Combined toxic effects of TiO2 nanoparticles and organochlorines on Chlorella pyrenoidosa in karst area natural waters.

With the discharge of nanoparticles (NPs) into the environment, NPs can interact with coexisting organic pollutants, resulting in combined toxic effects. In order to more realistically evaluate the potential toxic effects of NPs and coexisting pollutants on aquatic organisms. We evaluated the combined toxicities of TiO2 nanoparticles (TiO2 NPs) and three different organochlorines(OCs)-pentachlorobenzene (PeCB), 3,3',4,4'-tetrachlorobiphenyl (PCB-77) and atrazine to algae (Chlorella pyrenoidosa) in three karst natural waters. The results indicate that the individual toxicities of TiO2 NPs and OCs in natural waters were less than those of OECD medium, and the combined toxicities were different from but generally similar to those of OECD medium. The individual and combined toxicities were the largest in UW. The correlation analysis showed that the toxicities of TiO2 NPs and OCs were mainly related to TOC, ionic strength, Ca2+ and Mg2+ in natural water. The binary combined toxicities of PeCB and atrazine with TiO2 NPs to algae were synergistic. The binary combined toxicity of TiO2 NPs and PCB-77 to algae was antagonistic. The presence of TiO2 NPs increased the algae-accumulations of OCs. PeCB and atrazine all increased the algae-accumulations of TiO2 NPs, while PCB-77 showed the opposite result. The above results indicated that due to the influence of different hydrochemical properties in karst natural waters, there were differences between TiO2 NPs and OCs in their toxic effects, structural and functional damage, and bioaccumulation.