Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle

摘要

The effect of fuel ethanol content (10, 85 and 100 %) on primaryemissions and on subsequent secondary aerosol formation was investigated fora Euro 5 flex-fuel gasoline vehicle. Emissions were characterized during aNew European Driving Cycle (NEDC) using a comprehensive set-up of high time-resolution instruments. A detailed chemical composition of the exhaust particulatematter (PM) was studied using a soot particle aerosol mass spectrometer(SP-AMS), and secondary aerosol formation was studied using a potential aerosol mass(PAM) chamber. For the primary gaseous compounds, an increase in totalhydrocarbon emissions and a decrease in aromatic BTEX (benzene, toluene,ethylbenzene and xylenes) compounds was observed when the amount of ethanolin the fuel increased. In regard to particles, the largest primary particulatematter concentrations and potential for secondary particle formation wasmeasured for the E10 fuel (10 % ethanol). As the ethanol content of thefuel increased, a significant decrease in the average primary particulate matterconcentrations over the NEDC was found. The PM emissions were 0.45, 0.25and 0.15 mg m for E10, E85 and E100, respectively. Similarly, a cleardecrease in secondary aerosol formation potential was observed with a largercontribution of ethanol in the fuel. The secondary-to-primary PM ratios were 13.4and 1.5 for E10 and E85, respectively. For E100, a slight decrease in PM masswas observed after the PAM chamber, indicating that the PM produced bysecondary aerosol formation was less than the PM lost through wall lossesor the degradation of the primary organic aerosol (POA) in the chamber. For all fuelblends, the formed secondary aerosol consisted mostly of organic compounds.For E10, the contribution of organic compounds containing oxygen increasedfrom 35 %, measured for primary organics, to 62 % after the PAM chamber.For E85, the contribution of organic compounds containing oxygen increasedfrom 42 % (primary) to 57 % (after the PAM chamber), whereas for E100the amount of oxidized organics remained the same (approximately 62 %)with the PAM chamber when compared to the primary emissions.