USF student: hurricanes and humidity send microplastics from sky to Tampa Bay; hotspot found near EPC air-monitoring site

Lindsey Grossman, a PhD student at the University of South Florida, presented master's-level research on microplastics in Tampa Bay and on atmospheric deposition in and around the county's monitoring sites.

Grossman said previous local studies show microplastics in surface waters and sediments of Tampa Bay and in organisms including plankton, oysters and even the digestive tracts of deceased manatees. She described a sampling program that used rain and dry-deposition samplers at five sites and analyzed collected particulates with an infrared microscopy technique to identify polymer types.

"During the hurricane, we had a max of 95,000 microplastics per meter squared per day," Grossman told commissioners while noting a site near EPC's air monitoring station showed a pronounced hotspot. She reported a site average of roughly 50,000 microplastics/m^2/day in that location, with a minimum measurement of about 18,000/m^2/day in the sampling period presented.

Grossman also said one existing study estimated about 1 ton of plastic per year travels down the Hillsborough River into Tampa Bay. She explained the infrared method is limited in reliably detecting black tire-wear particles because they absorb the instrument's light, but image-analysis suggests tire-related particles are present at very high counts on some filters.

Her recommendations to the commission included forming a working group to standardize methods and expand monitoring across Tampa Bay, develop consistent reporting, and focus attention on tire-wear particles and storm-related transport mechanisms.

The commission voted to receive the presentation; no regulatory measures were adopted at the meeting.