Microplastics - the tiniest plastic particles, ranging in size from fractions of a millimeter - have already been found in the human body, in food and even in Arctic ice. But how these particles move through the air is still almost unknown. A group of researchers led by CIRES (the Cooperative Institute for Research in Environmental Sciences at the University of Colorado) has proposed a new way to sample microplastics directly in the atmosphere using an uncrewed aerial vehicle (UAV). The results were published in the journal Scientific Reports.
"Atmospheric microplastics are usually collected from a rooftop, from the ground or from a ship," says Radiance Calmer, a former CIRES staff member and now a researcher at the Norwegian Polar Institute and the first author of the work. "Our study is a proof of concept: we showed that samples can be taken from a drone at a specified altitude."
To do this, the scientists adapted a device normally used for aerosol monitoring - a so-called cyclone sampler. It captures particles ranging in size from 1 to 10 micrometers (a micrometer is one thousandth of a millimeter). The device was mounted on a small drone. Because there is little microplastic in the air, the operating mode had to be tuned so that during a short flight - about 25 minutes - a sufficient volume of air could be passed through the sampler.
In the fall of 2024, the craft was flown over two locations in the state of Colorado: near a busy highway in the city of Erie, and over residential areas and a landfill in Arvada. The samples were then processed at the University of Colorado Boulder to separate plastic from organic particles and sent to the University of Rhode Island, where specialists counted the particles and identified the type of plastic.
The samples were dominated by so-called heteroaggregates - clusters of plastic and natural materials. Such formations are often found near roads and places of high human activity. The main conclusion: microplastics are indeed present at an altitude of 100 meters (about 328 feet) above areas where people are active. In addition, the work confirmed that the drone sampling method is suitable for measuring microplastics in the air. The authors became the first team to successfully use a cyclone sampler on a UAV to collect microplastics.
According to co-author Gijs de Boer, director of the environment and energy division at Brookhaven National Laboratory, plastic particles can be carried to places where no one is looking for them, and are therefore difficult to track. And this matters: microplastics are potentially hazardous to human health, and their effect on Earth's processes - for example, on cloud formation or sea ice melt - is still unknown.
The researchers emphasize that their work is only a first step. The new method could become a basis for sampling in hard-to-reach places, including the air over the ocean and the lower layers of the atmosphere, where traditional methods are limited and often too expensive. The team plans to go to the Arctic. At the same time, the authors do not claim that microplastics cause any particular effects: they are talking about correlation - a statistical association that by itself does not prove causation.