See what isn't going down the drain

Dr Manue Martinez with some of the LittaTrap contents audited at NorthTec. Photo / supplied

A multi-agency effort is trapping Northland rubbish before it can find its way into the sea, and shedding new light on plastic, one of the most common ocean pollutants.

The Northland Regional Council is working with NorthTec, Whitebait Connection, the Northland District Health Board, the three district councils and local businesses to install LittaTraps, in a bid to establish how much plastic and other rubbish is reaching the region's rivers and estuaries.

Regional councillor Amy Macdonald said LittaTraps were a simple, cost-effective net that fitted inside a stormwater grate, trapping plastic and other litter that would otherwise be carried to the sea. Fifty traps had been installed around Northland to capture a variety of different land uses, such as playgrounds, carparks, supermarkets, fast food premises and industrial sites.

Dr Manue Martinez, from NorthTec, would audit the traps' contents every three months, and would try to calculate how much plastic was finding its way to the sea.

"The first audit has just been carried out, with a total of 4160 items captured after just three months," Cr Macdonald said.

"The data are also revealing a big difference between sites; one site at a city centre car park in Whangārei had more than 500 items, while two others, a residential street in Dargaville and a commercial office in Whangārei, had just two pieces of litter."

The data had also revealed that cigarette butts, which were made of a plastic called cellulose acetate, were the most common items, with 1322 retrieved from the traps. (Cigarette filters were an environmental issue because they released a "cocktail of chemical nasties" and could take years to break down).

Overall, the dominant variety of litter was plastic (69 per cent), followed by foamed plastic (8 per cent).

Cr Macdonald said plastics were an issue because they biodegraded extremely slowly, and could harm or kill animals that ingested or became entangled in them.

"Discarded plastic items like drink bottles and cigarette butts will break down into smaller and smaller pieces over time. These smaller items are potentially more dangerous to marine animals, and much harder to clean up," she said.

"Plastic rubbish also impacts on the aesthetics and amenity value of our coast."

It was hoped that the study would help identify some high-risk land uses and commonly occurring rubbish for a targeted mitigation and education campaign, along with any seasonal trends, such as more ice cream wrappers in summer.

"Stormwater systems are designed to manage flood risk, and the water is not typically treated, so everything that goes down the drain will end up in the sea," Cr Macdonald added.

Everyone could do their bit by disposing of litter and cigarette butts in a bin and helping to reduce the amount of plastic finding its way to the ocean. Where appropriate, business owners could also consider installing a LittaTrap at their premises.

The Far North's contribution

Three LittaTraps in the Bay of Islands have so far collected 269 items.

The traps were installed in drains at the Kerikeri Domain, Paihia's Williams Rd carpark, and in Hawke Drive, Haruru Falls, in November last year as part of the trial with the Northland Regional Council and NorthTec. In the latest audit, almost 47 per cent of the litter retrieved was plastic, and almost 39 per cent was paper, cardboard, glass or ceramics. The highest plastic content, 81 per cent, was trapped in Paihia.

Fifty traps had been installed around Northland, with the next audit scheduled to begin this month.