Fine particle emissions from on-road vehicles in the Zhujiang Tunnel, China

Little is known about the characteristics of particulate matter emissions from vehicles in China, although such information is critical in source apportionment modeling, emission inventories, and health effect studies. In this paper, we report a comprehensive characterization of PM2.5 emissions in the Zhujiang Tunnel in the Pearl River Delta region of China. The chemical speciation included elemental carbon, organic carbon, inorganic ions, trace elements, and organic compounds. The emission factors of individual species and their relative distributions were obtained for a mixed fleet of heavy-duty vehicles (19.8%) and light-duty vehicles (80.2%). In addition, separate emission factors of PM2.5 mass, elemental carbon, and organic matter for heavy-duty vehicles and light-duty vehicles also were derived. As compared to the results of other tunnel studies previously conducted, we found that the abundances and distributions of the trace elements in PM2.5 emissions were more varied. In contrast, the characteristics of the trace organic compounds in the PM2.5 emissions in our study were consistent with characteristics found in other tunnel studies and dynamometer tests. Our results suggested that vehicular PM2.5 emissions of organic compounds are less influenced by the geographic area and fleet composition and thereby are more suitable for use in aerosol source apportionment modeling implemented across extensive regions.     

Lubricating oil and fuel contributions to particulate matter emissions from light-duty gasoline and heavy-duty diesel vehicles

Size-resolved particulate matter emissions from heavy-duty diesel vehicles (HDDVs) and light-duty gasoline vehicles (LDGVs) operated under realistic driving cycles were analyzed for elemental carbon (EC), organic carbon (OC), hopanes, steranes, and polycyclic aromatic hydrocarbons. Measured hopane and sterane size distributions did not match the total carbon size distribution in most cases, suggesting that lubricating oil was not the dominant source of particulate carbon in the vehicle exhaust. A regression analysis using 17alpha(H)-21beta(H)-29-norhopane as a tracer for lubricating oil and benzo[ghi/perylene as a tracer for gasoline showed that gasoline fuel and lubricating oil both make significant contributions to particulate EC and OC emissions from LDGVs. A similar regression analysis performed using 17alpha(H)-21beta(H)-29-norhopane as a tracer for lubricating oil and flouranthene as a tracerfor diesel fuel was able to explain the size distribution of particulate EC and OC emissions from HDDVs. The analysis showed that EC emitted from all HDDVs operated under relatively high load conditions was dominated by diesel fuel contributions with little EC attributed to lubricating oil. Particulate OC emitted from HDDVs was more evenly apportioned between fuel and oil contributions. EC emitted from LDGVs operated underfuel-rich conditions was dominated by gasoline fuel contributions. OC emitted from visibly smoking LDGVs was mostly associated with lubricating oil, but OC emitted from all other categories of LDGVs was dominated by gasoline fuel. The current study clearly illustrates that fuel and lubricating oil make separate and distinct contributions to particulate matter emissions from motor vehicles. These particles should be tracked separately during ambient source apportionment studies since the atmospheric evolution and ultimate health effects of these particles may be different. The source profiles for fuel and lubricating oil contributions to EC and OC emissions derived in this study provide a foundation for future source apportionment calculations.     

Contribution of lubricating oil to particulate matter emissions from light-duty gasoline vehicles in Kansas City

The contribution of lubricating oil to particulate matter (PM) emissions representative of the in-use 2004 light-duty gasoline vehicles fleet is estimated from the Kansas City Light-Duty Vehicle Emissions Study (KCVES). PM emissions are apportioned to lubricating oil and gasoline using aerosol-phase chemical markers measured in PM samples obtained from 99 vehicles tested on the California Unified Driving Cycle. The oil contribution to fleet-weighted PM emission rates is estimated to be 25% of PM emission rates. Oil contributes primarily to the organic fraction of PM, with no detectable contribution to elemental carbon emissions. Vehicles are analyzed according to pre-1991 and 1991-2004 groups due to differences in properties of the fitting species between newer and older vehicles, and to account for the sampling design of the study. Pre-1991 vehicles contribute 13.5% of the KC vehicle population, 70% of oil-derived PM for the entire fleet, and 33% of the fuel-derived PM. The uncertainty of the contributions is calculated from a survey analysis resampling method, with 95% confidence intervals for the oil-derived PM fraction ranging from 13% to 37%. The PM is not completely apportioned to the gasoline and oil due to several contributing factors, including varied chemical composition of PM among vehicles, metal emissions, and PM measurement artifacts. Additional uncertainties include potential sorption of polycyclic aromatic hydrocarbons into the oil, contributions of semivolatile organic compounds from the oil to the PM measurements, and representing the in-use fleet with a limited number of vehicles.     

