Chamber investigation of the formation and transformation of secondary organic aerosol in mixtures of biogenic and anthropogenic volatile organic compounds

Abstract. A comprehensive chamber investigation of photochemical secondary organic aerosol (SOA) formation and transformation in mixtures anthropogenic (o-cresol) biogenic (α-pinene isoprene) volatile compound (VOC) precursors the presence NOx inorganic seed particles was conducted. To enable direct comparison across systems, initial concentration (hence reactivity) systems towards dominant OH oxidant adjusted. Comparing experiments conducted single-precursor at various reactivity levels (referenced to a nominal base case VOC concentration, e.g. halving for 1/2 experiment) as well their binary ternary mixtures, we show that molecular interactions from mixing can be investigated discuss challenges interpretation. The observed average SOA particle mass yields (the produced consumed) descending order were found following systems: α-pinene (32 ± 7 %), α-pinene–o-cresol (28 9 (21 5 α-pinene–isoprene (16 1 1/3 (15 4 o-cresol (13 3 α-pinene–o-cresol–isoprene (11 o-cresol–isoprene (6 2 isoprene (0 0 %). We find clear suppression yield when it is mixed with isoprene, whilst no or enhancement similarly isoprene. system appeared increased compared calculated based on additivity, measured predicted comparable. However, which more than one precursor contributes unclear whether changes potential are attributable physical chemical interactions, since reference basis complex. Online offline composition volatility, water uptake, “phase” behaviour measurements used interpret introduced detailed elsewhere.