PARTICLE DETECTORS

To tackle the growing problem of plastic pollution in the oceans, it’s vital to know where plastics are, where they move and what they’re made of – especially flurries of microplastics. These tiny plastic particles are smaller than 5mm in size, and can be difficult to find.

“At the moment, if you want to know the distribution of particles in the deep sea you have to sample them,” says Dr Tomoko Takahashi, postdoctoral researcher at Japan Agency for Marine-Earth Science and Technology (JAMSTEC). That takes time, either using nets or water bottles, which have to be hauled up to a ship and sent off for laboratory analysis. Researchers from the University of Southampton, the University of Aberdeen, JAMSTEC and the University of Tokyo, are developing a prototype particle detector that could soon automate the process and help monitor plastics, as well as other tiny particles – natural or human-made – in the deep sea.

Their device consists of a 20cm chamber, which seawater flows along. The chamber contains a single laser, and when a particle is present it scatters the laser light, creating a high-resolution holographic image. This can help to identify the particle, be it plastic or plankton. The same laser also analyses the chemical make-up of the particle, using a method called Raman spectroscopy. In tests, the device has successfully distinguished between 3mm pellets of polystyrene and acrylic.

The team’s ultimate goal is to produce a fully automated device that could continuously monitor the oceans. Fixed to floats or gliders that cruise around the ocean gathering data, the particle detectors could be deployed for months, even years at a time, beaming back information on the types and abundance of plastics and other particles all through the oceans.