Paper Title
Math Model of Grain Size Distribution Versus Radon Content of Wadi Arar, Kingdom of Saudi Arabia

Abstract
Comparing to other fractions, Coarse and fine sand is highly correlated with radon content with correlation coefficients of - 0.79 and 0.80 respectively. A polynomial of 3rd degree is the best math model representing the relation between the grain size content and it is correlated with radon content. At Coefficient of Determination, R2 equal to 82%, the relation between grain size of coarse and fine sand and radon contents is fitted with polynomials of 3rd degree. Radon content can be deduced depending on the grain size distribution instead of direct measurement using the polynomial model that created. At the radon point of view and for safety purpose, gravel, coarse and medium sand and silt and clay are the best material for construction because of the negative or very weak correlation between them. Keywords- grain size distribution, CR-39, Radon, soil classification, polynomial.