Contributions of Different Sources to Primary and Secondary PM10 Aerosols in Brisbane, Australia

PM10 aerosol samples (particles with aerodynamic diameter <10 m) were collected during 47 days from an industrial area in Brisbane from April to June 1999. The chemical composition of the samples was analysed by techniques including Ion Beam Analysis. Concurrent data on concentrations of SO2 and NOx at the site were also collected by the State EPA. The chemical mass balance method (CMB) was used to estimate the contribution of different emission sources using source profiles developed from literature composition of particulate emissions from local sources. By assuming the unexplained mass of S, N and organic carbon (OC) as mainly originated from secondary formation, the primary and secondary contributions of these elements were determined. The results of secondary contribution of OC was also compared with those using another method in which primary OC is estimated from the minimum ratio of concentrations of OC to elemental carbon (EC) in the samples. On average, 15% of the total mass, 73% of the S, 93% of the N and 57% of the OC elements in the PM10 samples were from secondary formation. Soil and roadside dust (32%), sea salt (27%), secondary formation (15%), unexplained sources of EC (12%), vehicular exhausts (9%) and biomass burning (9%) were the major sources of the PM10 aerosols. The percentage of secondary OC estimated from the CMB method (57%) is lower than that estimated from the minimum OC/EC ratio method (68%), probably due to the uncertainties in the concentrations of carbonaceous matter and Pb in the source profiles of vehicular exhausts and biomass burning. The relationship between ambient levels of SO2 and NOx and the extent of formation of secondary sulphates and nitrates in the PM10 samples is also investigated in this study.