Abstract: Graphene oxide (GO) and copper oxide nanoparticles (CuO NPs) lead to environmental exposure risks due to their widespread applications. The differences in properties, structures, and environmental behaviors may cause different ecological effects. We compared the effects of short-term exposure of 0.5 mg·L^-1 GO and CuO NPs on the operational performance of constructed wetlands (CWs) and the ecotoxicity mechanism. The results showed that the exposure of GO and CuO NPs did not affect COD and TP removal in the CWs. Removal rate of NH₄⁺-N in wetlands exposed to GO and CuO NPs was reduced by 5% and 9%, respectively, indicating that both GO and CuO NPs could inhibit the nitrogen removal effect in CWs. Compared with GO, CuO NPs inhibited nitrification more heavily. GO and CuO NPs exposure inhibited dehydrogenase activity. CuO NPs also had a significant inhibitory effect on urease activity. Phosphatase activity was the most responsive, which was significantly increased under both exposures. In the microbial nitrogen metabolism pathway, nitrification functional genes were inhibited by both GO and CuO NPs exposure, while denitrification functional genes were promoted by CuO NPs exposure. These results could provide a theoretical basis for assessing the ecotoxicity of different types of nanoparticles.

Key words: constructed wetland, graphene oxide, copper oxide nanoparticles, operational performance, nitrogen metabolism