Fibres dominant in microparticle contamination on Auckland beaches
Evidence of plastic microparticles were first found on the New Zealand coastline in the 1970s, and they have been found in many places since. The Scion project ‘Turning the tide on plastic microparticles’ saw a team of researchers sample the waterways and coastlines of the Auckland region to get a snapshot of the plastic microparticle problem in New Zealand’s most populated city.
Results showed that most of the microparticles in Auckland’s waterways are fibres (88 per cent), with small amounts of fragments and films. The sources of two-thirds of fibres were identified as the common plastics polyethylene, polyethylene terephthalate and polypropylene. The remaining third was not plastic but plant-based cellulose or regenerated cellulose like rayon. These findings indicate a major source of microparticle pollution could be the washing of clothing.
These results are aligned with international trends and similar plastic microparticle levels were found in Christchurch waterways and beaches.
With this baseline, New Zealand can start to look at ways to reduce and remove plastic pollution from our environment.
“Establishing a sense of the scale of the issue and evidential data looking at the sources, are crucial first steps if we want to design enduring solutions which will successfully reduce and remove plastic pollution from New Zealand’s environment.” - Sharon Humphreys, Executive Director, Packaging New Zealand
Sampling work for the study began in July 2018 with the collection of sediment samples. Samples were taken at the high-tide mark and intertidal area from 39 sites across Auckland.
The number of microparticles was significantly greater for west coast sites such as Piha compared to those in the east. Higher levels were found in the Manukau Harbour (an average of 1200 particles per square metre) compared with the Waitemata Harbour that had an average of 500 particles per square metre. The plant-based cellulose and regenerated cellulose made up 39% of the findings.
Identification of the microparticle polymer type, showed the majority of plastic microparticles to be polyethylene (19%), polypropylene (5%), polyethylene terephthalate (16%) with others making up the remainder.
Results from this study are a snapshot of the state of the waterways around our most populated city. With its diverse zones including high industry, commercial, residential and parkland next to aquatic environments, Auckland is a good natural laboratory to study the nature and source of plastic microparticle pollution in our aquatic environment.
Worldwide, plastic microparticles (smaller than 5 mm) may pose a threat to aquatic organisms. The smallest particles (c.a. <100 µm) have been found in the tissues of fish and other sea life. As an example, there is a risk that chemicals might migrate out of the particles and cause harm. The risks posed by microplastic particles to marine life and organisms further down the food chain, like humans, still need to be established.
Options to reduce and remove plastic pollution from our environment could include reducing its use, removing major sources of plastic microparticles before they enter the environment, and the introduction of alternative options such as marine degradable plastics.
The research was led by Scion in collaboration with the University of Canterbury, Auckland Council, Watercare, the University of Auckland and Sustainable Coastlines. The Ministry for the Environment’s Waste Minimisation Fund provided funding, as did the Packaging New Zealand.