MIN3P Verification Example: Acid mine drainage generation and
attenuation (comparison of MIN3P to MULTIFLO)
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.
References:
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.