Supplementary material to "Secondary organic aerosol formation from α-pinene, alkanes and oil sands related precursors in a new oxidation flow reactor"

Abstract

The design of the ECCC-OFR (Environment and Climate Change Canada oxidation flow reactor) was partially based upon recent OFRs designs (Lambe et al., 2011;Huang et al., 2017;Simonen et al., 2017) with several small specific differences. The specific differences and similarities between the various reported OFRs is described below. Comparison with the PAM (Potential Aerosol Mass) reactor (Lambe et al., 2011): The ECCC-OFR utilizes a conical diffusion inlet, while PAM employs a straight inlet. The straight inlet is likely to lead to some jetting and recirculation, while cone inlet should have improved fluid dynamics (Huang et al., 2017;Mitroo et al., 2018). The lamps of the ECCC-OFR are located on the outside of the reactor, while the lamps for the PAM are located inside the reactor which can increase surface-to-volume ratio and hence wall losses. Finally, both OFRs sample from the center with appropriate side flows as exhaust, however the ECCC-OFR uses a sampling tube which is 12.7 cm offset from the end of the OFR. Comparison with CPOT (Caltech Photooxidation Flow Tube) (Huang et al., 2017): Both of these OFRs use a conical diffusion inlet, with the lamps of both located out of the reactor. The ECCC-OFR samples from a center port, while CPOT samples all gases at the exit cone. The CPOT has a larger surface-tovolume ratio and a longer residence time (~1500 s) compared to the ECCC-OFR, which may lead to larger wall losses of particles and organic vapors. Comparison with TSAR (TUT Secondary Aerosol Reactor) (Simonen et al., 2017): Both of these OFRs make use of a conical inlet, with lamps located on the outside of the reactor. These OFRs both sample from the OFR center-line, with sampling tubes offset from the end of the reactors. The TSAR is designed for rapidly changing sources, with a volume that is smaller (3.3 L) and a residence time which is shorter (37 s) (Simonen et al., 2017). As a result, the OH concentration within the TSAR will be higher at the same OH exposure. The LVOCs inside the reactor can be consumed by high concentration of OH, or exit the OFR because due to insufficient time to condense on aerosols (Simonen et al., 2017).