Emissions of Particulate Trace Elements, Metals and Organic Species from Gasoline, Diesel, and Biodiesel Passenger Vehicles and Their Relation to Oxidative Potential

Abstract

Three light-duty passenger vehicles were tested in five configurations in a chassis dynamometer study to determine the chemical and oxidative potential of the particulate exhaust emissions. The first vehicle was a diesel Honda with a three-stage oxidation system. Its main catalyst was replaced with a diesel particulate filter (DPF) and tested as a second configuration. The second vehicle was a gasoline-fuelled Toyota Corolla with a three-way catalytic converter. The last vehicle was an older Volkswagen Golf, tested using petro-diesel in its original configuration, and biodiesel with an oxidation catalyst as an alternative configuration. Particulate matter (PM) was collected on filters and subsequently analyzed using various chemical and toxicological assays. The production of reactive oxygen species (ROS), quantified by the dithiothreitol (DTT) and macrophage-ROS assays, was used to measure the PM-induced oxidative potential. The results showed that the Golf vehicle in both configurations had the highest emissions of organic species (PAHs, hopanes, steranes, and organic acids). The DPF-equipped diesel Accord car emitted PM with the lowest amounts of organic species and the lowest oxidative potential. Correlation analyses showed that soluble Fe is strongly associated with particulate ROS activity (R = 0.99), while PAHs and hopanes were highly associated with DTT consumption rates (R = 0.94 and 0.91, respectively). In particular, tracers of lube oil emissions, namely Zn, P, Ca, and hopanes, were strongly correlated with distance-based DTT consumption rates (R = 0.96, 0.92, 0.83, and 0.91, respectively), suggesting that incomplete combustion of lube oil might be important driving factors of the overall PM-induced oxidative stress.