Non-equilibrium reactive transport modeling of acid mine drainage in subsurface water.

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Someswaran Ravi, Suresh Kartha

Thursday 2 july 2015

12:15 - 12:30h at Asia (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment

Parallel session: 11G. Environment - Impact

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The acidified water that comes out of the abandoned and active mine sites is commonly referred as acid mine drainage (AMD), and is a great threat to the surface and subsurface hydrological environment. This paper attempts to describe the mathematical modeling of reactive transport of AMD through the subsurface environment. The liquid phase in the subsurface porous media is assumed to exist in two-domains (dual porosity) – mobile and immobile. The reactive component of the transport mechanisms are incorporated only in the mobile domain as we assume the AMD source to be in more interaction with the mobile liquid. Ferrous and ferric ions are the major pollutant species in AMD and the reactive transport model, here analyses ion-exchange of ferrous ion with sodium. The US-EPA developed finite-element software FEMWATER, is modified in this paper to account for ion-exchange chemical reaction between solid and mobile water and first order mass transfer interactions between mobile and immobile water. The model is used to study two-dimensional cases and the results suggested that retardation of ferrous ion concentration plume is more due to ion-exchange process, whereas the plume moves at a faster pace when the mass transfer between mobile and immobile water is significant.