Transport of engineered nanoparticles in soils and aquifers

Transport and deposition behaviour of engineered nanoparticles (ENPs) in natural aquifers and soil systems is a key determinant of the fate of these materials in environmental systems. A growing number of experimental studies are being conducted worldwide to address transport and deposition of ENPs in porous media (PM). Here we comprehensively review the main mechanisms and factors affecting the mobility of the environmentally important ENPs in natural PM. A variety of different processes including those that promote mobility and result in elution from the PM and those that hinder their mobility and promote ENP retention can influence ENP’s mobility through soil and aquifer media. The most important contributing factors regarding ENP transport in PM include: the physicochemical properties of the ENP, the media, the hydrodynamics of the system, and the background solution characteristics. Results from several studies conducted on the most common and environmentally important ENPs have shown that under natural environmental conditions, different types of ENPs show different transport behaviour in soil and aquifer systems. Additionally, the importance of media matrix and mobile solution factors in governing mobility of ENPs varies from one type of ENP to another.