(333b) HRTEM & XPS Applied to Particulate Emissions

Characterization of source (particulate) emission profiles is integral to formulation of source profiles towards development of receptor-based models and extraction of source contributions to monitored sites. Exposure and health effects can then be accurately evaluated, atmospheric impacts accurately assessed and regulatory statutes specifically targeted.

Electron microscopic and spectroscopic methods have great potential for carbonaceous aerosol characterization. High-resolution transmission electron microscopy (HRTEM) provides information of the carbon nanostructure (or relative lack thereof). Image quantification allows extraction of various statistical parameters including lamella length, separation distance and tortuosity. These may be summarized in the form of histograms. X-ray photoelectron spectroscopy (XPS) provides a means for probing the surface chemistry of materials. It provides not only information about the atomic composition of a sample but also information about the structure and oxidation state of the constituent elements.

Combustion produced soot is a highly variable material. Physically the nanostructure can range from amorphous to graphitic to fullerenic. Chemically nearly any element could be included, though the surface functional groups are predominantly oxygen-based. Results will be presented for analysis of HRTEM images of the physical nanostructure and XPS analysis of the chemical composition of soots collected from plant, institutional and residential scale oil-fired boilers, diesel engine, gas-turbine combustor (jet engines) and a wildfire. Physically soots from these emission source classes may be differentiated based on carbon lamella length, mean separation and tortuosity. Chemically these soots may also be distinguished by elemental composition, surface (oxygen) functional groups and carbon bonding.

Characterization of source (particulate) emission profiles is integral to formulation of source profiles towards development of receptor-based models and extraction of source contributions to monitored sites. Exposure and health effects can then be accurately evaluated, atmospheric impacts accurately assessed and regulatory statutes specifically targeted.