Mobilization and chemistry of sediment-bound aluminum in a softwater reservoir
A survey of the sediments in a reservoir revealed elevated concentrations of aluminum in surface sediments one year after final alum application. Total and dissolved aluminum concentrations were also highest in the cove where treated water first enters the reservoir, deep water sample concentrations being greater than surface water samples. Deep water aluminum levels declined over time reflecting the decreased influence of the sediment on ambient aluminum concentrations. Microcosm experiments using intact sediment cores demonstrated the potential for aluminum mobilization after acidification and showed that behavior of the metal changed below pH 5.0. Laboratory conditions such as higher than ambient temperatures favored the formation of polymers which were removed by filtration prior to analysis. Historical copper sulphate treatment records and the appearance of copper in the sediment were used as a dating tool in a core taken from the reservoir. The stratigraphy of cations including aluminum in this core did not reflect changes that have been associated with acidification (e.g., depressed levels of Ca/Mg) or industrialization (e.g., increasing lead levels). An automated method of analysis using pyrocatechol violet to measure aqueous aluminum was designed. In its development, it was shown that the absorption curve, particularly at lower concentrations, is not linear as thought before. Since control of pH is critical in this procedure, other buffers were examined to better maintain solution pH. MES was substituted for HMTA with operational benefits. Development of an automated method of measuring aqueous organic aluminum was impeded by the unsatisfactory results achieved by the ion exchange column procedure. An alternative analytical scheme is suggested.
Samaritan, Jeanette Marie, "Mobilization and chemistry of sediment-bound aluminum in a softwater reservoir" (1993). ETD Collection for Fordham University. AAI9324626.