A new approach to probing the atomic-scale surface chemistry of heterogeneous catalysts will be presented. The approach makes a direct connection between atomic-scale surface structures and macroscopic conductance measurements. We have applied this technique to gamma-alumina, a catalytic material that serves widely as a petroleum refining catalyst, as an active ingredient in cracking catalysts, and as a support material in automotive emissions control catalysts. A dual-charge-carrier model has previously been advanced to explain the observed nonlinear thermal dependence of surface conductance on gamma-alumina [M. Caldararu et al., Applied Surface Science, Vol. 181, (2001) p. 255.]. In this model, charge is carried across the surface by two independent types of atomic or molecular charge-carriers, each with different mobility. We have cast the dual-charge-carrier model into mathematical form. We then carried out first-principles calculations for various possible interactions of charge-carrier-species with the gamma-alumina surface. From these calculations we estimate the values of the energy parameters in the model. By comparing the values of these energy parameters as determined by first-principles calculations to those obtained by fitting the mathematical form of the model to experimental data, new insight is gained into the nature and transport of the charge-carrier species. The results support the hypothesis that the intrinsic hydrogen content and surface moisture of gamma-alumina provide a possible explanation of the observed thermal dependence of surface conductance.