New Drone-Based Method Samples Microplastics 100 Meters Up in the Atmosphere

In the fall of 2024, a small uncrewed aircraft lifted off near a heavily trafficked highway in Erie, Colorado, carrying an instrument built to catch particles too small to see. Its flight time was about 25 minutes. It flew again over residential neighborhoods and a landfill in Arvada. Up at 100 meters, roughly 328 feet, it was collecting air in search of microplastics.

The work, led by CIRES, the research institute at the University of Colorado Boulder, was published in the journal Scientific Reports. It addresses a gap: microplastics have turned up in human bodies, in food, and in remote places such as Arctic seawater and ice, yet little is known about how they travel through the atmosphere. Most atmospheric sampling has been done from rooftops, ground-based stations or ships, which limits what researchers can learn about particles at a specific height.

Radiance Calmer, lead author and a former CIRES researcher now at the Norwegian Polar Institute, described the study as proof of concept. Her team showed that flights can sample atmospheric microplastics at a chosen altitude. Their results show microplastics are present 100 meters up near areas of intense human activity, and they confirm that drone sampling is a workable way to measure them. The team says it is the first to successfully use an environmental cyclone sampler on a UAS for collecting microplastics.

The project brought together experts from CIRES, CU Boulder and the University of Rhode Island, and the authors describe it as part puzzle in engineering and part in atmospheric science. The team adapted a cyclone sampler, an instrument commonly used in aerosol monitoring, to capture particles between 1 and 10 micrometers and mounted it on a small drone. Microplastics are sparse in the air, so the harder problem was gathering enough of them. As Calmer put it, the challenge was to sample a large enough volume of air that some microplastics would be present among all the other particles, and the short flight time made that difficult.

After the flights, the samples were preprocessed at CU Boulder to separate microplastics from organic particles. They then went to the University of Rhode Island, where researchers counted each particle and identified its plastic type. The samples were dominated by hetero-aggregates, clusters of plastic and environmental material that are often found near highways and other places with high human activity.

The authors say the method could provide a framework for sampling in remote settings, including above the ocean and in the lower atmosphere, where traditional approaches are limited and often too expensive. Gijs de Boer, a co-author who is now Environment & Energy Division director at Brookhaven National Laboratory and was previously a faculty research scientist at CIRES and CU Boulder, noted that microplastics can be carried to places people are not looking for them, which makes them hard to track. The stakes, the source says, are potential harm to human health and unknown effects on Earth system processes such as cloud formation and sea ice melting.

Calmer and de Boer, the principal investigators, credited the CIRES Innovative Research Program for getting the work started. The program is an internal competition that funds novel or unconventional research that can be hard to finance through traditional routes. De Boer compared such projects to a snowflake that turns into an avalanche, and said innovation often happens at interfaces, here between atmospheric science and aerospace engineering.

The team hopes the study opens the way to research on the long-range transport and origins of microplastics. Calmer said she hopes it becomes the launching point for another project, and that the group is aiming for the Arctic.