University of Arizona
Superfund Research Program
Phytostablization of Mine Tailings in the Southwestern United States: Plant-Soil-Microbe Interactions and Metal Speciation Dynamics
Mine tailings disposal sites are prevalent in arid and semiarid regions throughout the world including the US Southwest. Unreclaimed mining wastes generally remain unvegetated for tens to hundreds of years, and exposed tailings can spread over vast areas via wind and water erosion. A combination of factors, including metal toxicity, low organic matter, acidic pH, high salinity, extreme temperatures, low precipitation, and severely stressed microbial communities contribute to this lack of vegetation. For such tailings, wind-borne dispersion is an important exposure route for nearby communities and environmentally sensitive areas. Specifically, tailings are a significant source of air pollution in the form of particulates <10 pm (PM10) and <2.5 Âµm (PM2.5). Exposure to these particulates has consequences for respiratory and other diseases even in the absence of toxic metals. The fact that many sites additionally contain toxic metals exacerbates the human health impact. A cost effective remedial technology for such sites is phytostabilization, the establishment of a permanent vegetative cover that does not accumulate metals into plant shoot tissues. While of great promise, there is currently little documentation of this technology in accessible scientific literature.
The overall goal of this project is to determine how plant-microbe-metal interactions affect the short- and long-term requirements for, and mechanisms of, revegetation of arid mine tailings and to identify the biological and physico-chemical markers that indicate successful remediation. This project focuses on examining field application of phytostabilizafion while retaining several key basic research questions identified as important for success in the field. Specific objectives include:
- to translate phytostabilization technology from the greenhouse to the field;
- to determine if a multi-variate, spatial analysis of initial biophysico-chemical characteristics of mine tailings can serve as a useful predictor of phytostabilization success;
- to evaluate the progress toward development of a "healthy" soil as a function of time following revegetafion of mine tailings; and
- to determine the influence of microbial inocula on phytostabilization including plant biomass production and development of the rhizosphere community.