Abundances of Iron-Group Elements in Planetary Nebulae and Consequences for Chemical Enrichment

We have developed a method for determining elemental Fe-group abundances in planetary nebulae using an infrared emission line of Zn, the least refractory Fe-group species. Many planetary nebulae, particularly those of the Milky Way's thick disk and bulge, display subsolar [Fe/H] (as inferred from Zn) although their abundances of a elements such as O, S, and Ar are nearly solar. We discuss the implications for determining enhancements of species synthesized by the progenitor star during the AGB (e.g., s-process products), and for galactic chemical evolution in view of the metallicity dependence of AGB nucleosynthetic yields.