FIG. 5. (A) Chlorofluorocarbon and SF6 concentrations measured in August 2001 samples from the Central High Plains rangeland site CNG (symbols) compared with simulated profiles (lines) for porosity, moisture content, and tortuosity data shown in Table 2; and (B) measured N2O profiles compared with the simulated profile assuming that steady 0.17 kg N2O-N ha–1 yr–1 production occurs in the top 1 m of the profile. X in line represents mean and range of groundwater equivalent equilibrium concentration in water-vapor-saturated air (GW EEC).