Lead isotope ratios determined by ICP-MS: Investigation of anthropogenic lead in seawater and sediment from the Gulf of Carpentaria, Australia

Lead isotope ratios and concentrations have been measured in seawater and marine sediment by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). For seawater, solvent extraction pre-concentration and the use of a micro-concentric nebulizer allowed 1 ml of concentrate to be measured for several minutes to achieve precisions in the range 0.5-1.2% relative standard deviation for 208Pb/206Pb and 207Pb/206Pb. The environmental dispersion of trace amounts of anthropogenic Pb produced distinctive Pb isotope ratio changes in seawater and marine sediments in the immediate vicinity of a Pb---Zn concentrate shipping facility. Concentrate was found to have 208Pb/206Pb ratios in the range 2.21-2.25, whereas environmental background 208Pb/206Pb ratios were: filtered (< 0.45 μm) seawater, 2.13-2.15; unfiltered seawater, 2.06-2.10; sediment, 2.06-2.09. The combined Pb isotope ratio and concentration measurements by ICP-MS have provided a sensitive and cost effective monitoring tool allowing an unambiguous assessment of the source of Pb.