XUV-driven escape of hydrogen atmospheres on super-Earths

XUV exposed non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: Atmospheric expansion and thermal escape
http://arxiv.org/abs/1212.4982

Final conclusion...

Quote :

Thus, terrestrial exoplanets in orbits inside the habitable zone, which capture too much H/He nebula gas or degas dense steam atmospheres most likely keep their hydrogen envelopes and may end as sub-Neptune-type planets or low-density “super-Earths.”

Interesting paper about thermal mass loss for corot7b and k10b they started as super earth or sub Uranus mass planet

Are you referring to this one?

Could CoRoT-7b and Kepler-10b be remnants of evaporated gas or ice giants?
http://www.sciencedirect.com/science/article/pii/S0032063311001759

Probing the Blow-Off Criteria of Hydrogen-Rich "Super-Earths"
http://arxiv.org/abs/1210.0793

So it seems that the super-Earths experience 1--2 orders of magnitude lower mass-loss rates than hot Jupiters such as HD 209458b.

These planets are therefore predicted to retain their primordial hydrogen-rich atmospheres.

Press-release from the Royal Astronomical Society:
Are super-Earths really mini-Neptunes?

All depends on radius of particular planet but it seems that from 2.5 to 1.5 earth radius amount of hydrogen is rapidly decreasing and density increasing

I am not sure if any amount of water matters but I suppose more water contain planet the less hydrogen as gravity is then weaker