| Abstract
| - Size distributions of particulate hopanes, steranes, andpolycyclic aromatic hydrocarbons (PAHs) were measuredin the exhaust from four heavy-duty diesel vehicles(HDDVs) operated under idle, creep, transient, and two high-speed driving modes. Particulate matter was collectedusing a chassis dynamometer and a dilution sampling systemequipped with cascade impactors and filter samplers.Samples were extracted using organic solvents and analyzedusing gas chromatography−mass spectrometry. Sizedistributions of hopanes and steranes were functions ofengine load conditions and vehicle technology. Hopanes andsteranes peaked in size ranges larger than 0.18 μmaerodynamic particle diameter under light load conditionsand less than 0.10 μm aerodynamic particle diameterunder heavier load conditions. The eight hopane sizedistributions emitted from newer technology (>1998) vehicleswere unimodal while the four hopane size distributionsemitted from older technology vehicles (<1992) were bimodal.Similar trends between older and newer vehicles werenot observed for sterane size distributions. The PAHcomposition emitted from HDDVs was a function of drivingcycle and vehicle technology. Light driving cycles producedquantifiable emissions of 3, 4, 5, and 6 ring PAHs (includingcoronene). Heavier driving cycles produced only the 3 and4 ring PAHs in quantifiable amounts. PM1.8 and PM0.1source profiles constructed using the relative abundanceof hopanes and steranes to total organic carbon werefunctions of vehicle load condition. Increasing load reducedthe relative abundance of motor oil tracers in the PM1.8size fraction and increased the abundance of these tracersin the PM0.1 size fraction. The relative abundances ofPAHs in the PM0.1 and PM1.8 size fractions emitted fromthe oldest vehicle tested (1985 HDDV) were significantlyhigher than for any other vehicle tested.
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