The 2012 Gordon Research Conference on «Environmental Sciences: Water» will continue its long tradition of surveying priority and emerging issues across all aspects of aquatic environmental science. The scope will span multiple disciplines (chemistry, biology, geology, engineering, health science), media (soil, groundwater, surface water, atmospheric water, drinking water, wastewater), and scales (molecular, nano, cellular, ecosystem, global). This year, the unifying theme will be the scientific grand challenges that form the foundations and, at the same time, the frontiers of aquatic environmental science. These grand challenges, which include topics related to free radical reactions, natural organic matter, nanoparticles, biotransformation, reactive transport and surface chemistry, will provide the general themes for each session. Overall, the program will highlight the crosscutting significance of these grand challenges through sessions that represent the depth and breadth of each grand challenge issue with speakers engaged in innovative and significant research on diverse aspects to environmental aquatic science.