Date of Award

Summer 2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Ocean and Earth Sciences

Committee Director

Peter N. Sedwtck

Committee Director

Gregory A. Cutter

Committee Member

H. Anna Jeng

Call Number for Print

Special Collections LD4331.O35 W35 2013

Abstract

Each year a significant amount of coal fly ash enters the environment, where it can potentially cause adverse effects by releasing a range of bioactive trace elements. In this context, environmental studies have largely focused on the leaching of trace elements from the coal ash in landfills by rainwater and groundwater, while there has been relatively little study of the release of bioactive trace elements from coal fly ash deposited in natural fresh waters such as rivers and lakes. Furthermore, the batch leaching methods that have been used to study the interaction of rainwater and groundwater with coal ash in landfills are not readily extrapolated to rivers and lakes, where the solution to particle ratio is typically high. A flow-through leaching protocol, used previously to estimate the fractional dissolution of trace elements from mineral aerosols in ocean waters, was adapted for this study to address this problem. This rapid leaching technique more closely resembles the interaction of coal ash with fresh waters, thus allowing an assessment of the release of coal fly ash constituents into rivers and lakes. A series of flow-through leaching experiments were performed using coal fly ash and freshwater samples collected from three rivers and one lake in the southeastern United States. A suite of bioactive trace elements (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Pb, and U) was analyzed in the resulting leachate solutions, and in acid digests of the bulk coal ash, using high-resolution plasma-source mass spectrometry. The data suggest that significant fractions of a number of bioactive trace elements in coal ash are readily soluble in natural fresh waters typical of the Southeastern United States. High ratios of vanadium, manganese, and iron concentrations to cadmium, and uranium concentrations may identify a freshwater source as being contaminated by coal fly ash. The results of this study suggest a strong correlation between leaching solutions with high dissolved organic carbon concentrations and leachate solutions with high concentrations of trace elements released into solution. This observation is supported by the regression analysis performed on the leachate solution concentration data, where the dissolved organic carbon concentration of the leaching solution had the statistically strongest relationship to trace element fractional solubility in the coal fly ash. The elements most readily released into leaching solutions with high dissolved organic concentrations included vanadium, chromium, cobalt, copper, cadmium, and lead.

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DOI

10.25777/q602-0n32

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