  Plausible ratios of deuterium to hydrogen D/H as a function of metallicity,
time, and redshift are investigated. Guided by the heavy element abundance
patterns observed locally in Galactic dwarf stars and at large redshift in
quasi-stellar object absorption line systems, empirical evolution of the
relative abundance ratios Li/D, B/D, N/D, O/D, and F/D for QSO absorption line
systems are given for the possible evolutionary patterns in D/H. Shortened
abstract.
