Particulate emissions from tailpipe during idling of public transit buses fueled with alternative fuels



Engine exhaust in public transit buses has been associated with health effects. This pilot study examines the toxic nature of these engine exhausts under different idling conditions. The emission tests on public buses were performed with two different fuels: the ultra low sulfur diesel (ULSD: Bus 536) and 20% Biodiesel (BD) mixed with ULSD (B20: Bus 506). Particulate matter (PM) was collected from the tailpipe emissions and then analyzed for elements and polycyclic aromatic hydrocarbons (PAH). Cold and hot-idle-engine testing was conducted. The results of the PM emission analysis showed that the PM mean value of emission is dependent on the engine operation conditions and fuel type. The PM emissions in cold idling were lower than the hot idling condition. However, the absence of 16-EPA PAH in the samples suggests that the tested public buses are using clean fuel. It was found that lubricant oil, PM ash content, and storage tanks were the major sources of elemental concentrations in the PM. However, heavy metals are primary reasons in catalyzing the oxidation reactions that results in reduced PM and PAH emissions. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1134–1142, 2013