This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Rainfall from Hurricane Helene produced a short-term spike in microplastics at three sites in western North Carolina, with microplastic deposition three to 22 times higher than before the storm. The storm accounted for 18.8% of the annual microplastic deposition at Highlands Biological Station at Western Carolina University, 4.2% at Iron Duff in Haywood County and 4.6% at Coweeta Hydrologic Laboratory in Macon County.
"The microplastic footprint Helene left behind was pretty substantial," said Austin Gray, a Virginia Tech biologist. "Microplastics are depositing all over terrestrial and aquatic areas, especially after a storm event, and that changes what we consider an impacted zone since the particles deposited could have originated from areas far away." This was the first U.S.-based study to assess microplastic deposition before, during and after a hurricane. The research—conducted by a team from Virginia Tech, Western Carolina University, Highlands Biological Station and the University of North Carolina—was published recently in Integrated Environmental Assessment and Management.
Before Helene, researchers were measuring microplastics in the headwaters of the Richland Creek Watershed and the Cullasaja River Basin. They wanted to know how many microplastic particles were transported through the streams—and how many were floating in the atmosphere and deposited in these remote locations by rain or wind. To answer these questions, they measured microplastic accumulation at three locations, distinguishing between particles that settled in dry periods and those that settled in rainy periods.
The samplers were collecting through the storm that struck the southern Appalachian Mountains on Sept. 25, 2024, bringing 20 to 30 inches (51 to 76 centimeters) of rain and causing catastrophic flooding. The findings show that during Hurricane Helene, microplastic deposition was three to 22 times higher than before the storm. Data collection continued in the weeks after the storm, offering new insights into how microplastics circulate through the environment and the effects of a major storm and its aftermath.
Microplastics are usually associated with urban watersheds near roads and development. The headwaters targeted in this study are rural, forested and generally seen as pristine or less affected by microplastic pollution. "There's been very little investigation into microplastics within small headwaters, particularly low-order stream networks, but these small streams account for more than 70% of the total stream length in the continental U.S.," Gray said.
"And if it's happening in the headwaters, then it's going to flow downstream." But how are microplastics getting into headwaters? A recent study in Nature estimated that more than 600 quadrillion microplastic particles are in the atmosphere—that's 600 followed by 15 zeros. Working with Virginia Tech's Hosein Foroutan in civil engineering, Gray and his collaborators estimated that the storm released 385 quadrillion additional microplastic particles into the atmosphere above normal levels.
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