Fig. 4. Evolution of abundance profiles in the Milky Way disk, in the framework of the model presented in Sect. 2 and with the WW95 metallicity dependent yields. Curves show results at 2, 4, 9 and 13.5 Gyr, respectively (as indicated in the lower right panel). Because of the metallicity dependence of the yields, some elements (N, Al) have steeper abundance profiles than e.g. O, at all times. This is also the case for Fe, but the reason is its production mostly by SNIa. C and N are underproduced with respect to their solar system values, because yields from intermediate mass stars are neglected in this calculation. Metallicity dependent massive star yields from M92 considerably improve the situation concerning carbon (see Fig. 7), but not nitrogen. Solar abundances () were taken from Grevesse & Sauval (1998).