纳米二氧化钛对三价砷在大型蚤体内累积与毒性的影响

nTiO₂（纳米二氧化钛）可作为其吸附污染物的运输载体而影响污染物在生物体内的累积与毒性，为明晰nTiO₂吸附As（Ⅲ）（三价砷）后作为As的运输载体对水生物体内As累积与毒性的影响，以大型蚤（Daphnia magna）为受试生物，通过室内培养试验，研究了不同nTiO₂浓度、As（Ⅲ）不同暴露水平相互作用下蚤体中As与Ti的累积含量、毒性及其潜在作用机制.结果表明，nTiO₂可在30 min内吸附As（Ⅲ）至平衡，其中2、20 mg/L的nTiO₂对75 μg/L As（Ⅲ）的吸附率分别可达31.38%、51.84%，蚤体内As的累积含量分别为对照组的2.9和3.8倍，表明nTiO₂可作为运输载体提高As（Ⅲ）在大型蚤体内的累积；但不同As暴露水平下蚤体As和Ti含量的相关关系表明，nTiO₂作为载体的运输作用可能会因As暴露水平的增加而减弱.另外，nTiO₂虽然作为运输载体提高了As（Ⅲ）在大型蚤体内的累积，但并未增加As（Ⅲ）对大型蚤的毒性.添加2、20 mg/L的nTiO₂后，As（Ⅲ）对大型蚤的24 h IC₅₀（半抑制浓度）分别从0.93 mg/L增至2.53和2.97 mg/L，表明nTiO₂降低了As（Ⅲ）对大型蚤的毒性.研究显示，nTiO₂虽增加了As（Ⅲ）在大型蚤体内的累积，但却降低了As（Ⅲ）对大型蚤的毒性，这有利于对nTiO₂及其复合重金属污染风险的深入认识. 

Influence of Nano-TiO2 on Accumulation and Toxicity of Arsenite in Daphnia magna

Titanium dioxide nanoparticles (nTiO₂) have a higher capacity to adsorb contaminants, which in turn affects the biological accumulation and toxicity. To examine the toxicity and accumulation of arsenite (As(Ⅲ)) in Daphnia magna in the presence of nTiO₂ as transport carriers, the half inhibitory concentration (IC₅₀), and As and Ti accumulated levels were determined for different As concentrations (75 μg/L and IC₅₀) in absence and presence of nTiO₂ at 2 and 20 mg/L. Results showed that nTiO₂ can adsorb As(Ⅲ) to be balanced after 30 min. Specifically, the adsorption rate of As(Ⅲ) was 31.38% and 51.84%, respectively at 2 and 20 mg/L nTiO₂, and the amount of accumulated arsenic in D. magna was 2.9 and 3.8 times the amount accumulated in the control (without nTiO₂). This indicates that nTiO₂ could function as carrier and enhance the accumulation of As(Ⅲ) in D. magna. Meanwhile, the amount of accumulated arsenic in D. magna transported by nTiO₂ might decreased with increasing exposed As(Ⅲ) levels. The observation result is supported by the relationship between arsenic and titanium in D. magna for different As exposed levels. Furthermore, in spite of the increasing arsenic accumulation in D. magna with the nTiO₂ concentration, the toxicity of As(Ⅲ) did not increase. Specifically, the 24 h IC₅₀ of As(Ⅲ) increased from 0.93 mg/L in absence of nTiO₂ to 2.53 and 2.97 mg/L at 2 and 20 mg/L of nTiO₂, respectively, demonstrating that nTiO₂ decreased the toxicity of As(Ⅲ) on D. magna. The study concluded that nTiO₂ can enhance the accumulation of As(Ⅲ) in D. magna, but reduced its toxicity, which will be helpful of providing insights into ecological risks of combined pollution of nTiO₂ with other heavy metals.