  We introduce a simple and efficient algorithm for diffusion in smoothed
particle hydrodynamics (SPH) simulations and apply it to the problem of
chemical mixing. Based on the concept of turbulent diffusion, we link the
diffusivity of a pollutant to the local physical conditions and can thus
resolve mixing in space and time. We apply our prescription to the evolution of
an idealized supernova remnant and find that we can model the distribution of
heavy elements without having to explicitly resolve hydrodynamic instabilities
in the post-shock gas. Instead, the dispersal of the pollutant is implicitly
modelled through its dependence on the local velocity dispersion. Our method
can thus be used in any SPH simulation that investigates chemical mixing but
lacks the necessary resolution on small scales. Potential applications include
the enrichment of the interstellar medium in present-day galaxies, as well as
the intergalactic medium at high redshifts.
