Heavy metals in waters and sediments of Port Phillip Bay, Australia

Abstract

Despite significant inputs of heavy metals from rivers, creeks and drains and a major sewage treatment plant to Port Phillip Bay, Victoria, Australia, attenuation processes in the water column are such that metal concentrations in the bay waters are comparable to uncontaminated estuaries elsewhere in the world. Sedimentation appeared to be largely responsible for metal removal, with strong correlations between particulate metals and iron in input waters sampled over a storm event. Storm events contributed between 9 (Zn) and 21 (Cr) times the metal loads that enter the bay during low flow conditions. Although metal accumulations in sediments are below guideline concentrations in the major deposition zones, they are highest close to input sources. A unique feature of bay waters was the high concentration of dissolved arsenic (2.8 µg L–1). The source appears to be natural sediment mineralogy, and sediment cores were found to be depleted in arsenic near the sedimentŒwater interface. Overall, the findings suggested that current heavy metal inputs do not represent a threat to the health of the bay.