Biochar and Other Amendments Promote Douglas fir Survival and Growth on Mine Tailings

In the western US, there are over 33,000 abandoned sites where heavy metal contaminated mine tailings contaminate local ground and surface water sources. At these sites, revegetation is required to prevent further erosion of heavy metal contaminated soils into nearby waters. However, successful growth of plants is often limited by degraded soil conditions, including low soil pH and associated high soil heavy metal concentrations, poor soil structure, diminished water holding capacity, limited soil fertility, soil carbon, and microbial activity. In a field study, we evaluated the effects of a mixture of amendments (lime, biosolids, biochar, locally effective microbes) on spoil pH and metal concentrations and subsequent impacts on injury, growth and needle elemental concentrations for Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] growing in mine spoil at the Formosa mine Superfund site in southwestern Oregon. Two years past amendment application, the spoil had a pH increase and lowered metal availability, resulting in enhanced seedling survival, growth, and needle N contents; while reducing needle heavy metal concentrations, such as Cu. This study indicates that biochar, along with lime and nutrients, can enhance tree seedling growth and affect needle elements in mine affected spoils.

Impact/Purpose

In the western US, there are over 33,000 abandoned sites where heavy metal contaminated mine tailings contaminate local ground and surface water sources. The EPA has regulatory authority, especially under Comprehensive Environmental Response, Compensation, and Liability Act (Superfund) to oversee cleanup of these sites; and responsibility to regions, states and local communities under the Office of Research and Development’s Safe and Healthy Community Research Program to develop new techniques to assist in this cleanup. Of special concern to EPA’s Region 10 is the Formosa mine superfund site in south-central Oregon, which has a large area of mine spoils (waste material from mining on the soil surface) where it is difficult to establish vegetation. At sites such as this, successful growth of plants is often limited by low spoil pH and associated high soil heavy metal concentrations, poor soil structure, diminished water holding capacity, limited fertility, soil carbon, and microbial activity. In a field study, we evaluated the effects of a mixture of amendments (lime, biosolids, biochar, locally effective microbes) on Formosa mine spoil pH and metal concentrations and subsequent impacts on injury, growth and needle elemental concentrations for Douglas fir [Pseudotsuga menziesii (Mirb.) Franco]. Two years past amendment application, the spoil had a pH increase and lowered metal availability, resulting in enhanced seedling survival, growth, and needle N contents; while reducing needle heavy metal concentrations, such as Cu. This study indicates that biochar, along with lime and nutrients, can enhance tree seedling growth and affect needle elements in mine affected spoils, providing immediately useful information to alleviate a mine spoil pollution problem in Region 10. More broadly, the study illustrated the potential for techniques developed under ORD’s biochar research program to enhance plant growth by improving soil chemistry, thus increasing the potential for success of vegetation reestablishment to degraded mine soils across the United States.

Citation

Olszyk, D., Mark G Johnson, Mike Bollman, M. Nash, K. Trippe, V. Manning, D. Watts, AND J. Novak. Biochar and Other Amendments Promote Douglas fir Survival and Growth on Mine Tailings. Annual Meeting of Society of Environmental Toxicology and Chemistry, Virtual, OR, November 15 - 19, 2020.