# [PERSON]: Extreme Plastic Pollution Pathways in Riparian Waterways
## 5 Discussion
### Findings and Interpretations  
The tracker's journey provided insights into the behavior of plastic waste in tidal environments, characterized by slow movement and frequent resting states. The tracker's low average speed of 0.50 m/s and 78 distinct resting periods, with an average duration of 2.40 min, underscore the significant role of tidal reversals and interactions with riverbanks in immobilizing plastic waste [2; 3; 21]. The final resting period, spanning 30 h in a tidal mud bank, highlights how specific environmental features can act as long-term retention zones, preventing plastic from reaching open waters [16]. These observations align with prior studies emphasizing the retention potential of tidal systems, adding empirical evidence to support their role as semi-permanent repositories for plastic debris [2; 3; 16; 21]. The prolonged resting period highlights the capacity of natural features, such as mud banks, to trap floating debris. This retention has important implications for understanding plastic waste accumulation in riparian systems and for designing targeted waste removal interventions. The persistence of the tracker in this state underscores the need to monitor such zones as key sites for intervention strategies, including the installation of plastic capture systems. A notable anomaly in the data was the speed spike event, where the tracker experienced a sudden acceleration to 2.55 m/s, far exceeding its average velocity of 0.50 m/s. This event, supported by gyroscopic and accelerometer readings, revealed intense rotational dynamics and sudden shifts in speed and orientation, indicating a momentarily chaotic environment influenced by external forces. Analysis of the gyroscopic data showed rapid movements consistent with what would occur during interactions with large-scale vessel wakes or high-turbulence zones. This dynamic behavior aligns with the expected effects of passing ships in busy commercial waterways, where wake turbulence can displace floating objects with significant force. This dynamic behavior aligns with the expected effects of passing ships in heavily trafficked commercial waterways, where wake disturbance can displace floating objects with significant force. The Saigon River, as a vital economic artery for Ho Chi Minh City [17; 24], underscores this contrast of scale and activity. Navigated daily by over 2500 large commercial vessels, including post-Panamax ships, the waterway is highly dynamic and congested [16]. These massive vessels, essential for Vietnam's economic development, produce significant wake turbulence that interacts with the comparatively minute scale of a single-use plastic bottle tracker. This stark contrast between the scale of shipping infrastructure and the vulnerability of floating plastic debris highlights the disproportionate impact of human activities on the movement of waste in urban waterways. The bustling traffic amplifies the complexity of plastic transport as human-engineered forces interact with natural tidal dynamics to create unpredictable transport patterns, further emphasizing the Saigon River's role as both a transport pathway and retention zone for plastic debris. The geospatial context of the speed spike event further supports this reading, as the anomaly occurred near two heavily trafficked commercial docks situated along the Saigon River's main channel. This zone, characterized by constant vessel movement and industrial activity, highlights the significant role human interventions play in disrupting the natural transport patterns of plastic waste. Large vessels not only generate wake turbulence but also create secondary effects, such as rapid water displacement, increased flow velocities, and pressure changes, all of which can contribute to sudden, erratic movements of floating debris [14]. This underscores the unpredictable nature of plastic transport in regions where human and natural dynamics intersect.