Overview of designing biochars to improve soil health characteristics at two Superfund mine sites

Soil remediation of mine sites using biochars is a management option to possibly increase phytostabilization. Soil health characteristics at mine sites, however, can be complex because the soils may have multiple issues (e.g., acidification, heavy metal content, etc.) detrimental to plant growth. Under these circumstances, selection of an appropriate biochar to improve soil health may be confusing and cause erroneous biochar choices. It may be prudent to select a designer biochar with apriori properties tailored for particular soil health deficiencies. The USDA-ARS and US EPA are conducting research experiments to develop designer biochars for soil remediation at two Superfund sites including Formosa (near Riddle, Oregon) and the Tri-State (near Joplin, Missouri). Soil at the Formosa mine are acidic (pH < 3), are elevated in copper (Cu) and zinc (Zn; 300 to 500 milligrams per kilogram, mg/kg), and have poor water retention, while soils at the Tri-State mine site have elevated Zn contents (up to 2500 mg/kg).  Designer biochars were chosen with surface chemistry characteristics to raise soil pH and sequester heavy metals (e.g. Cu and Zn, etc.).  In preliminary experiments, gasified manure-based biochar (pH 10) and biochar produced from Miscanthus were found to raise soil pH and sequester Zn.  After these biochars were incorporated into the Formosa soil, rye grass and wheat were found to successfully grow compared to the control. Experiments using designer biochars in the Tri-State soil are under commencement. This presentation summarizes criteria for selecting an appropriate designer biochar to remediate diverse soil health issues at these two superfund sites.