John C. Sagebiel

Emission Rates and Comparative Chemical Composition from Selected In-Use Diesel and Gasoline-Fueled Vehicles

Abstract Emission samples for toxicity testing and detailed chemical characterization were collected from a variety of gasoline- and diesel-fueled in-use vehicles operated on the Unified Driving Cycle on a chassis dynamometer. Gasoline vehicles included normal particle mass (particulate matter [PM]) emitters (tested at 72 and 30°F), “black” and “white” smokers, and a new-technology vehicle (tested at 72 °F). Diesel vehicles included current-technology vehicles (tested at 72 and 30°F) and a high PM emitter. Total PM emission rates ranged from below 3 mg/mi up to more than 700 mg/mi for the white smoker gasoline vehicle. Emission rates of organic and elemental carbon (OC/EC), elements (metals and associated analytes), ions, and a variety of particulate and semi-volatile organic compounds (polycyclic aromatic hydrocarbons [PAH], nitro-PAH, oxy-PAH, hopanes, and steranes) are reported for these vehicles. Speciated organic analysis also was conducted on the fuels and lube oils obtained from these vehicles after the emissions testing. The compositions of emissions were highly dependent on the fuel type (gasoline vs. diesel), the state of vehicle maintenance (low, average, or high emitters; white or black smokers), and ambient conditions (i.e., temperature) of the vehicles. Fuel and oil analyses from these vehicles showed that oil served as a repository for combustion byproducts (e.g., PAH), and oil-burning gasoline vehicles emitted PAH in higher concentrations than did other vehicles. These PAH emissions matched the PAH compositions observed in oil.

Real-world automotive emissions : Summary of studies in the Fort McHenry and Tuscarora Mountain Tunnels

Al~ract--Motor vehicle emission rates of CO, NO, NOx, and gas-phase speciated nonmethane hydrocarbons (NMHC) and carbonyl compounds were measured in 1992 in the Fort McHenry Tunnel under Baltimore Harbor and in the Tuscarora Mountain Tunnel of the Pennsylvania Turnpike, for comparison with emission-model predictions and for calculation of the reactivity of vehicle emissions with respect to 03 formation. Both tunnels represent a high-speed setting at relatively steady speed. The cars at both sites tended to be newer than elsewhere (median age was < 4 yr), and much better maintained as judged by low CO/CO2 ratios and other emissions characteristics. The Tuscarora Mountain Tunnel is flat, making it advantageous for testing automotive emission models, while in the underwater Fort McHenry Tunnel the impact of roadway grade can be evaluated. MOBILE4.1 and MOBILE5 gave predictions within + 50% of observation most of the time. Tbere was a tendency to overpredict, especially with MOBILE5 and especially at Tuscarora. However, fight-dutyvehicle CO, NMHC, and NOx all were underpredicted by MOBILE4.1 at Fort McHenry. Light-dutyvehicle CO/NO~ ratios and NMHC/NO~ ratios were generally a little higher than predicted. The comparability of the predictions to the observations contrasts with a 1987 experiment in an urban tunnel (Van Nuys) where CO and HC, as well as CO/NO~ and NMHC/NO~ ratios, were grossly underpredicted. The effect of roadway grade on gram per mile (g mi- 1) emissions was substantial. Fuel-specific emissions (g gal-1), however, were almost independent of roadway grade, which suggests a potential virtue in emissions models based on fuel-specific emissions rather than g mi- 1 emissions. Some 200 NMHC and carbonyl emissions species were quantified as to their light- and heavy-dutyvehicle emission rates. The heavy-duty-vehicle NMHC emissions were calculated to possess more reactivity, per vehicle-mile, with respect to 03 formation (g 03 per vehicle-mile) than did the light-duty-vehicle NMHC emissions. Per gallon of fuel consumed, the light-duty vehicles had the greater reactivity. Much of the NMHC, and much of their reactivity with respect to O3 formation, resided in compounds heavier than Cto, mostly from beavy-duty diesels, implying that atmospheric NMHC sampling with canisters alone is inadequate in at least some situations since canisters were found not to be quantitative beyond ~ C1o. The contrasting lack of compounds heavier than C1o from light-duty vehicles suggests a way to separate light- and heavy-duty-vehicle contributions in receptor modeling source apportionment. The division between light-duty-vehicle tailpipe and nontaiipipe NMHC emissions was ~ 85% tailpipe and ~ 15% nontailpipe (evaporative running losses, etc.). Measured CO/CO2 ratios agreed well with concurrent roadside infrared remote sensing measurements on light-duty vehicles, although remote sensing HC/CO2 ratio measurements were not successful at the low HC levels prevailing. Remote sensing measurements on heavy-duty diesels were obtained for the first time, and were roughly in agreement with the regular (bag sampling) tunnel measurements in both CO/CO2 and HC/CO2 ratios. A number of recommendations for further experiments, measurement methodology development, and emissions model development and evaluation are offered. Copyright

