Airborne particulate material contributes significant quantities of trace elements to surface waters. Metals may be partially transferred from airborne particulate material to the aqueous phase while they are still in the atmosphere, but transfer to solution is most important when the particles contact surface waters. In both artificial and natural waters, appreciable fractions of most metals dissolve within minutes. This is followed by a further, slower dissolution over a period of hours or days. Dissolved metals interact with natural organic material and mineral particles. Interactions with organics and metal oxides are now sufficiently understood for them to be modelled by considering surface charges and chemical binding. More measurements on natural systems are required to validate these models and to establish the respective importance and roles of organic and inorganic interactions. Compared to sea water, data on fresh water are scarce. In view of their compositional variability and the relatively high concentrations of trace metals which they often contain, there is an urgent need for systematic investigations of the partitioning of metals in fresh waters.