  The thermodynamic structure of protoplanetary discs is determined by dust
opacities, which depend on the size of the dust grains and their chemical
composition. In the inner regions, the grain sizes are regulated by the level
of turbulence (e.g. $\alpha$ viscosity) and by the dust fragmentation velocity
that represents the maximal velocity that grains can have at a collision before
they fragment. Here, we perform self-consistently calculated 2D hydrodynamical
simulations that consider a full grain size distribution of dust grains with a
transition in the dust fragmentation velocity at the water-ice line. This
approach accounts for the results of previous particle collision laboratory
experiments, in which silicate particles typically have a lower dust
fragmentation velocity than water-ice particles. Furthermore, we probe the
effects of variations in the water abundance, the dust-to-gas ratio, and the
turbulence parameter on the disc structure. For the discs with a transition in
the dust fragmentation velocity at the water-ice line, we find a narrow but
striking zone of planetary outward migration, including for low viscosities. In
addition, we find a bump in the radial pressure gradient profile that tends to
be located slightly inside the ice line. Both of these features are present for
all tested disc parameters. Thus, we conclude that the ice line can function
both as a migration trap, which can extend the growth times of planets before
they migrate to the inner edge of the protoplanetary disc, and as a pressure
trap, where planetesimal formation can be initiated or enhanced.
