Impacts of Amendments to Promote Mine Revegetation: Relationships Among Effects on Tailing Chemistry and Douglas fir Health and Needle Chemistry

Past mining activities in the United States have left a legacy of heavy metal contaminated soils that requires remediation to allow for increased phytostabilization and reduced water and soil pollution. Of special concern to EPA’s Region 10 is the Formosa mine superfund site located in south-central Oregon.  This site has a large area of acidic mining tailings where it is difficult to establish vegetation.  We evaluated the effects of amending the tailings with lime, biochar, biosolids, and locally-sourced microbes (LSM) on tailing chemistry, plant establishment and response. This research evaluated plant response data across tailing amendments for both greenhouse and field studies with Douglas fir (Pseudotsuga menziesii). ”Heat maps”, based on Pearson correlation coefficients were used to evaluate relationships among tailing chemistry, plant health and needle element parameters.  The analysis indicated that in both the greenhouse and field studies, seedling survival was positively related with an increase in tailing pH, decreased electrical conductivity, and decreased availability of metals (Al, Cu, Fe, Mn, Zn) concentrations.  Seedling health was positively related to needle Al and Cu concentrations in the field study, but health/needle element concentrations were less strongly correlated in the greenhouse study.  Tailing and needle elements showed similar patterns of correlation in both the field and greenhouse studies. This study highlights the potential for amendments developed under EPA ORD and USDA ARS biochar research programs to enhance plant growth by improving soil chemistry, thus increasing the potential for success of vegetation reestablishment to degraded mine soils in Superfund sites across the United States.

Impact/Purpose

Past mining activities in the United States have left a legacy of heavy metal contaminated soils, which need to be cleaned up to allow for growth healthy plants on the site to promote phytostabilization of the land, thus preventing water and soil pollution. Of special concern to EPA’s Region 10 is the Formosa mine superfund site located in south-central Oregon, which has a large area of mine tailings on the soil surface where it is difficult to establish vegetation.  We evaluated the impact of tailings amendments [lime, biochar, biosolids, and locally-sourced microbes (LSM)], on tailing chemistry and plant responses. This research evaluated data across amendment treatments for both a greenhouse and field study with Douglas fir (Pseudotsuga menziesii) using “heat maps” based on Peason correlation coefficients to evaluate relationships among tailing chemistry, plant health and needle element parameters.  The analysis indicated that in both the greenhouse and field studies, seedling survival was positively related with an increase in tailing pH, decreased electrical conductivity, and decreased availability of metals (Al, Cu, Fe, Mn, Zn) concentrations.  Seedling health was positively related to lower needle Al and Cu in the field, but health/needle element concentrations were less correlated in the greenhouse.  Tailing and needle elements showed similar patterns of correlation in both the field and greenhouse studies. This study highlighted the potential for amendments developed under EPA ORD and USDA ARS biochar research programs to enhance plant growth by improving soil chemistry, thus increasing the potential for success of vegetation reestablishment.  This will assist EPA efforts to restore degraded mine soils at Superfund sites across the United States.

Citation

Olszyk, D., V. Manning, M. Johnson, Mike Bollman, T. Shiroyama, M. Nash, K. Trippe, D. Watts, AND J. Novak. Impacts of Amendments to Promote Mine Revegetation: Relationships Among Effects on Tailing Chemistry and Douglas fir Health and Needle Chemistry. Annual Meeting of Society of Environmental Toxicology and Chemistry, OR, Portland, November 14 - 18, 2021.