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

An understanding of the controls of aluminium 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. The authors hypothesized that a chlorination 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 water. Samples were collected from Fishtrap Lake, and Davey Lake, and Care Run Lake sediments, in the Eastern Coalfields region of Kentucky, USA and from Rough River Lake in the Western coalfields region of Western Kentucky. 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 has less pH buffering capacity than sediments without Al-hydroxy interlayers. It was concluded that the mineralogy of lake sediments needs to be considered when evaluating Al equilibria in lakes