Contaminant pathways in Port Curtis: Final report - OzCoasts

Contaminant pathways in Port Curtis: Final report3: Sediment contaminants3.4 ConclusionsThe study confirmed that intertidal (mangrove) sediments in Port Curtis tend tocollect fine sediments, which contained higher concentrations of metals and PAHsthan estuarine sediments. Using radiochemical dating methods, the top 28 cm ofsubsurface sediments at intertidal/subtidal sites were estimated to have beendeposited since 1958 in Port Curtis, which is roughly the start of theindustrialisation of Gladstone. The rate of sediment deposition was at least0.6 cm/y. Much deeper sediment cores (at least 1–2 m) are necessary todetermine sediment chronology more accurately. The sediment depositional zonesidentified were the northern Narrows, lower Calliope River and South Trees Inlet–Boyne River areas. Stable lead isotope ratios in Port Curtis sediments wereconsistent with those reported for other sediments from northern Queensland.Using three lines of evidence, it was shown that the concentrations of particulatearsenic, chromium and nickel in the benthic sediments of Port Curtis are relatedto the local geology and do not reflect metal contamination by anthropogenicsources. This important factor needs to be taken into account when applyingthe ANZECC/ARMCANZ (2000) sediment quality assessment framework tothis region.PAH contaminants in sediments were highest around the industrial area ofGladstone. Several types of PAHs characteristic of combustion sources weredetected at the middle harbour largely at the Clinton Coal Facility, along CalliopeRiver and at South Trees Inlet/Boyne River. Relatively high proportions of thenaturally-occurring PAH perylene were found in sediments from The Narrowsand Munduran Creek.37