Effects of Fe₂O₃ nanoparticles on extracellular polymeric substances and nonylphenol degradation in river sediment

In this study, the impact of Fe₂O₃ nanoparticles (nFe₂O₃) on microbial extracellular polymeric substances (EPS) and nonylphenol (NP) degradation in sediment were investigated. The results showed that the addition of nFe₂O₃ lowered the degree of EPS overproduction and the amount of polysaccharides and proteins secreted in NP contaminated sediment. Particularly, the secretion of colloidal EPS (C-EPS) lowered significantly (P < 0.05), and the content of tyrosine-like, tryptophan-like, and soluble microbial by-product-like substances in C-EPS also decreased, leading to a lower aromaticity, humification, and hydrophobicity of C-EPS. Furthermore, with lower C-EPS content in water, NP was adsorbed to sediment more easily, and the weakened toxic effect of NP to bacteria as well as a higher proportion of organic matter degrading microbes stimulated NP degradation. These findings revealed the vital role of nFe₂O₃ in alleviating NP toxicity to microbes and reducing NP ecological risk in aquatic environments.