Effects of sediment-associated CuO nanoparticles on Cu bioaccumulation and oxidative stress responses in freshwater snail Bellamya aeruginosa.

Copper oxide nanoparticles (CuO-NPs) may pose high ecological risks to aquatic ecosystems. While sediments are the final destinations for CuO-NPs, little is known about the potential ecotoxicity of sediment-associated CuO-NPs on freshwater deposit-feeding macroinvertebrates. The gastropod Bellamya aeruginosa was chosen as an ecotoxicological test species. Adult snails were exposed to Cu (180μg/g dry weight (DW)) added to sediments in the form of CuO-NPs, CuO microparticles (CuO-MPs, size control), and CuSO4 (solubility control) for 7, 14, and 28days, Cu burdens in different tissues and biomarkers of oxidative stress were determined to understand Cu accumulation differences among tissues, potential mechanisms of Cu uptake, time-effect relationships, particle size effects, and the relative contribution of toxicity from CuO-NPs and its soluble Cu ions. There was no difference in Cu ion concentrations in porewaters between the CuO-NPs and CuO-MPs treatments. In addition, relatively low Cu ion concentrations in porewater might indicate their remarkably low solubility. The hepatopancreas and gonad of B. aeruginosa are the primary target tissues for Cu accumulation. Cu accumulation in the hepatopancreas and gonad from CuSO4 treatments was consistently higher than that from the CuO-NPs and CuO-MPs treatments. After long-term exposure, Cu accumulation was higher from CuO-NPs than from CuO-MPs, especially, the Cu accumulation rate from CuO-NPs was greater than that from CuSO4 . Short-term exposure to the three Cu forms caused oxidative stress to the hepatopancreas. CuO-MPs did not cause oxidative damage. Long-term exposure to CuO-NPs and CuSO4 resulted in oxidative damage. Overall, prolonged exposure to CuO-NPs will increase the ecotoxicity risk to B. aeruginosa. Although there was no difference in Cu accumulation between the CuO-NPs and CuO-MPs treatments after 14days of exposure, pronounced oxidative damage was caused by exposure to CuO-NPs but not to CuO-MPs, implying that toxicity of CuO-NPs could be attributed to specific nanoparticulate effects.