Element abundances of our sample objects in the Kiel diagram (panels from upper left to lower right: C, N, O, Si, P, and S). The abundances are illustrated with filled circles and squares for DAOs and DAs, respectively. The symbol size is proportional to the mass fraction of the respective element. The dashed symbols represent solar values (Asplund et al. 2009). The upper limits are marked with an upside triangle, which does not scale with the abundances.