ABSTRACT
Emerging contaminants, including nanoparticles, need to undergo environmental risk assessment, whereby they are tested for properties of persistence in the environment, toxicity or bioaccumulation. To date, little data exists for the bioaccumulation of aluminium oxide nanoparticles (Al2O3 NPs) and zinc oxide nanoparticles (ZnO NPs) in aquatic animals, particularly fishes. Therefore, this study was conducted to determine the accumulation of aluminium ion Al3+ and zinc ion Zn2+ by embryos of Clarias gariepinus exposed to a combined mixture of Al2O3 NPs and ZnO NPs. The embryos (3hpf) were exposed to varying concentrations (0, 0.5, 1, 5 and 10mg/l) of Al2O3 NPs and ZnO NPs, for a short term of 48 hours and assessed for bioaccumulation of the ions. The assay revealed a dose-time-dependent accumulation of Al3+ from Al2O3 NP exposure in the embryos. More of the ion was accumulated in the embryos across all treatment groups at 48hpf, which is followed by 36hpf and 24hpf. At 24hpf, the concentration of Al3+ in embryos was 0, 0.05 ± 0.01, 0.07 ± 0.02, 0.08 ± 0.00, and 0.09 ± 0.04 mg/l for control, 0.5mg/l, 1mg/l, 5mg/l and 10mg/l treatment groups respectively. At 36hpf, the concentration of Al3+ in embryos was 0, 0.9 ± 0.01, 0.12 ± 0.00, 0.14 ± 0.01, and 0.23 ± 0.16 mg/l for control, 0.5mg/l, 1mg/l, 5mg/l and 10mg/l treatment groups respectively. At 48hpf, the concentration of Al3+ in embryos was 0, 0.26 ± 0.00, 0.28 ± 0.01, 0.35 ± 0.01, and 0.55 ± 0.05 mg/l for control, 0.5mg/l, 1mg/l, 5mg/l and 10mg/l treatment groups respectively. Similar observations were recorded for accumulation of Zn2+ in the embryos. At 24hpf, the concentration of Zn2+ in embryos was 0, 0.05 ± 0.04, 0.05 ± 0.05, 0.01 ± 0.00, and 0.17 ± 0.14 mg/l for control, 0.5mg/l, 1mg/l, 5mg/l and 10mg/l treatment groups respectively. At 36hpf, the concentration of Zn2+ in embryos was 0.00, 0.34 ± 0.04, 0.82 ± 0.29, 0.99 ± 0.48, and 1.34 ± 0.89 mg/l for control, 0.5mg/l, 1mg/l, 5mg/l and 10mg/l treatment groups respectively. At 48hpf, the concentration of Zn 2+ in embryos was 0.00, 0.83 ± 0.39, 1.66 ± 0.88, 1.80 ± 0.67, and 2.03 ± 0.48 mg/l for control, 0.5mg/l, 1mg/l, 5mg/l and 10mg/l treatment groups respectively. However, there was no significant difference in the concentration of Al3+ and Zn2+ in the embryos in all treatment groups at any time of the exposure compared to the control (P>0.05). These findings highlight the ecological and health implications of nanoparticle exposure in aquatic ecosystems, underscoring the importance of continued research and regulatory measures to ensure environmental safety.
