Distribution and source of titanium dioxide nanoparticles in seawater and sediment from Jiaozhou Bay, China

The widespread use of titanium dioxide nanoparticles (TiO₂NPs) and their potential adverse effects on the ecosystems have raised significant concerns. Limitations in detection methods and insufficient data on their environmental concentrations, especially in marine systems, hinder the accurate risk assessment. Herein, a robust method for the analysis of TiO₂NPs in marine sediment is developed, with a detection limit of 0.09 μg/g. The spatial distribution of TiO₂NPs in seawater and sediments in Jiaozhou Bay was investigated. High concentrations of TiO₂NPs in seawater were distributed in the northeastern region, near river inlets and sea-crossing bridges. By using the proposed method, the mass concentrations of TiO₂NPs in the Jiaozhou Bay sediments were first reported, ranging from 0.697 to 2.44 mg/g. There was no positive correlation between the distribution of TiO₂NPs in seawater and sediment. The Ti/Nb ratio of TiO₂NPs was used to distinguish whether TiO₂NPs were sourced from the background or anthropogenic inputs. Similar distribution trends of Ti/Nb ratios in seawater and sediment suggest that significant engineered TiO₂NPs were transferred from high-salinity seawater to sediment via agglomeration and sedimentation. Industrial discharges and bridge runoff may be primary contributors of engineered TiO₂NPs. This study provides a reliable method for the analysis of TiO₂NPs in marine sediment, which would contribute to tracking the mobility of TiO₂NPs in the marine system. The data on the spatial distribution and possible sources of TiO₂NPs in Jiaozhou Bay also benefit the risk assessment and control.