A Quantitative Description of Vehicle Exhaust Particle Size Distributions in a Highway Tunnel (original) (raw)
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Size distribution of vehicle emitted primary particles measured in a traffic tunnel
Atmospheric Environment, 2018
Total and size-resolved concentrations and emission factors are used to compare fleet-averaged vehicle emissions in Pittsburgh, PA in 2002 and 2014. Winter-time traffic tunnel measurements acquired using dual scanning mobility particle sizers (SMPS) over the size range 3-500 nm form the key input for the analysis. Size-resolved mass emission factors were calculated assuming a nanoparticle aggregate model. The ultrafine particle (< 30 nm) emissions of diesel vehicles significantly dropped from 2002 to 2014. In the 2014 study, a thermodenuder (TD) was deployed together with the SMPS to measure emissions of non-volatile particles. After evaporation at 250°C inside the TD, the median diameter of the number-size distribution shifted from 16 nm to ∼7 nm. The total particle number decreased significantly (69%) after evaporating inside the TD, indicating that vehicle emitted particles may be largely externally mixed and that a large fraction of these particles may be purely composed of volatile components. Based on the SMPS-TD measurements, we report a size-resolved volatile-to-non-volatile-component-ratio for vehicle emitted particles. It shows that smaller particles (10-60 nm) emitted by vehicles are dominantly (over 75%) composed of volatile components. We also apportioned the sizeresolved particles and non-volatile particle mass and number emission factors for both gasoline and diesel
Applied Sciences, 2021
This study aims to analyze the seasonal number concentrations corresponding to each particle size derived from the measurements of exhausts from approximately seven million vehicles on real-world using a pair of the scanning mobility particle sizer to determine the vehicle emission rate. The actual tunnel flow coefficient was investigated for car emission rate based on the measurements of individual physical parameters (i.e., cross section area and length of the tunnel, tunnel wind speed and traffic volume). The mode of particle diameter according to temperatures in respective seasons exhibited a high correlation together with rapid changes at temperature above the breakthrough point. The temperature acted as major cause of determination of final condensation diameter, which is also dependent on diverse environmental effects comprising particle number concentration. The traffic volume of ordinary cars increased by more than twice as much in the period of Asian New Year, the traffic ...
Exhaust Particle Size Distribution Measurements at the Tuscarora Mountain Tunnel
Aerosol Science and Technology, 2002
On-road particle size distributions were measured at the Tuscarora Mountain tunnel on the Pennsylvania Turnpike in May 1999. The data were obtained using a scanning mobility particle sizer. The nucleation modes of the size distributions contained most of the particles on a number concentration basis and exhibited peak diameters ranging from 11 to 17 nm. This observation is consistent with previous calculations and measurements, indicating that signi cant numbers of ultra ne aerosol particles can be expected in close proximity to busy motorways. The experiment provided 4 case studies for which the tunnel inlet data could be used to correct data obtained at the outlet, allowing for estimates of particle production within the tunnel. Exhaust particle production rates per vehicle kilometer were estimated; the results are presented with the caveat that the measurements were affected by ambient dilution. The 4 case study nucleation mode sizes varied inversely with ambient temperature. The light-duty vehicle contributions to the ultra ne particle distributions were apparently dominated by the heavy-duty vehicle contributions.
Atmospheric Environment, 2005
On-road size-resolved particulate emission factors were computed using concurrently measured carbon monoxide (CO) as a freeway dilution indicator and correlating roadside particle measurements to CO measurements. The emission factors derived for the total particle number agree well with previous on-road investigations. However, this study extends this analysis to produce unique receptor-dependent, size-resolved, road and grid-level emission factor distributions. Both mileage-and fuel-based particle number and mass emission factors at road and grid levels, along with CO emission factors, are presented and the results from freeways with distinctly different percentages of heavyduty diesel truck traffic are compared. The effects of plume processing on particle number near roadways are shown to be much more profound than on particle mass, further indicting that the adverse health effects observed near roadways are at least partially related to particle numbers. r
Atmospheric Environment, 2006
In-use, fuel-based motor vehicle emission factors were determined using measurements made in a highway tunnel in Pittsburgh, Pennsylvania. Concentrations of PM 2.5 mass, CO, CO 2 , and NO x were measured continuously. Filter-based measurements included PM 2.5 mass, organic and elemental carbon (OC and EC), inorganic ions and metals. Fuel-based emission factors for each pollutant were calculated using a fuel-carbon balance. The weekday traffic volume and fleet composition varied in a consistent diurnal pattern with the estimated fraction of fuel consumed by heavy-duty diesel vehicle (HDDV) traffic ranging from 11% to 36%. The emission rate of most species showed a significant dependence on sample period. NO x , PM 2.5 , EC and OC emission factors were significantly larger during the early morning, truckdominated period. Emissions of particulate metals associated with brake wear (Cu, Sb, Ba and potentially Ga) were emitted at higher rates during the rush-hour period, which is characterized by slower, stop-and-go traffic. Emission rates of crustal elements (Fe, Ca, Mg, Li), Zn and Mn were highest during the early-morning period when there was more heavytruck traffic. A seasonal shift in average OC/EC ratio for the rush-hour period was observed; fall and summer OC/EC ratios are 1.070.6 and 0.2670.06, respectively. Potential causes for this shift are increased partitioning of semi-volatile organic compounds into the gas phase during the summer months and/or effects of seasonal changes in fuel formulation. Emission factors for HDDV and light-duty vehicles (LDV) classes were estimated using a linear regression of emission factor as a function of fleet composition. The extrapolated emission factors generally agree with previously published measurements, though a substantial range in published values is noted. r
Measurements of mobile source particulate emissions in a highway tunnel
International Journal of Vehicle Design, 2001
Recent studies have linked atmospheric fine particulate matter (PM 2.5) with human health effects. In many urban areas, mobile sources are the dominant source of PM 2.5. Dynamometer studies have also implicated diesel engines as being a significant source of ultrafine particles. In order to characterise particulate emissions from in-use vehicles, we performed an onroad study of emissions from vehicles operating in the Tuscarora Mountain Tunnel along the Pennsylvania Turnpike. As part of this study we obtained chemically speciated, size-segregated PM emission rates, particle size distributions, chemically speciated profiles of diesel emissions for use in source apportionment studies, a comparison with years past how much improvement there has actually been in diesel particulate emission rates, and measurements of particulate emission rates from light-duty gasoline vehicles to evaluate the relative significance of this source. This paper describes the experimental methods and presents the preliminary results of the on-road particulate emissions measurements.
