Effect of Zinc Oxide Nanoparticles on Denitrification and Denitrifying Bacteria Communities in Typical Estuarine Sediments

For revealing the effects of increasing of zinc oxide nanoparticles (ZnO NPs) on denitrification and denitrifying bacteria communities in estuarine sediments, the surface sediments of two typical estuaries (the Yangtze River Estuary and the Yellow River Estuary) were added with medium concentration (170 mgL⁻¹) and high concentration (1700 mg L⁻¹) of ZnO NPs for anaerobic culture in laboratory. The concentration of NO₃⁻ and NO₂⁻, the reductase activity and denitrification rate were measured by physico-chemical analysis, nirS gene abundance and denitrifying bacteria communities by molecular biological methods. The results showed that ZnO NPs inhibited NO₃⁻, NO₂⁻ reduction process and NO₃⁻, NO₂⁻ reductase activity, and a stronger inhibition effect resulting from the higher ZnO NPs concentration. ZnO NPs decreased nirS gene abundance and community diversity of denitrifying bacteria. In addition, the inhibition degree of ZnO NPs on the denitrification process of sediments in different estuaries was different. These results were of great significance for evaluating the potential ecological toxicity and risks of nanomaterials in estuaries.