Optimization-based source apportionment of PM2.5 incorporating gas-to-particle ratios

A modified approach to PM2.5 source apportionment is developed, using source indicative SO2/PM2.5, CO/PM2.5, and NOx/PM2.5 ratios as constraints, in addition to the commonly used particulate-phase source profiles. Additional information from using gas-to-particle ratios assists in reducing collinearity between source profiles, a problem that often limits the source-identification capabilities and accuracy of traditional receptor models. This is especially true in the absence of speciated organic carbon measurements. In the approach presented here, the solution is based on a global optimization mechanism, minimizing the weighted error between apportioned and ambient levels of PM2.5 components, while introducing constraints on calculated source contributions that ensure that the ambient gas-phase pollutants (SO2, CO, and NOy) are reasonable. This technique was applied to a 25-month dataset of daily PM2.5 measurements (total mass and composition) at the Atlanta Jefferson Street SEARCH site. Results indicate that this technique was able to split the contributions of mobile sources (gasoline and diesel vehicles) more accurately than particulate-phase source apportionment methods. Furthermore, this technique was able to better quantify the direct contribution (primary PM2.5) of coal-fired power plants to ambient PM2.5 levels.     

Size distribution of trace organic species emitted from heavy-duty diesel vehicles

Size distributions of particulate hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs) were measured in the exhaust from four heavy-duty diesel vehicles (HDDVs) operated under idle, creep, transient, and two high-speed driving modes. Particulate matter was collected using a chassis dynamometer and a dilution sampling system equipped with cascade impactors and filter samplers. Samples were extracted using organic solvents and analyzed using gas chromatography-mass spectrometry. Size distributions of hopanes and steranes were functions of engine load conditions and vehicle technology. Hopanes and steranes peaked in size ranges larger than 0.18 microm aerodynamic particle diameter under light load conditions and less than 0.10 microm aerodynamic particle diameter under heavier load conditions. The eight hopane size distributions emitted from newertechnology (> 1998) vehicles were unimodal while the four hopane size distributions emitted from older technology vehicles (< 1992) were bimodal. Similar trends between older and newer vehicles were not observed for sterane size distributions. The PAH composition emitted from HDDVs was a function of driving cycle and vehicle technology. Light driving cycles produced quantifiable emissions of 3, 4, 5, and 6 ring PAHs (including coronene). Heavier driving cycles produced only the 3 and 4 ring PAHs in quantifiable amounts. PM1.8 and PM0.1 source profiles constructed using the relative abundance of hopanes and steranes to total organic carbon were functions of vehicle load condition. Increasing load reduced the relative abundance of motor oil tracers in the PM1.8 size fraction and increased the abundance of these tracers in the PM0.1 size fraction. The relative abundances of PAHs in the PM0.1 and PM1.8 size fractions emitted from the oldest vehicle tested (1985 HDDV) were significantly higher than for any other vehicle tested.     

Emissions of toxic pollutants from compressed natural gas and low sulfur diesel-fueled heavy-duty transit buses tested over multiple driving cycles

