Most people have heard of microplastics and how they’ve been found everywhere from the bottom of the ocean to the top of Mt. Everest to the human bloodstream. But did you know they are also in hurricanes? The atmosphere is responsible for transporting all kinds of particles around the world, including microplastics. While the atmospheric limb of the global plastic cycle has been extensively researched in the past few years, there are still many questions, including what is the role of meteorological events, such as hurricanes, on the transport and deposition of microplastics in the atmosphere?
Hurricane Larry: A unique opportunity
We were able to investigate this question in the form of Hurricane Larry, which passed over Newfoundland, Canada in September 2021 as a category 1 hurricane. The storm followed a path offshore the east coast of the United States, crossing the garbage patch in the North Atlantic and not making landfall until it reached Newfoundland. Newfoundland has a relatively low population density meaning most of the land is remote and doesn’t have direct sources of microplastic. This gave us a unique opportunity to study how much microplastic was coming from the hurricane without worrying about input from other sources.
During the peak of the hurricane, a staggering 1.13 x 105 microplastics m-2 day-1 were deposited. This amount is much higher than totals in previous studies investigating microplastic deposition during monsoon or typhoon events. Even during fair-weather conditions before and after the hurricane, deposition amounts were relatively high compared to previous studies, typically falling within the range of ca. 500 to 6,000 MPs m-2 day-1.
The ocean as a source
Using polymer type analysis and air parcel back-trajectory modelling, it is highly likely the microplastics analyzed in this study were sourced from the North Atlantic Ocean. The ocean is often thought of as a sink for microplastics, but particles in the surface waters can be resuspended into the atmosphere and deposited elsewhere. The extreme deposition during the storm can be attributed to Hurricane Larry intersecting with the North Atlantic garbage patch, an area with high concentrations of microplastics in the surface waters.
Implications for remote areas
Our study underscores the impact of North Atlantic hurricanes on the atmospheric transport and deposition of ocean-sourced microplastics. The implications are far-reaching, especially for remote areas that may be less equipped to handle increased exposure to microplastics which can be detrimental to humans, wildlife, and even climate processes. As these storms continue to intensify and change patterns due to climate change, understanding their role in the global movement of microplastics becomes increasingly crucial.