The series of papers presented in this special issue highlight several transformations of natural and engineered nanomaterials that are critical processes affecting their behavior in the environment. It begins to make connections between the nanoscale properties and features of various NP types and their macromolecular coatings, and their behavior and effects in natural systems. The papers also illustrate that additional research and the development of novel tools for characterizing NMs in situ and at relevant concentrations is needed to more completely describe transformation processes and determine the extent to which these processes occur in real systems.

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