  Acid mine drainage (AMD) is the outflow of acidic water from metal mines or
coal mines. When exposed to air and water, metal sulfides from the deposits of
the mines are oxidized and produce acid, metal ions and sulfate, which lower
the pH value of the water. An open limestone channel (OLC) is a passive and low
cost way to neutralize AMD. The dissolution of calcium into the water increases
the pH value of the solution. A differential equation model is numerically
solved to predict the variation of concentration of each species in the OLC
solution. The diffusion of Calcium due to iron precipitates is modeled by a
linear equation. The results give the variation of pH value and the
concentration of Calcium.
