  We use the time-dependent photoionization and dust destruction code developed
by Perna & Lazzati (2002) to study the time evolution of the medium in a dusty
gaseous cloud illuminated by a bright central source that sets on at time zero.
We study the case of a bright source, which lasts for a time scale much smaller
than the recombination and dust creation time scales. For this reason an
equilibrium is never reached. We show that the presence of dust and its
properties, such as its composition, can have a big effect on the time scale
for the evaporation of the soft X-ray absorption, in particular for ionizing
sources with hard spectra. We discuss the profile of evaporation of the soft
X-ray absorbing column, as well as how the apparent ionization state of the
cloud evolves in time. We finally consider the apparent metallicity of the
cloud that is left behind as a function of the cloud and ionizing source
properties.
