An Overview of Microplastic Contamination in Groundwater: Sources, Transport Pathways, and Environmental Implications

This review investigates the growing concern of microplastic (MP) contamination in groundwater systems, an area that has received relatively limited attention compared to surface water environments. Drawing from a comprehensive review of recent literature, the study identifies key sources of MPs in groundwater, including landfills, septic systems, agricultural runoff, and wastewater infiltration. Polyethylene (PE) and polypropylene (PP) were consistently found to be the most prevalent polymer types. The paper synthesizes evidence on MP transport mechanisms—such as movement through the hyporheic zone, soil macropores, and karst aquifers—highlighting the role of hydraulic conductivity, seasonal flow variations, and soil structure. Findings also emphasize the influence of particle characteristics (e.g., size, shape, density) on mobility and persistence in subsurface environments. The review further discusses analytical challenges in detecting MPs at small scales and underscores health and ecological risks, such as bioaccumulation, heavy metal adsorption, and disruption to groundwater fauna. The study calls for standardized sampling methods, increased monitoring, and integrated management strategies to mitigate MP pollution in groundwater. These insights are critical for informing policy decisions and advancing research on this emerging threat to freshwater sustainability.