Emission Control Strategies Research Articles

Developing and analyzing eco-driving strategies for on-road emission reduction in urban transport systems - A VR-enabled digital-twin approach

A vast number of pollutants are generated from on-road commuting vehicles, and there is an increasing need to explore vehicle emission monitoring and mitigation strategies. Traditionally, vehicle emissions can be monitored and measured directly from on-vehicle devices such as a sensor at the tailpipe, or based on expensive data collection tools such as roadside units; while another mainstream research estimates vehicle emissions by relying on the connection to the vehicle motions, which can approximately calculate vehicle emissions under certain traffic conditions. This paper proposes a virtual reality (VR) enabled digital twin platform for on-road emission monitoring, and it develops and evaluates eco-driving strategies within a specific area. The proposed approach, integrating a VR-based digital environment, a micro-simulation model for background traffic, and a Motor Vehicle Emission Simulator for emission estimation, offers an alternative to collect and examine vehicle emissions such as NOx under various traffic conditions. A case study on a central business area in Melbourne is conducted and eco-driving strategies are tested in two scenarios. The first scenario concerns the impact of hybrid electric vehicles and connected autonomous vehicles, which points to the long-term benefit of having controllable and cleaner modes of transportation as a strategy. Results showed that manipulating the penetration rate of emission-friendly engines or motions could reduce vehicle emissions effectively. The second scenario concerns the real-time eco-routing based on emission-optimum, which points to the short-term benefit of emission control strategies. Human-in-the-loop experiments were conducted to test drivers’ responses toward routing options. Results showed that over 90% of participants would follow the eco-routing recommendations completely. The presented study offers an alternative to data-generating, analyzing, and managing approaches for on-road emissions in urban transportation systems.

Separately resolving NOx and VOC contributions to ozone formation

Ozone (O3) is widely recognized as a significant air pollutant that affects public health across the globe. O3 is formed from precursor emissions of oxides of nitrogen (NOx) and volatile organic compounds (VOCs) that react in the atmosphere, making it complex to identify the major source contributions to O3 concentrations. O3 source apportionment calculations within chemical transport models (CTMs) provide a specialized approach to resolve source contributions. Traditional O3 apportionment techniques track source contributions based on the chemical formation regime, but they do not separately distinguish between NOx and VOC source contributions. In this study, a new O3 source apportionment technique was developed to explicitly resolve the contributions from both NOx and VOC sources in order to provide a more detailed view on O3 source origins so that policy makers can design more effective emission control strategies. The new technique is flexible and can be configured to identify the original source of precursors that contribute to O3 formation or the most recent source depending on the choice of the tagging method. The detailed features of the new technique are demonstrated during a peak O3 event in September 2010 in Los Angeles, while trends in O3 source contributions over time are evaluated during two additional simulations in July 2005 and August 2015. Quality control checks show that the new source apportionment methodology does not alter predicted total O3 concentrations, and the detailed source apportionment information can be averaged to yield results that are consistent with traditional O3 source apportionment calculations. The detailed O3 source apportionment results during Sept 2010 show that, among NOx sources, on-road gasoline, on-road diesel, off-road diesel, and soil NOx account for over 60% of the ground level O3 concentrations. Among VOC sources, upwind boundary conditions and biogenic sources account for approximately 90% of the ground-level O3 formed. The formaldehyde to NO2 ratio suggests that the chemical regime in the year 2015 was VOC-limited, but given the uncontrollable nature of the VOC emissions, the results suggest that NOx emission controls would have been the preferred emission control strategy to reduce O3 concentration in Los Angeles at that time, with the understanding that some period of O3 disbenefits would need to be tolerated until the emissions control program shifts the atmospheric chemistry back into the NOx-limited regime. The NOx source apportionment results for O3 identify the largest NOx sources that could be reduced in an effort to reach NOx-limited conditions. The chemical regime in the Los Angeles atmosphere is continuously evolving, and so these calculations would need to be repeated under current conditions to determine if we have arrived at this NOx limited regime. Future studies will undertake this analysis.

