Pore-Scale Insights into Microplastic Fiber Transport and Retention in Porous Media

Agricultural soils have been identified as sinks for microplastic fibers (MPFs); however, little is known about their transport and behavior in these environments. This study tracked polypropylene microfibers (20-150 μm) in a microfluidic cell (dimensions) to better understand their potential movement and entrapment in soil-like porous media. The effects of MPF dimensions and elasticity on their mobility and retention were examined, along with how fiber trapping influenced the overall flow dynamics of the system. Results showed that fiber transport depends strongly on size and flexibility: fibers longer than 50 μm were highly retained, while shorter fibers followed preferential flow paths and experienced higher flow velocities. The retention mechanisms of fibers differed from those of spherical particles, and even a small number of trapped fibers were found to alter pore-scale flow patterns. In addition, several properties were identified as crucial for improving models and predictions of MPF behavior in porous systems. These findings provide insight into the dynamics of fiber entrapment and the complexities of nonspherical particle transport in porous media, emphasizing the need for further research in this field.