Biochar Application to Abandoned Mine Tailings: Managing Soils for Succession, Plant Growth, and Water Quality.

Acidic drainage and associated toxic heavy metals emanating from waste rock piles at historic metal mining sites cause enormous and long-lived environmental problems.  These barren piles, which degrade water quality and impair growth of vegetation, are unstable, subject to erosion and mass failure, and are difficult and costly to remediate.  We are using laboratory column experiments designed to assess whether adding biochar made from beetle-killed pine wood to mine tailings is an effective approach for reclaiming abandoned mine lands.  Using tailings from two mine sites near Silverton, CO we investigated the hypotheses that incorporating biochar into acidic mine tailings would 1) decrease heavy metals in leaching solution, 2) improve activity and diversity of microbial populations that might promote natural ecosystem succession processes, and 3) improve overall conditions for plant growth and soil formation by increasing nutrient and water holding capacity, increasing pH, and decreasing compaction, concretion, and bioavailable heavy metal concentrations.  We also investigated the longevity of any ameliorating effects resulting from amending acidic mine tailings with biochar.