Joint increase of aerosol scattering efficiency and aerosol hygroscopicity aggravate visibility impairment in the North China Plain

China's “Blue Sky Action Plan” aimed at tremendous improvements in atmospheric visibility. While stringent emission control policies have substantially brought down PM2.5 mass concentrations, visibility improved much less than expected due to non-linear responses of visibility changes to PM2.5 reductions. In this study, we used long-term continuous humidified nephelometer system measurements of multi-wavelength aerosol scattering coefficients in both dry state and controlled relative humidity conditions in the North China Plain during spring and summer to attempt disentanlge the non-linear relationsips between visibility and PM2.5 mass.Aerosol scattering efficiency, optical hygroscopicity and air relative humidity are key factors for relating PM2.5 mass to visibility. It was found that aerosol volume scattering efficiencies (VSEs) were highly correlated (r > 0.8) with aerosol scattering coefficients. The continuous decrease of aerosol scattering Ångström exponent during pollution episodes revealed dominant contributions of secondary aerosol formation to aerosol size growth and mass accumulation, explaining aerosol VSE increases. Moreover, the optical hygroscopicity parameter κsca that describes the aerosol light scattering enhancement abilities through water uptake increased jointly with VSE and aggravated the visibility degradation during middle to final stages of pollution episodes. Thus, low visibility events (<3 km) only occurred when VSE and κsca were at their highest levels. The contribution of aerosol water to visibility degradation increased as visibility decreased, and contributed dominantly to visibility degradation under extremely low visibility conditions (<1 km). However, under hazy visibility conditions (3–10 km), which occurred most frequently, both aerosol water and scattering efficiency enhancement played significant roles. For setting up more efficient emission control strategies targeting on visibility improvement, our results highly encourage more future research on the linkages between secondary aerosol formation mechanisms and co-variations of aerosol scattering efficiency and aerosol hygroscopicity on the NCP.

Response surface model based emission source contribution and meteorological pattern analysis in ozone polluted days

Urban and regional ozone (O3) pollution is a public health concern and causes damage to ecosystems. Due to the diverse emission sources of O3 precursors and the complex interactions of air dispersion and chemistry, identifying the contributing sources of O3 pollution requires integrated analysis to guide emission reduction plans. In this study, the meteorological characteristics leading to O3 polluted days (in which the maximum daily 8–h average O3 concentration is higher than the China Class II National O3 Standard (160 μg/m3)) in Guangzhou (GZ, China) were analyzed based on data from 2019. The O3 formation regimes and source apportionments under various prevailing wind directions were evaluated using a Response Surface Modeling (RSM) approach. The results showed that O3 polluted days in 2019 could be classified into four types of synoptic patterns (i.e., cyclone, anticyclone, trough, and high pressure approaching to sea) and were strongly correlated with high ambient temperature, low relative humidity, low wind speed, variable prevailing wind directions. Additionally, the cyclone pattern strongly promoted O3 formation due to its peripheral subsidence. The O3 formation was nitrogen oxides (NOx)-limited under the northerly wind, while volatile organic compounds (VOC)-limited under other prevailing wind directions. Anthropogenic emissions contributed largely to the O3 formation (54–78%) under the westerly, southwesterly, easterly, southeasterly, or southerly wind, but only moderately (35–47%) under the northerly or northeasterly wind. Furthermore, as for anthropogenic contributions, local emission contributions were the largest (39–60%) regardless of prevailing wind directions, especially the local NOx contributions (19–43%); the dominant upwind regional emissions contributed 12–46% (e.g., contributions from Dongguan were 12–20% under the southeasterly wind). The emission control strategies for O3 polluted days should focus on local emission sources in conjunction with the emission reduction of upwind regional sources.

