Spatial and Temporal Variability of Particulate Trace Metals in Port Jackson Estuary, Australia

Major elements (Al, Ca, Fe and Mn) and trace elements (Cu, Cr, Pb, Zn and Ni) in operationally defined available and total particulate phases have been determined along an axial transect of the Port Jackson Estuary during twelve surveys between 1998 and 1999. Salinity, temperature, pH, dissolved oxygen and suspended particulate material (SPM) were also measured. Temporal and spatial variability were tested by two-factor analysis of variance. Throughout the estuary Zn and Ni exhibited a uniform distribution. It is suggested that the low reactivity of these elements may be a result of the water physicochemistry, low SPM concentrations and long residence time in the Port Jackson Estuary. Anthropogenic sources of Zn and Ni are widespread in the Port Jackson catchment, and also contribute to the spatial distribution observed in the estuary. The distributions of particulate Cu and Pb are significantly affected by anthropogenic inputs, particularly, from the southern embayments in the lower estuary. It is suggested that the increase of Cu and Pb seaward is also related to sorption of these elements on Fe-Mn oxides. Mixing, however, can largely account for the distribution of Cr, which was the only element that presented significant decrease in concentration with increasing salinity. Embayments and tributaries of Port Jackson show distinctive signatures of particulate trace metals (Cu, Pb and Cr), as a result of anthropogenic activities around those embayments. The SPM composition has a significant seasonal variability (P<0·05). During spring and summer, the particulate trace metals (Cr, Cu, Pb, Zn and Cr) and major elements (Al and Fe) concentrations are significantly lower than winter. This trend is ascribed to a dilution effect of plankton blooms on SPM composition.