Chemical Signature of Biomass Burning Emitted PM2.5 by Multi-Element Scanning Thermal Analysis

Particulate matter (PM) emitted from biomass burning and wild fire has been an air quality concern in affected areas. It is desirable to have a sensitive and convenient method to detect, characterize and identify sources of biomass burning emitted PM in the air. We initiated this research to identify the chemical signature of biomass burning emitted PM2.5 by a CNS multi-element scanning thermal analysis (MESTA) method and study the feasibility of using it as a fingerprint to trace the presence of biomass burning emitted PM2.5 in the air. We collected PM2.5 samples from the prescribed burnings of the pine forest at the Tall Timbers Experimental Station and from the pre- and post burning ambient air and analyzed them with the MESTA method. MESTA is a method developed for characterizing the thermal stability of organic compounds in a solid sample in terms of C, N and S thermograms from 40 oC to 750 oC. The results of the MESTA show that the prescribed burning emitted PM2.5 has a characteristic thermally stable (300-700 oC) component with very high C/N ratio (150-300) and non-detectable S content. In contrast, the PM2.5 of the pre- and post burning ambient air has a characteristic thermally unstable (100-300 oC) component with very low C/N (1-3) and C/S (3-7) ratios. The results of this study suggest that the MESTA thermograms of the biomass burning emitted PM2.5 could be used as a tracer for the presence of biomass burning PM2.5 in the air.