  The broad absorption lines (BALs) of QSOs indicate abundances of heavy
elements, relative to hydrogen, that are 1 to 2 orders of magnitude higher than
the solar values. In at least one QSO, an especially large enhancement of
phosphorus is observed. These abundances resemble those in Galactic novae, and
this suggests that novae may produce the BAL gas. The needed rate of nova
outbursts may come from single white dwarfs that accrete gas as they pass
through a supermassive accretion disk around a central black hole.
