Taking advantages of online and offline technics to investigate biogenic-SOA during F-BEACh 2014

Poulain a), A. Mutzel a), M. Teich a), N. Triesch a), A. Held b), S. Richter a), D. van Pinxteren a), Y. Iinuma a), M. Brüggemann a),c), T. Hoffmann c), A. Wiedensohler a) and H. Herrmann a)

a)Leibniz-Institut für Troposphärenfroschung (TROPOS), Permoserstr. 15, 04318 Leipzig, Germany

b)University of Bayreuth, Atmospheric Chemistry, Dr.-Hans-Frisch-Str. 1-3, 95448 Bayreuth, Germany

c)Institute of Inorganic and Analytical Chemistry, University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany

Secondary Organic Aerosols (SOAs) are resulting from reactions of Volatile Organic Compounds (VOCs) emitted into the atmosphere either from anthropogenic or biogenic sources. Although SOA represents an important fraction of the total organic aerosols mass, up to now models mostly underestimate the ambient SOA concentrations, indicating that some of the SOA formation mechanisms and/or sources are still not well characterized or missing. One of the dominant SOA sources is related to biogenic emissions from plants and trees. In order to better assess biogenic SOA, an intensive field campaign took place at the forest research station of the University of Bayreuth (Germany) in July 2014 (Fichtelgebirge – Biogenic Emission and Aerosol Chemistry, F-BEACh 2014). A complementary set of real time mass spectrometers, including a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), and an Aerosol Flowing Atmospheric-Pressure Afterglow Mass Spectrometer (AeroFAPA-MS), was deployed. Additionally, off-line analysis on day-night regime on PM1 and PM2.5 filters performed in parallel was made and targeted to Biogenic SOA tracers (e.g., monoterpene tracers, organosulfate, orgnonitrates and nitroxyorganosulfate compounds), carboxylic acids, carbonyls, imidazols.... Source apportionment was performed using Positive Matrix Factorization (PMF) based on the high-resolution AMS mass spectra including both organic and inorganic fragments in order to distinguish inorganic and organic sulfate and nitrate compounds. Validation of the PMF results was made by comparison with off-line results. It was therefore possible to clearly distinguish two groups of factors: one associated to long-range transport/regional background and one related to local SOA sources. From the last group, it was possible to identified in particular a nitrate related OA associated to semi-volatile compounds, an organo-nitrate related factor, a freshly locally formed monoterpene SOA factor, a non-monoterpene SOA factor. Details on the source apportionment results and factors identification will be presented.

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