Characterization and source apportionment of particulate matter less than 10 microns in diameter in the Prince George airshed

Abstract

The susceptibility of the Prince George airshed to high concentrations of particulate matter less than 10 microns in diameter (PM10) have raised considerable concern because of the possible health impacts attributed to this air pollutant. This study examined the chemical and morphological characteristics of samples collected from two main PM10 sources and selected ambient samples from the archive of the Ministry of Environment to determine the contributions from these PM10 sources to the PM10 composition during Episodic and Non-Episodic events. The sources sampled included road dust taken from street sweepings, snow removed from city streets and unpaved roads and a beehive burner sample. PM10 samples from three Episodic events with 24 hour PM10 levels >50!-!g/m 3 and threeNon-Episodic events with 24 hour PM10 levels <50!-!g/m 3 were examined in the bowl area ofPrince George (represented by three sampling sites: Plaza, Van Bien, and Lakewood) using a ScanningElectron microscope with Energy Dispersive system and Inductively Coupled Plasma EmissionSpectroscopy. Episodes and Non-Episodes were also examined in the BCR industrial site.Results show that rounded, spherical and oval shaped particles were diagnostic of combustion sources, while amorphous shaped particles were dominant in all samples. The particle size distributions indicated that combustion sources contributed more to the fine fraction ofPM10 (<2.5!-!m) than road dust. The presence of a substantial amount ofPM10 with a diameter of3-4!lm is diagnostic for significant contributions of the road dust source to ambient PM10. The qualitative chemical analysis suggested that high concentrations of aluminum, silicon and magnesium were indicative of road dust while high concentrations of carbon, sodium and sulphur were indicative of combustion and industrial sources.Principal Component Analysis (PCA) was performed on the qualitative chemical data and four discernable sources were identified as contributing to the ambient PM10 in all locations: road dust, ii industrial, combustion, and salt. Most of the episodes examined were dominated by road dust while the non-episodes were influenced by industrial, combustion and road dust.