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.

Determinants of ultrafine particle exposures in transportation environments: findings of an 8-month survey conducted in Montréal, Canada

“…In general, however, UFP exposures were greater in the English studies (Kaur et al, 2005b(Kaur et al, , 2006. As in this study, previous investigations have observed higher UFP levels in the morning relative to the evening hours, and this effect may be attributed to lower mixing heights and lower wind speeds during the morning hours (Kuhlbusch et al, 2001) as well as factors such as higher engine temperatures in the evening hours (Fujita et al, 2007). In addition, traffic densities may be higher during the morning hours (Cyrys et al, 2003;Young and Keeler, 2004;Aalto et al, 2005;Kaur et al, 2005aKaur et al, , b, 2006Jeong et al, 2006) as the evening rush hour is generally more spread out relative to the morning commute.…”

Comparison of the MOVES2010a, MOBILE6.2, and EMFAC2007 mobile source emission models with on-road traffic tunnel and remote sensing measurements

“…Another possible explanation may be related to the cycle-average approach used in EMFAC versus the MOVES modal modeling approach. Vehicle emission tests have shown that a large fraction of the PM emissions from normal emitters are associated with hard acceleration events in the vehicle test cycle (Fujita et al, 2007). Measurements during the Kansas City Vehicle Emissions Characterization Study showed that the hard acceleration event that occurs between 840 and 880 sec of the unified driving cycle accounted for about 40% of the total hot running PM emission (Lindhjem et al, 2009) and that this fraction was similar for all model years newer than 1980.…”

“…The TIGF filters and XAD-4 extracts were analyzed separately by GC/MS, using a Varian CP-3800 GC equipped with a CP8400 autosampler and interfaced to a Varian 4000 ion trap for analysis of all semivolatile and condensed-phase organic compounds except hopanes and steranes, as described before (Fujita et al, 2007). Hopanes and steranes were analyzed using the Varian 1200 triple quadrupole gas chromatograph/mass spectrometer (GC/MS/MS) system with CP-8400 autosampler due to the higher sensitivity of this system.…”

Polycyclic Aromatic Hydrocarbons in the Urban Atmosphere of Mexico City

“…The main tracers of this factor are mostly associated to low molecular weight PAHs, namely, ACY, FLU, PHE and FLT, which could be associated mainly with diesel source emissions, since Wang et al, (2007) indicated the dominance of diesel combustion with the presence of three and four ring PAHs (such as FLT and PHE), as well as with oil combustion. Large emissions from diesel could be related also with the high concentrations of CRY which has been suggested as a diesel tracer ( Simcik et al 1999;Fujita et al 2007). The second factor was mostly associated with high molecular weight PAHs accounting 23.66% of the total variance.…”