Plastic bottles dumped in rivers can travel thousands of kilometres
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Environment



2 December 2020

By Ibrahim Sawal

Emily Duncan releases a bottle

Sara Hylton/NGS

Plastic bottles dumped in rivers can travel up to 3000 kilometres in just a few months. Following where bottles end up could help determine how best to tackle plastic pollution.

Emily Duncan at the University of Exeter, UK, and her colleagues used GPS and satellite technology, similar to those used for tracking animal movements, to follow the path of 25 plastic bottles. “We thought if we can track a turtle, why can’t we track a plastic bottle?” says Duncan.

The team released the bottles along the Ganges river in India and Bangladesh, which is the second largest contributing river to ocean plastic pollution. They found that the average bottle travelled at speeds of about 1 kilometre a day. Some ended up in the Bay of Bengal and travelled an average of 6 kilometres a day at sea.

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One bottle travelled roughly 3000 kilometres from the Bay of Bengal and circled around the east Indian coastline in 94 days. The fastest bottle travelled about 21 kilometres a day, but Duncan says they have the potential to travel much further and faster depending on ocean currents and wind speed.

The team found the bottles travelled in stepwise movements along the Ganges, with some 40 per cent becoming stranded on river banks. That waste could then get flushed out to sea during monsoon season.

“This can tell us how much effort we should put to inland waste management,” says Marcus Eriksen at the 5 Gyres Institute, a non-profit organisation in Santa Monica, California. “The most value is in what these bottles can tell us about where and when to remove trash from the world’s rivers,” he says.

Richard Thompson at the University of Plymouth, UK, says this data shows that rivers are important pathways for ocean plastic pollution. “Rivers are a one-way conveyor belt of material,” he says. “They connect the sea to people that could be living thousands of miles inland. And their actions can have an influence on the accumulations of plastic in the oceans.”

In 2010, an estimated 5 million to 13 million tonnes of plastic waste entered the world’s oceans.

“It’s also an important visual tool for social change and awareness,” says Duncan. Tracking how far plastic can travel gives communities and policy-makers ownership of their waste and can help stop ocean plastic pollution at its source, she says.

Journal reference: PLOS ONE, DOI: 10.1371/journal.pone.0242459

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