Effects of tropical wildfire behavior on fire emissions and subsequent impacts on PM_2.5 and O₃ levels

This study aims to explore the associations between wildfire behavior parameters and various emissions, analyze the impacts of these emissions on environmental PM_2.5 and O₃, and reveal the complex causal relationships between fire behavior and PM_2.5 and O₃ through emissions. The research focuses on three key regions: tropical America, tropical Africa, and tropical Asia. Using multi-output random forest and structural equation modeling, we analyzed the relationships between fire behavior parameters, emissions, and air quality indicators. The results show that: 1) there is a significant spatial correlation between fire behavior parameters and the aforementioned emissions, and this correlation exhibits different patterns in different tropical regions; 2) various pollutants emitted by fires have a significant impact on the formation of PM_2.5 and O₃, among which: in tropical Asia, the role of emissions such as NMVOCs, NO_x, NH₃, CH₄, and SO₂ is particularly prominent. In tropical America and Africa, NH₃, N₂O, and NMVOCs are the main influencing factors. The RF-MTL model demonstrated high predictive performance in these analyses, achieving R² values of up to 0.87 for O₃ in tropical Asia and 0.83 for PM_2.5 in tropical America.; 3) the study not only confirms the role of fire behavior in the synergistic effect between PM_2.5 and O₃ but also reveals the key role of mediating factors such as N₂O, NO_x, and SO₂ in the path of fire behavior affecting pollutants, where Fire Radiative Power (FRP) exerted a total positive effect of 0.366 on PM_2.5 in tropical America and a total negative effect of - 0.594 in tropical Africa. The conclusions of this study provide important insights for understanding the impact of wildfire behavior on air quality and have significant reference value for formulating air quality management and wildfire control policies in different tropical regions.