Vehicular emissions and concentrations in school zones: A case study

Recent research has revealed that human exposure to air pollutants such as CO, NO_x, and particulates can lead to respiratory diseases, especially among school-age children. Towards understanding such health impacts, this work estimates local-scale vehicular emissions and concentrations near a highway traffic network, where a school zone is located in. In the case study, VISSIM traffic micro-simulation is used to estimate the source of vehicular emissions at each roadway segment. The local-scale emission sources are then used as inputs to the California line source dispersion model(CALINE4) to estimate concentrations across the study area. To justify the local-scale emissions modeling approach, the simulation experiment is conducted under various traffic conditions. Different meteorological conditions are considered for emission dispersion. The work reveals that emission concentrations are usually higher at locations closer to the congested segments, freeway ramps and major arterial intersections. Compared to the macroscopic estimation(i.e. using network-average emission factors), the results show significantly different emission patterns when the local-scale emission modeling approach is used. In particular, it is found that the macroscopic approach over-estimates emission concentrations at freeways and under-estimations are observed at arterials and local streets. The results of the study can be used to compare to the US environmental protection agency(EPA) standards or any other air quality standard to further identify health risk in a fine-grained manner.

Do vehicular emissions dominate the source of C6–C8 aromatics in the megacity Shanghai of eastern China?

The characteristic ratios of volatile organic compounds（VOCs） to i-pentane, the indicator of vehicular emissions, were employed to apportion the vehicular and non-vehicular contributions to reactive species in urban Shanghai. Two kinds of tunnel experiments, one tunnel with more than 90% light duty gasoline vehicles and the other with more than 60% light duty diesel vehicles, were carried out to study the characteristic ratios of vehicle-related emissions from December 2009 to January 2010. Based on the experiments, the characteristic ratios of C6–C8aromatics to i-pentane of vehicular emissions were 0.53 ± 0.08（benzene）, 0.70 ± 0.12（toluene）,0.41 ± 0.09（m,p-xylenes）, 0.16 ± 0.04（o-xylene）, 0.023 ± 0.011（styrene）, and 0.15 ± 0.02（ethylbenzene）, respectively. The source apportionment results showed that around 23.3% of C6–C8 aromatics in urban Shanghai were from vehicular emissions, which meant that the non-vehicular emissions had more importance. These findings suggested that emission control of non-vehicular sources, i.e. industrial emissions, should also receive attention in addition to the control of vehicle-related emissions in Shanghai. The chemical removal of VOCs during the transport from emissions to the receptor site had a large impact on the apportionment results. Generally, the overestimation of vehicular contributions would occur when the VOC reaction rate constant with OH radicals（k OH） was larger than that of the vehicular indicator, while for species with smaller k OH than the vehicular indicator, the vehicular contribution would be underestimated by the method of characteristic ratios.

Impacts of methanol fuel on vehicular emissions:A review

The transport sector is a significant energy consumer and a major contributor to urban air pollution.At present,the substitution of cleaner fuel is one feasible way to deal with the growing energy demand and environmental pollution.Methanol has been recognized as a good alternative to gasoline due to its good combustion performance.In the past decades,many studies have investigated exhaust emissions using methanol-gasoline blends.However,the conclusions derived from different studies vary significantly,and the explanations for the effects of methanol blending on exhaust emissions are also inconsistent.This review summarizes the characteristics of CO,HC,NO_(x),CO_(2),and particulate emissions from methanol-gasoline blended fuels and pure methanol fuel.CO,HC,CO_(2),particle mass(PM),and particle number(PN)emissions decrease when methanol-blended fuel is used in place of gasoline fuel.NO_(x) emission either decreases or increases depending on the test conditions,i.e.,methanol content.Furthermore,this review synthesizes the mechanisms by which methanol-blended fuel influences pollutant emissions.This review provides insight into the pollutant emissions from methanol-blended fuel,which will aid policymakers in making energy strategy decisions that take urban air pollution,climate change,and energy security into account.

