Search Results (308)

The maritime sector is undergoing rapid transformation, driven by increasingly stringent international regulations targeting air pollution. While newly built vessels integrate advanced technologies for compliance, the global fleet averages 21.8 years of age and must meet emission requirements through retrofitting or operational changes. This study evaluates, at environmental and economic levels, two key sulphur abatement strategies for a 1998-built cruise vessel nearing the end of its service life: (i) the installation of open-loop scrubbers with fuel enhancement devices, and (ii) a switch to marine diesel oil as main fuel. The analysis was based on real operational data from a cruise vessel. For the environmental assessment, a Tier III hybrid emissions model was used. The results show that scrubbers reduce SO_x emissions by approximately 97% but increase fuel consumption by 3.6%, raising both CO₂ and NO_x emissions, while particulate matter decreases by only 6.7%. In contrast, switching to MDO achieves over 99% SO_x reduction, an 89% drop in particulate matter, and a nearly 5% reduction in CO₂ emissions. At an economic level, it was found that, despite a CAPEX of nearly USD 1.9 million, scrubber installation provides an average annual net saving exceeding USD 8.2 million. From the deterministic and probabilistic analyses performed, including Monte Carlo simulations under various fuel price correlation scenarios, scrubber installation consistently shows high profitability, with NPVs surpassing USD 70 million and payback periods under four months. Full article

Compression–ignition engines emit particulate matter (PM) (soot), prompting the widespread use of diesel particulate filters (DPFs) in the automotive sector. An alternative method for PM reduction involves the use of ultrasonic waves to disperse and modify the structure of exhaust particles. This article presents experimental results of the effects of ultrasonic emitter parameters, including the number, arrangement, and power, along with the engine speed, on the exhaust smoke density. Tests were conducted on a laboratory prototype equipped with six ultrasonic emitters spaced 0.17 m apart. The exhaust source was a diesel engine from a construction excavator, based on the MTZ-80 tractor design, delivering 80 HP and a displacement of 4750 cm³. A regression model was developed to describe the relationship between the engine speed, emitter power and spacing, and smoke density. The optimal configuration was found to involve an emitter power of 319.35 W and a spacing of 1.361 m for a given engine speed. Under the most effective conditions—an engine speed of 1500 rpm, six active emitters, and a total power of 600 W—smoke emissions were reduced by 18%. These findings support the feasibility of using ultrasonic methods as complementary or alternative exhaust gas filtration techniques for non-road diesel engines. Full article

Selective catalytic reduction filter (SDPF) technology constitutes a critical methodology for controlling nitrogen oxide (NOx) and particulate matter emissions from light-duty diesel vehicles. A series of SDPFs with different sulfur poisoning times and concentrations were prepared using the worldwide harmonized light vehicles test cycle (WLTC). Bench testing revealed that sulfur poisoning diminished the catalyst’s NH₃ storage capacity, impaired the transient NOx reduction efficiency, and induced premature ammonia leakage. After multiple sulfur poisoning incidents, the NOx reduction performance stabilized. Higher SO₂ concentrations accelerated catalyst deactivation and hastened the attainment of this equilibrium state. The characterization results for the catalyst indicate that the catalyst accumulated the same sulfur content after tail gas poisoning with different sulfur concentrations and that sulfur existed in the form of SO₄²⁻. The sulfur species in low-sulfur-poisoning-concentration catalysts mainly included sulfur ammonia and sulfur copper species, while high-sulfur-poisoning-concentration catalysts contained a higher proportion of sulfur copper species. Neither species type significantly altered the zeolite coating’s crystalline structure. Sulfur ammonia species could easily lead to a significant decrease in the specific surface area of the catalyst, which could be decomposed at 500 °C to achieve NOx reduction performance regeneration. In contrast, sulfur copper species required higher decomposition temperatures (600 °C), achieving only partial regeneration. Full article

