Nano-titanium dioxide (nano-TiO2) is one of the most universal engineered nano-materials while perfluorooctanesulfonate (PFOS) is a typical new persistent organic pollutant. They are widely used and present in aquatic environment. In this study, a novel semi-static multilayer microcosm was setup to investigate the impacts of nano-TiO2 on PFOS bioaccumulation in fish species [Danio rerio (D. rerio), Ctenopharyngodon idella (C. idella), Hypostomus plecostomus (H. plecostomus)] living in different vertical layers. As a result of aggregation and deposition, the concentration of TiO2 increased from upper to bottom layers in the water column. Concomitantly, due to adsorption of PFOS on the nano-TiO2 particles, PFOS also displayed an increasing trend from upper to bottom layer. Owing to ingestion of the TiO2-PFOS complexes, more PFOS was taken-up by fish. With the aid of intestinal fluid, PFOS was readily released from TiO2 particles and absorbed by fish. As a result, accumulation of PFOS in whole fish was facilitated and the bioaccumulation factors of PFOS in D. rerio, C. idella and H. plecostomus were 3.01, 2.42 and 1.11 times of that in the groups without TiO2. However, TiO2 aggregates were too large to penetrate biological membranes to participate body circulation, and no significant accumulation of TiO2 was observed in fish muscle. The results suggested that the ecological risk of PFOS could be enhanced due to the presence of nano-TiO2 in water.
Keywords: Aggregation; bioaccumulation; carrier; engineered nanoparticles; vertical distribution.