Effects of titania nanoparticles on phosphorus fractions and its release in resuspended sediments under UV irradiation

Little is known about the effects of nano-TiO2 on the transformation and transport of phosphorus (P) in resuspended sediments. Chemical sequential extraction was used to investigate P fractions and its release in resuspended sediments under the influence of nano-TiO2 and UV irradiation. The results showed that the contents of sediment P in all fractions decreased with increasing nano-TiO2 concentration in UV irradiation, while increased in the dark controls. Furthermore, P release from all fractions was greater in UV irradiation than in the controls. Elevated concentrations (10-50 mg L-1) of nano-TiO2 in UV irradiation significantly facilitated the release of P from organic and Fe oxide fractions, possibly resulting from the partial photo-degradation of organic matter and photochemical transformation of Fe oxides. Apparently, nano-TiO2 in UV irradiation did not immobilize the loosely sorbed P and reductant soluble P release from the resuspended sediments, possible because (1) some of P released from those fractions were refurnished by the P released from OM; (2) photocatalysis of nano-TiO2 reduced binding capacity of the resuspended sediments. Our results suggest that the photocatalysis of nano-TiO2 may offer the potential to regulate the transformation and transport of sediment P in the aquatic environment.