Mass flux of oxygen (stored in water ice, solid lines) and carbon (in gas-phase CH₄, dashed lines) at 1 au as a function of time, for a disc with a gap carved by a 100 M_⊕ planet at 10 au. As in Fig. 11, we focus on simulations with δ_turb = 10⁻⁴ and varying viscosity, as these sample the different leakiness regimes well. We see that the pebble flux is always above the flux of C-rich gas, meaning that it is challenging for outer dust traps to result in inner disc gas-phase C/O above unity.