There accordingly exists a fundamental need to understand the reversible nature of U removal in complex and/or natural waters using iron-based materials, specifically the link between nanoparticle corrosion and U desorption. The current work has therefore been established to contrast the sorption-desorption behaviour of U onto nanoscale zero-valent iron in natural waters containing dissolved oxygen (and dissolved oxygen recharge), that is, the vadose zone, with waters where dissolved oxygen is only available in trace levels, that is, the phreatic zone.