Effect of coastal cities on surficial sediments mantling an adjacent high-energy continental margin - central New South Wales, Australia

Abstract

Trace metal (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) concentrations in the fine fraction (<62.5 µm) of surficial sediments adjacent to the major urban centres of Sydney, Newcastle and Wollongong on the central New South Wales (NSW) continental margin, Australia, are elevated above regional background. The nature of enrichment off these major urban centres is distinct. The fine fractions of sediments adjacent to Newcastle are enriched in Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn, associated with the disposal of dredged harbour spoil in an offshore dumpsite, whereas adjacent to Sydney, enrichment of Cu, Pb and Zn in the fine fraction of sediments results mainly from the disposal of large volumes of sewage effluent. The source and regional dispersion of trace metals on the central-NSW continental margin can only be established from analysis of the fine fraction of the sediment, because total sediment distributions of contaminants are confounded by a highly variable sediment texture. Generally, low mud contents (<2%) and low concentrations of trace metals in inner-shelf sediment are evidence of efficient dispersal of fine material and associated contaminants on this high-energy continental margin.