Low-volume sampling and individual particle analysis of airborne particulate matter

Collecting and analyzing airborne particles for identification of relationships between sources and receptors (source apportionment) are important objectives of air monitoring programs. Limitations posed by common bulk analytical techniques from ambient air samples have created an opportunity for examining alternative methods for providing quantitative data for source apportionment. A promising method uses portable low volume sampling (≤5 L/min) followed by Scanning Electron Microscopy - Energy Dispersive X-Ray (SEM-EDX) for individual particle analysis. SEM-EDX has broader identification capabilities than bulk analytical techniques in terms of particle size measurement, morphology characterization, and elemental composition. SEM-EDX is not well suited to analyze filters from fixed Federal Reference Method (FRM) samplers (>10 L/min) because the particles may be too close for individual particle analysis.; This study was performed to identify a method of analyzing individual particle morphology and elemental profiles through Scanning Electron Microscopy - Energy Dispersive X-Ray (SEM-EDX). Ambient airborne particles included those with an aerodynamic diameter of 10 micrometers and less (PM10). One chamber control study and two field collection programs were undertaken.; The chamber control study included comparisons of elemental quantities between SEM-EDX, Inductively Coupled Plasma - Mass Spectroscopy (ICP-MS) using standard reference material NIST 1648 Urban Particulate Matter. Results from the chamber study indicated that analysis of a minimum of 10 randomly selected particles was representative of PM10 collected on a filter at a low volume sampling rate of 5 L/min.; Goals of the ambient field studies were to determine the analytical capability of SEM-EDX compared to ICP-MS, and to characterize regional sources of PM 10 collected by analyzing individual particle morphology and elements. Filter samples were collected for analysis at a low volume sampling rate of 5 L/min. A field study in Edmonton, Alberta demonstrated comparable findings between SEM-EDX and ICP-MS for analysis of major elements (Si, Ca, Fe, Al, Mg, K, Na, Zn, Ti, and Mn). In addition, individual particles---such as fine oil droplets and biological particles (e.g. spores)---not identified through ICP-MS were easily identified through SEM-EDX morphological analysis.; A second field study in a small rural community (High Level, Alberta) was conducted with low volume sampling and SEM-EDX of PM10 in order to undertake receptor modeling using principle component analysis (PCA). PCA apportioned sources of ambient PM10 into three categories: re-suspension of crustal material (32%), re-suspension of salt material used for road de-icing (26%), and combustion (14%), with 28% remaining unknown. These three sources combined accounted for 72% of total variance of the original data set. Maximum mass concentration rose for selected elements agreed with the findings of the PCA for re-suspended salt materials associated with road de-icing and combustion sources.