Investigating the Migration and Transport of Micro/Nano-plastics in Soil Columns: A Systematic Review

Plastics have emerged as a pervasive pollutant in terrestrial ecosystems, posing significant ecological risks and potential threats to human health. The pervasive nature of these plastics and their longevity leave a legacy of micro/nano-plastics (MnPs), which contaminate soil systems and drinking water resources. In recent years, a growing number of experimental studies have investigated the transport behavior of MnPs; however, comprehensive review articles focusing specifically on MnPs transport in soil- and groundwater-based column systems remain limited. The present article aims to systematically compile the existing literature on the migration and mass distribution of MnPs of varying sizes in soil, under the influence of key physicochemical parameters such as pH, ionic strength, surfactants, and solution chemistry. In addition, this review examines the effects of co-contaminants, flow direction, hydraulic forcing, and experimental setup variations on the transport and retention of MnPs within soil columns. The outcomes of the reviewed studies are evaluated through their impacts on breakthrough curves and retention profiles, providing insights into MnPs mobility and accumulation mechanisms. Both labelled and non-labelled MnPs transport studies conducted in column experiments are considered, with particular emphasis on the detection and quantification techniques employed. These include fluorescence-based methods, particle counting approaches (manual and automated), electron microscopy (SEM/TEM), and light scattering techniques such as dynamic light scattering. Finally, the performance of these detection methods is critically compared in terms of sensitivity, accuracy, and applicability, and key methodological limitations and future research challenges in MnPs transport studies are discussed.