On-Site Monitoring of Ocean Plastic Particles

By Devin Partida

Everything from shopping bags to toys contains plastic, and the material remains widespread around the world. Unfortunately, only 9 percent of all plastic  gets recycled. A related issue is that many of the varieties used today have chemical makeups that prevent full decomposition.

These realities mean that plastics in the ocean is a major problem, polluting the beaches and ending up in the bodies of humans and sea creatures alike.

Holographic Imaging and Spectrography

Scientists are still learning how small plastic particles reach and spread from the ocean’s deepest areas. A new system based on light could help them understand more about what happens.

A research team has used high-resolution holographic imaging plus chemical information from Raman spectroscopy, which works based on how light interacts with chemical bonds.

The researchers created a lab environment where they pass one laser beam through a seawater channel less than 8 in. long. When plastic particles are in the water channel, they interact with the light from the laser beam and create optical interference patterns. Scientists can then rely on that to see a high-resolution representation of a plastic object’s shape.

Because a small amount of the light causes a molecular interaction with the material, that event alters the light’s wavelength and makes a spectral fingerprint to reveal the particle’s composition.

The team used their method to find two varieties of plastic pieces and confirm their chemical composition. They described their experiments in the journal Applied Optics.

Their technique should be able to detect a variety of plastic in as little as a liter of liquid. 

A Notable Ocean Research Development

The team has created an on-site method of finding ocean plastics. It’s also a low-power option potentially
well-suited to long-term observation that does not require preparing or altering seawater samples. Combining this new approach with autonomous underwater vehicles or gliders could help researchers cover large areas.

The conventional method involves using a filter or trap to gather plastic for study in labs. This captures the water condition at a few locations over brief periods.

The new method could help scientists learn more about the origins of plastics in oceans by enabling on-site analysis, making them better equipped to solve the problem of plastics pollution.

Devin Partida writes about science and technology. She is the editor-in-chief of ReHack.com.


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