Primary particle formation from vehicle emissions during exhaust dilution in the roadside atmosphere
Atmospheric Environment, 2003
Measurements of particle number size distribution in the range 11-452 nm have been made on the side of the busy Marylebone Road in central London over a period from April 1998 to August 2001. The data have been analysed to demonstrate the influences of meteorological factors upon different size fractions and upon the overall size distribution. The relationship to traffic volumes indicates that the accumulation mode particles are associated with emissions from heavy-duty traffic (mainly diesel vehicles) whilst particles in the range 30-60 nm show a stronger association with lightduty traffic. Both of these size fractions show the anticipated dilution effect with increasing wind speed. Particles in the 11-30 nm range behave anomalously showing no clear relationships to traffic volumes and a lesser effect of dilution by increasing wind speed than for the larger particles. Particles in this fraction tend to peak in the early morning showing an inverse association with air temperature. It is concluded that this size range contains freshly nucleated particles formed as the exhaust gases are diluted with ambient air. r
Atmospheric Environment, 2012
Particle emissions from diesel engine cars depend firstly on exhaust aftertreatment systems but the use of the vehicle becomes also crucial. In urban areas, this use depends on: transport demand, route choices, traffic density, street conditions, weather, driver behaviour and topographical characteristics of the roads. Nowadays, most diesel vehicles in urban areas across Europe are equipped with exhaust aftertreatment systems aiming to reduce the total mass of emitted particles. In comparison to earlier aftertreatment systems, the implementation of modern procedures is causing a reduction in the size of the emitted particles up to a nanometric range. The main goal of this work is the characterization of particle size and number distribution in the submicrometric range from a modern diesel vehicle emission in real traffic conditions in the city of Madrid with the purpose of assessing the actual weight of the different city parameters influencing the particle emission. In order to accomplish this objective, up to 12 on board emission measurement experiments have been performed with a Euro IV Diesel passenger car driving along a single urban circuit in Madrid City. To cover the main external factors, stretch, traffic conditions and driving directions have been considered as independent variables for this study. Assuming a proper car operating conditions, the results show that street characteristics, vehicle density and topographic features are the main factors conditioning the particle emission. Extrapolating our results, a diesel standard passenger car circulating across a city like Madrid can emit more nanoparticles per kilometre (up to 114% more in this study) at peak hour than at off peak hour. Moreover, the driving direction can also influence dramatically the emission of nanoparticles per second. This difference in the emission rate depends on the street but in our study it can be higher than 110% depending on the driving direction.
Formation potential of vehicle exhaust nucleation mode particles on-road and in the laboratory
Atmospheric Environment, 2005
A mobile laboratory equipped with gas analysers, a particle number counter and a scanning mobility particle sizer was employed to measure the exhaust particle size distributions of a diesel Euro III passenger car, chasing its exhaust plume on a high-speed track at 50, 100 and 120 km h À1 . Emissions from the same vehicle were also measured in the laboratory under the same driving conditions, using a partial flow sampling system with constant sampling conditions. The vehicle was equipped with an oxidation catalyst and was operated on diesel fuel with 280 ppm wt. sulphur content. Similar results for the exhaust aerosol behaviour were found in both sampling environments, despite the different dilution ratio, sampling temperature and residence time of the aerosol in dilute conditions. A relatively constant soot particle mode was formed in all cases and, in addition, a nucleation mode started to form at 100 km h À1 and became more stable at 120 km h À1 . No nucleation mode was observed at 50 km h À1 road load. The similar behaviour of nucleation mode particles both in the chasing and the laboratory tests indicated that such small volatile particles are a true vehicle emission component and not a dilution artefact. Additional measurements in the laboratory with varying engine load revealed that the nucleation mode formation is sensitive to exhaust gas temperature and its occurrence in increased temperature is repeatable and stable for long sampling times. The findings of this study indicate that nucleation mode particles are an actual emission component of diesel passenger cars and they need to be considered in relevant exhaust aerosol characterization studies. r
Roadside measurements of particulate matter size distribution
Atmospheric Environment, 2003
Roadside measurements were performed in order to document the size distribution of particulate matter (PM) under dilution conditions similar to those found in real world. These activities covered measurements at engine test beds, at different locations in a road tunnel as well as in an urban environment. In order to get a clear picture of the evolution of the PM in different size classes, the in-tunnel locations ranged from curb-side to different locations inside the exhaust air system. Additional measurements were performed in the ambient air at curb-side at a street crossing as well as in urban background.