Lead isotope ratios determined by ICP-MS: Monitoring of mining-derived metal particulates in atmospheric fallout, Northern Territory, Australia

Rates of Zn and Pb fallout from atmospheric particulates >10–20 μm in diameter have been measured by passive sampling during development of the McArthur River Zn/Pb mine from 1993 to 1997. Although short-term variability at a given location is high due to a combination of natural factors and limitations imposed by the sampling technique, long-term fallout rates of Pb increased significantly in 1995 following commencement of local mining operations. Recently fallout rates have decreased and are at the lower end of the range found in other Australian mining and inner-city locations. The measurement of Pb isotope ratios by ICP-MS in samples of fallout and soil has provided unequivocal evidence that ore-derived Pb has become the dominant Pb source in fallout up to 8.6 km from the mine. The isotope data has provided sensitive and reliable discrimination between ore-derived Pb and local soil-derived Pb. In areas with several potential sources of fallout, Pb isotope ratios determined by ICP-MS may provide a source-specific and cost-effective monitoring tool.