Evaluation of Long-Term Modeling Fine Particulate Matter and Ozone in China During 2013–2019

Air quality in China has been undergoing significant changes due to the implementation of extensive emission control measures since 2013. Many observational and modeling studies investigated the formation mechanisms of fine particulate matter (PM2.5) and ozone (O3) pollution in the major regions of China. To improve understanding of the driving forces for the changes in PM2.5 and O3 in China, a nationwide air quality modeling study was conducted from 2013 to 2019 using the Weather Research and Forecasting/Community Multiscale Air Quality (WRF/CMAQ) modeling system. In this study, the model predictions were evaluated using the observation data for the key pollutants including O3, sulfur dioxide (SO2), nitrogen dioxide (NO2), and PM2.5 and its major components. The evaluation mainly focused on five major regions, that is , the North China Plain (NCP), the Yangtze River Delta (YRD), the Pearl River Delta (PRD), the Chengyu Basin (CY), and the Fenwei Plain (FW). The CMAQ model successfully reproduced the air pollutants in all the regions with model performance indices meeting the suggested benchmarks. However, over-prediction of PM2.5 was noted in CY. NO2, O3, and PM2.5 were well simulated in the north compared to the south. Nitrate (NO3−) and ammonium (NH4+) were the most important PM2.5 components in heavily polluted regions. For the performance on different pollution levels, the model generally over-predicted the clean days but underpredicted the polluted days. O3 was found increasing each year, while other pollutants gradually reduced during 2013–2019 across the five regions. In all of the regions except PRD (all seasons) and YRD (spring and summer), the correlations between PM2.5 and O3 were negative during all four seasons. Low-to-medium correlations were noted between the simulated PM2.5 and NO2, while strong and positive correlations were established between PM2.5 and SO2 during all four seasons across the five regions. This study validates the ability of the CMAQ model in simulating air pollution in China over a long period and provides insights for designing effective emission control strategies across China.

Direct measurements of ozone response to emissions perturbations in California

Abstract. A new technique was used to directly measure O3 response to changes in precursor NOx and volatile organic compound (VOC) concentrations in the atmosphere using three identical Teflon smog chambers equipped with UV lights. One chamber served as the baseline measurement for O3 formation, one chamber added NOx, and one chamber added surrogate VOCs (ethylene, m-xylene, n-hexane). Comparing the O3 formation between chambers over a 3-hour UV cycle provides a direct measurement of O3 sensitivity to precursor concentrations. Measurements made with this system at Sacramento, California, between April–December 2020 revealed that the atmospheric chemical regime followed a seasonal cycle. O3 formation was VOC-limited (NOx-rich) during the early spring, transitioned to NOx-limited during the summer due to increased concentrations of ambient VOCs with high O3 formation potential, and then returned to VOC-limited (NOx-rich) during the fall season as the concentrations of ambient VOCs decreased and NOx increased. This seasonal pattern of O3 sensitivity is consistent with the cycle of biogenic emissions in California. The direct chamber O3 sensitivity measurements matched semi-direct measurements of HCHO/NO2 ratios from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor (Sentinel-5P) satellite. Furthermore, the satellite observations showed that the same seasonal cycle in O3 sensitivity occurred over most of the entire state of California, with only the urban cores of the very large cities remaining VOC-limited across all seasons. The O3-nonattainment days (MDA8 O3&gt;70 ppb) have O3 sensitivity in the NOx-limited regime, suggesting that a NOx emissions control strategy would be most effective at reducing these peak O3 concentrations. In contrast, a large portion of the days with MDA8 O3 concentrations below 55 ppb were in the VOC-limited regime, suggesting that an emissions control strategy focusing on NOx reduction would increase O3 concentrations. This challenging situation suggests that emissions control programs that focus on NOx reductions will immediately lower peak O3 concentrations but slightly increase intermediate O3 concentrations until NOx levels fall far enough to re-enter the NOx-limited regime. The spatial pattern of increasing and decreasing O3 concentrations in response to a NOx emissions control strategy should be carefully mapped in order to fully understand the public health implications.

