Copper tainting city waterways

The amount of copper in some Auckland waterways is at unhealthy levels, a programme monitoring marine sediment has found.

The Auckland Regional Council-run programme has discovered nine Auckland streams and estuaries with unhealthy levels of copper in its sediments, and a substantial number hovering near the threshold.

ARC stormwater spokesman Earl Shaver said on average, Auckland waterway sediments had copper levels between 20 to 30 parts a million. Marine life begins to be affected at concentrations of 35 parts a million.

Mr Shaver said a trend had emerged from biennial monitoring of waterways over the past eight years.

"Every time we do it, we find the concentrations are going up. That's why we're making it an issue now before it gets to be at a level where we're seeing adverse effects on aquatic organisms.

"We want to try to deal with it before it gets to be a big problem."

Mr Shaver said the problem exclusively affected urban waterways, and under the regional stormwater action plan, copper had been identified as the second highest priority contaminant after zinc.

The metal is around 10 times more toxic than zinc to aquatic life such as shellfish and fish, he said.

Known copper sources are car brake-linings and run-off from building materials such as copper spouting and roofs, marina dry-docks and soil disturbance on historic horticultural sites.
Jenny Webster-Brown, senior lecturer in water quality at Auckland University, said heavy metals such as copper, lead and zinc, which were generated by urban living, would only rise in future.

But two streams with similar copper concentrations could have different toxicities.

"It's not the copper that's bound to the sediment that is, in fact, toxic - it's the copper that's released into the pore water [the water filling the spaces between grains of sediment]."

Worms and other organisms that lived in the sediment would be first affected, followed by other organisms further up the food chain. She said high copper levels were unlikely to affect human health.

Mr Shaver said the council was planning more research to try to determine the biggest contributors of copper to waterways.

ARC environmental management committee chairwoman Dianne Glenn encourages people to use alternative building materials that do not contain copper, or to incorporate roof gardens, filter strips and reduced paved surfaces into their building design. She said it was important to move quickly.

"If we want to protect the Kiwi way of life when it comes to recreating in and enjoying our waterways, and our own health, then we need to start thinking about how our actions are affecting our harbours, streams and estuaries."

Worst-affected waterways

Wairau Creek, North Shore City.
Coxs Bay, Auckland City.
Anns Creek, Auckland City.
Waikaraka Park Cemetery, Auckland City.
Whau River, Waitakere City.
Wairau Creek, Waitakere City.
Henderson Creek, Waitakere City.
Harania Creek, Manukau City.
Tararata Creek, Manukau City.