Time-dependent optical depth. Top: AGN light curve. The thick lines show the times for which ion abundances are shown (see below). The thin lines show the times corresponding to the absorption spectra in Fig. 9. Bottom, first and second row: Selected ion abundances (see legend) respectively for oxygen and iron as a function of N_H. The left and right panels correspond to t = 5, 16 ks. log() = 10 in all cases.