# [PERSON]: Extreme Plastic Pollution Pathways in Riparian Waterways
## 6 Conclusions  
This study investigated the movement and retention dynamics of a single-use plastic tracker in the tidal waters of the Saigon River, shedding light on the broader challenge of plastic pollution in riparian ecosystems. Using a combination of low-cost GPS-enabled tracking, accelerometer, and gyroscopic sensors and hidden Markov model (HMM) analysis, we provided a detailed understanding of the tracker's behavior, including speed, resting states, and responses to external influences. The results revealed the critical role of tidal dynamics in governing the slow average speeds and frequent resting periods of floating debris. A notable speed spike event, attributed to vessel-induced turbulence, demonstrated the significant impact of anthropogenic activities on plastic transport. The HMM analysis further provided insights into transitions between resting and transit states, emphasizing the potential for retention zones in tidal waterways to act as semi-permanent repositories supporting efficient collection of plastic waste. By illuminating the transportation of single-use plastic bottles through the riparian waterways of Ho Chi Minh City, this study contributes to collective efforts to understand and mitigate plastic pollution, supporting the preservation of aquatic ecosystems. The findings align with prior research on plastic retention in estuaries, underscoring the intricate interplay between tidal cycles, river discharge, and human activity in influencing plastic transport. This study advances scientific understanding by providing a structured approach to tracking and evaluating plastic waste transport in tidal river systems. By integrating GPS tracking with empirical data analysis, it establishes a reproducible methodology for assessing plastic retention patterns, informing cleanup strategies, and refining plastic pollution models. The contributions of this work are threefold: it demonstrates the practical application of GPS-enabled tracking for monitoring plastic waste, highlights the importance of integrating tidal dynamics into plastic transport models, and offers an innovative approach to analyzing movement patterns using HMMs. Future research could build upon this study by deploying similar trackers across diverse river systems, both tidal and non-tidal, to explore variability in transport dynamics. Investigating how different plastic types, with varying buoyancy and rigidity, interact with environmental forces could provide further insights into plastic behavior. Additionally, identifying and prioritizing retention zones and collection points along waterways like the Saigon River could enhance the efficiency of cleanup efforts and contribute to long-term pollution mitigation strategies. Conceptualization: P.C. and A.M.; methodology, P.C. ; software, P.C. ; validation, P.C. and A.M.; formal analysis, P.C. ; investigation, P.C. ; resources, P.C. ; data curation, P.C. ; writing--original draft preparation, P.C. and A.M.; writing--review and editing, P.C. and A.M.; visualization, P.C. ; supervision, A.M.; project administration, P.C. and A.M.; funding acquisition, A.M. and P.C. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data presented in this study are available on request from the first author. The data are not publicly available due to the costs and resources involved in making the data set legible enough to be publicly accessible. We will make the data publicly available in the next iteration of this project. Acknowledgments: The authors acknowledge internal funding support from the School of Future Environments (SoFE) and Faculty of Design and Creative Technology (DCT) at Auckland University of Technology (AUT). Conflicts of Interest: The authors declare no conflicts of interest. References  
* [PERSON] et al.