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. References: 25
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