02 Nov 2026
Could raindrops be launching microplastics from the ocean into the air?
A new study involving Oxford scientists shows how raindrops hitting contaminated water can send microplastics into the air, offering clues about how plastic pollution spreads through the environment.
Tiny plastic particles have been found in the world's oceans, remote mountain regions, and even in the air we breathe. Yet we still know surprisingly little about how they move from water into the atmosphere.
Researchers from the University of Oxford, University College London (UCL), and the National Autonomous University of Mexico (UNAM) have been investigating whether something as ordinary as rainfall could play a part.
In a study published in the Journal of Colloid and Interface Science, the team used high-speed cameras to observe what happens when water droplets strike a surface covered with microscopic plastic particles.
They found that microplastics can be thrown into the air in two ways: through the initial splash, and through a thin jet of water that shoots upwards as the crater left by the drop collapses. In some experiments, a single ejected droplet carried around 100 microplastic particles.
The researchers also found that the surface properties of the particles made a striking difference to how easily they were ejected from the water. Muhammad Hamza Iqbal, lead author of the study and PhD researcher at UCL, said: “What struck me most was how changing just the surface properties of the particles could completely change what happened to them when a drop hit the water.”
Some of the most water-repellent particles even formed tiny droplets wrapped in a shell of plastic, known as liquid marbles. These droplets resist merging back into the water, potentially allowing the plastic particles to remain dispersed for longer.
The experiments were carried out under controlled laboratory conditions, so there is still work to do to understand how significant this process might be in the natural environment.
Professor Alfonso Arturo Castrejón-Pita, Professor of Fluid Dynamics said: “Microplastics are now everywhere and understanding how they spread is hugely important if we are to track them and perhaps eventually contain them. What happens when a single raindrop strikes contaminated water illustrates just how complex these processes are, and how difficult it is to quantify their effects.”
Read the paper - Droplet impact on a particle-laden liquid interface: Worthington jet dynamics and microplastic ejection from floating rafts here: https://www.sciencedirect.com/science/article/pii/S0021979726020072
