Assessment of metal variability in green and red seaweed exposed to TiO₂ nanoparticles

The use of nanomaterials has expanded significantly in recent years, particularly in biomedical and industrial applications. Among them, titanium dioxide nanoparticles (TiO₂NPs) are widely employed as UV filters in cosmetics and in wastewater treatment processes, leading to their increasing release into the environment and raising concerns about potential effects on aquatic organisms. This study evaluates the variation in the elemental composition of primary producers (green seaweed Ulva sp. and red seaweed Palmaria palmata), exposed to 5 nm TiO₂NPs at different concentrations (0, 0.1, and 1.0 mg L⁻¹) for 28 days. After microwave-assisted acid digestion (HNO₃ + H₂O₂), 14 trace elements (As, Cd, Ce, Co, Cr, Cu, Mo, Ni, Pb, Rb, Sb, Se, V, and Zn) were determined by ICP-MS. The method showed low detection limits, ensuring high sensitivity, and good accuracy (analysis of BCR®-279 and ERM®-CD281 certified reference materials). In Ulva sp., increasing exposure to TiO₂NP concentration was associated with significant changes in As, Cd, Ce, Co, Cu, Mo, and Ni, with different trends depending on nanoparticle concentration and exposure time. In P. palmata, only Ce displayed a consistent reduction with increasing exposure time. Moreover, Ti concentrations in Ulva sp. showed positive correlations with several elements, particularly As, Co, Cu, Mo, Rb, and V, after 28 days of exposure. These results demonstrate that exposure to TiO₂NPs can alter the elemental composition of marine macroalgae.