The number of heavy-duty vehicles using alternative fuels such as compressed natural gas (CNG) and new low-sulfur diesel fuel formulations and equipped with after-treatment devices are projected to increase. However, few peer-reviewed studies have characterized the emissions of particulate matter (PM) and other toxic compounds from these vehicles. In this study, chemical and biological analyses were used to characterize the identifiable toxic air pollutants emitted from both CNG and low-sulfur-diesel-fueled heavy-duty transit buses tested on a chassis dynamometer over three transient driving cycles and a steady-state cruise condition. The CNG bus had no after-treatment, and the diesel bus was tested first equipped with an oxidation catalyst (OC) and then with a catalyzed diesel particulate filter (DPF). Emissions were analyzed for PM, volatile organic compounds (VOCs; determined on-site), polycyclic aromatic hydrocarbons (PAHs), and mutagenic activity. The 2000 model year CNG-fueled vehicle had the highest emissions of 1,3-butadiene, benzene, and carbonyls (e.g., formaldehyde) of the three vehicle configurations tested in this study. The 1998 model year diesel bus equipped with an OC and fueled with low-sulfur diesel had the highest emission rates of PM and PAHs. The highest specific mutagenic activities (revertants/microg PM, or potency) and the highest mutagen emission rates (revertants/mi) were from the CNG bus in strain TA98 tested over the New York Bus (NYB) driving cycle. The 1998 model year diesel bus with DPF had the lowest VOCs, PAH, and mutagenic activity emission. In general, the NYB driving cycle had the highest emission rates (g/mi), and the Urban Dynamometer Driving Schedule (UDDS) had the lowest emission rates for all toxics tested over the three transient test cycles investigated. Also, transient emissions were, in general, higher than steady-state emissions. The emissions of toxic compounds from an in-use CNG transit bus (without an oxidation catalyst) and from a vehicle fueled with low-sulfur diesel fuel (equipped with DPF) were lower than from the low-sulfur diesel fueled vehicle equipped with OC. All vehicle configurations had generally lower emissions of toxics than an uncontrolled diesel engine. Tunnel backgrounds (measurements without the vehicle running) were measured throughout this study and were helpful in determining the incremental increase in pollutant emissions. Also, the on-site determination of VOCs, especially 1,3-butadiene, helped minimize measurement losses due to sample degradation after collection.     

Separation of fine particulate matter emitted from gasoline and diesel vehicles using chemical mass balancing techniques

Samples of fine particulate matter were collected in a roadway tunnel near Houston, TX over a period of 4 days during two separate sampling periods: one sampling period from 1200 to 1400 local time and another sampling period from 1600 to 1800 local time. During the two sampling periods, the tunnel traffic contained roughly equivalent numbers of heavy-duty diesel trucks. However, during the late afternoon sampling period, the tunnel contained twice as many light-duty gasoline-powered vehicles. The effect of this shift in the vehicle fleet affects the overall emission index (grams pollutant emitted per kilogram carbon in fuel) for fine particles and fine particulate elemental carbon. Additionally, this shift in the fraction of diesel vehicles in the tunnel is used to determine if the chemical mass balancing techniques used to track emissions from gasoline-powered and diesel-powered emissions accurately separates these two emission categories. The results show that the chemical mass balancing calculations apportion roughly equal amounts of the particulate matter measured to diesel vehicles between the two periods and attribute almost twice as much particulate matter in the late afternoon sampling period to gasoline vehicles. Both of these results are consistent with the traffic volume of gasoline and diesel vehicles in the tunnel in the two separate periods and validate the ability for chemical mass balancing techniques to separate these two primary sources of fine particles.     

Gaseous and particulate emissions from prescribed burning in Georgia

Prescribed burning is a significant source of fine particulate matter (PM2.5) in the southeastern United States. However, limited data exist on the emission characteristics from this source. Various organic and inorganic compounds both in the gas and particle phase were measured in the emissions of prescribed burnings conducted at two pine-dominated forest areas in Georgia. The measurements of volatile organic compounds (VOCs) and PM2.5 allowed the determination of emission factors for the flaming and smoldering stages of prescribed burnings. The VOC emission factors from smoldering were distinctly higher than those from flaming except for ethene, ethyne, and organic nitrate compounds. VOC emission factors show that emissions of certain aromatic compounds and terpenes such as alpha and beta-pinenes, which are important precursors for secondary organic aerosol (SOA), are much higher from active prescribed burnings than from fireplace wood and laboratory open burning studies. Levoglucosan is the major particulate organic compound (POC) emitted for all these studies, though its emission relative to total organic carbon (mg/g OC) differs significantly. Furthermore, cholesterol, an important fingerprint for meat cooking, was observed only in our in situ study indicating a significant release from the soil and soil organisms during open burning. Source apportionment of ambient primary fine particulate OC measured at two urban receptor locations 20-25 km downwind yields 74 +/- 11% during and immediately after the burns using our new in situ profile. In comparison with the previous source profile from laboratory simulations, however, this OC contribution is on average 27 +/- 5% lower.     

