Message in a bottle: Open source technology to track the movement of plastic pollution

Abstract

Rivers worldwide are now acting as major transport pathways for plastic pollution and discharge large quantities of waste into the ocean. Previous oceanographic modelling and current drifter data have been used to predict the movement and accumulation of plastic pollution in the marine environment, but our understanding of the transport and fate through riparian systems is still largely unknown. Here we undertook a proof of concept study by applying open source tracking technology (both GPS (Global Positing System) cellular networks and satellite technology), which have been successfully used in many animal movement studies, to track the movements of individual plastic litter items (500 ml PET (polyethylene terephthalate) drinks bottles) through the Ganges River system (known as the Ganga in India and the Padma and Meghna in Bangladesh, hereafter known as the Ganges) and the Bay of Bengal. Deployed tags were successfully tracked through the Ganges river system and into the Bay of Bengal marine system. The "bottle tags" were designed and built (e.g. shape, size, buoyancy) to replicate true movement patterns of a plastic bottle. The maximum distance tracked to date is 2845 km over a period of 94 days. We discuss lessons learnt from the development of these plastic litter tags, and outline how the potential widespread use of this open source technology has the ability to significantly increase understanding of the location of accumulation areas and the timing of large inputs of plastic pollution into the aquatic system. Furthermore, "bottle tags" may act as a powerful tool for stimulating social behaviour change, informing science-based policy, and as valuable educational outreach tools for public awareness.

Fig 1. Maps of bottle tag movements a) Expedition site map of the 10 sites in the Sea to Source Expedition; the first three sites in Bangladesh ((1) Bhola, (2) Chandpur and (3) Rajbari) and 7 remaining in India ((4) Sahibganj, (5) Patna, (6) Varanasi, (7) Kannauj, (8) Anupshahar, (9) Rishikesh, (10) Harsil) b) Phase A bottle A7 (pink) deployed in (8) Anupshahar c) Phase B bottle B9 (blue) deployed in (2) Chandpur d) Phase B bottle tags deployed at sea in the Bay of Bengal (B1 (red), B2 (orange)) and (1) Bhola (B4 (yellow)).

Star = deployment location, Black diamond = end location, Green triangle = expedition site location. Maps throughout this research article were created using ArcGIS^® software by Esri. ArcGIS^® and ArcMap^™ are the intellectual property of Esri and are used herein under license. Copyright © Esri. All rights reserved. For more information about Esri^® software, please visit www.esri.com. Contains information from OpenStreetMap and OpenStreetMap Foundation, which is made available under the Open Database License.

Fig 2. The shape and profile of the bottle tag.

a) A transparent schematic showing the seating of batteries and placement of electronics inside the bottle’s enclosure; a = Horizon GPS board, b = Cellular antenna, c = Cellular or Argos satellite board, d = CNC-milled enclosure, e = Battery board, f = O-ring seal. b) Transparent top, side, bottom view and orientation of batteries inside the bottle’s internal cavity; g = Positioning of AA lithium batteries c) Phase A GSM bottle tags d) observed PET bottles in river bank Ganges River e) Phase B satellite bottle tag after deployment.

Fig 3. Displacement plots; bottle straight distance displacement movements over time tracked.

Star = release. Bottle = tracking finished. a), b), c) & d) river deployments and e) & f) at sea deployments.