Study Challenges Ocean as Primary Source of Airborne Microplastics

A new study by the Department of Meteorology and Geophysics at the University of Vienna has challenged many of the existing beliefs about where airborne microplastics originate from. In previous years, it was believed that most microplastics originated from the ocean, and this assumption has been refuted, based on a study published in Nature that says land-based sources contribute far more particles to the atmosphere than ocean-based sources.

The study compared a total of 2782 atmospheric data samples collected from around the world and advanced transport models to indicate that land-based sources contribute approximately 20 times more microplastics to the atmosphere than the ocean. The new results demonstrate that it is crucial to develop accurate data on the quantities of particles in the atmosphere from various sources and the abrasion of transportation network surfaces to fully understand how these synthetic products move through the Earth's atmosphere.

According to the University of Vienna, the research was conducted by Ioanna Evangelou, Silvia Bucci and Andreas Stohl, who used an extensive database of 2,782 atmospheric samples collected all around the globe, from which they were able to determine the true source of these particles found throughout the environment. The results represent a paradigm shift in environmental science and suggest that, unlike in the past, when oceanic spray was considered a major source of microplastics in the atmosphere, land-based sources (primarily from the tyre abrasion on the road and the shedding of synthetic textile fibres) are now the primary contributor to atmospheric microplastics.

Given this new information, the researchers concluded that the human-dominated land environment is producing over 20 times more microplastics than the ocean, thus changing our understanding of plastic pollution across the globe.

A critical component of this study involved a rigorous comparison between real-world atmospheric observations and the results generated by existing transport models. The research team discovered that prior modelling efforts consistently overestimated the prevalence of microplastic particles, often by several orders of magnitude, both in the air and upon deposition to the Earth's surface. By identifying this significant gap between theoretical predictions and empirical data, the team was able to recalibrate their models to account for the disparity between land and ocean emission profiles, as noted in research published in Nature. This technical adjustment successfully corrected long-standing errors, providing a much more accurate and scientifically grounded representation of how these pollutants are distributed across the planetary atmosphere.

Despite major developments with this work, lead author Andreas Stohl admits there are still significant uncertainties present, particularly in how accurately we know the size distribution of the airborne particles. While the majority of the particle count came from land-based sources, the researchers pointed out a surprising exception: the total mass of emitted particles is greater over the ocean because oceanic particles tend to be larger than land-derived particles. The research team clearly states that a continued need exists for improved data collection methods and improved methods to separate the contributions from specific sources (for example, automotive vs. various types of industrial emissions) to improve the emission estimates of individual sources, as well as gain a clearer understanding of the long-term effect on the environment.