Criteria and air-toxic emissions from in-use automobiles in the National Low-Emission Vehicle program

The U.S. Environmental Protection Agency (EPA) implemented a program to identify tailpipe emissions of criteria and air-toxic contaminants from in-use, light-duty low-emission vehicles (LEVs). EPA recruited 25 LEVs in 2002 and measured emissions on a chassis dynamometer using the cold-start urban dynamometer driving schedule of the Federal Test Procedure. The emissions measured included regulated pollutants, particulate matter, speciated hydrocarbon compounds, and carbonyl compounds. The results provided a comparison of emissions from real-world LEVs with emission standards for criteria and air-toxic compounds. Emission measurements indicated that a portion of the in-use fleet tested exceeded standards for the criteria gases. Real-time regulated and speciated hydrocarbon measurements demonstrated that the majority of emissions occurred during the initial phases of the cold-start portion of the urban dynamometer driving schedule. Overall, the study provided updated emission factor data for real-world, in-use operation of LEVs for improved emissions modeling and mobile source inventory development.     

Modeling In-Use Vehicle Emissions and the Effects of Inspection and Maintenance Programs

Different ways for modeling the impact of vehicle emission inspection and maintenance programs on fleet hydrocarbon emissions are examined. A dynamic model is developed for forecasting fleet emissions in which individual vehicle performance is modeled as a stochastic process and vehicle emissions are tracked over time. Emissions inspection and repair are incorporated into the model, allowing for the stochastic aspects of both testing and repair. This model is compared to EPA’s model for evaluating the impact of vehicle emissions inspection and maintenance. We find that the way vehicle emission equipment deterioration overtime is modeled is important for forecasting emissions from the fleet and for assessing the success of inspection and maintenance programs. For inspection programs, we find that factors such as the proportion of vehicles tested, and repair effectiveness and duration have the greatest impact on emission reductions. The ability of different emission testing regimes to identify polluting vehicles has less impact on a program’s overall potential for emissions reduction. Policy recommendations for I&M testing and predictions of emission reduction credits from these tests will depend in important ways on the methods used in the underlying emissions models.     

Sulfate Emissions from Catalyst-Equipped Automobiles on the Highway

Abstract

A systematic investigation of solid and gaseous atmospheric emissions from some coke-oven batteries of one of Europe’s largest integrated steel factory (Taranto, Italy) has been carried out. In air monitoring samples, polycyclic aromatic hydrocarbons (PAHs) were consistently detected at concentrations largely exceeding threshold limit values. By means of PAHs speciation profile and benzo (a)pyrene (BaP) equivalent dispersion modeling from diffuse sources, the study indicated that serious health risks exist not only in working areas, but also in a densely populated residential district near the factory.     

Characterization of In-Use Light-Duty Gasoline Vehicle Emissions by Remote Sensing in Beijing: Impact of Recent Control Measures

Abstract

China’s national government and Beijing city authorities have adopted additional control measures to reduce the negative impact of vehicle emissions on Beijing’s air quality. An evaluation of the effectiveness of these measures may provide guidance for future vehicle emission control strategy development. In-use emissions from light-duty gasoline vehicles (LDGVs) were investigated at five sites in Beijing with remote sensing instrumentation. Distance-based mass emission factors were derived with fuel consumption modeled on real world data. The results show that the recently implemented aggressive control strategies are significantly reducing the emissions of on-road vehicles. Older vehicles are contributing substantially to the total fleet emissions. An earlier program to retrofit pre-Euro cars with three-way catalysts produced little emission reduction. The impact of model year and driving conditions on the average mass emission factors indicates that the durability of vehicles emission controls may be inadequate in Beijing.     

