Microplastics in the atmosphere: Higher emissions from land areas than from the ocean

(Press-News.org) The atmosphere is an important transport medium that carries microplastics to even the most remote parts of the world. These microplastics can be inhaled and pose a health risk to humans and animals. They can also settle out of the atmosphere and contaminate oceans and soils worldwide. A new study by the Department of Meteorology and Geophysics at the University of Vienna estimates microplastic emissions from land-based and oceanic sources into the atmosphere based on global measurement data and model simulations. The results: over 20 times more microplastic particles are emitted on land than from the ocean. The study was recently published in Nature.

It is now well documented that the atmosphere worldwide is contaminated with microplastic particles, which then settle even in the most remote parts of the world. The microplastics originate from primary sources such as tyre abrasion or textile fibres, as well as from the resuspension of already contaminated land or the ocean. However, the magnitude of these emissions and their distribution among emission sources was previously unknown. In previous studies, the ocean was often cited as the main source.

About the study: Systematic comparison of model calculations and measurements

In the current study, Ioanna Evangelou, Silvia Bucci and Andreas Stohl from the University of Vienna collected 2,782 globally distributed individual measurements of microplastics in the atmosphere from the literature. The meteorologists then compared these measurements with simulations with a transport model that used three different published emission estimates. The scientists found that the model overestimates the number of microplastic particles in the atmosphere and their deposition on the Earth's surface by several orders of magnitude, both over land and over the ocean. Using this systematic discrepancy between model results and observations, the Vienna-based researchers were able to rescale the emissions separately for land and ocean emissions. This resulted in improved emission estimates.

Specifically, it turned out that the number of particles emitted on land had to be revised significantly downwards in order to reconcile the model results with the measurements. Ocean emissions were also largely overestimated. When asked where more microplastics enter the atmosphere, the study's lead author, Andreas Stohl, says: "The now scaled emission estimates show that over 20 times more microplastic particles are emitted on land than from the ocean." "However, the emitted mass is actually higher over the ocean than over land, which is due to the larger average size of oceanic particles," adds first author Ioanna Evangelou.

More measurements needed to clearly classify microplastic pollution

With this study, the scientists are taking an important step towards better estimating the pollution of the atmosphere with microplastics and their global transport. "However, the data situation is still not satisfactory, and there are still major uncertainties. More measurements are needed so that we know how much microplastic comes from traffic and how much from other sources. The size distribution of the particles is also highly uncertain, and thus the total amount of plastic transported in the atmosphere," summarises Andreas Stohl, lead author of the study.

Summary:

Globally distributed measurements of microplastics in the atmosphere were compared with model simulations. The comparison showed that the model overestimates the number of measured microplastic particles by several orders of magnitude. This is a clear indication that the emission estimates used to date are far too high, especially for land-based emissions. The number of microplastic particles emitted from land is more than 20 times higher than the number of particles emitted from the ocean. More accurate measurements are needed for more precise emission estimates. In particular, the size distribution of plastic particles is a major source of uncertainty that has not been recorded accurately enough in the measurement data to date. Environment and Climate Research Hub at the University of Vienna:

Andreas Stohl is Vice-Dean of the Faculty of Earth Sciences, Geography and Astronomy and a member of the University of Vienna's interdisciplinary Environment and Climate Research Hub (ECH). This network brings together researchers from a wide range of disciplines to gain excellent scientific insights that can offer solutions to pressing problems such as climate change, biodiversity loss and environmental pollution.

About the University of Vienna: 

For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected. With degree programmes covering over 180 disciplines, and more than 10,000 employees we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.

END