Wastewater-Aged Silver Nanoparticles in Single and Combined Exposures with Titanium Dioxide Affect the Early Development of the Marine Copepod .

In this study, the effects of aged Ag and TiO nanoparticles (NPs), individually and as a mixture, in wastewater relative to their pristine counterparts on the development of the copepod nauplii () were investigated. NP behavior in synthetic wastewater and seawater was characterized during aging and exposure. A delayed development and subsequent mortality were observed after 6 days of exposure to aged Ag NPs, with a twofold decrease in EC (316 μg/L) compared to pristine NPs (EC 640 μg/L) despite the similar dissolved Ag concentrations measured for aged and pristine Ag NPs (441 and 378 μg/L, respectively). In coexposures with TiO NPs, higher dissolved Ag levels were measured for aged NPs (238.3 μg/L) relative to pristine NPs (98.57 μg/L). Coexposure resulted in a slight decrease (15%) in the Ag NP EC (270 μg/L) with a 1.9-fold increase in the Ag NP retained within the organisms after depuration (2.82% retention) compared to Ag NP single exposures as measured with sp-ICP-MS, suggesting that the particles are still bioavailable despite the heteroaggregation observed between Ag, Ti NPs, and wastewater components. This study shows that the presence of TiO NPs can affect the stability and toxicity of Ag NPs in complex media that cannot be predicted solely based on ionic, total, or nanoparticulate concentrations, and the need for studying NP interactions in more complex matrices is highlighted.