Northland drain trial finds main rubbish items going into the sea

Installing a rubbish-catching LittaTrap at Onerahi last year are Whangārei district councillor Nicholas Connop, Manue Martinez, of NorthTec, Kim Jones, of Whitebait Connection, Northland regional councillor Amy Macdonald, and Shelley Butt, of Sustainable Coastlines.

A trial in Northland has revealed the extent of rubbish that goes into the sea - and cigarette butts are the main item found.

In a bid to determine how much plastic and other litter is reaching Tai Tokerau's rivers and estuaries annually, the Northland Regional Council is working with NorthTec, Whitebait Connection, Northland District Health Board, the region's three district councils and local businesses to install LittaTraps.

The simple, cost-effective nets fit inside a stormwater grate, trapping plastic and other litter that would otherwise be carried by stormwater straight into the sea.

Regional councillor Amy Macdonald said as part of the study, 50 traps have been installed around Northland to capture a variety of land uses, such as playgrounds, car parks, supermarkets, fast-food premises and industrial sites.

Dr Manue Martinez, of NorthTec, will audit the traps' contents every three months and will try to estimate how much plastic is finding its way into the sea.

Manue Martinez with some of the LittaTrap contents audited recently at NorthTec.

The first audit captured a total of 4160 items after just three months. The data is also revealing a big difference between sites: a city-centre car park in Whangārei had more than 500 items, while A residential street in Dargaville and a commercial office in Whangārei had just two pieces of litter.

The data revealed that cigarette butts, which are made of a plastic called cellulose acetate, are the top litter item overall with 1322 butts found. Cigarette filters Release a cocktail of chemical nasties and can take years to break down.

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

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Macdonald said plastics biodegrade extremely slowly and can harm or kill animals that ingest or get 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," he said.

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

Organisers hope the study will help identify high-risk land uses and commonly occurring rubbish so they can target mitigation and education. They're also looking for any seasonal trends, for example there may be more icecream wrappers in summer.

Some of the hundreds of cigarette butts recovered from a network of LittaTraps across Northland. All these butts were collected from just one trap.

"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," Macdonald said.

She says everyone can 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 business.