TiO2 nanoparticles in sediments: Effect on the bioavailability of heavy metals in the freshwater bivalve Corbicula fluminea.

Most studies investigating the influence of TiO2 NPs on heavy metal bioavailability have focused on the aqueous phase; however, few have examined the sediments containing more nanoparticles. Here, we investigated the effects of TiO2 NPs on heavy metal bioavailability in C. fluminea in sediments. The interactions between the TiO2 NPs and metals in sediments, the influence of TiO2 NPs on metals levels in aqueous phase and geochemical speciation were also explored. The results indicated the large adsorption capacity of TiO2 NPs and the strong adsorption affinity to metals caused the metals adsorbed on nanoparticles, which decreased the metals concentrations in water phase. Changes in metal speciation caused by metals in EXC, CAR, and IMO partly transported from sediments to TiO2 NPs during the aging of sediments. Heavy metals contents in C. fluminea tissues were in the order of gill>visceral mass>mantle>foot and increased with the increasing TiO2 NPs contents in sediments. TiO2 NPs enhanced the bioavailability of metals in the speciation of EXC, CAR, and IMO in sediments by the Trojan horse effects. The results can facilitate a more realistic evaluation of the environmental risks of TiO2 NPs to benthic organisms in heavy metal-contaminated sediments.