Spatial variability of cadmium, copper, manganese, nickel and zinc in the Port Curtis Estuary, Queensland, Australia

Port Curtis is a rapidly growing industrialised and urbanised harbour in Central Queensland, Australia. The spatial variability of trace metals in waters and suspended particulates was determined along axial transects within the harbour and in oceanic waters adjacent to Port Curtis. Dissolved metal concentrations were significantly elevated in Port Curtis compared with the concentrations measured in the adjacent coastal waters. Dissolved copper and zinc concentrations ranged from <19 to 800 and <31 to 580 ng L–1, respectively, and maxima were observed in inner harbour waters adjacent to the southern entrance to the Narrows and in close proximity to anthropogenic sources. Dissolved nickel concentrations were measured in the range of 110 to 900 ng L–1, and exhibited a maximum concentration in the central to northern Narrows, in an area that was not adjacent to anthropogenic sources. Dissolved manganese concentration maxima were measured in close proximity to the dissolved nickel maxima. It appears likely that the elevated dissolved metal concentrations in Port Curtis and the Narrows were not caused by a single point source, and are the result of several factors, including industrial activity around the foreshore, fluxes from sediment-porewater, low flushing durations, lower water pH and possibly episodic inputs from adjacent rivers.