Possible sources of PM10 in Prince George (Canada) as revealed by morphology and in situ chemical composition of particulate

The susceptibility of the Prince George airshed to incidence of high concentrations of particulate matter <10 μm in aerodynamic diameter (PM10) has raised considerable concern because of potential health hazards. This study examined the utility of chemical and morphological characteristics of PM10 collected and archived by the BC Ministry of Environment, Land and Parks from three monitoring stations to determine the possible sources of PM10 during selected episodic and non-episodic events. Samples from three episodic events (24 h PM10 levels >50 μg m−3) and three non-episodic events (24 h PM10 levels <50 μg m−3) in 1995–1996 were examined using a scanning electron microscope with energy dispersive system. Results show that rounded, spherical and oval shaped particulate were diagnostic for combustion sources, while irregular-shaped particulate were dominant in all samples including road dust. The particulate size distributions indicated that combustion sources contributed more to <2.5 μm fraction while geologic material is responsible for particulate with diameter between 3 and 4 μm. Principal component analysis of in situ chemical composition suggests that high concentrations of aluminum, silicon and magnesium are indicative of geologic material while carbon, sodium and sulphur are indicative of combustion and industrial sources. Our study suggests that in Prince George, episodic events were influenced by geologic material while the non-episodic events are impacted by industrial, combustion and to some extent by geologic materials. We also found that the combined use of particulate morphology and elemental composition has a good potential to distinguish between geologic material and industrial/combustion sources of PM10 in the Prince George airshed.