Abstract:
Fugitive atmospheric emission of methane, a potent greenhouse gas with a 25-fold global
warming potential compared to CO2, from the natural gas industry has raised significant environmental
and health concerns during last few years. Migration of gases in soil is controlled by subsurface
conditions (e.g., heterogeneity) and their emission across the soil-atmosphere continuum is affected
by atmospheric boundary conditions (e.g., wind, temperature). A bench-scale experiment was
conducted in a wind tunnel coupled with porous media facility to investigate the effects of two nearsurface
(above ground) controls, wind (0.5 and 2.0 ms1) and temperature (24°C and 38°C), on
atmospheric concentration profiles of methane migrated from a point source. We used COMSOL
Multiphysics to simulate methane dynamics under the coupled temperature, pressure (wind) and
concentration-driven flow conditions, taking also into account the density-dependent flow. The results
show marked differences in atmospheric concentration boundary layer development under different
wind velocity conditions. A good agreement was observed between the measured and simulated
concentration profiles. Based on the permissible occupational exposure limits for methane, we further
discussed the potential effects of wind and temperature on controlling safe workplace atmospheric
conditions.
