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Remediation of Abandoned Mine Lands |
Thursday, October 2, 2008 : 1:20 p.m.
Leaching Experiments with Acid Mine Drainage Sediments from Abandoned Coal Mines of Southeastern Ohio
Acid mine drainage (AMD) is a serious environmental problem in SE Ohio. Iron is the major heavy metal with variable concentrations of aluminum and manganese. Some watersheds have abundant rock alkalinity and calcium can be an important cation in the water and sediments. The fine sediments precipitated from these waters do not allow a full recovery of remediated AMD impacted streams. The need to separate these sediments from the stream and use them in some industrial application is evident. Sediments were collected at four different acid mine drainage sites in SE Ohio. These sites have contrasting chemical composition in terms of the ions Ca, Fe, Mn, and Al. In this work, we present the results of leaching experiments with sediments deposited in the four types of waters: 1) waters with relatively low Al, Mn, and Ca and high Fe, 2) waters with high Al that show higher water-rock interaction, 3) waters with relatively high Mn, and 4) waters with high Ca and neutral to alkaline pH that reflect the presence of carbonate rocks. 12 g of sediments were mix with 400 ml of waters of pH 5, 6, 7, and 8, during six days. Filtered water samples were collected every day. The results show that the pH of the solution changed with time as well as the release of ions to the solution but at the sixth day the waters were close to equilibrium with the sediments. Of the different AMD sediments, the sediments that contained more iron (70% iron hydroxide) released the lower concentrations of heavy metals to the solution. These results suggest that the use of AMD sediments should consider the chemical composition of the sediment, the pH of the water used in the application, and the time that the sediment will be in contact with the water.
Dina L. Lopez, Ohio University Dina L. Lopez is a professor of Geochemistry and Hydrogeology in the Department of Geological Sciences, Ohio University. She graduated with a BS in Chemistry and Physics from the University of El Salvador, a M.Sc. in Physics from Virginia Tech, and Ph.D. from Louisiana State University. She worked as a post doc inn hydrogeology at the University of British Columbia. She has been in Ohio University since 1995. Her areas of research are acid mine drainage, diffuse soil degassing and heat flow in hydrothermal areas.