Final Report CRC Project E 24 1 Measurement of Exhaust Particulate Matter Emissions from In Use Light Duty Motor Vehicles in the Denver, Colorado Area 03/ 16/ 98 Prepared for: Timothy C. Belian, Deputy Director Coordinating Research Council 219 Perimeter Center Parkway, Suite 400 Atlanta, Georgia 30346 1301 Prepared by:

Steven H. Cadle, Patricia Mulawa and Eric C. Hunsanger General Motors R& D Center MD 480 106 269 Warren, MI 48090 9055 Ken Nelson, Ronald A. Ragazzi, Richard Barrett, and Gerald L. Gallagher Colorado Department of Public Health and Environment Air Pollution Control Division 15608 E. 18th Ave. Aurora, CO 80011 Douglas R. Lawson Cooperative Institute for Research in the Atmosphere Colorado State University Fort Collins, CO 80523 Kenneth T. Knapp U. S. Environmental Protection Agency MD 46 Research Triangle Park, NC 27711 Richard Snow Clean Air Vehicle Technology Center, Inc Table of Contents Executive Summary .................................................................................................................... i List of Abbreviations and Acronyms Used in this Report ........................................................ vi 1. Introduction .......................................................................................................................... 1 2. Experimental ......................................................................................................................... 5 Vehicle recruitment ................................................................................................................. 5 Vehicle inspection ................................................................................................................... 7 Vehicle testing......................................................................................................................... 7 Gaseous emissions .................................................................................................................. 8 PM emissions........................................................................................................................ 10 Sample analysis .................................................................................................................... 11 Fuel ...................................................................................................................................... 13 Smoking vehicle population................................................................................................... 13 3. Quality Assurance/ Quality Control .................................................................................... 15 Site correlations .................................................................................................................... 15 Emissions variability............................................................................................................. 17 Filters ................................................................................................................................... 21 Carbon measurements ........................................................................................................... 23 Teflon Pallflex comparisons .................................................................................................. 26 4. Emission Rates of PM and Regulated Gaseous Pollutants.................................................. 30 Vehicles ................................................................................................................................ 30 FTP emission rates of regulated pollutants............................................................................. 31 IM240 emission rates of regulated pollutants ......................................................................... 32 Idle test emission rates and concentration............................................................................... 32 PM FTP emission rates ......................................................................................................... 33 Comparison of PM and HC FTP emission rates ..................................................................... 36 IM240 PM emission rates...................................................................................................... 37 5. Particle Number and Size ................................................................................................... 55 Particle number ..................................................................................................................... 55 Particle size distributions....................................................................................................... 58 6. Chemical Composition of the Particulate Matter................................................................ 69 Carbon.................................................................................................................................. 69 Sulfate and nitrate emission rates........................................................................................... 71 Fuel sulfur ............................................................................................................................ 77 XRF elements ....................................................................................................................... 79 Comparison of outdoor and indoor composition ..................................................................... 84 Polynuclear aromatic hydrocarbons ....................................................................................... 85 PAH hazardous air pollutants................................................................................................ 99 Steranes/ hopanes................................................................................................................. 100 7. Emissions Inventory.......................................................................................................... 136 8. Conclusions.......................................................................................................... ............. 139 Acknowledgments/ References................................................................................................ 140 Appendix A. Vehicle Recruitment Letters and Vehicle Inspection Form.............................. A. 1 Appendix B. Vehicle Descriptions.......................................................................................... B. 1 Appendix C. Correction of EPA Winter Regulated Pollutant Data ..................................... C. 1 Appendix D. Visual Observation of the Frequency of Smoking Vehicles ............................. D. 1 Appendix E. University of Denver Remote Sensing Observation of Smoking Vehicles ....... E. 1 Appendix F. Emission Rate Statistics ................................................................................... F. 1 Appendix G. Idle Test Data .................................................................................................. G. 1 i Executive Summary A vehicle emissions study was conducted in the Denver, Colorado area in July August of 1996 and in January February of 1997. The goals of the program were to measure exhaust particulate matter ( PM) emission rates from in use light duty gasoline and diesel vehicles, to obtain representative particle size distributions, to chemically characterize the PM, and to compare the results to those from PART5, the current Federal mobile source PM emission factor model. The EPA anticipates using these results and those from two companion CRC studies to assist in a planned revision of the PART5 model. In addition, results of the chemical characterization of the collected PM are being provided to the Northern Front Range Air Quality Study ( NFRAQS) for use in source apportionment. Study participants were the Colorado Department of Public Health and Environment ( CDPHE), the U. S. Environmental Protection Agency, the General Motors R& D Center, and Colorado State University. Chemical analyses were performed under subcontract by the Desert Research Institute ( DRI). The study was funded by the CRC and the DOE, through the National Renewable Energy Laboratory and by the NFRAQS. It also benefited from in kind contributions from all the participants. Total Petroleum provided free gasoline coupons for use as an incentive in vehicle recruitment.

Light duty vehicles were recruited in six categories: 1991 96 gasoline, 1986 90 gasoline, 1981 85 gasoline, 1971 80 gasoline, 1971 or newer smoking gasoline, and 1971 or newer diesels. Vehicles were soaked overnight before testing on a chassis dynamometer using the Urban Dynamometer Driving Schedule of the Federal Test Procedure ( FTP). Testing was done with the vehicles in as received condition, i. e. without preconditioning or fuel changes. The mandatory oxygenated fuel program was in effect during the winter portion of the study. The FTP test was followed, in sequence, by an IM240 test and a no load idle test. Regulated emissions and PM 10 samples ( particulate matter smaller than 10 µ m in diameter) were collected for all three FTP phases and the IM240. PM 10 samples were not collected during the idle test. During the summer portion of study, 111 vehicles were tested once. During the winter portion of the study, 84 different vehicles were tested twice, once on the CDPHE dynamometer located indoors at a temperature of 60 ° F, and once outdoors on the EPA transportable dynamometer at the prevailing ambient temperature. Winter outdoor testing was done on vehicles soaked overnight outdoors.

Quality assurance/ quality control ( QA/ QC) procedures included comparisons of calibration gases for the two test sites, testing of a correlation car at the two test sites, repeat of the FTP for every 10th vehicle, repeat of every 10th IM240, collection of duplicate filter samples, analysis of filter samples for deposit homogeneity, and collection of backup filters to assess the magnitude of adsorption of organic carbon on filters.

Average emission rates for the regulated emissions and exhaust PM 10 are summarized in Table 1. FTP PM emission rates for the 1991 97 gasoline vehicles were very low, averaging 2.8 mg/ mi in the summer and 3.7 mg/ mi in the winter indoors. The PM emission rate increased with vehicle age to an average of 95.5 mg/ mi in the summer and 54.2 mg/ mi in the winter indoors for the 1971 80 vehicles. FTP PM emission rates for ii vehicles tested outdoors in the winter were higher than those indoors. All of the increase occurred during the cold start portion of the test.

Table 1. Average FTP Regulated and PM 10 Emission Rates Period Category Number HC CO NOx PM g/ mi mg/ mi Summer 1991 96 20 0.24 2.35 0.42 2.82 Summer 1986 90 22 1.03 14.7 1.32 44.4 Summer 1981 85 25 2.7 35.9 1.54 47.4 Summer 1971 80 25 6.08 62.6 2.46 95.5 Summer Smoker 9 3.59 38.8 1.88 225 Summer Diesel 10 ND 3.99 4.57 811 Winter indoor 1991 96 10 0.56 6.74 0.51 3.51 Winter indoor 1986 90 14 0.63 9.23 1.44 11.8 Winter indoor 1981 85 16 2.57 35.7 2.76 35.9 Winter indoor 1971 80 16 2.78 44.3 2.11 54.2 Winter indoor Smoker 15 4.96 52.6 2.28 395 Winter indoor Diesel 12 0.82 1.94 1.73 460 Winter outdoor 1991 96 9 1.02 11.6 0.53 24.9 Winter outdoor 1986 90 14 1.06 15.5 1.61 28.5 Winter outdoor 1981 85 16 3.39 38.7 2.31 48.2 Winter outdoor 1971 80 16 4.49 52.1 2.01 82.6 Winter outdoor Smoker 15 8.71 65.6 2.29 434 Winter outdoor Diesel 12 1.1 1.76 1.55 503 The average PM 10 emission rates for smoking gasoline vehicles were 225 mg/ mi in the summer and 395 mg/ mi in the indoor winter tests. The difference is primarily attributable to better identification and recruiting of smoking vehicles in the winter. Diesel vehicles averaged 811 mg/ mi in the summer and 460 mg/ mi in the indoor winter tests. There were significant differences in vehicle age and class between the summer and winter diesel vehicles.

FTP HC and PM 10 emission rates were compared since other studies have used HC emission rates as a surrogate for PM emission rates. Correlations between HC and PM 10 for individual vehicles were weak, with R2< 0.25. The correlation was much better ( R2= 0.89) when the averages for each gasoline vehicle category during the summer and the winter were compared.

FTP and IM240 emission rates of HC, CO, and NOx were well correlated with R2 values ranging from 0.72 to 0.95. Correlations between FTP and IM240 PM 10 emission rates ranged from 0.97 for all vehicles in the summer study to 0.53 for only the non smoking gasoline vehicles in the summer study. These results suggest that the IM240 is effective in identifying high PM 10 emission rate vehicles.

Particle size distributions were obtained from 33 vehicles using impactors. Results are predominantly from the high PM 10 emitting vehicles, since there is insufficient mass from iii low emitting PM 10 vehicles for accurate impactor measurements. The mass median diameter ( MMD) for non smoking gasoline vehicles was 0.13 µ m. On average, 91% of the PM mass was present in particles 2.5 µ m or smaller. Both the smoking vehicles and the diesel vehicles had a MMD of 0.18 µ m, with 97% of the mass being emitted in particles 2.5 µ m or smaller.

The number of particles larger than 0.01 µ m in diameter was measured continuously during FTP tests of 92 gasoline vehicles and 12 diesel vehicles. The data showed that PM emissions are very dynamic, tending to occur during changes in throttle, much like the gas phase emissions. This has implications for tunnel and roadside studies of in use PM emissions. Integrated particle counts were moderately well correlated with PM mass for the summer study ( R2 = 0.70), but were not as well correlated for the winter study ( R2 = 0.39).

Chemical analysis was performed on a representative subset of filter samples. Only outdoor samples were analyzed for the winter since these are most representative of actual fleet emissions. " Organic" carbon ( OC) and " elemental" carbon ( EC) were analyzed by the thermal optical reflectance method. Soluble sulfate and nitrate were determined by ion chromatography. X ray fluorescence ( XRF) was used for elemental analysis. Combined filter and PUF/ XAD cartridge samples were solvent extracted. The PUF/ XAD cartridge is used behind the particle filter to collect volatile and semi volatile organic compounds. Extracts were analyzed by gas chromatography/ mass spectrometry for polynuclear aromatic hydrocarbons ( PAH) and for steranes and hopanes.

On average, 90% of the PM emitted from the vehicles is carbonaceous material, where carbonaceous material is defined as the sum of the OC ( multiplied by 1.2 to account for other elements such as hydrogen and oxygen) and the EC. The OC and EC fractions of the carbonaceous material are highly variable from vehicle to vehicle. The OC fraction tends to increase with increasing PM emission rate for gasoline vehicles, reaching more than 90% of the carbonaceous material for some smoking vehicles. The OC fraction is also higher on average during FTP phase two than phase one or three. Diesel vehicles average approximately 50% OC.

Sulfate emission rates were low, with vehicle category averages for the gasoline vehicles ranging from 0.13 to 1.7 mg/ mi. Diesel sulfate emissions were higher, averaging 5.6 mg/ mi in the summer and 2.7 mg/ mi in the winter. Fuel sulfur content in the Denver area was 0.036 and 0.034 wt. %, respectively, for regular grade gasoline and # 2 diesel fuel in the summer and 0.023 and 0.034 wt. %, respectively, for regular grade gasoline and # 2 diesel fuel in the winter. A comparison of the sulfur emitted as sulfate ( measured by ion chromatography) to the total sulfur ( measured by XRF) indicated that approximately 40% of the sulfur present in the PM was in the form of water soluble sulfate.

Forty elements were measured by XRF, 12 of which were commonly detected. These were magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, calcium, iron, copper, zinc, bromine and lead. Several of these compounds are present due to the consumption iv of engine oil. The average emission rates for the sum of the elements ranged from 0.27 to 3.6 mg/ mi for the gasoline vehicles. Their maximum percent contribution to the average PM emission rate for the vehicle categories was nine percent for the 1991 96 gasoline summer vehicles. This elemental data will be used as part of the vehicle emissions profile for source apportionment. Several of the metals are also of interest as air toxics. In this regard, some of the measurements showing less than detectable quantities of metals are as important as the measurements on more abundant species. Finally, the emission rates of transition metals are of interest because they have been postulated to play a role in PM health effects.

Sixty five PAH compounds were measured. The primary purpose was to contribute to the mobile source profile for source apportionment studies. However, it is recognized that PAHs are also of interest as hazardous air pollutants ( HAPs). Essentially all of the measured compounds were emitted by all vehicles tested. Considerable variability was found in the relative emission rates of the individual compounds from vehicle to vehicle, between FTP phases, and between some vehicle categories. The largest difference was between the diesels and gasoline vehicles, with the diesels emitting relatively lower naphthalene and methyl naphthalenes than the gasoline vehicles. Unfortunately, these compounds are present in the gas phase and do not appear to correlate well with the PM. A rigorous analysis of the variability of the emission rates and their potential usefulness as source receptor fitting compounds is beyond the scope of this study. Their utility will be judged as part of the NFRAQS study.

Hopanes and steranes are two classes of hydrocarbons found in motor oil. It has been suggested by others that these compounds can serve as tracers for motor vehicle PM in the atmosphere, with the possibility that they can be used to distinguish between diesel and gasoline PM. Eighteen hopane and sterane compounds were measured. Emission rates were generally very low, frequently in the microgram per mile range. The compounds were emitted by all of the tested vehicles, although some compounds were frequently below detection limits for the lower PM emitting vehicles. There was little difference in the relative emission rates of these compounds between diesel, smokers, or gasoline vehicles. It is concluded that they may be excellent tracers for mobile source PM if they are not emitted by other sources, but they can not be used to distinguish between diesel and gasoline PM emissions.