The presented research examined the impact of using biodiesel as a fuel for existing diesel engines during the transition to the broader adoption of electric vehicles powered by renewable energy or through integrated hybrid drive systems. The authors considered previous research on this topic, which is demonstrated by a literature review. This paper will utilize the findings to further explore the potential of optimizing existing engines by using biodiesel and thus propose their continued use in the transition period as one of the clean fuels. This paper outlines the standards that define fuel quality and presents a test bench equipped with an experimental engine and specialized equipment for laboratory examination, enabling the measurement of emissions and the determination of cylinder pressure. To ensure the repeatability of the experimental conditions and facilitate future comparison of the obtained results, the engine examination was conducted according to the standard ESC 13-mode test. The examination process confirmed a significant reduction in particulate matter emissions (on average 40%) but, simultaneously, an increase in nitrogen oxide emissions (on average 25%), whose level, according to data from the literature, depends on the type of raw materials used for biodiesel production. Brake thermal efficiency is higher when operating with biodiesel (on average 1.5%). Still, it was concluded that the use of biodiesel in existing diesel engines is feasible only if the engines are equipped with variable systems for automatically adjusting the compression ratio, fuel injection time, valve timing, and so on. The outcomes from the examination conducted can be further processed by applying statistical methods and represent an essential database for further research in this scientific area. Full article

The global climate crisis necessitates the urgent implementation of sustainable practices and carbon emission reduction strategies across all sectors. Transport, as a major contributor to greenhouse gas emissions, requires transitional technologies to bridge the gap between fossil fuel dependency and renewable energy systems. Natural gas, recognised as the cleanest fossil-derived fuel with approximately half the CO₂ emissions of coal and 75% of oil, presents a potential transitional solution through Natural Gas Vehicles (NGVs). This manuscript presents several distinctive contributions that advance the understanding of Natural Gas Vehicles within the contemporary energy transition landscape while synthesising updated emission performance data. Specifically, the feasibility and sustainability of NGVs are investigated within the energy transition framework by systematically incorporating recent technological developments and environmental, economic, and infrastructure considerations in comparison to conventional vehicles (diesel and petrol) and unconventional alternatives (electric and hydrogen-fuelled). The analysis reveals that NGVs can reduce CO₂ emissions by approximately 25% compared to petrol vehicles on a well-to-wheel basis, with significant reductions in NO_x and particulate matter. However, these environmental benefits depend heavily on the source and type of natural gas used (CNG or LNG), while economic viability hinges largely on governmental policies and infrastructure development. The findings suggest that NGVs can serve as an effective transitional technology in the transport sector’s sustainability pathway, particularly in regions with established natural gas infrastructure, but require supportive policy frameworks to overcome implementation barriers. Full article

Diesel particulate matter—primarily ultrafine particles (UFPs), defined as particles smaller than 0.1 µm—are released by diesel-powered vehicles, especially those used in heavy-duty hauling. While much of the existing research on traffic-related air pollution focuses on urban environments, limited attention has been paid to how complex topography influences the concentration of UFPs, particularly in areas with significant truck traffic. With a focus on Morgantown, West Virginia, an area distinguished by a steep topography, this study investigates how travel over two different terrain conditions affects UFP concentrations close to roadways. Specifically, we sought to determine if the truck count taken from simultaneous video evidence could be used as a surrogate for varying topography in determining the concentration of UFPs. This study shows that “TRUCK COUNT” and “TRUCK SPEED” have a linear relationship and yield a possible surrogate measure of the lung dose of UFP number concentration. Our results demonstrate a statistically significant (p < 0.1) linear relationship between truck count and UFP number concentration (R = 0.77 and 0.40), validating truck count along with truck speed as a medium effect surrogate for estimating near-road UFP exposure. Dose estimation using the Multiple-Path Particle Dosimetry (MPPD) model further revealed that approximately 30% of inhaled UFPs are deposited in the alveolar region, underscoring the public health relevance of this exposure pathway in topographically complex areas. This method ultimately awaits comparison with health effects to determine its true potential as a useful exposure metric. Full article

This study investigates the relationships between air quality, social vulnerability, and health outcomes at the census tract-level in Harris County, Texas. Spatial and regression analyses were conducted using sociodemographic data, air quality indicators, including PM2.5, diesel particulate matter (DPM), nitrogen dioxide (NO₂), and ozone, and health metrics, such as coronary heart disease, chronic obstructive pulmonary disease (COPD), asthma, and stroke prevalence. The results indicated variability in sociodemographic challenges, air pollution, and health outcomes. Social vulnerability strongly correlated with increased prevalence of respiratory and cardiovascular diseases, notably COPD, asthma, and stroke. The air quality metrics showed significant geospatial variability: PM2.5 and NO₂ were concentrated centrally near transportation corridors, DPM was elevated near eastern industrial regions, and ozone peaked in western parts of the county, potentially due to atmospheric transport and photochemical processes. PM2.5 exposure significantly correlated with increased cardiovascular and respiratory health outcomes, particularly at elevated concentrations. In contrast, ozone demonstrated a plateauing effect, increasing the health risks but with a diminishing impact at higher concentrations. The correlations between social vulnerability and air quality were modest, suggesting homogenous distributions of PM2.5, NO₂, and DPM across socioeconomically diverse areas, whereas ozone exposure slightly increased with higher social vulnerability. The findings pointed to the complexity of spatial relationships between socioeconomic status, air pollution, and health, highlighting the need for additional monitoring and targeted interventions to improve health outcomes in socio-demographically and economically challenged communities. Full article

