Phytostabilization of Mine Tailings in the Southwestern United States: Plant-Soil-Microbe Interactions and Metal Speciation Dynamics

Background
Many mine tailings piles are barren or have minimal vegetation due to metal toxicity and low pH and thus are vulnerable to wind and water erosion. Phytostabilization has been proposed as an alternative economical remediation strategy to stabilize the metal contaminants and prevent human and animal exposure resulting from particle suspension (dust) in the atmosphere or dissolution in ground and surface waters. Little information is available on the effect of organic matter addition, plant establishment, and the evolution of associated microbial communities on metal bioavailability, solubility and speciation.

Plants (Atriplex lentiformis) used for phytostabilization.

Objectives
1. Investigate whether the specific selection of metal- and drought-tolerant native plant species in conjunction with the controlled use of a seed inoculum developed from indigenous plant growth promoting bacteria can minimize the requirement for organic matter amendment and irrigation.

2. Monitor the bioavailability, speciation, and phase distribution of contaminating metals in the plant rhizosphere in both greenhouse and field trials in order to assess whether revegetation results in a permanent reduction in site toxicity.

3. Investigate the effects of specific root-microbe-tailings associations on the local biogeochemistry and metal speciation of the rhizosphere in order to identify mechanisms involved in phytostabilization and detoxification at the micrometer and submicrometer scale.


Field Trial Sites and Descriptions

Phytostabilization of Neutral Mine Tailings within the San Pedro River National Conservation Area in southern Arizona

Phytostabilization of Acidic Mine Tailings in Aravaipa Valley, Graham County, Arizona-Klondyke State Superfund Site

Contact
Raina Maier
rmaier@ag.arizona.edu
(520) 621-7231