Composition of Particulate Matter During a Wildfire Smoke Episode in an Urban Area
Open accessAbstract
The composition of wildfire smoke particulate matter (PM) was investigated during a 2018 smoke episode in the San Francisco Bay Area and compared to non-wildfire periods. Scanning electron microscopy (SEM) of passive PM samples deployed at four sites exhibited a higher concentration of submicron, spherical, carbonaceous PM (“tar balls”) during the wildfire period compared to the non-wildfire period. Coarse ash aluminosilicates and potassium bearing particles were enhanced as well. Disproportionately more UV light was absorbed by PM during the wildfire period than during the non-wildfire period, indicating a higher organic content consistent with the observed tar balls. An indoor PM sample from a residence operating a medium-efficiency furnace filter during the smoke episode exhibited fine, carbonaceous PM comparable to outdoors, but reduced coarse ash PM. Indoor/outdoor ratios for PM2.5, PM10-2.5, and PM10 were 0.6, 0.1, and 0.5 respectively. SEM of the wildfire furnace filter revealed a greater proportion of tar balls compared to a non-wildfire filter. Relatively rare particles enriched in Cu, Zn, Sn and Pb were observed in wildfire samples, but not in non-wildfire samples. Higher concentrations of Cu, Zn, and Pb during the wildfire were confirmed by inductively coupled plasma mass spectrometry (ICP-MS) of the furnace filter. The use of low-cost passive samplers enabled rapid deployment at multiple locations and indoors and outdoors during the wildfire episode. These measurements suggest smoke impacts were regional in scale and similar across sites, though local variations in PM2.5 magnitudes, particle types, and confounding by local sources were observed.Copyright © 2021 American Association for Aerosol Research
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Wildfire-emitted particles are typically dominated by a mode smaller than 1 μm of fairly monodisperse carbonaceous tar balls, and a second mode larger than 1 μm of inorganic ash particles.
“Wildfire-emitted particles are somewhat dependent on fuel and burning conditions, but typically dominated by a mode smaller than 1 µm of fairly monodisperse, carbonaceous tar balls, and a second mode larger than 1 µm of inorganic ash particles [28,29,30].”
From Comparative Mask Protection against Inhaling Wildfire Smoke, Allergenic Bioaerosols, and Infectious Particles (2022) · cites this paper as [28]
The Wildfire vs. non-wildfire PM section (page unavailable) reports that submicron particles in these samples were dominated by 150–450 nm carbonaceous tar balls. The Conclusions (page unavailable) say coarse ash particles were enhanced during the wildfire, but do not establish a second, ash-dominated mode above 1 µm. The paper studies an urban smoke episode, so its findings do not establish that this two-mode pattern is typical of wildfire emissions generally. (LLM, conf=0.86)
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References 56 · Cited by 81
Research works printed but not linked: 1
- HEI NPACT Review Panel. 2013. Executive summary. HEI's national particle component toxicity (NPACT) initiative. Boston, MA: Health Effects Institute.
- Authors
- Sparks, T. L., & Wagner, J.
- Affiliations
- California Department of Public Health (US)
- Corresponding author
- Wagner, Jeff
- Venue
- Aerosol Science and Technology
- Publisher
- Informa UK Limited
- Published
- 2021-03-23
- Volume
- 55
- Issue
- 6
- Pages
- 734-747
- ISSN
- 0278-6826 (ISSN-L)
- 1521-7388
- OpenAlex
- W3135309013
- Cited by
- 81
- References
- 56
- Citations by year
- 2026: 18 · 2025: 21 · 2024: 21 · 2023: 12 · 2022: 8 · 2021: 1
- FWCI
- 3.68
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Aerosol Science and Technology (publishedVersion)
- Figshare (submittedVersion, cc-by)
- Figshare (cc-by)
- Funders
- National Aeronautics and Space Administration
- Topics
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Atmospheric chemistry and aerosols
- Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Air Quality and Health Impacts
- Physical Sciences › Environmental Science › Global and Planetary Change › Atmospheric aerosols and clouds
- Keywords
- wildfire smoke, particle composition, tar balls, carbonaceous aerosols, UV absorption, trace metals, San Francisco Bay Area, PM2.5
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