Utah State University Assistant Professor Janice Brahney and her team recently published a study looking at microplastics emitted into the atmosphere. The team used high-resolution atmospheric deposition data and identified samples of microplastics and other particles collected over 14 months from 11 national parks and wilderness areas. In the samples, the researchers identified plastic and polymers composition to identify the sources of plastic committed to the atmosphere and track its movement fallout.
Brahney says that she and her team were “shocked” at the estimated deposition rates and tried to figure out where their calculations were wrong. The team went through 32 different particle scans to confirm their findings and found that roughly 4% of the atmospheric particles analyzed in remote locations were synthetic polymers. The world produced 348 million metric tons of plastic in 2017, and global production shows no signs of slowing.
The high resilience and longevity of plastics make them very useful in everyday life. Still, the same properties lead to progressive fragmentation instead of degradation into the environment, according to the team. That creates so-called microplastics that are known to accumulate in wastewaters, rivers, and, ultimately, the world’s oceans. The new research shows that they also accumulate into the atmosphere. The study looked at sources of both wet and dry microplastic deposition. Wet deposition occurs via rain.
The study shows that cities and population centers serve as the primary source of plastics associated with wet deposition. Still, secondary sources include the redistribution of microplastics re-entrained from soils or surface waters. Dry deposition of plastics showed indicators of long-range transport that is associated with large-scale atmospheric patterns. The team says that suggest microplastics are small enough to be entrained in the atmosphere for cross-continental transport.
The researchers say that most of the plastics deposited in both wet and dry samples were microfibers sourced from clothing and industrial materials. About 30% of the particles were brightly colored microbeads made of acrylic and derived from industrial paints and coatings. Other particles are fragments of larger pieces of plastic. The samples allowed the team to estimate that more than 1000 tons of microplastics are deposited onto protected wetlands in the western United States each year, which is equivalent to more than 123 million plastic water bottles.