The Contribution of Forest Fires to PM2.5 Burden in Halifax During the Summer of 2011

Abstract

Source apportionment was used to identify the contributing sources to the concentration of PM2.5 in Halifax over the summer of 2011. The source modeling of choice was Positive Matrix Factorization (PMF) because it does not require source profiles. There were 5 factors that were considered: Biomass burning, shipping emission, surface material, long range transportation and sea salt. The PMF result indicated that biomass burning contributed the most to PM2.5 concentration (56.2%). The second prominent source was shipping emission (20.3%). Surface material contributed 12.2% and long range transport of PM contributed 11.3%. Although Halifax is a port city with very close proximity to the ocean, the salt factor did not contribute to concentration of PM2.5. The PM2.5 showed episodic changes over the sampling period. Combining the episodic change characteristic with the summer sampling time, it is likely that forest fire was the cause of the episodic changes. However, further studies of forest fire inventory, wind direction, and air-mass back track trajectory are needed to confirm that result. Coincidentally, a systematic contamination of nylon filters was identified in this study. The contaminating source, however, was not identified. As a result, it is recommended that nylon filter should be avoided until the contaminating source is identified.