Short-Range Atmospheric Dispersion of Carbon Dioxide

We present a numerical study aimed at quantifying the effects of concentration-dependent density on the spread of a seeping plume of CO₂ into the atmosphere such as could arise from a leaking geologic carbon sequestration site. Results of numerical models can be used to supplement field monitoring estimates of CO₂ seepage flux by modelling transport and dispersion between the source emission and concentration-measurement points. We focus on modelling CO₂ seepage dispersion over relatively short distances where density effects are likely to be important. We model dense gas dispersion using the steady-state Reynolds-averaged Navier-Stokes equations with density dependence in the gravity term. Results for a two-dimensional system show that a density dependence emerges at higher fluxes than prior estimates. A universal scaling relation is derived that allows estimation of the flux from concentrations measured downwind and vice versa.