Assessment of background ozone concentrations in China and implications for using region-specific volatile organic compounds emission abatement to mitigate air pollution

Mitigation of ambient ozone (O3) pollution is a great challenge because it depends heavily on the background O3 which has been poorly evaluated in many regions, including in China. By establishing the relationship between O3 and air temperature near the surface, the mean background O3 mixing ratios in the clean and polluted seasons were determined to be 35–40 and 50–55 ppbv in China during 2013–2019, respectively. Simulations using the chemical transport model (i.e., the Weather Research and Forecasting coupled with Chemistry model, WRF/Chem) suggested that biogenic volatile organic compounds (VOC) emissions were the primary contributor to the increase in the background O3 in the polluted season (BOP) compared to the background O3 in the clean season (BOC), ranging from 8 ppbv to 16 ppbv. More importantly, the BOP continuously increased at a rate of 0.6–8.0 ppbv yr−1 during 2013–2019, while the non-BOP stopped increasing after 2017. Consequently, an additional 2%–16% reduction in anthropogenic VOC emissions is required to reverse the current O3 back to that measured in the period from 2013 to 2017. The results of this study emphasize the importance of the relative contribution of the background O3 to the observed total O3 concentration in the design of anthropogenic precursor emission control strategies for the attainment of O3 standards.

Differentiated emission control strategy based on comprehensive evaluation of multi-media pollution: Case of mercury emission control

In order to comprehensively evaluate the environmental impact of multi-media mercury pollution under differentiated emission control strategies in China, a literature review and case studies were carried out. Increased human exposure to methylmercury was assessed through the dietary intake of residents in areas surrounding a typical coal-fired power plant and a zinc (Zn) smelter, located either on acid soil with paddy growth in southern China, or on alkaline soil with wheat growth in northern China. Combined with knowledge on speciated mercury in flue gas and the fate of mercury in the wastewater or solid waste of the typical emitters applying different air pollution control devices, a simplified model was developed by estimating the incremental daily intake of methylmercury from both local and global pollution. Results indicated that air pollution control for coal-fired power plants and Zn smelters can greatly reduce health risks from mercury pollution, mainly through a reduction in global methylmercury exposure, but could unfortunately induce local methylmercury exposure by transferring more mercury from flue gas to wastewater or solid waste, then contaminating surrounding soil, and thus increasing dietary intake via crops. Therefore, tightening air emission control is conducive to reducing the comprehensive health risk, while the environmental equity between local and global pollution control should be fully considered. Rice in the south tends to have higher bioconcentration factors than wheat in the north, implying the great importance of strengthening local pollution control in the south, especially for Zn smelters with higher contribution to local pollution.

Chemical kinetic investigation on NOx emission of SI engine fueled with gasoline-ethanol fuel blends

Understanding the nitrogen oxide (NOx) formation chemical kinetic mechanism and analyzing the effect of relevant influence parameters are the effective strategy for NOx emission control. Based on the essential role of ethanol-gasoline blends among oxygenate alternative fuel, the experiments in a GDI (gasoline direct injection) SI (spark ignition) engine and the chemical kinetic simulation were carried out. According to the validated model, seven NO contributing reactions and three reaction pathways were observed. Besides the thermal NO formation pathway, two other pathways with N2O and NNH through NH-HNO-NO have nonnegligible places in the high engine speed condition. As for the parameters, initial temperature aggravates NO emission, initial pressure and ethanol fraction inhibit NO, which influence it through thermal NO pathway and have slight impact on the other two pathways. While with the increase of equivalence ratio (ER) from 0.5 to 1.0, ER promotes first and then resists NO formation, getting highest emission when ER equals to 0.85. In a lean burn condition, the thermal pathway is highly inhibited and the N2O pathway is sharply accelerated. Through current work, NOx producing mechanism under high-speed condition is investigated comprehensively, which not only completes the total NO formation pathways from atmospheric N2 but also provides reference for the designing and modification of low harmful NOx emitting gasoline-ethanol engines.

