| Two dynamic mathematical models were developed to model acid mine drainage and the subsequent leaching of certain metals. The first model called PSCAMD was developed to model the performance of humidity-cell testing. Humidity-cell tests are accelerated weathering tests used to access the acid-producing potential of waste rock. The current version of PSCAMD includes the following special characteristics: (1) a complex reaction system consisting of 24 species and 19 reactions, (2) use of a shrinking-core model approach including the secondary minerals (precipitation), (3) one or two bacteria systems, (4) interstitial water inside the humidity cell which is treated as a variable, and (5) a PC Windows-based, user-friendly interface. The humidity-cell model matched experimental data for at least five species for five different rock samples over a period as long as 200 weeks.; The second model called AMD3D3PG is a three-dimensional, three-phase geochemical mathematical model describing acid mine drainage on a much larger scale, actual waste rock dump sites. The current version of AMD3D3PG focuses on the transport mechanisms that occur in waste rock dump sites under certain restricted conditions. Properties calculated simultaneously in AMD3D3PG include (1) temperature and reaction rates; (2) vapor, liquid, and capillary pressures; (3) vapor and liquid velocities under unsaturated conditions; (4) volume fractions of vapor, liquid, and solid phases; (5) relative permeabilities of vapor and liquid phases; (6) heat capacity, viscosity, density, and thermal conductivity of each phase; (7) diffusion of chemical species; and (8) concentration profiles of all species. A special algorithm, the plane-bounded method, was developed to set up a three-dimensional waste rock dump site. This algorithm also uses computer memory more efficiently. |
