Trends of the derived metal abundances with effective temperature. Each panel shows the inferred abundances of C, N, O, Mg, and Si as a function of T_eff for the analysed sample. The error bars correspond to the 68% credible intervals from the posterior distributions. A mild decrease in O abundance toward higher T_eff is visible, consistent with the limitations of the current O II model atom at high ionisation stages (see text); no significant trends are found for the other elements. The dash-dotted line marks the CAS value, and the dashed line indicates the median of the derived abundances in each panel.