Photochemical Reactivities of Exhausts from 1966 Model Automobiles Equipped to Reduce Hydrocarbon Emissions

During the summer of 1966, a selected group of automobiles from the Cincinnati phase of the GSA study were used in an irradiation chamber study. The study was conducted to evaluate the photochemical air pollution potential of representative models of the equipped and unequipped automobiles. Only one set of automobiles, the unequipped Chevelles, produced exhaust capable upon irradiation of forming significant levels of oxidant and PAN. Neither the equipped Chevelles nor any of the Fords or Plymouths, whether equipped or unequipped, produced exhaust having the characteristics necessary to form oxidant or PAN upon irradiation. The eye irritation level reported by the panel upon irradiation of exhaust from unequipped Chevelles was much higher than that produced by the irradiated exhausts from any of the other types of automobiles. Overall, there does appear to be some small improvement with respect to eye irritation in comparing equipped with unequipped automobiles. To a large extent, the improvement in the air pollution potential of exhaust from equipped Chevelles compared to the unequipped Chevelles can be attributed to the reduction in the hydrocarbon to nitrogen oxide ratio. The irradiated exhaust from equipped Chevelles, except for aldehyde levels, is about the same in photochemical air pollution potential as are the exhausts from both equipped and unequipped Fords and Plymouths which are maintained under lean operating conditions. Such irradiation chamber measurements are related to exhaust not hydrocarbon reactivities. Hydrocarbon reactivities can be obtained by direct measurement of reactive and nonreactive hydrocarbons in the automotive emissions.     

Real-World Vehicle Emissions: A Summary of the Ninth Coordinating Research Council On-Road Vehicle Emissions Workshop

ABSTRACT

In April 1999, the Coordinating Research Council sponsored a workshop focusing on our understanding of real-world emissions from motor vehicles. This summary presents the latest information on in-use light- and heavy-duty vehicle tailpipe and evaporative emissions, the effects of fuels on emissions, field programs designed to understand the contribution of mobile sources to emission inventories, efforts to evaluate and improve mobile source emission models, progress of vehicle inspection/ maintenance programs, and topics for future research. While significant progress has been made in understanding in-use vehicle emissions, further improvements are necessary. Moreover, the impact of current and future changes in emission control technologies and control programs will have to be monitored for effectiveness and incorporated into the emission factor models.     

Urban CO Concentrations and Vehicle Emissions

The effect of the general growth of CO vehicular emissions in urban areas on the CAMP station measurements in downtown areas, where vehicular traffic is saturated is considered. With the assumption that the street-level CO concentration is derived from the sum of an urban background term and a local street-effect term, the urban background CO concentration is computed with a diffusion model by introducing a simple area source distribution. The local street-effect term is taken to be constant at a saturation emission level corresponding to a saturation traffic density when the emission per vehicle-mile and meteorological conditions are fixed. The present analysis indicates that the local street-effect term, AC, has a major role in determining street-level concentrations for pollutants, such as CO, whose air quality standard is based on maximum concentrations with averaging times of 1 hour and 8 hours. The relevance of this analysis to the abatement requirements of the Clean Air Amendments and to the driving cycle adopted is discussed.     

Real-World Vehicle Emissions: A Summary of the Tenth Coordinating Research Council On-Road Vehicle Emissions Workshop

ABSTRACT

The Coordinating Research Council (CRC) held its tenth workshop in March 2000, focusing on results from the most recent real-world vehicle emissions research. In this paper, we summarize the presentations from researchers who are engaged in improving our understanding of the contribution of mobile sources to emission inventories. Participants in the workshop discussed efforts to improve mobile source emission models and emission inventories, results from gas- and particle-phase emissions studies from spark-ignition and diesel-powered vehicles, new methods for measuring mobile source emissions, improvements in vehicle emission control systems (ECSs), and evaluation of motor vehicle inspection/maintenance (I/M) programs, as well as topics for future research.     

Real-World Vehicle Emissions: A Summary of the Sixth Coordinating Research Council On-Road Vehicle Emissions Workshop

The Coordinating Research Council (CRC) has conducted a series of workshops on real-world vehicle emissions. This article summarizes findings from the most recent research regarding on-road emissions from mobile sources, presented at the CRC workshop held in March 1996. Among the topics discussed were efforts to improve and update emission models, results from field studies designed to understand the contribution of mobile sources to emission inventories, results from gas-and particle-phase emissions studies from in-use motor vehicles, and areas of future research.

