Monitoring Automotive Particulate Matter Emissions with LiDAR: A Review
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paper_title: Carbon in Black Crusts from the Tower of London

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This paper investigates the origin, fluxes, and transformation of carbon compounds within black crusts on the stone walls of the Tower of London. The crusts were analyzed for elemental and organic carbon, including the water soluble fraction. Elemental carbon and low solubility compounds such as oxalates appeared to be conserved because of long residence times. Conversely, more soluble ions, like chloride and formate would be removed from the layers relatively quickly by rainfall. At higher organic carbon concentrations acetic acid may be produced within the crusts from biological transformations. Currently, traffic sources contribute to increasingly organic rich crusts. The deposition of elemental carbon to buildings darkens surfaces and has important aesthetic implications. The increased organic content may have further aesthetic consequence by changing the color of buildings to warmer tones, particularly browns and yellows. Management of historic buildings requires us to recognize the shift away from simple gypsum crusts to those richer in organic materials.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet Lidar and transmissometer: theory

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An on-road vehicle emissions remote sensing system (VERSS) utilizing an ultraviolet laser (operating at a wavelength of 266 nm) has been developed to quantify the particulate mass in vehicle exhaust. The system simultaneously measures the backscatter and the transmission of the laser light. Obtaining the particulate matter mass concentration from the measurements depends upon a prior laboratory calibration as well as knowledge of the physical, chemical and optical characteristics of the exhaust particles.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet lidar and transmissometer: instrument.

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A novel vehicle emissions remote sensing system (VERSS) for the on-road measurement of fuel-based particulate matter (PM) emission factors is described. This system utilizes two complementary PM channels using an ultraviolet Lidar and transmissometer for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM mass emission factor. The transmissometer directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study, and example data are presented.
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paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

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During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
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paper_title: A case study of optical and chemical ground apportionment for urban aerosols in Thessaloniki

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Abstract Urban aerosol characterization gathering ground-based in situ and sunphotometer measurements have been performed for the city of Thessaloniki for two specific days: the 12th and 13th of June 1997. A representative aerosol model for Thessaloniki aerosols was tentatively constructed for each day. Four components have been selected from our chemical measurements: black carbon (BC), particulate organic matter (POM), inorganic fine water soluble particles (WS) and a residue coarse component which mainly contains coarse dust and sea-salt particles (CC). Size distribution and complex refractive index for (WS) and (CC) components were determined from published data. (CC) has been shown to have a small optical effect compared to the submicron components. Size distribution for carbonaceous particles was obtained from sensitivity tests on particulate number and visible Angstrom exponent. The impact of relative humidity on extinction and scattering coefficients has been calculated on 13 June with Mie theory and Hanel relationships. Parameters needed for this calculation were well known for WS particles only. For POM particles we have used the experimental curve of hygroscopic factors obtained by Hobbs et al. (1997) for urban aerosols sampled on the East coast of United States to determine the hydrophilic dependency of POM particles. Relative humidity has been shown to be an important parameter even for values lower than 50%. Optical apportionment calculation has been realized pointing out that more than 45% of the total extinction coefficient is due to (POM) particles and about 20 and 30% to (WS) and (BC), respectively.
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paper_title: A case study of real-world tailpipe emissions for school buses using a 20% biodiesel blend.

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Numerous laboratory studies report carbon monoxide, hydrocarbon, and particulate matter emission reductions with a slight nitrogen oxides emission increase from engines operating with biodiesel and biodiesel blends as compared to using petroleum diesel. We conducted a field study on a fleet of school buses to evaluate the effects of biodiesel use on gaseous and particulate matter fuel-based emission factors under real-world conditions. The field experiment was carried out in two phases during winter 2004. In January (phase I), emissions from approximately 200 school buses operating on petroleum diesel were measured. Immediately after the end of the first phase measurement period, the buses were switched to a 20% biodiesel blend. Emission factors were measured again in March 2004 (phase II) and compared with the January emission factors. To measure gaseous emission factors we used a commercial gaseous remote sensor. Particulate matter emission factors were determined with a combination of the gaseous remote sensor, a Lidar (light detection and ranging), and transmissometer system developed at the Desert Research Institute of Reno, NV, U.S.A. Particulate matter emissions from school buses significantly increased (up to a factor of 1.8) after the switch from petroleum diesel to a 20% biodiesel blend. The fuel used during this campaign was provided by a local distributor and was independently analyzed at the end of the on-road experiment. The analysis found high concentrations of free glycerin and reduced flash points in the B 100 parent fuel. Both measures indicate improper separation and processing of the biodiesel product during production. The biodiesel fuels used in the school buses were not in compliance with the U.S.A. ASTM D6751 biodiesel standard that was finalized in December of 2001. The U.S.A. National Biodiesel Board has formed a voluntary National Biodiesel Accreditation Program for producers and marketers of biodiesel to ensure product quality and compliance with the ASTM standard. The results of our study underline the importance of the program since potential emission benefits from biodiesel may be reduced or even reversed without appropriate fuel quality control on real-world fuels.
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paper_title: Particle Optics in the Rayleigh Regime

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Abstract Light scattering and absorption by particles suspended in the atmosphere modifies the transfer of solar energy in the atmosphere, thereby influencing global and regional climate change and atmospheric visibility. Of particular interest are the optical properties of particles in the Rayleigh regime, where particles are small compared with the wavelength of the scattered or absorbed light, because these particles experience little gravitational settlement and may have long atmospheric lifetimes. Optical properties of particles in the Rayleigh regime are commonly derived from electromagnetic theory using Maxwell’s equations and appropriate boundary conditions. The size dependence of particle scattering and absorption are derived here from the most basic principles for coherent processes such as Rayleigh scattering (i.e., add amplitudes if in phase) and incoherent processes such as absorption (i.e., add cross sections), at the same time yielding understanding of the upper particle size limit for the ...
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paper_title: CORRELATION BETWEEN AUTOMOTIVE CO, HC, NO, AND PM EMISSION FACTORS FROM ON-ROAD REMOTE SENSING: IMPLICATIONS FOR INSPECTION AND MAINTENANCE PROGRAMS

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Abstract Carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NO) emission factors (EFs) are measured with a commercial vehicle emissions remote sensing system (VERSS) during a large-scale vehicle exhaust emissions study in Las Vegas. Particulate matter (PM) EFs are simultaneously measured for individual vehicles with a newly developed PM-VERSS based on ultraviolet backscatter light detection and ranging (Lidar). The effectiveness of CO and HC EFs as proxy for NO and PM EFs for spark-ignition vehicles is evaluated. Poor correlations were found between EFs for pollutants on an individual vehicle basis indicating that high EFs for one or more pollutants cannot be used as a predictor of high EFs for other pollutants. Stronger functional relationships became evident after averaging the EF data in bins based on rank-order of a single pollutant EF. Low overlap between the highest 10% emitters for CO, HC, NO, and PM was found. These results imply that for an effective reduction of the four pollutants, inspection and maintenance (I/M) programs, including clean screening, should measure all four pollutants individually. Fleet average CO and HC concentrations determined by gaseous VERSS were compared with fleet average CO and HC concentrations measured at low-idle and at high-idle during local I/M tests for spark-ignition vehicles. The fleet average CO concentrations measured by I/M tests at either idle were about half of those measured by remote sensing. The fleet average high-idle HC concentration measured by I/M tests was about half of that measured by VERSS while low-idle I/M and VERSS HC average concentrations were in better agreement. For a typical vehicle trip, most of the fuel is burned during non-idle conditions. I/M measurements collected during idling conditions may not be a good indicator of a vehicle’s potential to be a high emitter. VERSS measurements, when the vehicle is under a load, should more effectively identify high emitting vehicles that have a large contribution to the mobile emissions inventory.
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paper_title: Detection of Gasoline Vehicles with Gross PM Emissions

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Light duty gasoline vehicles (LDGV) are estimated to contribute 40% of the total on-road mobile source tailpipe emissions of particulate matter (PM) in California. While considerable efforts have been made to reduce toxic diesel PM emissions going into the future, less emphasis has been placed on PM from LDGVs. The goals of this work were to characterize a small fleet of visibly smoking and high PM emitting LDGVs, to explore the potential PM-reduction benefits of Smog Check and of repairs, and to examine remote sensing devices (RSD) as a potential method for identifying high PM emitters in the in-use fleet. For this study, we recruited a fleet of eight vehicles covering a spectrum of PM emission levels. PM and criteria pollutant emissions were quantified on a dynamometer and CVS dilution tunnel system over the Unified Cycle using standard methods and real time PM instruments. The vehicles were then tested using RSD equipment over a test track, tested with a standard Smog Check, and tested with a screening device during the Smog Check. The PM emission rates of the visibly smoking vehicles range from 60 to 1718 mg/mi over the UC cycle. The light or invisible smokers had PM emissions ranging from 7 to 25 mg/mi. The smoking vehicles showed particle number rates on the order of 10
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paper_title: Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV.

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A novel light detection and ranging-based remote sensing system was assembled and used to measure mass particulate matter (PM) emissions per unit of fuel burned from in-use on-road vehicles. A commercially available remote sensing system was concurrently used to measure emissions of carbon monoxide (CO), nitrogen oxide (NO) and hydrocarbons (HC). The two systems were used to measure 61,207 gasoline and 1180 diesel powered vehicle emissions in Las Vegas, NV from 4/4/2000 to 5/16/2002. Emission factors were related to vehicle age, weight class and fuel type by matching license IDs to the state registration data. Measurements of vehicle speed and acceleration permitted the analysis of emission factors by vehicle specific power (VSP). Average emission factors were calculated for light-duty (<3863 kg [8500 lbs]) gasoline vehicles (LDGV), light-duty diesel vehicles (LDDV), heavy-duty (>3863 kg [8500 lbs]) gasoline vehicles (HDGV) and heavy-duty diesel vehicles (HDDV). LDDV and HDDV emitted approximately 25 times more PM per mass of fuel than LDGV and HDGV. Sufficient numbers of LDGV were measured to relate VSP with CO, HC and NO emissions. No relationship was observed between PM emissions and VSP. PM emission factors from LDGV increased with vehicle age. Fuel-based emission factors measured by remote sensing were compared with MOBILE6 and PART5 emissions model factors. Good agreement was observed for HC emission factors for vehicles less than 20 years old. MOBILE6 CO emission factors were approximately 2 times greater than measured CO emission factors for vehicles less than 13 years old. Measured NO emission factors were approximately 50% greater than MOBILE6 factors for vehicles 7-15 years old but in good agreement for vehicles less than 7 years old. Measured PM emission factors showed a clear increase with vehicle age, however, PART5 uses only a single PM emission factor for LDGV less than 18 years old. The PM emission factors for the fleet of LDGV, HDGV, LDDV and HDDV were 0.06, 0.05, 1.6 and 1.5 g/kg, respectively.
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paper_title: Aerosol light scattering effect on terrestrial plant productivity and energy fluxes over the eastern United States

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[1] This study reports the first regional-scale assessment of aerosol effects on plant productivity and surface energy fluxes over the eastern United States. Analysis is conducted using an established modeling framework, which is composed of a regional land surface model, regional daily aerosol optical depth (AOD) estimates, and meteorological forcings. The sensitivity experiments were conducted from May to September in 2000 and 2001 over the eastern United States with and without the aerosol light scattering effect. Results show that the aerosol light scattering effect results in enhanced productivity for high-LAI and optimum temperature environments under cloudless-sky conditions around noon, while it results in least productive for low-LAI, low-temperature environments under cloud-sky conditions in early morning or late afternoon. As a result, domain-averaged plant productivities, measured as net primarily production, are changed by −0.71 g C m−2 (−0.09%) in 2000 and +5.00 g C m−2 (+0.5%) in 2001. These responses of plant productivity and photosynthesis to the aerosol light scattering effect uniquely modulate the surface flux as follows. The aerosol light scattering effect reduces the surface downwelling solar radiation (14.9 W m−2 in 2000 and 16.0 W m−2 in 2001) and net radiation in vegetation canopy, but simultaneously increases the photosynthesis and stomatal conductance. Consequently, surface latent heat flux (transpiration and evaporation) is reduced by a small amount particularly over the forests, while aerosol loading often results in larger reduction in the sensible heat flux. For the whole domain, latent heat flux is changed by −3.10 W m−2 (−2.1%) in 2000 and −3.12 W m−2 (−2.1%) in 2001, sensible heat flux is changed by −7.57 W m−2 (−12.9%) in 2000 and −8.36 W m−2 (−11.3%) in 2001, and surface skin temperature is changed by −0.25 K (−0.1%) in 2000 and −0.27 K (−0.1%) in 2001.
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paper_title: Global warming in the twenty-first century: An alternative scenario

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A common view is that the current global warming rate will continue or accelerate. But we argue that rapid warming in recent decades has been driven mainly by non-CO(2) greenhouse gases (GHGs), such as chlorofluorocarbons, CH(4), and N(2)O, not by the products of fossil fuel burning, CO(2) and aerosols, the positive and negative climate forcings of which are partially offsetting. The growth rate of non-CO(2) GHGs has declined in the past decade. If sources of CH(4) and O(3) precursors were reduced in the future, the change in climate forcing by non-CO(2) GHGs in the next 50 years could be near zero. Combined with a reduction of black carbon emissions and plausible success in slowing CO(2) emissions, this reduction of non-CO(2) GHGs could lead to a decline in the rate of global warming, reducing the danger of dramatic climate change. Such a focus on air pollution has practical benefits that unite the interests of developed and developing countries. However, assessment of ongoing and future climate change requires composition-specific long-term global monitoring of aerosol properties.
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paper_title: Aerosol light absorption and its measurement: A review

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Abstract Light absorption by aerosols contributes to solar radiative forcing through absorption of solar radiation and heating of the absorbing aerosol layer. Besides the direct radiative effect, the heating can evaporate clouds and change the atmospheric dynamics. Aerosol light absorption in the atmosphere is dominated by black carbon (BC) with additional, significant contributions from the still poorly understood brown carbon and from mineral dust. Sources of these absorbing aerosols include biomass burning and other combustion processes and dust entrainment. For particles much smaller than the wavelength of incident light, absorption is proportional to the particle volume and mass. Absorption can be calculated with Mie theory for spherical particles and with more complicated numerical methods for other particle shapes. The quantitative measurement of aerosol light absorption is still a challenge. Simple, commonly used filter measurements are prone to measurement artifacts due to particle concentration and modification of particle and filter morphology upon particle deposition, optical interaction of deposited particles and filter medium, and poor angular integration of light scattered by deposited particles. In situ methods measure particle absorption with the particles in their natural suspended state and therefore are not prone to effects related to particle deposition and concentration on filters. Photoacoustic and refractive index-based measurements rely on the heating of particles during light absorption, which, for power-modulated light sources, causes an acoustic signal and modulation of the refractive index in the air surrounding the particles that can be quantified with a microphone and an interferometer, respectively. These methods may suffer from some interference due to light-induced particle evaporation. Laser-induced incandescence also monitors particle heating upon absorption, but heats absorbing particles to much higher temperatures to quantify BC mass from the thermal radiation emitted by the heated particles. Extinction-minus-scattering techniques have limited sensitivity for measuring aerosol light absorption unless the very long absorption paths of cavity ring-down techniques are used. Systematic errors can be dominated by truncation errors in the scattering measurement for large particles or by subtraction errors for high single scattering albedo particles. Remote sensing techniques are essential for global monitoring of aerosol light absorption. While local column-integrated measurements of aerosol light absorption with sun and sky radiometers are routinely done, global satellite measurements are so far largely limited to determining a semi-quantitative UV absorption index.
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paper_title: Light Absorption by Carbonaceous Particles: An Investigative Review

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The optical properties of the light-absorbing, carbonaceous substance often called “soot,” “black carbon,” or “carbon black" have been the subject of some debate. These properties are necessary to model how aerosols affect climate, and our review is targeted specifically for that application. We recommend the term light-absorbing carbon to avoid conflict with operationally based definitions. Absorptive properties depend on molecular form, particularly the size of sp 2-bonded clusters. Freshly-generated particles should be represented as aggregates, and their absorption is like that of particles small relative to the wavelength. Previous compendia have yielded a wide range of values for both refractive indices and absorption cross section. The absorptive properties of light-absorbing carbon are not as variable as is commonly believed. Our tabulation suggests a mass-normalized absorption cross section of 7.5 ± 1.2 m2/g at 550 nm for uncoated particles. We recommend a narrow range of refractive indices for s...
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paper_title: Individual Measurements of the Emission Factor of Aerosol Black Carbon in Automobile Plumes

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As automobiles passed a measuring point, we recorded the concentrations of carbon dioxide and aerosol black carbon (BC) in their dispersing exhaust plumes. After subtraction of background levels, the ratio of the increments of these species allows us to calculate the emission factor of BC per unit mass of fuel from each individual vehicle. These factors spanned a range of greater than two orders of magnitude, representing the emission of from 4 × 10−6 to 10−3 grams of aerosol black carbon per gram of carbon consumed in the fuel. Their distribution showed that 20 percent of the vehicles accounted for 65 percent of the emissions. The real-time measurement methodology allows for a determination of the distribution of emission factors across the actual population of sources. These results are similar to the wide range of carbon monoxide emission factors reported recently.
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paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

paper_content:

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
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paper_title: Analysis of Remote Sensing Errors of Omission and Commission Under FTP Conditions.

