[pam-users] Liu et al., AMTD, 2024; Paul et al, under review, 2024

[pam-users]

Liu, Q., Huang, D. D., Lambe, A. T., Lou, S., Zeng, L., Wu, Y., Huang, C., Tao, S., Cheng, X., Chen, Q., Hoi, K. I., Wang, H., Mok, K. M., Huang, C., and Li, Y. J.: A Comprehensive Characterization of Empirical Parameterizations for OH Exposure in the Aerodyne Potential Aerosol Mass Oxidation Flow Reactor (PAM-OFR), EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-2721, 2024.

Abstract. The oxidation flow reactor (OFR) has been widely used to simulate secondary organic aerosol (SOA) formation in laboratory and field studies. The extent of hydroxyl radical (OH) oxidation (or OH exposure, OHexp), normally expressed as the product of OH concentration and residence time in the OFR, is important in assessing the oxidation chemistry in SOA formation. Several models have been developed to quantify the OHexp in OFRs, and empirical equations have been proposed to parameterize OHexp. Practically, the empirical equations and the associated parameters are derived under atmospheric relevant conditions (i.e., external OH reactivity) with limited variations of calibration conditions, such as residence time, water vapor mixing ratio, O3 concentration, etc. Whether the equations or parameters derived under limited sets of calibration conditions can accurately predict the OHexp under dynamically changing experimental conditions with large variations (i.e., extremely high external OH reactivity) in real applications remains uncertain. In this study, we conducted 62 sets of experiments (416 data points) under a wide range of experimental conditions to evaluate the scope of the application of the empirical equations to estimate OHexp. Sensitivity tests were also conducted to obtain a minimum number of data points that is necessary for generating the fitting parameters. We showed that, for the OFR185 mode (185-nm lamps with internal O3 generation), except for external OH reactivity, the parameters obtained within a narrow range of calibration conditions can be extended to estimate the OHexp when the experiments are in wider ranges of conditions. For example, for water vapor mixing ratios, the parameters obtained within a narrow range (0.49-0.99 %) can be extended to estimate the OHexp under the entire range of water vapor mixing ratios (0.49-2.76 %) studied. However, the parameters obtained when the external OH reactivity is below 23 s-1 could not be used to reproduce the OHexp under the entire range of external OH reactivity (4-204 s-1). For the OFR254 mode (254-nm lamps with external O3 generation), all parameters obtained within a narrow range of conditions can be used to estimate OHexp accurately when experimental conditions are extended, but too-low lamp voltages should be avoided. Regardless of OFR185 or OFR254 mode, at least 20-30 data points from SO2 or CO decay with varying conditions are required to fit a set of empirical parameters that can accurately estimate OHexp. Caution should be exercised to use fitted parameters from low external OH reactivity to high ones, for instance, those from direct emissions such as vehicular exhaust and biomass burning.

PAM Wiki - Publications Using the PAM Oxidation Flow Reactor (google.com)<https://sites.google.com/site/pamwiki/publications-using-the-pam-oxidation-flow-reactor?authuser=0>


Andreas Paul, Tuukka Kokkola, Zheng Fang et al. The impact of photochemical aging on secondary aerosol formation from a marine engine, 27 September 2024, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-4983538/v1]

Abstract. Ship traffic is known as one important contributor to air pollution. Recent regulations aimed at reducing sulfur oxide (SOx) pollution by limiting the fuel sulfur content (FSC) may also decrease fresh particulate matter (PM) emitted from ships. However, there is a knowledge gap regarding how the FSC affects secondary aerosol formation. Aerosol particle emissions from a research ship engine operated with either low sulfur heavy fuel oil (LS-HFO) (FSC=0.5%) or marine gas oil (MGO) (FSC=0.01%), were studied. The emissions were photochemically processed in the oxidation flow reactor "PEAR" to equivalent photochemical aging between 0-9 days in the atmosphere. It was found that FSC had no significant impact on secondary organic aerosol (SOA) formation after 3 days of aging, at 1.8±0.4g/kg and 1.5±0.4g/kg for MGO and LS-HFO, respectively. Furthermore, the composition and oxidative pathways remained similar regardless of FSC. However, as a result of the higher secondary SO4 formation and fresh aerosol emissions, LS-HFO had significantly higher total PM1 than MGO. Black carbon (BC) specifically was found to be 3 times higher for HFO than MGO. While the fuel with the lower sulfur content produces significantly less PM, the SOA formation remains similar regardless of FSC.

PAM Wiki - Publications Using Other Oxidation Flow Reactors (google.com)<https://sites.google.com/site/pamwiki/publications-using-other-oxidation-flow-reactors?authuser=0>

Andrew Lambe
Principal Scientist
Aerodyne Research, Inc.

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