G. D. McOrist

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.

Arsenic microdistribution and speciation in toenail clippings of children living in a historic gold mining area.

Arsenic is naturally associated with gold mineralisation and elevated in some soils and mine waste around historical gold mining activity in Victoria, Australia. To explore uptake, arsenic concentrations in childrens toenail clippings and household soils were measured, and the microdistribution and speciation of arsenic in situ in toenail clipping thin sections investigated using synchrotron-based X-ray microprobe techniques. The ability to differentiate exogenous arsenic was explored by investigating surface contamination on cleaned clippings using depth profiling, and direct diffusion of arsenic into incubated clippings. Total arsenic concentrations ranged from 0.15 to 2.1 microg/g (n=29) in clipping samples and from 3.3 to 130 microg/g (n=22) in household soils, with significant correlation between transformed arsenic concentrations (Pearsons r=0.42, P=0.023) when household soil was treated as independent. In clipping thin sections (n=2), X-ray fluorescence (XRF) mapping showed discrete layering of arsenic consistent with nail structure, and irregular arsenic incorporation along the nail growth axis. Arsenic concentrations were heterogeneous at 10x10 microm microprobe spot locations investigated (<0.1 to 13.3 microg/g). X-ray absorption near-edge structure (XANES) spectra suggested the presence of two distinct arsenic species: a lower oxidation state species, possibly with mixed sulphur and methyl coordination (denoted As(approximately III)(-S, -CH3)); and a higher oxidation state species (denoted As(approximately V)(-O)). Depth profiling suggested that surface contamination was unlikely (n=4), and XRF and XANES analyses of thin sections of clippings incubated in dry or wet mine waste, or untreated, suggested direct diffusion of arsenic occurred under moist conditions. These findings suggest that arsenic in soil contributes to some systemic absorption associated with periodic exposures among children resident in areas of historic gold mining activity in Victoria, Australia. Future studies are required to ascertain if adverse health effects are associated with current levels of arsenic uptake.

Trace elements in Australian opals using neutron activation analysis

Neutron activation analysis was used to determine the concentration of trace elements in 42 samples of black, grey and white opals taken from a number of recognised Australian field. The results were evaluated to determine if a relationship existed between trace element content and opal colour.

The determination of manganese status in the Australian diet using neutron activation analysis

Fifty representative foods sampled Australia-wide from each of the State capitals were analysed for manganese by instrumental neutron activation analysis. Calculated daily intake of manganese for Australian diets was compared with recommendations by US authorities for the safe and adequate dietary intake of this essential trace element. The contribution of tea to adult daily intakes was determined.

Trace elements in precious and common opals using neutron activation analysis

Neutron activation analysis (NAA) was used to determine the concentration of trace elements in 44 precious and 52 common opals sampled from a number of recognised fields within Australia. The purpose of this study was to determine if precious and common opals of the same colour and location have the same or a different trace element profile. Similar numbers of black, white and grey samples were studied in each case. In most cases common opals had a significantly higher concentrationof certain trace elements when compared with precious opals.

Laboratory studies of the diffusive transport of 137Cs and 60Co through potential waste repository soils.

Tests using reconstituted samples have been performed to assess the diffusive transport of (137)Cs and (60)Co through natural regolith materials from a region in South Australia being considered for a radioactive waste repository. A double diffusion cell apparatus made of polycarbonate resin was developed to estimate the effective diffusion (D(e)) and sorption coefficients (K(d)) that allowed large withdrawals from the source and collector cells and has enabled tests with low concentrations of radioactivity. An alternative to porous stainless steel filter plates has also been used to reduce uncertainty in test interpretation. Analysis of the transient data used a staged method of the Laplace transform to take into consideration the volume of the samples withdrawn from the apparatus during testing. At test completion samples were cut into slices and analysed for radionuclide concentration. Data obtained from the sliced samples confirmed that both numerical and experimental data produced acceptable mass balance. The D(e) values obtained in this study were of the order of 10(-6) cm(2) s(-1) for both species, higher than previously published data. The K(d) values from the diffusion and batch sorption tests were in reasonable agreement for (137)Cs, but an order of magnitude different for (60)Co. The sorption of the latter radionuclide was strongly pH dependent, and this dependency during diffusion tests would benefit from further investigation.

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.

A study using neutron activation analysis of the short-term changes in the selenium content of blood components in human following supplementation with low doses of selenium

A study was undertaken to evaluate the short-term changes in the concentration of selenium in whole blood, plasma and erythrocytes following supplementation with low doses of four different selenium supplements. Fourteen volunteers took one of the supplements each day with breakfast for a period of six weeks. Two blood samples were taken each week during this time and selenium was determined on its components using neutron activation analysis via the77mSe isotope.

Rapid determination of selenium in erythrocytes by neutron activation analysis

The use of ultrafiltration prior to the determination of selenium via the short-lived activation product,77mSe, provided a simple and rapid method for the determination of this element in erythrocytes. An associated reduction in analytical error made this procedure acceptable for monitoring small changes in erythrocyte selenium concentrations.