Mean Rosseland opacity values for the disc that includes the BOD distribution (top) and the MRN (bottom). These opacities correspond to the discs with the grain size distributions which were presented in Figs. 5 and 6. The highest opacity values are found at the iceline transition (gray band in the right plots). Moving outwards, the disc gets colder and the opacity of the disc decreases. The light blue line is the location where the vertically integrated optical depth reaches unity (τ = 1), so it divides the disc in the optically thick lower region and the optically thin upper region. Above this line, the opacities decrease due to the efficient cooling of the disc. The uppermost layers show increased opacities caused by the direct stellar heating, which increases the temperature. The same gradients can be seen in the temperature plots (right).