Different phototoxicities of ZnO nanoparticle on stream functioning

Abstract To explore the chronic phototoxicity of ZnO nanoparticles (NPs) on stream ecosystems, a microcosm experiment was conducted on Populus nigra L. leaf decomposition with ZnO NPs under different light components (visible and ultraviolet (UV) light) with a natural photoperiod. Light components significantly affected the transformation dynamic of ZnO NPs. After chronic exposure (day 15 to 30), ZnO NPs under light irradiation caused significant decrease in the microbial biomass, but significant increase in the fungal biomass. Compared to visible light, UV light led to lower microbial biomass and metabolic activity but higher antioxidant activity when ZnO NP concentrations were 10 and 20 mg L−1, eventually causing significant reductions in decomposition rates. Pleosporales sp., Montagnulaceae sp., and Volutella citronella responded sensitively to ZnO NPs. However, higher decomposition efficiency of leaf nitrogen was achieved under UV light when ZnO NPs concentrations were 10 mg L−1, suggesting that microbial nitrogen-related enzymes and ZnO nanoparticle photocatalytic properties contribute to leaf degradation. In conclusion, the results of this study provide compelling evidence that light components strongly affect ZnO NPs transformation, which impacts microbial communities with consequences for ecological processes in stream ecosystems.