Microplastics alter soil structural stability as quantified by high-energy moisture characteristics.

Area of Science:

• Environmental Science
• Soil Science
• Materials Science

Background:

• Microplastics (MiPs) are emerging soil contaminants with potential to alter soil structural stability.
• The influence of MiPs on soil properties depends on their characteristics like chemistry, concentration, size, and degradation.
• Understanding these impacts is crucial for soil health and ecosystem functioning.

Purpose of the Study:

• To quantify the effects of microplastic properties on soil structural stability using high-energy moisture characteristics (HEMC).
• To investigate how polypropylene (PP) and polyethylene (PE) microplastics influence soil pore distribution and water retention.
• To assess the impact of microplastic concentration and size on soil hydraulic properties.

Main Methods:

• Soil samples contaminated with varying concentrations and sizes of PP and PE microplastics were analyzed.
• High-energy moisture characteristics (HEMC) were used to measure water retention at matric suctions from 0 to 50 hPa.
• HEMC data were modeled to quantify changes in drainable pore volume (VDP) and modal matric suction (h_modal).

Main Results:

• Increased microplastic concentrations (2% and 7%) significantly increased the volume of drainable pores (VDP).
• Larger microplastic fibers (3-5 mm) at lower concentrations (0.5-1%) showed higher VDP compared to smaller fibers (1.6 mm).
• Both PE and PP microplastics increased modal matric suction (h_modal), with effects more pronounced under fast wetting conditions.

Conclusions:

• Microplastics detrimentally impact soil aggregates and pores, significantly altering HEMC parameters and soil hydraulic properties.
• MiPs affect soil's water retention and supply capabilities, compromising overall soil health and productivity.
• Characterizing microplastic impacts on soil structure is essential for developing strategies to mitigate pollution effects.