In this example, the results of MIN3P are compared to those of MULTIFLO for an acid mine drainage problem described in detail by Lichtner (1996). Acid mine drainage results when oxidizing water infiltrates through mine waste containing sulphide minerals, for example pyrite (FeS2). The oxidation of pyrite produces iron oxide and sulphuric acid, mobilizing heavy metals and potentially resulting in environmental contamination (Lichtner, 1996).
Figure 1 shows the a breakthrough curve of pH at 20 m depth plotted against time, comparing MIN3P and MULTIFLO results. It takes approximately 30 years for the acid plume to reach a depth of 20m.
In Figure 2, the spatial pH profile is shown for both MIN3P and MULTIFLO.
The corresponding O2(g) concentration plotted for different times is shown in Figure 3 and shows a decrease with depth as pyrite is oxidized.
The pyrite dissolution rate for the parallel reaction pathways is shown in Figure 4.
Mineral volume fractions are shown in Figures 5 and 6 for elapsed times of 25 and 50 years. Pyrite is oxidized with precipitation of ferrihydrite, jarosite and jurbanite.
Lichtner, P.C. 1996. Modeling reactive flow and transport in natural waters. Proceedings of the Rome Seminar on Environmental Geochemistry. Castelnuovo di Porto, May 22-26, 1996. Pacini Editore. pp 5-72.