A study(Opens in a new window) published this month by scientists in the Netherlands suggests that the sun might break down plastics floating on the ocean’s surface. A team of marine specialists from the Royal Netherlands Institute for Sea Research (NIOZ) has found that in simulative ocean settings, ultraviolet (UV) light—the kind emitted by the sun—gradually degrades plastics, helping to reduce seawater pollution and potentially resolving what scientists call the “Missing Plastic Paradox.”
Environmentalists, marine biologists, and other researchers have been studying ocean-polluting plastics for some time now, but the Missing Plastic Paradox has been a constant head-scratcher. While scientists know approximately(Opens in a new window) how much plastic enters the ocean on a regular basis, they can’t actually locate some of it—it’s just gone. This naturally begs the question: Where does all that plastic end up?
(Image: Naja Bertolt Jensen/Unsplash)
In the NIOZ lab, researchers simulated ocean pollution and the sun’s UV rays by mixing up a “plastic soup” consisting of seawater and common plastics. These plastics included the most common polluters found on the ocean’s surface: polyethylene-terephthalate (PET), polystyrene (PS), polyethylene (PE), and polypropylene (PP). Each piece of plastic was barely larger than a microplastic, imitating the shape and size of pollutants capable of floating rather than sinking.
A 460-watt halogen lamp beamed UV rays similar to solar UV-A/B light at the plastic soup while a shaker table imitated the motion of ocean waves. Over the course of several days, the researchers monitored the plastic particles’ physical integrity. They found that UV rays broke each plastic particle into smaller pieces, eventually creating nanoplastics (plastics that are so small, they’re invisible to the naked eye) and molecules like the ones found in crude oil. These can chemically dissolve or be broken down further by bacteria.
Based on the rate of degradation measured in their experiment, the NIOZ researchers estimate that the sun breaks down common surface-level plastic pollutants by 1.7% to 2.3% per year. At this rate, anywhere from 7% to 22% of plastic ever released to the sea could have already been broken down by UV rays. While these statistics are encouraging, the scientists warn that this isn’t an umbrella solution to plastic pollution. Such a rate of degradation is too slow to fully rid the ocean of all its plastics; additionally, test plastics released organic carbon, carbon dioxide, carbon monoxide, methane, and other gasses as they broke down. The solution, they write, is still to mitigate which plastics are produced in the first place.
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