Plastic-Rock Complexes as Hotspots for Microplastic Generation.

Area of Science:

• Environmental Science
• Geology
• Materials Science

Background:

• Discarded plastics and microplastics (MPs) are pervasive environmental contaminants.
• Plastic debris is increasingly recognized as a marker of the Anthropocene.
• Understanding novel pathways of MP generation is crucial for environmental risk assessment.

Purpose of the Study:

• To report the discovery of a new environmental material: plastic-rock complexes.
• To investigate the role of these complexes in microplastic generation.
• To quantify the rate of microplastic release from these complexes.

Main Methods:

• Identification and characterization of plastic-rock complexes formed after flooding events.
• Laboratory-based wet-dry cycling tests on low-density polyethylene (LDPE)- and polypropylene (PP)-rock complexes.
• Quantification of microplastic generation rates using established methods.

Main Results:

• Plastic-rock complexes composed of LDPE/PP films and quartz-dominated matrices were identified.
• Wet-dry cycling generated exceptionally high rates of microplastic release (1.03-1.28 × 10⁸ items·m^-2 over 10 cycles).
• Microplastic generation rates were 4-5 orders of magnitude higher than in landfills and significantly higher than in marine environments.

Conclusions:

• Plastic-rock complexes represent a novel pathway for anthropogenic waste entering geological cycles.
• These complexes act as significant hotspots for microplastic pollution.
• Climate change-induced events like flooding may exacerbate this pollution pathway, posing ecological risks.