Inside the Fire Plume Chemical Interactions: A Review on Key Processes and Future Directions

Abstract

Fire plumes are rising columns of heated air masses, consisting of gaseous and particulate matter generated by combustion, affecting air quality, climate and public health. The chemical species released undergo secondary reactions and participate in chemical and physical interactions, altering the properties of the fire plume. The ability of the plume to be transported across short and long distances, depending on the atmospheric conditions, reveals the high importance of unraveling the chemical pathways influencing its inner and outer pollutants. Fresh plumes, close to the fire source, typically exhibit high temperatures and rapid reactions. In contrast, aged plumes differ in composition due to shifts in chemical regimes. The presence of sunlight influences oxidative reactions, while its absence favors oxidation paths driven by NO_x chemistry. The complexity of fire plume chemistry presents challenges in efficient characterization of species formation and decomposition. It also directly influences gas-phase species chemical pathways, in-plume evolution and formation of secondary air pollutants, as well as particulate matter composition and fate. This review provides a detailed description of the chemical mechanisms and pathways inside fresh and aged fire plumes and discusses the implications of critical parameters influencing plume composition. Main tracers are identified, and key processes are described, with information reviewed from laboratory, field, and satellite studies. Unaddressed aspects and emerging opportunities are discussed to provide potential future directions of investigation.