Emissions of metals associated with motor vehicle roadways

Emissions of metals and other particle-phase species from on-road motor vehicles were measured in two tunnels in Milwaukee, WI during the summer of 2000 and winter of 2001. Emission factors were calculated from measurements of fine (PM2.5) and coarse (PM10) particulate matter at tunnel entrances and exits, and effects of fleet composition and season were investigated. Cascade impactors (MOUDI) were used to obtain size-resolved metal emission rates. Metals were quantified with inductively-coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF). PM10 emission rates ranged from 38.7 to 201 mg km(-1) and were composed mainly of organic carbon (OC, 30%), inorganic ions (sulfate, chloride, nitrate, ammonium, 20%), metals (19%), and elemental carbon (EC, 9.3%). PM10 metal emissions were dominated by crustal elements Si, Fe, Ca, Na, Mg, Al, and K, and elements associated with tailpipe emissions and brake and tire wear, including Cu, Zn, Sb, Ba, Pb, and S. Metals emitted in PM2.5 were lower (11.6% of mass). Resuspension of roadway dust was dependent on weather and road surface conditions, and increased emissions were related to higher traffic volumes and fractions of heavy trucks. Emission of noble metals from catalytic converters appeared to be impacted by the presence of older vehicles. Elements related to brake wear were impacted by enriched road dust resuspension, but correlations between these elements in PM2.5 indicate that direct brake wear emissions are also important. A submicrometer particle mode was observed in the emissions of Pb, Ca, Fe, and Cu.     

Electric vehicles in China: emissions and health impacts

E-bikes in China are the single largest adoption of alternative fuel vehicles in history, with more than 100 million e-bikes purchased in the past decade and vehicle ownership about 2× larger for e-bikes as for conventional cars; e-car sales, too, are rapidly growing. We compare emissions (CO(2), PM(2.5), NO(X), HC) and environmental health impacts (primary PM(2.5)) from the use of conventional vehicles (CVs) and electric vehicles (EVs) in 34 major cities in China. CO(2) emissions (g km(-1)) vary and are an order of magnitude greater for e-cars (135-274) and CVs (150-180) than for e-bikes (14-27). PM(2.5) emission factors generally are lower for CVs (gasoline or diesel) than comparable EVs. However, intake fraction is often greater for CVs than for EVs because combustion emissions are generally closer to population centers for CVs (tailpipe emissions) than for EVs (power plant emissions). For most cities, the net result is that primary PM(2.5) environmental health impacts per passenger-km are greater for e-cars than for gasoline cars (3.6× on average), lower than for diesel cars (2.5× on average), and equal to diesel buses. In contrast, e-bikes yield lower environmental health impacts per passenger-km than the three CVs investigated: gasoline cars (2×), diesel cars (10×), and diesel buses (5×). Our findings highlight the importance of considering exposures, and especially the proximity of emissions to people, when evaluating environmental health impacts for EVs.     

Size-resolved source apportionment of airborne particle mass in a roadside environment