Volatile organic compounds up to C20 emitted from motor vehicles; measurement methods

To understand better the sources of observed differences between on-road vehicle emissions and model estimates, and to evaluate the emission of ozone precursors from motor vehicles, a series of experiments was conducted in the Fort McHenry Tunnel, Baltimore, Maryland (18–24 June 1992), and in the Tuscarora Mountain Tunnel, Pennsylvania (2–8 September 1992). Samples were collected using stainless steel canisters (whole air samples, analyzed for C2C12 hydrocarbons), Tenax-TA solid adsorbent cartridges (for semi-volatile hydrocarbons, in the C8C20 range), and 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridges (for carbonyl compounds). The samples were analyzed using high resolution gas chromatographic separation with Fourier transform infrared/mass spectrometric detection (GC/IRD/ MSD) for qualitative identification and with flame ionization detection (GC/FID) for quantitation of hydrocarbons, and high performance liquid chromatography (HPLC) for identification and quantitation of carbonyl compounds. A custom-designed database management system was used to handle the large data sets generated by these analyses. From the evaluation of canister and Tenax sample stability upon storage, it was found that hydrocarbons in the C8C12 range seemed to be more stable in the Tenax cartridge than in the canister. The effect of the Nafion® dryer (frequently used for moisture removal prior to cryogenic concentration of the canister samples) was also assessed and it was found to lower the measured concentrations of hydrocarbons collected in the canisters. Comparison of hydrocarbon concentrations found in the Tenax and canister samples allows an assessment of the contribution of semi-volatile hydrocarbons (C10C20 range derived from Tenax data) to the total non-methane hydrocarbons (C2C20, derived from canisters and Tenax data). The results of this study show that hydrocarbons in the range of C10C20 are important components of gas-phase hydrocarbons emitted from heavy-duty diesel vehicles (they account for approximately half of the total gas-phase non-methane hydrocarbon emission rates) and hence that solid adsorbent sampling should be used in addition to canister sampling in measurements of motor vehicle emissions.

Variations in Speciated Emissions from Spark-Ignition and Compression-Ignition Motor Vehicles in California's South Coast Air Basin

Abstract The U.S. Department of Energy Gasoline/Diesel PM Split Study examined the sources of uncertainties in using an organic compound-based chemical mass balance receptor model to quantify the contributions of spark-ignition (SI) and compression-ignition (CI) engine exhaust to ambient fine particulate matter (PM2.5). This paper presents the chemical composition profiles of SI and CI engine exhaust from the vehicle-testing portion of the study. Chemical analysis of source samples consisted of gravimetric mass, elements, ions, organic carbon (OC), and elemental carbon (EC) by the Interagency Monitoring of Protected Visual Environments (IMPROVE) and Speciation Trends Network (STN) thermal/optical methods, polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes, alkanes, and polar organic compounds. More than half of the mass of carbonaceous particles emitted by heavy-duty diesel trucks was EC (IMPROVE) and emissions from SI vehicles contained predominantly OC. Although total carbon (TC) by the IMPROVE and STN protocols agreed well for all of the samples, the STN/IMPROVE ratios for EC from SI exhaust decreased with decreasing sample loading. SI vehicles, whether low or high emitters, emitted greater amounts of high-molecular-weight particulate PAHs (benzo[ghi]perylene, indeno[1,2,3-cd]pyrene, and coronene) than did CI vehicles. Diesel emissions contained higher abundances of two- to four-ring semivolatile PAHs. Diacids were emitted by CI vehicles but are also prevalent in secondary organic aerosols, so they cannot be considered unique tracers. Hopanes and steranes were present in lubricating oil with similar composition for both gasoline and diesel vehicles and were negligible in gasoline or diesel fuels. CI vehicles emitted greater total amounts of hopanes and steranes on a mass per mile basis, but abundances were comparable to SI exhaust normalized to TC emissions within measurement uncertainty. The combustion-produced high-molecular-weight PAHs were found in used gasoline motor oil but not in fresh oil and are negligible in used diesel engine oil. The contributions of lubrication oils to abundances of these PAHs in the exhaust were large in some cases and were variable with the age and consumption rate of the oil. These factors contributed to the observed variations in their abundances to total carbon or PM2.5 among the SI composition profiles.