A simple light duty PM 10 emissions inventory estimate was prepared for the Colorado Front Range area using the emission rates determined in this study and daily vehicle miles traveled data supplied by the State of Colorado. Summer and winter PM 10 emissions are estimated at 1.5 and 1.7 tons/ day, for the summer and winter, respectively. Fleet average PM 10 emission rates are 33.9 and 38.4 mg/ mi, respectively, for the summer and winter. Non smoking light duty gasoline vehicles are the major source of the particles. Major uncertainties remain in the number of smoking vehicles on road, and in the low temperature PM emission rate for late model gasoline vehicles. v Results of the comparison of data obtained in this program to PART5 model predictions are not available at this time. The CRC and the DOE together with the State of Texas and the South Coast Air Quality Management District are sponsoring companion studies of inuse vehicle PM emissions at the Southwest Research Institute and the University of California at Riverside's College of Engineering Center for Environmental Research and Technology ( CE CERT). A report comparing the results of all three studies will be prepared after the final reports from each study are available. vi List of Abbreviations and Acronyms Used in this Report A/ O AQIRP Auto/ Oil Air Quality Improvement Research Program AAMA American Automobile Manufacturers Association AIR Secondary air injection CARB California Air Resources Board CAWRSS Clark and Washoe Remote Sensing Study CDPHE Colorado Department of Public Health and Environment CO Carbon monoxide CO2 Carbon dioxide CRC Coordinating Research Council D Diesel vehicle DOE U. S. Department of Energy DRI Desert Research Institute EAA Electrical aerosol analyzer EC " Elemental" carbon as measured by thermal/ optical reflectance method EMFAC7G Version 7G of California's mobile source emission model EMFAC EPA U. S. Environmental Protection Agency FTP Federal Test Procedure G Gasoline vehicle g/ mi Grams per mile GC/ MS Gas chromatograph/ mass spectrometer GM General Motors H High particle emitting vehicle HAP Hazardous air pollutant HC Hydrocarbons I/ M Motor vehicle inspection/ maintenance program IARC International Agency for Research on Cancer IC Ion chromatography IM240 Emissions test for motor vehicles lasting 240 seconds L Low particle emitting vehicle LD Light duty LDD Light duty diesel vehicle LDG Light duty gasoline vehicle Lpm Liters per minute M Medium particle emitting vehicle mg/ mi Milligrams per mile ML Medium low particle emitting vehicle MMD Mass median diameter MOUDI Micro orifice uniform deposit impactor ND Not detected NFRAQS Northern Front Range Air Quality Study NIST National Institute of Standards and Technology vii NOx Oxides of nitrogen OAQPS EPA Office of Air Quality Planning and Standards OC " Organic" carbon as measured by thermal/ optical reflectance method PAH Polynuclear aromatic hydrocarbon compounds PART5 EPA's mobile source model for particle emissions PM Particulate matter PM 10 Particulate matter having an aerodynamic diameter less than 10 µ m PM 2.5 Particulate matter having an aerodynamic diameter less than 2.5 µ m POM Polycyclic organic matter Ppm Parts per million PpmC Parts per million carbon PUF Polyurethane foam used for measuring semi volatile organic compounds QA/ QC Quality assurance/ quality control RTP Research Triangle Park, North Carolina S Smoking vehicle SO2 Sulfur dioxide Std. Dev. Standard deviation TC Total carbon TWC Three way catalyst TOR Thermal/ optical reflectance method UDDS Urban dynamometer driving schedule VMT Vehicle miles traveled XAD A polymer resin used for measuring semi volatile organic compounds XRF X ray fluorescence 1 1. Introduction Atmospheric particulate matter has long been a concern because it reduces visibility, can cause damage to exposed surface materials, soils monuments and other architectural structures, and can cause health effects. Health effects concerns have increased recently due to epidemiological studies that have correlated increases in human morbidity and mortality in several cities throughout the country to PM 2.5, particulate matter with a diameter of 2.5 micrometers or less ( Dockery and Pope, 1994; Health Effects Institute, 1995; Kaiser, 1997). In response, the EPA has retained the PM 10 standard while setting new national ambient air quality standards for PM 2.5 of 65 µ g/ m3 for 24 hr and 15 µ g/ m3 as an annual average. The new standards will increase the emphasis on reducing combustion related particles since they are predominately smaller than 2.5 µ m.

Vehicles contribute to the atmospheric particulate burden via three processes: 1) direct exhaust, brake wear, and tire wear emissions, 2) reentrainment of dust, and 3) through the secondary formation of particulate matter from the atmospheric chemistry of HC, NOx, and SO2 emissions. Nationally, all highway vehicles account for a very small proportion of the total PM 10. However, in urban areas, where population exposures are the highest, the impact of all three processes makes vehicles a major PM 10 source. Vehicle exhaust PM emissions and tire wear PM emissions are mostly carbonaceous matter. The state ofknowledge regarding vehicle emissions contributions to the carbonaceous portion of the ambient PM 2.5 in the South Coast Air Basin ( Cass, 1997; Rykowski and Hrebenyk, 1997) has recently been reviewed. Diesels were found to be the largest source, followed by meat cooking, wood smoke, gasoline vehicle emissions, and road dust. The relative order of importance of the sources varies somewhat depending on the analysis method used.

There is little information regarding the primary particulate emission rates from current inuse light duty vehicles. Measurements of tire and brake wear emission rates were last reported in the 1970' s. A few measurements of exhaust particulate emission rates have been reported recently. Sagebiel et al. ( 1997) measured PM 10 emission rates from 23 inuse vehicles that were recruited as high HC or CO exhaust emitters during the 1994 Clark and Washoe Remote Sensing Study ( CAWRSS) conducted in Nevada. These vehicles were emission tested at roadside on the IM240 test cycle with the EPA transportable chassis dynamometer. Particulate emission rates were readily determined. The average rate for non smoking vehicles was 0.051 grams per mile ( g/ mi), while the rate for those identified as having visible smoke was 0.558 g/ mi. Given the success of this study, additional measurements were made during 1995 in Orange County, CA. ( Cadle et al., 1997; Lawson et al., 1996). Again, vehicles were recruited on the basis of having high remote sensing readings of CO or HC, and were tested at roadside using the EPA transportable chassis dynamometer and the IM240 test cycle. Eighty six non smoking vehicles had an average PM 10 emission rate of 0.094 g/ mi, while 17 smokers had an average emission rate of 0.40 g/ mi. In both of these studies correlation between PM 10 and HC emissions was poor. Chemical characterization of the collected PM 10 was also conducted. 2 A third study ( Mulawa et al., 1997) was conducted in Alaska during the 1994/ 95 winter. Ten properly functioning light duty vehicles were recruited and tested on the EPA transportable dynamometer using the FTP cycle. Tests were conducted at three temperatures, with two fuels. Three of the vehicles were retested at the EPA RTP facility. A large fraction of the Alaska data was invalidated due to problems operating at very low temperatures and the inexperience of the local personnel who operated the equipment. Therefore, most of the conclusions were based on the results from the three vehicles tested at EPA. It was found that total PM emissions increase with decreasing temperature, that most of the particle mass was emitted during the cold start portion of the test, that there was a good correlation between PM 10 emission rates and the HC emission rate, and that use of an oxygenated fuel reduced PM 10 emission rates.

The limited data available from FTP tests of properly functioning vehicles indicate that modern, low mileage vehicles have low PM emission rates. The three aforementioned vehicles tested in the Alaska study averaged 0.003 g/ mi PM at room temperature. Twelve 1986 1990 light duty vehicles measured by Mulawa and Dasch ( 1995) averaged 0.007 g/ mi total PM. Most recently the Environmental Research Consortium tested 13 low mileage 1994 1998 model year vehicles and 6 high mileage 1995 1998 vehicles on the FTP using California phase II fuel ( Chase et al., 1998). The high mileage vehicles had average odometer readings of 94,000 miles. The low mileage cars and trucks had average total PM emission rates of 0.0006 and 0.0012 g/ mi, respectively. The three high mileage cars and 3 high mileage trucks had average total PM emission rates of 0.0008 and 0.0016 g/ mi, respectively.

In contrast, Durbin et al. ( 1998) studied smoking vehicles in the South Coast Air Basin. The study did an intensive visual survey of on road vehicles and concluded that between 1.1 and 1.8% of the light duty fleet emits some visible smoke, and that these are composed mainly of both gasoline and diesel vehicles that are 8 to 18 years old. Twentythree smoking vehicles that were tested on the FTP had an average emission rate of 0.399 g/ mi.

The contribution of exhaust, tire, and brake primary particulate emissions from the onroad fleet are estimated using the EPA PART5 model, or the CARB EMFAC7G model. The EMFAC7G model made major revisions in the light duty vehicle PM emission estimates compared to earlier versions of the model, largely incorporating methodologies and emission rates used in PART5. The algorithms used in these models are much simpler than those used for exhaust gaseous emissions ( Rykowski et al, 1996). They do not account for temperature, altitude, start emissions vs. running emissions, fuel composition ( except sulfur), mileage, emitter category, etc. This is due to a lack of data on the effects of these parameters. Light duty gasoline carbonaceous PM emission rates are provided as a function of four vehicle types; non catalyst vehicles, pre 1981 catalyst vehicles with and without AIR, and post 1980 catalyst vehicles. The light duty gasoline fleet average post 1980 catalyst vehicle emission rate of carbonaceous material is 0.004 g/ mi. The models also calculate sulfate emission rates for light duty gasoline vehicles as a function of 3 catalyst, AIR ( secondary air injection), and fuel sulfur content. The SO2 conversion factors appear to date from the late 1970' s. A typical sulfate emission rate for a catalyst vehicle without AIR is 0.005 g/ mi, and with AIR it is 0.016 g/ mi. The PART5 default light duty gasoline fleet average total PM exhaust emission rates for 1995 and 2010 are 0.014 and 0.012 g/ mi, respectively. For the draft EMFAC7G, the corresponding rates are 0.014 and 0.010 g/ mi, respectively.

The accuracy of the PART5 and EMFAC7G models is unknown. The failure to include high emitters will result in a significant underestimation of the light duty fleet average PM 10 emission rate. For example, at the two sites studied in Orange County, the recruited light duty gasoline vehicles had an average PM emission rate of 0.14 g/ mi, and represented approximately 9% of the fleet. Almost all of the emissions were carbonaceous material ( Cadle et al., 1997). Thus, these vehicles alone would contribute 0.013 g/ mi of carbonaceous material to the light duty gasoline fleet average PM emission rate at that location. In addition, the models do not separate cold start emissions from the total emission rate and do not account for the effect of ambient temperature. Properly functioning vehicles emit most of the exhaust particulate mass during the cold start, and the cold start rate is a function of ambient temperature. Recent activity studies in California suggest that the frequency of cold starts may be significantly underpredicted. Thus, the models may be underestimating PM emissions from properly functioning vehicles, especially at low temperatures. On the other hand, the models may overpredict sulfate emissions, since recent data suggest little tendency for current catalysts to produce sulfate. In addition, the models do not give credit for reductions in emissions from vehicles with improved emission control technology in future years. Thus, future year projections may well overestimate PM 10 exhaust emissions.

Two approaches can be taken to improve our knowledge regarding the impact of lightduty vehicle exhaust PM emissions. The first is the bottom up approach in which large numbers of vehicles are randomly recruited and emission tested under a variety of conditions. Given the highly skewed distribution of PM emission rates from in use vehicles, it would be necessary to recruit a very large number of vehicles to obtain an accurate distribution. This is not practical within the scope of this study. However, given the dearth of information on emission rates from in use light duty vehicles, the testing of even a modest number of vehicles will provide a significant improvement in our predictive capabilities, and may even be sufficient to conclude that the emissions are not significant compared to other sources. The second approach is the top down source apportionment method. This methodology utilizes chemical source signatures to separate the various sources of the observed atmospheric PM 10. It may be possible to separate the light and heavy duty contributions to atmospheric PM with this approach. Source profiles utilizing a combination of trace species, including some of the organic particulate compounds, are available. However, these profiles are based on limited numbers of samples and have not been independently verified. To some extent, this top down approach suffers from the same problem as the bottom up approach, in that source samples must be collected from a large enough set of vehicles to ensure that the source signature is robust. The top down approach also suffers from the inability to distinguish between on road and off road 4 combustion sources. The ideal situation will be when both the top down and bottom up methods agree on the relative importance of the emissions.

This program was designed to provide information for both the bottom up and top down approaches to assessing the impact of exhaust emissions of light duty vehicles on PM air quality. A total of 173 in use light duty gasoline ( LDG) and 22 light duty diesel ( LDD) vehicles were tested in as received condition on the Urban Dynamometer Driving Schedule ( UDDS) of the FTP and the IM240 driving cycle. PM 10 emission rates were measured for each of the three phases of the FTP. A subset of the FTP tests included impactor particle size distributions, continuous particle counts, and the determination of the chemical composition of the PM. Eighty four of the vehicles were tested during the winter at two temperatures. Results are compared to current emission factor model predictions, and will be available for use in future PM emissions model updates. It should be noted that the Coordinating Research Council together with the Department of Energy, the South Coast Air Quality Management District, and the State of Texas is funding two related studies that are making similar measurements on light duty vehicles. CE CERT ( University of California's College of Engineering Center for Environmental Research and Technology) will test at least 100 LDG and 19 LDD vehicles recruited in the South Coast Air Basin and the Southwest Research Institute will test 60 LDG and 8 LDD vehicles recruited in the San Antonio, TX area. Altogether a total of at least 333 LDG and 49 LDD vehicles will be tested.

This program is also part of the State of Colorado's Northern Front Range Air Quality Study ( NFRAQS), which was conducted during the winter of 1996, the summer of 1996 and the fall winter of 1996 1997. The overall goals of the study are: 1) to determine the sources of existing air pollution in the Denver urban region, attributing to each identified source or source category an estimate of its emissions of particles, particulate precursors, and other substances; and 2) to collect data necessary to support informed decisionmaking for the future, including measurement of existing exposure levels and the assessment of how best to meet state and visibility goals and federal air quality standards. The first policy relevant objective of the study is to do a source apportionment of carbonaceous particles in the NFRAQS study region. The Desert Research Institute, which is the prime NFRAQS contractor, will use the chemical compositions determined in this study to create source profiles for both LDG and LDD vehicles. Separate NFRAQSsponsored studies are collecting samples of heavy duty diesel vehicle emissions, woodburning emissions, and meat cooking emissions. Profiles will be generated from the chemical analysis results from each of these source types. It is hoped that the profiles will be sufficiently unique to enable a source apportionment of the carbonaceous PM in the NFRAQS region. Descriptions of the profiles and the results of the source apportionment study will be given in the NFRAQS final report. 5 2. Experimental The study was conducted at the Colorado Department of Public Health and Environment Aurora Emissions Technical Center, in the eastern Denver metropolitan area. The summer portion of the study was conducted in July and August of 1996, while the winter portion was conducted in January and February of 1997. Vehicles were tested once in as received condition during the summer portion of the study. During the winter, vehicles were tested twice in as received condition, once at 60 ° F and once at the prevailing ambient temperature. Details of the vehicle recruitment, inspection, testing, and sampling follow.

Vehicle recruitment. A goal of the study was to obtain, as best as possible, an unbiased set of vehicles representing the in use, on road, light duty vehicle fleet in the Northern Front Range area of Colorado. It was anticipated that the fleet PM emissions would be dominated by three categories of vehicles, smoking gasoline vehicles, diesel vehicles, and poorly maintained or malfunctioning vehicles. The latter are expected to occur most frequently in the older vehicle population. Thus, to ensure that a reasonable number of the higher emitting vehicles were acquired for testing, the total number of vehicles to be tested was allocated to six categories. These categories were 1991 1997 gasoline, 1986 1990 gasoline, 1981 1985 gasoline, 1971 1980 gasoline, 1971 or newer smoking gasoline, and 1971 or newer model year diesel powered vehicles. The 1971 cutpoint was taken because current emission factor models generally consider emissions from the last 25 years of vehicles. It is recognized that the 1971 1980 gasoline category includes both catalyst and non catalyst equipped vehicles. The 1981 model year is when three way catalyst technology was first introduced. In 1986, significant improvements were made in vehicle emissions control systems. Smoking gasoline vehicles, which are vehicles with visible smoke while driven on the road, and diesels are a very small percentage of the in use fleet, but are expected to contribute substantially to the fleet PM emissions. A random recruitment of the 195 vehicles tested in this program might not have captured any vehicles from these two categories. Therefore, special efforts were made to obtain these vehicles. As a secondary goal, a target of 70% light duty ( LD) cars and 30% LD trucks was set for each category. These percentages of LD cars and trucks are representative of the Denver area motor vehicle fleet.

