Radial abundance profiles of volatile C, O, and N in the disc at the time of planetesimal formation (10⁵ yr), 10³ years later, and at 1 Myr, shown for the inheritance-low scenario with 0.1 μm-sized grains. The light blue dashed line shows the gas-phase abundance, while the blue dash-dotted line represents the ice-phase abundance (which, for C, includes the contribution from semi-volatile refractory organics). The red solid line is the total abundance (gas + ice), initially set to the protosolar value and reduced by the meteoritic abundance. The plot illustrates the evolution of elemental abundances due to mass transport during viscous disc evolution.