Mechanisms governing the transport of nanoparticles and microplastics in porous media: A review

This work examines the transport mechanisms governing nanoparticles, microplastics, colloids, and biocoloids in porous media, and investigates their roles in environmental sustainability and water resource management. Processes such as aggregation, straining, and co-transport are considered, while a wide range of influencing parameters including particle surface charge, aqueous chemistry, pH, ionic strength, and porous media properties are analyzed for their impact. Published studies reveal that ionic strength and pH significantly impact nanoparticle transport, with higher ionic strength promoting aggregation and retention due to the compression of the electrical double layer. Colloids and viruses are influenced by factors such as attachment-detachment dynamics, and interactions with other particles. Furthermore, the transport of microplastics is governed by their surface properties, hydrophobicity, size, density, and interactions with surrounding organic and inorganic substances. These characteristics play a significant role in determining their migration through porous media. Furthermore, studies have shown that natural organic matter can act as a stabilizing agent for nanoparticles and microplastics by enhancing electrostatic repulsion, thereby increasing mobility in porous media. Conversely, the presence of divalent cations such as calcium can promote aggregation and retention, particularly under conditions of high ionic strength. Τhe importance of physical, chemical, and biological factors on particle transport in subsurface environments was highlighted. Clearly, these findings may help the development or improvement of economically viable and efficient remediation strategies for a wide range of contaminated environmental sites.