Keywords: 
• nano-titanium dioxide /
• metallic copper /
• Daphnia magna /
• accumulation /
• crystalline phases

Abstract: Due to its physicochemical property, the nano-titanium dioxide (nTiO₂) is widely utilized. Definitely, the nTiO₂ is released in the aquatic environment during its life cycle (such as production, use and waste). The heavy metals are typical contaminants in aquatic environment, but the influence from nTiO₂ on heavy metal, as well as impact on bioaccumulation of heavy metals remains uncertain. In this study, the Daphnia magna was selected as the case to address the influence from different crystalline phases of nTiO₂ on the bioaccumulation of copper. The results showed that nTiO₂ reduced the concentrations of Cu²⁺ in the test solution. Meanwhile, the copper adsorption capacities of the five crystalline nTiO₂ were different, among which anatase (A-S) was observed with the highest adsorption capacity. This may be explained by the fact that the presence of structural defects and surface hydroxyl groups of A-S can provide more binding sites for Cu²⁺ and correspondingly increase the adsorption capacity of A-S. On another aspect, in our study, the nTiO₂ particles reduced the accumulation of copper in D. magna, since the adsorption of Cu by nTiO₂ probably minimize the bioavailability of free copper ions. Also, as the variability of surface areas, the significant differences for the Cu accumulation per nTiO₂ were observed amongst the five nTiO₂ (P<0.05). In particular, the Cu accumulation for the 4:1 mixture of anatase/rutile (M1) was the highest, whilst that for the A-S was the lowest.