Pre- and post-remediation characterization of acid-generating fluvial tailings material

The upper Arkansas River south of Leadville, Colorado, USA, contains deposits of fluvial tailings from historical mining operations in the Leadville area. These deposits are potential non-point sources of acid and metal contamination to surfaceand groundwater systems. We are investigating a site that recently underwent in situ remediation treatment with lime, fertilizer, and compost. Preand post-remediation fluvial tailings material was collected from a variety of depths to examine changes in mineralogy, acid generation, and extractable nutrients. Results indicate sufficient nutrient availability in the postremediation near-surface material, but pyrite and acid generation persist below the depth of lime and fertilizer addition. Mineralogical characterization performed using semi-quantitative X-ray diffraction and quantitative SEM-based micro-mineralogy (Mineral Liberation Analysis, MLA) reveal formation of gypsum, jarosite, and complex coatings surrounding mineral grains in post-remediation samples.