Information provided by Sn-119(2+) Mossbauer probe ions, located on surface sites of anatase-type TiO2 microcrystals exposed, at room temperature, to a H2S/H-2 mixture, has permitted to conclude that the interaction of H2S molecules with the substrate surface leads to the dissociation of a fraction of the absorbate molecules. This gives rise to the formation of elemental sulfur which oxidizes the neighboring Sn2+ ions, the produced Sn4+ ions being found coordinated only by S2- anions. Subsequent exposure to ambient air is shown to result in the oxidation of 52- ions, yielding both S and SO42-like species, with concomitant stabilization of Sn4+ ions in coordination polyhedra where they are surrounded by only oxygen anions. (C) 2014 Elsevier B.V. All rights reserved.