Chemical Characteristics of Sediments Used for Coversoiling a Mine Tailings Pond and Effects On Plant Growth.

Chemical Characteristics of Sediments used for Coversoiling a Mine Tailings Pond and Effects on Plant Growth Katie L. Rothlisberger, Hamid Shahandeh, Frank M. Hons, and Terry J. Moore Texas Agrilife Research, Texas A&M University, and BP Remediation Management For approximately 100 years this research site served as a repository for mine tailings containing copper (Cu), manganese (Mn), zinc (Zn) and other metals. Since the tailings processing ceased a few decades ago, the repository has been dewatered and is undergoing reclamation to mitigate the potential effects of airborne dust, erosion, and leaching to ground water. Reclamation called for a small portion of the tailings repository to be covered with a 24” layer of dredged lake sediments, which also contained elevated concentrations of Cu, Zn, and Mn. Revegetation of these dredged lake sediments has been largely unsuccessful after 2 - 3 years effort. The primary objective of this study was to determine the effects of alternate wetting/drying cycles, addition of organic matter, zero-valent iron (Fe0) and lime kiln dust (LKD), and sediment washing on metals solubility, other chemical properties of the dredged sediments, and to determine the response of plants grown in a greenhouse setting. Sediment treatments included: 1-3) Control (oxidized and unoxidized), 1%, 3% wheat straw by weight, 4) Fe0 (2500 ppm by weight), 5) LKD (1x), 6) LKD (1x) + 1% wheat straw + 2500 ppm Fe0, 7) washed sediment (1 pore volume), 8) washed sediment (2 pore volumes), and 9) washed sediment (3 pore volumes). Samples were collected at 0, 7, 14, 21, and 28 d and extracted with water to analyze for pH, EC, ICP metals, and nitrate. Following this portion of the study, remaining material from all replicates of each treatment were combined and thoroughly mixed. Subsamples were collected and placed in nine separate pots where three grass species (barley, red top, and annual ryegrass) were subsequently seeded and grown in a greenhouse environment. Germination counts and plant heights were determined once per week for four weeks after seeding, as well as rooting depth and root and shoot weights at harvest. Discussion will focus primarily on treatments that significantly influenced sediment properties and plant growth.