Ecotoxicity Assessment of Zinc Oxide Nanoparticles in Embryo Stages of Zebrafish (Danio rerio)

Nuraqeelah, Binti Mohammad Shamhari (2020) Ecotoxicity Assessment of Zinc Oxide Nanoparticles in Embryo Stages of Zebrafish (Danio rerio). Masters thesis, University Malaysia Sarawak, UNIMAS.

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Abstract

High demand of nanonmaterials have produced enormous applications in global industries. However, due to their extensive productions, release of different size of zinc oxide nanoparticles (ZnO NPs) into the environment has raised concerns in which the environment might pose ecotoxicological risk to the aquatic organisms. Presence of natural organic matter (NOM) mainly humic acid (HA) has also gain interest. As HA affect behavior of ZnO NPs which eventually affect the level of toxicity of ZnO NPs. Thus, this study was carried out in order to determine the toxicity level of different size (7.4 nm, 36 nm, and 73 nm) of ZnO NPs with different concentrations (1, 5, 10, 30, 50, and 100 mg/L) in embryonic zebrafish (5 hpf -96 hpf) with and without the presence of HA. This study was also carried out to investigate the behaviour of ZnO NPs in embryo water in terms of aggregation and dissolution. Findings showed that smaller ZnO NPs (7.4 nm) has a higher toxicity than larger NPs (36 nm and 73 nm) in which low survival rate was observed in embryo exposed to smaller ZnO NPs with 0% hatching rate. However, the presence of HA has greatly alleviated the toxicity of three sizes of ZnO NPs as more than 50 % of the survival rates as well as the hatching rates of embryonic zebrafish were observed. Other than that, dissolution and aggregation were found to be one of the most important role that contribute to toxicity. Finding demonstrated that smaller ZnO NPs has high dissolution as compared to larger ZnO NPs in which aggregation has occurred. The presence of HA has surprisingly increased the dissolution of ZnO NPs and stabilized the ZnO NPs in water. Therefore, presence of HA did influence the toxicity and the fate of ZnO NPs in the environment regardless of their particle sizes.

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