One-dimensional, radial structure in the HD 169142 disk. Vertical brown shaded regions represent the dust rings. Left: DCO⁺ radial column density (dotted blue) calculated from Eq. (1) using the DCO⁺ the radial intensity profile (see Fig. 2) and the midplane gas temperature of the optimized DALI model (dot-dash red) as the T_ex profile. The gas surface density profile (dashed green) was used to derive the DCO⁺ radial abundance. Right: radial abundance structure of DCO⁺ with respect to H₂. The blue shaded region represents 1σ errors on the abundance.