Message in a bottle: tracking plastic across oceans

by ZSL on

Have you ever wondered where plastic drink bottles, food containers and everyday plastic items end up once they enter waterways?

As part of the National Geographic Sea to Source Ganges Expedition, ZSL scientists and Arribada engineers converted a satellite tracking tag, originally designed to track sea turtles, into what was possibly the world’s most advanced lemon and lime 500ml water bottle.

These findings were also published in a recent scientific paper, which you can read here.

A floating plastic bottle with an antennae

A special bottle cavity was designed to house both a cellular (mobile phone) and Argos (Argos is the name of the satellite constellation we used, not the shop) satellite transmitter to track plastic water bottles throughout the Ganges River system in India and Bangladesh. Whenever mobile phone networks were available (i.e urban areas), each bottle would transmit its GPS location until they reached the open ocean and mobile phone reception was lost,  at which point the satellite transmitter would take over and transmit the bottle’s location every three hours.

Cross section of a bottle filled with electronic transmitters

Special care was taken to weight and position the bottles to mimic the natural flow of plastic floating on the water’s surface. Our objective was to understand the speed, journey, and ultimate destination of plastic waste, tracking each bottle to understand where plastic may be most likely to accumulate and to identify periods when large amounts of plastic pollution may be released into the environment, such as a potential downpour of rain or inclement weather dislodging trapped plastic on the banks of rivers.


Video of bottle on water

After each bottle was released, we would crowd around our laptops and phones, eagerly awaiting location updates. In India we watched as one bottle left the main river system and made its way into a man-made canal. Using Google Earth we could physically map and track the bottle, looking ahead and taking guesses as to the which path it would take next, which fork in the canal, which weir or barrier would halt it in its tracks. That one bottle ending up travelling over 610km over the course of a month. That’s the equivalent of travelling from Newcastle to Exeter.

In Bangladesh, bottles were released within tributaries of the main river system to track their journey to the open ocean. Several bottles were also dropped by fishermen out at sea. One particular bottle travelled over 2844.6km over the course of 94 days, through a cyclone, wind and rain, before settling off the East coast of India. That’s the equivalent of travelling from London to Gibraltar!


Video of tracked bottle, Bay of Bengal

The hardware used to track each bottle was also entirely "open source", designed by ZSL and Arribada to unlock access to low-cost satellite tracking technologies. This means that researchers and others wishing to track plastics can customise, adapt or incorporate the same technology into their own designs if they so wished to.

Bottle with antennae floating

The expedition also marked the first time an open source Argos transmitter design was used at scale, opening up a door to the tracking of plastics at low-cost and at scale.



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