SREL Reprint #2273

The potential role of sediment mineralogy in regulating aluminum concentrations in lakewater

 Louis M. McDonald Jr1, V. P. Evangelou1, and Paul M. Bertsch2

1Dept. of Agronomy, University of Kentucky, Lexington, KY 40546-0091
2Univ. of Georgia, Savannah River Ecology Laboratory, Aiken, SC 29802

Abstract: An understanding of the controls on aluminum solubility is essential because Al can reach toxic levels in waters that are affected by acidic precipitation or acid mine drainage. One factor which has received little attention is the role of in-lake sinks for Al. We hypothesized that a chloritization mechanism was capable of removing large amounts of Al from solution when sediments contained 2:1 minerals without well-developed Al-hydroxy interlayers. The objective of this investigation was to evaluate the potential role of lake sediments in regulating Al equilibria in the overlying waters. Water chemistry data, sediment mineralogy and exchange phase composition, and Al sorption isotherms were used. Sediments with well developed Al-hydroxy interlayers sorbed less total Al, accumulated more Al on the readily reversible exchange phase, and had less pH buffering capacity than sediments without Al-hydroxy interlayers. We conclude that the mineralogy of lake sediments needs to be considered when evaluating Al equilibria in lakes.

Keywords: 2:1 clay minerals, Al-hydroxy, aluminum, equilibria, hydroxylation, interlayers

SREL Reprint #2273

McDonald, L.M., V.P. Evangelou, and P.M. Bertsch. 1998. The potential role of sediment mineralogy in regulating aluminum concentrations in lakewater. Water, Air and Soil Pollution 104:41-55.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).