Trace Metals in sediments from Lake Illawarra, New South Wales, Australia

Sediments in Lake Illawarra have been investigated by deep and shallow coring to provide a comprehensive appraisal of the sediment-bound natural (background) and more recent (i.e., industrial era) trace metal concentrations. The distribution of Cu, Pb and Zn in the upper 20 cm of sediment is directly related to the proportion of mud-dominated sediment forming the central floor of the lake. Trace metal enrichment factors for Cu, Pb and Zn were generally less than 2.5 with the exception of the southern portion of Griffins Bay where the factors were greater than 1.8, 3.5 and 5.8 for Cu, Pb and Zn respectively. According to ANZECC and ARMCANZ (2000) protocols, the sediments can be generally classified as low risk, although the sediments present in the southern part of Griffins Bay can exceed the high guideline value (ISQG-high) of 420 ppm for Zn and the low guideline values (ISQG-low) of 65 ppm and 50 ppm for Cu and Pb respectively. These sediments warrant further investigation in the form of `bioavailability' and biotoxicity testing. Future work could be directed towards an assessment of the acid generation potential of these sediments due to the potential for pyrite oxidation facilitated by dredging and exposure to the atmosphere.