Airborne particulate hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs) were measured in six size fractions < 1.8 microm particle diameter at one site upwind and two sites downwind of the Interstate 5 freeway in San Diego, CA. The smallest size fraction collected was exclusively in the ultrafine size range (D(p) < 0.1 microm; PM0.1). Size distributions of hopanes, steranes, and PAHs peaked between 0.10-0.18 microm particle aerodynamic diameter with a tail extending into the PM0.1 size range. This pattern is similar to previous dynamometer studies of hopane, sterane, and PAH size distributions emitted from gasoline- and diesel-powered vehicles. Size-resolved source profiles were combined to form an "on-road" profile for motor oil, diesel, and gasoline contributions to EC and OC. The resulting equations were used to predict source contributions to the size distributions of EC and OC in the roadside environment. The method successfully accounted for the majority of the carbonaceous material in particles with diameter < 0.18 microm, with significant residual material in larger size fractions. The peak in both the measured and predicted EC size distribution occurred between 0.1-0.18 microm particle aerodynamic diameter. The predicted OC size distribution peaked between 0.1-0.18 microm particle diameter, butthe measured OC size distribution peaked between 0.56-1.0 microm particle diameter, possibly because of secondary organic aerosol formation. Predicted OC concentrations in particles with diameter < 0.18 microm were greater than measured values 18 m downwind of the roadway but showed good agreement 37 m downwind. The largest source contributions to the PM0.1 and PM0.18 size fractions were different. PM0.18 was dominated by diesel fuel and motor oil combustion products while PM0.1 was dominated by diesel fuel and gasoline fuel combustion products. Total source contributions to ultrafine (PM0.1) EC concentrations 37 m downwind of the roadway were 44 +/- 6% diesel fuel, 21 +/- 1% gasoline, 5 +/- 6% motor oil, and 30% unknown. Total source contributions to ultrafine (PM0.1) OC concentrations 37 m downwind of the roadway were 46 +/- 5% diesel fuel, 44 +/- 5% gasoline, 20 +/- 15% motor oil with a slight overprediction (11%). Diesel fuel appears to make the single largest contribution to ultrafine (PM0.1) particle mass given the fleet distribution during the current experiment.     

Source apportionment of polycyclic aromatic hydrocarbons in the urban atmosphere: a comparison of three methods

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in urban atmospheres. Several PAHs are known carcinogens or are the precursors to carcinogenic daughter compounds. Understanding the contributions of the various emission sources is critical to appropriately managing PAH levels in the environment. The sources of PAHs to ambient air in Baltimore, MD, were determined by using three source apportionment methods, principal component analysis with multiple linear regression, UNMIX, and positive matrix factorization. Determining the source apportionment through multiple techniques mitigates weaknesses in individual methods and strengthens the overlapping conclusions. Overall source contributions compare well among methods. Vehicles, both diesel and gasoline, contribute on average 16-26%, coal 28-36%, oil 15-23%, and wood/other having the greatest disparity of 23-35% of the total (gas- plus particle-phase) PAHs. Seasonal trends were found for both coal and oil. Coal was the dominate PAH source during the summer while oil dominated during the winter. Positive matrix factorization was the only method to segregate diesel from gasoline sources. These methods indicate the number and relative strength of PAH sources to the ambient urban atmosphere. As with all source apportionment techniques, these methods require the user to objectively interpret the resulting source profiles.     

On-road particulate matter (PM2.5 and PM10) emissions in the Sepulveda Tunnel, Los Angeles, California

Total and speciated particulate matter (PM2.5 and PM10) emission factors from in-use vehicles were measured for a mixed light- (97.4% LD) and heavy-duty fleet (2.6% HD) in the Sepulveda Tunnel, Los Angeles, CA. Seventeen 1-h test runs were performed between July 23, 1996, and July 27, 1996. Emission factors were calculated from mass concentration measurements taken at the tunnel entrance and exit, the volume of airflow through the tunnel, and the number of vehicles passing through the 582 m long tunnel. For the mixed LD and HD fleet, PM2.5 emission factors in the Sepulveda Tunnel ranged from 0.016 (+/-0.007) to 0.115 (+/-0.019) g/vehicle-km traveled with an average of 0.052 (+/-0.027) g/vehicle.km. PM10 emission factors ranged from 0.030 (+/-0.009) to 0.131 (+/-0.024) g/vehicle. km with an average of 0.069 (+/-0.030) g/vehicle.km. The PM2.5 emission factor was approximately 74% of the PM10 factor. Speciated emission rates and chemical profiles for use in receptor modeling were also developed. PM2.5 was dominated by organic carbon (OC) (31.0 +/- 19.5%) and elemental carbon (EC) (48.5 +/- 20.5%) that together account for 79% (+/-24%) of the total emissions. Crustal elements (Fe, Mg, Al, Si, Ca, and Mn) contribute approximately 7.8%, and the ions Cl-, NO3-, NH3+, SO4(2-), and K+ together constitute another 9.8%. In the PM10 size fraction the particulate emissions were also dominated by OC (31 +/- 12%) and EC (35 +/- 13%). The third most prominent species was Fe (18.5 +/- 9.0%), which is greater than would be expected from purely geological sources. Other geological components (Mg, Al, Si, K, Ca, and Mn) accounted for an additional 12.6%. PM10 emission factors showed some dependence on vehicle speed, whereas PM2.5 did not. For test runs in which the average vehicle speed was 42.6 km/h a 1.7 times increase in PM10 emission factor was observed compared to those runs with an average vehicle speed of 72.6 km/h. Speciated emissions were similar. However, there is significantly greater mass attributable to geological material in the PM10, indicative of an increased contribution from resuspended road dust. The PM2.5 shows relatively good correlation with NOx emissions, which indicates that even at the low percent of HD vehicles, which emit significantly more NOx than LD vehicles, they may also have a significant impact on the PM2.5 levels.     