The Sixth Coordinating Research Council (CRC) On-Road Vehicle Emissions Workshop was held March 18-20, 1996, in San Diego, CA. More than 160 representatives from academia, industry, government, and consulting firms in the United States, Canada, and Europe participated in the three-day meeting. The objective of the Workshop was to present the most recent information from research programs on:

mobile source contributions to the emission inventory

emission factor models and activity data

model comparison and development

emission reduction programs

new developments in remote sensing

studies of on-road vehicle exhaust and non-tailpipe emissions

off-cycle Federal Test Procedure (FTP) studies and revisions to the FTP

particle emissions from the light- and heavy-duty fleets

future research needs

Nine sessions were devoted to vehicle emissions models, improvements to the emission inventory, on-road and tunnel studies, off-cycle emissions, non-tailpipe and diesel emissions, emission reduction programs, and remote sensing. Overall workshop coordination was provided by Timothy Belian and the CRC staff, with Steven Cadle and Robert Gorse serving as cochairmen. Individual session chairmen were Brent Bailey (National Renewable Energy Laboratory), Mark Carlock (California Air Resources Board), Harold Haskew (General Motors), Kenneth Knapp and Philip Lorang (U.S. Environmental Protection Agency), Douglas Lawson (Colorado State University), Alan Lloyd (Desert Research Institute), Robert Slott (Shell Oil), and Timothy Truex (University of California, Riverside). In addition, during the Workshop, Lesha Hrynchuk of the California Air Resources Board (CARB) presented a hands-on demonstration using the Internet to obtain motor vehicle emissions information from groups throughout the world. The complete Workshop proceedings are available from the Coordinating Research Council, 219 Perimeter Center Parkway, Atlanta, GA 30346; phone: (770) 396-3400; fax: (770) 396-3404. The following summarizes each session and includes a short synopsis of all the papers that were presented.     

Real-World Emissions from a Modern Production Vehicle Driven in Los Angeles

The emissions of hydrocarbons, nitric oxide, and carbon monoxide from one modern vehicle were measured using on-board instrumentation during about 350 miles of driving in Los Angeles, California. Emissions during on-road driving were compared to those obtained on dynamometers using the urban dynamometer driving schedule (UDDS). Although this study only used one driver and vehicle, tested over a relatively short distance, the analysis technique may be useful for a larger evaluation of off-cycle emissions.

The test vehicle had low warmed-up running emissions over the UDDS and for most of the on-road testing where the air-to-fuel ratio was maintained at the stoichiometric point. However, occasional heavily-loaded conditions during the on-road testing led to richerthan-stoiehiometric operation.

During these brief enrichment events, which lasted up to 29 seconds, CO emissions were increased by a factor of 2500 and HC by a factor of 40 over closed-loop stoichiometric operation. Nitrogen oxide emissions were similar during low-load stoichiometric operation and high-load enriched operation. The relatively constant gram-per-second emission rate of CO and HC observed during enriched operation suggests that such information can be combined with determinations of the frequency of enrichment for a large number of vehicles with similar calibrations to estimate the impact of the additional emissions from enrichment on emissions inventories.     

A Characterization of Emissions from an Early Model Flexible-Fuel Vehicle

An emission study was conducted on a 1987 Ford Crown Victoria flexible-fuel vehicle, an early prototype which had been driven about 25,000 miles. The vehicle was run on both gasoline and a blend of 85 percent methanol and 15 percent gasoline. Emission rates of regulated pollutants (hydrocarbons, carbon monoxide, nitrogen oxides, formaldehyde, and methanol) and nonregulated pollutants (speciated organic materials) were determined for both exhaust and evaporative emissions. Tests were run varying the driving cycle, ambient temperature and catalytic converter. In general, hydrocarbon composition of exhaust emissions was significantly affected by catalyst replacement and cold starts, slightly affected by driving schedule, and unaffected by ambient temperature and test fuel. Hydrocarbon composition of evaporative emissions was only sensitive to the type of evaporative test being performed: diurnal tests typically had larger fractions of lower molecular weight paraffins than hot soak tests.     

