ASH DISTRIBUTION AND METAL CONTENTS OF LAKE ILLAWARRA BOTTOM SEDIMENTS

The distribution of anthropogenically derived ash and metal contents o f Lake Illawarra bottom sediments have shown that elevated concentrati ons of trace metals, particularly Zn, are linked to ash concentrations . The highest concentrations of total metals (up to 10 times the local ly defined background) were recorded from Griffins Bay, adjacent to th e Port Kembla industrial complex. Other sites investigated exhibited o nly slight trace metal enrichment in near-surface sediments, typically 1.4 to 2 times the background. Analytical data from inductively coupl ed plasma mass spectrometry (ICPMS) indicate that the ratio of EDTA-ex tractable ratio:total metal present in the sediment generally decrease s in the order Pb, Zn and Cu. Lake sedimentation rates, calculated on the basis of metal and ash depth profiles, were found to lie in the ra nge 6.9 to 16 mm year-1 and represent the most serious long-term envir onmental problem in the Illawarra region.