Hydrogeochemical characteristics and importance of natural and anthropogenic influences on soil and groundwater in reclaimed land adjacent to Port Jackson, Sydney, Australia

Abstract

Major ion and trace metal concentrations and physicochemical parameters were measured over a full tidal cycle in groundwater from reclaimed land adjacent to Rozelle Bay in Port Jackson, Sydney, Australia. Materials used for reclaiming the land (construction material waste or dredged marine sediment) predominantly influenced the ion and trace element compositions of the groundwater. The redox behaviour and composition of the soil profiles influenced the behaviour of redox-sensitive elements in the groundwater, for example Mn and Fe. When the water table recedes in drier periods, oxygen ingress can lead to biologically catalysed oxidation reactions resulting in a reduction in pH and an associated increase in the concentration of some trace elements. The dredged marine sediment contains a considerable fraction of shell fragments, leading to elevated bicarbonate levels in the groundwater, which in turn limits some trace element and major ion concentrations. The groundwaters contain higher levels of many trace elements (Cu, Pb, Zn, As, Cr) than occur in seawater and the natural hydraulic gradient may lead to elevated concentrations of these elements entering the estuary.