Lead accumulation (adsorption and absorption) by the freshwater bivalve Corbicula fluminea in sediments contaminated by TiO2 nanoparticles

With the increasing production and applications of TiO 2 nanoparticles (NPs), their presence in aquatic environments, especially in sediments, will inevitably increase over time. Most studies investigating the influence of TiO 2 NPs on the bioaccumulation of co-existing contaminants have focused on the aqueous phase; however, few have examined the sediment phase, which contains more TiO 2 NPs and contaminants. We investigated the effects of TiO 2 NPs on Pb accumulation by Corbicula fluminea in sediments, and explored extracellular and intracellular Pb concentrations in the various soft tissues of the bivalve. Pb was spiked with 50 mg/kg in sediment and TiO 2 NPs/sediments ratios were within the range 0.2–3.0%. The results showed that TiO 2 NPs presented larger adsorption capacity and affinity to Pb ions than the sediments. In addition, the large adsorption capacity of TiO 2 NPs and the strong adsorption affinity to Pb ions caused part of the Pb ions released from sediments to aqueous phase were re-adsorbed by TiO 2 NPs in sediments. The concentration of TiO 2 NPs in C. fluminea tissues significantly increased with increasing TiO 2 NP content in sediments, following the order: gill > mantle > foot > visceral mass, which differed from the results found in the aqueous phase. In addition, the proportions of extracellular and intracellular Pb concentrations changed significantly in all the tissues as a result of TiO 2 NP contamination of sediments. TiO 2 NPs promote increased extracellular Pb in foot, mantle, and gill tissues, and increased intracellular Pb in the visceral mass. These results may be beneficial to more scientifically evaluate and predict the environmental risks of TiO 2 NPs to benthic organisms in sediments contaminated by heavy metals.