Impact of HOMs on Ambient Monoterpene SOA Formation in a German Forest

LAURENT POULAIN, Anke Mutzel, Yoshiteru Iinuma, Stefanie Richters, Dominik van Pinxteren, Martin Brüggemann, Andreas Held, Alfred Wiedensohler, Hartmut Herrmann, Leibniz Institute for Tropospheric Research

     Abstract Number: 136
     Working Group: Carbonaceous Aerosols

Abstract
Secondary Organic Aerosols (SOA) result from the reactions of Volatile Organic Compounds (VOCs) emitted either from anthropogenic or biogenic sources. Although SOA represent an important fraction of the total organic aerosol mass, the models are up to now, mostly underestimating the ambient SOA concentrations. The SOA formation mechanism is a complex system where a large number of reactions and chemical species are involved. The complexity of the SOA formation leads to large uncertainties in its model prediction as well as in its potential climate impact. Over the last few years, the importance of highly oxygenated organic molecules (HOMs) in SOA formation has been demonstrated. However, there are still a lot of uncertainties regarding their contribution to the SOA mass. To better assess this question, an intensive Field campaign took place at the forest research station of the University of Bayreuth (Germany) in July 2014. A complementary set of real-time mass spectrometers including High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), Chemical Ionization Atmospheric-Pressure interface Time-of-Flight Mass Spectrometer (CI-APiToF-MS) were deployed. To fully depict the chemical composition of the particles, offline chemical analysis based on a day-night regime of High-Volume quartz filter samples, was performed focused on Biogenic SOA tracers, as well as particulate HOMs tracers. The different sources of particles including several biogenic SOA factors as well as transport-related factors were identified from source apportionment analysis on combined AMS organic and inorganic mass spectra, supported by the offline analysis results. Combining these results with the gas and particulate HOMs results, allowed us a unique opportunity to investigate the relationship between HOMs and monoterpene SOA as well as new particle formation.