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 8d. 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 24h. 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 625.86cm, representing potential environmental risk of TiO2 nanoparticles to the environment.