Critical Stokes number of particles that are affected by turbulent diffusion as a function of absolute Δ v∕c_s in the pressure bump and α. Particles with Stokes numbers lower than the critical value easily diffuse and can drift through a pressure bump. The black lines denote particles with Stokes numbers of 10, 1, 0.1, 0.01, and 0.001 from left to right. The white dots correspond to different planetary masses, where we have taken the maximum value of the pressure bump generated by the planet for simulations with different α. The planetary masses are marked with the white numbers next to the dots. The horizontal dashed black line markes our nominal α = 0.001.