Microplastics on the Move: From City Streets to Caspian Shores

The world is full of tiny plastic pieces, but how they travel between land and sea is still a mystery. Scientists set up air samplers at seven different heights over the southern Caspian Sea and also used a vacuum pump to pull in air for two months. They collected samples from the coast, from the water surface, and from the nearby land for comparison. The results showed that most of the plastic in the air were fibers, with an average of about four particles per cubic meter. On the ground, the numbers were much higher, ranging from five to one thousand and a half pieces per kilogram of dry sediment.When the researchers calculated how much plastic moved horizontally near the surface, they found similar amounts coming in from the land and going out to the sea. The flow into the ocean was about 6, 500 particles per square meter each hour, while the outflow to land was around 8, 000. This balance suggests that during their three‑day field trip the system was fairly stable. To figure out where the plastic came from, they looked for other particles that travel with it—like sea salt and ash. By combining these clues with a computer model called FLEXPART, they traced the air back to its origins. The data pointed mainly to inland sources such as road dust and fibers shed from clothing, with only a small contribution from sea spray during the study period. These findings underline how far plastic can travel through the air and show that mixing real‑world measurements with modelling is a powerful way to pinpoint pollution sources.