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Second-by-second modal emissions data from a 73-vehicle fleet of 1990 and 1991 light duty cars and trucks driven on the Federal Test Procedure (FTP) driving cycle were examined to determine remote sensing errors of commission in identifying high emissions vehicles. Results are combined with a similar analysis of errors of omission based on modal FTP data from high emissions vehicles. Extremely low errors of commission combined with modest errors of omission indicate that remote sensing should be very effective in isolating high CO and HC emitting vehicles in a fleet of late model vehicles on the road.
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paper_title: Real-world automotive emissions: Summary of studies in the Fort McHenry and Tuscarora Mountain tunnels. Final report

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Motor vehicles are the main source of carbon monoxide (CO). Under multiple sponsorship, two major vehicle emissions studies were conducted: one in Fort McHenry tunnel (under the Baltimore Harbor) in June 1992 and the other in the Tuscarora Mountain tunnel in south-central Pennsylvania (Pennsylvania Turnpike) in September 1992. The cars at both sites tended to be newer than elsewhere (median age was < 4 years), and much better maintained as judged by low CO/CO2 ratios and other emissions characteristics. Measured CO/CO2 ratios agreed with concurrent roadside infrared remote sensing measurements on light-duty vehicles. Remote sensing measurements on heavy-duty diesels were obtained for the first time and were roughly in agreement with the regular (bag sampling) tunnel measurements in both CO/CO2 and HC/CO2 ratios.
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paper_title: Source apportionment of diesel and spark ignition exhaust aerosol using on-road data from the minneapolis metropolitan Area

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Abstract Air quality measurements were made on interstate highways in the Minneapolis metropolitan area. Gas and aerosol concentrations were measured on weekdays and weekends. By exploiting the difference in the relative volumes of heavy duty (HD) diesel and light duty (LD) spark ignition (SI) vehicles on weekdays and weekends, we were able to estimate apportioned fuel specific emissions. The on-road, apportioned, fuel specific particle number emissions factors, estimated from condensation particle counter (CPC) measurements were 1.34±0.2×1016 particles kg−1 for diesels and 7.1±1.6×1015 particles kg−1 for spark ignition vehicles. Estimates from the scanning mobility particle sizer (SMPS) measurements were 2.1±0.3×1015 particles kg−1 for diesels and 3.9±0.6×1014 particles kg−1 for SI vehicles. The difference between CPC and SMPS measurements is mainly due to different lower size detection limits of the instruments, ∼3 and ∼10 nm, respectively. On a weekly weighted basis and on weekdays, the majority of particle number was attributed to HD diesel traffic. Weekend production of particles can be primarily attributed to light duty SI automobiles. On a per vehicle basis, HD vehicles produced substantially greater numbers of particles. On a fuel specific basis, HD vehicles produce slightly higher concentrations of particles than light duty vehicles. The relative contribution of LD vehicles to particle number emissions increased as particle size decreased. The HD apportioned size distributions were similar to size distributions measured during other on-road and laboratory studies. The LD apportioned size distribution was bounded by laboratory and on-road size distributions. Our work is representative of summer, highway cruise conditions. It is likely that under cold start and high load operating conditions LD emissions will increase relative to HD emissions.
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paper_title: On-road vehicle emissions: US studies

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Abstract Several recent events in mobile sources emissions measurements have caused a major reassessment of the amounts of volatile organic compounds (VOC) and carbon monoxide (CO) in the ambient air attributed to mobile sources. These include the comparison of real-world in-use vehicle emissions with those predicted by mobile emission factor models and the development of cross-road remote sensors for measuring emissions from in-use passing vehicles. The real-world measurements were generally higher than model predictions. A tunnel study in the Southern California Air Quality Study (SCAQS) found two-fold to seven-fold differences. Additional real-world studies, including the remote sensor, roadside I/M inspections and testing on the US Environmental Protection Agency portable dynamometer have shown that 50% of the tailpipe emissions come from only 10% of the vehicles and 80% come from 20% of the vehicles. This paper describes the portable dynamometer study and several tunnel studies.
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paper_title: On-road measurement of vehicle tailpipe emissions using a portable instrument.

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A study design procedure was developed and demonstrated for the deployment of portable onboard tailpipe emissions measurement systems for selected highway vehicles fueled by gasoline and E85 (a blend of 85% ethanol and 15% gasoline). Data collection, screening, processing, and analysis protocols were developed to assure data quality and to provide insights regarding quantification of real-world intravehicle variability in hot-stabilized emissions. Onboard systems provide representative real-world emissions measurements; however, onboard field studies are challenged by the observable but uncontrollable nature of traffic flow and ambient conditions. By characterizing intravehicle variability based on repeated data collection runs with the same driver/vehicle/route combinations, this study establishes the ability to develop stable modal emissions rates for idle, acceleration, cruise, and deceleration even in the face of uncontrollable external factors. For example, a consistent finding is that average emissions during acceleration are typically 5 times greater than during idle for hydrocarbons and carbon dioxide and 10 times greater for nitric oxide and carbon monoxide. A statistical method for comparing on-road emissions of different drivers is presented. Onboard data demonstrate the importance of accounting for the episodic nature of real-world emissions to help develop appropriate traffic and air quality management strategies.
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paper_title: Method comparisons of vehicle emissions measurements in the Fort McHenry and Tuscarora Mountain Tunnels

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Abstract Experiments were conducted in the Fort McHenry Tunnel in Baltimore, MD, and in the Tuscarora Mountain Tunnel in Pennsylvania, during the summer of 1992 to evaluate real-world automotive emissions. Included in these experiments were the first reported measurements of individual vehicle exhaust in tunnels by a remote sensing device (RSD). Results are compared to integrated emission measurements carried out by analysis of concurrent collections of tunnel air into bags, canisters, and adsorbent traps and by conventional Fourier transform infrared (FTIR) spectroscopy. The vehicles using these highway tunnels proved to be lower emitting than vehicles usually measured by remote sensing in urban areas. At Fort McHenry the RSD-measured CO CO 2 ratios were, on average, high compared to either the bag or FTIR measurements (by a factor of 1.4 ± 0.2) for the four runs monitored. RSD hydrocarbon data were obtained only at the uphill location ( + 3.76% grade). RSD HC CO 2 ratios were lower on average, but statistically indistinguishable when compared with either the FTIR or the integrated uphill measurements. At Tuscarora, the RSD-measured CO CO 2 ratios were in agreement with the CO CO 2 ratios in the tunnel bag measurements and FTIR measurements (within a factor of 1.00 ± 0.16 by one method and 0.82 ± 0.32 by a second, when traffic was dominated by light-duty spark-ignition vehicles). The RSD HC CO 2 ratios were, however, higher than the light-duty vehicle estimates from the integrated (bag/canister/Tenax) tunnel measurements by a factor of 3, and higher than the FTIR Δ HC Δ CO 2 ratios by an even higher factor, mostly owing to water vapor interferences in the low average RSD measurements. For the first time RSD measurements were collected from a small sample of heavy-duty diesels; comparisons to the heavy-duty emissions contributions for CO and HC were favorable. Analysis of emissions data for vehicle variability at Fort McHenry revealed that low CO emitting vehicles tended to be consistently low but that the minority that were high emitters ( > 2.5% CO) were more likely to be high only at the uphill location. Vehicle mileage information was collected at a toll booth in the case of Fort McHenry and at a service plaza in the case of Tuscarora for comparison against the RSD emissions measurements. This comparison showed little conventional deterioration of CO or HC emissions with mileage. The trend consisted of an increased frequency of high emitters with mileage, rather than an increase in emissions from all vehicles with increasing mileage.
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paper_title: Analysis of heavy-duty diesel truck activity and emissions data

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Abstract Despite their relatively small population, heavy-duty diesel vehicles (HDDVs) are (in 2005) disproportionate contributors to the emissions inventory for oxides of nitrogen (NOx) and particulate matter (PM) due to their high individual vehicle emissions rates, lack of engine aftertreatment, and high vehicle miles traveled. Beginning in the early 1990s, heavy-duty engine manufacturers began equipping their engines with electronic sensors and controls and on-board electronic computer modules (ECMs) to manage these systems. These ECMs can collect and store both periodic and lifetime engine operation data for a variety of engine and vehicle parameters including engine speed and load, time at idle, average vehicle speed, etc. The University of California, Riverside (UCR), under a contract with the California Air Resources Board (CARB), performed data analysis of 270 ECM data sets obtained from the CARB. The results from this analysis have provided insights into engine/vehicle operation that have not been obtained from previous on-board datalogger studies since those previous studies focused on vehicle operation and did not collect engine operating data. Results indicate that HDDVs spend a considerable amount of time at high-speed cruise and at idle and that a smaller percentage of time is spent under transient engine/vehicle operation. These results are consistent with other HDDV activity studies, and provide further proof of the validity of assumptions in CARB's emission factor (EMFAC2002) model. An additional important contribution of this paper is that the evaluation of vehicle ECM data provides several advantages over traditional global positioning system (GPS) and datalogger studies: (1) ECM data is significantly cheaper than the traditional method ($50 record–1 vs. ∼$2000 record–1) and (2) ECM data covers vehicle operation over the entire life of the vehicle, whereas traditional surveys cover only short periods of surveillance (days, weeks, or months). It is worthwhile to note that this work was not intended to compare the various methods of data collection but to provide additional empirical support for the EMFAC2002 model and to explore the utility of this unique low-cost form of data collection and analysis.
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paper_title: A Decade of On-road Emissions Measurements

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A multiyear, on-road emission measurement program carried out in the cities of Chicago, Illinois; Denver, Colorado; Los Angeles (LA), California; and Phoenix, Arizona shows large, fuel-specific tailpipe emissions reductions at all of the sites for carbon monoxide (CO), hydrocarbons (HC), and nitric oxide (NO). CO emissions decreased between 56% (Denver) and 71% (Chicago), HC emissions decrease between 27% (Phoenix) and 63% (Denver), and NO emissions have dropped between 48% (West LA) and 68% (Chicago). Three observed factors common to all of the sites are that the emission reductions are occurring in vehicles of all ages, that the influence of engine load on fuel-specific emissions, especially for CO and NO, is reduced and that fleet-averaged emission deterioration is near zero for model years newer than 2001 and older than 1990. These nationwide data sets imply that the majority of these on-road emissions reductions are the result of continued improvements in function and durability of vehicle emission c...
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paper_title: ENHANCEMENTS OF REMOTE SENSING FOR VEHICLE EMISSIONS IN TUNNELS

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The University of Denver in cooperation with the Desert Research Institute, EPA, and General Motors Corporation have successfully adapted the University of Denver's remote sensing system for vehicle exhaust to the measurement of vehicle emissions in a tunnel environment. Two studies conducted at the Fort McHenry Tunnel in Baltimore, MD and the Tuscarora Mountain Tunnel located west of Harrisburg, PA on the Pennsylvania Turnpike are described. The difficulties associated with remote sensing in a tunnel environment have led to a number of improvements in the remote sensing technology. Due to logistics and restrictions on placement of equipment in the Fort McHenry tunnel, a prototype periscope system was employed to optimize the height of the remote sensor's infrared beam path relative to vehicle exhaust plumes. At the Tuscarora Tunnel, first-time measurements of dual lane traffic were conducted using a single source and detector and two cameras for vehicle identification. This precluded the normal practice of directing traffic into a single lane which can alter normal drivng patterns.
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paper_title: Emissions from lit-use Motor Vehicles in Los Angeles: A Pilot Study of Remote Sensing and the Inspection and Maintenance Program

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As part of a major field study to understand the causes of persistent, elevated carbon monoxide pollution episodes in Los Angeles, we performed a project to understand the emissions of vehicles in use. In this experiment, we assessed the accuracy of a remote sensing instrument designed to measure CO concentrations from vehicles as they were driven on the road. The remote sensor was shown to be accurate within ten percent of the directly measured tailpipe value. We performed a roadside inspection on 60 vehicles and demonstrated that the remote sensor could be used as an effective surveillance tool to identify high CO-emitting vehicles. We also compared the roadside data set to the biennial Smog Check (I/M) tests for the same vehicles, and observed that carbon monoxide and exhaust hydrocarbons from high emitters were much higher than when the vehicles received their routine inspection. Furthermore, for the high-emitting vehicles in this data set, the length of time since the biennial Smog Check had little i...
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paper_title: AUTOMOBILE CARBON MONOXIDE EMISSION

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An examination was made of all the programs currently in place in the state of Colorado that purport to control mobile source carbon monoxide (CO) emissions. These include Inspection and Maintenance, Oxygenated Fuels, and a Better Air Campaign featuring voluntary no-drive days. This article discusses why these programs don't work as well as was hoped, or as well as their proponents claim. Although several of the currently proposed Clean Air Act amendments fulfill the need to "do something" politically, they may not achieve the desired CO reduction goals either.
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paper_title: A hydrocarbon detector for the remote sensing of vehicle exhaust emissions

paper_content:

