Combined effects of titanium dioxide and humic acid on the bioaccumulation of cadmium in Zebrafish

The combined effects of titanium dioxide (TiO2) nanoparticles and humic acid (HA) on the bioaccumulation of cadmium (Cd) in Zebrafish were investigated. Experimental data on the equilibrium Cd bioaccumulation suggest that only the dissolved Cd effectively contributed to Cd bioaccumulation in HA solutions whereas both the dissolved and TiO2 associated Cd were accumulated in TiO2 or the mixture of HA and TiO2 solutions, due likely to the additional intestine uptake of the TiO2-bound Cd. The equilibrium Cd bioaccumulation in the mixed system was comparable to that in the corresponding HA solutions, and significantly lower than that in the corresponding TiO2 solutions (n = 3, p < 0.05). The presence of either HA or TiO2 (5–20 mg L−1) in water slightly increased the uptake rate constants of Cd bioaccumulation whereas combining HA and TiO2 reduced the uptake rate constants.

Both titanium dioxide (TiO2) and mixtures of TiO2 and humic acid (HA) facilitate the bioaccumulation of Cd in Zebrafish. The asterisk denotes significant differences of the values in solution with and without matrices. Significant differences between the test systems with 5 mg L−1 HA, 5 mg L−1 TiO2 and [5 + 5] mg L−1 HA and TiO2 as well as 10 mg L−1 HA, 10 mg L−1 TiO2 and [10 + 10] mg L−1 HA and TiO2 are indicated by different letters. C and C0 represent dissolved Cd concentrations (a) and Cd bioaccumulation (b) in solutions with and without matrices, respectively.Figure optionsDownload as PowerPoint slideHighlights
► TiO2 facilitated the bioaccumulation of Cd in Zebrafish.
► TiO2 associated Cd added to Cd bioaccumulation in TiO2 or mixtures of HA and TiO2.
► Coexistence with HA reduced Cd bioaccumulation in TiO2 solutions.
► HA or TiO2 increased the bioaccumulation rate constants whereas mixtures not.