Characterisation and source Identification of PM10 aerosol samples collected with a high volume cascade impactor in Brisbane

Abstract

PM10 (particulate matter with aerodynamic diameter <10 ¼m) samples of Brisbane air were collected and fractionated into six size fractions (<0.5, 0.50.61, 0.611.3, 1.32.7, 2.74.9 and 4.910 ¼m) with a high volume cascade impactor. The chemical composition of the samples was analysed by techniques including Ion Beam Analysis. On average, 42% of the aerosol mass is in the >2.7-¼m size fraction, with the <0.5-¼m size fraction also contributes 41% of the aerosol mass. The composition of the <1.3-¼m aerosols is significantly different to that of the >1.3-¼m aerosols. The aerosol mass and concentrations of chemical components related to human activities show a bimodal size-distribution pattern, with most of the mass in the accumulation range (<0.65 ¼m). The size geometric mean of aerosol mass is 0.96 ¼m in the samples collected from an industrial/residential site, and is 1.74 ¼m in the samples collected from a suburban site. The size geometric mean of concentrations of chemical components related to human activities ranges from 0.16 to 0.57 ¼m. The concentrations of crustal matter and sea salt show a unimodal size-distribution pattern, and with geometric means of 3.73 and 4.12 ¼m, respectively. Four source factors were resolved by multivariate analysis techniques for the size-fractionated aerosol samples, namely the soil, sea salt, organics and vehicular exhausts factors. The source fingerprints of the factors vary in the size ranges and have implications on the formation and dispersal processes of the particles. On average, the soil and sea salt factors contribute more than 80% of the aerosol mass in the >2.7-¼m fractions, while the organics and vehicular exhausts factors explain almost all the aerosol mass in the <0.61-¼m fractions.