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Sunlight can break down marine plastics into tens of thousands of compounds

WHOI postdoctoral researcher Taylor Nelson (left) and PhD student Anna Walsh are investigating sun-exposed plastics at WHOI’s outdoor laboratory. According to new research, sunlight can break down marine plastics into tens of thousands of compounds, which is at least 10 times more complex than previously understood.Credit: Woods Hole Oceanographic Institution

Sunlight was once thought to chemically resemble the plastic of the marine environment to its original material, only fragmenting it into tiny particles that last forever. But recently, scientists have also learned that sunlight chemically transforms plastics into a range of polymer, dissolved, and vapor-phase products.


Now, new research shows that this chemical reaction can produce tens of thousands of water-soluble compounds or formulations. Decomposition into many of these equations is at least 10 times more complex than previously understood in the coming weeks.

“There is increasing evidence that photochemical conversion of plastics is an important conversion process. Surface water According to the treatise, the formulation of plastics is a new control of its photochemical fate in the ocean, Environmental science and technology..

NS Scientific community“We assume that exposure to sunlight will only physically fragment macroplastics into microplastics and then survive forever in the environment,” said policy makers, industry, and others. The paper, led by Anna Walsh, a student at the University Woods Hole, states. Joint Program of Oceanographic Institutions (WHOI) in Chemical Oceanography. Along with the findings in the literature, the new discovery “has a radical challenge to this guideline, a series of sunlight that not only helps the physical fragmentation of plastics, but also chemically alters them and no longer resembles the base metal. It shows that it produces a transformation product. “

“It’s amazing to think that sunlight can break down plastic. Plastic is usually a compound with several additives mixed into tens of thousands of compounds that dissolve in water. It will be decomposed, “said Colin Ward, an assistant to WHOI’s oceanographic chemistry. And the geochemistry department.

“We need to think not only about the fate and impact of the first plastics that leak into the environment, but also about the changes in those materials,” says Ward. “We still don’t know how these products will affect biogeochemical processes such as aquatic ecosystems and the carbon cycle. It may seem good for plastics to decompose faster than expected. Maybe, but it’s unclear how these chemicals affect the environment. “

In this study, we investigated the decomposition of four different disposable consumer polyethylenes in sunlight. Plastic bag We compared them to pure polyethylene film from three major retailers that manufacture many plastic bags from Target, CVS and Walmart. Most plastics, including these retail bags, are not only pure base resins, but also contain complex formulations of chemical additives that make the plastics work or look in a particular way. Up to about one-third of the mass of each retailer’s plastic bag was inorganic additives.

The organic compounds produced by sunlight were analyzed at the National Institute of High Magnetic Fields, which designed and developed a mass spectrometer with 21 Tesla magnets for the world’s highest mass resolution and accuracy. In essence, this device is the finest scale in the world, allowing scientists to determine the composition of solar-generated formulations.

When exposed to sunlight, researchers say that four retail bags produce about 5,000 formulas (for target bags) to 15,000 formulas (for Wal-Mart bags), and pure polyethylene film produces about 9,000 formulas. I found that. Scientists have also found that the composition of manufactured formulations differs between pure plastics and consumer plastics.

Many previous studies of marine plastics have generally used pure polymers. Marine environment.. This paper calls on the research community to “accept diverse formulations of plastics and solar conversions in the ocean” in order to comprehensively and accurately understand the fate and impact of marine plastic pollution.

“If our goal is to understand the fate and impact of these materials, we need to study the plastics that represent the plastics that are actually leaking into the environment and the weathering processes that act on them.” Says Ward.

Co-author Christopher Lady, senior scientist in the Department of Marine Chemistry and Geochemistry at WHOI, said: “By simply changing the ingredients in the recipe, the plastics industry can become more prone to failure when the product reaches its useful life.”

“There is plenty of room for academia and industry to work together on this issue,” Ward adds. “One of the logical ways to solve a problem faster is to work with people who develop the material and understand its composition. Ideally, reblend the plastic and make a benign product. Understand how to accelerate degradation or minimize production of non-benign compounds. “

A previous paper by Ward, Reddy, and lead author Taylor Nelson, a postdoctoral fellow in the Department of Marine Chemistry and Geochemistry at WHOI, prevented biofilms growing on the plastic of marine screens from reaching the plastic surface. , Shows that it may delay the deterioration of plastics due to sunlight. Like Walsh’s treatise, Nelson’s treatise plasticIt affected the extent of this effect, including the presence of additives.


Sunlight decomposes polystyrene faster than expected


For more information:
Anna N. Walsh et al, Plastic Formulation, is a new control of its photochemical fate in the ocean, Environmental science and technology (2021). DOI: 10.1021 / acs.est.1c02272

Quote: Nikko can break down marine plastics into tens of thousands of compounds (2021, September 8). Obtained from https: //phys.org/news/2021-09-sunlight-marine-plastic-tens-thousands.html on September 8, 2021

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Sunlight can break down marine plastics into tens of thousands of compounds

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