Food Chain Transfer Of NANO-TiO₂ In Aquatic Ecosystem

With the rapid development of nanoscience and nanotechnology,more and more nanomaterials entered people's daily life.Nanomaterials may release into the water environment inevitably through multiple ways which would affect the aquatic ecosystem.It is crucial to carry out systematic study and analyzes its ecological effects for assessing environmental risks of nanomaterials.A lot of papers have been published about biological safety of nanomaterials,but most focused primarily on aqueous-phase exposures to single test organism and neglected toxic effects owing to dietary intake of food-associated nanoparticles.These limit the whole understanding on biological effects of nanomaterial in water environment.In this paper,we established the food chain composed by different trophic levels to explore the food chain transfer mechanism of nano-TiO₂ in the lab conditions.Nano-TiO₂ could transfer along the the food chain from Scenedesmus obliquus to Daphnia magna;the surfactant sodium dodecyl benzene sulfonate?SDBS?could improve the stability of the nano-TiO₂ in the water,increase nano-TiO₂ content in Scenedesmus oblique body and enhance nano-TiO₂ accumulation in Daphnia magna along the food chain transfer.Nano-TiO₂ could transfer along the the food chain from Daphnia magna to Japanese Medaka;the accumulation in Daphnia magna was as high as 1.40×104 mg/kg after exposed by nano-TiO₂ for 48h;TiO₂ could be transferred into Japanese Medaka body along the food chain and could penetrate heart-blood,blood-brain barrier,then accumulated in the heart,liver,brain tissues,they also could Pass on to the offspring through the gonads and eggs;the food chain transmission had no effects on reproductive behavior of Japanese Medaka,such as spawning,egg hatchability;the histopathological lesion was also not observed.Nano-TiO₂ could also transfer along the the food chain from Artemia salina to Zebrafish;compared to the dietary intake,Zebrafish were exposed to equivalent dose of TiO₂ nanoparticles by aqueous exposure,nano-TiO₂ distribution in zebrafish tissues was different under the two exposure ways:TiO₂ content in heart was significantly higher than those in liver,brain and gill,while the gill showed higher level of TiO₂ nanoparticles contents in queous treatment group;in the two different ways,nano-TiO₂ showed different histopathological injury;:cavitation and oedema of heart cells were more serious for fish in dietry exposer group,while gill filament bend,fall off were more for fish in water exposure group.The research on toxicity of nano-materials in the food webs is still in beginning stage now.So it is very necessary to establishe the food chain composed by primary producers and different consumers and systematically study the food chain transmission and the biological effects.