Real-world emissions and calculated reactivities of organic species from motor vehicles

To obtain real-world motor vehicle emission rates for the hydrocarbon ozone precursors, a series of experiments was conducted in the Fort McHenry Tunnel, Baltimore, Maryland and in the Tuscarora Mountain Tunnel, Pennsylvania. Air samples collected in the tunnels were analyzed for approximately 200 non-methane hydrocarbon (NMHC) species up to C20, and formaldehyde. Emission rates were determined from tunnel inlet and outlet fluxes. Traffic composition analysis allowed emissions to be split into light-duty (LD; mostly spark-ignition) and heavy-duty (HD; mostly diesel) contributions. LD emissions of NMHC at Tuscarora were 293 mg/veh-mile, with paraflins constituting 35%, olefins 23%, aromatics 42%, and 6 mg/veh-mile of formaldehyde. At Fort McHenry, LD hydrocarbon emissions were 615 mg/veh-mile, with 38% paraffins, 18% olefins, and 44% aromatics, and 7 mg/veh-mile of formaldehyde. In both tunnels, HD emissions were approximately double LD emissions, but with higher percent paraffins, lower percent olefins, and an order of magnitude more formaldehyde. Through use of reactivity adjustment factors, the reactivity of the NMHC emissions with respect to ozone formation was assessed. Reactivity followed emissions, with HD emissions approximately twice the reactivity of LD emissions (on a per vehicle-mile basis). The mass specific reactivity (g-O3/g-emission) was nearly constant among all vehicles. The effect of grade (assessed at Fort McHenry) was approximately a factor of 2 for both emissions and reactivity. However, since fuel-specific emissions (g-emission/gallon fuel consumed for LD and HD vehicles were nearly independent of grade at Fort McHenry, the fuel-specific ozone reactivity (g-O3/gallon fuel consumed) was also nearly constant over the down- and up-grades.

Emissions from Charbroiling and Grilling of Chicken and Beef

Abstract Emission rates for fine particle (<2.5μ m ) mass (PM2.5 ), carbon (organic/elemental), inorganic ions (SO4 2−, NO3 −, NH4 +), elements (primarily metals), and speciated organic compounds are reported for charbroiling hamburger, steak, and chicken. The PM2.5 rates for charbroiling meats ranged from 4.4 to 11.6 g/kg of uncooked meat in this study. No mass-emission rates are available from grilling, but the speciated organic data are available for these samples. Emission rates varied by type of appliance, meat, meat-fat content, and cooking conditions. High-fat hamburger cooked on an underfired charbroiler emitted the highest amount of PM2.5 . The emissions were almost exclusively composed of organic carbon, with small amounts of elements and inorganic ions. Water-soluble K+ and Cl−, which are used as indicators of wood smoke in source apportionment studies, were also present in meat-cooking emissions. The speciated organic compounds that were measured include polycyclic aromatic hydrocarbons (PAHs), cholesterol, and the long-chain γ-lactones. Charbroiling emissions yielded an average of ~3–5 times more PAHs, ~20 times more cholesterol, and ~10 times more lactones than grilling. These data were utilized in the ambient source apportionment analysis for the 1997 Northern Front Range Air Quality Study source apportionment.

Diurnal and weekday variations in the source contributions of ozone precursors in California's South Coast Air Basin.