A new remote sensor for measuring on‐road carbon monoxide, carbon dioxide, and hydrocarbon exhaust emissions in under 1 s from vehicles passing the sensor is described. The new design adds the capability for measuring exhaust hydrocarbons and eliminates the need for liquid–nitrogen‐cooled detectors while improving upon the overall signal to noise. Under typical field operating conditions, sensitivity to 0.05% propane with a precision of 0.014% propane is observed. Two types of water interferences important to the measurement of exhaust hydrocarbons are reported. The water vapor present in all auto exhaust causes a small positive bias dependent on the analytical wavelength chosen. A much larger interference is caused by liquid water (often called ‘‘steam’’) plumes seen behind cold vehicles at low temperatures.
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paper_title: A tunable diode laser system for the remote sensing of on-road vehicle emissions

paper_content:

O, and NO2 emissions have been measured with this instrument. The system is also capable of measuring CO, NH3, H2CO, CH3OH, and other small molecules in vehicle exhaust.
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paper_title: Remote Sensing of In-Use Heavy-Duty Diesel Trucks

paper_content:

On-road measurements in 2005 of carbon monoxide (CO), hydrocarbons, nitric oxide, nitrogen dioxide, and sulfur dioxide from 1641 individually identified heavy-duty diesel trucks at two locations in Colorado are reported. Carbon monoxide and nitric oxide show increasing emissions with increased altitude. Oxides of nitrogen (NOx) emissions have decreased with more recent model years over the last 10 years but are the same as vehicles that are 20 years old. At the Golden, CO site, there was a statistically significant decrease in fleet emissions of CO and NOx since a similar study in 1999. There was no emission trend for CO or NOx with gross vehicle weight or odometer in units of grams of pollutant per kilogram of fuel consumed. Data from this study suggest that on-road remote sensing can detect illegal, high sulfur fuel use from individual heavy-duty diesel trucks. Ammonia emissions from this study were below the detection limit of the instrument but will be useful as a baseline value for future comparison.
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paper_title: Nitrogen dioxide, sulfur dioxide, and ammonia detector for remote sensing of vehicle emissions

paper_content:

A remote sensor for measuring on-road vehicles passing the sensor in real time is described. This sensor expands upon previous technology that measured carbon monoxide, carbon dioxide, and exhaust hydrocarbons in the IR and nitric oxide in the UV. The design adds the capability to measure nitrogen dioxide in the UV with one spectrometer and to measure SO2 and NH3 along with NO in a second UV spectrometer. With these units operating side by side, the major mobile source precursors to secondary aerosol production can be measured simultaneously and in real time. Detection limits for NO2, SO2, and NH3 are 1.2, 0.72, and 0.78 g pollutant per kilogram of fuel, respectively.
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paper_title: An Experimental Evaluation of Remote Sensing-Based Hydrocarbon Measurements: A Comparison to FID Measurements.

paper_content:

The purpose of this study was to intercompare hydrocarbon (HC) measurements performed by a number of different instruments: a gas chromatograph (GC), a flame ionization detector (FID), a fourier transform infrared spectrometer (FTIR), a commercially produced non-dispersive infrared analyzer (NDIR), and two remote sensors. These instruments were used to measure total HC concentrations in a variety of samples, including (1) ten different individual HC species, (2) 12 different vehicle exhaust samples, and (3) three different volatilized fuel samples. The 12 exhaust samples were generated by operating two different vehicles on a dynamometer. Each vehicle was operated at different times with three different fuels. The vehicles were operated fuel rich, i.e., with low air/fuel ratios to encourage elevated exhaust HC levels. Some of the exhaust samples were obtained while operating each vehicle at a stoichiometric air/fuel ratio with one spark plug wire disconnected. To quantify the degree to which the various instruments agreed with the FID, a parameter called the response factor was used, where the response factor was defined as the HC/CO2 ratio measured by each instrument divided by the HC/CO2 ratio measured by the dynamometer bench. Of the various instruments, only the GC yielded response factors that were consistently at or close to one. The other instruments typically had values at or below one. For the ten individual HC species studied, the NDIR and remote sensors obtained response factors between 0.05 and 1.0, with the highest response factors being obtained for the alkanes and the lowest response factors obtained for toluene and ethylene. For the exhaust samples, the NDIR and remote sensors obtained response factors between 0.23 and 0.68. For raw fuel samples, the response factors were between 0.44 and 0.68. NDIR and remote sensor measurements correlated very poorly with total HC in exhaust.
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paper_title: Method comparisons of vehicle emissions measurements in the Fort McHenry and Tuscarora Mountain Tunnels

paper_content:

Abstract Experiments were conducted in the Fort McHenry Tunnel in Baltimore, MD, and in the Tuscarora Mountain Tunnel in Pennsylvania, during the summer of 1992 to evaluate real-world automotive emissions. Included in these experiments were the first reported measurements of individual vehicle exhaust in tunnels by a remote sensing device (RSD). Results are compared to integrated emission measurements carried out by analysis of concurrent collections of tunnel air into bags, canisters, and adsorbent traps and by conventional Fourier transform infrared (FTIR) spectroscopy. The vehicles using these highway tunnels proved to be lower emitting than vehicles usually measured by remote sensing in urban areas. At Fort McHenry the RSD-measured CO CO 2 ratios were, on average, high compared to either the bag or FTIR measurements (by a factor of 1.4 ± 0.2) for the four runs monitored. RSD hydrocarbon data were obtained only at the uphill location ( + 3.76% grade). RSD HC CO 2 ratios were lower on average, but statistically indistinguishable when compared with either the FTIR or the integrated uphill measurements. At Tuscarora, the RSD-measured CO CO 2 ratios were in agreement with the CO CO 2 ratios in the tunnel bag measurements and FTIR measurements (within a factor of 1.00 ± 0.16 by one method and 0.82 ± 0.32 by a second, when traffic was dominated by light-duty spark-ignition vehicles). The RSD HC CO 2 ratios were, however, higher than the light-duty vehicle estimates from the integrated (bag/canister/Tenax) tunnel measurements by a factor of 3, and higher than the FTIR Δ HC Δ CO 2 ratios by an even higher factor, mostly owing to water vapor interferences in the low average RSD measurements. For the first time RSD measurements were collected from a small sample of heavy-duty diesels; comparisons to the heavy-duty emissions contributions for CO and HC were favorable. Analysis of emissions data for vehicle variability at Fort McHenry revealed that low CO emitting vehicles tended to be consistently low but that the minority that were high emitters ( > 2.5% CO) were more likely to be high only at the uphill location. Vehicle mileage information was collected at a toll booth in the case of Fort McHenry and at a service plaza in the case of Tuscarora for comparison against the RSD emissions measurements. This comparison showed little conventional deterioration of CO or HC emissions with mileage. The trend consisted of an increased frequency of high emitters with mileage, rather than an increase in emissions from all vehicles with increasing mileage.
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paper_title: On-Road Evaluation of Inspection/Maintenance Effectiveness

paper_content:

This study presents an evaluation of inspection and maintenance (I/M) programs in terms of their effect on motor vehicle carbon monoxide (CO) and hydrocarbon (HC) exhaust emissions as measured on-road by remote sensing technology. The results show that the performance of past I/M programs at several monitored locations has been less effective than predicted by the U.S. Environmental Protection Agency. The emissions from I/M and non-I/M vehicles measured in Tucson, AZ, and in rural Colorado show no statistically significant difference. An apparent I/M effect observed in El Paso, TX, and in Denver, CO, is smaller than predicted. Comparisons of CO emissions by vehicle age for several years at the same locations in Chicago and Denver show no evidence that the Chicago centralized I/M program was more effective than the Denver decentralized I/M program.
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paper_title: REMOTE SENSING OF VEHICLE EXHAUST EMISSIONS

paper_content:

We will briefly discuss vehicle emissions and the vehicle emissions inventory before reviewing remote-sensing technology for exhaust emissions and remote-sensing applications that help characterize and minimize exhaust emissions in the real world. Remote sensing is the only method available that can measure the HC and CO exhaust emission rates of large numbers of individual in-use vehicles. These measurements have helped focus attention on the problem of in-use emissions from malfunctioning and illegally altered vehicles. The method has a bright future as an aid in understanding in-use emissions, a monitor of progress in reducing fleet emission rates, and as an IM and enforcement tool. 11 refs., 2 figs.
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paper_title: Remote sensing of ammonia and sulfur dioxide from on-road light duty vehicles.

paper_content:

This study reports the largest data set of on-road, fuel-based mass emissions of ammonia and sulfur dioxide from vehicles of known make, model year, and fuel type. Ammonia is the first pollutant observed for which the emissions decrease with increasing fleet age from 10 to 20 years. The fixed nitrogen emission ratio is 15.0% by mass and 24.7% by mole, larger than current models predict. Diesel fueled vehicles emit more SO2 than gasoline, and unexpectedly, gasoline SO2 emissions decrease continuously with newer model year vehicles.
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paper_title: Characterization of on-road vehicle NO emissions by a TILDAS remote sensor

paper_content:

A tunable infrared laser differential absorption spectrometer (TILDAS) was used to remotely sense the nitric oxide (NO) emissions from 1,473 on-road vehicles. The real-world measurement precision of this instrument in the limit of low NO concentration is 5 ppm of the vehicle exhaust, which corresponds to a 3o detection limit of 15 ppm. Our analysis of the distribution of negative concentration measurements produced during this experiment supports this claim, showing that the instrumental noise for this set of measurements was at most 8 ppm in the limit of low NO concentration. The high sensitivity of this instrument allowed us to measure the NO emissions of even the cleanest vehicles. The measured vehicle fleet NO emissions closely fit a gamma distribution with 10% of the fleet contributing about 50% of the total fleet emissions. Newer vehicles had lower NO emissions than older ones, but high NO emitters were found in every vehicle age cohort. On a vehicle-by-vehicle basis, NO emissions correlated very weakly with vehicle velocity, acceleration, power per unit mass, carbon monoxide (CO) emissions, and hydrocarbon (HC) emissions. High NO emitting vehicles could not be identified by remote sensing of CO or HC emissions and vice versa. When we compared the NO emissions for 117 vehicles measured more than one time, about half of the high NO emitters were found to be very consistent, while the other half varied significantly.
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paper_title: Comparison of auto emission measurement techniques

paper_content:

Abstract The Clark and Washoe Remote Sensing Study (CAWRSS) field season took place in September 1994. The study was designed to characterize the exhaust emissions of the on-road vehicle fleet in the two major urban centers of the State of Nevada. The air quality in Las Vegas (Clark County) and Reno (Washoe County) is significantly worse than the surrounding rural areas and vehicle emissions have been identified as one of the primary sources of the pollution. Inspection and maintenance programs, mandated by the federal government, have been implemented in both urban areas. The study compated the State-approved test, a no-load, two-speed idle test, to two other measurement techniques: remote sensing devices (RSDs) and the IM240 test, a loaded-mode test run on a dynamometer. Results were viewed from two different perspectives. Fleet-wide characteristics showed that concentrations of CO (%) measured with RSDs were higher than those obtained with the no-load idle tests. Characteristics of pollution distributions derived from the two techniques were similar in range and shape. Observations for individual vehicles were then compared. CAWRSS is in agreement with earlier studies in that high emitters in the idle test are also high emitters on-road.
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paper_title: Development of a High-Speed Ultraviolet Spectrometer for Remote Sensing of Mobile Source Nitric Oxide Emissions.

paper_content:

The University of Denver (DU) has developed a new remote sensor for the measurement of mobile source nitric oxide (NO). This system is integrated with an existing infrared remote sensor and is capable of measuring carbon monoxide and hydrocarbons in addition to NO, at a rate of more than 1000 vehicles/hr. The detection limit on a low-emitting vehicle under typical measurement conditions is 24 parts per million NO (3σ). Measurements from this instrument correlated well in a side-by-side comparison with the previous NO remote sensor developed at DU, and we have used this study to confirm a suspected interference by aromatic hydrocarbons in the older instrument. The results of an extended field experiment using the new instrument, conducted in fall 1997, are also presented. The NO emissions of the fleet measured in this study (averaging 15.0 g NO/gal) exhibit a skewed distribution typical of mobile sources. This paper also describes the relationship between NO emissions and model year and NO emissions and vehicle acceleration, as measured by the new remote sensor.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet lidar and transmissometer: instrument.

paper_content:

A novel vehicle emissions remote sensing system (VERSS) for the on-road measurement of fuel-based particulate matter (PM) emission factors is described. This system utilizes two complementary PM channels using an ultraviolet Lidar and transmissometer for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM mass emission factor. The transmissometer directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study, and example data are presented.
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paper_title: Aerosol light scattering effect on terrestrial plant productivity and energy fluxes over the eastern United States

paper_content:

[1] This study reports the first regional-scale assessment of aerosol effects on plant productivity and surface energy fluxes over the eastern United States. Analysis is conducted using an established modeling framework, which is composed of a regional land surface model, regional daily aerosol optical depth (AOD) estimates, and meteorological forcings. The sensitivity experiments were conducted from May to September in 2000 and 2001 over the eastern United States with and without the aerosol light scattering effect. Results show that the aerosol light scattering effect results in enhanced productivity for high-LAI and optimum temperature environments under cloudless-sky conditions around noon, while it results in least productive for low-LAI, low-temperature environments under cloud-sky conditions in early morning or late afternoon. As a result, domain-averaged plant productivities, measured as net primarily production, are changed by −0.71 g C m−2 (−0.09%) in 2000 and +5.00 g C m−2 (+0.5%) in 2001. These responses of plant productivity and photosynthesis to the aerosol light scattering effect uniquely modulate the surface flux as follows. The aerosol light scattering effect reduces the surface downwelling solar radiation (14.9 W m−2 in 2000 and 16.0 W m−2 in 2001) and net radiation in vegetation canopy, but simultaneously increases the photosynthesis and stomatal conductance. Consequently, surface latent heat flux (transpiration and evaporation) is reduced by a small amount particularly over the forests, while aerosol loading often results in larger reduction in the sensible heat flux. For the whole domain, latent heat flux is changed by −3.10 W m−2 (−2.1%) in 2000 and −3.12 W m−2 (−2.1%) in 2001, sensible heat flux is changed by −7.57 W m−2 (−12.9%) in 2000 and −8.36 W m−2 (−11.3%) in 2001, and surface skin temperature is changed by −0.25 K (−0.1%) in 2000 and −0.27 K (−0.1%) in 2001.
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paper_title: Feasibility of remote sensing of particulate emissions from heavy-duty vehicles

paper_content:

A portable remote sensing system capable of real-time detection of particulate emissions from heavy-duty vehicles is being developed. The remote sensing technique employs optical extinction to measure the concentration of the carbonaceous fraction of the particulate matter and the CO{sub 2} in the exhaust plumes from individual vehicles. From these two measurements, instantaneous emission indices giving the mass of soot emitted to the amount of fuel burned by the vehicle at the given operating condition can be computed. Two tests designed to characterize the accuracy of the technique were conducted: (1) measurements through an exhaust plume from a laboratory diesel using a sequence of steady-state operating conditions; and (2) measurements of transient emissions from full size diesel-powered buses whose emissions were simultaneously measured in a full-scale dilution tunnel. In both cases, the remote sensing measurements were in good agreement with those obtained by conventional methods. Applications to actual on-road measurements are also discussed.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet lidar and transmissometer: instrument.