Initial plans were to recruit vehicles by having the State Police stop on road vehicles in the Denver area. The drivers would then be solicited at roadside to volunteer their vehicle for the testing program. Unfortunately, this approach was prevented by last minute legal questions. Therefore, vehicles were recruited from customers at two local merchants, Cub Foods ( a large discount supermarket) and K Mart. Recruitment was accomplished by setting up tables with large signs requesting customer participation. Drivers were offered an incentive of $ 100, a $ 25 coupon from Total Petroleum redeemable for goods or fuel, and a free rental car during the time of testing or its cash equivalent. This approach worked well. Because of insufficient staffing, it was not possible to keep records of the number of acceptances/ rejections, but it is estimated that 40% of the drivers who inquired about the program accepted the offer. Of those who accepted the offer to participate in the program at the two locations, about 30 percent were rejected on the spot because the 6 vehicles were not mechanically suitable for dynamometer testing. The most common reasons for rejection were exhaust system leaks and bald tires. Once the vehicles arrived at the Aurora Emissions Technical Center, CDPHE personnel gave them a thorough inspection that resulted in the rejection of 20 percent of those vehicles. While it is logical to assume that vehicles rejected from the program due to a poor state of repair may have higher average emissions than the accepted vehicles, we are not aware of any study that has quantified that effect.

The one difficulty with this approach was that suitable numbers of the oldest vehicles were not recruited in a timely manner. It had been decided to test all the oldest vehicles towards the end of the program in order to minimize contamination of the exhaust sampling system by high PM emitters. Unfortunately, it turned out that these were the most difficult vehicles to recruit, because so many of them had mechanical problems and there are relatively few of them in the vehicle population. Therefore, an advertisement soliciting volunteers for the program was run for one issue in the Aurora Sentinel, a local paper. At approximately the same time, television news coverage of the program was broadcast. These two events resulted in a large number of calls from interested volunteers. Between 30 and 50 vehicles were recruited from these calls.

It was planned to recruit smoking vehicles through the City and County of Denver's smoking vehicle program. In this program, trained personnel from the City and County of Denver record license plate numbers of in use smoking vehicles. The registered owners of those vehicles are notified by certified mail that they must have their vehicle repaired within a specified period of time and show evidence to inspectors that the necessary repairs have been made, or they will be required to appear in court. Owners of vehicles that had been identified within the program were sent a letter asking them to volunteer their vehicle for testing. This approach met with very limited success ( six recruited vehicles) during the summer portion of the study. Therefore, the aforementioned advertisement was also used to solicit smoking vehicles. In all, only 9 of the planned 20 smoking vehicles were recruited during the summer, and one of these was through a personal contact. For the winter portion of the study, the City and County of Denver approach was even less successful. One vehicle was recruited by the City and County of Denver, five vehicles were recruited as a result of letters sent to Basic I/ M program emissions inspection stations, and the remaining nine vehicles were recruited either by word of mouth or from a list of vehicles failing the smoke portion of the enhanced I/ M inspection ( a copy of the letter sent to owners of Basic I/ M stations is included in Appendix A).

No diesel vehicles were recruited from motorists shopping at the local merchants. For the summer study, diesels were recruited by CDPHE personnel contacting local repair shops, used vehicle dealers, and diesel service businesses. For the winter, a cash incentive was provided to the owners/ managers of diesel inspection stations to identify and recruit diesel vehicles from the local diesel I/ M inspection lanes. A copy of the letter sent to the diesel inspection stations is included in Appendix A. Most of the diesels in the winter program came from these referrals, but one came from an owner who had participated in the 7 summer program with another diesel vehicle and heard of the winter program through word of mouth.

Table 2.1 gives the summer and winter recruitment targets for each vehicle category and the actual number of vehicles tested. The number of vehicles recruited for the winter was lower than that for the summer since these vehicles were tested twice. A description of every vehicle tested is given in Appendices B 1 through B 4.

Table 2.1. Number of Vehicles Recruited Category Summer Winter Planned Recruited Cars Trucks Planned Recruited Cars Trucks 1971 1980 25 25 18 7 15 17 11 6 1981 1985 25 25 19 6 15 16 12 4 1986 1990 20 22 14 8 10 14 8 6 1991 1996 20 20 14 6 10 10 7 3 Smoking 20 9 8 1 15 15 11 4 Diesel 10 10 3 7 10 12 9 3 Vehicle inspection. Recruited vehicles were driven by their owners to the Aurora Emission Test Facility, where they received a thorough inspection. The inspection accomplished three purposes. First, it was determined if the vehicle was in good enough condition to be tested on the chassis dynamometers. Vehicles were rejected if they had significant fluid leaks, if the exhaust system had leaks, if the tires were dangerously worn, or if the vehicle was judged to have such major mechanical problems that it could mechanically fail during testing. Second, vehicle information such as odometer reading, fuel grade, engine, transmission and emission control system was ascertained and recorded. Much of this information is presented in Appendix B. Third, body condition was recorded in the event damage occurred during vehicle testing. Appendix A contains a copy of one of the vehicle inspection sheets.

In seven cases during the winter portion of the study, a vehicle that was needed to complete a category, but had been rejected during inspection, was repaired so it could be tested. In each case, a portion of the exhaust system was repaired or replaced. The vehicles were then prepped on the dynamometer to ensure that their exhaust system had been conditioned and any forming oil present on new parts was removed. These are the only instances where a vehicle received dynamometer preparation. The seven repaired vehicles had the following WNFRAQS numbers: 312, 315, 332, 370, 375, 381 and 388, the latter two being diesels. Repairs were not expected to affect the vehicles emission. The repair costs ranged from $ 35 to $ 275, with an average cost of about $ 130.

Vehicle testing. Vehicles were tested as received, including the use of the tank fuel. Only in instances where insufficient fuel was present to complete the testing, was fuel added. The fuel added was a local commercial fuel. Immediately following acceptance for the study, each vehicle received an incoming two speed idle test for HC and CO. This was 8 followed by a soak period to bring all vehicle components to an equilibrium temperature.

During the summer, all vehicles were soaked indoors overnight at 72 ° F. Half the gasoline vehicles were tested on the CDPHE chassis dynamometer, while the other half were tested on the EPA transportable chassis dynamometer. All diesels in the summer were tested on the CDPHE dynamometer. Both dynamometers used 8.6" diameter dual rolls. The EPA dynamometer was located outdoors under a canopy. Vehicles tested outdoors were pushed from the soak area onto the dynamometer immediately before testing.

During the winter, all vehicles were tested twice, once on each dynamometer. Half the vehicles were tested indoors first, and half outdoors first. The indoor testing was done after a soak indoors at 60 ° F. The temperature was lowered from the standard FTP test temperature range to better reflect the maximum winter temperature in Denver and to minimize the influence evaporative emissions from high volatility winter fuels might have on the exhaust emissions. The outdoor testing was done after an overnight outdoor soak at ambient temperatures. The crankcase oil temperature of the vehicles was measured with a thermocouple immediately before testing. It was anticipated that oil temperature would be a better indicator of the vehicle condition at the time of testing than the ambient temperature. However, ambient temperature was also recorded.

The vehicles were driven on the UDDS of the FTP. This is the standard exhaust emissions test which has been used for both certification and emissions inventory development since 1975. It represents city driving in Los Angeles. There are three phases ( also referred to as bags) to the test that represent cold start, hot stabilized, and hot start operation. These phases are referred to as bags 1 3. After completion of the FTP, the vehicles were turned off for a few minutes, then restarted and an IM240 test was driven. The IM240 test cycle is used in the Denver area's enhanced inspection and maintenance program. It is started from idle with the vehicle in hot stabilized condition and lasts 240 seconds. It was designed to mimic the FTP. The purpose of conducting this test was to determine if it could be used as a short test to characterize PM emissions from light duty vehicles. Following the IM240, regulated emissions were measured at idle using a bagged idle test or its equivalent. The test was conducted at normal " as received" curb idle. For standard transmission vehicles the test was done in neutral. For automatic transmission vehicles, the test was conducted in drive. This was done for intersection modeling purposes by the CDPHE. No PM emissions were collected during the idle test. This report will not analyze the idle emissions data.

Gaseous emissions. Regulated emissions ( HC, CO and NOx) and CO2 were measured during all FTP and IM240 tests. Diesel vehicles require the use of a heated FID, which did not operate properly during the summer portion of the study. Therefore, no HC data are reported for the diesels tested during the summer. For the winter, the CDPHE heated FID worked well, and a heated FID was added to the EPA test site. The CDPHE measured gas phase emissions using the standard bag collection system. Their analyzer bench was replaced between the two studies. The EPA used modal dilute exhaust measurement, rather than bag collection. Their analyzers were operated on fixed ranges, 9 which limits their accuracy somewhat at very high and very low concentrations. During the winter, the dilution air for the EPA exhaust tunnel was preheated to 150 ° F and the tunnel was wrapped with insulation to ensure that water condensation was not a problem. In addition, a heated sampling line was used between the dilution tunnel and the trailer that housed the analytical instruments and data acquisition computer.

Near the end of the winter study, it was discovered that the pump on the EPA sample line had developed a leak approximately one third of the way through testing. A small leak in the pump was exacerbated by partial plugging of the filter protecting the pump. The filter plugging, which was probably caused by the testing of three smokers back to back, caused a large increase in the vacuum at the pump. A secondary effect of this problem was a decrease in response time. The timing and magnitude of the leak was corroborated by examining CO2 emission rates determined for bags 2 and 3 of the FTP and the IM240 at the CDPHE test site and the EPA test site on the same vehicles. If everything was operating properly, the emissions should be very similar. Bag 1 of the FTP was not included in the analysis since the cold start at different temperatures would be expected to influence CO2 emissions. The slope of the linear correlation for CO2 was 0.95 before the smokers were run, and 0.72 after the smokers were run. No trends in the leak rate with time could be observed. Based on this analysis, and flow tests of the leaking pump, all affected data from the EPA test site were reprocessed to account for the change in response time ( a 3 5% increase) and a leak of 25%. HC data for the diesels were not affected by this correction since the heated FID was operated with a separate pump. Also, PM samples were collected with a separate sampling system, and thus were not affected by this problem. More details on this correction are provided in Appendix C 1.

Figure 2.1 shows the difference in FTP composite CO2 emission rates between the CDPHE and EPA sites after the corrections were made. No corrections were made to runs 0 89 and 255 267, the latter being after the pump was replaced. On average, it is expected that the CO2 emission rate will be higher for the EPA site than the CDPHE site, due to the temperature difference. Figure 2.1 indicates that the differences are random up to run 182 and after the pump replacement before run 249. However, there is a consistent bias towards higher CO2 emission rates for runs 183 248. These can not be explained by the differences in ambient temperature. Since the CO2 rates are high, but within the variability of the other measurements, possible explanations include a decrease in the leak rate, an independent measurement problem with the CO2, or that the data are correct. The differences in the HC, CO and NOx emission rates for the same tests were examined for each FTP phase to determine if they showed the same pattern. Definite conclusions could not be drawn based on non parametric Wilcoxon tests, regressions, or t tests, in part because variability is generally higher for these species than for CO2. Therefore, it was not possible to determine if there was an independent measurement problem with the CO2. If however, all gaseous emission rates for runs 183 248 ( except diesel HC) are further adjusted by a 16% increase, the ratios of positive to negative differences between CDPHE and EPA measurements become more consistent over all tests for HC, CO and NOx as well as for CO2. We can not therefore discount the possibility that there are errors on the order of 16% with the gaseous emissions rates for runs 183 248, excluding the diesel HC 10 measurements. Such errors have no impact on the conclusions of this report. A more detailed examination of the differences is presented in Appendix C 2.

PM emissions. PM samples were collected through two isokinetic probes inserted into each of the dilution tunnels. These probes were connected to University Research Glassware PM 10 cyclones, which operated at a flow rate of 28.3 lpm. Flow rates were held constant with mass flow controllers and were checked periodically with a dry gas meter. Flow controller readouts were logged on data acquisition systems, with the exception of the EPA site in the summer, which relied on visual checks of the readout. Each cyclone was attached to a 26.5 cm long straight tube for flow straightening. The tube, in turn, was connected to a Y fitting which accommodated two filter holders. Solenoid valves activated by the test computer systems were used to switch between filters. Switching occurred at the end of phase 1 of the FTP to the phase 2 filter and at the end of phase 3 to the IM240 filter ( filter holders were changed during the soak period between phases 2 and 3 of the FTP).

PM 10 samples were collected simultaneously on both 37 mm diameter, 2.0 µ m pore size Gelman Teflo and 37 mm diameter Pallflex Tissue Quartz 2500 QAT UP filters. Quartz filters were prefired at 900 ° C for three hours to remove any carbon. Filter plugging problems were encountered during the summer for a few high emitting vehicles. Therefore, the 37 mm Teflo filters were replaced with either 47 mm Teflo filters or 37 mm or 47 mm T60A20 Pallflex filters for the high emitting gasoline vehicles and the diesels during the winter. A subset of tests was run with a vapor phase trap for polynuclear aromatic hydrocarbons ( PAH) placed behind the quartz filter. The trap consisted of 5 g of XAD 4 resin ( polystyrene/ divinylbenzene polymer) sandwiched between two polyurethane foam ( PUF) plugs. In addition, some tests were performed with back to back quartz filters and back to back Teflo/ quartz filter pairs to test for organic carbon adsorption. Both media blanks and field blanks of all filters and PUF/ XAD lots were retained and analyzed.

All Teflon and Pallflex filters were weighed on a microbalance after equilibration at constant temperature and humidity. Filters were stored in plastic Petri dishes in a refrigerator, and transported between laboratories using a cooler with blue ice packs. PUF/ XAD samples were stored in glass jars with a sheet of aluminum foil placed between the opening and the lid. These samples were also stored and transported cold.

Particle size distributions were determined with MSP micro orifice uniform deposit impactors ( MOUDI). The impactors were run on the CDPHE site only, since the physical arrangement of the EPA dilution tunnel made collection of impactor samples very difficult. The summer study used an eight stage impactor with a backup filter. The winter study used a ten stage impactor with a backup filter. The impactors were operated at an actual flow rate of 30.3 lpm. The particle size ranges for the individual stages were corrected for the reduced pressure at Denver's altitude. Uncoated aluminum foils were used as collection media. Particle bounce can be a problem with impactor samples using uncoated collection substrates ( Lawson, 1980). We are not aware of any studies of this potential 11 problem for exhaust PM with MOUDI impactors. Foils were stored and weighed in the same manner as the filter samples. No chemical analysis was done on these samples.

Continuous particle counts were made during most emission tests performed on the CDPHE site with a TSI Electrical Aerosol Analyzer ( EAA). The analyzer was operated continuously at a setting that measures all particles greater than 0.01 µ m aerodynamic diameter. This analyzer, which was designed for atmospheric studies, would be saturated by the high particle concentrations present at times in most of the mobile source tests. Therefore it was necessary to further dilute the sample drawn from the dilution tunnel. This was accomplished by using one or more diluters in series. The diluters were cartridge filters with different size " pinholes". The dilution ratio of each diluter was determined by placing it in the output stream of an aerosol generator and using the EAA to determine the change in particle number. Exhaust measurements were made at dilution ratios of 22 to 785 above that already generated by the dilution tunnel.

