CSIRO PUBLISHING Research Paper www.publish.csiro.au/journals/env A. Seen et al., Environ. Chem. 2004, 1, 49–54. doi:10.1071/EN04011 Determining the History and Sources of Contaminants in Sediments in the Tamar Estuary,Tasmania, Using 210 Pb Dating and Stable Pb Isotope Analyses Andrew Seen, A,E Ashley Townsend, B Bonnie Atkinson, A Joanna Ellison, C Jennifer Harrison, D and Henk Heijnis D A School of Chemistry, University of Tasmania, Launceston TAS 7250, Australia. B Central Science Laboratory, University of Tasmania, Hobart TAS 7001, Australia. C School of Geography and Environmental Studies, University of Tasmania, Launceston TAS 7250, Australia. D Australian Nuclear Science and Technology Organisation (ANSTO), Menai NSW 2234, Australia. E Corresponding author (e-mail: A.J.Seen@utas.edu.au). Environmental Context. Dating estuary sediments provides insights into the materials entering the estuary and can pinpoint when the contamination occurred. Heavy metal contamination is a known health risk but attributing it to a source can be contentious. For a sample sourced downstream of a city and a mining region, lead-210 dating and stable lead isotope analyses uncovered the sources of lead inputs. These methods quantified the extent that upstream mining activities and, for the first time, the extent that non-mining inputs (vehicles, industry) contributed to the estuary’s pollution. Abstract. 210 Pb dating and heavy metal analyses (Cd, Cu, Pb, Zn) have been combined to establish an historical profile of pollutant levels in sediments in the Tamar Estuary (Tasmania, Australia) over the past century. Heavy metal profiles through the core show a strong correlation with mining activities and industrialization during the past century, reflecting catchment disturbance in one of Australia’s earliest settled areas. A source apportionment of Pb in the sediment core using stable Pb isotope ratios ( 204 Pb, 206 Pb, 207 Pb, 208 Pb) shows that mine pollution has been contributing 10–25 mg kg −1 to Tamar Estuary sediments since the start of mining in the early 1890s, whilst non- mining inputs were not significant until post-1930 and became increasingly significant post-WorldWar II. Since the 1950s–1960s, non-mining anthropogenic Pb inputs have become as significant as Pb from mining activities, although there does appear to be a decline in non-mining inputs during the past 20 years, which is consistent with findings elsewhere where reductions in atmospheric Pb levels have been observed and are attributed to the phasing- out of leaded gasoline. The source apportionment does, however, suggest that Pb from mine pollution at Storys and Aberfoyle Creeks continues to impact upon upperTamar Estuary sediment quality. Keywords. contaminant deposition — geochemistry (inorganic) — lead — source characterization Manuscript received: 22 March 2004. Final version: 30 April 2004. Introduction The Tamar Estuary is formed from the South and North Esk Rivers at the city of Launceston, Tasmania, Australia, and extends 50 km to Bass Strait, Fig. 1. The catchment for the Tamar covers 10 000 km 2 or about 20% of the Tasmanian land mass, with the major land use being agricultural and forestry operations and some past and present mining activities. Urban land use is restricted primarily to Launceston, which was settled in 1805 to become Australia’s third-oldest city and an important early industrial port. The Tamar is a geologically confined estuary prone to silt accumulation, and this offers potential for reconstruction of catchment disturbance. The major mining activities in the Tamar catchment were those undertaken at Storys and Aberfoyle Creeks (tributaries to the South Esk River, 130 km upstream from the city of Launceston) between 1892 and 1982.Two tin and wolfram/ tungsten mines operated at these sites with in excess of 20 000 tonnes of tin and 15 000 tonnes of tungsten triox- ide recovered from these mines over their lifetimes. [1] The quartz–wolframite–cassiterite vein deposits of the Storys Creek and Aberfoyle mines also contained minor amounts of sulfides, including sulfides of iron, cadmium, copper, lead, and zinc. Until 1959 both mines discharged all of their tail- ings and process water directly into Storys and Aberfoyle Creeks, [2] and whilst there was an improvement in environ- mental management post-1959 with, for example, process waters containing finer tailings treated in settling ponds, tailings are still present in Storys and Aberfoyle Creeks. © CSIRO 2004 49 1448-2517/04/010049