Microplastics on the Coastlines of Canterbury, New Zealand
We now know microplastics are now found in marine environments around the globe. However, in 2013 we did not know the state of microplastic pollution on the coastlines of New Zealand. This small island nation is tucked away in the South Pacific and has a tourism industry priding itself on it’s “100% pure” brand.
After returning from traveling overseas I returned to University to do postgraduate research in the environmental sciences. The project that I came up with the help of my new supervisor, Dr Sally Gaw, was to examine the concentrations of microplastics on a number of different coastal locations in Canterbury, New Zealand. This was to be the first dedicated microplastics study conducted in New Zealand.
I did have some data to guide my research. In 1978 a chap named Murray Gregory reported the findings of his comprehensive study of 300 beaches in New Zealand. Although the term ‘microplastics’ had not yet been born, he reported the widespread contamination of our coastlines by small plastic nurdles. These are small pellets used as raw material in the production of plastic products. The greatest amounts were unsurprisingly found in the most populated areas of Auckland, Wellington and Christchurch. In some locations the concentrations reached 10,000 nurdles per square meter! The numbers were just staggering.
Christchurch, New Zealand is a medium sized city of approximately 360,000 people. It is surrounded by coastline on its eastern side which has a variety of character. Examples include: beaches exposed to the Pacific Ocean; an estuary fed by urban rivers; beaches located within closed harbors; beaches with sand; beaches with rocks; those close to the city; many that are not. These differences in character make Canterbury a great testing ground to examine microplastic pollution in variety of settings.
To begin this research I first set off and collected sand and sediment from ten different beaches that were representative of these different environments.
The samples collected varied as much as the environment. The beach located north of the city (1) consisted of small stones. The open shore locations (3-6) close to the city were all sand. The estuarine location (7 and 8) were muddy. Samples collected in the harbor (9 and 10) were a mixture of these with large numbers of shells present.
I used a simple salt water separation technique for the short study I was doing. It really is simple science and can be used by anyone to separate plastics from sand samples.
Add sand to salty water > Shake it (vigorously) > Filter the floating particles.
This is now a dated technique but at the time it was a simple and environmentally friendly method to examine the quantities of lightweight plastics in sand. It will effectively float common lightweight plastics including polyethylene, polypropylene and polystyrene. These are the most common plastics that are used in consumer packaging and are frequently found washed up on beaches worldwide. More modern methods can capture denser plastics such as PET (polyethylene terepthlatate) which most plastic bottles are now made of.
I isolated this floating material on filter papers and examined the material under a fluorescence microscope. This technique allowed me to easily identify smaller particles that lit up under the fluorescent excitation (see pics below). A number of microbeads were found in the sand samples. This may be the first instance where these microplastics have been found in beach sand! The bright orange beads really stood out. Not all plastics fluoresce. However, the technique allowed me to identify microplastics that I might have missed with a normal light microscope.
Using this technique, microplastics were found to be present at eight out of the ten locations sampled. The concentrations of microplastics ranged from 0 – 45 particles per kilogram of sand. At the time, this was similar to microplastic concentrations that had been previously reported in Singapore and Belgium which used a similar technique.
I then set out to determine what these plastics were. To do this, I headed to the University of Otago to work with Geoff Smith in the Raman spectroscopy lab. This technique functions by shooting particles of interest with laser light. The material in question gets “excited” and will emit a characteristic signal back to a detector. The microplastic particle can then be identified by comparing this signal, or “molecular fingerprint” against a library of known plastics. The majority of the microplastics were polystyrene, polyethylene and polypropylene. These are all commonly used plastics in packaging.
Composition of microplastics
This short study has shown us that even though we are geographically isolated, we are certainly not free of microplastic pollution in New Zealand. It is likely that much of the pollution is sourced from the city of Christchurch. However, it is also possible that some of this plastic comes from ocean currents that have carried plastic pollution from around the globe.
It really is concerning that microbeads are turning up in the sand of our beaches! Where have they come from? It’s likely that they are from sewage outfall in the area. In the past Christchurch’s sewage was discharged into the estuary on an outgoing tide. However, a new pipeline was constructed to pump the treated wastewater 3 km’s out to sea. Given that these beads float on the water, it seems quite obvious what the likely source is!
The New Zealand government is currently debating whether the use of microbeads should be regulated or banned. Given this new discovery, and the evidence to suggest that they are harmful, I would recommend that the public gets behind such a ban! They are unneccessary and there are plenty of alternatives.
Check out Sustainable Coastlines to see what’s being done to clean up plastic pollution on New Zealand’s coastlines.
See the original media release.