A numerical study on fuel film and emissions formations during cold start in a diesel engine using an improved spray-wall impingement model

Understanding the physical process such as fuel film formation during cold start is essential to reduce engine emissions. In this study, an improved spray-wall impingement model was applied to the cold-start simulation of a diesel engine. The fuel film and emissions formations during cold start were studied in depth. The effects of injection strategies were investigated by the use of various designed injection schemes. The results showed that a certain amount of fuel film is deposited on the wall surface due to the poor spray evaporation caused by the adverse thermal atmosphere in the cylinder. The low combustion temperature, insufficient oxygen, and the deposited fuel film are the primary causes for high HC, CO and soot emissions. The NOx emissions are relatively low because of low combustion temperature and oxygen content. A double injection strategy can reduce the deposited and remaining fuel film by 13% due to improved mixing, which benefits the reduction of HC and CO emissions, while it has a negligible effect on NOx and soot emissions. The percentage of first injected fuel has little impact on the amount of the remaining fuel film and emissions in the studied range. Increasing engine speed can inhibit the formations of fuel film, HC, CO, and soot emissions, which is due to the improved fuel evaporation, better flow motion, and thermal environment in the cylinder. Double injection allows a smaller amount of injected fuel to obtain a stable ignition. Decreasing the injected fuel mass can suppress the formation of fuel film and improve mixing, thus reducing HC, CO, and soot emissions. This work expands the application scenarios of the newly developed spray-wall impingement model. The new model has been successfully applied to investigate the cold start process of diesel engines in detail. The results provide insights into the fuel film formation and its effect on emissions, which can guide the development of a cold-start emission control strategy.

What drives long-term PM2.5-attributable premature mortality change? A case study in central China using high-resolution satellite data from 2003 to 2018.

Ambient PM2.5 was reported to be related to numerous negative health outcomes, leading to adverse public health impacts in many countries such as China. Despite the apparent reduction in PM2.5 levels over China due to its emission control policies in recent years, the health burdens were not reduced as much as expected. This calls for a comprehensive analysis to explain the reasons behind to provide a useful reference for formulating effective emission control strategies. Taking central China as an example due to its large population and high levels of PM2.5, this study quantified the spatiotemporal dynamics of premature mortality associated with PM2.5 pollution in central China for each year during 2003-2018 and applied a decomposition analysis to dissect the contribution of various driving factors including ambient PM2.5 level, demographic distribution and baseline incidence rate of four diseases related to air pollution. Results show significant spatiotemporal variations in PM2.5-attributed health impact in central China, including Henan, Hubei, and Hunan provinces. Five Henan cities had the largest PM2.5-attributable premature mortality (∼8-12K premature mortalities), while three Hubei cities and one Hebei city had the least chronic PM2.5-related all-cause mortality numbers (<1 K mortalities). Throughout the study period, the PM2.5-caused premature mortality decreased by 54K, in which changes in PM2.5 levels and baseline incidence rates of stroke and chronic obstructive pulmonary disease contributed to the positive effect, whereas demographic changes and baseline incidence rate change of ischemic heart disease and lung cancer brought a countervailing effect. Our findings suggest more dynamic and comprehensive policies and measures that take into account spatiotemporal variations of health burden for effective alleviation of the health impact of PM2.5 pollution in the country.

Declines and peaks in NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; pollution during the multiple waves of the COVID-19 pandemic in the New York metropolitan area

