Plastic materials are a large class of polymers that have been widely used in daily life due to their unique properties such as impermeability to water and microorganisms, resistance to chemicals, and being light weight with significant mechanical strength. The extensive production and application of plastic materials have resulted in their accumulation in the environment, which has become one of the world’s greatest environmental problems. The plastics can degrade and break down into microplastics (<5 mm) or even nanoplastics (<100 nm). Microplastics may also be intentionally produced for use in industrial and commercial products. Microplastics are widely present in subsurface environments or even in the food chain at various levels, and microplastics and their additives such as Bisphenol A and polybrominated diphenyl ethers are toxic to living organisms. Therefore, investigations on microplastic release from polymer production and application and the fate and transport of microplastics are critical to the accurate assessment of their environmental risks.

To date, the pathways for microplastic release from polymer production and application to subsurface environments have been poorly understood. Once released, their fate and transport are governed by processes such as degradation, aggregation/disaggregation, deposition/release, convection, and dispersion. Knowledge about these processes and accordingly the fate and transport of microplastics are still limited due to the complexities of the subsurface environments. This special issue focuses on recent advances in the pathways for release of microplastics, methods for detection of microplastics, fundamental and quantitative understanding of the interaction, and transport and impact of microplastics in subsurface environments. The issue welcomes original research articles and review papers addressing these topics, demonstrating both theoretical and experimental advances.

Potential topics include but are not limited to the following:

• Pathways for microplastic release
• Methods to detect microplastics in water, soil, and sediments
• Degradation of microplastics
• Aggregation and deposition/release of microplastics
• Transport of microplastics in groundwater and modeling