Nanoparticles (NPs) are inevitably released into the aquatic environment for being widely used and may affect the toxicity of other contaminants already present in the environment, such as trace metals. However, the effects of NPs on the ecotoxicity of cadmium (Cd), a common environmental trace metal pollutant, are not well explored. In this study, effects of four widely used NPs TiO₂ (n-TiO₂), SiO₂ (n-SiO₂), Ag (n-Ag) and CdTe/CdS core/shell quantum dots (QD) on the toxicity of Cd to the freshwater algae Chlamydomonas reinhardtii were assessed respectively. Cd reduced the algae biomass, impaired the photosynthetic activities, and led to intracellular oxidative stress of algae. At non-toxic concentrations, both n-TiO₂ (100 mg L⁻¹) and n-SiO₂ (400 mg L⁻¹) attenuated the toxicity of Cd towards the algae for reducing the intracellular Cd contents, and the former was more pronounced. QD (0.5 mg L⁻¹) increased the toxicity of Cd to algae, but n-Ag (0.2 mg L⁻¹) had no significant influence on the Cd toxicity to algae. The microscopic observations on the ultrastructure of algae cells presented the same phenomena and n-TiO₂, n-SiO₂ aggregations were clearly observed outside the cell wall. Furthermore, the regulation of NPs to the Cd toxicity towards algae was related to the intracellular nitric oxide (NO), an important signaling molecule, rather than the phototaxis of algae. Above all, this study provided a basic understanding about the difference in joint toxicity of different kinds of NPs and Cd to aquatic organisms.

纳米粒子（NPs）不可避免地会释放到水生环境中以得到广泛使用，并且可能会影响环境中已经存在的其他污染物（例如痕量金属）的毒性。但是，NPs对常见的环境痕量金属污染物镉（Cd）的生态毒性的影响尚未得到很好的研究。在这项研究中，四种广泛使用的NPs TiO ₂（n-TiO ₂），SiO ₂（n-SiO ₂），Ag（n-Ag）和CdTe / CdS核/壳量子点（QD）对其毒性的影响镉到淡水藻类衣藻分别进行了评估。Cd减少了藻类生物量，损害了光合活性，并导致藻类的细胞内氧化应激。在无毒浓度下，n-TiO ₂（100 mg L ^-1）和n-SiO ₂（400 mg L ^-1）均减弱了Cd对藻类的毒性，从而降低了细胞内Cd含量，而前者更多明显的。QD（0.5 mg L ^-1）增加了Cd对藻类的毒性，但是n-Ag（0.2 mg L ^-1）对Cd对藻类的毒性没有显着影响。藻类细胞超微结构的微观观察发现了与n-TiO ₂，n-SiO ₂相同的现象。在细胞壁外清楚地观察到聚集。此外，NPs对Cd对藻类毒性的调节与细胞内一氧化氮（NO）（一种重要的信号分子）有关，而不是与藻类的趋光性有关。最重要的是，这项研究提供了关于不同种类的NP和Cd对水生生物的联合毒性差异的基本理解。