Date of Award

Summer 1990

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

Gary C. Schafran

Committee Member

Joseph H. Rule

Committee Member

Dennis A. Darby

Call Number for Print

Special Collections LD4331.G4I43

Abstract

Simulation of acidic groundwater passing through lake sediments was conducted under controlled conditions in a laboratory. Three sediment cores collected intact from the near-shore region of an acidic lake were subjected to simulated groundwater inputs of initially identical chemistry for a seven day period. Following this period water being used in the simulation for two of the sediment cores was acidified by hydrochloric acid (HC1) addition to examine the ability of these sediments to neutralize acidic groundwater with varying H+ concentration.

Simulated acidic water passing through the sediment cores mobilized significant amounts of metals. The sediment acted as a sink or a source of metals dependent on H concentration of water leaving the sediments. Following influent acidification, the sediments acted as a source of aluminum (Al) until the end of the experimental period. In all cores, influent H+ was neutralized predominately by the mobilization of Al. Fluoride release from the sediments was episodic following acidification. The majority of the fluoride released was complexed with Al forming A1F2+ which was the predominant (>99%) Al-F species. Unlike Al, both manganese (Mn) and lead (Pb) mobilization was episodic with the influent acidification. For one core in the period before acidification, the sediment acted as a sink for Pb, however, this Pb was remobilized following influent acidification. The sediment was a "strong" sink for iron (Fe) prior to and following the influent acidification period. Acidification showed no effect on the mobilization of Fe, and over 99% of the influent Fe was lost to the sediments. Comparison of sediment metal fractions showed substantial variation in total metal content among the cores, however, the percentage distribution of the sediment metal fractions among the cores was similar. The inter-core variation in sediment chemistry and it's effects on groundwater chemistry as observed during the initial seven day period, suggest that the chemistry of groundwater inputs to lakes should exhibit high spatial variability.

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DOI

10.25777/4gjk-6c26

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