The atmosphere plays a major role in dispersing microplastics around the planet, transporting these tiny particles to the most remote regions. People and animals can inhale them, raising concerns about possible health effects. Once airborne, microplastics can fall to Earth and increase pollution of oceans and soil around the world.
A new study from the Department of Meteorology and Geophysics at the University of Vienna provides a clearer picture of where these airborne microplastics come from. Researchers use global measurements and computer models to estimate emissions from both land and ocean sources. Their key finding was surprising: land releases 20 times more microplastic particles into the atmosphere than the ocean. The study was recently published in the journal Nature.
Sources of airborne microplastics
Scientists have long known that microplastics exist in the atmosphere around the world. These particles eventually settle in isolated locations far away. They come from direct sources such as tire wear and textile fibers, as well as from previously contaminated land and ocean surfaces that release particles into the air.
Until now, the magnitude of these emissions and the contribution of each source have not been well understood. Previous studies have often pointed to the ocean as the main culprit, but new discoveries cast doubt on that assumption.
Comparing models and real-world measurements
To better understand the issue, researchers Ioanna Evangelou, Sylvia Bucci and Andreas Stoll compiled 2,782 individual measurements of atmospheric microplastics from studies conducted around the world. We then compared these real-world observations to the results of a transportation model that incorporates three different published emissions estimates.
The comparison revealed a major problem. The model consistently predicted far more microplastic particles in the air and deposited on the ground than actually observed, sometimes by orders of magnitude greater. This gap allowed researchers to adjust their models to adjust emissions estimates by land and ocean sources, resulting in more accurate results.
Land dominates microplastic emissions
After recalibrating the data, the researchers found that the initial model had significantly overestimated emissions from land, but that land remained the dominant source after the corrections. Marine emissions were also revised downward.
When asked where most of the airborne microplastics come from, lead author Andreas Stoll explained: “Currently scaled-up emissions estimates show that land releases more than 20 times as many microplastic particles as the ocean.” At the same time, lead author Ioanna Evangelou pointed out an important detail. “However, the actual mass released is greater in the ocean than on land, because the average size of ocean particles is larger.”
Continued uncertainty and need for more data
This research is an important step toward understanding how microplastics move through the atmosphere and spread globally. However, significant uncertainties remain.
“However, the data situation is still not satisfactory and large uncertainties remain. Further measurements are needed to know how much microplastics are coming from traffic and how much from other sources. The size distribution of the particles is also highly uncertain and therefore we do not know the total amount of plastics transported into the atmosphere”, summarizes Andreas Stoll, lead author of the study.
Summary of key findings
- Measurements of the global distribution of microplastics in the atmosphere were compared with model simulations.
- The comparison showed that the model overestimated the number of measured microplastic particles by several orders of magnitude.
- This clearly shows that the emissions estimates used so far are too high, especially for land-based emissions.
- The number of microplastic particles released from land is more than 20 times the number released from the ocean.
- More accurate emissions estimates require more accurate measurements. In particular, the size distribution of plastic particles is a major source of uncertainty and has not been recorded with sufficient precision in previous measurement data.
