10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Daytime and Night-time Atmospheric Aging of Emissions from Combustion Related Sources by Electrospray Ionization Time-of-Flight Mass Spectrometry (EESI-TOF) in a Smog Chamber
AMELIE BERTRAND, Bin Yuan, Giulia Stefenelli, Yandong Tong, Lu Qi, Liwei Wang, Felipe Lopez-Hilfiker, Sepideh Esmaeilirad, Urs Baltensperger, Imad El Haddad, Jay G. Slowik, Andre S.H. Prévôt, Paul Scherrer Institute
Abstract Number: 310 Working Group: Aerosol Chemistry
Abstract Combustion processes are predominant sources of organic aerosol (OA). Several studies have reported their significant contribution to the ambient OA burden. In Europe, biomass burning often accounts for 30 – 50 % of the OA total concentration, while in Asia, coal combustion has been reported to account as up to 30 % of the OA total concentration. The contribution of these sources to the secondary fraction remain however largely uncertain. Due to the complex transformation of the emissions occurring over time in the atmosphere, source apportionment studies can fail to properly distinguish between the different origins of the secondary fraction.
To solve this hurdle, new instruments capable of providing a more extensive knowledge of the chemical composition of the OA at the molecular level and with a high time resolution are necessary. The Paul Scherrer Institute (PSI) has recently developed such an instrument: the extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). The EESI-TOF enables real-time chemical analysis of atmospheric particles without thermal decomposition or ionization-induced fragmentation.
Here, we present results of the coupling of the EESI-TOF to a smog chamber to study the evolution during atmospheric aging of the chemical fingerprint of coal and biomass burning emissions generated with residential appliances. Experiments were conducted in the 7m3 atmospheric chamber (Teflon, 20 °C) of PSI. Emissions were oxidized during 4 - 5 hours under a variety of conditions (NO3 and OH chemistry) to simulate atmospheric aging both during the day and at night. A High Resolution – Time of Flight – Aerosol Mass Spectrometer (HR-TOF-AMS) and an Aethalometer AE33 were installed alongside EESI to provide real-time analysis of the bulk chemical composition of the particulate phase, including the non-refractory material and the black carbon. A Proton Transfer Reaction – Time of Flight – Mass Spectrometer (PTR-TOF-MS) was installed to monitor the volatile organic compounds.
We look into the modification of the chemical fingerprint during aging. With EESI we highlight the differences between fresh and aged, OH, and NO3 chemistry profiles, and compare with what is known of HR-TOF-AMS studies. We show time series of specific ions susceptible to serve as tracers for fresh biomass burning and coal combustion emissions, and secondary fraction. And finally we further investigate the evolution of certain of these compounds in the chamber in lights of what is known regarding their volatility and partitioning.