Particle counts made with the EAA in this manner are complicated by the fact that the EAA response is not identical for all particle sizes. Under normal operation, the analyzer is scanned through its size range, and the applicable response factors are used to determine the total number of particles. When operated at a single size setting, as in this study, an integrated response factor must be used that reflects the size distribution of the particles being measured. For calibration purposes, the EAA was used to measure particle size distributions from two vehicles operated under cruise conditions. It is not possible to obtain size distributions during cyclic operation since the scanning time is approximately two minutes. The response factor was determined by comparing the " step 3" voltage ( 0.01 µ m setting) to the total particle number calculated using TSI Model 390039 EAA software ( Twomey/ Kapadia algorithm). An integrated response factor of 1.25 x 105 particles/ cc/ volt determined from these tests was applied to all of the emission tests. It must be recognized that if the size distribution changes, the response factor can also change. Therefore, the particle numbers should be considered valid to no better than a factor of two. This high uncertainty has no effect on other measurements in the program since the particle number data is not used in any calculations.

Sample analysis. A representative subset of the samples was selected for chemical analysis. All analyses discussed in this report were performed at DRI. Samples were also provided to NIST for the determination of 14C content. These analyses were performed as part of the CRC/ NFRAQS funded Project A 20, " Carbon Isotopic Analysis of the Northern Front Range Air Quality Study's Summer and Winter 1996 1997 Program." Results will be given in the final report for that project.

Sulfate and nitrate were determined by ion chromatography ( IC). Teflo or Pallflex filters were extracted in 15 ml of 40: 60 water/ isopropyl alcohol in an ultrasonic bath for 60 min., then in a mechanical shaker for 60 min. This is the standard extraction solution for mobile source samples. It has been shown to be more efficient in extracting sulfate from mobile source samples than water alone because the alcohol acts as a wetting agent to help penetrate the hydrophobic samples. The ultrasonic bath temperature was maintained 12 below 27 ° C. Ammonium nitrate is easily lost from filters during sampling as nitric acid. Thus, nitrate values may be low. A more accurate sampling procedure would utilize a nitric acid denuder and a nylon backup filter. Such methods have been used in the past, and very little nitrate or nitric acid has been found. Since nitrate and nitric acid have never been found to be emitted in significant quantities from automobiles, it was not the focus of this study.

" Organic" carbon ( OC) and " elemental" carbon ( EC) were determined on 0.512 cm2 punches removed from the quartz filters using the DRI thermal optical reflectance ( TOR) technique ( Chow, 1993). With this method, OC is defined as carbon removed by pyrolysis at 550 ° C in a helium atmosphere, while EC is the carbon removed after pyrolysis by the addition of 2% oxygen. OC and EC results are corrected for charring by the optical monitoring of the reflectance. Teflo and Pallflex filters were analyzed for 38 elements by energy dispersive x ray fluorescence ( XRF) analysis ( Chow and Watson, 1994). PAHs are determined from the quartz filter/ PUF/ XAD samples. The PUF plugs are Soxhlet extracted with acetone, while the filters and XAD resin are Soxhlet extracted with dichloromethane. The extracts were combined and reduced to 1.0 ml by rotary evaporation and analyzed for approximately 70 PAHs by GC/ MS in selected ion monitoring mode. Samples have deuterated internal standards added before extraction to measure the recovery efficiency of the process. Hopanes and steranes are analyzed from these extracts by GC/ MS as well.

The primary purpose of measuring the PAHs was to create source profiles that can be used to determine the relative contributions of LDG and LDD exhaust PM emissions to the atmospheric particle burden. Some of the PAHs have also been designated by the EPA as air toxics. Samples for PAH analysis require extensive preparation, making the overall sample analysis cost high. To limit the number of PAH analyses, FTP runs from multiple vehicles were pooled on a bag basis. Since pooling of samples with large differences in emission rate would only result in a composite sample dominated by the high emitter, pooling was done on the basis of emission rate, rather than by vehicle age. Insufficient PUF/ XAD samples were collected to permit pooling by both vehicle age and emission rate. For the summer, a total of 29 FTP filter sets were pooled into 15 3 bag samples. These included four diesels pooled into three samples; six smokers into three samples; seven low emitters into three samples, six medium emitters into three samples, and six high emitters into three samples. Filter samples from all of the FTPs that were pooled for PAH analysis were also analyzed individually by IC, XRF, and TOR. This permitted the determination of the emission rates of the sulfate, nitrate, trace elements, OC and EC on a vehicle model year category basis, while still allowing the calculation of the pooled sample emission rates for source profiles.

For the winter, 42 FTP filter sets were pooled into 17 3 bag samples. Eleven diesels were pooled into five samples, eight smokers into three samples, six low emitters into two samples, five mid low emitters into two samples, eight medium emitters into three samples, and four high emitters into two samples. As before, filter samples from all of the FTPs that were pooled for PAH analysis were also analyzed individually by IC, XRF, and 13 TOR. All of the winter PUF/ XAD samples were collected from vehicles operated outdoors on the EPA dynamometer, since that was the most realistic condition for winter vehicle profile development. To determine if there is a difference in the composition of PM emitted at the indoor temperature as opposed to that outdoors, 18 indoor bag 1 samples were analyzed by IC and XRF. Samples from bags 2 and 3 of the FTP were not analyzed since it was unlikely that there would be significant differences in composition during hot stabilized or hot start operation.

Fuel. Vehicles were tested using the as received, on board fuel. Vehicle fuel samples were not collected. However, fuel sulfur content is of interest since it is used by the PM emission factor models to estimate sulfate emissions. Sixteen fuel samples were collected from service stations during the summer and 20 samples were collected in the winter. The samples were sent to Core Laboratories ( Houston, Texas) for analysis of fuel sulfur. The AAMA also collects and analyzes fuel samples during the summer and winter in Denver. The gasoline samples collected in this study put more emphasis on mid and premium grade gasolines than the AAMA program, so results would be complementary. Fuels tested are presented later, in Table 6.6. Average sulfur content is also given later, in Table 6.7. The AAMA samples ( AAMA, 1996/ 7) are analyzed for the complete set of standard fuel properties, including oxygenates. Readers interested in the fuel composition are referred to the AAMA report.

Smoking vehicle population. This test program specifically recruited smoking vehicles because of their obvious high PM emission rates. For the emission data to be useful, the in use frequency of smoking gasoline vehicles in the on road population must be estimated. Two programs were run to provide an estimate of this population. The first was a visual roadside survey of smoking vehicles in the Denver area. This effort, which is described in detail in Appendix D, found that 16 of 11,899 vehicles emitted visible smoke, a percentage of 0.13. The second approach was an analysis of the frequency of smoking vehicles observed by remote sensing at the westbound 6th Avenue off ramp from northbound I 25 site in Denver conducted by the University of Denver. Remote sensing has not been optimized for opacity measurements, and has not been calibrated or undergone independent validation studies. Thus, interpretation of the results is uncertain. It was found that 0.81 ± 0.24% of the gasoline vehicles had significantly increased exhaust plume opacity. 14 15 3. Quality Assurance/ Quality Control Several quality assurance procedures were used to validate the testing and sampling results. First, dynamometer coastdowns ( 55 to 45 miles per hour) were performed on both dynamometers using the same vehicle. The results were 13.38 sec for the CDPHE site and 13.58 sec for the EPA site, indicating that both dynamometers were providing similar loads to the vehicles. Next, cylinder calibration gases were exchanged. Results are given in Table 3.1.

Table 3.1. Cylinder Gas Standards Comparison Gas CDPHE EPA Scott1 Propane, ppmC 27.6 27.9 27.6 Propane, ppmC 165 167 165 CO, ppm 97.1 115 99.2 CO, ppm 971 993 963 NOx, ppm 69.8 72.0 70.6 NOx, ppm 88.0 89.3 90.2 CO2, % 2.62 2.61 2.68 CO2, % 3.50 3.53 3.56 1) Scott was the cylinder gas supplier Agreement was within three percent for all samples except the low CO concentration, which differed by 18%. Since EPA uses modal analysis without range changing, their analyzer must cover a very broad range of CO concentrations, with the low end being the least important for integrated values. Thus, this low CO point was at the low end of their calibration and consequently suffered in accuracy. The CDPHE measures emissions in bags, and must have accurate low CO readings. Overall, the agreement was judged to be excellent.

Site correlations. During the summer, results from the two sites could be directly compared by running the same vehicle. This was not possible during the winter due to the temperature differences. A 1991, 3.1L Corsica was chosen as the correlation vehicle for the summer study. It was operated on each site once a week. Results are given in Table 3.2.

The high PM result on the first EPA test was discounted since this was the first run after the equipment was setup, and the tunnel had not been conditioned. Considerable variability between emission tests is routinely observed. These can be caused by changes in the vehicle's operation and in changes in how the vehicle is driven. Few data are available about the reproducibility of PM emissions from light duty vehicles. For the regulated gaseous species, the CO emission rate is the most susceptible to variations in driving, with some vehicles experiencing changes of a factor of two in emission rate with different drivers, even though the tests are driven within the allowed test cycle speed 16 deviation. The last test on the EPA site was driven by a different driver than the first two tests. For comparison, the Auto/ Oil Air Quality Improvement Research Program ( A/ O AQIRP) used the ratios of emission rates from two tests to determine if a third test should be run. Acceptance ratios were 1.33, 1.70, and 1.29 for HC, CO and NOx, respectively. The HC and CO emission rates fall outside these criteria. This could still be due to driver differences rather than test site differences.

Table 3.2. Correlation Car FTP Results Site Date PM, mg/ mi HC, g/ mi CO, g/ mi NOx, g/ mi CO2, g/ mi EPA1 7/ 30/ 96 9.2 0.47 3.7 0.56 432 EPA 8/ 5/ 96 2.6 0.54 4.2 0.71 438 EPA2 8/ 12/ 96 2.7 0.34 1.7 0.51 419 CDPHE 8/ 6/ 96 0.9 0.21 1.4 0.56 396 CDPHE 8/ 13/ 96 0.9 0.23 2.0 0.53 397 1) First test run after equipment was set up 2) EPA driver change Emission results for the two test sites can be compared for all vehicles during the winter. The primary difference between the sites was the test temperature, the effect of which should be greatest on bag 1 emissions. Therefore, for QA purposes, the emission rates are compared for bags 2 and 3 only. Table 3.3 gives the average PM, HC, CO, and NOx emission rates for all non smoking vehicles, the smoking vehicles, and the diesels. Averages are for paired data only. Results for CO2 are not given since the EPA data used the CO2 comparison between the two sites to correct for a leak that occurred during some of the testing ( see Appendix C). Considering the differences in dynamometers, drivers, emission measurement method ( bag versus modal), temperature, and vehicle conditioning between subsequent tests, the agreement in average values is very good. Figures 3.1 and 3.2 show comparisons in HC and CO bag 2 emission rates for the gasoline vehicles. While there is considerable scatter in the data, the regressions and regression coefficients indicate good overall agreement. The PM data have much more scatter, with the result that the regressions were very poor for the gasoline vehicles, R2 of 0.23 and 0.08 for bags 2 and 3. PM correlations were better for smokers and diesels, which when compared together, had R2 values of 0.74 and 0.68 for bags 2 and 3, respectively.

Results from IM240 tests conducted at both sites were examined with all vehicles pooled together. The average masses emitted at the CDPHE and EPA sites were 135 and 148 mg/ mi, respectively. The R2 value for a linear correlation was only 0.40, although this correlation was greatly influenced by one point. 17 Table 3.3. Average FTP Bag 2 and 3 Winter Emission Rates Vehicles Site Bag 2 Bag 3 PM mg/ mi HC CO NOx PM mg/ mi HC CO NOx  g/ mi  g/ mi

Gasoline CDPHE 16.2 1.35 19.2 1.52 23.3 1.52 22.7 2.09 Gasoline EPA 19.0 1.58 17.2 1.63 21.7 1.47 17.0 1.79 Smokers CDPHE 298 4.37 44.6 1.96 315 4.28 44.0 2.68 Smokers EPA 233 5.56 47.0 2.19 268 4.62 41.5 2.53 Diesels CDPHE 380 0.80 1.86 1.87 495 0.64 1.68 1.56 Diesels EPA 370 1.09 1.73 1.63 425 0.79 1.50 1.29 Emissions variability. Vehicle emissions variability can be examined by comparing the results of the replicate FTPs that were run on every 10th vehicle. The first test on each vehicle was performed in the as received condition, whereas the second test had the first FTP as a preconditioning step. Thus, variability between tests is expected to be greater than that for normal vehicle testing which utilizes preconditioning to improve reproducibility. Variability is also expected to be higher for vehicles in a poor state of maintenance than for well maintained, properly functioning vehicles. Table 3.4 gives the emission rates for replicate FTP tests. The average of the ratios of the first to second test and the standard deviation of the ratios are given in the last two rows of the table. The average agreement is excellent, although it is clear that large differences can occur for individual tests. The standard deviation is by far the highest for the PM measurement, 80% vs. the next highest standard deviation of 29% for CO.

Replicate IM240 tests were run back to back, rather than on the successive days required by the FTP test because of the cold soak period. Since an FTP was run immediately before the first IM240, some preconditioning had been performed. Emission rates for the summer IM240 replicates are given in Table 3.5. The average ratio of the first to second test and the standard deviation of the ratios are given in the last two rows of the table. While the average ratio is highest for PM, this is influenced greatly by the last test. Deleting that test results in an average ratio of 0.92 with a standard deviation of 0.34. Table 3.6 gives the results from the back to back IM240 tests for the winter. The average ratios and standard deviations have outliers removed ( division by 0, and one test pair with a NOx ratio of 12).

Overall, PM emissions variability is higher for the FTPs than the IM240s. As noted above, two factors may explain this behavior. First is the lack of any vehicle preconditioning before the first FTP. In contrast, the first IM240 has an FTP as a preconditioning step. Second, the IM240s are short tests run back to back, whereas the FTPs are much longer tests and are run on subsequent days. Thus, the FTP is more likely to experience the vagaries of vehicle performance. We are not aware of any other studies of in use light 18 duty exhaust PM emissions that can be used to compare to the variability found in this study.

