10.1021/acs.est.6b01215.s001 Mengting Li Mengting Li Zhuanxi Luo Zhuanxi Luo Yameng Yan Yameng Yan Zhenhong Wang Zhenhong Wang Qiaoqiao Chi Qiaoqiao Chi Changzhou Yan Changzhou Yan Baoshan Xing Baoshan Xing Arsenate Accumulation, Distribution, and Toxicity Associated with Titanium Dioxide Nanoparticles in <i>Daphnia magna</i> American Chemical Society 2016 uptake subcellular distribution Arsenate Accumulation BDM accumulation toxicity Daphnia magna signal intensities Daphnia magna Titanium dioxide nanoparticles bioavailability MSF concentration Toxicity Associated consumer products Titanium Dioxide Nanoparticles 2016-08-02 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Arsenate_Accumulation_Distribution_and_Toxicity_Associated_with_Titanium_Dioxide_Nanoparticles_in_i_Daphnia_magna_i_/3578067 Titanium dioxide nanoparticles (nano-TiO<sub>2</sub>) are widely used in consumer products. Nano-TiO<sub>2</sub> dispersion could, however, interact with metals and modify their behavior and bioavailability in aquatic environments. In this study, we characterized and examined arsenate (As­(V)) accumulation, distribution, and toxicity in Daphnia magna in the presence of nano-TiO<sub>2</sub>. Nano-TiO<sub>2</sub> acts as a positive carrier, significantly facilitating D. magna’s ability to uptake As­(V). As nano-TiO<sub>2</sub> concentrations increased from 2 to 20 mg-Ti/L, total <i>As</i> increased by a factor of 2.3 to 9.8 compared to the uptake from the dissolved phase. This is also supported by significant correlations between arsenic (<i>As</i>) and titanium (<i>Ti</i>) signal intensities at concentrations of 2.0 mg-Ti/L nano-TiO<sub>2</sub> (<i>R</i> = 0.676, <i>P</i> < 0.01) and 20.0 mg-Ti/L nano-TiO<sub>2</sub> (<i>R</i> = 0.776, <i>P</i> < 0.01), as determined by LA-ICP-MS. Even though <i>As</i> accumulation increased with increasing nano-TiO<sub>2</sub> concentrations in D. magna, As­(V) toxicity associated with nano-TiO<sub>2</sub> exhibited a dual effect. Compared to the control, the increased <i>As</i> was mainly distributed in BDM (biologically detoxified metal), but <i>Ti</i> was mainly distributed in MSF (metal-sensitive fractions) with increasing nano-TiO<sub>2</sub> levels. Differences in subcellular distribution demonstrated that adsorbed As­(V) carried by nano-TiO<sub>2</sub> could dissociate itself and be transported separately, which results in increased toxicity at higher nano-TiO<sub>2</sub> concentrations. Decreased As­(V) toxicity associated with lower nano-TiO<sub>2</sub> concentrations results from unaffected <i>As</i> levels in MSFs (when compared to the control), where several <i>As</i> components continued to be adsorbed by nano-TiO<sub>2</sub>. Therefore, more attention should be paid to the potential influence of nano-TiO<sub>2</sub> on bioavailability and toxicity of cocontaminants.