Chemical Characterization of Particulate Organic Nitrogen Compounds Produced from Prescribed Burns of Managed and Unmanaged Western U.S. Forests
FARRAH HAERI, Daniel Foster, Deep Sengupta, Afsara Tasnia, Paul Van Rooy, Nathan Kreisberg, Lindsay Hatch, Christos Stamatis, Scott Stephens, John Battles, Robert York, Kelley Barsanti, Allen Goldstein, Coty Jen,
Carnegie Mellon University Abstract Number: 212
Working Group: Biomass Combustion: Outdoor/Indoor Transport and Indoor Air Quality
AbstractA significant source of organic nitrogen (ON) compounds in the atmosphere are emitted from biomass burning (BB) events, including wildfires and prescribed burns. ON compounds absorb light, contributing to a warming climate, or deposit onto land and oceans resulting in disruptions of the nitrogen cycle. However, the implications of prescribed burning emissions on air quality or environment are not well characterized, especially regarding the ON contribution from prescribed burning emissions. For this study, we chemically characterize and quantify emission factors (EF) of ON compounds from freshly emitted smoke PM 2.5 particles. Smoke particles were collected via Sequential Spot Sampler during prescribed burns of an unmanaged forest in 2021 and quartz fiber filters from third-entry managed forest plots in 2017 at Blodgett Forest Research Station (BFRS, Georgetown, CA) using a high-performance liquid chromatographers (HPLC) coupled to an orbitrap mass spectrometer. This study differentiates smoke from prescribed burns in managed and unmanaged forest plots based on molecular speciation of hundreds ON compounds as well as quantify the compounds’ respective mass concentrations and EF. We observe that EF of various groups of ON compounds (e.g., CHNO, CHNOS, CHN) are 2-3x higher in unmanaged than managed forests. Results from this non-targeted analysis show that ON emissions in prescribed burning contribute 30-40% by mass of observed speciated smoke emissions, with CHNO and CHNOS compounds dominating that composition. Our observations will help better inform the effects ON compounds from prescribed burns of managed and unmanaged forests have on the atmosphere and climate.