Table 3.4. FTP Emission Rates From Replicate Tests Vehicle1 Run Period Test Temp, ° F PM, mg/ mi HC, g/ mi CO, g/ mi NOx, g/ mi CO2, g/ mi 32 4472 summer 72 18 0.62 4.67 1.12 309 32 4485 summer 72 5.6 0.52 3.32 1.21 306 116 4580 summer 72 15 1.98 60.3 1.47 451 116 4586 summer 72 14 1.95 61.7 1.42 461 56 4520 summer 72 5.9 1.84 20.6 1.10 385 56 4533 summer 72 6.0 1.72 21.2 1.02 380 65 96074 summer 72 43 4.00 21.9 1.79 279 65 96090 summer 72 33 4.33 23.8 1.91 300 118 96152 summer 72 31 4.20 48.3 2.59 376 118 96158 summer 72 62 4.63 25.2 3.33 396 31 96037 summer 72 142 6.56 86.7 2.98 467 31 96050 summer 72 147 6.33 86.6 2.72 460 302 4680 winter 60 2.0 0.32 6.22 0.90 532 302 4693 winter 60 4.5 0.28 6.00 0.96 543 336 4752 winter 60 1.6 0.52 13.0 0.56 413 336 4761 winter 60 2.2 0.40 9.01 0.63 418 358 4816 winter 60 174 1.29 15.3 1.09 395 358 4847 winter 60 161 1.55 16.3 1.15 396 381 4888 winter 60 101 0.43 1.43 0.84 334 381 4891 winter 60 56.7 0.49 1.33 0.84 335 305 97035 winter 37 6.0 0.34 7.78 1.30 443 305 97038 winter 32 16.6 0.32 7.21 1.18 431 335 97099 winter 55 44.0 2.42 22.3 2.42 466 335 97106 winter 55 37.2 2.27 25.2 2.35 427 356 97183 winter 36 20.2 1.42 15.7 1.46 311 356 97192 winter 34 22.3 1.69 15.6 1.38 273 380 97233 winter 30 371 0.54 1.25 0.81 257 380 97236 winter 31 293 0.54 1.35 0.82 259 Ave. Ratio of 1st to 2nd Test 1.15 1.02 1.11 0.99 1.01 Std. Dev. of Ratios 0.80 0.14 0.29 0.09 0.05 1) Runs for the same vehicle listed in order of test date, starting with the first test 19 Table 3.5. Results from Summer Back to Back IM240 Emission Tests Vehicle Run PM, mg/ mi HC, g/ mi CO, g/ mi NOx, g/ mi CO2 g/ mi 6 4445 26.34 0.47 3.16 0.51 316 6 4446 25.42 0.39 3.27 0.51 315 4 4476 0.19 0.64 5.46 2.09 280 4 4477 1.10 0.43 7.84 1.48 286 63 4507 61.64 4.22 18.58 2.17 563 63 4508 50.33 3.30 19.98 2.09 563 88 4539 58.65 4.11 88.64 3.85 527 88 4540 50.44 3.79 93.35 3.45 502 119 4571 36.96 1.30 33.32 2.80 831 119 4572 52.36 1.21 33.14 2.77 840 2 96004 6.83 3.44 87.76 0.63 284 2 96005 7.25 2.22 91.00 0.62 271 25 96041 6.90 0.59 6.70 1.43 440 25 96042 6.60 0.42 3.70 1.40 485 65 96075 21.84 0.87 26.89 1.53 244 65 96076 31.13 0.97 39.90 1.20 240 71 96106 121.53 13.14 107.43 4.07 415 71 96107 132.56 14.10 106.13 3.70 409 101 96140 3.48 1.07 4.31 1.61 309 101 96141 4.41 1.13 5.54 1.51 292 126 96171 55.83 0.30 18.76 1.45 670 126 96172 37.73 0.46 28.40 1.35 650 152 96202 410.33 1.70 5.40 2.57 305 152 96203 88.77 1.00 4.53 1.86 284 Ave. Ratio 1.23 1.18 0.97 1.12 1.01 Std. Dev. 1.12 0.31 0.31 0.15 0.04 20 Table 3.6. Results from Winter Back to Back IM240 Emission Tests Vehicle Run PM, mg/ mi HC, g/ mi CO, g/ mi NOx, g/ mi CO2, g/ mi 310 4684 6.73 0.32 9.38 0.64 260.1 310 4685 3.83 0.23 5.42 0.58 271.6 317 4715 2.71 0.36 3.70 16.55 293.7 317 4716 2.69 0.29 5.34 1.38 293.0 332 4749 84.1 2.15 24.27 4.17 237.1 332 4750 97.6 2.17 26.93 4.03 240.5 349 4779 0.00 0.20 1.71 1.00 311.2 349 4780 0.00 0.08 0.90 0.77 313.3 337 4810 425 6.31 120.74 1.94 418.7 337 4811 468 6.97 126.31 1.88 415.5 362 4841 21.2 2.88 48.67 2.28 361.6 362 4842 14.7 2.96 39.70 2.53 362.0 377 4864 2.45 ND ND ND ND 377 4865 3.14 0.05 0.44 0.68 361.1 388 4904 679 0.30 2.05 2.62 445.3 388 4905 667 0.29 2.03 2.60 440.3 309 97032 2.48 0.11 0.96 1.44 355.7 309 97033 7.09 0.17 1.19 1.59 351.7 320 97069 24.5 5.46 26.58 2.70 441.1 320 97070 22.1 5.36 30.14 2.67 429.6 335 97100 37.6 1.99 23.77 2.75 439.5 335 97101 35.3 1.30 13.88 2.54 424.9 340 97131 1.83 0.00 0.84 0.42 242.0 340 97132 6.44 0.13 1.92 0.48 253.4 362 97162 9.55 1.95 42.96 1.40 294.8 362 97163 14.4 2.05 45.74 1.42 303.2 376 97196 1.03 0.01 0.70 0.17 226.7 376 97197 1.66 0.00 1.18 0.12 229.4 371 97227 7.88 0.69 7.22 1.19 237.5 371 97228 9.35 0.80 6.79 1.26 232.0 391 97258 339 0.42 0.90 0.48 236.2 391 97259 467 1.26 1.55 0.52 251.7 Ave. Ratio 0.90 1.03 1.03 1.04 0.99 Std. Dev. 0.38 0.58 0.44 0.15 0.03 21 Filters. Additional QA/ QC measures were taken to ensure the quality of the filter data. Both calibration weights and two control filters were weighed at least once during each weighing period. They were re weighed after every 20th filter, or if balance drift was encountered. The standard deviation on the control filters was ± 6 µ g. The control filters were stored in closed Petri dishes until the time of weighing. It was observed that they required much longer to reach a constant weight than sample filters that had been equilibrated with the room air before weighing. Thus, it is likely that the observed variability in the control filters represents a worst case situation.

Tunnel blanks are filter samples collected from the dilution tunnel operating at full flow with no vehicle exhaust. PM collected on a tunnel blank filter comes from the reentrainment of PM deposited in the tunnel during preceding vehicle testing and any ambient PM that passed through the tunnel air inlet filter. Tunnel blanks were collected periodically throughout the study. Results are given in Table 3.7, both as the mass collected and the equivalent emission rate for an FTP or an IM240 test. Tunnel blanks were lower during the summer than the winter at both sites. During the summer study, an effort was made to recruit and test the newest vehicles first, followed by the older vehicles Table 3.7. Tunnel Blanks Site Season Mass Collected, µ g FTP equivalent emission rate, mg/ mi IM240 equivalent emission rate, mg/ mi CDPHE summer 15 0.076 0.049 CDPHE summer 13 0.066 0.042 CDPHE summer 10 0.051 0.033 CDPHE summer 10 0.17 0.112 EPA summer 7 0.10 0.07 EPA summer 12 0.16 0.11 EPA2 summer 25 0.36 0.23 CDPHE winter 31 0.54 0.35 CDPHE2 winter 9 0.27 0.18 EPA winter 48 0.70 0.46 EPA winter 23 0.33 0.22 EPA winter 54 0.79 0.51 EPA winter 85 1.20 0.78 EPA1 winter 111 1.39 0.90 EPA1 winter 77 1.06 0.68 EPA2 winter 176 1.18 0.77 1) Collected immediately after a smoking vehicle 2) Collected immediately after a diesel vehicle 22 and finally the smokers in order to minimize tunnel contamination by the higher emitting vehicles. Unfortunately, the older vehicles and smokers were the hardest to find and recruit. Given the time constraints in the field, older vehicles and smokers were tested throughout the winter testing period. Diesels were tested at the end of the sampling period during both the summer and winter portions of the study.

Routine emission tests simultaneously collected samples on both Teflon and quartz filters. A few FTP tests were conducted with Teflon filters in both filter holders for comparison purposes. Results are given in Table 3.8. Samples collected at the CDPHE site during the winter are not shown. Examination of the data indicated a consistent difference between the two sample trains during the winter. It was subsequently determined that the body of the cyclone used for the quartz sample filter was leaking. Therefore, these samples were not used. Agreement between the duplicate filters was generally good. Eight IM240 tests were also conducted during the summer with duplicate Teflon filters. Results are shown in Table 3.9. Again, comparisons were judged to be acceptable.

Table 3.8. Duplicate Filter Samples for FTP Tests Site Season Test/ Filter Bag 1, mg/ mi Bag 2, mg/ mi Bag 3, mg/ mi FTP, mg/ mi CDPHE summer 1A 87.4 20.9 23.2 35.3 CDPHE summer 1B 114 27.0 27.0 44.9 CDPHE summer 2A 8.8 3.7 6.1 5.5 CDPHE summer 2B 10.3 4.1 5.6 5.8 CDPHE summer 3A 3.4 2.1 2.5 2.5 CDPHE summer 3B 2.4 1.4 2.4 1.9 EPA summer 4A 15.3 4.1 13.1 8.9 EPA summer 4B 15.9 4.1 13.9 9.2 EPA summer 5A 6.7 1.3 2.0 2.6 EPA summer 5B 5.2 1.3 1.7 2.2 EPA summer 6A 4.3 0.0 0.0 0.9 EPA summer 6B 5.4 0.0 0.3 1.2 EPA winter 9A 76.1 33.7 22.0 40.1 EPA winter 9B 73.8 30.1 20.5 37.8 EPA winter 10A 39.1 32.9 15.8 30.2 EPA winter 10B 38.7 30.4 13.6 28.1 Finally, tests were conducted with Teflon and Pallflex filters run simultaneously. Some of the tests were performed at the CDPHE site. However, the aforementioned leak in the cyclone invalidated these results. Table 3.10 gives the results for the EPA site. Large percentage differences were observed for the first two runs. We have no explanation for this apparent problem. Subsequent runs had better agreement. Note that the last filter pair was a comparison between two Pallflex filters. Similar testing conducted at SwRI and CE CERT leads to the conclusion that Pallflex was suitable for vehicle emission PM measurements ( private communication). 23 Table 3.9. Duplicate Filter Samples for Summer IM240 Tests Site Test # Filter A, mg/ mile Filter B, mg/ mi A B, mg/ mi CDPHE 1 26.4 22.1 4.3 CDPHE 2 25.4 24.8 0.6 CDPHE 3 2.2 3.6 1.4 CDPHE 4 1.1 5.4 4.3 EPA 5 6.8 6.9 0.1 EPA 6 7.3 6.6 0.7 EPA 7 0.3 0.8 0.5 EPA 8 0.0 0.0 0.0 Table 3.10. Comparison of Teflon and Pallflex Filter Samples Run Teflon PM, mg/ mi Pallflex PM, mg/ mi Difference 97172 1.95 7.37 5.4 97175 9.95 18.2 8.2 97178 59.8 65.0 5.2 97181 91.3 97.6 6.3 97184 12.7 13.4 0.7 971871 14.5 17.3 2.8 1) Comparison of two Pallflex filters Carbon measurements. As will be discussed later in this report, it was found that the total carbon measured on some quartz filters during the summer portion of the study exceeded the total mass measured on the Teflon filters. Since elements such as hydrogen, oxygen, sulfur, and nitrogen are associated with organic particulate matter, the total carbon should be consistently less than the measured mass. Similar discrepancies were observed in the CAWRSS study as well ( Sagebiel et al., 1997). At that time, no cause of the difference could be proven, but DRI, who performed the analyses, indicated that inhomogeneity in the filter deposits was the most likely explanation since the carbon analysis is performed on a small punch removed from the filter. Errors should be random unless the punches are not taken randomly. Inhomogeneities were visibly present on a few filter samples collected during this study. However, these were excluded from the filter set selected for carbon analysis. Visual inspection, however, is not adequate to screen for possible filter deposit inhomogeneities. Therefore, multiple punches for carbon analysis were taken from three filters during both the summer and winter portions of the study. Results are given in Table 3.11. With the exception of the center punch from the second filter, results indicate reasonable uniformity. 24 Table 3.11. Carbon Results From Multiple Punches Period Filter ID OC* EC* TC* Summer DYTQ052C1 12.8 24.2 37.1 DYTQ052M2 14.6 26.5 41.0 DYTQ052E3 9.6 26.5 36.0 Average 12.3 25.7 38.0 Std. dev. 2.1 1.1 2.1 Summer DYTQ053C4 18.1 6.9 25.1 DYTQ053M 7.7 0.3 7.8 DYTQ053E 7.3 0.0 7.3 Average 7.5 0.2 7.6 Std. dev. 0.2 0.2 0.3 Summer DYTQ222 585.2 614.5 1199.7 DYTQ222C 584.8 676.0 1260.8 DYTQ222M 597.1 685.1 1282.0 DYTQ222E 578.5 624.7 1203.4 Average 586.8 661.9 1248.7 Std. dev. 7.7 26.6 33.2 Winter DYDQ1436C 34.7 169.4 203.1 DYDQ1436M 33.8 184.0 216.8 DYDQ1436E 32.3 170.5 201.5 Average 33.6 174.6 207.1 Std. dev. 1.21 8.13 8.41 Winter DYDQ0700C 102.9 6.20 108.5 DYDQO700M 101.4 5.50 106.4 DYDQ0700E 95.8 6.20 101.4 Average 100.0 5.97 105.4 Std. dev. 3.74 0.40 3.65 Winter DYDQ1051C 28.6 18.9 46.9 DYDQ1051M 30.1 18.3 47.8 DYDQ1051E 26.5 17.6 43.5 Average 28.4 18.27 46.1 Std dev. 1.81 0.65 2.27 * Units in µ g/ filter for the summer and mg/ mi for the winter 1) Punch from center of filter 2) Punch from midway between center and edge of filter 3) Punch from edge of filter 4) Rejected as outlier based on abnormal carbon evolution temperature profile 25 It has long been recognized that filter sampling of organic particulate matter can have errors due to both the desorption of organic material from the particles deposited on the filter and from the adsorption of organic material onto both the particles and the filter material itself ( Cadle et al., 1983). One way of estimating the impact of adsorption onto the filter is to collect samples with a dual filter stack of quartz filters. This was done for four FTP tests during the summer. The filter analysis results are given in Table 3.12. The data in this table give the carbon in mg emitted during the indicated phase of the FTP test. The last four columns give the percent of the total OC and EC from both filters that were measured on the front and back filters. For the phase 1 filters, an average of 7.5% of the collected OC was on the backup filter. However, for the phase 2 filters 24.7% of the OC was found on the backup filters. The amount of OC collected on the backup filter was relatively constant, suggesting an adsorption process is occurring. The interpretation is complicated, however, by the presence of EC on the backup filter. Any EC on the backup filter should be due to particle penetration ( unless the EC measured by TOR was really OC). If that is the case, then the OC associated with those particles must be present on the backup filter as well. The reported EC, however, is close to the uncertainty in the measurement, and may not represent particle penetration. The amount of OC on the backup filter can not be used to correct the front filter since it is unknown how much of the OC was adsorbed from gas phase HC that passed through the front filter as compared to the amount that was revolatilized from the front filter and redeposited on the backup filter.