Assessment of Organic Compounds as Vehicular Emission Tracers in the AburráValley Region of Colombia

The Aburrá Valley region in Colombia, with Medellín as its main city, is an urban centre with about three million people. An investigation was carried out to deter-mine a set of baseline concentrations for VOC compounds associated with diesel fuel and gasoline, as vehicular emission tracers in the region. The VOC measurement campaigns, based on TENAX tube sampling and analysis according to TO-17 EPA method, were done in areas of low and high vehicular flow as well as on-board measurements covering major Medellín road networks during 24 hours. The results showed that there was a relation between VOCs concentrations and vehicular activi-ty. The diesel fuel sulfur content was also found as an important factor on VOC hy-drocarbon formation.

An Assessment of Vehicular Emission in the Vicinity of Selected Markets in Owerri, Imo State, Nigeria

This study assessed pollutants concentration at selected markets in Owerri. These markets were purposively selected after careful consideration of all major markets in the study area;the selected markets were considered to be more congested during the day as a result of open assess to road junctions coupled with a high density of vehicular movement, presence of offices, residential buildings, and human activities. Five air pollutants from vehicular emissions were monitored, namely: carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), particulate matter (PM 2.5) and particulate matter (PM 10). Assessments were carried out within 3 hours per dual diurnal section using approved standard methods which were converted to a 1-hour mean for the morning and afternoon period of sampling 7-10 am and 2-5 pm. These periods are known for the peak of human and vehicular movement within the study area. Results show that the highest level of CO concentration (0.293 - 0.387 ppm) was recorded at Alaba market and is less than the permissible limit of 35 ppm given by national ambient air quality standard (NAAQS). The highest range of CO2 (1153 - 1875 ppm) was recorded from Alaba market which is higher than the ambient standard of 314 ppm. The highest level of NO2 (0.116 - 0.297 ppm) was recorded from Relief market which is also higher than the permissible limit (0.100 ppm) of NAAQS. The highest range of particulate matter of PM 2.5 and PM 10 was recorded from Relief market (0.011 - 0.029 μg/m3) and (0.065 - 0.172 μg/m3) respectively and is far lower than the permissible limit (150 μg/m3) of NAAQS and WHO (base on target 1) standards. The study, therefore, concludes that there is a significant impact of emission from vehicles in the selected markets in Owerri metropolis as result indicates a high risk of health problems in the markets due to the high level of CO2 and NO2. It, therefore, recommends that an adequate mechanism should be put in place to decongest traffic density in the city especially near markets so as to have a substantial reduction in vehicular emissions and improve the livability of the citizens.

Comparative measurement of CO_(2),CH_(4)and CO at two traffic interjunctions having inflated vehicular flow in Delhi

Vehicular emissions are considered one of the major anthropogenic sources of greenhouse gases and poor air quality in metropolitan cities.This study aims to see the correlation of CO_(2),CH_(4),and CO through monitoring over a period from December 2020 to October 2021 covering three seasons’winter,summer,and monsoon at two different traffic locations of Delhi having different traffic volumes,road patterns,and traffic management.The annual average morning concentration of CO_(2),CH_(4)and CO was found(533±105),(7.3±3.1),(10.7±3.0)ppm at Najafgarh and(480±70),(5.2±1.8),(7.8±2.8)ppm at Rajendra Place,respectively.A relationship between concentration of all three gases and meteorological parameters such as temperature,humidity,wind speed and wind direction has also been investigated using Pearson correlation coefficient and pollution rose diagram.A comparable pattern in concentration was observed for all three gases in spatial(location)and temporal(diurnal)distribution.The concentration trend of CO_(2)in different seasons is winter>summer>monsoon,while in the case of CH_(4)winter=summer>monsoon but not any seasonal trend was noted in CO case.It is observed that CO_(2)has a good relation with CO(a tracer for vehicular emission)in terms of diurnal variation,whereas,CH_(4)does not represent a relation with CO and CO_(2)diurnally,suggesting that vehicles are the source of CO_(2)but not much contributing to other greenhouse gases like CH_(4).

