Enhanced bioaccumulation and toxicity of lithium iron phosphate micro/nanoparticles relative to lithium ions in Daphnia magna neonates

Growing demand for lithium driven by clean energy technologies has raised environmental risks to aquatic ecosystems. However, research on its ecological toxicity remains limited, with most studies focusing on lithium ion toxicity, while particulate lithium toxicity is poorly understood. In this study, lithium iron phosphate (LFP) with two particle sizes, as well as lithium ions, were selected to investigate their biokinetic processes and toxic effects in Daphnia magna neonates. Using the two-compartment toxicokinetic model, the results indicate that LFP exhibits a higher bio-accumulation potential than ions, with accumulation being more pronounced in the μm-scale particles compared to the nm-scale. Furthermore, lithium causes developmental disorders, including reduced length and eyespot deformities, through disruption of ionic balance and energy supply. These effects are more severe under LFP exposure. Due to its small size and easy internalization, nm-LFP causes more severe oxidative stress compared to μm-LFP, as evidenced by the accumulation of reactive oxygen species and malondialdehyde, while lithium ions minimally affect antioxidant systems. The results emphasize the critical role of lithium form and size specificity in biokinetic and toxicity, providing a basis for assessing ecological risk of lithium-based battery materials in aquatic environments. Environmental implication Lithium is widely used in energy, industrial production, and pharmaceuticals. There are few studies on the aquatic toxicity of lithium, and most of them focus on the toxicity of lithium ions. The present study indicated that lithium iron phosphate micro/nanoparticles were more likely to accumulate in D. magna than lithium ions. Environmental concentrations of nano-lithium iron phosphate can influent ionic disorder and energy supply, as well as causing more severe oxidative stress than μm-level. The results highlight the key role of the form and size specificity of lithium in biodynamics and toxic effects, which deserves more attention.