  We present an abundance analysis of a sample of 33 hydrogen-rich (DA) white
dwarfs. We have used archival high-resolution spectra to measure abundances of
calcium, magnesium and iron in a set of 30 objects. In addition, we present
preliminary calcium abundances in three new white dwarfs based on
low-dispersion spectra. We investigate some abundance ratios (Mg/Ca, Fe/Ca)
that may help uncover the composition of the accretion source.
