Heavy metal and suspended sediment fluxes from a contaminated, intertidal inlet (Manukau Harbour, New Zealand)

The magnitude of mobilization of Cd, Cu, Fe, Mn, Pb, Zn and suspended particulate matter (SPM) was measured in a 6.5 km2 contaminated inlet on Manukau Harbour, New Zealand, to assess the importance of this process in the recovery of contaminated sediments from pollution and as a source of secondary pollution to the water column. Mobilization of contaminated surface sediments is the main source of contamination to the water column, and the magnitude of mobilization suggests that this process is very important in contaminant cycling in the inlet sediments. During two surveys, the mass fluxes of SPM and metals were greater during the flood than the ebb tide showing that any mobilized contaminants were largely returned to the inlet, consistent with it acting as a sink for sediments and associated metals. Therefore, pollution recovery by the process of mobilization and dispersal will be slow.