Non-biodegradable microplastics in soils: A brief review and challenge

Area of Science:

• Environmental Science
• Soil Science
• Ecotoxicology

Background:

• Non-biodegradable microplastics (MPs) pose a persistent pollution challenge in soils.
• Recent years have seen increased focus on understanding MP behavior and impacts within terrestrial ecosystems.

Purpose of the Study:

• To quantitatively summarize the sources, migration, distribution, biological effects, degradation, and analytical methods of soil microplastics.
• To identify research trends and future directions in soil MP studies based on a literature review.

Main Methods:

• Systematic literature review of 170 publications from Web of Science (1950-2020).
• Quantitative analysis of data on MP types, sizes, concentrations, colors, geographical distribution, and biological impacts.

Main Results:

• Studies predominantly originate from Asia (60.0%) and Europe (23.3%), focusing on agricultural soils (68.5%).
• Polyethylene, polypropylene, and polystyrene were the most common MPs, typically 20-5000 µm in size, with concentrations ranging from 1000-4000 items kg⁻¹.
• Blue, white, red, and black were the most frequent colors. MPs negatively affected soil animals (100%) and plants (57.9%), altering soil microenvironments and microbial activity.

Conclusions:

• Microplastic pollution significantly impacts soil ecosystems, affecting soil fauna and flora.
• Degradation is influenced by various factors including photooxidation, microbial activity, and MP characteristics.
• Further research is urgently needed to address critical knowledge gaps in soil MP management and remediation.