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- Title
Limited Evidence for a Microbial Signal in Ground‐Level Smoke Plumes.
- Authors
Gering, Sarah M.; Sullivan, Amy P.; Kreidenweis, Sonia M.; McMurray, Jill A.; Fierer, Noah
- Abstract
Recent studies have suggested that microbial aerosolization in wildfire smoke is an understudied source of microbes to the atmosphere. Wildfire smoke can travel thousands of kilometers from its source with the potential to facilitate the transport of microbes, including microbes that can have far‐reaching impacts on human or ecosystem health. However, the relevance of longer‐range detection of microbes in smoke plumes remains undetermined, as previous studies have mainly focused on analyses of bioaerosols collected adjacent to or directly above wildfires. Therefore, we investigated whether wildfire smoke estimated to originate >30 km from different wildfire sources would contain detectable levels of bacterial and fungal DNA at ground level, hypothesizing that smoke‐impacted air would harbor greater amounts and a distinct composition of microbes as compared to ambient air. We used cultivation‐independent approaches to analyze 150 filters collected over time from three sampling locations in the western United States, of which 34 filters were determined to capture wildfire smoke events. Contrary to our hypothesis, smoke‐impacted samples harbored lower amounts of microbial DNA. Likewise, there was a limited signal in the composition of the microbial assemblages detected in smoke‐affected samples as compared to ambient air, but we did find that changes in humidity were associated with temporal variation in the composition of the bacterial and fungal bioaerosols. With our study design, we were unable to detect a robust and distinct microbial signal in ground‐level smoke originating from distant wildfires. Plain Language Summary: There have been recent reports that microbes can be released into the atmosphere during wildfires with the expectation that these microbes, including both bacteria and fungi, could possibly be detected in distant smoke plumes. However, we do not yet know if there is a detectable microbial "signal" in the near‐surface atmosphere in smoke beyond the wildfire zone and whether there are broader implications of this mode of microbial dispersal, including possible aerosolization of allergens and pathogens in smoke plumes. We leveraged pre‐existing air sampling efforts to investigate multiple smoke events observed at three sites in the rural western United States. We compared samples collected from ground‐level smoke‐impacted air to "ambient" air (no elevated smoke) using techniques targeting the DNA of bacteria and fungi recovered from the air filters. We expected to find more microbes and distinct types of microbes in air samples that were impacted by wildfire smoke. Instead, our results revealed limited evidence for a smoke‐associated microbial signal in the near‐surface atmosphere. While we cannot definitively claim that microbes are not associated with smoke plumes originating from distant fires, the microbial signal in the sampled ground‐level smoke plumes was below our limits of detection. Key Points: Using aerosol samples collected from the western US, we found that microbial DNA was not elevated in air masses impacted by wildfire smokeWildfire smoke events did not consistently impact the amounts or types of bacteria and fungi in near‐surface aerosol samplesContrary to expectations, we did not detect a microbial signal associated with wildfire smoke in the near‐surface atmosphere
- Subjects
UNITED States; SMOKE plumes; MICROBIOLOGICAL aerosols; AIR filters; WILDFIRE prevention; TOBACCO smoke; RURAL Americans; BACTERIAL DNA; FUNGAL DNA; AIR sampling
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 4, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039416