paper_content:

A novel vehicle emissions remote sensing system (VERSS) for the on-road measurement of fuel-based particulate matter (PM) emission factors is described. This system utilizes two complementary PM channels using an ultraviolet Lidar and transmissometer for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM mass emission factor. The transmissometer directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study, and example data are presented.
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paper_title: Intensity-modulated, stepped frequency cw lidar for distributed aerosol and hard target measurements

paper_content:

A compact frequency-modulated, continuous wave (FM-cw) lidar system for measurement of distributed aerosol plumes and hard targets is presented. The system is based on intensity modulation of a laser diode and quadrature detection of the return signals. The advantages of using laser diode amplitude modulation and quadrature detection is a large reduction in the hardware required for processing and storing return signals as well as the availability of off-the-shelf integrated electronic components from the wireless and telecommunication communities. Equations to invert the quadrature signal components and determine spatial distributions of multiple targets are derived. Spatial scattering intensities are used to extract aerosol backscatter coefficients, which can then be directly compared to microphysics aerosol models for environmental measurements. Finally, results from laboratory measurements with a monostatic FM-cw lidar system with both hard targets and aerosols are discussed.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet Lidar and transmissometer: theory

paper_content:

An on-road vehicle emissions remote sensing system (VERSS) utilizing an ultraviolet laser (operating at a wavelength of 266 nm) has been developed to quantify the particulate mass in vehicle exhaust. The system simultaneously measures the backscatter and the transmission of the laser light. Obtaining the particulate matter mass concentration from the measurements depends upon a prior laboratory calibration as well as knowledge of the physical, chemical and optical characteristics of the exhaust particles.
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paper_title: Aerosol light absorption and its measurement: A review

paper_content:

Abstract Light absorption by aerosols contributes to solar radiative forcing through absorption of solar radiation and heating of the absorbing aerosol layer. Besides the direct radiative effect, the heating can evaporate clouds and change the atmospheric dynamics. Aerosol light absorption in the atmosphere is dominated by black carbon (BC) with additional, significant contributions from the still poorly understood brown carbon and from mineral dust. Sources of these absorbing aerosols include biomass burning and other combustion processes and dust entrainment. For particles much smaller than the wavelength of incident light, absorption is proportional to the particle volume and mass. Absorption can be calculated with Mie theory for spherical particles and with more complicated numerical methods for other particle shapes. The quantitative measurement of aerosol light absorption is still a challenge. Simple, commonly used filter measurements are prone to measurement artifacts due to particle concentration and modification of particle and filter morphology upon particle deposition, optical interaction of deposited particles and filter medium, and poor angular integration of light scattered by deposited particles. In situ methods measure particle absorption with the particles in their natural suspended state and therefore are not prone to effects related to particle deposition and concentration on filters. Photoacoustic and refractive index-based measurements rely on the heating of particles during light absorption, which, for power-modulated light sources, causes an acoustic signal and modulation of the refractive index in the air surrounding the particles that can be quantified with a microphone and an interferometer, respectively. These methods may suffer from some interference due to light-induced particle evaporation. Laser-induced incandescence also monitors particle heating upon absorption, but heats absorbing particles to much higher temperatures to quantify BC mass from the thermal radiation emitted by the heated particles. Extinction-minus-scattering techniques have limited sensitivity for measuring aerosol light absorption unless the very long absorption paths of cavity ring-down techniques are used. Systematic errors can be dominated by truncation errors in the scattering measurement for large particles or by subtraction errors for high single scattering albedo particles. Remote sensing techniques are essential for global monitoring of aerosol light absorption. While local column-integrated measurements of aerosol light absorption with sun and sky radiometers are routinely done, global satellite measurements are so far largely limited to determining a semi-quantitative UV absorption index.
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paper_title: Feasibility of remote sensing of particulate emissions from heavy-duty vehicles

paper_content:

A portable remote sensing system capable of real-time detection of particulate emissions from heavy-duty vehicles is being developed. The remote sensing technique employs optical extinction to measure the concentration of the carbonaceous fraction of the particulate matter and the CO{sub 2} in the exhaust plumes from individual vehicles. From these two measurements, instantaneous emission indices giving the mass of soot emitted to the amount of fuel burned by the vehicle at the given operating condition can be computed. Two tests designed to characterize the accuracy of the technique were conducted: (1) measurements through an exhaust plume from a laboratory diesel using a sequence of steady-state operating conditions; and (2) measurements of transient emissions from full size diesel-powered buses whose emissions were simultaneously measured in a full-scale dilution tunnel. In both cases, the remote sensing measurements were in good agreement with those obtained by conventional methods. Applications to actual on-road measurements are also discussed.
---
paper_title: Development of a High-Speed Ultraviolet Spectrometer for Remote Sensing of Mobile Source Nitric Oxide Emissions.

paper_content:

The University of Denver (DU) has developed a new remote sensor for the measurement of mobile source nitric oxide (NO). This system is integrated with an existing infrared remote sensor and is capable of measuring carbon monoxide and hydrocarbons in addition to NO, at a rate of more than 1000 vehicles/hr. The detection limit on a low-emitting vehicle under typical measurement conditions is 24 parts per million NO (3σ). Measurements from this instrument correlated well in a side-by-side comparison with the previous NO remote sensor developed at DU, and we have used this study to confirm a suspected interference by aromatic hydrocarbons in the older instrument. The results of an extended field experiment using the new instrument, conducted in fall 1997, are also presented. The NO emissions of the fleet measured in this study (averaging 15.0 g NO/gal) exhibit a skewed distribution typical of mobile sources. This paper also describes the relationship between NO emissions and model year and NO emissions and vehicle acceleration, as measured by the new remote sensor.
---
paper_title: On-road measurement of automotive particle emissions by ultraviolet lidar and transmissometer: instrument.

paper_content:

A novel vehicle emissions remote sensing system (VERSS) for the on-road measurement of fuel-based particulate matter (PM) emission factors is described. This system utilizes two complementary PM channels using an ultraviolet Lidar and transmissometer for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM mass emission factor. The transmissometer directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study, and example data are presented.
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paper_title: Laser Remote Sensing: Fundamentals and Applications

paper_content:

Electromagnetic Theory of Radiation. Quantum Physics and Radiation Processes. Interaction and Propagation of Radiation. Laser Fundamentals. Laser Systems as Remote Sensors. Laser-Remote-Sensor Equations. Analysis and Interpretation of the Lidar Return Signals. Atmospheric Lidar Applications. Hydrographic Lidar Applications. Concluding Remarks. Index.
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paper_title: New approach for aerosol profiling with a lidar onboard an ultralight aircraft: application to the African Monsoon Multidisciplinary Analysis.

paper_content:

A new airborne instrumental payload has been designed for an ultralight aircraft to determine the vertical profile of aerosol optical properties. It is based on Lidar Aérosols UltraViolet Aéroporté (LAUVA), a compact backscattering lidar system emitting at the wavelength of 355 nm. We operated this airborne configuration in the Sahel from the city of Niamey (Niger) during the first campaign of the African Monsoon Multidisciplinary Analysis (AMMA) in January-February 2006, when aerosols from both soil dust and savannah fires cause large visibility reductions. We take advantage of the lidar capability of pointing in different directions for retrieving the vertical profile of the aerosol backscatter to extinction ratio (BER). A synergy with a scatterometer (880 nm) and a ground-based sunphotometer allows us to further determine the vertical profile of Angström exponent (a). We identify three types of aerosol layers up to about 5 km below the free troposphere, dominated by biomass burning (BB) particles, mineral dust (D) particles, and a mixing between BB and D particles, respectively, associated with BER (a) values close to 0.008 sr(-1) (1.5), 0.025 sr(-1) (0), and 0.015 sr(-1) (0.4-1).
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paper_title: Influence of the photomultiplier tube spatial uniformity on lidar signals.

paper_content:

Measurements of the spatial uniformity of Hamamatsu H5783-06 photosensor modules were performed by the flying spot method. The results were used to simulate the influence of the photomultiplier tube on a lidar signal. A simple method for improving the spatial uniformity is proposed.
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paper_title: Transmission as an input boundary value for an analytical solution of a single-scatter lidar equation.

paper_content:

Single-scatter lidar signals carry information on the spatial atmospheric backscatter coefficient, attenuated by the path-integrated extinction. Assuming that the relationship between the backscatter and the extinction is known, the inverted extinction profile and the path-integrated extinction are uniquely related to the input boundary value. The integrated extinction over a certain range interval is a measure of the optical transmission along that path. In reverse, for a given transmission over the path of interest, the input boundary value is uniquely defined. An analytical expression is derived that describes the input boundary condition for the inversion of the single-scatter lidar equation in terms of the transmission losses over the path of interest. The proposed method is useful in situations in which independent transmission measurements are carried out or in situations in which targets such as multiple cloud layers or beam stops are available in the lidar path. Equations for both the forward and the backward integration method are presented. Compared with the widely accepted inversion schemes that are based on single-point reference extinction values, the proposed method is less sensitive to noise.
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paper_title: Pulse mode saturation properties of photomultiplier tubes.

paper_content:

The response of an RCA-4522 photomultiplier tube (35ET bialkali photocathode, 14 dynode stages) in the saturation region has been studied as a function of ambient background light intensity, photocathode illumination area, magnetic field orientation, and ambient temperature. These studies were made using various high-speed pulsed light sources. It is found that the phototube's response does vary with some of these parameters (in particular, photocathode temperature effects). However, its response is reproducible and highly successful operation in this region is possible through a series of calibrations.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet lidar and transmissometer: instrument.

paper_content:

A novel vehicle emissions remote sensing system (VERSS) for the on-road measurement of fuel-based particulate matter (PM) emission factors is described. This system utilizes two complementary PM channels using an ultraviolet Lidar and transmissometer for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM mass emission factor. The transmissometer directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study, and example data are presented.
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paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

paper_content:

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
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paper_title: Measuring the Emissions of Passing Cars

paper_content:

Here, in situ sensing of the emissions from motor vehicles is reviewed. The role of thermodynamics, chemical reaction kinetics, stoichiometry of reactions, heat transfer, and fluid flow are considered. 27 refs., 5 figs.
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paper_title: On-road measurement of automotive particle emissions by ultraviolet Lidar and transmissometer: theory

paper_content:

An on-road vehicle emissions remote sensing system (VERSS) utilizing an ultraviolet laser (operating at a wavelength of 266 nm) has been developed to quantify the particulate mass in vehicle exhaust. The system simultaneously measures the backscatter and the transmission of the laser light. Obtaining the particulate matter mass concentration from the measurements depends upon a prior laboratory calibration as well as knowledge of the physical, chemical and optical characteristics of the exhaust particles.
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paper_title: Individual Measurements of the Emission Factor of Aerosol Black Carbon in Automobile Plumes

paper_content:

As automobiles passed a measuring point, we recorded the concentrations of carbon dioxide and aerosol black carbon (BC) in their dispersing exhaust plumes. After subtraction of background levels, the ratio of the increments of these species allows us to calculate the emission factor of BC per unit mass of fuel from each individual vehicle. These factors spanned a range of greater than two orders of magnitude, representing the emission of from 4 × 10−6 to 10−3 grams of aerosol black carbon per gram of carbon consumed in the fuel. Their distribution showed that 20 percent of the vehicles accounted for 65 percent of the emissions. The real-time measurement methodology allows for a determination of the distribution of emission factors across the actual population of sources. These results are similar to the wide range of carbon monoxide emission factors reported recently.
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paper_title: Submicrometer and supermicrometer particulate emission from spark ignition vehicles

paper_content:

Abstract: Particulate emissions from 11 gasoline powered and 2 liquefied petroleum (LPG) powered passenger vehicles were characterised during the Accelerated Simulation Mode driving cycles on a chassis dynamometer. The test fleet consisted of 10 catalyst-equipped vehicles operated with unleaded gasoline (5 Ford Falcons and 5 Holden Commodores), 2 LPG powered vehicles (both Ford Falcons), and 1 older type noncatalyst vehicle operated with leaded gasoline. Particulate characterisation included determination of total particulate number concentration and size distribution using the Scanning Mobility Particle Sizer (SMPS) and the Aerodynamic Particle Sizer (APS). The average particle number concentrations in the SMPS range for all modes was lower for Ford Falcons and somewhat higher for Commodores, with values of 1.5x104 and 4.1x104 cm-3, respectively. This difference is significant and was observed for all modes. The number concentration levels were higher for the LPG fuelled cars (8.4x104 cm-3) and for the leaded gasoline powered vehicle (7.9x105 cm-3). There was not a significant variation in particle count median diameter in the SMPS and the APS ranges, either for different operating conditions of the vehicles investigated, or between different vehicle groups. The observed size distributions were bimodal with average values of CMD ranged from 39.1 to 60.2nm in the SMPS range and from 0.9 to 1.4µm in the APS range. The results obtained from this study can be used as a first order estimation towards emission inventories for vehicle groups included in the investigations.
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paper_title: Characterization of Particles from a Current Technology Heavy-Duty Diesel Engine

paper_content:

The physical properties, chemical properties, and morphology of particles from a current technology diesel engine run under steady-state conditions were determined during five campaigns across three calendar years. Concentrations of particulate matter, NOx, HC, CO, and CO2 measured at a fixed sampling position were found to be repeatable between different campaigns. However, particle size distributions and number concentrations were significantly affected by dilution conditions. Particle density, estimated using a volume size distribution estimated from an ELPI together with measured mass, was found to be below 1 g/cm3 at nonzero loads, but this is explained by an overestimation of volume by the ELPI due to particle fractal properties. Particle phase SO42-, NO3-, PAH, organic carbon, and elemental carbon were found to vary with engine operating modes. Particles emitted from a modern diesel engine had similar cluster structures to those from old engines but consisted of smaller basic particles when analyze...
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paper_title: Size distribution characteristics of elemental carbon emitted from Chinese vehicles: results of a tunnel study and atmospheric implications.

paper_content:

The size distribution characteristics of elemental carbon (EC) emissions from Chinese vehicles have not been previously described. In this study, we collected size-segregated aerosol samples using a 10-stage MOUDI sampler (0.056-18 microm) in the Zhujiang tunnel, a roadway tunnel in the urban area of Guangzhou, China. The samples were analyzed for EC, organic carbon (OC), and inorganic ions. Fine particles had an OC/EC ratio of 0.57, indicating a dominant contribution of EC from diesel vehicles. Both EC and OC showed a dominant accumulation mode with a mass median aerodynamic diameter (MMAD) of 0.42 microm. In comparison, studies available in the literature typically reported a much lower MMAD for EC (approximately 0.1 microm) in vehicular emissions in North America. A theoretical analysis indicated that the larger EC particles observed in this study could not have resulted from after-emission growth processes (i.e., water accretion, coagulation, and vapor condensation). This leaves operating conditions such as high engine loads and low combustion efficiencies, which are more prevalent in diesel-fueled Chinese vehicles, as a more plausible inherent reason for producing the larger EC agglomerates. While fresh 0.1 microm EC particles are unlikely to act as cloud condensation nuclei (CCN), calculations showed that EC particles as large as 0.42 microm are effective CCN at atmospherically relevant critical supersaturation values of less than 1%. As a result, fresh EC particles from Chinese vehicle emissions could readily undergo cloud processing and form internal mixtures with sulfate in the residue droplet mode particles. This prediction is consistent with observations that EC frequently showed a dominant droplet mode in urban atmospheres in this region. The internal mixing of EC with highly hygroscopic sulfate would facilitate its removal by wet deposition and shorten its lifetime in the atmosphere. In addition, the light-absorbing capabilities of EC particles could also be enhanced due to their internal mixing with sulfate. Numerical aerosol models need to take these factors into consideration for better predictions of the behaviors and effects of urban aerosols in China.
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paper_title: Number size distribution of particulate emissions of heavy-duty engines in real world test cycles

paper_content:

