Photochemical aging and secondary organic aerosols generated from limonene in an oxidation flow reactor.

Oxidation flow reactors (OFRs) are increasingly used to study the formation and evolution of secondary organic aerosols (SOA) in the atmosphere. The OH/HO2 and OH/O3 ratios in OFRs are similar to tropospheric ratios. In the present work, we investigated the production of SOA generated by OH oxydation and ozonolysis of limonene in OFR as a function of OH exposure and O3 exposure. The results are compared with those obtained from the simulation chambers. The precursor gas is exposed to OH concentrations ranging from 2.11 × 108 to 1.91 × 109 molec cm-3, with an estimated exposure time in the OFR of 137 s. In the environmental chambers, the precursor was oxidized using OH concentrations between 2.10 × 106 and 2.12 × 107 molec cm-3 over exposure times of several hours. In the overlapping OH exposure region, the highest SOA yields are obtained in the OFR, which is explained by the ozonolysis of limonene in the OFR. However, the yields decrease with the increase of OHexp in both systems.