Vertical column density of chemical species. With the exception of the bottom row, the left column shows the gaseous species and the left column the frozen species. the last row shows the ions HCO⁺ (left) and N₂H⁺ (right). The reference model Z1 (solid black line), the model with only an elemental abundance reduction (dashed red line), the model with only dust-to-gas reduction (dotted blue line), and the Z01 (solid green line) show the effect of the two modifications done in this study separately.