[pam-users] Choudhary et al., AS&T, 2026; Kylämäki et al., AMT, 2026

[pam-users]

Vikram Choudhary, Yu Xi, Cynthia Pham, Yuetong Zhang, Kristen I. Hardy, Christopher F. Rider, Julia Zaks, Allan K. Bertram, Arthur Chan, William H. Brune & Chris Carlsten. Characterization and integration of a new oxidative flow reactor for use in biological exposure systems with diesel exhaust and other aerosols. Aerosol Sci. & Technol., 1–21. https://doi.org/10.1080/02786826.2026.2631106, 2026.

Abstract. Freshly emitted air pollutants may not represent real-world exposures in human studies, especially for communities exposed to aged pollutants. This study presents the characterization and simulation of diesel exhaust (DE) atmospheric aging in a new oxidative flow reactor (OFR) named Fast-oxidation Box (FoxBox, volume: 1019 L) and the effect of aging on biological systems through in vitro cellular studies. We examined: (a) residence time distribution (RTD) for DE-derived CO2, SO2, and particles, (b) DE particle transmission efficiency, (c) losses of low-volatile organic compounds (LVOC), and (d) photochemical oxidation of DE (from OH exposure of (1.9 to 9.5)×1011 molec cm−3 s). Our results demonstrate turbulent flow-like conditions in FoxBox with a narrower RTD for particles than gases. The particle transmission efficiency was greater than 80% for mobility diameters from 40 to 615 nm. LVOC losses to FoxBox walls were negligible. The changes in particle size distributions, such as new particle formation, and chemical composition – particularly secondary aerosol formation like nitrate, ammonium, semi-volatile oxygenated organic aerosol (OA) – during photochemical oxidation were like those observed in the atmosphere and other OFRs. The O:C values for newly formed OA in FoxBox were unlike those for ambient low-volatile oxygenated OA, likely due to high PM2.5 loading used for aging. A549 cell exposures revealed increased cytotoxicity and reactive oxygen species formation compared to incubator controls, due to photochemical aging. In the future, we plan to conduct more complex biological research, particularly controlled human studies, which will provide crucial insights and establish a unique capability globally.

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

Kylämäki, K., Jäppi, M., Simon, L., Honkisz, W., Marjanen, P., Salo, L., Lepistö, T., Lintusaari, H., Barreira, L., Kuutti, H., Rissanen, M., Bielaczyc, P., Timonen, H., Aakko-Saksa, P., and Rönkkö, T.: Comparison of two oxidation flow reactors for measuring aged aerosol from passenger car exhaust, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2026-224, 2026.

Abstract. Oxidation flow reactors (OFRs) are a practical way to assess the secondary aerosol (SecA) mass formation potential of any gas mixture of interest in relatively short processing timescales. In this study, two OFRs were assembled in parallel and used to investigate the photochemical aging and formation of secondary aerosol from exhaust emissions of seven passenger cars. The potential aerosol mass OFR (PAM-OFR) and the Dekati OFR (DOFR) have differences in reactor volume, wall material, residence time and ultraviolet (UV) wavelengths, but the particle number and mass size distributions measured after them were comparable when averaged over the transient driving cycle. The average secondary particle mass emission factor (EF) for all 34 cycles was 22.90 mg km-1 for the PAM-OFR and 15.77 mg km-1 for the DOFR. The fuel and exhaust after-treatment technology affected the difference between the PAM-OFR and the DOFR EFs. With gasoline cars, fast bursts of SecA formation during cold start and highway driving were captured more clearly by the DOFR, which led to DOFR EFs exceeding PAM-OFR EFs. However, with modern diesel cars, the CNG car or hybrid cars that all produced low fresh PM emissions, the SecA mass EFs were higher from the PAM-OFR than from the DOFR. OH exposure did not cause the differences in emission factors between the OFRs, because the OH exposure range was small. Background SecA formation from the PAM-OFR was visible in the particle size distributions of the cleanest cars, which was corrected for in the EF calculations. On average, the PAM-OFR produced more background particle mass (9.10 μg m-3) than the DOFR (0.36 μg m-3).

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


Andrew Lambe, PhD, PMP
Principal Scientist
Center for Aerosol and Cloud Chemistry
Aerodyne Research, Inc.
45 Manning Rd., Billerica, MA, 01821
+1-978-663-9500 x 209

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