Abstract Five in-service engines in heavy-duty trucks complying with Euro II emission standards were measured on a dynamic engine test bench at EMPA. The particulate matter (PM) emissions of these engines were investigated by number and mass measurements. The mass of the total PM was evaluated using the standard gravimetric measurement method, the total number concentration and the number size distribution were measured by a Condensation Particle Counter (lower particle size cut-off: 7 nm) and an Electrical Low Pressure Impactor (lower particle size: 32 nm), respectively. The transient test cycles used represent either driving behaviour on the road (real-world test cycles) or a type approval procedure. They are characterised by the cycle power, the average cycle power and by a parameter for the cycle dynamics. In addition, the particle number size distribution was determined at two steady-state operating modes of the engine using a Scanning Mobility Particle Sizer. For quality control, each measurement was repeated at least three times under controlled conditions. It was found that the number size distributions as well as the total number concentration of emitted particles could be measured with a good repeatability. Total number concentration was between 9×1011 and 1×1013 particles/s (3×1013–7×1014 p/kWh) and mass concentration was between 0.09 and 0.48 g/kWh. For all transient cycles, the number mean diameter of the distributions lay typically at about 120 nm for aerodynamic particle diameter and did not vary significantly. In general, the various particle measurement devices used reveal the same trends in particle emissions. We looked at the correlation between specific gravimetric mass emission (PM) and total particle number concentration. The correlation tends to be influenced more by the different engines than by the test cycles.
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paper_title: Characterization of Submicron Exhaust Particles from Engines Operating Without Load on Diesel and JP-8 Fuels

paper_content:

Diluted exhaust from a selection of Air Force ground support vehicles was subjected to gravimetric, carbon, and size distribution analyses in September 1999. The vehicles operated on diesel and JP-8 fuels. In most cases, the engines involved were similar to civilian counterparts. The tests involved "low" and "high" idle settings but no external loads were imposed. Particle size distribution data, obtained over the 10 to 352 nanometer diameter range using an SMPS instrument, showed that the relative number count of accumulation mode particles increased with respect to nucleation mode particles as the engine rpm increased. The SMPS distributions often explained the main variations in the integrated PM 2.5 gravimetric mass data. Particulate mass derived from the SMPS data and from cascade impactor measurements were well correlated (regression slope 1.02). Empirically determined "elemental" carbon (EC) and "organic" carbon (OC) were the main constituents of the PM 2.5 gravimetric mass (regression slope 0.89)....
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paper_title: Size Distributions of Motor Vehicle Exhaust PM: A Comparison Between ELPI and SMPS Measurements

paper_content:

Particle size measurements using the electrical low pressure impactor (ELPI) and scanning mobility particle sizer (SMPS) are compared from the perspective of characterizing the particulate matter in motor vehicle exhaust. Both steady state vehicle operation and transient drive cycles are considered, and both gasoline and diesel fueled vehicle emissions are compared. Although the ELPI and SMPS measure different physical properties, respectively, the aerodynamic diameter and mobility diameter, the steady state particle size distributions are in close agreement, except for the 37 nm impactor stage of the ELPI which may overestimate particle number by up to a factor of two relative to the SMPS. This has little effect on the volume, or mass, weighted distribution. These, too, are generally in good agreement, though discrepancies appear at large particle size due to multiple charging effects in the SMPS and to electrometer offsets and the small particle loss correction in the ELPI. Selecting particles based on ...
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paper_title: Effects of Exhaust System Components on Particulate Morphology in a Light-duty Diesel Engine

paper_content:

The detailed morphological properties of diesel particulate matter were analyzed along the exhaust system at various engine operating conditions (in a range of 1000 - 2500 rpm and 10 - 75 % loads of maximum torques). A 1.7-L turbocharged light-duty diesel engine was powered with California low-sulfur diesel fuel injected by a common-rail injection system, of which particulate emissions were controlled by an exhaust gas recirculation (EGR) system and two oxidation catalysts. A unique thermophoretic sampling system first developed for internal combustion engine research, a high-resolution transmission electron microscope (TEM), and a customized image processing/data acquisition system were key instruments that were used for the collection of particulate matter, subsequent imaging of particle morphology, and detailed analysis of particle dimensions and fractal geometry, respectively. The data analysis showed that the average primary particle sizes significantly changed in a range of approximately 15 nm to 30 nm as a function of engine operating condition, while overall decreasing along the exhaust pipe. Aggregate particle sizes also significantly changed in a range of approximately 50 nm to 100 nm, in terms of radius of gyration, through the entire engine operating conditions. These particle sizes were affected mainly by the oxidation catalysts and tail pipe as well as engine operating conditions. Particle geometry was changed along the exhaust pipe, most significantly by the first catalyst, while overall becoming more spherical in shape toward the tail pipe. Fractal dimensions were measured in a range of approximately 1.4 to 1.8 through the entire engine operating conditions, which identified the change of particle geometry. A distinct increase of fractal dimension appeared after the first catalyst. The spherical particle shape, represented by the larger fractal dimension, was justified by soot morphology observed at the sample collected immediately after the catalyst.
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paper_title: Size and Composition Distribution of Fine Particulate Matter Emitted from Motor Vehicles

paper_content:

A dilution source sampling system is augmented to measure the size-distributed chemical composition of fine particle emissions from motor vehicles. Measurements are made using an optical particle counter (OPC), a differential mobility analyzer (DMA)/condensation nucleus counter (CNC) combination, and a pair of microorifice uniform deposit impactors (MOUDIs). The sources tested with this system include catalyst-equipped gasoline-powered light-duty vehicles, noncatalyst gasoline-powered light-duty vehicles, and medium-duty diesel trucks. Chemical composition analysis demonstrates that particles emitted from the gasoline-powered vehicles tested are largely composed of organic compounds while particles emitted from diesel engines contain roughly equal amounts of organic compounds and elemental carbon. The particle mass distributions from all mobile sources tested have a single mode that peaks at approximately 0.1−0.2 μm particle diameter. Of the two diesel vehicles tested, the vehicle with the lowest fine particle emissions rate released the largest number of ultrafine particles, a finding similar to that of Bagley et al. (Characterization of fuel and aftertreatment device effects on diesel emissions; Technical Report 76; Health Effects Institute: Cambridge, MA, 1996). Particle size distribution measurements taken throughout the FTP urban driving cycle used to test all of the vehicles described in this paper reveal that particulate mass emission rates and particulate size distributions from the vehicles tested here are similar during the cold start and hot start segments of the driving cycle.
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paper_title: EFFECT OF ENGINE LOAD ON DIESEL SOOT PARTICLES

paper_content:

This study concentrates on characterization of nonvolatile fraction of diesel particles. These particles have an impact on earth's radiation balance as well as on health effects of vehicle emissions. In addition to composition and size distribution of particles, an important factor affecting their health effects and properties and lifetimes in the atmosphere is their morphology. The effect of engine parameters on soot particle size distributions and also on particle morphology has been studied. It was found that the shape of the size distribution and also the structure of diesel particles depend on engine load. The number distributions were found to obey log-normal assumption. The width of the distribution increased with increasing engine load. The geometric standard deviations of measured distributions varied from 1.7 to 2.1. Simultaneously, the fractal dimension of particles decreased with increasing engine load. The values for mass fractal dimensions based on scaling of particle mass and mobility size ...
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paper_title: Influence of diesel engine combustion parameters on primary soot particle diameter.

paper_content:

Effects of engine operating parameters and fuel composition on both primary soot particle diameter and particle number size distribution in the exhaust of a direct-injected heavy-duty diesel engine were studied in detail. An electrostatic sampler was developed to deposit particles directly on transmission electron microscopy (TEM) grids. Using TEM, the projected area equivalent diameter of primary soot particles was determined. A scanning mobility particle sizer (SMPS) was used for the measurement of the particle number size distribution. Variations in the main engine operating parameters (fuel injection system, air management, and fuel properties) were made to investigate soot formation and oxidation processes. Primary soot particle diameters determined by TEM measurements ranged from 17.5 to 32.5 nm for the diesel fuel and from 24.1 to 27.2 nm for the water-diesel emulsion fuel depending on the engine settings. For constant fuel energy flow rate, the primary particle size from the water-diesel emulsion fuel was slightly larger than that from the diesel fuel. A reduction in primary soot particle diameter was registered when increasing the fuel injection pressure (IP) or advancing the start of injection (SOI). Larger primary soot particle diameters were measured while the engine was operating with exhaust gas recirculation (EGR). Heat release rate analysis of the combustion process revealed that the primary soot particle diameter decreased when the maximum flame temperature increased for the diesel fuel.
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paper_title: Individual Measurements of the Emission Factor of Aerosol Black Carbon in Automobile Plumes

paper_content:

As automobiles passed a measuring point, we recorded the concentrations of carbon dioxide and aerosol black carbon (BC) in their dispersing exhaust plumes. After subtraction of background levels, the ratio of the increments of these species allows us to calculate the emission factor of BC per unit mass of fuel from each individual vehicle. These factors spanned a range of greater than two orders of magnitude, representing the emission of from 4 × 10−6 to 10−3 grams of aerosol black carbon per gram of carbon consumed in the fuel. Their distribution showed that 20 percent of the vehicles accounted for 65 percent of the emissions. The real-time measurement methodology allows for a determination of the distribution of emission factors across the actual population of sources. These results are similar to the wide range of carbon monoxide emission factors reported recently.
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paper_title: EFFECTS OF WATER CONDENSATION AND EVAPORATION ON DIESEL CHAIN-AGGLOMERATE MORPHOLOGY

paper_content:

Abstract Diesel engines emit chain-agglomerate particles that can serve as cloud condensation nuclei. This research uses an Environment Scanning Electron Microscope (ESEM) to study the effect of cloud processing on morphologies of individual diesel chain-agglomerates. Particles produced using a Caterpillar 3304 diesel engine from fuels with sulfur contents of 0.84%, 0.32% and 0.034% by weight were collected on silicon wafer substrates. They were subjected to one to three water condensation-evaporation cycles in the ESEM. This process was recorded on video tape, and digitized images of individual particles were used to find the particle's fractal dimension before and after each condensation-evaporation cycle. Significant collapse occurred in particles generated from both the mid-range sulfur fuel (0.32% S) and the low sulfur fuel (0.034% S). The average fractal dimension of the particle images increased from 1.56 to 1.76 and from 1.40 to 1.54 for particles from low and mid-range sulfur fuel, respectively. We observed no significant morphological change in particles from high sulfur fuels. The experiments reflect lower limits for the degree of collapse that diesel chain-agglomerate particles undergo during atmospheric cloud processing.
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paper_title: Morphological investigation of the microstructure, dimensions, and fractal geometry of diesel particulates

paper_content:

The microstructure, dimensions, and fractal geometry of diesel particulates were investigated through morphological observations. A thermophoretic particle-sampling system was developed to collect diesel particulates directly from the high-temperature exhaust stream of a 75 hp single-cylinder direct-injection diesel engine at various engine operating conditions. The morphology of the collected diesel particulates was analyzed using a high-resolution transmission electron microscope and subsequent image processing/data acquisition system. The analysis revealed that spherical prinary particles were agglomerated together to form large aggregate clusters at most engine operating conditions. The particles produced at low loading conditions displayed amorphous structures, possibly containing a significant amount of soluble organic fraction, while the soot sample at high engine load conditions mostly exhibited graphitic structures. Measured primary particle sizes ranged from 34.4 to 28.5 nm at various engine operating conditions. The smaller primary particles observed at high engine load conditions were caused by oxidation at the encountered high temperatures. A number of small and irregularly shaped particles were captured at these conditions, which identified the existence of apparent particle oxidation. Engine-speed-dependent experiments were also performed to investigate the effects of the residence time of soot particles on particle growth. A growth mechanism of diesel particulates was suggested through analyses for fractal geometry of the cluster particles.
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paper_title: SUBMICROMETER AND SUPERMICROMETER PARTICLES FROM DIESEL VEHICLE EMISSIONS

paper_content:

There is growing evidence that fine airborne particulates could play the most important role in determining health effects. The aim of this work was to investigate the number concentration and size distributions of particulates in the exhausts of diesel vehicles (mainly buses) of different ages and make, operating under different loads. Particle-sizing instruments used were the Scanning Mobility Particle Sizer (SMPS) and Aerodynamic Particle Sizer (APS). The average particle number concentration of the exhausts was in the range (0.7−3.9) × 107 cm-3 in the SMPS range (0.0075−0.304 μm) and (0.3−32) × 103 cm-3 in the APS range (0.5−30 μm). In most cases, particle number concentrations increased with the increased power output from the engine and, in both SMPS and APS ranges, varied significantly within each group of vehicles, but the differences between the groups were small. For individual vehicles, there was no relation between emissions in the smaller and larger particle ranges. Emission characteristics d...
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paper_title: Size and Composition Distributions of Particulate Matter Emissions: Part 2-Heavy-Duty Diesel Vehicles

paper_content:

Abstract Particulate matter (PM) emissions from heavy-duty diesel vehicles (HDDVs) were collected using a chassis dynamometer/dilution sampling system that employed filter-based samplers, cascade impactors, and scanning mobility particle size (SMPS) measurements. Four diesel vehicles with different engine and emission control technologies were tested using the California Air Resources Board Heavy Heavy-Duty Diesel Truck (HHDDT) 5 mode driving cycle. Vehicles were tested using a simulated inertial weight of either 56,000 or 66,000 lb. Exhaust particles were then analyzed for total carbon, elemental carbon (EC), organic matter (OM), and water-soluble ions. HDDV fine (≤1.8 μm aerodynamic diameter; PM1.8) and ultra fine (0.056–0.1 μm aerodynamic diameter; PM0.1) PM emission rates ranged from 181–581 mg/km and 25–72 mg/km, respectively, with the highest emission rates in both size fractions associated with the oldest vehicle tested. Older diesel vehicles produced fine and ultrafine exhaust particles with highe...
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paper_title: Emissions from the laboratory combustion of wildland fuels : Particle morphology and size

paper_content:

