Yan Ding

As exhaust emission standards continue to tighten, evaporative emissions have attracted increasing attention, while information on motorcycles, particularly older models, remains limited. In this study, seven China II and China III motorcycles with engine displacement between 50 and 150 mL were tested using a sealed housing for evaporative determination (SHED), including standardized hot soak and 1 h diurnal breathing loss (DBL) measurements; an additional non-replicated 12 h laboratory-reproduced temperature-profile test was conducted as an exploratory comparison. Across the displacement-matched China II and China III motorcycles, DBL decreased from 6.17–11.12 g to 0.33–0.57 g, corresponding to pairwise reductions of approximately 91–97%, while hot soak loss (HSL) decreased from approximately 1.2–1.6 g to 0.07–0.29 g, corresponding to reductions of approximately 82–95%. These differences coincided with multiple evaporative-emission-control upgrades introduced with China III, including activated-carbon canisters, improved fuel-system sealing, and closed-crankcase ventilation; their individual contributions could not be isolated. In a vehicle-specific comparison between two 150 China III motorcycles, the electronic fuel injection (EFI) equipped motorcycle exhibited 66.9% lower DBL than the carburetor-equipped motorcycle, although this single comparison cannot establish a general EFI effect. The exploratory 12 h test also yielded higher cumulative DBL than the standardized 1 h procedure; however, because test duration, temperature amplitude, and temperature-change rate differed simultaneously, the individual contribution of these factors could not be separated.

Accurate and comprehensive estimation of mobile source (MS) emissions is essential for air quality management and atmospheric research. However, existing emission inventories often lack sufficient coverage of MS categories, emerging pollutants, and newly developed model parameterizations. Here, we present the Gridded Mobile-source Emission Dataset (GMED), a model-ready emission inventory with detailed source classification and multi-pollutant coverage. GMED provides monthly emissions from 2011 to 2020 at a spatial resolution of 36 km × 36 km, covering eight MS categories and including both tailpipe and non-exhaust emissions. It incorporates several methodological improvements and integrates localized measurements from multiple sources, including emission factors, organic compound speciation, spatiotemporal proxies, and activity data. Validation involves comparisons with established inventories and cross-checks of key model parameters, both showing good agreement across multiple metrics. GMED outputs also align well with high-resolution emission inventories derived from big traffic data. As a validated, long-term dataset, GMED supports emission assessments, air quality modelling, and policy evaluation, helping to fill a critical gap in differentiated, multi-year MS emission inventories.

Traffic-related activity patterns, including transportation mode choices and time spent in transit, critically influence individuals’ exposure to air pollution. This study analyzed data from three cross-sectional surveys conducted in Lanzhou, China (2015-2020), to investigate variations in transportation behavior and their impact on daily cumulative PM2.5 inhalation exposure. Results showed that walking was the most frequently used mode, accounting for over 70% of trips, while car use involved the longest average travel time - exceeding 60 min per day. However, trends in mode share and usage time were not synchronized, and the use of different transportation modes was interrelated. Sociodemographic factors and built environment features near homes and workplaces were dynamically associated with transportation behaviors. Time spent in transit had the strongest influence on cumulative daily exposure, explaining more than 90% of the variation across modes. Open modes of transport were linked to the highest exposure levels due to elevated pollutant concentrations and increased inhalation rates, whereas car transportation resulted in the lowest exposure despite its longer duration. These findings underscore the need to incorporate transportation behavior into air pollution exposure assessments and suggest that transportation policies and infrastructure planning should align mobility objectives with public health priorities.

Greenhouse gas (GHG) emissions represent a pivotal driver of global climate change, with vehicular emissions, particularly from light-duty vehicles, emerging as a prominent source of GHGs. Despite extensive research on gaseous pollutants, studies on GHG emissions within the framework of carbon neutrality remain scarce. This study delves into the emission characteristics of three primary GHGs (carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)) from various light-duty vehicles, encompassing conventional gasoline and hybrid vehicles and bi-fuel taxis. As anticipated, with advancements in emission standards and powertrains, vehicular GHG emissions have significantly decreased. However, our findings also revealed surprising trends. While engine technology upgrades reduced CO₂, they unexpectedly increased CH₄ and N₂O emissions. Additionally, hot starts, beneficial for reducing CO₂ and CH₄ emissions, caused heightened N₂O emissions, which is noteworthy under operating conditions with frequent start–stop events. Intriguingly, compressed natural gas (CNG), generally perceived as cleaner, increased CH₄ emissions. Regarding the impact of three-way-catalyst (TWC) converters on GHG emissions, under “TWC deteriorated” conditions, N₂O emissions from CNG-powered vehicles were approximately 3 times higher than those under “TWC worked” conditions, which can be attributed to the significant increase in nitrogen oxides (NO_x). Considering the global warming potential (GWP), the “TWC deteriorated” scenario paradoxically decreased GWP values, highlighting the complex interaction between emission control technologies and their environmental impacts. This study provides crucial insights into vehicular GHG emissions, which are essential for developing effective strategies aimed at mitigating emissions and enhancing the efficiency of emission control systems.

