  Context. The composition of a protoplanetary disk at a given location does
not only depend on temperature and pressure but also on the time dependent
transport of matter, such as radial drift of solid bodies, which could release
water and other volatile species before disintegration or accretion onto a
larger body with potentially considerable implications for the composition of
planets. Aims. We perform a parameter study focused on the water depletion of
different sized bodies able to cross the water snowline by gas induced radial
drift. Methods. Either the analytical Hertz-Knudsen-Langmuir sublimation
formula assuming equilibrium temperature within the body or a more involved,
numerical model for the internal thermal evolution is coupled with an
alpha-disk model. Different properties of the disk and the embedded body are
explored. Results. Bodies with radii up to 100 meter drift faster towards the
central star than the water snowline, hence, cross it. The region that can be
reached before complete disintegration - and is therefore polluted with H2O ice
- extends to 10 percent closer to the star than the snowline location. The
extent of this polluted region could be multiple times larger in the presence
of a dust mantle, which is, however, unlikely to form due to frequent
collisions with smaller-than centimeter sized objects. Conclusions. Given a
significant abundance of meter sized boulders in protoplanetary disks, the
transport of water by radial drift of these bodies towards regions closer to
the star than the snowline is not negligible and this flux of volatiles can be
estimated for a given distribution of solid body sizes and compositions. A
simple expression for surface sublimation is applicable for a homogeneous body
consisting of only dust and water ice without a dust mantle.
