Conceptual Model Of Mining Tailings Columns For Reactive Contaminant Transport Experiments.
Presenter: Xenia De Gracia1
Advisor(s): Dr. Jon Chorover
1Department of Hydrology and Atmospheric Sciences, University of Arizona
Sulfidic mining tailings deposited more than 50 years ago, a consequence of mining activities developed throughout the Western United States during the last century, possess minerals that host toxic metal(loids), which can be mobilized in the vadose zone. Sulfide mineral oxidation reactions in the surface tailings, where the mineral enters in contact with water and oxygen, create what is known as acid mine drainage. Depending on the pore size of the media and the minerals residing in the tailings, these redox reactions can influence the fate of toxic metal(loid)s by altering the sorptive affinity of tailings particle surfaces, and the speciation of the sorbing metal(loid)s themselves. As a result, these contaminants can be adsorbed in the vadose zone, or they can be leached to the adjacent layers and even get to aquifers. To analyze mineral reactivity and hydrodynamic properties of mine tailings and their effects on metal(loid) transport, we designed a conceptual model of tailing columns that could represent the system and the environmental conditions by applying concepts including soil-water characteristic curves, breakthrough curves, mineral speciation, and analytical chemistry. These columns are being developed for two sulfide ore tailings sites with different climatic conditions. The first one derives from high humidity and low temperatures (Mammoth, Montana), and the other one derives from a very arid and warmer site (Tybo, Nevada). Column design includes the installation of sensors for soil moisture content, oxidation-reduction potential, and samplers for pore-water element composition. The data collected through this experiment will provide information on how the tailing's physical and geochemical properties (as driven by environmental conditions) can directly affect the hydrodynamics, reactivity, sorption processes, and contaminant transport.