State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province 210093, China.
Ecotoxicol Environ Saf. 2012 Nov;85:44-51. doi: 10.1016/j.ecoenv.2012.08.024. Epub 2012 Sep 10.
Toxicity of engineered nanoparticles has received extensive attention in recent years. However, nanoparticles always co-exist with other pollutants in natural environment. Whether there are any interactions between these classical pollutants and nanoparticles; and how these interactions may influence the environmental behavior, effects and fate of each other remain largely unclear. For this purpose, effects of bare titanium dioxide engineered nanoparticles (TiO(2)-NP) and their bulk counterpart (TiO(2)-BC) on Cd(2+) bioavailability and toxicity to the green alga Chlamydomonas reinhardtii were examined in the present study. We first investigated the kinetics and equilibrium isotherm of Cd(2+) adsorption on both particles in the algal culture medium. Pseudo-first-order adsorption kinetics was observed with equilibrium rate constant ranging from 0.19 to 0.33min(-1). Increase in Cd(2+) adsorption with its ambient concentration at equilibrium followed a single Langmuir isotherm for different concentrations of TiO(2). Furthermore, surface-area-based Cd(2+) adsorption by TiO(2)-BC was higher than that by TiO(2)-NP in most Cd(2+) concentration treatments suggesting that particle size was not the only cause for different adsorption. Both forms of TiO(2) could alleviate Cd(2+) inhibitive effects on C. reinhardtii. However, Cd(2+) toxicity and its bioaccumulation were comparable as long as its free ion concentration in ambient toxicity media was similar regardless the particle size and concentration of TiO(2). There was no TiO(2) inside the algal cells either. Therefore, it was Cd(2+) adsorption by TiO(2) which decreased its ambient free ion concentration and further its intracellular accumulation as well as toxicity.
近年来，工程纳米粒子的毒性受到了广泛关注。然而，纳米粒子在自然环境中总是与其他污染物共存。这些经典污染物与纳米粒子之间是否存在相互作用，以及这些相互作用如何影响彼此的环境行为、效应和归宿，在很大程度上仍不清楚。为此，本研究考察了裸露的二氧化钛工程纳米粒子（TiO(2)-NP）及其体相对照物（TiO(2)-BC）对绿藻莱茵衣藻的 Cd(2+)生物可利用性和毒性的影响。我们首先研究了 Cd(2+)在藻类培养液中吸附到两种颗粒上的动力学和平衡等温线。观察到准一级吸附动力学，平衡速率常数范围为 0.19 至 0.33min(-1)。在不同 TiO(2)浓度下，Cd(2+)吸附量随环境浓度的增加而增加，符合单 Langmuir 等温线。此外，基于表面积的 TiO(2)-BC 对 Cd(2+)的吸附量在大多数 Cd(2+)浓度处理中均高于 TiO(2)-NP，这表明粒径不是导致吸附量不同的唯一原因。两种形式的 TiO(2)都可以减轻 Cd(2+)对 C. reinhardtii 的抑制作用。然而，只要环境毒性介质中的游离离子浓度相似，无论 TiO(2)的粒径和浓度如何，Cd(2+)的毒性及其生物累积都相当。藻类细胞内也没有 TiO(2)。因此，是 TiO(2)对 Cd(2+)的吸附降低了其环境游离离子浓度，进而降低了其细胞内累积和毒性。
