Risk to port from paints

Nelson has been identified as one of two ports most susceptible to the leaching of copper from antifouling paints on vessels’ hulls in a national survey.

The National Institute of Water and Atmospheric Research’s (Niwa) modelling suggests that in many New Zealand marinas, copper concentrations could be above the guidelines for protection of marine aquatic life.

The two port areas predicted to be at greatest risk are Nelson and the designated port area of Milford Sound in Fiordland, a world heritage area with high ecological value.

This modelling work was conducted for New Zealand’s Environmental Protection Authority (EPA), which assesses the risk of hazardous substances to the environment.

Antifouling paints are used to protect our environment by preventing unwanted organisms attaching themselves to the hulls of boats.

Copper is used in almost all antifouling paints on boats in New Zealand. These paints are designed to leach copper into the water column while vessels are in the water.

Copper leaching from moored vessels represents a potentially significant source of copper in the marine environment. Dissolved copper, the most harmful form to organisms, is measurable in water samples from marinas and ports around New Zealand.

Significant copper inputs also come from stormwater discharges, with high concentrations often measured in harbour sediments.

An existing OECD model, the Marine Antifoulant Model to Predict Environmental Concentrations ( MAM-PEC), was used by Niwa scientists to predict concentrations of antifouling compounds at 11 ports and 13 marinas around New Zealand.

A study to test the predictions for the Auckland area was undertaken by the Auckland Council’s stormwater contaminant scientist, Marcus Cameron, in collaboration with Niwa’s Jennifer Gadd and principal scientist Chris Hickey.

‘‘Based on the results from this study, and information compiled from previous studies, leaching of antifouling paints from vessel hulls appears to be the major source of copper in marina waters,’’ Dr Hickey says.

Mr Cameron says, ‘‘The results were quite surprising – the modelling indicated that copper levels could be quite elevated in marina waters and the sampling broadly confirmed that.

‘‘On top of this the estimates of copper being exported from marinas were also significant,’’ he said.

The EPA is carrying out a reassessment of antifouling paints approved for use in New Zealand.