[pam-users] Noël et al., ACS E&ST Air, 2025; Simon et al., Atmos. Environ. X, 2025

[pam-users]

Noël, Alexandra, Glenn, Chase K,  El Hajj, Omar, Anosike, Anita, Kumar, Kruthika,  Abdurrahman, Muhammad Isa, Flanagan, Steven, Callaham, Mac A., Loudermilk, E. Louise, Roberts, Elijah T., Choi, Jonathan H., Bai, Bin, Liu, Pengfei, Amster, I. Jonathan, O’Brien, Joseph,  Saleh, Rawad, Differential In Vitro Lung Cell Toxicity of Fresh and Photochemically Aged Smoke Aerosol Emissions from Simulated Wildland Fires of Duff and Surface Fuels,  ACS ES&T Air, https://doi.org/10.1021/acsestair.5c00207, 2025.

Abstract. We investigated the effects of the fuel moisture content and photochemical aging on the toxicity of smoke particulate matter (PM) emissions in simulated wildland fires. We burned fuel beds consisting of surface fuels and duff under moderate and low moisture contents, representative of prescribed fires (Rx) and drought-induced wildfires (Wild), respectively. The Wild emissions were photochemically aged in an oxidation flow reactor (Wild-Aged). We exposed human bronchial epithelial cells to PM extracts from each permutation. PM extracts from all experimental permutations (Rx, Wild, Wild-Aged) induced oxidative stress, evidenced by a significant increase in 8-isoprostane concentration in the cell media compared to control. However, the increase of 8-isoprostane was significantly less in Wild-Aged compared to that in Wild and Rx, indicating loss of oxidative potential due to photochemical aging. Based on the release of lactate dehydrogenase in the cell media, the level of lipid peroxidation, and the magnitude of gene fold-changes, Rx PM extracts were more toxic than Wild. Chemical composition analysis suggests that toxicity was driven by levels of aromatic species in the PM, which were highest in Rx, followed by Wild and Wild-Aged. Overall, these results highlight the complex dependence of the toxicity of wildland-fire smoke on combustion conditions and atmospheric processing.


Leïla Simon, Luis Barreira, Katariina Kylämäki, Sanna Saarikoski, Minna Aurela, Delun Li, Anssi Järvinen, Hannu Kuutti, Wojciech Honkisz, Milja Jäppi, Laura Salo, Matti Rissanen, Tereza Červená, Michal Vojtíšek, Jan Topinka, Piotr Bielaczyc, Topi Rönkkö, Päivi Aakko-Saksa, Hilkka Timonen, From real-driving emissions to urban air quality: composition of aged PM from modern diesel, gasoline, and CNG fueled cars and plug-in hybrid electric vehicles, Atmospheric Environment: X, 28, 100375, https://doi.org/10.1016/j.aeaoa.2025.100375, 2025.

Abstract. Secondary aerosol emissions from vehicle exhaust often surpass primary particle emissions, yet they are not currently regulated, as they remain difficult to constrain. Here we investigate the factors driving the formation and chemical composition of secondary aerosol from light-duty vehicle exhaust emissions, focusing on the most recent Euro emission standard (Euro 6d), and including hybrid and natural gas cars. Seven modern cars were driven through a real-driving emission simulation cycle in a chassis dynamometer. The exhaust emissions were aged in a PAM chamber and their chemical and physical properties measured with an aerosol mass spectrometer and state-of-the-art instrumentation. Results indicate that secondary aerosol emissions surpassed fresh aerosol emissions for all cars, except for old Euro 4 diesel. While on average, Euro 6d gasoline and diesel cars aged PM emissions were about 90 % lower than emissions from older cars, their cold start emissions were still significant. Hybrid cars also emitted considerably when switching to combustion engine, which, depending on the length and style of the driving, could be comparable to non-hybrid vehicles emissions. Aged organic aerosol was dominated by oxidized compounds typical of ambient secondary organic aerosol, with unique compositions across vehicle types and fuels. Notably, the CNG vehicle emitted hydrocarbon-like organics, likely originating from less reactive species from lubricant oil, and the Euro 4 diesel exhibited organic nitrate formation, an underreported component in vehicle exhaust with atmospheric implications. Secondary aerosol and its precursors should be regulated and considered in reduction technologies, to best mitigate atmospheric PM in urban traffic-influenced areas.

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

Andrew Lambe
Principal Scientist
Aerodyne Research, Inc.

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