  We combine UV spectra obtained with the HST/GHRS echelle, IMAPS, and
Copernicus to study the abundances and physical conditions in the predominantly
ionized gas seen at high (-105 to -65 km/s) and intermediate velocities (-60 to
-10 km/s) toward zeta Ori. We have high resolution (FWHM ~ 3.3-4.5 km/s) and/or
high S/N spectra for at least two significant ions of C, N, Al, Si, S, and Fe
-- enabling accurate estimates for both the total N(H II) and the elemental
depletions. C, N, and S have essentially solar relative abundances; Al, Si, and
Fe appear to be depleted by about 0.8, 0.3-0.4, and 0.95 dex, respectively.
While various ion ratios would be consistent with collisional ionization
equilibrium (CIE) for T ~ 25,000-80,000 K, the widths of individual
high-velocity absorption components indicate that T ~ 9000 K -- so the gas is
not in CIE. Analysis of the C II fine-structure excitation equilibrium yields
estimated densities (n_e ~ n_H ~ 0.1-0.2 cm^{-3}), thermal pressures (2 n_H T ~
2000-4000 cm^{-3}K), and thicknesses (0.5-2.7 pc) for the individual clouds. We
compare the abundances and physical properties derived for these clouds with
those found for gas at similar velocities toward 23 Ori and tau CMa, and also
with several models for shocked gas. While the shock models can reproduce some
features of the observed line profiles and some of the observed ion ratios,
there are also significant differences. The measured depletions suggest that
\~10% of the Al, Si, and Fe originally locked in dust in the pre-shock medium
may have been returned to the gas phase, consistent with predictions for the
destruction of silicate dust in a 100 km/s shock. The near-solar gas phase
abundance of carbon, however, seems inconsistent with the predicted longer time
scales for the destruction of graphite grains.
