How Massive Are BALQSO Winds

We are involved in a program to derive properties of broad absorption line (BAL) winds in quasars using combined UV and X-ray observations. A major obstacle is large uncertainties in the derived BAL column densities because of partial coverage of the background light source. In this preliminary report, we circumnavigate those uncertainties by making a simple assumption -- that the relative metal abundances are roughly solar. In this case, the PV 1118,1128 multiplet should have at least 500 times lower optical depth than CIV 1549,1551. Nonetheless, a PV BAL is present in at least half of the well-measured BALQSOs we studied. We conclude that the strong lines of abundant species like CIV are typically very optically thick. The total BAL column densities are N_H > 10^22 cm^-2 (for solar overall metallicity), and they might be comparable to the X-ray absorbers, of order 10^23 cm^-2, if the BAL gas is sufficiently ionized. If the column densities in outflowing BAL gas are, in fact, as large as the X-ray absorbers, it would present a serious challenge to models of radiatively-driven BAL winds.