Chemical Analysis of PM2.5 from Controlled Burns of Southwest Biomass Fuels using a High Resolution Time-of-Flight Aerosol Mass Spectrometer

Li Qi(1), SeyedEhsan Hosseini(2), Heejung Jung(2), Bob Yokelson(3), David Weise(4), David Cocker III(1)

(1) Department of Chemical and Environmental Engineering, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside (2) Department of Mechanical Engineering, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside (3) Department of Chemistry, University of Montana, Missoula (4) Foreset Fire Laboratory, 4955 Canyon Crest Drive, Riverside, CA

     Abstract Number: 513
     Last modified: May 13, 2010

Abstract
A total of forty-nine burns were conducted at the Missoula Fire Sciences Lab consisting of nine southwestern fuel types; i.e., chamise scrub oak, ceanothus, maritime chaparral, coastal sage scrub, California sage brush, Manzanita, oak savanna, oak woodland and masticated mesquite. This presentation focuses on the chemical characterization of PM2.5 emissions collected for flaming, mixed and smoldering phases using a HR ToF-AMS. The evolution of OM/OC, H/C, O/C and N/C from fire ignition to extinction was measured to capture the transient and integrated chemical composition of the non-refractory portion of bulk particles. Real time elemental ratios and empirical formulas derived with respect to modified combustion efficiency (MCE) are reported. Real time OM/OC derived from AMS measurement is compared with that obtained from offline filter analysis. For each fuel, the hydrogen fragment ions dominate the unit mass resolution (UMR) mass spectra with no specific fragment ions attributable to an individual ecological combination. An interference ion in the UMR m/z 73, a fragment normally attributed to levoglucosan, is noted. Therefore, the results imply that C2H4O2+ (m/z 60.021) plus C3H5O2+ (m/z 73.029) are more sufficient to estimate the contribution of levoglucosan. The results did not show significant variations of levoglucosan content in the organic particle with the overall average contribution fraction ranging from 0.74% for coastal sage to 1.93% for chamise.