Up close and personal with Microplastics
BY HANNAH DE FROND
Microplastics are everywhere. Every sample I have analysed, from sediments to fish tissue, has contained tens if not hundreds of plastic particles of different shapes and sizes.
I work as a plastic pollution researcher at the University of Toronto, where a large part of my work involves testing and developing methods to analyse microplastics from environmental samples. Microplastics (plastic particles <5 mm in size) have now been found in every ecosystem from the deep ocean to arctic sea ice, and even in the air we breathe. Since the term was first coined in 2004, there have been constant developments in what we know about microplastics; their presence and fate in the environment, and their impacts on wildlife and human health.
Searching for microplastics!
The main steps of processing a microplastics sample include; extraction, counting and characterisation, and chemical identification. Extraction is the first step, where we separate the microplastics from organic material in a sample such as water, animal tissue, or sediment. There are different methods for this depending on the sample type. For clean water samples, we can separate out the microplastics by pouring the sample through a sieve. For animal tissue, chemicals are used to digest the tissue and leave the microplastics behind.
After extraction, the particles are identified under a microscope. We count how many microplastics we find, and note down their colour and shape (fragment, fiber, foam etc.). Microplastics can range from large pieces, to tiny particles less than 100 microns in size - about the width of a human hair. Often it can take a number of days to count all the particles in a single sample!
This is what a typical sample will look like after we have identified and picked out the microplastics. Each particle is circled and numbered to help with data recording.
Following microscopy, we identify particles by their polymer type. Polymer types include polystyrene which is used to make items like styrofoam takeout boxes and packaging or polypropylene which is used to make things like straws, grocery bags and cling film. To do this, we use a method called spectroscopy. In short, spectroscopy uses a laser to shine light on a particle and the amount of energy that is absorbed and emitted back is measured can be used to identify the chemical components. Once we have collected all of this information, we can analyse the data and write up our results!
A Raman Spectrometer, one of the methods we use to identify microplastics by polymer type.
I never imagined myself working in a lab, but I really do enjoy it. Every day is different, and I am constantly learning new techniques. It is also such a rewarding feeling to discover something new or to test a method and see it work successfully. Although it is sad to see so much plastic in every sample, it keeps me motivated knowing that the work I do can improve methods for others, which in turn might lead to an exciting new discovery about microplastics. The more we know, the more evidence we have to act and reduce plastic pollution in the future.