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Institut für Wasserbau - IWS

Selected Topics and International Network Lectures

16:00 Uhr
Prof. Philip Binning, Environment & Resources Technical University of Denmark

Reactive Gas Transport in the Unsaturated Zone

Pyrite oxidation in unsaturated mine waste rock dumps and acid sulphate soils is limited by the supply of oxygen from the atmosphere. Oxygen transport through the subsurface has long been considered to be driven by diffusion and models have generally been based on such an assumption. However, oxygen comprises 23.2% by mass of dry air and when oxygen is consumed at depth in the unsaturated zone a pressure gradient is created between the reactive zone and the ground surface causing a substantial advective air flow into the subsurface. To determine the balance between advective and diffusive transport, a one-dimensional unsaturated zone gas transport model is developed. The two component mass balance model includes advection, diffusion and dispersion in oxygen and nitrogen gas.