Additional dual filter experiments were performed in the winter. Dual quartz filters were collected simultaneously with dual Teflon/ quartz filter packs during eight IM240 tests. Results are shown in Table 3.13. The average OC collected on the backup filter for the dual quartz filter pack was equivalent to an emission rate of 6.1 mg/ mi OC. A relatively constant amount of OC was observed on the backup filter, supporting the earlier suggestion that this is due to adsorption of OC. For lightly loaded filters, such as run 97073, the backup filter OC emission rate is equal to 34% of that based on the front filter alone. For heavily loaded samples, such as run 97088, the adsorbed OC on the backup filter is less than one percent of the emission rate based on the front filter. With the exception of the first run listed in Table 3.13, the Teflon/ quartz backup filter collected more OC than the quartz/ quartz backup filter. The increase is presumed to be due to OC that that is adsorbed on the front quartz filter, but passes through or is released from deposits on the Teflon filter. Table 3.13 also shows that a small amount of EC was reported on the backup quartz filters. Similar amounts were seen for both the Teflon and quartz backup filters. As before, these levels are close to the uncertainty of the measurement method and probably represent analytical error. The total carbon collected on the Teflon/ quartz backup filter averaged 13.9% of the total carbon collected on the front quartz filter. The additional TC collected behind the Teflon filter averaged 6.2% of the total carbon on the quartz filter. No speciation of the backup filter organic carbon was performed. Overall, it is concluded that quartz filters can capture substantially more OC than Teflon filters. It is not possible to determine if all of the adsorbed OC was initially present in the gas phase, or if some of it was released from particles collected on the front filter. However, it is likely that the OC determined from quartz filters is an overestimate 26 of the actual particulate matter OC.

Table 3.12. Carbon Measured on Front and Back Summer Quartz Filters Front Filter Back Filter % of OC on % of EC on Run Phase OC EC TC OC EC TC Front Back Front Back 96047 1 115 66.0 181 9.0 0.9 9.9 92.8 7.2 98.6 1.4 96078 1 128 38.7 167 12.0 2.0 13.9 91.4 8.6 95.1 4.9 96081 1 25.2 28.0 53.2 3.7 1.1 4.8 87.2 12.8 96.2 3.8 96090 1 236 249 485 3.2 0.0 3.1 98.7 1.3 100.0 0.0 MEAN 92.5 7.5 97.5 2.5 STD DEV 4.1 4.1 1.9 1.9 % of OC on % of EC on Run Phase OC EC TC OC EC TC Front Back Front Back 96047 2 25.7 16.9 42.7 7.9 1.2 9.1 76.5 23.5 93.2 6.8 96078 2 38.5 3.1 41.6 12.3 3.1 15.5 75.8 24.2 49.7 50.3 96081 2 11.1 1.0 12.0 4.8 0.6 5.4 69.8 30.2 62.5 37.5 96090 2 12.4 3.7 16.1 3.3 0.7 3.9 79.2 20.8 84.4 15.6 MEAN 75.3 24.7 72.4 27.6 STD DEV 3.5 3.5 17.3 17.3 % of OC on % of EC on Run Phase OC EC TC OC EC TC Front Back Front Back 96047 3 24.3 25.9 50.2 7.6 1.6 9.2 76.1 23.9 94.0 6.0 96078 3 41.0 9.3 50.2 7.5 0.9 8.4 84.5 15.5 91.5 8.5 96081 3 11.9 3.2 15.1 2.7 1.8 4.5 81.4 18.6 64.0 36.0 96090 3 13.7 14.1 27.8 0.0 0.2 0.0 100.0 0.0 98.9 1.1 MEAN 85.5 14.5 87.1 12.9 STD DEV 8.9 8.9 13.6 13.6 Carbon units are total mg emitted per phase, front filters are carbon tunnel blank corrected Teflon  Pallflex Comparisons. During the summer, Teflon filter samples from high emission vehicles were observed to lose some flow due to plugging. Therefore, in the winter Pallflex T60A20 filters were used in place of Teflon membrane filters for these vehicles. Three sets of simultaneously collected Teflon membrane and Pallflex T60A20 filters were collected and analyzed by IC and XRF for comparison purposes. One of the filters was lost during analysis. All T60A20 filters had high nitrate backgrounds and higher backgrounds of most of the elements determined by XRF. Therefore, the only valid comparison for these filters was for sulfate. The sulfate emission rate determined from the two Teflon membrane filters was 0.098 and 0.181 mg/ mi while it was 0.086 and 0.174, respectively, from the Pallflex filters.

Table 3.13. Carbon Measured on Front and Back Winter Quartz Filters 27 Run Cycle OC, mg/ mi EC, mg/ mi TC, mg/ mi Front Qback1 Tback2 Front Qback Tback Front Qback Tback 97054 IM240 44.7 15.6 8.7 35.5 0.9 0.3 79.7 15.9 8.5 97063 IM240 71.2 3.4 4.3 61.8 0.8 1.3 132 3.7 5 97066 IM240 163 7.1 14.4 19.6 1.4 1.6 182 7.9 15.5 97069 IM240 16.7 5.7 10.8 3.2 0.2 0.3 19.2 5.3 10.5 97073 IM240 8.2 0 2.3 1.8 0 0 9.4 0 1.7 97082 IM240 89.1 4.6 9.1 26.8 0.1 0.3 115 4.1 8.8 97088 IM240 666 6.5 11.8 169 0.5 0.4 835 6.4 11.6 97091 IM240 145 5.7 12.5 42.5 0.4 0.5 187 5.5 12.4 1) Qback is the quartz backup filter behind a quartz front filter 2) Tback is the quartz backup filter behind a Teflon front filter 28 29 30 4. Emission Rates of PM and Regulated Gaseous Pollutants This section presents the average emission rates of PM and the regulated pollutants as well as the relationships between them. Results will focus on the average emission rates for the six categories of vehicles tested: 1971 80, 1981 85, 1986 90, 1991 96, smokers, and diesels.

Vehicles Table 4.1 gives the number of vehicles in each category as well as their average age and odometer reading. 1996 model year vehicles were defined as being 0.5 years old during the summer and 1.0 year old during the winter. Not all drivers were asked if their odometer had rolled over ( exceeded 100,000 miles on an odometer that reads a maximum of 99,999 miles), and some drivers did not know if the odometer had rolled over. Thus the odometer readings on old vehicles are highly uncertain. The average odometer readings in Table 4.1 assumed that any vehicle older than 1986 with an odometer reading less than 50,000 miles had rolled over once. Uncorrected values are given in the footnote to the Table. These odometer readings should be viewed as estimates since errors can be produced by factors other than rollover. The biggest differences between the summer and winter vehicle fleets are for the smokers and the diesels. Winter smokers averaged significantly older than those from the summer, although the reported average odometer readings are essentially the same. The range in smoker model years was large, 1969 1990 in the winter and 1966 1989 in the summer. The average age of diesels in the summer was 7.3 years, while it was 15.3 in the winter. This was the result of selecting vehicles during the winter that could be accommodated on the EPA chassis dynamometer. Most newer vehicles are in relatively large trucks which are too heavy for the EPA dynamometer. Thus, the winter diesel vehicles were dominated by older passenger cars that ranged in model year from 1979 to 1989. The summer diesels ranged in model year from 1980 to 1994. Appendices B 1 and B 3 list all of the individual vehicles.

Table 4.1. Vehicle Age and Odometer Vehicle Category Number Average Age Average Odometer1 Number Average Age Average Odometersummer winter 1971 80 25 19.8 117,000 17 19.3 149,000 1981 85 25 13.2 142,000 16 13.4 113,000 1986 90 22 8.7 109,000 14 8.5 102,000 1991 96 20 3.0 40,000 10 3.2 65,000 Smoker 9 13.8 110,000 15 17.4 119,000 Diesel 10 7.3 89,000 12 15.2 161,000 1) Uncorrected odometer averages: Summer 1971 80, 85,000; summer 1981 85, 134,000; winter 1971 80, 130,000; winter 1981 85, 95,000; winter diesel, 151,000.

FTP emission rates of regulated pollutants Table 4.2 gives the average emission rates for each vehicle category tested during the summer and the winter. Winter CDPHE was the 31 indoor site while winter EPA was the outdoor site. In all cases, the average emission rates increase with increasing age. Figure 4.1 shows the relationship between vehicle age and FTP HC emission rate for the individual summer gasoline vehicles, excluding recruited smokers. The increase in emissions with age is obvious, although it is also seen that some older vehicles have relatively low emissions. All vehicles less than six years old had low HC emissions. Figure 4.2 shows the same relationship for NOx. Again emissions increase with age, but the range is considerably lower than for HC. As expected, the diesels have relatively low HC and CO emissions but high NOx. The standard deviation, minimum value and maximum value for each of the average emission rates are given in Appendix F1. The highest individual HC and CO emission rates for diesel vehicles were 2.89, and 9.08 g/ mi., respectively, while those for gasoline vehicles were 45 and 347 g/ mi, respectively.

Table 4.2. Average FTP Regulated Emission Rates Period Category Number HC CO NOx  g/ mi  Summer 1991 96 20 0.24 2.35 0.42 Summer 1986 90 22 1.03 14.7 1.32 Summer 1981 85 25 2.7 35.9 1.54 Summer 1971 80 25 6.08 62.6 2.46 Summer Smoker 9 3.59 38.8 1.88 Summer Diesel 10 ND 3.99 4.57 Winter CDPHE 1991 96 10 0.56 6.74 0.51 Winter CDPHE 1986 90 14 0.63 9.23 1.44 Winter CDPHE 1981 85 16 2.57 35.7 2.76 Winter CDPHE 1971 80 16 2.78 44.3 2.11 Winter CDPHE Smoker 15 4.96 52.6 2.28 Winter CDPHE Diesel 12 0.82 1.94 1.73 Winter EPA 1991 96 9 1.02 11.6 0.53 Winter EPA 1986 90 14 1.06 15.5 1.61 Winter EPA 1981 85 16 3.39 38.7 2.31 Winter EPA 1971 80 16 4.49 52.1 2.01 Winter EPA Smoker 15 8.71 65.6 2.29 Winter EPA Diesel 12 1.1 1.76 1.55 Winter indoor and outdoor measurements on the same vehicles can also be compared. In section 3, it was shown that FTP bag 2 and 3 emission rates were in good agreement between the indoor and outdoor sites. Table 4.2, on the other hand, shows that FTP emission rates consistently averaged higher outdoors than indoors, as would be expected for the lower temperatures. Clearly, all of this difference is attributable to the bag 1 emissions, which are higher due to the longer warm up times for the emission control system. Average vehicle oil temperature and ambient temperature at the start of the emissions tests are given in Table 4.3. In most cases the oil temperature lagged the ambient temperature since testing was done after an overnight soak. Average test 32 temperatures for each vehicle category were from 22 to 34 ° F colder outdoors than indoors.

Table 4.3. Winter Outdoor Average Vehicle Test Temperature Vehicle Category Oil Temperature Ambient Temperature ° F 1971 80 28.2 30.9 1981 85 36.6 40.7 1986 90 31.9 38.4 1991 96 35.0 38.0 Smoker 39.9 44.4 Diesel 39.5 40.1 IM240 emission rates of regulated pollutants. IM240 average emission rates are given in Table 4.4 for both the summer and winter periods. Appendix F2 gives the standard deviation, the minimum and the maximum values for each category as well. Since the IM240 is a hot start test, little effect of temperature is expected. Figure 4.3 shows the relationship between the indoor and outdoor sites for HC on the same vehicles. The linear regression slope of 1.03 and the R2 of 0.82 are good considering the differences in preconditioning and other factors between the test sites. The slopes and regression coefficients for CO were 0.74 and 0.73, respectively, while those for NOx were 0.56 and 0.79, respectively. The NOx regression had a significant non zero intercept.

IM240 emission rates of regulated species were compared to those measured on the FTP for both the summer and winter. Figure 4.4 shows the relationship for CO during the summer, while Figure 4.5 shows that for NOx at the EPA site during the winter. All vehicles, including the smokers and diesels were included in these comparisons. Correlation coefficients are good, 0.82 and 0.90 for CO and NOx, respectively. Table 4.5 gives the slopes and regression coefficients for all of the regulated pollutants. In general, regression coefficients indicate a strong relationship between the IM240 and the FTP emission rates. Agreement is closest for NOx. In all cases, CO and HC linear regression slopes indicate that emissions are lower on the IM240 than the FTP. This was especially true for the EPA site in the winter due to the elevated FTP emission rates at the low cold start temperature.

Idle test emission rates and concentration. Vehicles received both an incoming two speed idle test and a post IM240 idle test. These tests were added to the program for other purposes and won't be analyzed for this report. The results, however, are given in Appendix G.

Table 4.4. IM240 Average Emission Rates Period Category N HC CO NOx 33  g/ mi  Summer 1971 80 22 4.74 59.7 2.90 Summer 1981 85 24 1.72 25.4 1.76 Summer 1986 90 20 0.77 14.6 1.47 Summer 1991 96 17 0.13 2.18 0.43 Summer Smoker 7 2.23 33.0 2.19 Summer Diesel 10 ND 3.10 4.14 Winter CDPHE 1971 80 16 2.24 40.6 2.67 Winter CDPHE 1981 85 15 1.76 29.7 3.59 Winter CDPHE 1986 90 14 0.57 7.64 2.93 Winter CDPHE 1991 96 9 0.51 5.04 0.63 Winter CDPHE Smoker 15 3.84 42.5 3.05 Winter CDPHE Diesel 12 0.63 1.68 1.49 Winter EPA 1971 80 15 2.15 27.4 1.81 Winter EPA 1981 85 16 1.27 20.9 2.18 Winter EPA 1986 90 14 0.39 7.62 1.65 Winter EPA 1991 96 9 0.35 2.94 0.45 Winter EPA Smoker 15 3.81 40.0 2.36 Winter EPA Diesel 12 0.64 1.45 1.15 Table 4.5. Slope and Regression Coefficients for Linear Regressions Between the FTP and IM240 Emission Rates Period Species Slope R2 Summer HC 0.73 0.95 Summer CO 0.75 0.82 Summer NOx 1.14 0.84 Winter CDPHE HC 0.64 0.87 Winter CDPHE CO 0.77 0.82 Winter CDPHE NOx 1.10 0.87 Winter EPA HC 0.46 0.72 Winter EPA CO 0.53 0.85 Winter EPA NOx 0.88 0.90 PM FTP emission rates. Table 4.6 gives the average PM 10 emission rates by vehicle grouping for both the summer and winter portions of the study. Appendix F3 gives the standard deviation, the minimum value, and the maximum values for each vehicle category as well. The effect of vehicle age is pronounced, with the summer 1971 80 vehicles emitting an average of 95.4 mg/ mi compared to average emissions of 2.8 mg/ mi from the summer 1991 96 vehicles. Similar results were observed for the winter measurements. Figure 4.6 shows the FTP PM emission rates as a function of vehicle age for the summer non smoking gasoline vehicles. It is clear that most new vehicles have low PM emission rates, but that after 10 years there is a wide range of emissions. The winter CDPHE average for the 1971 80 and 1991 96 vehicles in Table 4.6 are given both for all tested 34 vehicles, and for only those that match those tested at the EPA site outdoors, a difference of one vehicle in each case. This permits a valid direct comparison between the indoor and outdoor data. This comparison is shown graphically in Figure 4.7. Emission rates decrease with age for all three groups ( summer, winter indoor, and winter outdoor). The indoor winter emission rates average lower than those for comparable vehicles tested during the summer for the 1971 80, 1981 85, and 1986 90 vehicles. Emission rates were similar for the 1991 96 vehicles ( 2.82 in the summer, 3,74 in the winter). It is possible that the decrease between the two seasons is due to fuel changes. Oxygenated fuels are mandated in the winter in the Denver area, but not the summer. It was found in a study of PM emission rates from vehicles using Alaska fuel ( Mulawa et al., 1997), that adding ethanol reduces PM formation at temperatures from 72 to   20 ° F. However, other changes in fuel composition such as sulfur or aromatic content could impact PM emission rates as well. Fuel composition is examined later in this report. As expected, average PM emission rates in the outdoor tests exceeded those of the indoor tests. The winter outdoor PM emission rates were lower than those from the summer for the 1971 80 and 1986 90 vehicles. 1981 85 vehicles had slightly higher average emissions in the winter than summer. The major difference is for the 1991 96 vehicles, which had a much higher winter outdoor average. The winter EPA PM average drops to 12.6 with the removal of one vehicle with a PM emission rate of 124 mg/ mi. Thus, the emission rate for this category remain uncertain.

