The surface-related emission properties of mesoporous silica are investigated by changing the environment surrounding the silica surface, that is by filling the pores of the transparent matrix with different media such as air and nitrogen, or under high vacuum conditions. The interaction of the emitting surface centers with the filling media induces large modifications on the surface of silica matrices and modifies the optical features of the emitting centers. The aim of the paper is to assign the origin of the gathered UV and visible emissions: the modifications induced by the different treatments support the involvement of OH species in the formation of the surface centers responsible of both the emissions and can be rationalized within the framework of two different dehydration reaction schemes previously proposed.