Deciphering the carrier potential of microplastics aged in freeze-thaw soils: Multiscale insights into mechanisms for...

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Aged microplastics (MPs) are a growing concern due to their potential to transport contaminants.
• The influence of soil freeze-thaw cycles (FTCs) on the contaminant-carrying capacity of MPs is not well understood.

Purpose of the Study:

• To investigate how soil FTCs affect the carrier potential of MPs for antibiotics (ATs).
• To elucidate the mechanisms behind these changes using a combination of experimental and computational methods.

Main Methods:

• Adsorption experiments were conducted using FTC-aged MPs and antibiotics (sulfamethoxazole and enrofloxacin).
• MP characterization included surface morphology, wettability, and surface charge analysis.
• Density functional theory (DFT) and partial least squares structural equation modeling (PLS-SEM) were used to analyze mechanistic pathways.

Main Results:

• FTCs roughened MP surfaces, altered wettability and surface charges, and increased oxygen-containing functional groups (OCFGs).
• Adsorption capacities for SMX and ENR generally increased on FTC-aged MPs, indicating enhanced carrier potential.
• FTC-induced surface morphology changes were the primary driver of increased adsorption, with OCFGs playing a minor, polymer-specific role.

Conclusions:

• Soil FTCs significantly enhance the carrier potential of MPs for antibiotics.
• Surface morphology alterations due to FTCs are key to increased adsorption, impacting contaminant transport in cold regions.
• This study provides a framework for understanding MP-contaminant interactions under environmental stress and highlights the importance of FTCs in climate change contexts.