Numerical study on the ozone formation inside street canyons using a chemistry box model

Tropospheric ozone is a secondary air pollutant produced in the presence of nitrogen oxides (NO_x),volatile organic compounds (VOCs),and solar radiation.In an urban environment,ground-level vehicular exhaust is the major anthropogenic source of ozone precursors.In the cases of street canyons,pollutant dilution is weakened by the surrounding buildings that creates localized high concentration of NO_x and VOCs,and thus leads to high potential of ozone formation.By considering the major physical and chemical p...

Road transport and urban air quality in China

This paper takes a comprehensive view at transportationrelated air pollution problems and solution options. While the transport infrastructure in major Chinese cities is briefed, the environmental impacts of transport activities on urban air quality are discussed in detail. Not only the contribution of automotive emissions to the CO, NMHC and NO\-x pollution in urban areas is reviewed, but also concerns over the carcinogenic emissions, lead deposition and noise are presented. From a lifecycle view point, the impacts of motorway construction, as well as those from scrapped cars, car batteries and old tires in China have been taken into account. In the second part of this paper, the current technical efforts to curb vehicular emissions are evaluated. The performances of unleaded petrol, domestic catalytic converters, and fuel injection systems have been assessed. Options of cleaner alternative fuels and “green” vehicles are discussed, with both the life-cycle impacts and economic feasibility emphasized. Policy and management aspects for effective pollution control are tackled. In particular, speculations about potential economic incentives and legislative measures for vehicular pollution control are presented.

Choice of precipitant and calcination temperature of precursor for synthesis of NiCo_2O_4 for control of CO–CH_4 emissions from CNG vehicles

Compressed natural gas（CNG）is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants（Na2CO3,KOH and urea）for nickel cobaltite（Ni Co2O4）catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400℃.The catalysts were used for oxidation of a mixture of CO and CH4（1：1）.The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na2CO3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH4mixture at the lowest temperature（T（100）=350℃）.Whereas,for catalyst prepared using urea,T（100）=362℃.On the other hand the conversion of CO-CH4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400℃.Further,the effect of higher calcination temperatures of 500 and600℃ was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410℃ over catalysts calcined at 500 and 600℃ respectively.Thus,the best precipitant established was Na2CO3and the optimum calcination temperature of 400℃ was found to synthesize the Ni Co2O4catalyst for the best performance in CO-CH4oxidation.

Variation of spatio-temporal distribution of on-road vehicle emissions based on real-time RFID data

High-resolution vehicular emissions inventories are important for managing vehicular pollution and improving urban air quality. This study developed a vehicular emission inventory with high spatio-temporal resolution in the main urban area of Chongqing, based on realtime traffic data from 820 RFID detectors covering 454 roads, and the differences in spatiotemporal emission characteristics between inner and outer districts were analysed. The result showed that the daily vehicular emission intensities of CO, hydrocarbons, PM2.5, PM10,and NO_(x) were 30.24, 3.83, 0.18, 0.20, and 8.65 kg/km per day, respectively, in the study area during 2018. The pollutants emission intensities in inner district were higher than those in outer district. Light passenger cars(LPCs) were the main contributors of all-day CO emissions in the inner and outer districts, from which the contributors of NO_(x) emissions were different. Diesel and natural gas buses were major contributors of daytime NO_(x) emissions in inner districts, accounting for 40.40%, but buses and heavy duty trucks(HDTs) were major contributors in outer districts. At nighttime, due to the lifting of truck restrictions and suspension of buses, HDTs become the main NO_(x) contributor in both inner and outer districts,and its three NO_(x) emission peak hours were found, which are different to the peak hours of total NO_(x) emission by all vehicles. Unlike most other cities, bridges and connecting channels are always emission hotspots due to long-time traffic congestion. This knowledge will help fully understand vehicular emissions characteristics and is useful for policymakers to design precise prevention and control measures.

Vehicles and Particulate Air Pollution

The current scene relating to particles and vehicular emissions in UK is reviewed. The active research topics are health effects of particles, particle size and composition, modeling the fate of particles and assessing individual exposure. There is a National Air Quality Strategy combined with local air quality management which includes monitoring and assessment, dispersion modeling and development of management plans.