The Shapes and Sizes of Macroplastics and Other Litter in Rivers

Area of Science:

• Environmental Science
• Ecology
• Materials Science

Background:

• Limited data exists on the physical and geometric properties of river macrolitter.
• Understanding these properties is crucial for effective pollution management and mitigation.

Purpose of the Study:

• To reveal the physical-structural relationships of river macrolitter.
• To identify the most persistent river litter categories and their geometric characteristics.

Main Methods:

• Analysis of a detailed dataset of 14,052 riverbank items, including dimensions (L1, L2, L3), mass, volume, and density.
• Mapping these properties onto a larger dataset of 239,290 River-OSPAR items from 22 global sites.
• Utilizing multivariate statistics and kernel density estimations to identify persistent litter categories and their geometries.

Main Results:

• 25 River-OSPAR categories constitute 80% of all river and riverbank litter.
• Soft plastic pieces/films and food packaging are the most abundant litter types.
• Flat, 2D-shaped macrolitter (L1 between 1-10 cm, L3/L2 ratio <0.4) are the most persistent.

Conclusions:

• The physical and geometric properties of macrolitter significantly influence its persistence in riverine environments.
• Findings can inform plastic transport models, monitoring protocols, and the design of river cleanup technologies.
• Prioritizing flat, 2D-shaped plastics in cleanup efforts is recommended.