A scaling law of interstellar depletions as a tool for abundance studies of Damped Ly alpha systems

An analytical expression is presented that allows dust depletions to be estimated in different types of interstellar environments, including Damped Ly alpha systems. The expression is a scaling law of a reference depletion pattern and takes into account the possibility that the dust chemical composition may vary as a function of the dust-to-metals ratio and of the intrinsic abundances of the medium. Preliminary tests and applications of the proposed scaling law are briefly reported.