  Context. Ice lines are suggested to play a significant role in grain growth
and planetesimal formation in protoplanetary disks. Evaporation fronts directly
influence the gas and ice abundances of volatile species in the disk and
therefore the coagulation physics and efficiency and the chemical composition
of the resulting planetesimals.
  Aims. In this work we investigate the influence of the existence of the CO
ice line on the particle growth and on the distribution of CO in the disk.
  Methods. We include the possibility of tracking the CO content and/or other
volatiles in particles and in the gas in our existing dust coagulation and disk
evolution model and developed a method for evaporation and condensation of CO
using the Hertz-Knudsen equation. Our model does not include fragmentation,
yet, which will be part of further investigations.
  Results. We find no enhanced grain growth just outside the ice line where the
particle size is limited by radial drift. Instead we find a depletion of solid
material inside the ice line which is solely due to evaporation of the CO. Such
a depression inside the ice line may be observable and may help to quantify the
processes described in this work. Furthermore, we find that the viscosity and
diffusivity of the gas heavily influence the re-distribution of vaporized CO at
the ice line and can lead to an increase in the CO abundance by up to a factors
of a few in the region just inside the ice line. Depending on the strength of
the gaseous transport mechanisms the position of the ice line in our model can
change by up to 10 AU and consequently, the temperature at that location can
range from 21 K to 23 K.
