Ozonolysis of α-pinene: parameterization of secondary organic aerosol mass fraction
1Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, USA
2Chemical & Biochemical Engineering and IIHR Hydroscience and Engineering Department, University of Iowa, Iowa City, USA
3Department of Chemical Engineering, University of Patras, Patra, Greece
Abstract. Existing parameterizations tend to underpredict the α-pinene aerosol mass fraction (AMF) by a factor of 2–5 at low organic aerosol concentrations (<5 μg m−3). A wide range of smog chamber results obtained at various conditions (low/high NOx, presence/absence of UV radiation, dry/humid conditions, and temperatures ranging from 15–40°C) collected by various research teams during the last decade are used to derive new parameterizations of the SOA formation from α-pinene ozonolysis. Parameterizations are developed by fitting experimental data to a basis set of saturation concentrations (from 10−2 to 104 μg m−3) using an absorptive equilibrium partitioning model. Separate parameterizations for α-pinene SOA mass fractions are developed for: 1) Low NOx, dark, and dry conditions, 2) Low NOx, UV, and dry conditions, 3) Low NOx, dark, and high RH conditions, 4) High NOx, dark, and dry conditions, 5) High NOx, UV, and dry conditions. According to the proposed parameterizations the α-pinene SOA mass fractions in an atmosphere with 5 μg m−3 of organic aerosol range from 0.032 to 0.1 for reacted α-pinene concentrations in the 1 ppt to 5 ppb range.