Objective:

To quantify the contribution of microplastic coatings from agricultural fertilizers to marine pollution and understand their transport pathways.

Key Findings:

• Beaches near river mouths received less than 0.2% of applied polymer-coated fertilizers (PCFs).
• Beaches connected to paddy fields via drainage canals accumulated up to 28% of applied microplastics.
• Microplastic capsules showed signs of aging, indicating oxidation and photodegradation.

Interpretation:

The study reveals that agricultural practices significantly contribute to marine microplastic pollution, with specific transport pathways influencing accumulation rates on beaches.

Limitations:

• Study focused solely on Japanese beaches, limiting generalizability.
• Only specific types of microplastics were analyzed, potentially overlooking others.

Conclusion:

The findings underscore the need for improved monitoring of agricultural plastics and suggest that the methodology could be applied to other regions to track plastic leakage.