Metals, arsenic and lead isotopes in near-pristine estuarine and marine coastal sediments from northern Australia

Arsenic and selected metal concentrations, as well as Pb isotope ratios, are reported for sediments from thirteen estuaries and coastal areas along tropical northern Australia. A close approximation of total As, Fe, Mn, Co, Ni, Cu, Zn, Cd and Pb concentrations were derived by a perchloric + nitric acid digestion procedure and the potentially bioavailable fractions were extracted by 1M hydrochloric acid. Total concentrations were at near-pristine levels and although some significant variations were observed amongst the areas studied, concentration ranges are similar to those published for other areas in the region with little anthropogenic input. The potentially bioavailable fraction of each metal (average % ± 1 s.d.) for all areas are: Mn(65 ± 11) > Pb(50 ± 9) > Cd(43 ± 23) > Co(33 ± 5) > Cu (27 ± 5) > As (21 ± 8) > Ni (15 ± 5) ≈ Fe (13 ± 6) ≈ Zn (13 ± 5). The potentially bioavailable fractions for Mn, Co and Ni are similar to published data for globally averaged river particulates. The isotope ratios of naturally derived Pb are catchment specific and of potential value in tracing the provenance of marine coastal and offshore terrigenous sediments. Concordant isotopic ratios for potentially bioavailable Pb and total Pb confirm that there is little anthropogenic Pb in the sediments