With concern about fine particulate matter (PM2.5) pollution in urban areas and levels approaching a new Canadian Ambient Air Quality Standards (CAAQS), an exploratory study of air quality characteristics and potential sources affecting PM2.5 levels was undertaken in the City of Calgary, Alberta. The study was performed for the economic recession period 2014 to 2016 using hourly concentrations of criteria air pollutants at two monitoring stations (Calgary central and Calgary northwest). The overall mean and median PM2.5 concentrations were similar at both Calgary central (arithmetic mean: 7.7 mu g/m(3), median: 6.0 mu g/m3) and Calgary northwest (arithmetic mean: 7.5 mu g/m(3), median: 6.0 mu g/m(3)). Three-year averages of annual average daily 24 h PM2.5 concentrations at both stations were below the 2015 annual CAAQS of 10 mu g/m(3) during the study period 2014-2016. A multivariate receptor model positive matrix factorization (PMF) revealed five sources, where secondary aerosol was identified as the largest source of PM2.5 contributing 54% at Calgary central and 42% at Calgary northwest. Other sources included combustion (18%, 39%), traffic (18%, 12%), an O-3-rich source (8%, 4%), and a mixed urban source (2%, 3%) at Calgary central and Calgary northwest, respectively. Variations in annual contributions of secondary aerosol, combustion and traffic were observed at Calgary downtown for 2014-2016. At Calgary northwest no variation was found for annual traffic contributions. These findings offer preliminary information about the contributions of different potential sources to PM2.5 in Calgary; and this information can support policy makers in developing appropriate air quality management initiatives for PM2.5 pollution if needed.
