Dissolved organic matter (DOM) is ubiquitous in the environment and has high reactivity.Once engineered nanoparticles (ENPs) are released into natural systems,interactions of DOM with ENPs may significantly affect the fate and transport of ENPs,as well as the bioavailability and toxicity of ENPs to organisms.However,because of the complexity of DOM and the shortage of useful characterization methods,large knowledge gaps exist in our understanding of the interactions between DOM and ENPs.In this article,we systematically reviewed the interactions between DOM and ENPs,discussed the effects of DOM on the environmental behavior of ENPs,and described the changes in bioavailability and toxicity of ENPs caused by DOM.Critical evaluations of published references suggest further need for assessing and predicting the influences of DOM on the transport,transformation,bioavailability,and toxicity of ENPs in the environment.