Microscopical TSP studies comparing a city centre and suburban sites in Canberra, Australia

Abstract

A study of total suspended particulate (TSP) levels in Canberra has been carried out using light microscopy, transmission electron microscopy (TEM) and microprobe analysis. A significant source of the fine particulates as well as the greater part of black amorphous particles > 2 μm in city centre samples has been traced by TEM observation to be car emissions. In the suburban site of Kambah TEM displayed charcoal in the black amorphous particles. Further studies using microprobe analysis have shown Pb-Br content in all the fine particulates in the city samples whereas none have been detected in Kambah due to their low concentrations (the presence of small amounts of high electron-dense crystals was visible in TEM observations of Kambah samples). However, high Pb concentrations at both sites correlate well with the fine fraction, indicating that care needs to be taken in interpreting the microprobe results. A strong positive correlation exists between high H/C atomic ratios and the presence of partly burned hydrocarbons containing embedded lead as observed in electron microscopy and microprobe analysis, and between low H/C atomic ratios and the presence of charcoal visible in TEM. For the organic particles from natural sources seasonal peaks of pollen, fungal remains and plant tissue are evident in both localities. Particles of mineral or crustal source form similar peaks in samples from both localities, probably reflecting dry windy conditions. A comparison between TSP results and microscopic results reveals serious problems with using TSP standards as measures of respirable health effects.