  We separately assess elemental abundances in AGNs' broad and narrow emission
line regions (BLR and NLR), based on a critical assessment of published results
together with new photoionization models. We find 1) He/H enhancements in some
AGN, exceeding what can be explained by normal chemical evolution and confirm
2) super-solar {\alpha} abundance, though to a lesser degree than previously
reported. We also reaffirm 3) a N/O ratio consistent with secondary production;
4) solar or slightly sub-solar Fe abundance; and 5) red-shift independent
metallicity, in contrast with galactic chemical evolution. We interpret 6) the
larger metallicity in the BLR than NRL in terms of an in situ stellar evolution
and pollution in AGN discs (SEPAD) model. We attribute: a) the redshift
independence to the heavy element pollutants being disposed into the disc and
accreted onto the central supermassive black hole (SMBH); b) the limited He
excess to the accretion-wind metabolism of a top-heavy population of evolving
massive main sequence stars; c) the super-solar CNO enrichment to the nuclear
synthesis during their post-main-sequence evolution; d) the large N/O to the
byproduct of multiple stellar generations; and e) the Mg, Si, and Fe to the
ejecta of type II supernovae in the disc. These results provide supporting
evidence for f) ongoing self-regulated star formation, g) adequate stellar
luminosity to maintain marginal gravitational stability, h) prolific production
of seeds and i) dense coexistence of subsequently-grown residual black hole
populations in AGN discs.
