Superfund Research Program
Revegetation of Mining Wastes in Arid and Semiarid Environments: Plant-Microbe-Metal Interactions and Fertility Island Effects
Project Leader: Raina M. Maier
Co-Investigators: Jon Chorover, Julie W. Neilson, Francisco E. Molina-Freaner (Universidad Nacional Autónoma de México), Mark D. Barton
Grant Number: P42ES004940
Funding Period: 2005-2020
Legacy mine tailings with high toxic metal content are a significant health risk to nearby populations and require novel and economical remediation approaches. University of Arizona Superfund Center Project 3 is investigating phytostabilization technology, direct planting of seeds into compost-amended tailings, as a low input remediation strategy to stabilize both metal(loid)s and mine tailings particulates. This project combines phytostabilization at the field scale with complementary greenhouse experiments to examine plant-microbe-metal interactions during the phytostabilization process. Results show that a robust plant cover can be established that suppresses dust emissions from the tailings (Gil-Loaiza et al., 2016; 2018). Key findings from this research include information relevant for management of such legacy sites. For example, a single compost amendment helped control pH and create a neutrophilic, beneficial microbial community in plant-rooting zones. However, after several years, areas that were subject to erosion of compost began a re-acidification process and in these areas tailings became dominated by an increasingly acidiphilic microbial community through a successional process (Hottenstein et al., 2019; Honeker et al., 2019). These results suggest that re-application of compost or an alternate buffering material may be required in regions susceptible to re-acidification. Further, analysis of the microbial community suggests there are sensitive components of the community that can act as biomarkers to suggest optimal times for reapplication of compost. The effect of phytostabilization on arsenic mobilization was also investigated. While subsurface mobilization of arsenic was observed, there was not a difference between phytostabilized treatments and controls (Hammond et al., in review).