(503b) Chemical Fingerprinting of Particulate Organic Compounds in Fresh Smoke Produced from Burning Individual Western U.S. Wildland Fuels

Wildfires in the western U.S. are becoming larger and more frequent due to climate change and historical fire suppression. Smoke particles emitted from wildfires are composed of thousands of organic compounds that can vary based upon the fuel burned. The purpose of this study is to identify particulate chemical tracers in order relate smoke composition to a specific fuel or fuel type. Chemical fingerprints were developed from molecular speciation of smoke particles collected during the FIREX campaign at the USDA Fire Sciences Laboratory (Missoula, MT). Western U.S. wildland fuels were burned individually and the emitted smoke particles were collected onto filters. Filters were analyzed using thermal desorption, online derivatization, and 2-dimensional gas chromatography with electron ionization (70 eV) or vacuum ultra-violet light (10.5 eV) high-resolution time-of-flight mass spectrometry. Emission factors of individual organic compounds were normalized to the measured total organic carbon emission factor. Compounds were considered part of the fingerprint for a specific fuel when their ratios exceeded two standard deviations relative to other fuels. These chemical fingerprints were then compared to smoke collected during two western U.S. wildland fires: low-intensity prescribed burning at a managed forest (Blodgett Forest, Georgetown, CA, Nov. 2017) and high-intensity wildfires in northern California (Santa Rosa County, CA, Oct. 2017). Fuels that were identified by their fingerprints, such as manzanita and coniferous rotten log, matched the plant inventory of the forest plots/region. These results indicate that the chemical fingerprints derived from detailed molecular speciation can be used to help determine the specific fuels that burned during wildland fires.