The potential phototoxicity of nano-scale ZnO induced by visible light on freshwater ecosystems.

With the development of nanotechnology, nanomaterials have been widely applied in anti-bacterial coating, electronic device, and personal care products. NanoZnO is one of the most used materials and its ecotoxicity has been extensively studied. To explore the potential phototoxicity of nanoZnO induced by visible light, we conducted a long-term experiment on litter decomposition of Typha angustifolia leaves with assessment of fungal multifaceted natures. After 158 d exposure, the decomposition rate of leaf litter was decreased by nanoZnO but no additional effect by visible light. However, visible light enhanced the inhibitory effect of nanoZnO on fungal sporulation rate due to light-induced dissolution of nanoZnO. On the contrary, enzymes such as β-glucosidase, cellobiohydrolase, and leucine-aminopeptidase were significantly increased by the interaction of nanoZnO and visible light, which led to high efficiency of leaf carbon decomposition. Furthermore, different treatments and exposure time separated fungal community associated with litter decomposition. Therefore, the study provided the evidence of the contribution of visible light to nanoparticle phototoxicity at the ecosystem level.