The COVID-19 pandemic created an extreme natural experiment in which sudden changes in human behavior and economic activity resulted in significant declines in nitrogen oxide (NO x ) emissions, immediately after strict lockdowns were imposed. Here we examined the impact of multiple waves and response phases of the pandemic on nitrogen dioxide (NO2) dynamics and the role of meteorology in shaping relative contributions from different emission sectors to NO2 pollution in post-pandemic New York City. Long term (> 3.5 years), high frequency measurements from a network of ground-based Pandora spectrometers were combined with TROPOMI satellite retrievals, meteorological data, mobility trends, and atmospheric transport model simulations to quantify changes in NO2 across the New York metropolitan area. The stringent lockdown measures after the first pandemic wave resulted in a decline in top-down NO x emissions by approx. 30% on top of long-term trends, in agreement with sector-specific changes in NO x emissions. Ground-based measurements showed a sudden drop in total column NO2 in spring 2020, by up to 36% in Manhattan and 19%-29% in Queens, New Jersey (NJ), and Connecticut (CT), and a clear weakening (by 16%) of the typical weekly NO2 cycle. Extending our analysis to more than a year after the initial lockdown captured a gradual recovery in NO2 across the NY/NJ/CT tri-state area in summer and fall 2020, as social restrictions eased, followed by a second decline in NO2 coincident with the second wave of the pandemic and resurgence of lockdown measures in winter 2021. Meteorology was not found to have a strong NO2 biassing effect in New York City after the first pandemic wave. Winds, however, were favorable for low NO2 conditions in Manhattan during the second wave of the pandemic, resulting in larger column NO2 declines than expected based on changes in transportation emissions alone. Meteorology played a key role in shaping the relative contributions from different emission sectors to NO with low-speed (< 5 ms-1) SW-SE winds enhancing contributions from the high-emitting power-generation sector in NJ and Queens and driving particularly high NO2 pollution episodes in Manhattan, even during - and despite - the stringent early lockdowns. These results have important implications for air quality management in New York City, and highlight the value of high resolution NO2 measurements in assessing the effects of rapid meteorological changes on air quality conditions and the effectiveness of sector-specific NO x emission control strategies.

Long-term winter observation of nitrous acid in the urban area of Beijing

The particulate matter (PM) pollution has been significantly improved by carrying out various valid emission control strategies since 2013 in China. Meanwhile the variation trend of nitrous acid (HONO) is worthy to investigate due to its vital role in the atmospheric oxidation process. In this study, field observation in the winter is conducted to investigate the concentration of HONO in an urban area of Beijing. In the winter of 2019, the mean HONO concentration is 1.38 ppbV during the whole winter. Photo-enhanced NO2 heterogeneous reactions on the ground and aerosol surfaces were found as the possible daytime sources of HONO. Compared to O3, photolysis of HONO dominates the primary OH sources during the winter time. To understand the HONO pollution patterns by years variation, multi-year data is summarized and finds that primary pollutants including CO and NO decreased, but secondary pollutants i.e., HONO (mostly generated via secondary process) increased. Our study highlights the requirement to mitigate secondary pollution by control HONO concentration.

Dispersion simulations in an Andean city: Role of continuous traffic data in the spatio-temporal distribution of traffic emissions

Emissions information is essential for air quality modeling and management. However, detailed spatio-temporal emissions information is usually not available in urban centers of developing countries. In this study, we assess the ability of three spatio-temporal disaggregation methods for estimating traffic emissions and modeling dispersion of pollutants in the Aburrá Valley, a densely populated and complex terrain region in Colombia. The disaggregation methods, which differ on the detail in the input traffic information applied, are used to distribute annual traffic emissions for the whole study area to 1 km2 and hourly resolution. The distributed emissions are used as input in high-resolution dispersion simulations, and the simulated concentrations are compared against surface observations. In general, simulated pollution levels reproduce adequately observations. Results show that methods using a higher level of detail (continuous traffic information and road density) improved the representation of emissions dynamics, the dispersion of pollutants, and allocated higher emissions in zones of higher road density and traffic. Thus, these methods can be used to improve high-resolution simulations. Our results show that the selection of a disaggregation method should be rigorously analyzed in order to perform a spatio-temporal distribution of emissions. This approach provides insights for emissions control strategies and can be applied in other regions with available traffic information.

