The fate and toxicity of silver nanoparticles (AgNPs) and ions in water bodies is largely determined by the natural organic matter (NOM)-mediated redox cycling. However, the process of NOM-mediated redox cycling in the day/night cycles remains elusive. In this study, the inter-transformation between AgNPs and Ag+ ion caused by humic acid (HA) was investigated under controlled light and dark conditions. It was shown that HA induced the reduction of Ag+ into AgNPs in simulated sunlight, and also oxidize AgNPs to release Ag+ in darkness. Kinetics ...