Although the transition to electric vehicles (EVs) is well underway and expected to continue in global car markets, most vehicles on the world’s roads will be powered by internal combustion engine vehicles (ICEVs) and fossil fuels for the foreseeable future, possibly well past 2050. Thus, good environmental performance and effective emission control of ICE vehicles will continue to be of paramount importance if the world is to achieve the stated air and climate pollution reduction goals. In this study, we review 228 publications and identify four main issues confronting these objectives: (1) cheating by vehicle manufacturers, (2) tampering by vehicle owners, (3) malfunctioning emission control systems, and (4) inadequate in-service emission programs. With progressively more stringent vehicle emission and fuel quality standards being implemented in all major markets, engine designs and emission control systems have become increasingly complex and sophisticated, creating opportunities for cheating and tampering. This is not a new phenomenon, with the first cases reported in the 1970s and continuing to happen today. Cheating appears not to be restricted to specific manufacturers or vehicle types. Suspicious real-world emissions behavior suggests that the use of defeat devices may be widespread. Defeat devices are primarily a concern with diesel vehicles, where emission control deactivation in real-world driving can lower manufacturing costs, improve fuel economy, reduce engine noise, improve vehicle performance, and extend refill intervals for diesel exhaust fluid, if present. Despite the financial penalties, undesired global attention, damage to brand reputation, a temporary drop in sales and stock value, and forced recalls, cheating may continue. Private vehicle owners resort to tampering to (1) improve performance and fuel efficiency; (2) avoid operating costs, including repairs; (3) increase the resale value of the vehicle (i.e., odometer tampering); or (4) simply to rebel against established norms. Tampering and cheating in the commercial freight sector also mean undercutting law-abiding operators, gaining unfair economic advantage, and posing excess harm to the environment and public health. At the individual vehicle level, the impacts of cheating, tampering, or malfunctioning emission control systems can be substantial. The removal or deactivation of emission control systems increases emissions—for instance, typically 70% (NO_x and EGR), a factor of 3 or more (NO_x and SCR), and a factor of 25–100 (PM and DPF). Our analysis shows significant uncertainty and (geographic) variability regarding the occurrence of cheating and tampering by vehicle owners. The available evidence suggests that fleet-wide impacts of cheating and tampering on emissions are undeniable, substantial, and cannot be ignored. The presence of a relatively small fraction of high-emitters, due to either cheating, tampering, or malfunctioning, causes excess pollution that must be tackled by environmental authorities around the world, in particular in emerging economies, where millions of used ICE vehicles from the US and EU end up. Modernized in-service emission programs designed to efficiently identify and fix large faults are needed to ensure that the benefits of modern vehicle technologies are not lost. Effective programs should address malfunctions, engine problems, incorrect repairs, a lack of servicing and maintenance, poorly retrofitted fuel and emission control systems, the use of improper or low-quality fuels and tampering. Periodic Test and Repair (PTR) is a common in-service program. We estimate that PTR generally reduces emissions by 11% (8–14%), 11% (7–15%), and 4% (−1–10%) for carbon monoxide (CO), hydrocarbons (HC), and oxides of nitrogen (NO_x), respectively. This is based on the grand mean effect and the associated 95% confidence interval. PTR effectiveness could be significantly higher, but we find that it critically depends on various design factors, including (1) comprehensive fleet coverage, (2) a suitable test procedure, (3) compliance and enforcement, (4) proper technician training, (5) quality control and quality assurance, (6) periodic program evaluation, and (7) minimization of waivers and exemptions. Now that both particulate matter (PM, i.e., DPF) and NO_x (i.e., SCR) emission controls are common in all modern new diesel vehicles, and commonly the focus of cheating and tampering, robust measurement approaches for assessing in-use emissions performance are urgently needed to modernize PTR programs. To increase (cost) effectiveness, a modern approach could include screening methods, such as remote sensing and plume chasing. We conclude this study with recommendations and suggestions for future improvements and research, listing a range of potential solutions for the issues identified in new and in-service vehicles. Full article