The smoking vehicle and diesel vehicle populations between the summer and winter were not well matched. Thus, these emissions should not be compared. It is appropriate, however, to compare the indoor and outdoor tests. For the smoking vehicles, the emissions averaged 9.8% higher outdoors. The diesels also averaged 9.3% higher outdoors. This is a much lower impact than seen for the randomly recruited gasoline vehicles. For example, the difference in the 1981 85 vehicles was 34%.

At least some of the difference in temperature sensitivity between the non smoking gasoline vehicles and the diesel and smoking gasoline vehicles is due to the relative importance of emissions in the three phases of the FTP. As noted earlier, only phase 1 is affected significantly by the ambient temperature. Table 4.6 gives the fraction of the total mass emitted over the entire FTP that was emitted in each phase. Since the FTP weighs the three phases, this is not the same as the fractional contribution to the FTP. Emission rate by phase are given in Table 4.7. For the non smoking gasoline vehicles, the majority of the mass is emitted in phase 1. Due to the temperature effect, the fraction in phase 1 is even greater for the vehicles in the winter outdoor tests than the indoor tests. Figure 4.8 plots the vehicle oil temperature and the ambient temperature immediately before the FTP test, as well as the FTP phase 1 total mass emission rates outdoors ( EPA) and indoors ( CDPHE) for each paired vehicle in the 1981 85 vehicle category. The PM emissions are higher outdoors for 13 of the 15 vehicles. Phase 2 results are shown for the same vehicles in Figure 4.9. The emissions are much lower, and the differences appear to be random and within the test variability. Figure 4.10 shows the effect on diesel phase 1 FTP PM emissions. Ten out of 12 vehicles had higher emissions at the reduced temperature. Phase 2 FTP diesel emissions are shown in Figure 4.11. Only 4 of the 12 vehicles had higher emissions at the lower temperature. In addition, the emissions, while lower than 35 during phase 1, are still substantial. Thus, the overall impact of temperature was less for the diesel than the non smoking gasoline vehicles.

Table 4.6. FTP PM Emission Rates and Bag Fractions Period Category N Fraction Bag 1 Fraction Bag 2 Fraction Bag 3 PM, mg/ mi Summer 1971 80 25 0.64 0.18 0.19 95.5 Summer 1981 85 25 0.66 0.17 0.17 47.4 Summer 1986 90 22 0.61 0.21 0.18 44.4 Summer 1991 96 20 0.58 0.19 0.23 2.82 Summer Smoker 9 0.49 0.24 0.27 225 Summer Diesel 10 0.54 0.16 0.29 811 Winter CDPHE 1971 80 16 0.62 0.16 0.22 54.2 Winter CDPHE ( match vehicles to EPA) 1971 80 15 0.63 0.15 0.22 56.6 Winter CDPHE 1981 85 16 0.59 0.2 0.21 35.9 Winter CDPHE 1986 90 14 0.71 0.13 0.16 11.8 Winter CDPHE 1991 96 10 0.62 0.16 0.21 3.51 Winter CDPHE ( match vehicles to EPA) 1991 96 9 0.62 0.18 0.20 3.74 Winter CDPHE Smoker 15 0.45 0.28 0.26 395 Winter CDPHE Diesel 12 0.41 0.27 0.32 460 Winter EPA 1971 80 15 0.77 0.11 0.13 82.6 Winter EPA 1981 85 16 0.75 0.12 0.13 48.2 Winter EPA 1986 90 14 0.68 0.16 0.15 28.5 Winter EPA 1991 96 9 0.83 0.11 0.07 24.9 Winter EPA Smoker 15 0.59 0.22 0.2 434 Winter EPA Diesel 12 0.50 0.24 0.25 503 Table 4.7. FTP PM emission rates by phase.

Period Category N Phase 1 mg/ mi Phase 2 mg/ mi Phase 3 mg/ mi FTP PM, mg/ mi Summer 1971 80 25 235 54.2 68.4 95.5 Summer 1981 85 25 98.9 32.1 38.5 47.4 Summer 1986 90 22 91.7 33.6 28.8 44.4 Summer 1991 96 20 5.7 1.8 2.4 2.82 Summer Smoker 9 253 231 192 225 Summer Diesel 10 1646 398 964 811 36 Winter CDPHE 1971 80 16 139 27.4 40.3 54.2 Winter CDPHE ( match vehicles to EPA) 1971 80 15 147 28.2 42.1 56.6 Winter CDPHE 1981 85 16 82.6 20.3 30.2 35.9 Winter CDPHE 1986 90 14 27.9 7.3 8.2 11.8 Winter CDPHE 1991 96 10 8.9 1.7 2.8 3.51 Winter CDPHE ( match vehicles to EPA) 1991 96 9 9.4 1.9 2.9 3.74 Winter CDPHE Smoker 15 742 298 315 395 Winter CDPHE Diesel 12 699 377 494 460 Winter EPA 1971 80 15 290 26.1 37.9 82.6 Winter EPA 1981 85 16 159 19.0 21.4 48.2 Winter EPA 1986 90 14 70.6 16.9 18.7 28.5 Winter EPA 1991 96 9 81.3 13.4 6.3 24.9 Winter EPA Smoker 15 1179 231 272 434 Winter EPA Diesel 12 875 384 448 503 Comparison of PM and HC FTP emission rates. In previous studies, the lack of PM emission measurements on light duty gasoline vehicles has forced the use of HC as a surrogate for PM. In the EPA Motor Vehicle Related Air Toxics Study ( EPA, 1994), it was estimated that PM is 1.1% of the mass of total HC emitted on an FTP. In the CAWRSS and Orange County studies, the relationship between IM240 PM and HC was examined and found to be very weak. In the Alaska study on FTP PM emissions ( Mulawa et al., 1997) a good correlation was found. The relationship between PM and HC emission rates was reexamined for this study. Figure 4.12 plots the PM and HC emission rates for the individual non smoking gasoline vehicles tested during the summer. The correlation for a linear regression is poor ( R2= 0.23). The linear correlations for the winter indoor and outdoor data were similar with R2 of 0.16 and 0.24, respectively. Thus, it is clear that HC is not a good surrogate for gasoline PM emissions on an individual basis. This is not unexpected since the PM emissions can arise from at least two separate phenomena, rich air/ fuel operation and oil consumption. On the other hand, examination of the average emissions rates in Tables 4.2 and 4.6 indicate that both average PM and HC do increase with vehicle age. Therefore, the average PM and HC emission rates for the non smoking gasoline vehicles from the summer and the indoor and outdoor winter portions of the study were compared. The result, shown in Figure 4.13, shows that average values based on vehicle age have an R2 of 0.89. The slope of the linear regression indicates PM increases 15 mg/ mi for each g/ mi of HC. This is somewhat higher than the 1.1% value used by the EPA.

IM240 PM emission rates. Table 4.8 gives the average IM240 PM emission rates by vehicle category and study period. The standard deviation, minimum value, and maximum value for each category and study period are given in Appendix F4. These averages are not matched with those for the FTP in Table 4.6 since the number of vehicles in some categories is less. The main reason for measuring IM240 PM emission rates was to compare the results to those of the FTP. If results are in good agreement, then the 37 IM240 data obtained in previous studies could be used with higher confidence as a representation of in use emissions. Also, further consideration could be given to making IM240 measurements of PM. The comparison of IM240 and FTP PM emission rates for the summer is given in Figure 4.14. This regression includes all vehicles, including diesels. One high emitting diesel was omitted from the comparison since it was so far off scale. Including this point changed the R2 to 0.97 and the slope to 0.86. Including the diesel and smoking vehicles in the comparison greatly enhances the correlation. Figure 4.15 shows the comparison for non smoking gasoline vehicles only. There is much more scatter in the data and the R2 drops to 0.53. The comparisons for the winter indoor and outdoor data sets are shown in Figures 4.16 and 4.17, with all vehicles included. The regressions are good ( R2 of 0.88 and 0.84), and the slopes are surprisingly close to unity ( 1.02 and 0.91). The good agreement is somewhat surprising given the impact of cold start emissions on the FTP. Presumably, the regressions are driven by the higher emitters, which have less of a cold start impact than the low emitters.

Table 4.8. IM240 PM Emission Rates Period Category N Average PM, mg/ mi Summer 1971 80 22 82.1 Summer 1981 85 24 21.9 Summer 1986 90 20 21.6 Summer 1991 96 17 2.18 Summer Diesel 8 762 Summer Smoker 7 192 Winter CDPHE 1971 80 16 43.0 Winter CDPHE 1981 85 16 16.38 Winter CDPHE 1986 90 14 14.4 Winter CDPHE 1991 96 9 1.57 Winter CDPHE Diesel 12 403 Winter CDPHE Smoker 15 350 Winter EPA 1971 80 16 27.6 Winter EPA 1981 85 16 31.2 Winter EPA 1986 90 14 172 Winter EPA 1991 96 9 4.24 Winter EPA Diesel 12 394 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 5. Particle Number and Size Particle number. The number of particles larger than 0.01 µ m in diameter was monitored continuously using an Electrical Aerosol Analyzer ( EAA). Figures 5.1 through 5.3 plot the EAA trace for the three phases of the FTP. Results are given for three of the summer emission tests. These were selected to represent vehicles with high, medium, and low PM 10 emission rates. The dark solid line in the figures is the FTP speed time trace. Both the speed time trace and the EAA traces are plotted in actual time, i. e. the EAA data were not corrected for any lags due to transfer lines. Therefore, the EAA data are probably shifted a few seconds to longer times compared to the FTP trace. Note also that the relative particle count scale ( vertical scale) is expanded for the phase 2 and 3 plots compared to phase 1.

Several conclusions can be drawn from these data. First, the particle count from the high PM mass emitter is consistently higher than the count from the medium mass emitter, which in turn is higher than that for the low emitter, for phase 1 of the FTP. This suggests that the integrated particle count may be roughly proportional to particle mass. Note that the medium emitter emits higher numbers of particles than the high emitter in phases 2 and 3 of the FTP. This was also reflected in the measured mass emissions. Second, the number of particles emitted is highly variable, even for the high emitter. Some of the variation in particle number is due to the change in exhaust dilution ratio in the dilution tunnel, which is proportional to exhaust flow. It is apparent, however, that spikes in particle number emissions are associated with driving events, such as acceleration. This has been observed in other tests as well ( Maricq et al., 1998) and is also commonly observed for the emissions of gaseous regulated pollutants. This suggests that PM emission rates are cycle dependent, and that real world PM emission studies conducted under steady state operation will tend to underestimate the number of particles emitted and probably the particle mass. Third, in many instances, all three vehicles show peaks in particle number emissions at the same point in the cycle, indicating a consistency in the particle formation events for different vehicles.

The areas under the EAA curves were integrated to determine the total number of particles emitted on each phase of the FTP. Twenty five FTP runs from the summer were judged to have valid data. All of these runs were for gasoline vehicles. Results are given in Table 5.1 along with the corresponding measured FTP mass emission rates. For the winter, there were 84 FTP runs with EAA data, twelve of which were for diesel vehicles. All EAA data were collected indoors on the CDPHE site. Table 5.2 gives the EAA particle emission rates for the gasoline vehicles in the winter, while Table 5.3 gives the rates for the diesel vehicles. As before, the corresponding PM 10 mass emission rates are also given. Linear regressions were run between the EAA particle number and the PM 10 mass emission rates for both the summer and the winter. Results were best for the summer data, which are shown in Figure 5.4. This figure includes data from all three phases of each FTP. While there is clearly considerable scatter in the data, the R2 of 0.70 is good. Correlation coefficients were similar for each FTP phase considered separately ( R2 of 0.71, 0.64, and 0.77) and for the composite FTP ( R2 of 0.69). There was more scatter in the winter data, as shown in Figure 5.5, which plots all the FTP phases from the 55 gasoline vehicles. The R2 is poor, only 0.29. One difference in the two data sets is that the winter includes more high emitters. It is possible that a few large particles were collected on some samples. This could significantly affect the particle number to mass ratio. Therefore, we examined only the data with mass emission rates of 300 mg/ mi or less. The correlation improved slightly to an R2 of 0.39. It does not appear that a few vehicles are dominating the correlation. The R2 values for correlations between PM 10 mass emission rate and the particle number emission rate for each FTP phase were 0.36, 0.16, and 0.25 for the winter. Correlations were slightly better for the diesel vehicles, with an overall R2 of 0.35 with all phases considered, and individual FTP phase 1, 2, and 3 correlations of 0.48, 0.26, and 0.27, respectively.

