  We show that the mass of ionized gas in the Broad Line Regions (BLRs) of
luminous QSOs is at least several hundred Msun, and probably of order 10^3-10^4
M_sun. BLR mass estimates in several existing textbooks suggest lower values,
but pertain to much less luminous Seyfert galaxies or include only a small
fraction of the ionized/emitting volume of the BLR. The previous estimates also
fail to include the large amounts of BLR gas that emit at low efficiency (in a
given line), but that must be present based on reverberation and other studies.
Very highly ionized gas, as well as partially ionized and neutral gas lying
behind the ionization zones, are likely additional sources of mass within the
BLR. The high masses found here imply that the chemical enrichment of the BLR
cannot be controlled by mass ejection from one or a few stars. A significant
stellar population in the host galaxies must be contributing. Simple scaling
arguments based on normal galactic chemical enrichment and solar or higher BLR
metallicities show that the minimum mass of the enriching stellar population is
of order 10 times the BLR mass, or greater than 10^4-10^5 M_sun. More realistic
models of the chemical and dynamical evolution in galactic nuclei suggest that
much larger, bulge-size stellar populations are involved.