Source apportionment of molecular markers and organic aerosol--1. Polycyclic aromatic hydrocarbons and methodology for data visualization

Individual organic compounds often referred to as molecular markers are used in conjunction with the chemical mass balance (CMB) model to apportion sources of primary organic aerosol. This paper presents a methodology to visualize molecular marker data; it allows comparison of ambient data and source profiles and allows assessment of chemical stability and aging. The method is intended to complement traditional quantitative source apportionment analysis. The core of the technique involves construction of plots of ratios of species concentrations (ratio-ratio plots) in which source profiles appear as points connected by linear mixing lines. The approach is illustrated using data collected over a 1-year period in Pittsburgh, Pennsylvania. The analysis considers for elemental carbon and a number of high molecular weight polycyclic aromatic hydrocarbons (PAHs) commonly used as molecular markers in CMB: benzo(b+j+k)fluoranthene, benzo(e)pyrene, benzo[g,h,i]perylene, coronene, and indeno(1,2,3-cd)pyrene. In Pittsburgh, the ambient concentrations of these PAHs are higher than in other cities in the United States; they are also strongly correlated consistent with a single, dominant source. Both ratio-ratio plots and CMB analysis indicate that this source is metallurgical coke production. Although emissions from coke production dominate ambient PAH concentrations, on most study days they contributed little fine particle mass. Ratio-ratio plots are then used to investigate the feasibility of using PAHs to help differentiate between gasoline and diesel vehicle emissions. Ambient concentrations of these large PAHs provide little information on the gasoline-diesel split because of the strong influence of local emissions from coke production combined with evidence of photochemical decay of PAHs in the regional air mass. Decay of PAHs will bias estimates of the gasoline-diesel split toward diesel emissions.     

Tracking petroleum refinery emission events using lanthanum and lanthanides as elemental markers for PM2.5

Fine particulate matter levels at four air sampling stations in the Houston, TX area are apportioned to quantify the impact of emissions from a local refinery during a reported emission event. Through quantification of lanthanum and lanthanides using a recently developed analytical technique, the impacts of emissions from fluidized-bed catalytic cracking (FCC) units are quantitatively tracked across the Houston region. The results show a significant (33-106-fold) increase in contributions of FCC emissions to PM2.5 compared with background levels associated with routine operation. This impact from industrial emissions to ambient air quality occurs simultaneously with a larger, regional haze episode that lead to elevated PM2.5 concentrations throughout the entire region. By focusing on detailed chemical analysis of unique maker metals (lanthanum and lanthanides), the impact of emissions from the FCC unit was tracked from the local refinery that reported the emission event to a site approximately 50 km downwind, illustrating the strength of the analytical method to isolate an important source during a regional haze episode not related to the emission event. While this source apportionment technique could separate contributions from FCC emissions, improved time-resolved sampling is proposed to more precisely quantify the impacts of transient emission events on ambient PM2.5.     