[1] The morphology of particles emitted by wildland fires contributes to their physical and chemical properties but is rarely determined. As part of a study at the USFS Fire Sciences Laboratory (FSL) investigating properties of particulate matter emitted by fires, we studied the size, morphology, and microstructure of particles emitted from the combustion of eight different wildland fuels (i.e., sagebrush, poplar wood, ponderosa pine wood, ponderosa pine needles, white pine needles, tundra cores, and two grasses) by scanning electron microscopy. Six of these fuels were dry, while two fuels, namely the tundra cores and one of the grasses, had high fuel moisture content. The particle images were analyzed for their density and textural fractal dimensions, their monomer and agglomerate number size distributions, and three different shape descriptors, namely aspect ratio, root form factor, and roundness. The particles were also probed with energy dispersive X-ray spectroscopy confirming their carbonaceous nature. The density fractal dimension of the agglomerates was determined using two different techniques, one taking into account the three-dimensional nature of the particles, yielding values between 1.67 and 1.83, the other taking into account only the two-dimensional orientation, yielding values between 1.68 and 1.74. The textural fractal dimension that describes the roughness of the boundary of the two-dimensional projection of the particle was between 1.10 and 1.19. The maximum length of agglomerates was proportional to a power a of their diameter and the proportionality constant and the three shape descriptors were parameterized as function of the exponent a.
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paper_title: Structural and Fractal Properties of Particles Emitted from Spark Ignition Engines

paper_content:

Size, morphology, and microstructure of particles emitted from one light-duty passenger vehicle (Buick Century; model year 1990; PM (particulate matter) mass emission rate 3.1 mg/km) and two light-duty trucks (Chevrolet C2; model year 1973; PM mass emission rate 282 mg/km, and Chevrolet El Camino; model year 1976; PM mass emission rate 31 mg/km), running California's unified driving cycles (UDC) on a chassis dynamometer, were studied using scanning electron microscopy (SEM). SEM images yielded particle properties including three-dimensional density fractal dimensions, monomer and agglomerate number size distributions, and three different shape descriptors, namely aspect ratio, root form factor, and roundness. The density fractal dimension of the particles was between 1.7 and 1.78, while the number size distribution of the particles placed the majority of the particles in the accumulation mode (0.1−0.3 μm). The shape descriptors were found to decrease with increasing particle size. Partial melting of parti...
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paper_title: Light Absorption by Carbonaceous Particles: An Investigative Review

paper_content:

The optical properties of the light-absorbing, carbonaceous substance often called “soot,” “black carbon,” or “carbon black" have been the subject of some debate. These properties are necessary to model how aerosols affect climate, and our review is targeted specifically for that application. We recommend the term light-absorbing carbon to avoid conflict with operationally based definitions. Absorptive properties depend on molecular form, particularly the size of sp 2-bonded clusters. Freshly-generated particles should be represented as aggregates, and their absorption is like that of particles small relative to the wavelength. Previous compendia have yielded a wide range of values for both refractive indices and absorption cross section. The absorptive properties of light-absorbing carbon are not as variable as is commonly believed. Our tabulation suggests a mass-normalized absorption cross section of 7.5 ± 1.2 m2/g at 550 nm for uncoated particles. We recommend a narrow range of refractive indices for s...
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paper_title: Particle size distribution from a modern heavy duty diesel engine

paper_content:

Abstract The particle size distribution emitted from a modern heavy duty diesel engine was investigated. It was found that the operation of the engine test bed system, primary and secondary dilution system and instruments were stable and that particle size distributions could be measured repeatedly under specific conditions. The particle size distribution was determined at different engine speed and load. The mode in the number distribution was smaller than 25 nm at engine speed 1600 rev./min and between 40–60 nm at 2600 rev./min. Good agreement of size distributions measured by SMPS and ELPI instruments was found in the region of overlap, and with measurements made with an electron microscope and image analyser. Total particle volume concentrations calculated from SMPS and ELPI data agreed well with those estimated from filter mass data. The measured particle size distribution and total number concentration changes with the dilution conditions and humidity of dilution air. The mechanism is being investigated and preliminary results suggest that sulphuric acid is involved in homogeneous nucleation of new particles during the dilution process.
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paper_title: Signature size distributions for diesel and gasoline engine exhaust particulate matter

paper_content:

Abstract The size distributions of diesel exhaust particulate matter measured from a large number of vehicles and test engines, using a variety of diesel fuels, collapse onto a single characteristic lognormal distribution, when normalized by total particle number and plotted against a scaled diameter. Distinctly different characteristic distributions are observed for direct injection and for port injection gasoline vehicles. These signature distributions are compared to numerically calculated self-preserving size distributions which incorporate fractal dimensions ⩽3 to describe the dendritic nature of soot. However, the coagulation models alone are incapable of reproducing the observed characteristic distributions; compared to the diesel engine data they are conspicuously asymmetric and too steep on the large particle diameter side of the distribution. We discuss the possibility that soot oxidation also plays a role in determining the shape of the characteristic distributions, and the possibility that these signatures could be utilized to distinguish soot emissions from other aerosols.
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paper_title: Morphological investigation of the microstructure, dimensions, and fractal geometry of diesel particulates

paper_content:

The microstructure, dimensions, and fractal geometry of diesel particulates were investigated through morphological observations. A thermophoretic particle-sampling system was developed to collect diesel particulates directly from the high-temperature exhaust stream of a 75 hp single-cylinder direct-injection diesel engine at various engine operating conditions. The morphology of the collected diesel particulates was analyzed using a high-resolution transmission electron microscope and subsequent image processing/data acquisition system. The analysis revealed that spherical prinary particles were agglomerated together to form large aggregate clusters at most engine operating conditions. The particles produced at low loading conditions displayed amorphous structures, possibly containing a significant amount of soluble organic fraction, while the soot sample at high engine load conditions mostly exhibited graphitic structures. Measured primary particle sizes ranged from 34.4 to 28.5 nm at various engine operating conditions. The smaller primary particles observed at high engine load conditions were caused by oxidation at the encountered high temperatures. A number of small and irregularly shaped particles were captured at these conditions, which identified the existence of apparent particle oxidation. Engine-speed-dependent experiments were also performed to investigate the effects of the residence time of soot particles on particle growth. A growth mechanism of diesel particulates was suggested through analyses for fractal geometry of the cluster particles.
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paper_title: Transmission electron microscopical and aerosol dynamical characterization of soot aerosols

paper_content:

Abstract Size, morphology and microstructure of Palas soot, Diesel soot and of Diesel soot/ammonium sulfate mixtures were studied by transmission electron microscopy (TEM). The diameter of the primary particles derived from TEM is 6.6±1.7 nm for Palas soot and 22.6±6.0 nm for Diesel soot. Palas soot predominantly consists of amorphous carbon. In a few cases, nanocrystalline graphite with domain sizes on the order of 1 nm were observed. Primary particles of Diesel soot always show an onion-shell structure of nanocrystalline graphite with domain sizes between 2– 3 nm . Fractal properties of 37 Diesel soot agglomerates were determined from TEM images by two different techniques. The average fractal dimension of Diesel soot derived from TEM is 1.70±0.13. TEM further showed that the initially external mixture of Diesel soot and ammonium sulfate developed with time in a significant degree of internal mixing. A second independent approach to determine the fractal properties of soot is based on computer simulations of the aerosol dynamics. A good reproduction of the time evolution of mass and number concentrations and of the mobility size distribution was achieved. The primary particle diameters obtained from the computer simulations ( 7.3±0.8 nm for Palas soot, 25±3 nm for Diesel soot) are in excellent agreement with the TEM results. The fractal dimension of Diesel soot received from the COSIMA algorithm of 1.9±0.2 (overlap of primary particles was taken into consideration) is consistent with the value obtained from TEM image analysis. For Palas soot, the computer simulation yielded a fractal dimension of 2.0±0.1 (overlap was not corrected, as the overlap coefficient is not known).
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paper_title: Lidar and Balloon-Borne Cascade Impactor Measurements of Aerosols: A Case Study

paper_content:

Aerosol size distributions, elemental components, complex refractive indices, extinction profiles and extinction-to-backscatter ratios have been measured and inferred from balloon-borne cascade impactor and lidar observations made during a cooperative joint experiment conducted during the period 4–10 April, 1980 in Tucson, AZ. Size distributions obtained from quartz crystal microbalance (QCM) cascade impactor measurements at different heights (1 to 1000 m) and times over a period of several days were fairly similar in form, being clearly bimodal in their mass distributions with the coarse particle mode being dominant. Electron microscope and energy dispersive X-ray analyses of particles deposited on the QCM stages over the particle radii range ∼0.5–4.0 μm revealed that the particle samples were elementally dominated by both sulfur and crustal type (Al, Ca, Mg and Si) elements. Complex refractive index estimates for a wavelength of 649 nm were obtained by comparing the lidar inferred aerosol extinction-to-...
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paper_title: Elastic Lidar: Theory, Practice, and Analysis Methods

paper_content:

Preface. Definitions. 1. Atmospheric Properties. 1.1 Atmospheric Structure. 1.2 Atmospheric Properties. 2. Light Propagation in the Atmosphere. 2.1 Light Extinction and Transmittance. 2.2 Total and Directional Elastic Scattering of the Light Bean. 2.3 Light Scattering by Molecules and Particulates: Inelastic Scattering. 2.4 Light Absorption by Molecules and Particulates. 3. Fundamentals of the Lidar Technique. 3.1 Introduction to the Lidar Technique. 3.2 Lidar Equation and Its Constituents. 3.3 Elastic Lidar Hardware. 3.4 Practical Lidar Issues. 3.5 Eye Safety Issues and Hardware. 4. Detectors, Digitizers, Electronics. 4.1 Detectors. 4.2 Electric Circuits for Optical Detectors. 4.3 A-D Converters/Digitizers. 4.4 General. 5. Analytical Solutions of the Lidar Equation. 5.1 Simple Lidar-Equation Solution for a Homogene ous. 5.2 Basic Transformation of the Elastic Lidar Equation. 5.3 Lidar Equation Solution for a Single-Component Heterogeneous Atmosphere. 5.4 Lidar Equation Solution for a Two-Component Atmosphere. 5.5 Which Solution is Best? 6. Uncertainty Estimation for Lidar Measurements. 6.1 Uncertainty for the Slope Method. 6.2 Lidar Measurement Uncertainty in a Two-Component Atmosphere. 6.3 Background Constituent in the Original Lidar Signal and Lidar Signal Averaging. 7. Backscatter-to-Extinction Ratio. 7.1 Exploration of the Backscatter-to-Extinction Ratio on the Inversion Result. 7.2 Influence of Uncertainty in the Backscatter-to-Extinction Ratio. 8. Lidar Examination of Clear and Moderately Turbid Atmospheres. 8.1 One-Directional Lidar Measurements: Methods and Problems. 8.2 Inversion Techniques for a "Spotted" Atmosphere. 9. Multiangle Methods for Extinction Coefficient Determination. 9.1 Angle-Dependent Lidar Equation and Its Basic Solution. 9.2 Solution for the Layer-Integrated Form of the Angle-Dependent Lidar Equation. 9.3 Solution for the Two-Angle layer-Integrated Form of the Lidar Equation. 9.4 Two-Angle Solution for the Angle-Independent Lidar Equation. 9.5 High-Altitude Tropospheric Measurements with Lidar. 9.6 Which Method Us the Best? 10. Differential Absorption Lidar Technique (DIAL). 10.1 DIAL Processing Technique: Fundamentals. 10.2 DIAL Processing Technique: Problems. 10.3 Other Techniques for DIAL Data Processing. 11. Hardware Solutions to the Inversion Problem. 11.1 Use of N2 Raman Scattering for Extinction Measurement. 11.2 Resolution of Particulate and Molecular Scattering by Filtration. 11.3 Multiple-Wavelength Lidars. 12. Atmospheric Parameters from Elastic Lidar Data. 12.1 Visual Range in Horizontal Directions. 12.2 Visual Range in Slant Directions. 12.3 Temperature measurements. 12.4 Boundary Layer Height Determination. 12.5 Cloud Boundary Determination. 13. Wind Measurement Methods from Elastic Lidar Data. 13.1 Correlation Methods to Determine Wind Speed and Direction. 13.2 Edge Technique. 13.3 Fringe Imaging Technique. 13.4 Kinetic Energy, Dissipation Rate, and Divergence. Bibliography. Index.
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paper_title: Particulate Emission Rates for Unpaved Shoulders along a Paved Road

paper_content:

ABSTRACT This paper reports the first empirical estimate of particle emissions from unpaved shoulders along paved roads.1 Its objectives are to develop and demonstrate an emission rate measurement methodology that can be applied in different areas; identify the mechanisms that suspend dust from unpaved shoulders and the observables related to this suspension process; and quantify PM10 mass emissions in the form of an emission rate. To achieve these objectives, fast-response observations from nephelometers and a sonic anemometer were used to characterize shortlived dust plumes generated by passing vehicles. In addition, detailed soil surface measurements determined the mechanical properties of the shoulder surfaces. Large traffic-induced turbulence events that led to significant dust entrainment were almost exclusively caused by “large” vehicles such as trucks, semis, and vehicles pulling trailers, all traveling 50-65 mph. PM10 emission rates for these large, fast-traveling vehicles were determined to be 8...
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paper_title: One‐year observations of particle lidar ratio over the tropical Indian Ocean with Raman lidar

paper_content:

Observations of the extinction-to-backscatter ratio (lidar ratio) of South and Southeast Asian aerosol particles are presented for the wavelength of 532nm. Raman lidar measurements were performed in the Maldives (4.1° N, 73.3° E) in the framework of the Indian Ocean Experiment (INDOEX) in 1999/2000. These observations in the tropics are an important contribution to a growing global lidar-ratio climatology which is needed for an improved determination of the particle optical depth with ground-based and spaceborne lidars. The lidar ratio was found to be a useful quantity to trace back different pollution sources and to identify less and considerably light-absorbing particles. During the winter/spring seasons heavily polluted air from India and Southeast Asia was advected to the lidar site. Under these conditions lidar ratios up to 110sr were observed in the lofted pollution plumes above 1000m height. According to backward trajectories the highest lidar ratios were found for airmasses which crossed the eastern and northeastern parts of India. Large lidar ratios >70sr indicate small, considerably absorbing aerosol particles. Below 1000m height, the lidar ratio typically ranged from 30-60sr. The marine boundary layer contained a mixture of marine and anthropogenic particles. Under clean, marine conditions in October 1999, lidar ratios <30sr were found.
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paper_title: Testing Re-entrained Aerosol Kinetic Emissions from Roads : a new approach to infer silt loading on roadways

paper_content:

Abstract PM10 and PM2.5 emissions from roadways are currently estimated using the silt loading on the road surface as a surrogate for the emissions potential of road dust. While the United States Environmental Protection Agency prescribes this method in AP-42, there is considerable cost associated with silt loading measurements; it is feasible to sample only a small portion of a roadway network. A new approach for measuring the concentration of suspendable PM10 above road surfaces has been developed to obtain a more spatially representative estimate of a road's potential to emit dust. The Testing Re-entrained Aerosols Kinetic Emissions from Roads (TRAKER) system uses real-time aerosol sensors mounted on a vehicle to measure the concentration of dust suspended from the road while the vehicle is in motion. When coupled with a Global Positioning System (GPS) instrument, TRAKER can be used to efficiently survey the changes in suspendable particles due to varying road conditions over a large spatial domain. In a recent study on paved roads in Las Vegas, the TRAKER system was compared with collocated silt loading measurements. The TRAKER system was also used to survey the relative amounts of suspendable road dust on approximately 300 miles of paved roads. The system provides a unique perspective on road dust sources and their spatial distribution. Results of this study indicated that the difference of the PM10 concentrations measured behind the tire and on the hood is exponentially related to vehicle speed. This was an interesting finding because current AP-42 road dust emissions estimation methods do not include vehicle speed as a factor in the emissions calculations. The experiment also demonstrated that the distribution of suspendable material on roadways is highly variable and that a large number of samples are needed to represent road dust emissions potential on an urban scale for a variety of road and activity conditions.
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paper_title: The Extinction-to-Backscatter Ratio of Tropospheric Aerosol: A Numerical Study

paper_content:

