Assessing Wildfire\nImpact on Diffusive Flux of Parent\nand Alkylated PAHs: A Pilot Study of Soil–Air Chemical Movement\nbefore, during, and after Wildfires

The global wildfire risk is predicted to rise due to\ncontributing\nfactors of historical fire management strategies and increases in\nextreme weather conditions. Thus, there is a need to better understand\ncontaminant movement and human exposure to wildfire smoke. Vapor-phase\npolycyclic aromatic hydrocarbons (PAHs) are elevated during wildfires,\nbut little is known about how these chemicals move during and after\nwildfire events for exposure risk assessment. Paired air and soil\npore air passive samplers were deployed before, during, and after\nwildfires to determine diffusive flux of vapor-phase parent (p-PAH)\nand alkylated (a-PAH) PAHs in the Western United States. Naphthalene\nand 2-methylnaphthalene contributed to most of the volatilization\nand deposition (6.3–89%) before and after a wildfire. Retene\n(41%) and phenanthrene (27%) contributed substantially to deposition\nduring a wildfire. During wildfires, the number of PAHs in deposition\nincreased at sites with worse air quality. Most p-PAHs and a-PAHs\nwere either depositing or near equilibrium after a wildfire, except\nfor retene at several locations. A majority (≥50%) of PAHs\nhad a 50% magnitude difference between flux before and after a wildfire.\nThis study increases the understanding of PAH movement and exposure\nduring each stage of the wildfire cycle.