Structure Burning Emissions and Plume Rise Influence PM2.5 Concentrations During the 2025 Los Angeles Fires

Wildland-urban interface (WUI) fires can release substantial emissions from burned structures, yet their air quality impacts remain poorly characterized. We performed multiple high-resolution simulations to incorporate and improve the representation of structure burning emissions for the January 2025 Los Angeles fires in the WRF-Chem model. Applying fire-specific temporal allocation of biomass burning emissions improved agreement of PM 2.5 concentrations with surface observations. Relative to the simulation that only included biomass burning emissions, considering structure burning emissions increased downwind surface and column-integrated PM 2.5 concentrations. Applying plume rise to structural burning emissions shifted more PM 2.5 aloft and substantially reduced their contribution to surface concentrations, while having a smaller effect on column-integrated PM 2.5 . Structure burning increased population-weighted PM 2.5 concentrations in the Los Angeles South Coast area by 14%. Our findings show that representing structure burning emissions and their plume rise is important for modeing air quality and estimating population exposure during WUI fires.