From aerodyne-pam-users at lists.aerodyne.com Wed Mar 11 09:35:37 2026 From: aerodyne-pam-users at lists.aerodyne.com (pam-users) Date: Wed, 11 Mar 2026 13:35:37 +0000 Subject: [pam-users] Gibbons et al., Anal. Chem., 2024; Boadu and Ohno, ES&T, 2026 Message-ID: Angel M. Gibbons, Michael Boadu, and Paul E. Ohno, Aerosol Fluorescent Labeling via Probe Molecule Volatilization. Anal. Chem., 96(50), 19947-19954, https://doi.org/10.1021/acs.analchem.4c04291, 2024. Abstract. The physicochemical properties of aerosols, including hygroscopicity, phase state, pH, and viscosity, influence important processes ranging from virus transmission and pulmonary drug delivery to atmospheric light scattering and chemical reactivity. Despite their importance, measurements of these key properties in aerosols remain experimentally challenging due to small particle sizes and low mass densities in air. Fluorescence probe spectroscopy is one of the only analytical techniques that is capable of experimentally determining these properties in situ in a nondestructive and minimally perturbative manner. However, the application of fluorescence probe spectroscopy to important classes of aerosols including exhaled respiratory and ambient atmospheric aerosols has been limited due to a typical reliance on premixing the probe molecule with particle constituents prior to particle generation, which is not always possible. Here, a method for aerosol fluorescent labeling based on probe molecule volatilization is developed. The method is first applied to label model polyethylene glycol (PEG) aerosols with two different polarity-sensitive probes, Nile red and Prodan. The similarity of the relative humidity-dependent fluorescent emission of each probe between prelabeled and volatilized-probe PEG particles validated the methodology. A preliminary application of the technique to indicate the hygroscopicity of artificial saliva respiratory particles and model atmospheric secondary organic aerosol particles is demonstrated. The methodology developed here paves the way for future studies applying powerful fluorescent probe-based analytical techniques to study exhaled or natural aerosols for which fluorescent prelabeling is not possible. Michael Boadu and Paul E. Ohno. In Situ Physicochemical Characterization of Secondary Organic Aerosols via Fluorescence Probe Spectroscopy, Environ. Sci. Technol., 60(9), 7315-7325, https://doi.org/10.1021/acs.est.5c18022, 2026. Abstract. Secondary organic aerosol (SOA) physicochemical properties such as hygroscopicity, degree of oxidation, phase state, pH, and viscosity influence important processes that ultimately impact air quality and climate. Due in part to the experimental challenge of in situ characterization, these physicochemical properties remain incompletely understood. Here, an aerosol fluorescent labeling methodology in conjunction with a fluorescence aerosol flow tube (F-AFT) was used for direct, in situ physicochemical characterization of ?-pinene and toluene SOA. The wavelength of maximum emission ?max of the fluorescent probe Prodan was shown to depend on the hygroscopicity, degree of oxidation, and relative humidity (RH)-dependent phase transitions of the SOA. At varying RH, ?max was linearly correlated with % water content with an R2 value of 0.95. For fixed RH and varying SOA oxidation degree, ?max was linearly correlated with the oxygen-to-carbon ratio (O:C) with an R2 value of 0.95. Finally, the ?max values measured from mixed organic/inorganic particles indicated that ammonium sulfate seeded toluene SOA exhibited liquid-liquid phase separation (LLPS) at 80% RH and below while remaining homogeneous at 90% RH. Overall, this study demonstrates the power and versatility of this approach for direct, online analysis of a range of physicochemical properties in SOA. PAM Wiki - 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: From aerodyne-pam-users at lists.aerodyne.com Wed Mar 11 09:46:42 2026 From: aerodyne-pam-users at lists.aerodyne.com (pam-users) Date: Wed, 11 Mar 2026 13:46:42 +0000 Subject: [pam-users] =?utf-8?q?Choudhary_et_al=2E=2C_AS=26T=2C_2026=3B_Ky?= =?utf-8?b?bMOkbcOka2kgZXQgYWwuLCBBTVQsIDIwMjY=?= Message-ID: 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 Kyl?m?ki, K., J?ppi, M., Simon, L., Honkisz, W., Marjanen, P., Salo, L., Lepist?, T., Lintusaari, H., Barreira, L., Kuutti, H., Rissanen, M., Bielaczyc, P., Timonen, H., Aakko-Saksa, P., and R?nkk?, 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 ?g m-3) than the DOFR (0.36 ?g m-3). PAM Wiki - 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: