Dispersive mixing has an important impact on the effectiveness of miscible floods. The main objective of this project is to perform experimental and computational studies to understand the basic mechanisms of dispersion and mixing at pore scale. The understanding will be used to develop an improved multi-scale model of dispersion and to optimize field scale displacements. Experiments were carried out to measure concentration histories in a sand-pack at a scale of the order of 100 microns using a simple two-electrode microprobe inserted into the column. We used the multi-physics modeling software FEMLAB to investigate mixing in two-dimensional porous media by solving the Navier-Stokes and convection-diffusion equations in the pore space. We have also begun investigating other approaches for numerical modeling - particle tracking and dynamical systems. The computational studies qualitatively support the experimental observations and explain the mixing mechanism inside the pore body. We continue to make progress toward creating a robust, miniature and inexpensive nitrate ion selective electrodes (ISE) by electropolymerizing pyrrole onto carbon fiber substrates in a nitrate solution (nitrate becomes the dopant ion).