I am not sure about the fluoride in the water, it is a halogen and I assume would just make a very minute amount of hydrofluoric acid, in solution, I also assume this would be so minute amount that it would almost be undetectable.
There are minerals in water that may react more with the acids like calcium, magnesium, iron and silica (this sand glass should not react) the metals high in the reaction series may be the reaction you notice, or maybe just the water itself, cold water holds a considerable amount of oxygen also, as aqua regia usually uses high concentrated nitric which is reacting with metals, was there metals in your solution, also if you had nitrous oxide fume you may not have been able to see fuming off the water may be reacting with these, I think this combination of chemicals would produce several differing reactions the fumes you see may be hard to blame on one single one.
Of coarse I am just speculating on this, but I believe it could be most any thing beside a very small amount of fluorine to purify water. If we can drink it I do not think it will affect your aqua regia solution much.
Now just my guess, I really do not know..
