A long-term field experiment confirms the necessity of improving biowaste sorting to decrease coarse microplastic...

Area of Science:

• Environmental Science
• Soil Science
• Ecotoxicology

Background:

• Microplastic (MP) contamination in agroecosystems is a growing concern due to diverse input sources.
• Compost application, vital for circular economy soil management, may introduce MPs.

Purpose of the Study:

• To assess the impact of different urban waste-derived composts on the quantity and type of coarse microplastics (CMP) in soils.
• To evaluate MP accumulation over 22 years in a long-term field experiment.

Main Methods:

• Isolation and characterization of microplastics from composts and amended soils.
• Utilized pyrolysis Gas Chromatography/Mass Spectrometry (GC/MS) for MP analysis.
• Long-term field experiment with bi-annual compost application in France.

Main Results:

• Coarse microplastic concentrations ranged from 26.9 to 417 kg/ha after 22 years, varying by compost type.
• Composts from municipal solid waste showed the highest plastic particle quantities.
• MP accumulation may exceed levels from conventional agricultural practices due to higher application rates.

Conclusions:

• Urban waste composts, particularly from municipal solid waste, are significant sources of soil microplastic contamination.
• Urgent need to limit plastic use, improve biowaste sorting, and incorporate MP considerations into organic amendment regulations.
• Further research is required to understand the long-term effects of substantial MP inputs on soil functioning, despite no current observed bio-physico-chemical impacts.