Size distribution of trace organic species emitted from light-duty gasoline vehicles

Size distributions for particulate hopanes+steranes and nonvolatile polycyclic aromatic hydrocarbons (PAHs) emitted from five classes of light-duty gasoline-powered vehicles were measured using the federal test procedure (FTP), unified cycle (UC), and correction cycle (CC) driving cycles. 17alpha(H)-21beta(H)-29-norhopane, 17alpha(H)-21beta(H)-hopane, alpha beta beta-20R-stigmastane, and alpha beta beta-20S-stigmastane were highly correlated and behaved consistently across sampling methods. Coronene and benzo[ghi]perylene were the most ubiquitous heavy PAHs detected in the vehicle exhaust. The emission rates of hopanes, steranes, and PAHs contained in particles with aerodynamic diameters of less than 1.8 ,m varied by 2 orders of magnitude between the lowest- and highest-emitting vehicle classes. Hopane+sterane size distributions emitted from vehicles without an operating catalyst (including "cold-start" emissions from catalyst-equipped vehicles) were bimodal with one mode between 0.10 and 0.18 microm and the second mode >0.32 microm particle diameter. Hopane+sterane emissions released from vehicles with a catalyst at operating temperature had a single mode between 0.1 and 0.18 microm diameter. Hopane+sterane emissions from visibly smoking vehicles had a single mode between 0.18 and 0.32 microm diameter. Heavy PAH size distributions for all vehicle classes consistently had a single mode between 0.10 and 0.18 microm particle diameter (0.1-0.32 microm diameter for smoking vehicles). The geometric standard deviations for PAH size distributions were generally smaller than the corresponding hopane+sterane distributions. These trends suggest that hopanes+steranes and heavy PAHs act as tracers for separate processes of particulate organic carbon formation. PAH and hopane+sterane emissions shifted to smaller sizes during the more aggressive UC and CC driving cycles relative to the FTP. The fraction of PAH and hopane+sterane emissions in the ultrafine (Dp < 0.1 microm) range more than doubled during "warm-start" UC and CC cycles vs the FTP cycle. The enhancement of ultrafine PAHs during "cold-start" UC driving cycles was less pronounced.     

Development and application of a mobile laboratory for measuring emissions from diesel engines. 2. Sampling for toxics and particulate matter

Limited data are available on the emission rates of speciated volatile and semivolatile organic compounds, as well as the physical and chemical characteristics of fine particulate matter (PM) from mobile, in-use diesel engines operated on the road. A design for the sampling of these fractions and the first data from in-use diesel sources are presented in this paper. Emission rates for carbonyls, 1,3-butadiene, benzene, toluene, xylene, PM, and elemental and organic carbon (EC and OC) are reported for a vehicle driven while following the California Air Resources Board (ARB) four-mode heavy heavy-duty diesel truck (HHDDT) cycle and while transiting through a major transportation corridor. Results show that distance specific emission rates are substantially greater in congested traffic as compared with highway cruise conditions. Specifically, emissions of toxic compounds are 3-15 times greater, and PM is 7 times greater under these conditions. The dependence of these species on driving mode suggests that health and source apportionment studies will need to account for driving patterns in addition to emission factors. Comparison of the PM/NOx ratios obtained for the above tests provides insight into the presence and importance of "off-cycle" emissions during on-road driving. Measurements from a stationary source (operated and tested at constant engine speed) equipped with an engine similar to that in the HHDDT yielded a greater understanding of the relative dependence of emissions on load versus engine transients. These data are indicative of the type of investigations made possible by the development of this novel laboratory.     

Exposure to particulate matter,volatile organic compounds,and other air pollutants inside patrol cars

People driving in a vehicle might receive an enhanced dose of mobile source pollutants that are considered a potential risk for cardiovascular diseases. The exposure to components of air pollution in highway patrol vehicles, at an ambient, and a roadside location was determined during 25 work shifts (3 p.m. to midnight) in the autumn of 2001, each day with two cars. A global positioning system and a diary provided location and activity information. Average pollutant levels inside the cars were low compared to ambient air quality standards: carbon monoxide 2.7 ppm, nitrogen dioxide 41.7 microg/m3, ozone 11.7 ppb, particulate matter smaller 2.5 microm (PM2.5) 24 microg/m3. Volatile organic compounds inside the cars were in the ppb-range and showed the fingerprint of gasoline. PM2.5 was 24% lower than ambient and roadside levels, probably due to depositions associated with the recirculating air conditioning. Levels of carbon monoxide, aldehydes, hydrocarbons, and some metals (Al, Ca, Ti, V, Cr, Mn, Fe, Cu, and Sr) were highest in the cars, and roadside levels were higher than ambient levels. Elevated pollutant levels were related to locations with high traffic volumes. Our results point to combustion engine emissions from other vehicles as important sources of air pollutants inside the car.     

