Excitation-Emission Matrix Spectroscopy for Analysis of Chemical Composition of Combustion Generated Particulate Matter

Analysis of particulate matter (PM) is critical for the assessment of human exposures to potentially harmful agents, notably combustion-generated PM; specifically polycyclic aromatic hydrocarbons (PAHs) found in them and associated with carcinogenic and mutagenic effects. In this study, we quantify the presence and concentrations of PAHs with low molecular weight (LMW) and higher molecular weight (HMW) in combustion-generated PM using excitation-emission matrix (EEM) fluorescence spectroscopy. PM samples were generated in a laminar diffusion inverted gravity flame reactor (IGFR) operated on Ethylene and Ethane. Fuel dilution by Ar in 0% to 90% range controls the flame temperature, the maximum flame temperature decreases with fuel dilution. The colder flames result in lower PM yields; however, the PM PAH content increases significantly. Temperature thresholds for PM transition from low to high organic carbon content were characterized based on the maximum flame temperature (1814K-1864K) and highest soot luminosity region temperature (1600K-1650K). Principal component regression (PCR) analysis of the EEM spectra correlates to GCMS data, R² values of 0.98 for LMW and 0.99 for HMW PAHs. The agreement demonstrates that EEM analysis can be used to determine relative concentrations of organic carbon and PAH fractions in combustion PM, and can be related to PM health effects and used in the environmental studies.