The deposition and dispersion of particulate matter from diesel combustion in confined spaces pose significant challenges to air quality and public health, with important implications for sustainable development goals. While previous studies have focused on particle behavior inside diesel engines, the external environmental effects remain poorly understood. This study systematically investigated the mass concentrations and deposition characteristics of PM₁, PM_2.5, and PM₁₀ particles in a 1 m³ environmental chamber under both sealed and ventilated conditions. The experimental results demonstrated that natural deposition ratios reached 50–75% after 8 h across all particle sizes. A comparative evaluation of ventilation strategies showed lateral ventilation achieved superior particle reduction ratios of 36%, outperforming direct ventilation at 14–22% and non-ventilated conditions at 23%. The study revealed that ventilation-induced convective removal was more effective than gravitational settling alone, providing important technical insights for air quality management in enclosed environments. These findings offer valuable scientific guidance for optimizing ventilation systems while contributing to the development of sustainable solutions for particulate pollution control. The research advances our understanding of particle behavior in confined spaces and supports technological innovations for cleaner air in urban infrastructure. Full article

In this study, the chemical compositions of PM_2.5 (particulate matter < 2.5 μm) and the molecular compositions of methanol-soluble organic carbon (MSOC) in suburban Shanghai during summer were measured to investigate the molecular characteristics of organic aerosol (OA) under high humidity. Diurnal variation analysis reveals the influence of relative humidity (RH) on secondary organic aerosol (SOA) components. Organosulfates (OSs), particularly nitrooxy-OSs, exhibit a positive correlation with increasing humidity rather than atmospheric oxidants in this high-humidity site. This suggests that high RH can promote the formation of OSs, possibly through enhancing particle surface area and volume, and creating a favorable environment for aqueous-phase or heterogeneous reactions in the particle phase. A considerable proportion of CHOS compounds may be derived from anthropogenic aliphatic hydrocarbon derivatives. These compounds exhibit slightly elevated daytime concentrations due to increased emissions of long-chain aliphatics from sources such as diesel combustion, as well as photochemically enhanced oxidation to OSs. In contrast, CHONS compounds increased at night, driven by high-humidity liquid-phase oxidation. Terpenoid derivatives accounted for 13.4% of MSOC and contributed over 40% to nighttime CHONS. These findings highlight humidity’s important role in driving daytime and nighttime processing of anthropogenic and biogenic precursors to form SOA, even under low SO₂ and NO_x conditions. Full article

Diesel exhaust particulate (DEP) is widely recognized to weaken lung function and skin diseases. When the skin, which defends against external factors, is exposed to PM2.5, various chronic inflammatory diseases occur. When keratinocytes recognize harmful signals, they synthesize the NOD-like receptor protein 1 (NLRP1) inflammasome. DEP enhances NF-κB signaling and NLRP1 inflammasome expression through the interaction of TXNIP with NLRP1 in keratinocytes. Although many studies have reported the anti-inflammatory and antioxidant characteristics of Impressic acid (IPA), the umbrella consequences of IPA for PM2.5-influenced inflammasomes and the associated mechanisms remain unknown. Therefore, this study aimed to examine the protective function of IPA against inflammation in human keratinocytes. IPA attenuated the NLRP1 expression, caspase-1, IL-1β actuation, and NF-κB and IκB phosphorylation induction by DEP. IPA upregulated the Nrf2, HO-1, and NQO1 expression through CaMKKβ, AMPK, and GSK3β phosphorylation. Also, IPA led to the elevation of p62 and the degradation of the Keap1 protein. ML385 reversed the suppressive effect of IPA on the NLRP1 inflammasome, which was enhanced by DEP, and NAC counteracted the effect of ML385. These findings indicate that IPA can suppress inflammation induced by PM2.5 by expressing antioxidant enzymes through the Keap1/p62/Nrf2-signaling pathway in human keratinocytes. Full article

The abundant availability of crop waste and forestry residues in Texas provides great potential for producing renewable diesel in the local towns of Texas. This study aims to evaluate the environmental impacts of renewable diesel use in Texas transportation and the potential of renewable diesel production in Texas. The GREET model was used to customize the life cycle pathway of renewable diesel and evaluate its environmental impacts. The models of renewable diesel produced from forestry residue and corn stover were built to calculate life cycle gas emissions of combination short-haul heavy-duty trucks fueled with renewable diesel. Life cycle GHG emissions of renewable diesel are much lower than those of low-sulfur diesel. However, with respect to renewable diesel derived from corn stover, life cycle PM₁₀ and PM_2.5 emissions were almost double those of low-sulfur diesel in 2024, and both emissions will be reduced by 37–38% in 2035. The life cycle emission trends of SO_x, black carbon, and primary organic carbon are very similar to those of PM₁₀ and PM_2.5. The total cost of ownership (TCO) of heavy-duty trucks using renewable diesel produced from forestry residues or corn stover would be 10.3–14.8% higher than those consuming regular low-sulfur diesel in Texas. Full article

