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Thousands of tons of COVID-related plastic could end up in the ocean

The COVID-19 pandemic has generated more than eight million tons of plastic waste since its start, most of it single-use plastic for personal protective purposes. This is according to a new model, developed by researchers at the Nanjing University in China. 

A portion of this plastic will end up entering the oceans of the world, and will either sink to the bottom or remain floating on top until it collects on beaches, in oceanic gyres or in the seas of the Arctic. 

The Nanjing University MITgcm-plastic model (NJU-MP) that was developed and used in this study works like “a virtual reality,” according to Yanxu Zhang, professor at the School of Atmospheric Sciences at Nanjing University. He said that the model was built based on Newton’s laws of motion and the law of conservation of mass. 

“The model simulates how the seawater moves, driven by wind, and how the plastics float on the surface ocean, degraded by sunlight, fouled by plankton, landed on beaches, and sank to the deep,” said Professor Zhang. “It can be used to answer ‘what if’ questions, for example, what will happen if we add a certain amount of plastics to the ocean?”

The researchers used data from the start of the pandemic in 2020 through August 2021, and found that most of the global pandemic plastic waste entering the ocean comes from rivers in Asia; they account for 73 percent of the total discharge of plastics. 

The three biggest contributors to ocean plastic pollution are the Shatt al-Arab, Indus, and Yangtze Rivers, which discharge into the Persian Gulf, Arabian Sea, and East China Sea respectively. European rivers account for 11 percent of the discharge, and other continents have only minor contributions to the problem. 

The study, led by a team of researchers at Nanjing University’s School of Atmospheric Sciences and UC San Diego’s Scripps Institution of Oceanography, found that the bulk of pandemic plastics discharged on land were derived from medical waste. This was particularly true in areas where waste management was already under pressure before the start of the pandemic.

“When we started doing the math, we were surprised to find that the amount of medical waste was substantially larger than the amount of waste from individuals, and a lot of it was coming from Asian countries, even though that’s not where most of the COVID-19 cases were,” said study co-author Amina Schartup, an assistant professor at Scripps Oceanography. 

“The biggest sources of excess waste were hospitals in areas already struggling with waste management before the pandemic; they just weren’t set up to handle a situation where you have more waste.”

Out of the more than eight million tons of pandemic-associated plastic generated globally, more than 25,000 tons would enter the global ocean. The model predicted that, within three to four years, a significant portion of this ocean plastic debris would either be washed up on beaches or sink to the seabed. 

However, a portion will likely go into the open ocean, eventually being trapped in the centers of ocean basins or subtropical gyres, or ending up in a circumpolar plastic accumulation zone in the Arctic Ocean. 

While this Arctic accumulation zone does not yet exist, the model predicts that, due to ocean circulation patterns the Arctic Ocean appears to be a “dead-end” for plastic debris transported in the oceans of the world. The model shows that about 80 percent of the plastic debris that transits into the Arctic Ocean will sink quickly, but a circumpolar plastic accumulation zone is predicted to form by 2025. 

“There is a pretty consistent circulation pattern in the ocean, and that’s why we can build models that replicate how the ocean moves – it’s just physical oceanography at this point,” said Schartup, whose research normally focuses on understanding mercury in the oceans. 

“We know that if waste is released from Asian rivers into the North Pacific Ocean, some of that debris will likely end up in the Arctic Ocean – a kind of a circular ocean which can be a bit like an estuary, accumulating all kinds of things that get released from the continents.”

The Arctic ecosystem is already particularly vulnerable due to the harsh environmental conditions and sensitivity to global warming. The addition of plastic pollution to this already fragile system carries further threats to the organisms that live there and adds another layer of concern.

The authors stress the importance of better management of medical waste derived from treating COVID-19 patients, particularly in developing countries where management systems may already be insufficient. They also call for global public awareness of the environmental impact of personal protection equipment (PPE) and other plastic products, and the development of innovative technologies for better plastic waste collection, classification, treatment, and recycling, and development of more environmentally friendly materials.

“Indeed, the COVID-related plastic is only a portion of a bigger problem we face in the 21st century: plastic waste,” said Zhang. “To solve it requires a lot of technical innovation, transition of economy, and change of lifestyle.”

The study is published today in the journal Proceedings of the National Academy of Sciences.

By Alison Bosman, Staff Writer

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