Abstract For at least 30 years, ozone (O3) levels on weekends in parts of California’s South Coast (Los Angeles) Air Basin (SoCAB) have been as high as or higher than on weekdays, even though ambient levels of O3 precursors are lower on weekends than on weekdays. A field study was conducted in the Los Angeles area during fall 2000 to test whether proposed relationships between emission sources and ambient nonmethane hydrocarbon (NMHC) and oxides of nitrogen (NOx) levels can account for observed diurnal and day-of-week variations in the concentration and proportions of precursor pollutants that may affect the efficiency and rate of O3 formation. The contributions to ambient NMHC by motor vehicle exhaust and evaporative emissions, estimated using chemical mass balance (CMB) receptor modeling, ranged from 65 to 85% with minimal day-of-week variation. Ratios of ambient NOx associated with black carbon (BC) to NOx associated with carbon monoxide (CO) were approximately 1.25 ± 0.22 during weekdays and 0.76 ± 0.07 and 0.52 ± 0.07 on Saturday and Sunday, respectively. These results demonstrate that lower NOx emissions from diesel exhaust can be a major factor causing lower NOx mixing ratios and higher NMHC/NOx ratios on weekends. Nonmobile sources showed no significant day-of-week variations in their contributions to NMHC. Greater amounts of gasoline emissions are carried over on Friday and Saturday evenings but are, at most, a minor factor contributing to higher NMHC/NOx ratios on weekend mornings.

Exhaust Particle Size Distribution Measurements at the Tuscarora Mountain Tunnel

On-road particle size distributions were measured at the Tuscarora Mountain tunnel on the Pennsylvania Turnpike in May 1999. The data were obtained using a scanning mobility particle sizer. The nucleation modes of the size distributions contained most of the particles on a number concentration basis and exhibited peak diameters ranging from 11 to 17 nm. This observation is consistent with previous calculations and measurements, indicating that significant numbers of ultrafine aerosol particles can be expected in close proximity to busy motorways. The experiment provided 4 case studies for which the tunnel inlet data could be used to correct data obtained at the outlet, allowing for estimates of particle production within the tunnel. Exhaust particle production rates per vehicle kilometer were estimated; the results are presented with the caveat that the measurements were affected by ambient dilution. The 4 case study nucleation mode sizes varied inversely with ambient temperature. The light-duty vehicle contributions to the ultrafine particle distributions were apparently dominated by the heavy-duty vehicle contributions.

Characterization of the volatile organic compounds present in the headspace of decomposing animal remains, and compared with human remains

Human Remains Detection (HRD) dogs can be a useful tool to locate buried human remains because they rely on olfactory rather than visual cues. Trained specifically to locate deceased humans, it is widely believed that HRD dogs can differentiate animal remains from human remains. This study analyzed the volatile organic compounds (VOCs) present in the headspace above partially decomposed animal tissue samples and directly compared them with results published from human tissues using established solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) methods. Volatile organic compounds present in the headspace of four different animal tissue samples (bone, muscle, fat and skin) from each of cow, pig and chicken were identified and compared to published results from human samples. Although there were compounds common to both animal and human remains, the VOC signatures of each of the animal remains differed from those of humans. Of particular interest was the difference between pigs and humans, because in some countries HRD dogs are trained on pig remains rather than human remains. Pig VOC signatures were not found to be a subset of human; in addition to sharing only seven of thirty human-specific compounds, an additional nine unique VOCs were recorded from pig samples which were not present in human samples. The VOC signatures from chicken and human samples were most similar sharing the most compounds of the animals studied. Identifying VOCs that are unique to humans may be useful to develop human-specific training aids for HRD canines, and may eventually lead to an instrument that can detect clandestine human burial sites.

Real-Time Measurements of Jet Aircraft Engine Exhaust

Abstract Particulate-phase exhaust properties from two different types of ground-based jet aircraft engines—high-thrust and turboshaft—were studied with real-time instruments on a portable pallet and additional time-integrated sampling devices. The real-time instruments successfully characterized rapidly changing particulate mass, light absorption, and polycyclic aromatic hydrocarbon (PAH) content. The integrated measurements included particulate-size distributions, PAH, and carbon concentrations for an entire test run (i.e., “run-integrated” measurements). In all cases, the particle-size distributions showed single modes peaking at 20–40nm diameter. Measurements of exhaust from high-thrust F404 engines showed relatively low-light absorption compared with exhaust from a turboshaft engine. Particulate-phase PAH measurements generally varied in phase with both net particulate mass and with light-absorbing particulate concentrations. Unexplained response behavior sometimes occurred with the real-time PAH analyzer, although on average the real-time and integrated PAH methods agreed within the same order of magnitude found in earlier investigations.