Hydrogeochemical studies of groundwater from reclaimed land adjacent to Rozelle Bay, Sydney, Australia

Abstract

The current study is undertaken to evaluate the anthropogenic influences of groundwater during tidal cycles in Bicentennial Park adjacent to Rozelle Bay, Sydney, Australia and to explain the geochemical processes controlling trace metal distributions. Results reveal that major ion and trace element compositions of groundwater are predominantly influenced by different types of waste materials (construction materials or dredged marine sediments) disposed in the study area. Major ions in the groundwater exhibit a concentration order of Na≫Mg>Ca>K (equivalents) for areas containing construction waste materials, whereas for areas comprising dredged marine infill sediments it is Na>Ca>Mg>K (equivalents). Similarly, an anionic order of Cl>SO4>HCO3 was observed for areas containing construction materials and HCO3>Cl>SO4 for areas comprising dredged marine infill sediments. The trace metal concentrations indicate that the total dissolved concentrations of As, Cr and Cu relative to chloride collected from the reclaimed land along coastline increase as chloride increases, while the concentrations of Fe and Mn relative to chloride in groundwaters relatively decrease as chloride increases. No trends are apparent for trace, metals such as, Pb, Zn, Ni and Co. There are a number of factors controlling the trace metal concentrations, and hence migration, in the groundwaters associated with landfill materials, which include the redox behaviour of the groundwater, water table fluctuation, fill compositions buried at the site, dilution of seawater by the ingress of freshwater from upgradient of the filled area. Results of this study reveal that the natural hydraulic gradient of the groundwater will lead to elevated concentrations of trace metals (As, Cr, Cu, Pb, Zn) entering the estuary from waste materials used for infill at the site.