Experimental investigation of stability and transport of TiO₂ nanoparticles in real soil columns

This study aims to explore the stability of TiO₂ nanoparticles in soil suspensions and their transport behavior through real soil columns. A classical filtration theory was used to describe transport behaviors of TiO₂ nanoparticles. The results illustrated that TiO₂ nanoparticles could remain suspended in soil suspensions even after settling for 8 d. At comparatively higher dissolved organic matter (DOM) and low ionic strength (IS) containing soils, considerable portion of TiO₂ nanoparticles (32–34%) suspensions was observed in sedimentation experiments after 24 h. In addition, zeta potential (ZP) of soil suspensions as a function of soil pH, suggested that ZP played significant role than soil pH. In soils containing comparatively higher DOM, a considerable portion of TiO₂ nanoparticles (51.8–90.6%) readily passed through soils columns, while TiO₂ nanoparticles were retained by soils with comparatively higher ISs. The estimated travel distances of TiO₂ nanoparticles in soils ranged from 45.03 to 625.86 cm, representing potential environmental risk of TiO₂ nanoparticles to the environment.