Costs,Emissions Reductions,and Vehicle Repair: Evidence from Arizona

ABSTRACT

The Arizona inspection and maintenance (I/M) program provides one of the first opportunities to examine the costs and effectiveness of vehicle emission repair. This paper examines various aspects of emission reductions, fuel economy improvements, and repair costs, drawing data from over 80,000 vehicles that failed the I/M test in Arizona between 1995 and the first half of 1996. We summarize the wealth of data on repair from the Arizona program and highlight its limitations. Because missing or incomplete cost information has been a serious shortcoming for the evaluation of I/M programs, we develop a method for estimating repair costs when they are not reported. We find surprising evidence that almost one quarter of all vehicles that take the I/M test are never observed to pass the test. Using a statistical analysis, we provide some information about the differences between the vehicles that pass and those that do not. Older, more polluting vehicles are much more likely never to pass the I/M test, and their expected repair costs are much higher than those for newer cars.

This paper summarizes the evidence on costs and emission reductions in the Arizona program, comparing costs and emissions reductions between cars and trucks. Finally, we examine the potential for more cost-effective repair, first through an analysis of tightening I/M cut points and then by calculating the cost savings of achieving different emission reduction goals when the most cost-effective repairs are made first.     

Daily Variability of Motor Vehicle Emissions Derived from Traffic Counter Data

ABSTRACT

This work studied the daily variability of mobile sources in rural and urban areas, in and around the Atlanta Metropolitan Area. Traffic counter data collected during the 1992 Southern Oxidants Study Atlanta Intensive Study were used to analyze the spatial and temporal distribution of traffic volume. A simple method to study the daily variability of mobile emissions from the different types of urban and rural roads is presented. The method is based on hourly traffic volume data and emission factors and it has been generalized to describe the daily variability of mobile emissions for urban and rural areas and for the whole modeling domain. Implications of this study for improving mobile emission inventories are also discussed.     

Effects of Fuel Type,Driving Cycle,and Emission Status on In-Use Vehicle Exhaust Reactivity

ABSTRACT

The introduction of reformulated gasolines significantly reduced exhaust hydrocarbon (HC) mass emissions, but few data are available concerning how these new fuels affect exhaust reactivity. Similarly, while it is well established that high-emitting vehicles contribute a significant portion of total mobile source HC mass emissions, it is also important to evaluate the exhaust reactivity from these vehicles. The objective of this study was to evaluate the relative influence on in-use vehicle exhaust reactivity of three critical factors: fuel, driving cycle, and vehicle emission status. Nineteen in-use vehicles were tested with seven randomly assigned fuel types and two driving cycles: the Federal Test Procedure (FTP) and the Unified Cycle (UC). Total exhaust reactivity was not statistically different between the FTP and UC cycles but was significantly affected by fuel type. On average, the exhaust reactivity for California Phase 2 fuel was the lowest (16 % below the highest fuel type) among the seven fuels tested for cold start emissions. The average exhaust reactivity for high-emitting vehicles was significantly higher for hot stabilized (11%) and hot start (15%) emissions than for low-emitting vehicles. The exhaust reactivities for the FTP and UC cycles for light-end HCs and carbonyls were significantly different for the hot stabilized mode. There was a significant fuel effect on the mean specific reactivity (SR) for the mid-range HCs, but not for light-end HCs or carbonyls, while vehicle emission status affected the mean SR for all three HC compound classes.     

Real-World In-Use Activity,Fuel Use,and Emissions for Nonroad Construction Vehicles: A Case Study for Excavators

Abstract

A study design was developed and demonstrated for deployment of a portable emission measurement system (PEMS) for excavators. Excavators are among the most commonly used vehicles in construction activities. The PEMS measured nitric oxide, carbon monoxide, hydrocarbons, carbon dioxide, and opacity-based particulate matter. Data collection, screening, processing, and analysis protocols were developed to assure data quality and to quantify variability in vehicle fuel consumption and emissions rates. The development of data collection procedures was based on securing the PEMS while avoiding disruption to normal vehicle operations. As a result of quality assurance, approximately 90% of the attempted measurements resulted in valid data. On the basis of field data collected for three excavators, an average of 50% of the total nitric oxide emissions was associated with 29% of the time of operation, during which the average engine speed and manifold absolute pressure were significantly higher than corresponding averages for all data. Mass per time emission rates during non-idle modes (i.e., moving and using bucket) were on average 7 times greater than for the idle mode. Differences in normalized average rates were influenced more by intercycle differences than intervehicle differences. This study demonstrates the importance of accounting for intercycle variability in real-world in-use emissions to develop more accurate emission inventories. The data collection and analysis methodology demonstrated here is recommended for application to more vehicles to better characterize real-world vehicle activity, fuel use, and emissions for nonroad construction equipment.     

