Geo News

A matter of microplastics

Tiny plastic motes suspended in the atmosphere have an impact on the global climate, according to research from a New Zealand team. As plastic degrades, weathered by the elements, it breaks down into smaller and smaller fragments. Microplastics are between five millimetres and one micron in size—one-hundredth the width of a human hair. They’re tiny, but they’re everywhere: from deep ocean trenches to remote Antarctic icescapes, and, closer to home, in our table salt and drinking water. They’re even airborne, floating in the air we breathe and transported far and wide on the wind. Airborne particles can absorb sunlight or scatter it “like tiny disco balls”, says the University of Canterbury’s Laura Revell, who led a study into the impact of microplastics on the global climate. Scattering has a cooling effect, while absorbing light warms the Earth. “They do both,” says Revell. The plastic particles are pretty good at reflecting sunlight back into space, but they can also absorb heat radiated from the Earth, contributing a tiny amount to the greenhouse effect. Revell estimates microplastics will have a “significant” effect as plastic waste grows. In another modelling study, researchers estimated the amount of microplastics in Waikato River drinking water, which Auckland uses. Their worst-case scenario had the concentration at around 65 particles per litre—about five to ten times less than similar cities around the world, thanks to our low levels of industrial activity, low population density, and advanced filtration methods.

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