PM 10 and total particle number need not be well correlated. A large number of very small particles contribute little to the total mass. For example, it takes one billion 0.01 µ m particles to equal the mass of one 10 µ m particle, assuming they all are spheres with equal density. Thus, the total particle emission rate could undergo large variations with little effect on the emitted PM 10 mass concentration. The observation that PM 10 and particle number correlate as well as they do suggests that the particle size distributions are fairly constant. 56 Table 5.1. Summer EAA Particle Emission Rates and PM 10 Mass Emission Rates Run # Phase 1 Phase 1 Phase 2 Phase 2 Phase 3 Phase 3 FTP Composite particle/ mi mg/ mi particle/ mi mg/ mi particle/ mi mg/ mi Particle/ mi mg/ mi 4444 3.16E+ 14 113.6 1.50E+ 14 27.0 1.45E+ 14 27.0 1.83E+ 14 44.9 4448 4.92E+ 13 10.3 1.86E+ 13 4.1 3.78E+ 13 5.6 3.02E+ 13 5.8 4457 1.01E+ 14 5.0 7.65E+ 12 2.9 1.42E+ 13 2.6 2.88E+ 13 3.3 4460 1.59E+ 13 3.7 2.53E+ 13 2.4 9.58E+ 12 3.2 1.90E+ 13 2.9 4463 9.40E+ 12 2.4 2.16E+ 11 1.4 8.39E+ 11 2.4 2.29E+ 12 1.9 4466 1.00E+ 14 10.4 5.31E+ 13 2.7 3.33E+ 13 2.1 5.75E+ 13 4.1 4469 2.54E+ 13 15.9 8.39E+ 11 4.0 1.13E+ 13 6.2 8.80E+ 12 7.0 4472 4.31E+ 14 57.2 1.23E+ 14 7.0 1.09E+ 14 10.1 1.83E+ 14 18.2 4475 1.12E+ 14 5.6 3.31E+ 13 5.4 1.43E+ 13 0.0 4.42E+ 13 3.9 4482 2.29E+ 14 28.7 3.85E+ 13 11.9 1.66E+ 14 15.8 1.13E+ 14 16.4 4490 3.77E+ 14 33.3 1.52E+ 14 9.2 6.99E+ 13 5.7 1.76E+ 14 13.2 4496 4.49E+ 13 2.1 1.48E+ 13 0.5 1.93E+ 12 0.3 1.75E+ 13 0.8 4499 1.77E+ 14 5.4 7.74E+ 13 2.0 7.79E+ 13 6.0 9.82E+ 13 3.8 4502 3.15E+ 15 379.1 2.27E+ 15 253.9 3.03E+ 15 246.4 2.66E+ 15 277.5 4506 3.33E+ 15 105.7 2.04E+ 15 28.9 2.13E+ 15 40.3 2.33E+ 15 47.9 4510 1.86E+ 15 151.0 1.11E+ 15 127.9 7.63E+ 14 48.5 1.17E+ 15 110.9 4513 5.02E+ 13 4.0 2.89E+ 14 7.7 7.25E+ 13 1.6 1.80E+ 14 5.2 4535 3.75E+ 14 13.1 2.01E+ 14 9.0 3.19E+ 14 13.7 2.69E+ 14 11.1 4538 2.80E+ 15 182.1 4.92E+ 14 17.6 1.04E+ 15 33.7 1.12E+ 15 56.1 4548 2.03E+ 13 3.8 1.23E+ 12 2.3 5.46E+ 11 2.8 5.00E+ 12 2.7 4554 1.15E+ 14 14.2 2.65E+ 14 6.7 7.34E+ 13 3.2 1.81E+ 14 7.3 4557 8.99E+ 13 7.2 3.18E+ 13 0.5 1.20E+ 13 1.6 3.84E+ 13 2.2 4566 5.29E+ 13 2.6 4.20E+ 13 1.5 4.23E+ 12 1.4 3.39E+ 13 1.7 4580 3.45E+ 14 32.5 1.49E+ 14 10.4 1.94E+ 14 10.2 2.02E+ 14 14.9 4583 8.45E+ 14 48.5 5.28E+ 14 29.6 5.44E+ 14 25.0 5.98E+ 14 32.2 Table 5.2. Winter EAA Particle Emission Rates and PM 10 Mass Emission Rates from Gasoline Vehicles Run # Phase 1 Phase 1 Phase 2 Phase 2 Phase 3 Phase 3 FTP Composite particle/ mi mg/ mi particle/ mi mg/ mi Particle/ mi mg/ mi particle/ mi mg/ mi 4656 4.05E+ 14 168.3 6.66E+ 13 10.9 6.4E+ 13 13.8 1.36E+ 14 44.3 4659 1.17E+ 14 23.9 2.95E+ 12 1.4 6.5E+ 12 1.6 2.75E+ 13 6.1 4662 2.3E+ 14 51.2 7.45E+ 12 0.9 9.84E+ 12 1.4 5.43E+ 13 11.4 4665 1.31E+ 15 283.6 6.73E+ 13 8.9 2.37E+ 13 16.0 3.09E+ 14 67.0 4668 9.94E+ 13 26.7 8.52E+ 12 0.9 3.87E+ 12 0.1 2.61E+ 13 6.0 4671 3.37E+ 13 7.0 9.95E+ 12 1.8 3.44E+ 12 0.9 1.31E+ 13 2.7 4674 3.95E+ 14 87.0 1.5E+ 14 79.2 2.58E+ 14 77.3 2.3E+ 14 80.3 4677 3.32E+ 13 30.4 5.59E+ 12 4.2 6.29E+ 12 12.2 1.15E+ 13 11.8 4680 7.15E+ 13 6.4 3.86E+ 13 0.6 1.86E+ 13 1.2 4E+ 13 2.0 4683 1.08E+ 14 21.2 2.87E+ 13 6.2 1.68E+ 13 5.7 4.18E+ 13 9.2 4687 1.78E+ 14 55.3 9.56E+ 13 42.2 8.97E+ 13 40.9 1.11E+ 14 44.5 4690 5.54E+ 13 8.9 7.01E+ 12 0.1 8.58E+ 12 1.9 1.75E+ 13 2.4 4693 1.21E+ 14 7.2 6.34E+ 13 4.6 2.29E+ 13 2.2 6.42E+ 13 4.5 4695 1.52E+ 15 231.7 9.78E+ 14 163.7 1.13E+ 15 221.0 1.13E+ 15 193.6 4698 3.99E+ 14 29.5 1.8E+ 14 8.2 2.01E+ 14 8.8 2.31E+ 14 12.8 4704 2.87E+ 14 12.9 8.18E+ 14 29.0 4.63E+ 14 20.6 6.1E+ 14 23.4 4707 4.97E+ 14 186.1 3.71E+ 14 47.6 8.04E+ 14 57.6 5.16E+ 14 79.1 4711 4.44E+ 14 97.6 1.43E+ 14 11.9 2.81E+ 14 18.6 2.42E+ 14 31.3 57 4714 3.73E+ 13 6.5 3.24E+ 12 1.8 1.27E+ 12 2.1 9.76E+ 12 2.8 4718 5.14E+ 14 263.3 5.7E+ 14 32.5 5.53E+ 14 59.8 5.54E+ 14 88.0 4721 2.35E+ 14 84.6 4.49E+ 13 18.1 6.92E+ 13 25.4 9.12E+ 13 33.9 4725 3.84E+ 14 659.3 2.4E+ 14 270.7 3.3E+ 14 414.0 2.94E+ 14 390.0 4731 7.79E+ 14 1362.7 3.56E+ 14 1134.9 3.85E+ 14 849.4 4.52E+ 14 1103.7 4735 1.75E+ 14 50.4 9.36E+ 12 4.5 1.75E+ 13 5.5 4.6E+ 13 14.3 4739 6.58E+ 14 711.0 3.31E+ 14 494.3 4.13E+ 14 428.0 4.21E+ 14 520.9 4742 6.04E+ 14 458.7 3.16E+ 14 181.1 2.93E+ 12 268.1 2.9E+ 14 262.5 4745 5.23E+ 13 20.3 8.18E+ 13 20.2 4.4E+ 13 14.8 6.54E+ 13 18.8 4748 3.64E+ 14 302.5 1.99E+ 14 126.9 2.23E+ 14 149.0 2.4E+ 14 169.4 4752 1.57E+ 13 5.2 8.9E+ 11 0.8 1.06E+ 12 0.2 4E+ 12 1.6 4755 3.04E+ 14 85.1 4.78E+ 13 12.6 6.7E+ 13 25.7 1.05E+ 14 30.7 4758 1.14E+ 14 126.4 1.34E+ 14 244.3 9.35E+ 13 134.4 1.19E+ 14 189.8 4761 2.56E+ 13 6.6 1.73E+ 12 0.8 4.5E+ 11 1.5 6.31E+ 12 2.2 4763 1.91E+ 14 56.6 1.32E+ 14 35.9 8.75E+ 13 39.1 1.32E+ 14 41.1 4766 4.18E+ 14 24.0 1.06E+ 14 3.7 8.58E+ 13 8.3 1.65E+ 14 9.1 4769 1.07E+ 13 6.2 3.27E+ 12 1.2 5.57E+ 12 5.2 5.45E+ 12 3.3 4772 1.09E+ 14 9.6 1.13E+ 11 0.0 2.22E+ 11 4.6 2.28E+ 13 3.3 4775 1.86E+ 13 6.3 9.31E+ 12 1.4 2.63E+ 12 2.6 9.39E+ 12 2.7 4778 3.13E+ 12 2.2 7.88E+ 10 0.0 6.25E+ 10 1.0 7.07E+ 11 0.7 4782 2.42E+ 13 17.4 1.43E+ 13 3.1 2.18E+ 13 4.4 1.84E+ 13 6.4 4785 5.18E+ 14 270.6 4.61E+ 14 580.2 3.38E+ 14 270.3 4.39E+ 14 431.1 4788 8.58E+ 14 110.3 3.18E+ 14 20.5 2.01E+ 14 27.2 3.98E+ 14 40.9 4791 2.38E+ 13 3.5 1.29E+ 13 5.2 4.53E+ 12 1.1 1.29E+ 13 3.7 4794 5.6E+ 14 95.6 9.53E+ 13 18.9 3.45E+ 13 14.4 1.75E+ 14 33.5 4797 2.54E+ 14 57.4 5.38E+ 13 5.3 7.8E+ 13 28.9 1.02E+ 14 22.5 4800 4.55E+ 13 14.9 2.89E+ 13 8.8 3.88E+ 13 10.6 3.5E+ 13 10.6 4809 9.25E+ 14 1177.1 3.24E+ 14 109.0 5.54E+ 14 738.0 5.11E+ 14 501.2 4813 2.5E+ 14 58.2 8.83E+ 12 3.6 1.44E+ 14 36.4 9.59E+ 13 23.9 4816 5.86E+ 14 325.1 2.23E+ 14 141.8 2.6E+ 14 119.0 3.09E+ 14 173.5 4819 1.19E+ 14 44.5 2.09E+ 14 132.8 1.73E+ 14 107.1 1.8E+ 14 107.5 4822 7.73E+ 13 30.9 4.96E+ 13 6.6 3.62E+ 13 6.3 5.16E+ 13 11.6 4825 2.46E+ 13 4.1 7.27E+ 11 0.1 1.39E+ 12 1.9 5.84E+ 12 1.4 4828 3.75E+ 13 10.0 1.42E+ 13 0.6 1.46E+ 12 0.2 1.55E+ 13 2.4 4831 3E+ 14 125.4 2.28E+ 14 120.0 2.42E+ 14 167.2 2.47E+ 14 134.1 4834 1.76E+ 14 278.9 2.38E+ 14 653.4 3.14E+ 14 514.4 2.46E+ 14 537.7 4837 2.6E+ 14 70.0 8.52E+ 13 44.4 1.4E+ 14 36.2 1.36E+ 14 47.5 4840 4.55E+ 14 190.8 1.38E+ 14 32.1 2.1E+ 14 41.3 2.23E+ 14 67.4 4844 3.83E+ 14 174.9 1.49E+ 14 30.1 2.13E+ 14 43.0 2.15E+ 14 63.6 4847 6.97E+ 14 385.2 2.84E+ 14 156.2 2.8E+ 14 2.1 3.69E+ 14 161.4 4851 7.71E+ 12 1.9 7.24E+ 12 1.2 2.85E+ 12 1.4 6.14E+ 12 1.4 4854 9.86E+ 12 4.0 4.79E+ 12 1.3 7.65E+ 11 1.9 4.74E+ 12 2.0 4857 1.06E+ 14 50.9 1.03E+ 14 29.7 2.97E+ 13 21.9 8.37E+ 13 31.9 4860 8.23E+ 13 29.7 5.74E+ 13 14.9 5.76E+ 13 13.0 6.26E+ 13 17.5 4863 1.03E+ 13 4.7 2.72E+ 11 1.4 1.76E+ 11 0.2 2.33E+ 12 1.8 4876 1.81E+ 13 23.7 2.02E+ 12 1.9 3.93E+ 11 5.3 4.92E+ 12 7.4 4879 4.21E+ 14 235.6 5.94E+ 13 9.6 1.85E+ 14 15.8 1.68E+ 14 57.9 4882 1.61E+ 14 53.9 5.15E+ 14 117.2 1.92E+ 14 35.3 3.53E+ 14 81.7 4885 9.92E+ 13 16.4 1.46E+ 14 23.0 1.18E+ 13 6.6 9.96E+ 13 17.1 Table 5.3. Winter EAA Particle Emission Rates and PM 10 Mass Emission Rates from 58 Diesel Vehicles Run # Phase 1 Phase 1 Phase 2 Phase 2 Phase 3 Phase 3 FTP Composite particle/ mi mg/ mi particle/ mi mg/ mi particle/ mi mg/ mi particle/ mi mg/ mi 4891 4.22E+ 14 99.8 3.37E+ 14 69.0 2.37E+ 14 ND 3.28E+ 14 ND 4894 3.83E+ 14 525.5 4.36E+ 14 543.9 3.68E+ 14 530.4 4.06E+ 14 536.4 4897 3.7E+ 14 602.9 3.06E+ 14 229.3 2.95E+ 14 354.9 3.16E+ 14 341.2 4900 9.31E+ 14 940.4 6.75E+ 14 383.4 7.93E+ 14 646.5 7.6E+ 14 570.1 4903 1.02E+ 15 866.6 8.4E+ 14 407.3 7.94E+ 14 642.7 8.65E+ 14 566.7 4907 1.03E+ 15 1129.1 1.09E+ 15 789.5 7.13E+ 14 1045.6 9.71E+ 14 930.0 4910 6.45E+ 14 940.7 4.79E+ 14 724.7 4.06E+ 14 830.8 4.93E+ 14 798.5 4913 7.15E+ 14 1120.7 2.4E+ 14 416.7 4.1E+ 14 528.4 3.85E+ 14 593.1 4916 4.24E+ 14 474.7 5.72E+ 14 310.7 4.4E+ 14 329.7 5.05E+ 14 349.9 4919 4.82E+ 14 388.9 5.94E+ 14 136.8 4.77E+ 14 281.4 5.39E+ 14 228.5 4926 4.6E+ 14 240.4 3.53E+ 14 121.8 4.22E+ 14 162.4 3.94E+ 14 157.3 4929 5.31E+ 14 1056.3 3.41E+ 14 373.4 3.89E+ 14 498.2 3.93E+ 14 546.8 59 Particle size distributions. Particle size distributions were taken with MOUDI impactors. During the summer an eight stage impactor with a final stage cutpoint of 0.19 µ m was used. Considerable difficulty was experienced with this measurement. High emission vehicles tended to plug the impactor while low emission vehicles provided insufficient mass for weighing. The plugging was determined to primarily be caused by the Teflo final filter. We assume that the very small particles reaching this filter penetrated into the pores and plugged them. All but seven size distributions were rejected. During the winter a ten stage impactor with a final stage cutpoint of 0.068 µ m was used. This impactor has finer particle size resolution than the one used in the summer. Thus, a lower percentage of the mass was deposited on the final filter. In addition, the final filter was switched from a 2 µ m pore size Teflo filter to a Pallflex T60A20 filter. Results were much better.

The impactors were operated continuously over the entire FTP, except for a few runs in the summer when the run was terminated early due to plugging. Examination of size distributions for the low PM emitters indicated some variability in the impactor stage blank values, with a tendency towards decreasing blanks throughout the winter portion of the study. Therefore, subjective judgment was necessary in choosing the blank correction value for each sample. In all cases, a blank was used that resulted in no impactor stages with a negative mass change. Uncertainty in the blank adds uncertainty to the overall particle size distributions, especially for the low emission vehicles. This should be kept in mind when examining the following data.

Figure 5.6 shows two typical particle size distributions from diesel vehicles and two from smoking gasoline vehicles from the winter study. In all cases the maximum collected mass is on the 0.22 µ m cutpoint stage. Figure 5.7 shows distributions from four gasoline winter vehicles. The maximum collected mass is on either the 0.12 or the 0.22 cutpoint stage. There is some indication of bimodal distributions for the gasoline vehicles, with the second mass mode at larger particle diameters. Most of the gasoline vehicle size distributions are for older vehicles, since there was insufficient mass collected from the newer vehicles to provide accurate impactor size distributions. It must be remembered that because the impaction foils were not coated with grease, particle bounce and particle loss in the impactor were probably significant ( Lawson, 1980). Coated impaction foils were not used since the chance of losing mass during handling foils is high, and collected sample mass was low.