Immobilization of Heavy Metals in Abandoned Mine Soils Amended with Al-Based Drinking Water Treatment Residuals: An Incubation Study.

Abandoned mines with acidic, heavy metal-contaminated soils are a widespread and serious problem in the United States. Amendment of these soils with a by-product of municipal drinking water treatment - drinking water treatment residuals (WTRs) - offers a low cost and “green” treatment alternative for abandoned mine sites. The pH of these soils is typically below 3, thereby mobilizing various heavy metals into the runoff. This acidic, metal-bearing surface and subsurface drainage can contaminate downstream and underground water supplies. Revegetation and reclamation of these mined lands is a challenging task as most plants cannot survive under these soil conditions. This study examines the metal binding capacity of an aluminum based WTR as a soil amendment to minimize heavy metal availability in acidic abandoned mine soils. However, in order to demonstrate its efficacy as a viable soil amendment, one must thoroughly understand the effects of varying soil solution properties on heavy metal retention. A batch incubation study was set up using an acidic soil from a Northeastern US mine site that was amended with various rates of Al-WTR, and the effects of soil solution properties on immobilization of certain heavy metals were examined. This study serves as the precursor to a comprehensive project aimed at achieving our long-term goal to develop a highly efficient, eco-friendly, and inexpensive model for stabilization and reclamation of abandoned acid mine sites.