Fate of Stormwater-derived Metals in Tidal Creeks

Complex interactions occur in tidal creeks with changes in salinity and mixing causing flocculation of sediments and deposition of metals, as well as dissolution of some metals from bottom sediments into the overlying water column. A study in Henderson Creek (Central Waitemata Harbour, Auckland) is investigating processes that occur in tidal creeks to further our understanding of the fate of stormwater-derived contaminants in wider estuarine receiving waters. Hourly water samples were collected over a complete tidal cycle and analysed for dissolved and total metals, sediment and pore water samples were also collected with the ultimate aim of constructing a metal budget for Henderson Creek that accounts for metal fluxes and sources and sinks of particulate and dissolved metals. A further aim is to assess potential effects of metals on estuarine biota. Preliminary results will be presented and discussed in relation to model predictions of stormwater-derived metal accumulation in the Waitemata Harbour.