URI team studies microplastics in Rhode Island waters

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CHARLESTOWN, RI – Researchers at the University of Rhode Island are collecting and analyzing microplastics in Narragansett Bay, coastal ponds, freshwater ponds in Worden and Roger Williams Park, and the Blackstone River, to determine what types plastics are the most prevalent and where most of them are found.

During an Aug. 15 presentation in Charlestown to members of the Salt Ponds Coalition, doctoral candidate Sarah Davis said plastic debris, which is present in almost every body of water, is an environmental problem because if little plastic is recycled.

“… It is estimated that 13 million tonnes of plastic enter our oceans every year,” she said. “You may also have heard the recent estimates that less than 10% of plastic is actually recycled, while it ends up in our global waste systems. Moreover, our waste management systems are simply not effective in dealing with very small pieces of plastic debris.”

Plastic waste can be divided into two broad categories: macroplastics, such as water bottles, which measure more than 5 millimeters, and microplastics, which measure from 5 millimeters to 1 micrometer.

Davis described several sources of plastic entering Narragansett Bay and freshwater bodies. One source, which might surprise many people, is clothing.

“Sewage-related debris…is a major source of microplastic fibers from clothing and microbeads from cosmetics,” she said. “A lot of our clothes are plastic. Polyester is one of the main woven plastics that we use as textiles, and every time we wash our clothes, we actually release thousands of fibers into the waste water that comes out of our washing machines, and if we are connected to local sewage systems, most sewage treatment plants cannot filter these tiny fibers and they are discharged at the outlets into our waterways.

Garbage is an obvious source of plastic pollution, as is industrial waste from plastic refineries. Some plastics also end up in the ocean during transportation, when tiny beads of pre-production plastic, called “nurdles,” are lost in transit.

Maritime and leisure industries also produce plastic waste.

“Lost or abandoned gear, such as nets and ropes, which are made of bundled plastic fibers such as polypropylene or nylon, also break down into tiny plastic fragments very quickly,” Davis said. “Cut or abandoned fishing line could also be a familiar plastic hazard to wildlife.”

Depending on their density, plastics float on the surface of water or sink. This in turn determines which organisms might ingest them, Davis said.

Quonochontaug Pond in Charlestown. Researchers from the University of Rhode Island are assessing the extent of plastic pollution in Narragansett Bay, as well as fresh and salt water ponds. (Cynthia Drummond/ecoRI News)

“Organisms that live in the sediment, such as clams, might be more affected by things like nylon or polyester that sink to the bottom, while seabirds and fish, which drag up the column of d water, could be more affected by fragments of polyethylene or polypropylene,” she said.

Plastics enter organisms when consumed or absorbed, usually through the gills. Ingested plastics disrupt hormone regulation and create what Davis described as “a false feeling of fullness” in which the body feels like it has eaten, when in fact it has not consumed any nutrients. Microplastics can also act as vectors for invasive species and disease, which are carried on the fragments.

Davis is currently part of a research team involved in three plastics projects: a seasonal assessment of plastic debris in surface waters of Narragansett Bay, an assessment of plastic pollutants in freshwater, and a study of how marine organisms interact with microplastics. through the food chain.

Using a net called a manta trawl, researchers sampled the waters of Narragansett Bay at several locations over two seasons.

“We want to produce a really robust, technically sound approximation of what’s going on in the bay, so our sites are spaced out the way they are,” Davis said. “We start with Providence, so really urbanized, [a] kind of an urban-rural gradient, which is great, not only adjacent to different levels of urbanization, but also different influences of things like currents, wind, boat traffic, rainfall runoff – all things that could influence the spread of microplastics. ”

Dressed in bright orange coveralls – so the fibers of their clothing can be differentiated from plastic fragments found in the water – the researchers deploy a manta trawl that is towed behind an URI research vessel for 10 minutes at each site.

In the lab, seawater is removed from the sample and a hyper-saline solution, denser than ordinary seawater, is added to help the plastic fragments float.

“Then,” Davis explained, “myself and our wonderful undergraduate assistants sit under the microscope and handpick any suspicious microplastics.”

Parts are affixed to slides and high resolution photographs are taken. The final step to confirming it is plastic involves inserting a very hot needle into each fragment. Non-plastic pieces burn, but plastic fragments melt.

The process is laborious, Davis said, because much of the work has to be done by hand.

“We’ve characterized over 3,000 particles from the berry so far, so that’s a lot of stinging,” she said.

The final step uses Raman spectroscopy, a type of analysis that uses laser light to create molecular vibrations that the spectrometer reads. It then produces a spectrograph that allows researchers to identify specific types of plastic polymers.

The results

The research team found no clear seasonal pattern in the abundance of microplastics, but preliminary results show that more microplastics have been recovered from Narragansett Bay near Providence.

Overall, however, compared to other water bodies, the bay falls roughly in the middle of the plastic pollution scale, with an average concentration of 0.3 microplastics per cubic meter.

Plastic litter quickly breaks down into small pieces. These fragments, called macro plastics because they measure more than 5 millimeters, washed up in the algae of Quonochontaug Pond in Charlestown. (Cynthia Drummond/ ecoRI News)

“I think it’s pretty good,” Davis said, “and it’s also pretty good when you compare it to other places… Monterey Bay Marine Sanctuary, in 2021, using methods of manta trawl, found an average concentration of 1.32 microplastics per cubic meter. So we’re definitely sitting lower than that, but we’re also sitting a bit higher than some other places. Chesapeake Bay found 0, 16. So we’re sort of in the middle.

There is also a relationship between tides and the abundance of microplastics, with more plastics found at low tide.

Researchers are still collecting freshwater samples, but the lack of rain this summer means there has been no stormwater to analyze.

There are several steps Rhode Islanders can take to reduce the prevalence of microplastics in saltwater and freshwater.

Davis suggested people wear natural fibers when out on the water, handle vinyl and PVC coated traps with care so the coating doesn’t come off, replace old marine ropes with natural fibers and to use reusable tarps instead of shrink wrap. to protect boats during wintering.

Davis said boaters should also try to recycle the shrink wrap they use.

“Woods Hole actually runs a recycling program every summer and has recycled thousands of tons of shrink wrap,” she said.

Local shrink wrap recycling is available through Clean Ocean Access.


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