The Al-water reaction has attracted considerable attention in the past few years, because it is an economically viable way to supply hydrogen for portable and kW-grade fuel cells. The water type is found to have a significant impact on Al-water reaction. In this work, the effect of trace species in water on Al-water reaction is investigated systematically. It is found that the trace organic acids originated from the decay of botanies and animals in nature and trace F- ions, rather than other cations and anions, play a key role in the reaction dynamics of Al with water. The mechanism analyses reveal that the organic acids and F- ions form complexes with aluminol groups on Al particle surfaces to impede the hydration process of Al surface oxide film and retard the reaction of Al with water. The present results imply that a suitable water should be chosen for the Al-water reaction to generate hydrogen. At the same time, the organic acids and trace F- ions could be used as the agents to prevent undesirable Al-water reaction. (C) 2013 Elsevier B.V. All rights reserved.