LB 22-191 - The role of wildfire intensity on viability and composition of bioaerosol emissions

With the increasing frequency of wildfires, the health implications for these have come to the limelight as our knowledge about the composition of their emissions expands. Wildfires have been identified as a large source of atmospheric aerosol, which includes both live and dead biological material, known as bioaerosols. Around 20-40% of primary biological aerosol particles (PBAP), composed of bacteria, fungi, viruses, pollen, and plant matter, has been reported to be compositionally unidentified. The viability and number of microbes, along with their composition, can depend on the type of material being burned, the temperature of the fire, atmospheric lifetime residence time, along with other environmental conditions such as humidity and ventilation. With a large fraction of wildfire microbial bioaerosols deriving from burnt plant matter, we investigate whether smoke can act as a vector for viable, aerosolized microbes. To determine the viable fraction of microbial bioaerosols in smoke, we collected the emissions from four different types of plant litters burned in controlled conditions designed to simulate the temperatures seen in two different combustion severities (flaming vs. smoldering). Smoke from these burns was passed through a 6-stage Andersen impactor to evaluate each size fraction separately and captured on cellulose filters to be used in downstream processes such as flow cytometry and fluorescence microscopy, followed by fluorescence activated cell sorting (FACS). These processes allow us to perform 16S and ITS amplicon sequencing to determine the composition of the viable, smoke-carried microbial community. Litter types were specifically chosen to represent New Mexico fuels (Ponderosa pine needles, Blue Grama grass, Gambel Oak leaf, and Juniper tree needle). Preliminary results show that biogenic particles ranging in diameter from 0.65 um to 7 um were observed, with the highest concentration of total particles, as well as potentially viable biogenic particles, found to be between 0.65 um and 1.1 um. Results have also shown that the level of potentially viable biogenic particles varies by both litter type and by combustion severity. The comparison between the experimentally observed microbial bioaerosol and that of background bioaerosols will aid in the modeling and prediction of the impacts of these on the environment and human health.