SOA formation in a photoreactor from a mixture of organic gases and HONO for different experimental conditions

Smog chambers have been extensively used to investigate the chemical routes of oxidation reactions for several organic gases. In this study we present the results of a set of experiments performed in the EUPHORE photoreactor to analyze SOA formation from a mixture of four organic gases related to anthropogenic emissions (1,3,5-trimethylbenzene, o-xylene, octane and toluene) with an oxidant under different experimental conditions. The effect of the organic mixture and oxidant initial concentration and the effect of SO2 on SOA formation were analyzed. A mixture of three organic gases associated to biogenic emissions (isoprene, α-pinene and limonene) was also examined. An on-line analysis of the aerosol concentration and particle size distribution was performed by TEOM and SMPS. Two off-line techniques were also used: ion chromatography to quantify the inorganic fraction (sulfates and nitrates) and derivatization followed by GC–MS to analyse the hydroxyl-containing compounds. The experiment with the mixture of biogenic parent organic gases led to the highest organic aerosol yields and larger particles. High initial SO2 concentrations strongly increased aerosol yields for the anthropogenic mixture.