Ni depletion factor versus Fe depletion factor in clump regions within PNe. Diamond shapes correspond to NGC 7009 values. All the clump abundances were calculated for T_e = 10 000 K and n_e = 1000 cm⁻³. Solid lines correspond to best-fit lines for different iron atomic data and fluorescent cases for nickel. The dashed line shows the best fit from DI16. Green and blue dots were estimated accounting for fluorescence (or lack thereof) in nickel using B15 atomic data. The pink and orange dots were derived with the TZ18 atomic data.