Nanobubble and Slow-Release Hydrogen Delivery Methods for Interfacial Remediation of Copper-Induced Toxicity in Aquatic Environments

Heavy metal pollution poses a serious threat to aquatic environments, requiring effective strategies to mitigate its harmful effects. Hydrogen molecules have shown potential in alleviating oxidative stress caused by heavy metals; however, delivering hydrogen in water remains challenging. In this study, four hydrogen delivery methods, namely, hydrogen water without nanobubbles (NBs), hydrogen NB water, nanosilicon, and sodium alginate-coated nanosilicon gel microspheres, were evaluated for their ability to protect zebrafish embryos from copper ion-induced toxicity. Hydrogen water without NB and hydrogen NB water initially contained 1.15 and 1.53 mg/L dissolved hydrogen, respectively, but both fell below 0.1 mg/L within 12 h. In contrast, gel microspheres had a lower dissolved hydrogen concentration (0.78 mg/L) yet sustain hydrogen release for more than 48 h, delivering a cumulative hydrogen yield of 786.67 mL/g. Different hydrogen delivery methods exhibit varying degrees of effectiveness in alleviating Cu²⁺-induced embryotoxicity. Exposure to Cu²⁺significantly increased embryo mortality from a control rate of 1.33% to 66.67% and reduced hatching rates from 82.44% to 0%. All four hydrogen treatments significantly lowered mortality (to 44.67%, 4%, 13.33%, and 34.67%) and raised hatching rates (to 10.98%, 14.29%, 50.76%, and 21.35%) while reducing copper accumulation and boosting antioxidant enzyme activity. Among these methods, hydrogen NB water showed the strongest toxicity alleviation effect. Gas chromatography revealed that NBs enhance hydrogen transport, and transcriptomic analysis demonstrated that hydrogen affects cellular interactions, signaling pathways, and structural components, thereby mitigating oxidative damage. Overall, these findings highlight an innovative approach to harness hydrogen molecules for improving aquatic organism survival and restoring ecosystems under heavy metal stress. This study provides valuable insights for advancing water pollution control and promoting the health of aquatic life.