Mechanistic drivers of PM2.5 emissions and water-soluble organic compounds and spectral characteristics from wildfire combustion.

Wildfire emissions of PM2.5, including its water-soluble organic compounds (WSOC) fraction, pose a significant threat to the global environment and human health. However, the dynamic correlations among the fire environment, fire behavior, as well as the fluorescence components and spectral characteristics of WSOC remain unclear. In this study, a total of 144 indoor simulated combustion experiments and subsequent indoor tests were carried out by setting different fuel loads, fuel moisture contents, and slopes. The results indicated that both the fire environment and fire behavior had a significant impact on the fluorescence components and spectral characteristics of WSOC (P < 0.05). By employing Pearson's correlation coefficient and multiple regression analysis, the correlation intensity of fire environment - fire behavior - WSOC fluorescence components and spectral characteristics was quantified for the first time, thereby uncovering the dynamic coupling relationship among these three elements. After the concentration of PM2.5 changes, the fluorescence components and spectral characteristics of its WSOC exhibit significant differences, which suggests that relying only on PM2.5 concentration to assess health risks may lead to underestimation. It is recommended that fuel management be integrated into the regional health risk assessment system to reduce the impact of wildfire emissions pollution on the ecological environment and public health.