Mel:
http://www.tarotforum.net/showthread.php?t=69304&page=13&pp=10 (scroll to the last post.
Each of the four Elements is a combination of two Powers. The Powers, like the Elements are not talking about actual substances, but are 'code words' for a collection of related qualities that share certain behaviors. The four Powers are:
Heat - Causes things of the same kind to join, so each seeks it's own and things that are different separate, hence it is the source of separation, differentiation, discrimination, dissociation, and opposition. Heat is expansive, outward directed, energetic. It is speed. It is the cause of change, analysis, judgement, justice, honesty, critical thinking, skillfulness, diligence, authority, selfishness, intolerance, willfulness, and dominance.
Dryness - Dryness is contractive, gives shape and is formative. It causes rigidity, solidity, purpose, and practicality. It is unreceptive, inflexible, commanding, arguing, strict, concrete, of long duration, and grounded.
Cold - Unites things. It is mixing, joining, synthetic, relating, loving, undiscriminating, indecisive, slow, nurturing, sympathetic, cooperative, and sluggish.
Moisture - Has a lack of self-determination, and conforms to its surroundings. It is receptive, adaptive, form receiving, flexible, fluid, short of duration, mercurial, unreliable, indefinite and lacking self control. It is agile, gentle, obedient, conforming, passive, yielding, accommodating, weak, sensitive, understanding, kind, empathetic, and compassionate.
Fire = Dryness + Heat
Air = Heat + Moisture
Water = Moisture + Cold
Earth = Cold + Dryness
So, Water, being Cold+Moist is uniting and flexible, slow reacting and short of duration. The Water person would be accommodating, tolerant, frugal, and inoffensive, but timid, sluggish, uncreative, unresponsive, unmotivated, and rather emotionally indifferent.
As for "mysterious" this would be the Earthy Melanchollic (Cold+Dry). They are slow reacting but long of duration, this makes them introspective, penetrating, reflective, and visionary, but they are also critical, solitary, depressed, withdrawn and unforgiving.
As for "emotion", it depends on which emotion you are talking about. The fiery Choleric is angry, the airy Sanguine is cheerful, and the Melancholic is, well... melancholy.
Fecundity would probably fit best with either of the 'dry' elements, Fire or Earth. These have the ability to make their ideas happen (long of duration). Air is full of quick inspirations, but rarely has the ability to manifest the ideas. Phlegmatics are like Hobbits, they like to be comfortable, not productive or creative. Earth is slow and reflective, so deep and penetrating ideas are born from the Melancholic mind. Fire is quick and has duration, and the Choleric energy and competitiveness is endlessly productive, though anger and ego can be real hurdles.