First Name:
Daniel
Last Name:
Gaspari
Major Department:
Geology
Thesis Director:
Ellen A. Cowan
Date of Thesis:
Aug 2014
In December 2008, an unprecedented spill of coal ash occurred at the Kingston Fossil Plant near Harriman, Tennessee. Despite dredging efforts by the Tennessee Valley Authority, approximately 229,000 m3 of ash remains in the rivers of the Watts Bar Reservoir system and is available for transport during high discharge events. Grab samples of bottom sediment were collected in 2010-11 adjacent to, upstream and as far as 24 miles downstream of the spill. The morphology of coal ash is heterogeneous, but several of its magnetic properties are remarkably consistent between samples. Point counting of magnetic separates and thermomagnetic analysis indicate that anthropogenically formed magnetite is associated primarily with black ash spherules. The magnetic grain size found in all samples is uniformly pseudo-single domain (PSD). Low field magnetic susceptibility (χLF) varies depending primarily on the magnetite content and to a lesser extent the other iron oxides, including hematite, contributed by background sediment. A bivariate plot of anhysteretic remanent magnetization (ARM) versus χLF identifies two distinct populations of samples upstream and downstream of the spill. Overlap of these populations occurs at χLF < 1.0 x 10-6 m3/kg and ARM < 2.8 x 10-6 kg/m3 supporting morphological evidence that there is anthropogenic magnetic material (AMM) in the Tennessee River that did not originate from the Kingston spill. A mixing line (R2=0.85) composed of 28 samples, models the sorting of Kingston coal ash and background river sediment. The position of each sample on this line is proportional to its concentration of magnetic material and the slope of the line is indicative of magnetic grain size.
Acid digestion of the samples yielded total trace element concentrations. The concentrations of As, Ba, Cd, Se, and V are positively correlated with ARM, indicating that these elements are contained within the magnetic fraction of samples affected by the Kingston spill and are possibly incorporated into anthropogenic magnetite. However, Co, Pb, Mn, and Zn are independent of magnetic properties. Analysis of the magnetic properties of coal ash contaminated sediments can effectively be used to monitor changes in ash content and trace element concentrations resulting from downstream transport within the Watts Bar Reservoir system.