Secondary organic aerosol formed by EURO 5 gasoline vehicle emissions: chemical composition and gas-to-particle phase partitioning

authors

• Kostenidou Evangelia
• Marques Baptiste
• Temime-Roussel Brice
• Liu Yao
• Vansevenant Boris
• Sartelet Karine
• D’anna Barbara

document type

abstract

In this study we investigated the photo-oxidation of EURO 5 gasoline vehicle emissions during cold urban, hot urban and motorway Artemis cycles. The experiments were conducted in an environmental chamber with average OH concentrations ranging between 6.6x105–2.3x106 molecules cm-3, relative humidity (RH) 40–55 % and temperatures between 22–26 °C. A proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) and the chemical analysis of aerosol on-line (CHARON) inlet coupled with a PTR-ToF-MS were used for the gas and particle phase measurements respectively. This is the first time that CHARON inlet was used for the identification of the secondary organic aerosol (SOA) produced from vehicle emissions. The secondary organic gas phase products ranged between C1 and C9 with 1 to 4 atoms of oxygen and were mainly composed of small oxygenated C1–C3 species. The formed SOA contained compounds from C1 to C14, having 1 to 6 atoms of oxygen and the products’ distribution was centered at C5. Organonitrites and organonitrates contributed 6–7 % of the SOA concentration. Relatively high concentrations of ammonium nitrate (35–160 µg m-3) were formed. The nitrate fraction related to organic nitrate compounds was 0.12–0.20, while ammonium linked to organic ammonium compounds was estimated only during one experiment reaching a fraction of 0.19. The produced SOA exhibited logC* values between 2 and 5. Comparing our results to the theoretical estimations, we observed differences of 1–3 orders of magnitude indicating that additional parameters such as RH, particulate water content, aerosol hygroscopicity, and possible reactions in the particulate phase may affect the gas-to-particle partitioning.

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