The framework of eco-driving evaluation relying on vehicle trajectory data is to quantify the disparities of the fuel consumption for individual driving behavior and to develop a baseline under various traffic conditions. The baseline represents the typical driving behavior in a city, and it is a pivotal parameter for eco-driving evaluation. The applicability of the evaluation method in different cities is overlooked, encompassing the suitability of parameters and the minimum data required. This study aims to investigate whether the evaluation baseline developed with sufficient data can be applied to a new city. The results reveal that the baseline developed in Beijing cannot be directly transferred to the eco-driving evaluation in Toronto due to the significantly more aggressive and competitive driving behavior exhibited by Toronto drivers. This study further examines the minimum data sample size necessary to develop a robust evaluation baseline and proposes a localized method to construct the evaluation system for eco-driving evaluation in different cities.

Greenhouse gas (GHG) emissions represent a pivotal driver of global climate change, with vehicular emissions, particularly from light-duty vehicles, emerging as a prominent source of GHGs. Despite extensive research on gaseous pollutants, studies on GHG emissions within the framework of carbon neutrality remain scarce. This study delves into the emission characteristics of three primary GHGs (carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)) from various light-duty vehicles, encompassing conventional gasoline and hybrid vehicles, and bi-fuel taxis. As anticipated, with advancements in emission standards and powertrains, vehicular GHG emissions have significantly decreased. However, our findings also revealed surprising trends. While engine technology upgrades reduced CO₂, they unexpectedly increased CH₄ and N₂O emissions. Additionally, hot starts, beneficial for reducing CO₂ and CH₄ emissions, caused heightened N₂O emissions, which is noteworthy under operating conditions with frequent start-stop events. Intriguingly, compressed natural gas (CNG), generally perceived as cleaner, increased CH₄ emissions. Regarding the impact of Three-Way Catalysts (TWC) on GHG emissions, under “TWC failed” conditions, N₂O emissions from CNG-powered vehicles were approximately three times higher than those under “TWC worked” conditions, attributed to the significant increase in NOx. Considering the global warming potential (GWP), the "TWC failure" scenario paradoxically decreased GWP values, highlighting the complex interaction between emission control technologies and their environmental impacts. This study provides crucial insights into vehicular GHG emissions, which are essential for developing effective strategies aimed at mitigating emissions and enhancing the efficiency of emission control systems.

Greenhouse gas (GHG) emissions represent a pivotal driver of global climate change, with vehicular emissions, particularly from light-duty vehicles, emerging as a prominent source of GHGs. Despite extensive research on gaseous pollutants, studies on GHG emissions within the framework of carbon neutrality remain scarce. This study delves into the emission characteristics of three primary GHGs (carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)) from various light-duty vehicles, encompassing conventional gasoline and hybrid vehicles, and bi-fuel taxis. As anticipated, with advancements in emission standards and powertrains, vehicular GHG emissions have significantly decreased. However, our findings also revealed surprising trends. While engine technology upgrades reduced CO₂, they unexpectedly increased CH₄ and N₂O emissions. Additionally, hot starts, beneficial for reducing CO₂ and CH₄ emissions, caused heightened N₂O emissions, which is noteworthy under operating conditions with frequent start-stop events. Intriguingly, compressed natural gas (CNG), generally perceived as cleaner, increased CH₄ emissions. Regarding the impact of Three-Way Catalysts (TWC) on GHG emissions, under “TWC failed” conditions, N₂O emissions from CNG-powered vehicles were approximately three times higher than those under “TWC worked” conditions, attributed to the significant increase in NOx. Considering the global warming potential (GWP), the "TWC failure" scenario paradoxically decreased GWP values, highlighting the complex interaction between emission control technologies and their environmental impacts. This study provides crucial insights into vehicular GHG emissions, which are essential for developing effective strategies aimed at mitigating emissions and enhancing the efficiency of emission control systems.

Greenhouse gas (GHG) emissions represent a pivotal driver of global climate change, with vehicular emissions, particularly from light-duty vehicles, emerging as a prominent source of GHGs. Despite extensive research on gaseous pollutants, studies on GHG emissions within the framework of carbon neutrality remain scarce. This study delves into the emission characteristics of three primary GHGs (carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)) from various light-duty vehicles, encompassing conventional gasoline and hybrid vehicles, and bi-fuel taxis. As anticipated, with advancements in emission standards and powertrains, vehicular GHG emissions have significantly decreased. However, our findings also revealed surprising trends. While engine technology upgrades reduced CO₂, they unexpectedly increased CH₄ and N₂O emissions. Additionally, hot starts, beneficial for reducing CO₂ and CH₄ emissions, caused heightened N₂O emissions, which is noteworthy under operating conditions with frequent start-stop events. Intriguingly, compressed natural gas (CNG), generally perceived as cleaner, increased CH₄ emissions. Regarding the impact of Three-Way Catalysts (TWC) on GHG emissions, under “TWC failed” conditions, N₂O emissions from CNG-powered vehicles were approximately three times higher than those under “TWC worked” conditions, attributed to the significant increase in NOx. Considering the global warming potential (GWP), the "TWC failure" scenario paradoxically decreased GWP values, highlighting the complex interaction between emission control technologies and their environmental impacts. This study provides crucial insights into vehicular GHG emissions, which are essential for developing effective strategies aimed at mitigating emissions and enhancing the efficiency of emission control systems.