GROUNDWATER FLOW AND MULTI-COMPONENT REACTIVE TRANSPORT SIMULATION OF ACID MINE DRAINAGE AT A FORMER MINE SITE

Abstract

Contamination of groundwater resources due to Acid Mine Drainage (AMD) is one of the
severest environmental problems. Understanding complex geochemical processes responsible for the
generation of AMD within the mine waste deposits is imperative for effective management and remediation of
contaminated mine sites. A multi-component reactive transport simulation is developed based on PHT3D to
simulate the geochemical evolution of AMD at the Rum Jungle Mine site that has undergone a long history of
groundwater contamination. The reactive transport simulation utilized hydraulic head distribution obtained
from MODFLOW based calibrated flow model. Geochemical processes considered for the reactive simulation
were conceptualized based on previous geochemical characterization and the contaminant of concerns were
limited to copper, iron, manganese, aluminum, zinc, and pyrite minerals considering their environmental
significance. The simulation results showed that the simulated plume followed mobility pattern dominated by
oxidation of sulfide minerals resulting in AMD and subsequent escalation in the concentration of dissolved
metals. Simulated and observed concentration for different reactive species appeared to be in a similar range
implying reasonable approximation of the physical system. The detailed calibration of reactive transport
simulation is restrained by uncertainties associated with aquifer heterogeneity, sparsity in available
information, and inaccurate understanding of the geochemical processes.