AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Properties of Secondary Organic Aerosols Formed in the Oxidation of Alfa-pinene at Different Temperatures
Kasper Kristensene, Louise Normann Jensen, Marianne Glasius, MERETE BILDE, Aarhus University
Abstract Number: 543 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) derived from biogenic volatile organic compounds contribute significantly to the aerosol mass burden of the atmosphere. The chemical composition of SOA is important for the SOA climate impact, and may be highly influenced by temperature. Few studies have however addressed this, and in particular the chemical composition of SOA at temperatures below ambient represents an understudied area. In this work, the formation and properties of secondary organic aerosol formed in the dark ozonolysis or OH initiated oxidation of alfa-pinene was studied in a new chamber facility at Aarhus University. For the dark ozonolysis experiments temperature was varied over the range 258-293 K. The particle elemental composition was probed using an aerosol mass spectrometer (HR-ToF-AMS) and molecular speciation was obtained from off-line (UHPLC/ESI-qTOF-MS) analysis of filter samples. Particle size distributions were measured using a scanning mobility particle sizer (SMPS) system and SOA yields as derived from the integrated size distributions compared with literature studies. In the chemical analysis 16 organic acids and 30 dimer esters were identified. The concentration of the identified organic acids formed in the dark ozonolysis of alfa-pinene was higher (~30% of total SOA mass) at the coldest temperature (258 K) compared to the warmest temperature of 293 K (~20% of total SOA mass) whereas dimer esters were found to be suppressed at low temperatures. Vapour pressures of the identified carboxylic acids and dimer esters have been estimated and the gas/particle distribution of these compounds will be discussed in relation the temperature dependence of their vapour pressures.