Satellite-tagged bottles show promise for tracking plastic litter through rivers

Plastic pollution threatens natural ecosystems and human health worldwide. Previous research suggests that rivers transport up to 80 percent of the plastic pollution found in oceans. However, while ocean modeling and tracking technology have revealed detailed insights into how plastic litter moves and accumulates within oceans, river transport of plastic pollution remains poorly understood.

To help address this knowledge gap, Duncan and colleagues developed a new, low-cost, open-source tracking method that uses reclaimed 500 mL plastic bottles to house custom-designed electronics, allowing the bottles to be tracked via GPS cellular networks and satellite technology. These "bottle tags" mimic plastic beverage bottles, in the hopes that they realistically replicate the path of plastic pollution down a river.

As part of the National Geographic Sea to Source Ganges Expedition, the researchers released 25 bottle tags at various sites along the Ganges River. They successfully tracked several of them through the river and into the Bay of Bengal. They also released three bottles directly into the Bay of Bengal to mimic paths followed by litter once it reaches the sea. The farthest distance traveled by any of the bottles was 2,845 kilometers, which took 94 days.

This study demonstrates that future research could use bottle tags to significantly boost understanding of plastic litter's movement through rivers and into oceans. These devices could reveal new insights into areas where plastic litter is likely to accumulate and periods when large amounts of plastic pollution are moving through the waterways.

The authors also highlight the potential for bottle tags to engage the public -- such as by enabling people to follow the bottles' journeys for themselves -- potentially boosting awareness, discouraging littering, and informing changes to pollution policy.

The authors add: "Our 'message in a bottle' tags show how far and how fast plastic pollution can move. It demonstrates that this is a truly global issue, as a piece of plastic dropped in a river or ocean could soon wash up on the other side of the world."