Spatial distribution, temporal variations and source of titanium dioxide nanoparticles in Taihu Lake, China

The detrimental impacts of titanium dioxide nanoparticles (TiO₂NPs) on the ecosystem and organisms have aroused great public concerns. However, the information on their concentration in the real aquatic environment is still limited, hindering the rational evaluation of their potential hazards. In this study, water samples from Taihu Lake were collected in June and November 2023, to investigate the spatial distribution and temporal variations of TiO₂NPs. Using phosphorylated Fe₃O₄ particles based magnetic solid phase extraction and ICP-MS determination, high concentrations of TiO₂NPs were detected in the western and northern regions of Taihu Lake. These areas contribute to 83 % of the total runoff into the lake. Total Ti levels were typically higher in November than in June, but no marked seasonal difference was observed for TiO₂NPs. Different shapes of TiO₂NPs with both smooth and rough surfaces were observed in the surface water. To further distinguish whether these TiO₂NPs were sourced from the natural background or anthropogenic sources, the ratios of Ti to other rare elements including Nb were calculated. In November, the Ti/Nb ratios at most sampling sites were significantly higher than those in June, indicating that a large amount of engineered TiO₂NPs are discharged into Taihu Lake during the summer and autumn seasons. Our study contributes to the understanding of contamination levels, spatial distribution, and temporal variation of TiO₂NPs in lake systems, and provides valuable data for their further risk assessment.