Multiple Pb sources in marine sediments near the Australian Antarctic Station, Casey

An extensive Pb isotope ratio survey of ∼ 100 marine sediment samples from near Casey Station, East Antarctica has been undertaken. Sediment surface grabs and cores were collected over nine years between 1997-2006 and, following HF total digestion, were analysed by magnetic sector ICP-MS. Fifty-two reference samples ([Pb] range 5-26 mg kg-1) from 6 non-impacted locations displayed a broad range of Pb isotope ratios representative of the natural background geology of the region (208Pb/204Pb ratios of 37.5-40; 206Pb/204Pb ratios of 17-19). Potentially impacted sediments from Brown Bay (n = 27, [Pb] range 18-215 mg kg-1), adjacent to the current and former Australian Stations at Casey (and the associated Thala Valley tip site) showed contamination by Pb characteristic of Broken Hill and Mt Isa Australian deposits (208Pb/204Pb and 206Pb/204Pb values of 35.5-36 and 16.0-16.1, respectively). The nearby abandoned Wilkes Station was previously manned by both US (1957-59) and Australian (1959-69) expeditioners. Adjacent marine sediment samples (n = 24, [Pb] range 13-40 mg kg-1) displayed Pb isotopic signatures suggesting anthropogenic input from multiple sources. On a three-isotope diagram Wilkes sediments were found to display Pb ratios lying intermediate between Missouri (US), Broken Hill/Mt Isa (Australia)/Idaho (US), and natural geogenic Pb end members. Discarded Pb batteries, paint samples and fuel spills were all considered in this work as possible point sources of Pb contamination to the local environment. Batteries are thought to be the dominant source