P.D. Vowles

Characterisation of chemical species in PM2.5 and PM10 aerosols in Brisbane, Australia

Abstract Aerosol samples for PM 10 (particulate matter with aerodynamic diameters less than 10 um) were collected from September 1993 to August 1994 at five sites representing the major land use patterns in Brisbane, a subtropical coastal city in Australia. The samples collected were analysed by techniques such as ion beam analysis and the integrating plate laser absorption method, and the chemical composition of the samples was reconstructed from the observed elemental composition. For these PM 10 samples, the major components, on average, were crustal matter (25% by mass), organics (17%), sea salt (12%), elemental carbon (10%) and ammonium sulphate (7%). Aerosol samples of PM 2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) were collected by a dichotomous sampler at one of the sites (GU), a site on university buildings located in a suburban area of Brisbane but surrounded by a buffer zone provided by a forest conservation area. A high average fine Br/Pb ratio of 0.36 in the GU samples, which is close to that in vehicle exhausts, indicates that this site probably has low background levels of lead even though there has been significant traffic in the area for 20 years, so the forest area is an effective buffer to road dust from the surrounding suburbia. Temporal trends at this site suggest that road side dust and industry-sourced crustal matter could contribute to more than half of the mass of crustal matter. Seasonal meteorological conditions which determine the dispersion of pollutants out of Brisbane and the continuous input of rural dust into Brisbane are potentially important factors influencing the level of crustal matter in Brisbane. However, major rural dust events do not considerably increase the seasonal average level of crustal matter. Also, apart from significant local influences at some sites (such as heavy road traffic network or a cement factory), the results from the GU site show a similar level of elemental and chemical components from anthropogenic sources to sites in heavy industrial and commercial/light industrial sites, indicating that most anthropogenic emissions are evenly and widely distributed in Brisbane.

Source apportionment of PM2.5 and PM10 aerosols in Brisbane (Australia) by receptor modelling

Aerosol samples for PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 and 10 μm, respectively) were collected from 1993 to 1995 at five sites in Brisbane, a subtropical coastal city in Australia. This paper investigates the contributions of emission sources to PM2.5 and PM10 aerosol mass in Brisbane. Source apportionment results derived from the chemical mass balance (CMB), target transformation factor analysis (TTFA) and multiple linear regression (MLR) methods agree well with each other. The contributions from emission sources exhibit large variations in particle size with temporal and spatial differences. On average, the major contributors of PM10 aerosol mass in Brisbane include: soil/road side dusts (25% by mass), motor vehicle exhausts (13%, not including the secondary products), sea salt (12%), Ca-rich and Ti-rich compounds (11%, from cement works and mineral processing industries), biomass burning (7%), and elemental carbon and secondary products contribute to around 15% of the aerosol mass on average. The major sources of PM2.5 aerosols at the Griffith University (GU) site (a suburban site surrounded by forest area) are: elemental carbon (24% by mass), secondary organics (21%), biomass burning (15%) and secondary sulphate (14%). Most of the secondary products are related to motor vehicle exhausts, so, although motor vehicle exhausts contribute directly to only 6% of the PM2.5 aerosol mass, their total contribution (including their secondary products) could be substantial. This pattern of source contribution is similar to the results for Rozelle (Sydney) among the major Australian studies, and is less in contributions from industrial and motor vehicular exhausts than the other cities. An attempt was made to estimate the contribution of rural dust and road side dust. The results show that road side dusts could contribute more than half of the crustal matter. More than 80% of the contribution of vehicle exhausts arises from diesel-fuelled trucks/buses. Biomass burning, large contributions of crustal matter, and/or local contributing sources under calm weather conditions, are often the cause of the high PM10 episodes at the GU site in Brisbane.

Characterisation and source identification of PM10 aerosol samples collected with a high volume cascade impactor in Brisbane (Australia).

PM10 (particulate matter with aerodynamic diameter < 10 microm) samples of Brisbane air were collected and fractionated into six size fractions (< 0.5, 0.5-0.61, 0.61-1.3, 1.3-2.7, 2.7-4.9 and 4.9-10 microm) 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-microm size fraction, with the < 0.5-microm size fraction also contributes 41% of the aerosol mass. The composition of the < 1.3-microm aerosols is significantly different to that of the > 1.3-microm 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 microm). The size geometric mean of aerosol mass is 0.96 microm in the samples collected from an industrial/residential site, and is 1.74 microm 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 microm. The concentrations of crustal matter and sea salt show a unimodal size-distribution pattern, and with geometric means of 3.73 and 4.12 microm, 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-microm fractions, while the organics and vehicular exhausts factors explain almost all the aerosol mass in the < 0.61-microm fractions.

Simultaneous collection of airborne particulate matter on several collection substrates with a high-volume cascade impactor

This paper describes a method for the simultaneous collection of size-fractionated aerosol samples on several collection substrates, including glass-fibre filter, carbon tape and silver tape, with a commercially available high-volume cascade impactor. This permitted various chemical analysis procedures, including ion beam analysis (IBA), instrumental neutron activation analysis (INAA), carbon analysis and scanning electron microscopy (SEM), to be carried out on the samples.

Application of Pixe Analysis to Urban Aerosol Samples Collected on Whatman 41 Filters

Abstract The applicability of the Proton Induced X-Ray Emission (PIXE) technique to multi-elemental analysis of PM10 aerosol samples collected on Whatman 41 cellulose fibrous filters is investigated using concurrent samples collected on teflon membrane filters as references. The elemental levels measured on the two types of filter samples are highly correlated and the ratio of the elemental levels is related to the deepness of penetration of particles inside the filter, which is calculated from the Fan Filter Model. Therefore, PIXE analysis can be used to describe urban aerosol samples collected on low impurity level porous filters such as Whatman 41.