Salinity and toxicity of zinc oxide nanoparticles in aquatic system: A review study

Abstract

Nanotechnology has significantly advanced in many scientific fields, particularly in nanoscale materials. Nanoparticles are distinguished by their small size and large surface area contributing to their unique functionality and reactivity. One of the most effective types of nanoparticles is zinc oxide nanoparticles (ZnO-NPs), known for their exceptional physical and chemical properties. Aquatic organisms benefit from ZnO-NPs due to their ability to promote growth and provide nutritional advantages. An aqueous solution containing ZnO-NPs has proven effective in removing lead and cadmium from water. Furthermore, incorporating zinc oxide in nanoform into fish feed enhances food palatability and increases consumption rates. However, improper handling of these nanoparticles can pose serious environmental risks. The zinc ions released by ZnO-NPs in water are considered the primary source of toxicity. The toxicity of ZnO-NPs is influenced by the presence of Zn²⁺ ions in solution and the formation of particle aggregates. Various parameters, including salinity, affect the ZnO-NP aggregates and the release of zinc ions. Salinity facilitates this complexation by providing additional chloride ions, which further reduce Zn²⁺ concentrations. While salinity increases aggregation, Zn²⁺ levels tend to decrease with rising salinity. Therefore, the salinity of water must be considered when assessing the impact of nanoparticles on aquatic life. This review, for the first time, investigated the effect of salinity on the properties and toxicity of zinc oxide nanoparticles. Additionally, it highlighted the detrimental effects of ZnO-NPs on fish. To achieve a comprehensive understanding of salinity-nanoparticle interactions, further research into the physicochemical properties and toxicity of nanoparticles, such as ZnO-NPs, is essential.