Articles | Volume 17, issue 8
https://doi.org/10.5194/acp-17-5311-2017
https://doi.org/10.5194/acp-17-5311-2017
Research article
 | 
24 Apr 2017
Research article |  | 24 Apr 2017

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

Hilkka Timonen, Panu Karjalainen, Erkka Saukko, Sanna Saarikoski, Päivi Aakko-Saksa, Pauli Simonen, Timo Murtonen, Miikka Dal Maso, Heino Kuuluvainen, Matthew Bloss, Erik Ahlberg, Birgitta Svenningsson, Joakim Pagels, William H. Brune, Jorma Keskinen, Douglas R. Worsnop, Risto Hillamo, and Topi Rönkkö

Abstract. The effect of fuel ethanol content (10, 85 and 100 %) on primary emissions and on subsequent secondary aerosol formation was investigated for a Euro 5 flex-fuel gasoline vehicle. Emissions were characterized during a New European Driving Cycle (NEDC) using a comprehensive set-up of high time-resolution instruments. A detailed chemical composition of the exhaust particulate matter (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 total hydrocarbon emissions and a decrease in aromatic BTEX (benzene, toluene, ethylbenzene and xylenes) compounds was observed when the amount of ethanol in the fuel increased. In regard to particles, the largest primary particulate matter concentrations and potential for secondary particle formation was measured for the E10 fuel (10 % ethanol). As the ethanol content of the fuel increased, a significant decrease in the average primary particulate matter concentrations over the NEDC was found. The PM emissions were 0.45, 0.25 and 0.15 mg m−3 for E10, E85 and E100, respectively. Similarly, a clear decrease in secondary aerosol formation potential was observed with a larger contribution of ethanol in the fuel. The secondary-to-primary PM ratios were 13.4 and 1.5 for E10 and E85, respectively. For E100, a slight decrease in PM mass was observed after the PAM chamber, indicating that the PM produced by secondary aerosol formation was less than the PM lost through wall losses or the degradation of the primary organic aerosol (POA) in the chamber. For all fuel blends, the formed secondary aerosol consisted mostly of organic compounds. For E10, the contribution of organic compounds containing oxygen increased from 35 %, measured for primary organics, to 62 % after the PAM chamber. For E85, the contribution of organic compounds containing oxygen increased from 42 % (primary) to 57 % (after the PAM chamber), whereas for E100 the amount of oxidized organics remained the same (approximately 62 %) with the PAM chamber when compared to the primary emissions.

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Short summary
The effect of fuel ethanol content (10–100 %) on primary emissions and the subsequent secondary aerosol formation was investigated for a Euro 5 flex-fuel gasoline vehicle. The emissions were characterized during the New European Driving Cycle (NEDC) using high time-resolution instruments. The chemical composition of the exhaust particulate matter was studied using a soot particle aerosol mass spectrometer (SP-AMS), and the secondary aerosol formation was studied with an oxidation chamber.
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