Abstract An adequate estimation of the aerosol extinction-to-backscatter ratio S is important for solving the underdetermined single scattering lidar equation and for investigating the climate impact of aerosols. In this study, the extinction-to-backscatter ratios for the Nd:YAG wavelengths are calculated for continental, maritime, and desert aerosols; the corresponding aerosol components are varied within the expected natural variabilities of the particle number mixing ratios. For continental aerosol, S increases with the relative humidity f from 40 to 80 sr. For maritime aerosol, the extinction-to-backscatter ratios lie between 15 and 30 sr for 355 and 532 nm and between 25 and 50 sr for 1064 nm. The desert aerosol exhibits a weak dependence of S on f and ranges between 42 and 48 sr for 355 nm and between 17 and 25 sr for 532 and 1064 nm. For practical applications, the calculated values of S are fitted by a power series expansion with respect to their dependence on f.
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paper_title: Modeling of particle size distribution and its influence on the radiative properties of mineral dust aerosol

paper_content:

The radiative parameters of mineral aerosols are strongly dependent on particle size. Therefore explicit modeling of particle size distribution is needed to calculate the radiative effects and the climate impact of mineral dust. We describe a parameterization of the global mineral aerosol size distribution in a transport model using eight size classes between 0.1 and 10 μm. The model prescribes the initial size distribution using soil texture data and aerosol size measurements close to the ground. During transport, the size distribution changes as larger particles settle out faster than smaller particles. Results of Mie scattering calculations of radiative parameters (extinction efficiency, single scattering albedo, asymmetry parameter) of mineral dust are shown at wavelengths between 0.3 and 30 μm for effective particle radii between 0.1 and 10 μm. Also included are radiative properties (reflection, absorption, transmission) calculated for a dust optical thickness of 0.1. Preliminary studies with the Goddard Institute for Space Studies (GISS) general circulation model (GCM), using two particle size modes, show regional changes in radiative flux at the top of the atmosphere as large as +15 W m -2 at solar and +5 W m -2 at thermal wavelengths in the annual mean, indicating that dust forcing is an important factor in the global radiation budget.
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paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

paper_content:

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
---
paper_title: Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV.

paper_content:

A novel light detection and ranging-based remote sensing system was assembled and used to measure mass particulate matter (PM) emissions per unit of fuel burned from in-use on-road vehicles. A commercially available remote sensing system was concurrently used to measure emissions of carbon monoxide (CO), nitrogen oxide (NO) and hydrocarbons (HC). The two systems were used to measure 61,207 gasoline and 1180 diesel powered vehicle emissions in Las Vegas, NV from 4/4/2000 to 5/16/2002. Emission factors were related to vehicle age, weight class and fuel type by matching license IDs to the state registration data. Measurements of vehicle speed and acceleration permitted the analysis of emission factors by vehicle specific power (VSP). Average emission factors were calculated for light-duty (<3863 kg [8500 lbs]) gasoline vehicles (LDGV), light-duty diesel vehicles (LDDV), heavy-duty (>3863 kg [8500 lbs]) gasoline vehicles (HDGV) and heavy-duty diesel vehicles (HDDV). LDDV and HDDV emitted approximately 25 times more PM per mass of fuel than LDGV and HDGV. Sufficient numbers of LDGV were measured to relate VSP with CO, HC and NO emissions. No relationship was observed between PM emissions and VSP. PM emission factors from LDGV increased with vehicle age. Fuel-based emission factors measured by remote sensing were compared with MOBILE6 and PART5 emissions model factors. Good agreement was observed for HC emission factors for vehicles less than 20 years old. MOBILE6 CO emission factors were approximately 2 times greater than measured CO emission factors for vehicles less than 13 years old. Measured NO emission factors were approximately 50% greater than MOBILE6 factors for vehicles 7-15 years old but in good agreement for vehicles less than 7 years old. Measured PM emission factors showed a clear increase with vehicle age, however, PART5 uses only a single PM emission factor for LDGV less than 18 years old. The PM emission factors for the fleet of LDGV, HDGV, LDDV and HDDV were 0.06, 0.05, 1.6 and 1.5 g/kg, respectively.
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paper_title: Measuring Particulate Mass Emissions with the Electrical Low Pressure Impactor

paper_content:

The electrical low pressure impactor (ELPI) is a useful tool for recording transient particle size distributions, such as in motor vehicle emissions. But for sub-micron aerosols, the straightforward mass weighting and integration of these size distributions overestimates the particulate matter (PM) mass by a factor of two or more. The present article examines the sources of this discrepancy and develops an analysis that allows quantitative PM mass measurement with an accuracy of about 20%. This procedure is applied to measure motor vehicle PM emissions, and the results are compared with filter-based gravimetric determinations. Good agreement is achieved for diesel and direct injection gasoline vehicles. For particulate trap equipped diesel vehicles and conventional gasoline vehicles, the PM mass recorded by the ELPI is often substantially lower than the filter based mass owing to the gaseous adsorption artifact of the latter. Accurate work at very low emissions levels, less than ∼ 1 mg/mi, requires furthe...
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paper_title: In-Plume Emission Test Stand 2: Emission Factors for 10- to 100-kW U.S. Military Generators

paper_content:

Although emissions of air pollutants from some military tactical equipment are not subject to the emissions standards, local communities near military bases must conform to the National Ambient Air Quality Standards. Military diesel generators are widely used in training. A portable in-plume system was used to measure fuel-based emission factors (EFs) for particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HCs) for 30-, 60-, and 100-kW generators at five load levels and for cold starts. It was found that EFs depend on multiple parameters including engine size, engine load, unit age, and total running hours. The average CO EF of generators tested was 5% lower, and the average NOx EF was 63% lower than AP-42 estimates; average PM EF was 80% less than the AP-42 estimates. A 2002 model-year 60-kW engine produced 25% less PM than a 1995 engine of the same family with similar running hours. CO EFs decrease with increasing engine load, NOx EFs increase up to mid-loads and decrease slightly at high loads, PM EFs increase with loads for 30- and 60-kW engines. CO and PM have higher EFs and NOx has a lower EF during cold starts than during hot-stabilized operation. PM chemical source profiles were also examined.
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paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

paper_content:

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
---
paper_title: A case study of real-world tailpipe emissions for school buses using a 20% biodiesel blend.

paper_content:

Numerous laboratory studies report carbon monoxide, hydrocarbon, and particulate matter emission reductions with a slight nitrogen oxides emission increase from engines operating with biodiesel and biodiesel blends as compared to using petroleum diesel. We conducted a field study on a fleet of school buses to evaluate the effects of biodiesel use on gaseous and particulate matter fuel-based emission factors under real-world conditions. The field experiment was carried out in two phases during winter 2004. In January (phase I), emissions from approximately 200 school buses operating on petroleum diesel were measured. Immediately after the end of the first phase measurement period, the buses were switched to a 20% biodiesel blend. Emission factors were measured again in March 2004 (phase II) and compared with the January emission factors. To measure gaseous emission factors we used a commercial gaseous remote sensor. Particulate matter emission factors were determined with a combination of the gaseous remote sensor, a Lidar (light detection and ranging), and transmissometer system developed at the Desert Research Institute of Reno, NV, U.S.A. Particulate matter emissions from school buses significantly increased (up to a factor of 1.8) after the switch from petroleum diesel to a 20% biodiesel blend. The fuel used during this campaign was provided by a local distributor and was independently analyzed at the end of the on-road experiment. The analysis found high concentrations of free glycerin and reduced flash points in the B 100 parent fuel. Both measures indicate improper separation and processing of the biodiesel product during production. The biodiesel fuels used in the school buses were not in compliance with the U.S.A. ASTM D6751 biodiesel standard that was finalized in December of 2001. The U.S.A. National Biodiesel Board has formed a voluntary National Biodiesel Accreditation Program for producers and marketers of biodiesel to ensure product quality and compliance with the ASTM standard. The results of our study underline the importance of the program since potential emission benefits from biodiesel may be reduced or even reversed without appropriate fuel quality control on real-world fuels.
---
paper_title: The In-Plume Emission Test Stand: An Instrument Platform for the Real-Time Characterization of Fuel-Based Combustion Emissions

paper_content:

Abstract The In-Plume Emission Test Stand (IPETS) characterizes gaseous and particulate matter (PM) emissions from combustion sources in real time. Carbon dioxide (CO2), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), and other gases are quantified with a closed-path Fourier transform infrared spectrometer (FTIR). Particle concentrations, chemical composition, and other particle properties are characterized with an electrical low-pressure impactor (ELPI), a light-scattering particle detector, an optical particle counter, and filter samples amenable to different laboratory analysis. IPETS measurements of fuel-based emission factors for a diesel generator are compared with those from a Mobile Emissions Laboratory (MEL). IPETS emission factors ranged from 0.3 to 11.8, 0.2 to 3.7, and 22.2 to 32.8 g/kg fuel for CO, NO2, and NO, respectively. IPETS PM emission factors ranged from 0.4 to 1.4, 0.3 to 1.8, 0.3 to 2.2, and 1 to 3.4 g/kg fuel for filter, photoacoustic, nephelometer, and impactor me...
---
paper_title: Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV.

paper_content:

A novel light detection and ranging-based remote sensing system was assembled and used to measure mass particulate matter (PM) emissions per unit of fuel burned from in-use on-road vehicles. A commercially available remote sensing system was concurrently used to measure emissions of carbon monoxide (CO), nitrogen oxide (NO) and hydrocarbons (HC). The two systems were used to measure 61,207 gasoline and 1180 diesel powered vehicle emissions in Las Vegas, NV from 4/4/2000 to 5/16/2002. Emission factors were related to vehicle age, weight class and fuel type by matching license IDs to the state registration data. Measurements of vehicle speed and acceleration permitted the analysis of emission factors by vehicle specific power (VSP). Average emission factors were calculated for light-duty (<3863 kg [8500 lbs]) gasoline vehicles (LDGV), light-duty diesel vehicles (LDDV), heavy-duty (>3863 kg [8500 lbs]) gasoline vehicles (HDGV) and heavy-duty diesel vehicles (HDDV). LDDV and HDDV emitted approximately 25 times more PM per mass of fuel than LDGV and HDGV. Sufficient numbers of LDGV were measured to relate VSP with CO, HC and NO emissions. No relationship was observed between PM emissions and VSP. PM emission factors from LDGV increased with vehicle age. Fuel-based emission factors measured by remote sensing were compared with MOBILE6 and PART5 emissions model factors. Good agreement was observed for HC emission factors for vehicles less than 20 years old. MOBILE6 CO emission factors were approximately 2 times greater than measured CO emission factors for vehicles less than 13 years old. Measured NO emission factors were approximately 50% greater than MOBILE6 factors for vehicles 7-15 years old but in good agreement for vehicles less than 7 years old. Measured PM emission factors showed a clear increase with vehicle age, however, PART5 uses only a single PM emission factor for LDGV less than 18 years old. The PM emission factors for the fleet of LDGV, HDGV, LDDV and HDDV were 0.06, 0.05, 1.6 and 1.5 g/kg, respectively.
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paper_title: Light Absorption by Carbonaceous Particles: An Investigative Review

paper_content:

The optical properties of the light-absorbing, carbonaceous substance often called “soot,” “black carbon,” or “carbon black" have been the subject of some debate. These properties are necessary to model how aerosols affect climate, and our review is targeted specifically for that application. We recommend the term light-absorbing carbon to avoid conflict with operationally based definitions. Absorptive properties depend on molecular form, particularly the size of sp 2-bonded clusters. Freshly-generated particles should be represented as aggregates, and their absorption is like that of particles small relative to the wavelength. Previous compendia have yielded a wide range of values for both refractive indices and absorption cross section. The absorptive properties of light-absorbing carbon are not as variable as is commonly believed. Our tabulation suggests a mass-normalized absorption cross section of 7.5 ± 1.2 m2/g at 550 nm for uncoated particles. We recommend a narrow range of refractive indices for s...
---
paper_title: Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV.

paper_content:

A novel light detection and ranging-based remote sensing system was assembled and used to measure mass particulate matter (PM) emissions per unit of fuel burned from in-use on-road vehicles. A commercially available remote sensing system was concurrently used to measure emissions of carbon monoxide (CO), nitrogen oxide (NO) and hydrocarbons (HC). The two systems were used to measure 61,207 gasoline and 1180 diesel powered vehicle emissions in Las Vegas, NV from 4/4/2000 to 5/16/2002. Emission factors were related to vehicle age, weight class and fuel type by matching license IDs to the state registration data. Measurements of vehicle speed and acceleration permitted the analysis of emission factors by vehicle specific power (VSP). Average emission factors were calculated for light-duty (<3863 kg [8500 lbs]) gasoline vehicles (LDGV), light-duty diesel vehicles (LDDV), heavy-duty (>3863 kg [8500 lbs]) gasoline vehicles (HDGV) and heavy-duty diesel vehicles (HDDV). LDDV and HDDV emitted approximately 25 times more PM per mass of fuel than LDGV and HDGV. Sufficient numbers of LDGV were measured to relate VSP with CO, HC and NO emissions. No relationship was observed between PM emissions and VSP. PM emission factors from LDGV increased with vehicle age. Fuel-based emission factors measured by remote sensing were compared with MOBILE6 and PART5 emissions model factors. Good agreement was observed for HC emission factors for vehicles less than 20 years old. MOBILE6 CO emission factors were approximately 2 times greater than measured CO emission factors for vehicles less than 13 years old. Measured NO emission factors were approximately 50% greater than MOBILE6 factors for vehicles 7-15 years old but in good agreement for vehicles less than 7 years old. Measured PM emission factors showed a clear increase with vehicle age, however, PART5 uses only a single PM emission factor for LDGV less than 18 years old. The PM emission factors for the fleet of LDGV, HDGV, LDDV and HDDV were 0.06, 0.05, 1.6 and 1.5 g/kg, respectively.
---
paper_title: Characterization of on-road vehicle NO emissions by a TILDAS remote sensor

paper_content:

