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dc.contributor.advisorSharp, John Malcolm, Jr., 1944-
dc.creatorCagle, Margaret Frances, 1983-
dc.date.accessioned2017-01-06T19:31:08Z
dc.date.available2017-01-06T19:31:08Z
dc.date.issued2007-12
dc.identifierdoi:10.15781/T21G0HX9V
dc.identifier.urihttp://hdl.handle.net/2152/44100
dc.description.abstractSulfate (SO₄ ²⁻) concentrations in the groundwater at the Luminant Monticello lignite mine, northeast Texas, vary with both time and space. SO₄ ²⁻ is monitored closely because it is a product of chemical reactions that can lead to acid mine drainage. Although acid mine drainage is not a problem at Monticello, SO₄ ²⁻ concentrations in some areas are high and correspond to high total dissolved solids (TDS), low pH groundwater. At Monticello, chloride, total dissolved iron, and total dissolved manganese concentrations also are variable. To examine this variability, 46 monitoring wells are divided into those: 1) screened in rock underneath the lignite seam (underburden); 2) screened in the rock over the lignite seam (overburden); and 3) screened in the reclaimed spoil. There is a wide range of SO₄ ²⁻ concentration across the mine with statistically significant differences between the SO₄ ²⁻ distributions for each well category. Three hypotheses may explain the spatial SO₄ ²⁻ variability: (1) The heterogeneity of the mined material (2) Flushing of SO₄ ²⁻ from the reclaimed section into the overburden (3) Exposing iron sulfides to oxidizing conditions when the water table is dropped by mine dewatering operations. Possible sources of SO₄ ²⁻ include the oxidation of pyrite and/or the dissolution of gypsum. Temporal SO₄ ²⁻ variability is evident in the SO₄ ²⁻ time series for each well. In the underburden, SO₄ ²⁻ seems to be approaching a steady state; however, some wells in the unmined overburden and reclaimed area have SO₄ ²⁻ trends that are increasing or are highly variable with time. Water table fluctuations or flushing caused by seasonal meteorological changes may control these trends. Correlation analyses show that for most underburden, overburden, and reclaim wells, SO₄ ²⁻ does not correlate with pH, indicating that acidity does not accompany the incorporation of SO₄ ²⁻ and that SO₄ ²⁻ may be advected from another part of the mine. Analysis of water level and SO₄ ²⁻ time series, as well as Cl⁻ and SO₄ ²⁻ time series, show that advection from reclaimed areas cannot account for every high SO₄ ²⁻ value or increasing SO₄ ²⁻ concentration in the overburden and reclaim. Groundwater in most overburden and reclaimed areas are at equilibrium with gypsum, indicating gypsum precipitation if SO₄ ²⁻ is flushed into the area and gypsum dissolution if SO₄ ²⁻ is flushed out. Time series analyses shows some of the wells with increasing SO₄ ²⁻ concentration to be approaching equilibrium. Also, most SO₄ ²⁻ time series have a seasonal component. Flushing from the reclaimed areas is considered to be the dominant process controlling SO₄ ²⁻ variability in the overburden. A combination of flushing and aqueous geochemical processes related to heterogeneity controls the SO₄ ²⁻ concentration in the reclaimed land.en_US
dc.format.mediumelectronicen_US
dc.language.isoengen_US
dc.relation.ispartofUT Electronic Theses and Dissertationsen_US
dc.rightsCopyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en_US
dc.subject.lcshGroundwater--Texas
dc.subject.lcshSulfates
dc.subject.lcshLignite--Texas
dc.subject.lcshStrip mining--Texas
dc.titleTemporal and spatial sulfate variability in groundwater at a lignite mine, northeast Texasen_US
dc.typeThesisen_US
dc.description.departmentGeological Sciencesen_US
dc.type.genreThesisen_US
thesis.degree.departmentGeological Sciencesen_US
thesis.degree.disciplineGeological Sciencesen_US
thesis.degree.grantorUniversity of Texas at Austinen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Scienceen_US
dc.rights.restrictionRestricteden_US


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