Panel a: abundance of CN in a 10^-2M_⊙, ψ = 0.3, h_c = 0.1 disk surrounding a T Tauri star. The location of the peak value is indicated with the green dot. The shape of the distribution of the outer high-CN-abundance region is representative for all the other models. The white line shows the τ = 0.5 contour of the CN (N = 3−2) emission line. The red line shows the dust τ = 1 layer at the same wavelength. The green dotted line indicates the location of the vertical CN abundance maximum for each radius. Panel b: CN (solid blue line) and HCN (cyan line) column densities calculated for the same model, plotted on a linear rather than logarithmic scale. The HCN column density was multiplied by 2 and is more radially concentrated than CN.