THE VARIATION OF ABUNDANCES IN PLANETARY-NEBULAE WITH HEIGHT ABOVE THE GALACTIC PLANE

In a sample of 94 planetary nebulae of the Galactic disk we find a sys tematic decrease of the abundances of He, N, O, S, and Ar with height above the Galactic plane, and also with radial velocity. Over an inter val of 3 kpc the abundance of O, S, and Ar decrease by 0.1 ... 0.2 dex . This value is in good agreement with the predictions of an empirical model for the chemical and kinematical evolution of the disk, based o n relations and constraints of the solar neighbourhood. The radial mig ration of the progenitor stars, caused by the velocity dispersion incr easing with age, is found to be quite important for the vertical metal licity profile.