010005 - 20 Dec 2023

Viewed by 1682

Abstract

Characterizing the influence factors of exhaust gas based on the suspended road dust on paved roads, according to the number of vehicles and their distance with regard to driving pattern, is important in order to provide a coefficient for driving patterns to find a model equation. This has been a limitation of previous studies, in which this was difficult to carry out in a large area reflecting various driving patterns because some sections were selected according to empirical measurement results, and only one vehicle measurement was used to find the level of road dust. This study measured the concentration of suspended road dust that could occur, depending on the vehicle’s driving patterns, on an experimental road in Yongin, South Korea, from May to July 2023. The study was conducted to determine the degree of the effect of exhaust gas, according to the concentration of suspended road dust generated, by determining the separation distance based on real-time measurements. This study attempted to determine the changes in suspended road dust based on driving patterns in urban areas and factor in the concentration of suspended road dust with regard to emission characteristics in terms of exhaust gas and particulate matter with a diameter of 10 microns or less (PM₁₀). This was in accordance with conditions evaluated using mobile laboratories, based on suspended-PM₁₀-concentration-measuring equipment. This study mainly focused on the following main topics: (1) increasing the level of suspended particulate matter at less than 10 m intervals produced by exhaust gas; (2) decreasing the level of suspended road dust with an increase in the number of vehicles, with the area measured at a distance of three cars in front showing the lowest level of suspended road dust in the air and a low level for the rear vehicle; (3) demonstrating that PM₁₀ is effective in measuring the generation of suspended road dust; and (4) evaluating suspended road dust levels by road section. Based on the results, this research is necessary to more appropriately set the focus of analyses that aim to characterize suspended road dust according to exhaust gas and PM₁₀ content in silt. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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14 pages, 24946 KiB

Open AccessEditor’s ChoiceArticle

Research on Carbon Emission Characteristics and Mitigation Pathways in the Vehicle Fuel Cycle: A Case Study of Guangdong Province

by Jianjun Liu, Yinping Luo, Qianru Zhu, Yixi Li and Yutao Luo

Atmosphere 2024, 15(1), 3; https://doi.org/10.3390/atmos15010003 - 20 Dec 2023

Cited by 1 | Viewed by 1334

Abstract

This study presents a comprehensive analysis of vehicle ownership, energy consumption, and carbon emissions in Guangdong Province, China, from 2020 to 2035 under different scenarios. Key findings highlight the province’s pursuit of carbon peak goals and provide valuable insights into strategies to achieve them. Vehicle ownership in Guangdong is projected to exceed 48 million by 2035, which represents a doubling from 2020. Under both scenarios, internal combustion engine vehicle ownership will peak around 2030 and then gradually decline, while under the enhanced scenario, electric vehicle ownership will exceed 40% by 2035. Enhanced vehicle energy efficiency and reduced annual mileage will lead to a 17% reduction in gasoline and diesel consumption by 2035 in both scenarios. At the same time, there will be a substantial five- to six-fold increase in electricity consumption for vehicles compared to 2020. Both scenarios peak in carbon emissions before 2030, with the enhanced scenario achieving this peak a year earlier. The enhanced scenario outperforms the baseline, reducing carbon emissions by about 21.2% from the peak and 8% relative to 2020. Pure electric vehicles exhibit a significant advantage in reducing carbon emissions per vehicle compared to their internal combustion engine counterparts. Encouraging new energy vehicles, especially pure electric ones, accelerates the carbon emissions peak and lowers overall peak emissions. Accelerating the adoption of electric vehicles, reducing per-vehicle fuel consumption and annual average mileage, and optimizing transportation modes are crucial for carbon peaking from the vehicle fuel cycle. Policy recommendations focus on promoting new energy vehicles, optimizing transportation, and advancing research and technology. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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15 pages, 2368 KiB

Open AccessArticle

Assessment of Heavy-Duty Diesel Vehicle NOx and CO₂ Emissions Based on OBD Data

by Lijun Hao, Yanxu Ren, Wenhui Lu, Nan Jiang, Yunshan Ge and Yachao Wang

Atmosphere 2023, 14(9), 1417; https://doi.org/10.3390/atmos14091417 - 8 Sep 2023

Cited by 8 | Viewed by 2508

Abstract

Controlling NOx and CO₂ emissions from heavy-duty diesel vehicles (HDDVs) is receiving increasing attention. Accurate measurement of HDDV NOx and CO₂ emissions is the prerequisite for HDDV emission control. Vehicle emission regulations srecommend the measurement of NOx and CO₂ emissions from vehicles using an emission analyzer, which is expensive and unsuitable to measure a large number of vehicles in a short time. The on-board diagnostics (OBD) data stream of HDDVs provides great convenience for calculating vehicle NOx and CO₂ emissions by providing the engine fuel flow rate, NOx sensor output, and air mass flow. The calculated vehicle NOx and CO₂ emissions based on the OBD data were validated by testing a heavy-duty truck’s emissions on the chassis dynamometer over the CHTC-HT driving cycle, showing that the calculated NOx and CO₂ emissions based on the OBD data are consistent with the measured results by the emission analyzer. The calculated vehicle fuel consumptions based on the OBD data were close to the calculated results based on the carbon balance method and the measured results by the fuel flowmeter. The experimental results show that accessing vehicle NOx and CO₂ emissions based on the OBD data is a convenient and applicable method. Full article

(This article belongs to the Special Issue Traffic Related Emission (2nd Edition))

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