Study on the effect of supercritical CFB boiler air preheater and flue gas treatment facilities on sulfur trioxide emission characteristics

The current situation of air pollution in China is very serious, and the control of non-conventional pollutants in addition to conventional air pollutants has received more and more attention. The emission of SO3 in flue gas has attracted widespread attention due to the environmental hazards and equipment problems caused by it, and the study of its emission characteristics and control strategies is the basis for national, local and industry to formulate relevant policies and implement emission control work. The SO3 monitoring and emission control study of a supercritical circulating fluidized bed boiler was carried out based on the controlled condensation method of on-site flue gas sampling, laboratory testing, and instrumental analysis of coal and ash samples, and the synergistic SO3 removal capability of the air preheater and flue gas treatment facilities was explored and summarized. The results showed that the SO3 co-removal rate of the four operating conditions of the test unit ranged from 74.34% to 88.51%, and the highest SO3 co-removal rate (88.51%) was achieved when the SNCR ammonia to nitrogen molar ratio was 1.2 and the slurry pH of the desulfurization system was 5.45 (primary tower) and 6.28 (secondary tower). During the test period, the differential pressure of the air preheater basically fluctuated between 1.245 kPa–1.326 kPa under the operating conditions of working condition 2, with no significant increase. For the same type of unit, the ammonia to nitrogen molar ratio and wet FGD slurry pH can be adjusted to reduce SO3 emissions.

Understanding the underlying mechanisms governing the linkage between atmospheric oxidative capacity and ozone precursor sensitivity in the Yangtze River Delta, China: A multi-tool ensemble analysis.

Continued exacerbation of ozone (O3) pollution in China has driven the urgent need for an emission control strategy that efficiently reduces O3 levels. Determining O3 precursor sensitivity (OPS) and its driving factors is a prerequisite for formulating effective O3 control strategies. In this study, we proposed an atmospheric oxidative capacity-based indicator, HO2/OH, and demonstrated its effectiveness in indicating OPS over the Yangtze River Delta (YRD) of China by applying a localized comprehensive air quality model with extensions (CAMx) coupled with the Weather Research and Forecasting (WRF) model. A strong correlation was discovered between HO2/OH and OPS, and HO2/OH showed the best performance in separating NOx- and VOC-limited regimes in comparison with other commonly used indicators. A comprehensive analysis with ensemble diagnostic tools revealed the spatial heterogeneity of NOx and VOC emissions and the impact of regional transport controlling the relationship between OPS variations and the HO2/OH indicator over the YRD. The process analysis results show that days with higher contributions from horizontal advection favored OPS transitions in Shanghai, Nanjing, Hefei, Suzhou, and Wuhu, while vertical advection caused OPS transitions in Hangzhou and Ningbo. O3 source apportionment technology analysis indicated that the regional contributions from Zhejiang and Jiangsu/Anhui corresponded well to the NOx-limited and VOC-limited regimes, respectively. Our results provide a better understanding of the underlying mechanisms of the relationship between OPS and the HO2/OH indicator and can help guide contingency control measures for O3 despiking over the YRD and other photochemically active regions worldwide.

Analysis and Prediction Model of Fuel Consumption and Carbon Dioxide Emissions of Light-Duty Vehicles

Due to the alarming rate of climate change, fuel consumption and emission estimates are critical in determining the effects of materials and stringent emission control strategies. In this research, an analytical and predictive study has been conducted using the Government of Canada dataset, containing 4973 light-duty vehicles observed from 2017 to 2021, delivering a comparative view of different brands and vehicle models by their fuel consumption and carbon dioxide emissions. Based on the findings of the statistical data analysis, this study makes evidence-based recommendations to both vehicle users and producers to reduce their environmental impacts. Additionally, Convolutional Neural Networks (CNN) and various regression models have been built to estimate fuel consumption and carbon dioxide emissions for future vehicle designs. This study reveals that the Univariate Polynomial Regression model is the best model for predictions from one vehicle feature input, with up to 98.6% accuracy. Multiple Linear Regression and Multivariate Polynomial Regression are good models for predictions from multiple vehicle feature inputs, with approximately 75% accuracy. Convolutional Neural Network is also a promising method for prediction because of its stable and high accuracy of around 70%. The results contribute to the quantifying process of energy cost and air pollution caused by transportation, followed by proposing relevant recommendations for both vehicle users and producers. Future research should aim towards developing higher performance models and larger datasets for building APIs and applications.

