by using only the main absorption component of the system;

$c$ : Error bar not reported by the author.

$d$ : Upper limit from Lipman (1995; thesis).

$e$ : Column densities from line profile fitting where all the lines are fitted simultaneously; the final choice of Lu et al (1995a) for O is \[O/H\]$>$ -2.99; metal abundance error bars include propagation of the N(HI) error.

     QSO           $z_{\rm abs}$       \[N/O\]      \[N/Si\]      \[N/S\]      \[Si/O\]      \[S/O\]      \[O/Fe\]      \[Si/Fe\]
  --------------- --------------- ------------ ------------- ------------ ------------- ------------ ------------- --------------
                                                                                                                   
  0000-26             3.3901             +0.36       $-$0.29           —          +0.65           —        $-$0.75        $-0.10$
                                                                                                                   
  1331+1700           1.7765             +0.08            —       $-$1.38            —         +1.46       $-$0.56             — 
                                                                                                                   
  2348-147            2.2794          $<-1.02$      $<-1.18$     $<-1.24$         +0.16        +0.22         +0.22          +0.38
                                                                                                                   
  2344+124 $^a$       2.5379           $-0.59$       $-1.14$     $>-1.32$         +0.55     $<+0.73$       $-0.59$          +0.13
                                                                                                                   
  1946+7658           2.8443          $<-0.61$      $<-1.10$           —          +0.49     $<+1.76$       $-0.24$          +0.25
                                                                                                                   

0.5 truecm

$a$ Values derived by using only the main absorption component

Ionization corrections and dust depletions
------------------------------------------

The neutral hydrogen in the DLA is optically thick to the ionizing radiation either from the intergalactic background or from starlight inside the DLA, and the abundances derived from species that have ionization potentials in excess of 13.6 eV do not require ionization corrections. This is the case of abundances derived from 