On the Start Up or Initial Phase of Linear Mass Transport of Chemicals in a Water saturated Sorbing Porous Medium. I

Most researchers in the field of mass transfer of chemicals in sorbing porous media (includes miscible displacement, convective dispersion or “leaching”, straight diffusion, etc.) assume, for mathematical convenience, a simple Dirac δ or a rectangular pulse initial distribution of chemical. In actual practice, neither of these forms seems to occur. To better understand the initial phase or prelude phase to a “leaching” experiment, we have developed a rather general convective-diffusive-sorbtive dispersion model for the mass transport of chemicals in a porous medium such as soil or sandstone. The method of solution of the resulting linear integro-differential equation of transport is that of classical Laplace transforms. The free and sorbed phase distributions are then obtained as simple convolution integrals. A typical example is included to illustrate the distributions obtained.