Evaluating dual-domain models for upscaling multicomponent reactive transport in mine waste rock

Reactive transport models have proven abilities to simulate the quantity and quality of drainage from mine waste
rock. Tracer experiments indicate the presence of fast and slow flow regimes in many heterogeneous waste-rock
piles. Although multidomain models have been developed specifically for systems with such distinctive hydrodynamics,
there have been limited applications of multidomain reactive transport models to simulate composite
drainage chemistries from waste-rock piles to date. This work evaluated the ability of dual-domain multicomponent
reactive transport models (DDMRTMs) to reproduce breakthrough curves of conservative (chloride) and
reactive (molybdenum) solutes observed at a well-characterized experimental waste-rock pile at the Antamina
Mine, Peru. We found that the DDMRTM simulations quantitatively matched eight-year-long records of conservative
transport through the waste-rock pile when parameterized mainly with field-measured properties
obtained from the site and limited calibration. The DDMRTM model also provided a reasonable match to field
observations of the reactive solute. The limited calibrated parameters are physically realistic, corroborating the
ability of these multidomain models to reproduce the complex reactive-transport processes governing polluted
rock drainage from large-scale waste-rock piles.