Toxic potency-adjusted control of air pollution for solid fuel combustion

The combustion of solid fuels, including coal and biomass, is a main anthropogenic source of atmospheric particulate matter (PM). The hidden costs have been underestimated due to lack of consideration of the toxicity of PM. Here we report the unequal toxicity of inhalable PM emitted from energy use in the residential sector and coal-fired power plants (CFPPs). The incomplete burning of solid fuels in household stoves generates much higher concentrations of carbonaceous matter, resulting in more than one order of magnitude greater toxicity than that from CFPPs. When compared with CFPPs, the residential sector consumed only a tenth of solid fuels in mainland China in 2017, but it contributed about 200-fold higher of the population-weighted toxic potency-adjusted PM2.5 exposure risk. We suggest that PM2.5-related toxicity should be considered when making air pollution emission control strategies, and incomplete combustion sources should receive more policy attention to reduce exposure risks.

One-step synergistic optimization of hierarchical pore topology and nitrogen dopants in activated coke for efficient catalytic oxidation of nitric oxide

Carbon-catalyzed oxidation represents a promising strategy for nitrogen oxide emission control. Here, we report a new strategy to simultaneously optimize the pore topology and doping environment of activated coke (AC) catalyst through one-step catalytic activation process with nitrogen resource in-situ participation. Dynamic experiments of nitric oxide catalytic oxidation using the prepared activated cokes with controllable pore configurations and doping environment firstly demonstrate that hierarchical pore configuration and nitrogen functional groups can synergistically improve catalytic oxidation activity. Especially, nitrogen-doped hierarchical porous AC catalyst exhibits the highest conversion efficiency (above 70%). Based on density functional theory calculations in combination with control experiments using pyridinic nitrogen and quaternary nitrogen-dominant catalysts, a new activity descriptor of electrophilic Fukui function is proposed and quaternary nitrogen is thereby identified to be the optimal nitrogen doping configuration towards nitric oxide catalytic oxidation. This work provides new insights into the synergistic role of pore topology and nitrogen doping in nitric oxide low-temperature oxidation, giving guidance for designing high-performance carbocatalyst.

ENVIRONMENTAL POLLUTION: EFFECT ON PEDESTRIANS WHILE WALKING IN URBAN STREET

Purpose: The reason for this study is because of observed difference in environmental condition in Lagos metropolis. The change is witnessed in environmental change arising from air, water and noise pollution mostly from increasing vehicle emissions in the State. This study has been conducted to analyze the environmental effects of pollution on pedestrians. Specific objectives are determine the air quality of the city at most populate headquarters of each of the 20 Local Government Areas of Lagos State, to examine the impact of pollution (air, water and noise) on pedestrians and assess various measures for reducing environmental pollution in the State.&#x0D; Methodology: The use of Thermo scientific MIE pDR-1500 instrument was used to measure air quality index of the selected locations and survey was carried out with well-structured questionnaire to elicit information with the aid of incidental sampling technique on impact of pollution on pedestrians from 177 respondents.&#x0D; Findings: Air Quality Index was shown with histogram chart where six out of 20 Local Government Areas are above the acceptable standard of pollution. There is rising cases of pollution in the State and very few Local governments were within acceptable range. One –Sample T-test showed that air pollution is majorly affecting pedestrians with t-value of 22.226 followed by noise with 19.643 and water with 5.529 respectively.&#x0D; Conclusion and recommendations: The research concluded that, there is need to control the rising cases of pollution in the state and policies to tame air and noise pollution in the state should be adopted. Emission control strategies to be adopted with the existing ones can be in form of restricting hours of movement of vehicles to late at night to avoid human pollutant contact, encourage tree planting and rapid evacuation of environmental waste.