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Understanding how plastics flow from land to sea is essential for solving the growing problem of plastic pollution. Rivers play a key role as major transport pathways, and accurate monitoring technologies are urgently needed to achieve the Osaka Blue Ocean Vision declared at the 2019 G20 Osaka Summit, which aims to reduce additional marine plastic pollution to zero by 2050.

Newly developed software to detect and track river plastics integrates three key technologies:

• Template matching for measuring river surface flow velocity;
• YOLOv8 for detecting and classifying plastic objects; and
• Deep SORT for tracking their movements.

The work is in the journal Water Research.

By combining these techniques, the system automatically quantifies the transport volume of floating plastics in rivers. This innovation enables continuous, simultaneous monitoring at multiple sites, including under challenging conditions such as floods—something that was previously difficult and dangerous to perform manually. In addition, because the software can distinguish plastics by type, it allows for more direct evaluation of source reduction measures and the effectiveness of waste management policies.

Moving forward, the research team plans to incorporate this software into the Plastic River Monitoring System (PRIMOS), jointly developed with Yachiyo Engineering Co., Ltd., to promote its application in real river environments.

Through this effort, the team aims to:

• Accurately estimate the amount of plastic flowing from land to sea
• Clarify the transport processes across entire river basins
• Support the formulation and evaluation of evidence-based environmental policies.

This initiative is expected to make a significant contribution to international efforts toward a sustainable and pollution-free society.