Evolution of the dust over time in the protoplanetary disc. The different colours represent different distances to the star. (a): Pebble flux and flux ratio as a function of time around a star with a solar mass and composition. The fragmentation velocity here was set to 2 m s⁻¹. The flux ratio starts at a moderately high value of ~0.015 but decreases rapidly after ~10⁵ yr. The sharp increase in pebble flux and flux ratio at 1 Myr is caused by the CO₂ iceline which is travelling inwards due to the decreasing luminosity of the star. (b): Stokes number as a function of time for the same distances as in the top panel. The Stokes number increases fast in the inner region of the disc, growing to 0.02 before 10³ yr. The size of the dust is mostly regulated by fragmentation either due to turbulence or differential radial drift. Only in the outermost regions of the disc is the growth of the dust slow enough for the Stokes number to be drift-limited.