Size distribution of particle-phase molecular markers during a severe winter pollution episode

Airborne particulate matter was collected using filter samplers and cascade impactors in six size fractions below 1.8 microm during a severe winter air pollution event at three sites in the Central Valley of California. The smallest size fraction analyzed was 0.056 < Dp <0.1 microm particle diameter, which accounts for the majority of the mass in the ultrafine (PM0.1) size range. Separate samples were collected during the daytime (10 a.m. to 6 p.m. PST) and nighttime (8 p.m. to 8 a.m. PST) to characterize diurnal patterns. Each sample was extracted with organic solvents and analyzed using gas chromatography mass spectrometry for molecular markers that can be used for size-resolved source apportionment calculations. Colocated impactor and filter measurements were highly correlated (R8 > 0.8) for retene, benzo[ghi]flouranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, perylene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, coronene, MW302 polycyclic aromatic hydrocarbon (PAHs), 17beta(H)-21alpha(H)-30-norhopane, 17alpha(H)-21beta(H)-hopane, alphabetabeta-20R-C29-ethylcholestane, levoglucosan, and cholesterol. Of these compounds, levoglucosan was present in the highest concentration (60-2080 ng m(-3)) followed by cholesterol (6-35 ng m(-3)), PAHs (2-38 ng m(-3)), and hopanes and steranes (0-2 ng m(-3)). Nighttime concentrations were higher than daytime concentrations in all cases. Organic compound size distributions were generally similar to the total carbon size distributions during the nighttime but showed greater variability during the daytime. This may reflect the dominance of fresh emission in the stagnant surface layer during the evening hours and the presence of aged organic aerosol at the surface during the daytime when the atmosphere is better mixed. All of the measured organic compound particle size distributions had a single mode that peaked somewhere between 0.18 and 0.56 microm, but the width of each distribution varied by compound. Cholesterol generally had the broadest particle size distribution, while benzo[ghi]perylene and 17alpha(H)-21beta(H)-29-norhopane generally had sharper peaks. The difference between the size distributions of the various particle-phase organic compounds reflects the fact that these compounds exist in particles emitted from different sources. The results of the current study will prove useful for size-resolved source apportionment exercises.     

Unregulated emissions from a heavy-duty diesel engine with various fuels and emission control systems

This study evaluated the effects of various combinations of fuels and emission control technologies on exhaust emissions from a heavy-duty diesel engine tested on an engine dynamometer. Ten fuels were studied in twenty four combinations of fuel and emission control technology configurations. Emission control systems evaluated were diesel oxidation catalyst (DOC), continuously regenerating diesel particulate filter (CRDPF), and the CRDPF coupled with an exhaust gas recirculation system (EGRT). The effects of fuel type and emission control technology on emissions of benzene, toluene, ethylbenzene, xylene (BTEX), and 1,3-butadiene, elemental carbon and organic carbon (EC/OC), carbonyls, polycyclic aromatic hydrocarbons (PAHs), and nitro-PAHs (n-PAHs) are presented in this paper. Regulated gaseous criteria pollutants of total hydrocarbons (THC), carbon monoxide (CO), oxides of nitrogen (NO(x)) and particulate matter (PM) emissions have been reported elsewhere. In general, individual unregulated emission with a CRDPF or an EGRT system is similar (at very low emission level) or much lower than that operating solely with a DOC and choosing a "best" fuel. The water emulsion PuriNO(x) fuel exhibited higher BTEX, carbonyls and PAHs emissions compared to other ultralow sulfur diesel (ULSD) fuels tested in this study while n-PAH emissions were comparable to that from other ULSD fuels. Naphthalene accounted for greater than 50% of the total PAH emissions in this study and there was no significant increase of n-PAHs with the usage of CRDPF.