Differences in the bioaccumulation and toxicity of monomeric Al and nano-Al13 in the organs of Corbicula fluminea

The chemical reactivity and toxicity of aluminum are related to its speciation, but the differences in bioaccumulation and toxic mechanisms between different Al species remain unclear. In this study, Corbicula fluminea was exposed to polymeric Al (nano-Al₁₃) and monomeric Al (Al_m) to compare their accumulation kinetics and toxicity responses in different organs. Results showed that gills accumulated more Al than digestive glands. Al_m exhibited a slower discharge rate in the gills, whereas Al₁₃ was excreted more slowly from the digestive glands. Higher Al concentrations cause irreversible damage to gill nerves, while the digestive glands could adapt to external Al stress by behavioral regulation. Significant differences existed in the toxic effects of Al_m and Al₁₃. Al_m obstructed gill filament pores, causing swelling and deformation, resulting in pronounced mechanical damage and significant siphoning inhibition. Al₁₃ more easily adhered to gill valve surfaces, exerting milder interference with gill tissue structure and physiological activities, but having more noticeable impacts on the nervous system. AChE inhibition by Al primarily affected gill nerves, diminishing the continuous Al uptake intensity, while potentially stimulating nerves in the digestive gland to promote the expulsion of accumulated Al. These findings reveal distinct organ-specific responses of Al species, contributing to a better understanding of their environmental risks and informing safety assessments of residual Al in aquatic systems.