Nano-TiO2 modifies heavy metal bioaccumulation in Daphnia magna: A model study

Due to special properties, nano-TiO2 will interact with heavy metals and other pollutants in water, thus affecting the environmental behavior and ecotoxicity of these pollutants. However, the exact manner in which nano-TiO2 affects the bioaccumulation mechanisms of heavy metals is still unclear now. In the present study, quantitative structure bioaccumulation relationship (QSBAR) models were established to explore the relationships between physicochemical parameters of heavy metals and their accumulation in Daphnia magna in the absence and presence of nano-TiO2 at low metal exposure concentrations. The results showed that different physicochemical parameters affected the bioaccumulation of metals in Daphnia magna. The metal accumulation could be described by means of a Comprehensive Parameter composed of seven parameters, i.e., atomic number (AN), relative atomic weight (AW), atomic radius (AR), atomic ionization potential (AN/Delta IP), covalent index (X2r), second ionization energy (I2) and electrochemical potential (E0), in the absence of nano-TiO2, whereas the metal accumulation increased with the increase in Van Der Waals radius (rw) of metals in the presence of nano-TiO2. It was demonstrated that the bioaccumulation mechanism of the metals to Daphnia magna changed in the presence of nano-TiO2. Moreover, the bioaccumulation of more than 85% of the metals increased in the presence of nano-TiO2, but it increased differently for different metals. The present study provides an alternative approach to understand the mechanism of heavy metal bioaccumulation at low metal exposure concentrations and the effect of nano-TiO2 on metal bioaccumulation.

Automated summary

Due to its unique properties, nano-TiO2 can affect the behavior and toxicity of heavy metals and other pollutants in water. However, the specific impact of nano-TiO2 on the bioaccumulation mechanisms of heavy metals is not yet fully understood. This study utilized quantitative structure bioaccumulation relationship (QSBAR) models to investigate the relationship between physicochemical parameters of heavy metals and their accumulation in Daphnia magna, both in the presence and absence of nano-TiO2 at low metal exposure concentrations. The results revealed that different physicochemical parameters influenced metal bioaccumulation in Daphnia magna. In the absence of nano-TiO2, a Comprehensive Parameter composed of seven parameters was able to describe metal accumulation, while in the presence of nano-TiO2, metal accumulation increased with the Van Der Waals radius of metals. This study demonstrates the changing bioaccumulation mechanism of heavy metals in the presence of nano-TiO2.