Integrating FTIR 2D correlation analyses, regular and omics analyses studies on the interaction and algal toxicity mechanisms between graphene oxide and cadmium.

Graphene oxide (GO, a popular 2D graphene-based nanomaterial) has developed quickly and has received considerable attention for its applications in environmental protection and pollutant removal. However, significant knowledge gaps still exist about the interaction characteristic and joint toxicity mechanism of GO and cadmium (Cd) on aquatic organisms. In this study, GO showed a high adsorption capacity (120. 6 mg/g) and strong adsorption affinity (K = 0.85 L/mg) for Cd. Integrating multiple analytical methods (e.g., electron microscopy, Raman spectra, and 2D correlation spectroscopy) revealed that Cd is uniformly adsorbed on the GO surface and edge mainly through cation-π interactions. The combined ecological effects of GO and Cd on Chlorella vulgaris were observed. Cd induced more severe growth inhibition, photosynthesis toxicity, ultrastructure damage and plasmolysis than GO. Interestingly, we found that GO nanosheets could augment the algal toxicity of Cd (e.g., chlorophyll b, mitochondrial membrane damage, and uptake). Transcriptomics and metabolomics further explained the underlying mechanism. The results indicated that the regulation of PSI-, PSII-, and metal transport-related genes (e.g., ABCG37 and ZIP4) and the inhibition of metabolic pathways (e.g., amino acid, fatty acid, and carbohydrate metabolism) were responsible for the persistent phytotoxicity. The present work provides mechanistic insights into the roles of coexisting inorganic pollutants on the environmental fate and risk of GO in aquatic ecosystems.