What causes the "white water" smell?
I don't have any journal article citations to back me up, but I've always understood that this distinct smell is from water aerosol.  You can detect the same smell during a fine misting rain as well as near water sprinklers (if the sprinklers produce a very fine mist of water).  But you don't get this smell from water vapor (steam) or bulk water, so there is clearly a specific range of water droplet size that triggers the olfactory response.

I've personally always wanted to know what the specific size range of these aerosol droplets needs to be to trigger the olfactory response.  I'm confident someone has studied this, but I don't know which journals to search to find the answer.