Using Biochar and Soil Amendments for Plant Establishment in Mine Residuals at the Formosa Mine: A Case Study

Mining provides essential metals and minerals for a variety of societal needs and uses. At the same time, it can also be the cause of intensive and extensive environmental contamination from the residuals of mining. Management tools are needed to facilitate the stabilization/remediation of mining residuals using plants (phytostabilization) at both active and abandoned mine sites to reduce negative environmental impacts. Mining residuals are often acidic, laden with heavy metals, lacking adequate nutrients and physical conditions for plant growth, which are all challenging for establishing plant cover. We have had success using a systematic approach to define site-specific prescriptions using biochar in concert with other soil amendments to improve site conditions to facilitate native plant establishment on mine residuals. Our framework includes assessing site-specific limitations to plant establishment through laboratory analyses to evaluate pH, heavy metal contamination, nutrient availability, and soil physical attributes (e.g., particle size distribution, bulk density, water-holding capacity), followed by development of site-specific soil amendment prescriptions tailored to ameliorate the particular limitations present. Long-term incubation studies are conducted to: 1) determine the amount of lime required to restore soils to near-native pH, 2) evaluate the efficacy of various biochars on sorption and retention of plant-available metals and creation of desired soil physical attributes, 3) identify nutrient (N, P, K) levels, combinations, and sources (e.g., commercial fertilizer, municipal biosolids) optimal for plant growth, and 4) evaluate physical manipulations that may improve soil structure/water retention for plant growth (e.g., tillage, mulching). Plant germination and growth studies are conducted in growth chambers and/or greenhouses to evaluate the efficacy of various combinations of candidate amendments, and field trials are used to further demonstrate the effectiveness of selected amendment prescriptions in a site-specific environmental context. This presentation describes our working framework and uses our research at the abandoned Formosa Mine in southern Oregon as a case study to demonstrate the positive and negative aspects of the process we developed to revegetate an otherwise barren landscape.

Impact/Purpose

Mining provides essential metals and minerals for a variety of societal needs and uses. However, across the U.S. it is estimated that there are more than 500,000 abandoned mines. In the western U.S. alone 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. Management tools are needed to facilitate the stabilization/remediation of mining residuals using plants (phytostabilization) at both active and abandoned mine sites to reduce negative environmental impacts. The Formosa Mine site has served as a field laboratory for investigating the use of biochar and other soil amendments to revegetate what is otherwise an acidic, barren landscape. We have had success using a systematic approach to define site-specific prescriptions using biochar in concert with other soil amendments to improve site conditions to facilitate native plant establishment on mine residuals. Our framework includes assessing site-specific limitations to plant establishment through laboratory analyses to evaluate pH, heavy metal contamination, nutrient availability, and soil physical attributes (e.g., particle size distribution, bulk density, water-holding capacity), followed by development of site-specific soil amendment prescriptions tailored to ameliorate the particular limitations present. This study indicates that biochar, along with lime and nutrients, can enhance tree seedling growth in acidic mine tailings, providing immediately useful information to alleviate a mine tailings pollution problem in Region 10. More broadly, the study illustrates 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 mining impacted soils, spoils and tailings across the United States.

Citation

Johnson, Mark G, D. Olszyk, Mike Bollman, M. Storm, G. King, V. Manning, K. Trippe, K. Spokas, J. Ippolito, D. Watts, T. Ducey, G. Sigua, AND J. Novak. Using Biochar and Soil Amendments for Plant Establishment in Mine Residuals at the Formosa Mine: A Case Study. American Society of Agronomy Annual Meetings, Virtual, OR, November 09 - 13, 2020.