A tunable infrared laser differential absorption spectrometer (TILDAS) was used to remotely sense the nitric oxide (NO) emissions from 1,473 on-road vehicles. The real-world measurement precision of this instrument in the limit of low NO concentration is 5 ppm of the vehicle exhaust, which corresponds to a 3o detection limit of 15 ppm. Our analysis of the distribution of negative concentration measurements produced during this experiment supports this claim, showing that the instrumental noise for this set of measurements was at most 8 ppm in the limit of low NO concentration. The high sensitivity of this instrument allowed us to measure the NO emissions of even the cleanest vehicles. The measured vehicle fleet NO emissions closely fit a gamma distribution with 10% of the fleet contributing about 50% of the total fleet emissions. Newer vehicles had lower NO emissions than older ones, but high NO emitters were found in every vehicle age cohort. On a vehicle-by-vehicle basis, NO emissions correlated very weakly with vehicle velocity, acceleration, power per unit mass, carbon monoxide (CO) emissions, and hydrocarbon (HC) emissions. High NO emitting vehicles could not be identified by remote sensing of CO or HC emissions and vice versa. When we compared the NO emissions for 117 vehicles measured more than one time, about half of the high NO emitters were found to be very consistent, while the other half varied significantly.
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paper_title: Individual Measurements of the Emission Factor of Aerosol Black Carbon in Automobile Plumes

paper_content:

As automobiles passed a measuring point, we recorded the concentrations of carbon dioxide and aerosol black carbon (BC) in their dispersing exhaust plumes. After subtraction of background levels, the ratio of the increments of these species allows us to calculate the emission factor of BC per unit mass of fuel from each individual vehicle. These factors spanned a range of greater than two orders of magnitude, representing the emission of from 4 × 10−6 to 10−3 grams of aerosol black carbon per gram of carbon consumed in the fuel. Their distribution showed that 20 percent of the vehicles accounted for 65 percent of the emissions. The real-time measurement methodology allows for a determination of the distribution of emission factors across the actual population of sources. These results are similar to the wide range of carbon monoxide emission factors reported recently.
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paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

paper_content:

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
---
paper_title: Characterization of on-road vehicle NO emissions by a TILDAS remote sensor

paper_content:

A tunable infrared laser differential absorption spectrometer (TILDAS) was used to remotely sense the nitric oxide (NO) emissions from 1,473 on-road vehicles. The real-world measurement precision of this instrument in the limit of low NO concentration is 5 ppm of the vehicle exhaust, which corresponds to a 3o detection limit of 15 ppm. Our analysis of the distribution of negative concentration measurements produced during this experiment supports this claim, showing that the instrumental noise for this set of measurements was at most 8 ppm in the limit of low NO concentration. The high sensitivity of this instrument allowed us to measure the NO emissions of even the cleanest vehicles. The measured vehicle fleet NO emissions closely fit a gamma distribution with 10% of the fleet contributing about 50% of the total fleet emissions. Newer vehicles had lower NO emissions than older ones, but high NO emitters were found in every vehicle age cohort. On a vehicle-by-vehicle basis, NO emissions correlated very weakly with vehicle velocity, acceleration, power per unit mass, carbon monoxide (CO) emissions, and hydrocarbon (HC) emissions. High NO emitting vehicles could not be identified by remote sensing of CO or HC emissions and vice versa. When we compared the NO emissions for 117 vehicles measured more than one time, about half of the high NO emitters were found to be very consistent, while the other half varied significantly.
---
paper_title: On-road vehicle particulate matter and gaseous emission distributions in Las Vegas, Nevada, compared with other areas.

paper_content:

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.
---
paper_title: CORRELATION BETWEEN AUTOMOTIVE CO, HC, NO, AND PM EMISSION FACTORS FROM ON-ROAD REMOTE SENSING: IMPLICATIONS FOR INSPECTION AND MAINTENANCE PROGRAMS

paper_content:

Abstract Carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NO) emission factors (EFs) are measured with a commercial vehicle emissions remote sensing system (VERSS) during a large-scale vehicle exhaust emissions study in Las Vegas. Particulate matter (PM) EFs are simultaneously measured for individual vehicles with a newly developed PM-VERSS based on ultraviolet backscatter light detection and ranging (Lidar). The effectiveness of CO and HC EFs as proxy for NO and PM EFs for spark-ignition vehicles is evaluated. Poor correlations were found between EFs for pollutants on an individual vehicle basis indicating that high EFs for one or more pollutants cannot be used as a predictor of high EFs for other pollutants. Stronger functional relationships became evident after averaging the EF data in bins based on rank-order of a single pollutant EF. Low overlap between the highest 10% emitters for CO, HC, NO, and PM was found. These results imply that for an effective reduction of the four pollutants, inspection and maintenance (I/M) programs, including clean screening, should measure all four pollutants individually. Fleet average CO and HC concentrations determined by gaseous VERSS were compared with fleet average CO and HC concentrations measured at low-idle and at high-idle during local I/M tests for spark-ignition vehicles. The fleet average CO concentrations measured by I/M tests at either idle were about half of those measured by remote sensing. The fleet average high-idle HC concentration measured by I/M tests was about half of that measured by VERSS while low-idle I/M and VERSS HC average concentrations were in better agreement. For a typical vehicle trip, most of the fuel is burned during non-idle conditions. I/M measurements collected during idling conditions may not be a good indicator of a vehicle’s potential to be a high emitter. VERSS measurements, when the vehicle is under a load, should more effectively identify high emitting vehicles that have a large contribution to the mobile emissions inventory.
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paper_title: A case study of real-world tailpipe emissions for school buses using a 20% biodiesel blend.

paper_content:

Numerous laboratory studies report carbon monoxide, hydrocarbon, and particulate matter emission reductions with a slight nitrogen oxides emission increase from engines operating with biodiesel and biodiesel blends as compared to using petroleum diesel. We conducted a field study on a fleet of school buses to evaluate the effects of biodiesel use on gaseous and particulate matter fuel-based emission factors under real-world conditions. The field experiment was carried out in two phases during winter 2004. In January (phase I), emissions from approximately 200 school buses operating on petroleum diesel were measured. Immediately after the end of the first phase measurement period, the buses were switched to a 20% biodiesel blend. Emission factors were measured again in March 2004 (phase II) and compared with the January emission factors. To measure gaseous emission factors we used a commercial gaseous remote sensor. Particulate matter emission factors were determined with a combination of the gaseous remote sensor, a Lidar (light detection and ranging), and transmissometer system developed at the Desert Research Institute of Reno, NV, U.S.A. Particulate matter emissions from school buses significantly increased (up to a factor of 1.8) after the switch from petroleum diesel to a 20% biodiesel blend. The fuel used during this campaign was provided by a local distributor and was independently analyzed at the end of the on-road experiment. The analysis found high concentrations of free glycerin and reduced flash points in the B 100 parent fuel. Both measures indicate improper separation and processing of the biodiesel product during production. The biodiesel fuels used in the school buses were not in compliance with the U.S.A. ASTM D6751 biodiesel standard that was finalized in December of 2001. The U.S.A. National Biodiesel Board has formed a voluntary National Biodiesel Accreditation Program for producers and marketers of biodiesel to ensure product quality and compliance with the ASTM standard. The results of our study underline the importance of the program since potential emission benefits from biodiesel may be reduced or even reversed without appropriate fuel quality control on real-world fuels.
---
paper_title: Combustion of fat and vegetable oil derived fuels in diesel engines

paper_content:

In this article, the status of fat and oil derived diesel fuels with respect to fuel properties, engine performance, and emissions is reviewed. The fuels considered are primarily the methyl esters of fatty acids derived from a variety of vegetable oils and animal fats, and referred to as biodiesel. The major obstacle to widespread use of biodiesel is the high cost relative to petroleum. Economics of biodiesel production are discussed, and it is concluded that the price of the feedstock fat or oil is the major factor determining biodiesel price.Biodiesel is completely miscible with petroleum diesel fuel, and is generally tested as a blend. The use of biodiesel in neat or blended form has no effect on the energy based engine fuel economy. The lubricity of these fuels is superior to conventional diesel, and this property is imparted to blends at levels above 20 vol%. Emissions of PM can be reduced dramatically through use of biodiesel in engines that are not high lube oil emitters. Emissions of NOx increase significantly for both neat and blended fuels in both two- and four-stroke engines. The increase may be lower in newer, lower NOx emitting four-strokes, but additional data are needed to confirm this conclusion. A discussion of available data on unregulated air toxins is presented, and it is concluded that definitive studies have yet to be performed in this area. A detailed discussion of important biodiesel properties and recommendations for future research is presented. Among the most important recommendations is the need for all future studies to employ biodiesel of well-known composition and purity, and to report detailed analyses. The purity levels necessary for achieving adequate engine endurance, compatibility with coatings and elastomers, cold flow properties, stability, and emissions performance must be better defined.
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paper_title: Vehicle self-pollution intake fraction : Children's exposure to school bus emissions

paper_content:

Vehicle self-pollution occurs when a vehicle's emissions migrate to inside that vehicle's passenger compartment. This paper presents values for two new parameters: vehicle self-pollution intake fraction (iFSP), which is the total fraction of a vehicle's emissions inhaled by all people in the vehicle, and vehicle self-pollution individual intake fraction (iFi,SP), which is the fraction of a vehicle's emissions inhaled by an individual in the vehicle. We use results from tracer-gas experiments in California's South Coast Air Basin (SoCAB) to quantify students' iFSP and iFi,SP for school bus emissions. Six buses were studied during nine runs with windows open and seven runs with windows closed. Reported iFSP values (units: per million; min = 10, max = 94, mean = 27) indicate that the total mass of a bus' exhaust inhaled by students commuting on it is comparable in magnitude to the total mass of that bus' exhaust inhaled by all other people in the SoCAB. Reported iFi,SP values (units: per million; min = 0....
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paper_title: A case study of real-world tailpipe emissions for school buses using a 20% biodiesel blend.

paper_content:

Numerous laboratory studies report carbon monoxide, hydrocarbon, and particulate matter emission reductions with a slight nitrogen oxides emission increase from engines operating with biodiesel and biodiesel blends as compared to using petroleum diesel. We conducted a field study on a fleet of school buses to evaluate the effects of biodiesel use on gaseous and particulate matter fuel-based emission factors under real-world conditions. The field experiment was carried out in two phases during winter 2004. In January (phase I), emissions from approximately 200 school buses operating on petroleum diesel were measured. Immediately after the end of the first phase measurement period, the buses were switched to a 20% biodiesel blend. Emission factors were measured again in March 2004 (phase II) and compared with the January emission factors. To measure gaseous emission factors we used a commercial gaseous remote sensor. Particulate matter emission factors were determined with a combination of the gaseous remote sensor, a Lidar (light detection and ranging), and transmissometer system developed at the Desert Research Institute of Reno, NV, U.S.A. Particulate matter emissions from school buses significantly increased (up to a factor of 1.8) after the switch from petroleum diesel to a 20% biodiesel blend. The fuel used during this campaign was provided by a local distributor and was independently analyzed at the end of the on-road experiment. The analysis found high concentrations of free glycerin and reduced flash points in the B 100 parent fuel. Both measures indicate improper separation and processing of the biodiesel product during production. The biodiesel fuels used in the school buses were not in compliance with the U.S.A. ASTM D6751 biodiesel standard that was finalized in December of 2001. The U.S.A. National Biodiesel Board has formed a voluntary National Biodiesel Accreditation Program for producers and marketers of biodiesel to ensure product quality and compliance with the ASTM standard. The results of our study underline the importance of the program since potential emission benefits from biodiesel may be reduced or even reversed without appropriate fuel quality control on real-world fuels.
---

Title: Monitoring Automotive Particulate Matter Emissions with LiDAR: A Review

Section 1: Introduction and Background
Description 1: Write about the importance of monitoring automotive particulate matter emissions, the effects of these emissions, and the recent development of LiDAR technology for this purpose.

Section 2: Vehicle Emissions
Description 2: Discuss the variability in vehicle emissions, factors influencing emissions, and the need for detailed emission inventories and prediction tools.

Section 3: Measurement Challenges
Description 3: Describe the different approaches and challenges in measuring vehicle emissions, emphasizing the advantages and limitations of remote sensing.

Section 4: Vehicle Emission Remote Sensing Systems
Description 4: Detail the function and setup of Vehicle Emissions Remote Sensing Systems (VERSS), focusing on the measurement of gaseous emissions and their integration with PM measurements.

Section 5: Fuel-Based Pollutant Emission Factors Calculation
Description 5: Explain the methodology for calculating fuel-based emission factors using the mass column content of pollutants and carbon.

Section 6: Measurement Approach and Instrument Design
Description 6: Present the design and functionality of the UV LiDAR and transmissometer system, including calibration, backscattering coefficients, and sources of uncertainty.

Section 7: State of the Art
Description 7: Review the current state of technologies for measuring PM emissions, including opacity-based and LiDAR-based methods, and their limitations and advancements.

Section 8: UV LiDAR and Transmissometer Unit
Description 8: Provide a detailed description of the UV LiDAR and transmissometer unit developed, including its setup, components, and calibration procedures.

Section 9: Method a. Transmissometer
Description 9: Elaborate on the method used by the transmissometer to measure PM emissions, including calculations and assumptions.

Section 10: Method b. LiDAR Calibration and Inversion
Description 10: Discuss the calibration process for the LiDAR system and the inversion techniques used to retrieve backscattering coefficients.

Section 11: Method c. Linearity and Dynamic Range Limitations of the Detector
Description 11: Describe the limitations of the detector's linearity and dynamic range and the empirical model used to correct the PMT nonlinearity.

Section 12: Method d. Source of Uncertainty
Description 12: Outline the various sources of uncertainty in the measurements and the steps taken to minimize these uncertainties.

Section 13: Method e. Gaseous Remote Sensing Unit
Description 13: Explain the integration of the gaseous remote sensing unit and its role in normalizing the PM mass column content for accurate EF calculation.

Section 14: Particulate Matter Extinction Mass Efficiency
Description 14: Define the calculation of extinction mass efficiency and its importance in relating particle number concentration to PM mass.

Section 15: Particulate Matter Backscattering Mass Efficiency
Description 15: Discuss the derivation of backscattering mass efficiency and its application in LiDAR measurements.

Section 16: Applications to Vehicle Emitted Particulate
Description 16: Review studies of particle morphology and how equivalent sphere models and size distributions are used in exhaust particle measurements.

Section 17: Mass Efficiency Sensitivity Study
Description 17: Present the sensitivity study on particle density, index of refraction, and size distributions, and their influence on mass efficiencies.

Section 18: Road Dust Contribution
Description 18: Discuss the contributions of road dust to measurements and its negligible impact on paved roads.

Section 19: Calculation of Emission Factors from Backscattering and Extinction Measurements
Description 19: Provide an example from the field demonstrating the calculations of emission factors using backscattering and extinction measurements.

Section 20: Field LiDAR Validation
Description 20: Review the validation of LiDAR measurements against other established methods during field studies.

Section 21: Results from Various Field Deployments
Description 21: Summarize the results from field campaigns demonstrating the system's applicability and flexibility.

Section 22: Las Vegas, Nevada 2000-2002: On-Ramp Freeway Vehicle Emissions
Description 22: Describe the objectives, methods, and key findings from the Las Vegas field campaign.

Section 23: Meridian, Idaho 2004: School-Busses Emissions, Petroleum-versus Bio-Diesel
Description 23: Summarize the experiment conducted on school buses comparing petroleum diesel and biodiesel emissions under real-world conditions.

Section 24: Conclusions
Description 24: Conclude with the significance of the LiDAR-based remote sensing system in monitoring PM emissions and its applications and limitations.