Heavy‐metal pollution in Manukau and Waitemata Harbours, New Zealand

Abstract

A total of 294 sediment samples from selected locations in Manukau and Waitemata Harbours have been analysed for 9 elements. The data indicate strong to moderate anthropogenic inputs of Pb, Zn, and Cu in certain parts of the harbours, particularly into Mangere Inlet (Manukau Harbour) and off Point Chevalier, Avondale, and the City (Waitemata Harbour). Sediments adjacent to the Manukau Sewage Purification Works appear to be in the uncontaminated to moderately contaminated range for Pb, Zn, and Cu. In general, the surface sediments contain higher concentrations of these metals than the subsurface sediments, although this is not always the case. The level of heavy‐metal pollution in Manukau and Waitemata Harbours appears to be comparable to thatpreviously found in Wellington Harbour if the much higher heavy‐metal levels in the sediments from Waiwhetu Stream and off Pencarrow outfall are discounted. The elevated levels, although undesirable, do not appear to be critical.

Key words:

• heavy metals
• pollution
• Manukau Harbour
• Waitemata Harbour