BIOSOLIDS USE FOR RECLAIMING FLUVIAL MINE TAILINGS

This study was conducted to determine the effect of biosolids and lime on reclamation of a heavily contaminated metal site. Within the Superfund area near Leadville, CO, biosolids and lime were amended (1998) to a 1 ha site at rates of 240 Mg per ha each. In 2006, soil samples were collected on a 10 m x 10 m grid to a depth of 30 cm across the site. Basic soil analysis included pH, EC, total C and N, inorganic and organic C, and NO3-N and NH4-N. A sequential fractionation for metal contaminants of concern (Cd, Cr, Fe, Pb, Mn, and Zn) identified associations with: 1) soluble/exchangeable; 2) specifically sorbed/weakly bound; 3) non-crystalline Fe/Mn oxides; 4) crystalline Fe/Mn oxides and organically complexed; 5) residual organic; and 6) residual inorganic phases. Sequential extraction data was cross correlated with basic soil analysis. Basic soil analysis were affected by both lime and biosolids applications. Cadmium was found primarily in mobile phases, Cu, Fe, Pb, and Mn in more resistant phases, and Zn distributed equally among all soil fractions. Metals were negatively correlated with basic soil analysis. The greatest mobile-phase metal concentrations were observed at the site’s south end. This may have been due to a lack of uniformly applied or incorporated biosolids, or not enough lime applied to raise soil pH and complex metals in more immobile phases. If mobile phases were present over the entire site prior to reclamation, then a positive phase shift has occurred towards more immobile metal phases following reclamation