Atmospheric transport over open-pit mines: The effects of thermal stability and mine depth

Abstract

A key difficulty in air pollution dispersion modeling and quantifying fugitive emission fluxes of pollutants from open-pit mines is that the meteorological fields for such complex terrains cannot be reliably predicted using simplistic surface layer theory. In this study, transport phenomena over a shallow (100 m) and a deep (500 m) synthetic mine are predicted under thermally unstable, neutral, and stable conditions using CFD modelling. The skimming flow is only predicted under the neutral case, while more complex flow patterns emerge otherwise. Under the unstable case, the shallow and deep mines induce enhanced mixing downstream of the mine, resulting in substantial vertical plume transport and dilution of the pollutants released from the mine. Under the stable case, the plume from the shallow mine is restricted to the surface layer downstream of the mine. However, under the stable case, the plume from the deep mine rises into the substantial portion of the boundary layer due to formation of a standing wave over and inside the mine. The results suggest that the CFD model can predict transport phenomena over open-pit mines reliably, so that the meteorological fields may be incorporated in operational models to improve accuracy of their predictions. • CFD is used to study atmospheric transport phenomena for open-pit mines under different mine depth and thermal stability conditions. • Skimming flow occurs for the neutral case, while enhanced mixing of passive scalar, released from the mine surface, occurs for the unstable case. • Under stable condition, a shallow surface layer is predicted for the shallow mine, while a deep standing wave is predicted for the deep mine. • Such accurate meteorological predictions can be incorporated in operational air quality and emission flux models for open-pit mines.