Long-Term Effects of Biosolid and Fly Ash Utilization On the Reclamation of Acid Mine Spoil.

Surface mining in the Appalachian region of the United States is known to generate acidity through the oxidation of pyritic minerals in the overburden when exposed to water and oxygen. The extremely acidic conditions combined with poor plant nutrition status, and elevated concentrations of hydrolyzable metals (such as Al and Mn) and trace elements (Cu and Zn) make it difficult to revegetate and reclaim these areas. Runoff from overburden, known as acid mine drainage, poses a threat to both ground and surface water quality. Research has shown that the application of organic matter, particularly biosolids, on acidic mine spoil aids in revegetation efforts by acting as a source of alkalinity and providing essential nutrients, such as nitrogen and phosphorus. Research on the use of acidic or neutral fly ash as a reclamation amendment has shown that while it is not useful in neutralizing the acidity, it acts as a source of macro and micronutrients as well as improves the physical properties of the spoil. Co-applications of biosolids and neutral fly ash have been documented, but the long term effects have not been studied. A study was begun in 1994 to document the potential long term effects of a municipal sewage sludge plus fly ash amendment on an abandoned acidic surface mine site. The site is a contour cut mountain top site in the Western Appalachian Plateau/Cumberland Mountains physiographic region in northeastern Tennessee. The 1.6 hectare site received a one-time amendment of a mix of Class A (lime-stabilized) biosolid from Knoxville Utility Board’s Kuwahee Waste Water Treatment Plant at a rate of 197 Mg ha^-1 and neutral fly ash from the Kingston Fossil Plant in Kingston, TN at a maximum rate of 394 Mg ha ^-1. The potential long term effects were studied through simulated weathering and monitoring the leachate chemistry. Results showed an increase in leachate pH, decrease in metals and trace elements, and a potential concern in an increase of boron concentration. The objectives of the current study are to determine the actual long term effects of the amendments at the field site, and to evaluate the effects on carbon and nitrogen cycling 18 years after the sludge-fly ash application. To accomplish this, various chemical characteristics (including pH, CEC, total C, total N) and mineralogy will be analyzed and a vegetation survey completed. It is expected that the treatment will have resulted in greater carbon and nitrogen storage, enhanced nutrient holding capacity, long term neutralization of acidity, and decrease in concentration of bioavailable trace elements.