Influence NTiO₂ On Bioavailability Of Arsenite In Daphnia Magna

Arsenic(As),which extensively existed in the water environment,is a easy-migration and high toxic pollutant,due to its biological accumulation and amplification after transport in food chain.Therefore,the events about As contamination is a hot focus for the present.In recent years,the overuse and potential ecological risk of nTiO2 make it the emerging contaminants.The aqueous nTiO2 would adversly affect the environmental behavior of other pollutants in water in view of its unique physical and chemical properties,thus resulting in the potential ecology risk.At the same time,nTiO2 is also widely used to purify As contaminated water.The ecological risk about adsorption of As by nTiO2 is receiving more and more focus.To better understand and predict the ecological risk of nTiO2 and As(?),the Daphnia magna,being sensitive to the pollutants,is adopted as experimental creature in this study.After the effect of As(II)on nTiO2 is determined,the toxicity of As(II)(the median inhibitory concentration,EC50)and nTiO2 on the accumulation in Daphnia magna,subcellular distribution and distribution of As(?)are evaluated.The results show that nTiO2 decreased the toxicity of As(?)to Daphnia magna.nTiO2 was a carrier to increase the accumulation of As(?)in the fleas body after its adsorption of As(?)and this parts of As are mainly distributed in cell debris of fleas,whereas the amount of As in metal-sensitive fraction(MSF)decreased.The increase of Ti is mainly distributed in biologically detoxified metal(BDM),and the difference of As and Ti indicated a certain amount of desorption of As and nTiO2 in fleas body.On the whole,the As and Ti in fleas body presented a significant correlation,suggested that the As acculuminated in fleas body mostly absorbed on nTiO2.The existence of nTiO2 impeded the metabolism of As by Daphnia magna.Meanwhile,nTiO2 could obviously affect the metabolic behaviour of Daphnia magna to As.According to the subcellular distribution model,the As in MSF and cell debris was mainly metabolized with no existence of nTiO2,but the metabolized As was only from cell debris when nTiO2 existed in system.Comparatively,the metabolized Ti was mainly from MSF,indicating the difference of detoxification mechanism for As and Ti in fleas body and the As accumulated in Daphnia magna was more easily metabolized.The nTiO2 could affect the uptake,accumulation and metabolism of heavy metals by Daphnia magna.Therefore,not only the environmental effect of nTiO2 itself should be given attention,but also more focus on the effect of nTiO2 on other pollutants in the environment and its ecological risk should be paid.