Status of Control of Motor Vehicle Emissions in California

The State of California, because of an acute air pollution problem has been forced to move ahead on a pioneer basis to control motor vehicle emissions. The Golden State’s program, as put into operation by the Motor Vehicle Pollution Control Board, is discussed in detail. Inspection-installation stations, enforcement and legal requirements relating to crankcase control devices and other facets of the program are presented. Of particular importance is the experience gained by the Board in requiring devices on all new vehicles registered in California and its used vehicle program, affecting vehicles back to the 1950 model year. Recent developments in exhaust control, anticipated installation requirements, and scheduling, as well as an indication of staff long-term planning is also outlined. California’s program is based on the principle that the motor vehicle must be controlled and that sewage no longer can be dumped into the air, if the public health is to be preserved.     

On-Road Motor Vehicle Emissions and Fuel Consumption in Urban Driving Conditions

ABSTRACT

This paper reports on the analysis of on-road vehicle speed, emission, and fuel consumption data collected by four instrumented vehicles. Time-, distance-, and fuel-based average fuel consumption, as well as CO, HC, NO_x, and soot emission factors, were derived. The influences of instantaneous vehicle speed on emissions and fuel consumption were studied. It was found that the fuel-based emission factors varied much less than the time- and distance-based emission factors as instantaneous speed changed. The trends are similar to the results obtained from laboratory tests. The low driving speed contributed to a significant portion of the total emissions over a trip. Furthermore, the on-road data were analyzed using the modal approach. The four standard driving modes are acceleration, cruising, deceleration, and idling. It was found that the transient driving modes (i.e., acceleration and deceleration) were more polluting than the steady-speed driving modes (i.e., cruising and idling) in terms of g/km and g/ sec. These results indicated that the on-road emission measurement is feasible in deriving vehicle emissions and fuel consumption factors in urban driving conditions.     

Development of the crop residue and rangeland burning in the 2014 National Emissions Inventory using information from multiple sources

Biomass burning has been identified as an important contributor to the degradation of air quality because of its impact on ozone and particulate matter. One component of the biomass burning inventory, crop residue burning, has been poorly characterized in the National Emissions Inventory (NEI). In the 2011 NEI, wildland fires, prescribed fires, and crop residue burning collectively were the largest source of PM_2.5. This paper summarizes our 2014 NEI method to estimate crop residue burning emissions and grass/pasture burning emissions using remote sensing data and field information and literature-based, crop-specific emission factors. We focus on both the postharvest and pre-harvest burning that takes place with bluegrass, corn, cotton, rice, soybeans, sugarcane and wheat. Estimates for 2014 indicate that over the continental United States (CONUS), crop residue burning excluding all areas identified as Pasture/Grass, Grassland Herbaceous, and Pasture/Hay occurred over approximately 1.5 million acres of land and produced 19,600 short tons of PM_2.5. For areas identified as Pasture/Grass, Grassland Herbaceous, and Pasture/Hay, biomass burning emissions occurred over approximately 1.6 million acres of land and produced 30,000 short tons of PM_2.5. This estimate compares with the 2011 NEI and 2008 NEI as follows: 2008: 49,650 short tons and 2011: 141,180 short tons. Note that in the previous two NEIs rangeland burning was not well defined and so the comparison is not exact. The remote sensing data also provided verification of our existing diurnal profile for crop residue burning emissions used in chemical transport modeling. In addition, the entire database used to estimate this sector of emissions is available on EPA’s Clearinghouse for Inventories and Emission Factors (CHIEF, http://www3.epa.gov/ttn/chief/index.html).Implications: Estimates of crop residue burning and rangeland burning emissions can be improved by using satellite detections. Local information is helpful in distinguishing crop residue and rangeland burning from all other types of fires.