Radon transport mechanisms in soils were studied to determine the dominant transport mechanism for Delaware county soils. In modeling the soil, it was assumed that is was homogenous and moisture-free. Two transport mechanisms were investigated, the transport of radon in the soil by molecular diffusion (assumed to be governed by Fick's law) and transport by pressure-induced flow or convection (assumed to be governed by Darcy's law). Following the previous work of W. E. Clements, a general transport equation was described which incorporated both diffusion and convection. In steady-state conditions, a closed-form solution was obtained for the concentration of radon in the soil interstices as a function of depth. Similarly, solutions were examined for transport by diffusion alone. Representative soil parameters were assigned and the diffusion fraction (the ratio of concentration due to diffusion to the concentration due to both diffusion and convection) was calculated. Referring to the work of A. B. Tanner, a radon availability number (RAN) was determined for the soils; the RAN value was a measure of the activity of radon per unit area. Analyses were also performed to determine the significance of pressure variations on calculated diffusion fractions and RAN values. For 99% of the acreage in Delaware county, the diffusion fraction was 0.95 or greater. Therefore, it was concluded that molecular diffusion is the dominant transport mechanism for the soils of Delaware county. / Department of Physics and Astronomy