There appears to be no reliable influence by positive or negative air ions (high levels occur around waterfalls) on mood according to a meta-analysis – http://www.ncbi.nlm.nih.gov/pubmed/23320516, but I certainly felt good working the falls of Ricketts Glen last month.
We had some very rainy weather my first day there which hindered my efforts, but the next day was magnificent and I did the loop down and back up the other side of the falls trail. All that rain had the water running deep and fast (and loud), making it quite the experience. Many other photographers thought to as well and added to the challenges of working that day.
I hadn’t photographed at Ricketts Glen in over ten years, so I went with light gear opting to be nimble and productive. I worked entirely with one camera and one lens — the Olympus EM-5 and the Panasonic 14-140mm II, and a small tripod. I used a polarizing filter and closed down the aperture for maximum depth of field.
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Paul Grecian - Photography 
Holy ion, Batman! Great image, bustling & calm.