posted on 2024-01-24, 21:45authored byLeda N. Kobziar, Phinehas Lampman, Ali Tohidi, Adam K. Kochanski, Antonio Cervantes, Andrew T. Hudak, Ryan McCarley, Brian Gullett, Johanna Aurell, Rachel Moore, David C. Vuono, Brent C. Christner, Adam C. Watts, James Cronan, Roger Ottmar
Wildland fire is a major global driver in the exchange
of aerosols
between terrestrial environments and the atmosphere. This exchange
is commonly quantified using emission factors or the mass of a pollutant
emitted per mass of fuel burned. However, emission factors for microbes
aerosolized by fire have yet to be determined. Using bacterial cell
concentrations collected on unmanned aircraft systems over forest
fires in Utah, USA, we determine bacterial emission factors (BEFs)
for the first time. We estimate that 1.39 × 1010 and
7.68 × 1011 microbes are emitted for each Mg of biomass
consumed in fires burning thinning residues and intact forests, respectively.
These emissions exceed estimates of background bacterial emissions
in other studies by 3–4 orders of magnitude. For the ∼2631
ha of similar forests in the Fishlake National Forest that burn each
year on average, an estimated 1.35 × 1017 cells or
8.1 kg of bacterial biomass were emitted. BEFs were then used to parametrize
a computationally scalable particle transport model that predicted
over 99% of the emitted cells were transported beyond the 17.25 x
17.25 km model domain. BEFs can be used to expand understanding of
global wildfire microbial emissions and their potential consequences
to ecosystems, the atmosphere, and humans.