Did you know that there are more pieces of plastic in the ocean than stars in the Milky Way galaxy? Over 14 million tons of plastic enter the ocean annually, 40 percent of which is considered “single-use”, which means it goes into the water within the same year that it was produced. Most plastics just fragment down into smaller pieces called microplastics, never breaking down completely in the process.
What Are Microplastics?
Microplastics are pieces of plastic under five millimeters in length and come from a variety of sources, including from larger plastic debris that degrades into smaller and smaller pieces.
Our increased reliance on plastics for countless applications has negative consequences on the environment. For example, the plastic manufacturing process is associated with air pollution, and volatile organic compounds released over the life of the plastic have deleterious health effects for humans. Plastic waste takes up significant space in landfills. Microplastics have been found in every corner of the globe, from the deepest part of the Mariana Trench to the top of the French Pyrenees.
Addressing this plastic pollution problem, of course, requires limiting plastic production. But innovators are also exploring ways to clean up plastic and microplastic that’s already in the ocean.
Environmental Effects of Microplastics
- Many persistent organic pollutants (aldrins, HCBs, DDT, PCBs, and dioxins) float around the oceans at low concentrations, but their hydrophobic nature concentrates them on the surface of plastic particles. Marine animals mistakenly feed on the microplastics, and at the same time ingest the toxic pollutants. As the pollutants are transferred up the food chain, the concentration of these toxicants increases in the animal tissues.
- As the plastics degrade and become brittle, they leach out monomers like BPA which can then be absorbed by marine life, with relatively little known consequences.
- Besides the associated chemical loads, ingested plastic materials can be damaging for marine organisms, as they can lead to digestive blockage or internal damage from abrasion.
- Being so numerous, microplastics provide abundant surfaces for small organisms to attach. This dramatic increase in colonization opportunities can have population-level consequences. In addition, these plastics are essentially rafts for organisms to travel further than they usually would, making them vectors for spreading invasive marine species.
A scientifically-approved solution
To decompose the microplastics, the researchers had to generate short-lived chemicals called reactive oxygen species, which trigger chain reactions that chop the various long molecules that makeup microplastics into tiny and harmless segments that dissolve in water.
However, reactive oxygen species are often produced using heavy metals such as iron or cobalt, which are dangerous pollutants in their own right.
To get around this challenge, the researchers found a greener solution in the form of carbon nanotubes laced with nitrogen to help boost the generation of reactive oxygen species. The process converts the plastic into carbon dioxide and water.
Proven through laboratory tests, carbon nano springs are strong and stable enough to break these microplastics down into compounds that do not pose such a threat to the marine ecosystem.
Shaped like a coil/spring, which increases stability and maximizes the reactive surface area, the carbon nanotube catalysts removed a ‘significant fraction’ of microplastics in just eight hours while remaining stable themselves in the harsh oxidative conditions needed for microplastics breakdown.
Scientists have also developed a substitute by coating carbon nanotubes with nitrogen. The inclusion of a small amount of manganese not only enhances its stability but also imparts the tubes their magnetic properties. These are particularly exciting because the nanotubes can be easily recovered from wastewater streams, providing repeated use. What do you think about this? Feel free to share your views on this in the comments section.