The aim of this study was to assess the impact of adding ethanol to diesel fuel on particulate matter (PM) and nitrogen oxides (NOx) emissions in the Perkins 854E compression-ignition engine. Tests were carried out under European Stationary Cycle (ESC) conditions using the Horiba Mexa 1230 PM analyzer (HORIBA, Ltd., Kyoto, Japan) for particulate measurement and the AVL CEB II analyzer (AVL, Graz, Austria) for NO_x concentration. The engine under investigation featured direct injection, turbocharging, a common-rail fuel supply system, and complied with the Stage IIIB/Tier 4 emission standard. Two types of fuel were used: conventional diesel fuel (DF) and diesel with a 10% ethanol additive by volume (DFE10). In addition to emissions measurements, key engine performance parameters, such as torque, effective power, and fuel consumption, were analyzed. The ESC test was specifically chosen to isolate the influence of the fuel’s properties by avoiding the effects of changes in combustion control strategies. Due to the lower calorific value of DFE10 compared to DF, a slight increase in fuel consumption was observed under certain operating conditions. Nevertheless, overall engine performance remained largely unchanged. The test results showed that the use of DFE10 led to a significant 44% reduction in particulate matter emissions and a moderate 2.2% decrease in NO_x emissions compared to conventional diesel fuel. These findings highlight the potential of ethanol as a diesel fuel additive to reduce harmful exhaust emissions without negatively affecting the performance of modern diesel engines. Full article

Diesel particulate matter (DPM) represents a deleterious environmental contaminant that necessitates the development of effective catalytic oxidation methodologies. This research delineates a comparative analysis of silver-supported metal oxide catalysts (Ag/Al₂O₃, Ag/TiO₂, Ag/ZnO, and Ag/CeO₂), with an emphasis on the effects of silver distribution and the metal-support interaction on the oxidation of DPM. An array of characterization techniques including XRD, HRTEM, XPS, H₂-TPR, TEM, GC-MS, TGA, and in situ DRIFTS was employed. The novelty of this study resides in elucidating the oxidation mechanism through a tripartite pathway and recognizing Ag⁰ as the predominant active species involved in soot oxidation. The Ag/Al₂O₃ catalyst demonstrated superior catalytic performance, achieving a reduction in the ignition temperature by more than 50 °C, attributable to the optimal dispersion of Ag nanoparticles and a balanced metal-support interaction. Conversely, an excessive interaction observed in Ag/ZnO resulted in diminished catalytic activity. The oxidation of DPM transpires through the volatilization of VOCs (<300 °C), the oxidation by reactive oxygen species, and the combustion of soot (>300 °C). This investigation offers significant contributions to the formulation of highly efficient silver-based catalysts for emissions control, with a particular focus on optimizing Ag dispersion and support interactions to enhance catalytic efficacy. Full article

Air pollution, particularly from vehicular emissions, has emerged as a critical environmental health concern, contributing to a global estimated 7 million premature deaths annually. Diesel exhaust, a major component of urban air pollution, contains fine particulate matter and gases that evade respiratory filtration, penetrating deep into the lungs and triggering oxidative stress, inflammation, and immune dysregulation. Epidemiological and in vitro studies have linked diesel exhaust exposure to respiratory diseases such as asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and lung cancer, with immunological mechanisms playing a central role. Diesel exhaust particles induce oxidative stress, impair macrophage phagocytosis, and skew T-cell polarization toward pro-inflammatory Th2 and Th17 responses, exacerbating chronic inflammation and tissue damage. Despite these insights, significant gaps remain in understanding the precise immunomodulatory pathways and long-term systemic effects of diesel exhaust exposure. While animal models and in vitro studies provide valuable data, they often fail to capture the complexity of human exposure and immune responses. Further research is needed to elucidate the mechanisms underlying diesel exhaust-induced immune dysregulation, particularly in vulnerable populations with pre-existing respiratory conditions. This review focuses on summarizing the current knowledge and identifying gaps that are essential for developing targeted interventions and policies to mitigate the adverse health impacts of diesel exhaust and improve respiratory health outcomes globally. Full article