Plastic rain in protected areas of the United States

TLDR

Eleven billion metric tons of plastic are projected to accumulate in the environment by 2025, and their persistence leads to fragmentation into wind‑entrainable fragments. The study aims to determine whether wet‑ and dry‑deposited plastics have distinct atmospheric life histories and to quantify their deposition rates and sources to remote U.S. conservation areas. High‑resolution spatial and temporal data were used to assess deposition patterns of plastics under wet and dry conditions.

Abstract

Eleven billion metric tons of plastic are projected to accumulate in the environment by 2025. Because plastics are persistent, they fragment into pieces that are susceptible to wind entrainment. Using high-resolution spatial and temporal data, we tested whether plastics deposited in wet versus dry conditions have distinct atmospheric life histories. Further, we report on the rates and sources of deposition to remote U.S. conservation areas. We show that urban centers and resuspension from soils or water are principal sources for wet-deposited plastics. By contrast, plastics deposited under dry conditions were smaller in size, and the rates of deposition were related to indices that suggest longer-range or global transport. Deposition rates averaged 132 plastics per square meter per day, which amounts to >1000 metric tons of plastic deposition to western U.S. protected lands annually.