Department of Environmental Science and Engineering, Beihang University, Beijing 100083, People's Republic of China.
Environ Sci Technol. 2012 Jan 3;46(1):469-76. doi: 10.1021/es202110d. Epub 2011 Dec 1.
Titanium dioxide nanoparticles (nano-TiO(2)) are now widely applied in consumer products, and the dispersion of nano-TiO(2) may adsorb metals and modify their behavior and bioavailability in the aquatic environment. In the present study, the aqueous uptake, dietary assimilation efficiency (AE), and efflux rate constant (k(e)) of two toxic metals (cadmium-Cd, and zinc-Zn) adsorbed on nano-TiO(2) in a freshwater zooplankton Daphnia magna were quantified. The biokinetics was then compared to daphnids that were exposed only to dissolved metals as controls. The aqueous uptake of Cd and Zn involved an initial rapid uptake and then an apparent saturation, and the uptake of metals was accompanied by an ingestion of nano-TiO(2). The AEs of Cd and Zn adsorbed on nano-TiO(2) were 24.6 ± 2.4-44.5 ± 3.7% and 30.4 ± 3.4-51.8 ± 5.0%, respectively, and decreased with increasing concentrations of nano-TiO(2). Furthermore, the difference between the AEs of Cd and Zn indicated that the desorption of Cd and Zn from nano-TiO(2) may have occurred within the gut of daphnids. With the use of algae as carrier, the AEs of Cd and Zn adsorbed on nano-TiO(2) were significantly higher than those of Cd and Zn directly from nano-TiO(2). The efflux rate constants of Cd and Zn adsorbed on nano-TiO(2) in the zooplankton were significantly lower than those of Cd and Zn not adsorbed on nano-TiO(2). Our study shows that the uptake and retention of toxic metals is enhanced when they are adsorbed on nano-TiO(2), and suggests more attention be paid to the potential influences of nano-TiO(2) on the bioavailability and toxicity of other contaminants.
二氧化钛纳米粒子（纳米 TiO(2)）目前广泛应用于消费产品，纳米 TiO(2)的分散可能会吸附金属，并改变它们在水生环境中的行为和生物利用度。本研究定量研究了两种有毒金属（镉 Cd 和锌 Zn）在淡水浮游动物大型溞（Daphnia magna）中吸附在纳米 TiO(2)上的水相摄取、膳食同化效率（AE）和外排率常数（k(e)）。然后将生物动力学与仅暴露于溶解金属的对照组溞进行了比较。Cd 和 Zn 的水相摄取涉及初始快速摄取，然后是明显的饱和，并且金属的摄取伴随着纳米 TiO(2)的摄入。吸附在纳米 TiO(2)上的 Cd 和 Zn 的 AE 分别为 24.6±2.4-44.5±3.7%和 30.4±3.4-51.8±5.0%，并随纳米 TiO(2)浓度的增加而降低。此外，Cd 和 Zn 的 AE 之间的差异表明，Cd 和 Zn 可能从纳米 TiO(2)上解吸发生在溞的肠道内。利用藻类作为载体，吸附在纳米 TiO(2)上的 Cd 和 Zn 的 AE 明显高于直接从纳米 TiO(2)上的 Cd 和 Zn。浮游动物中吸附在纳米 TiO(2)上的 Cd 和 Zn 的外排率常数明显低于未吸附在纳米 TiO(2)上的 Cd 和 Zn。本研究表明，当有毒金属被吸附在纳米 TiO(2)上时，它们的摄取和保留会增强，并表明需要更多地关注纳米 TiO(2)对其他污染物生物利用度和毒性的潜在影响。
