Infrared Spectroscopy for Detection of Gas-Phase Pyrolysis Products from Prescribed Burns in the Southeastern United States

Wildfires release significant quantities of trace gases and particles; the effluents can significantly impact atmospheric chemistry and climate. Such fires are becoming both more frequent and more severe. Prescribed fires are now routinely used to reduce dangerous fuel buildups in an attempt to prevent or mitigate such wildfire episodes. Identifying and quantifying the gas-phase species associated with such biomass burning has received heightened emphasis due to the released gases' influential role in the atmosphere. Previous prescribed burn studies have focused primarily on the flaming and smoldering stages; less is known, however, about pyrolysis processes and the products that arise during the initial stages of the burning process. The present study differs in that its objective is to exclusively investigate prescribed burn pyrolysis species released prior to the flame front and combustion. To achieve this objective, seven plots were burned in a longleaf pine stand at Ft. Jackson, South Carolina in May 2018, and pyrolysis products were identified using infrared spectroscopy on samples gathered in collection canisters and transported to / analyzed in a nearby laboratory. Preliminary results for several analytes will be presented in terms of their emission ratios for each burn. Preliminary measurements confirm species such as C₂H₄, C₂H_2, HCHO, CH₃OH, HCN, CH₃CHO, furan, furfural, and acrolein, all produced at least in part during the pyrolysis phase. Preliminary data also suggest IR detection of naphthalene and methyl nitrite.