Characterization of coal ash released in the TVA Kingston spill to facilitate detection of ash in river systems using magnetic methods

Abstract

h i g h l i g h t sKingston coal ash increases magnetic susceptibility of riverbed sediment. Fluvial transport both enriches and dilutes the magnetic fraction of coal ash. Micron-size magnetite and maghemite occur within aluminosilicate spheres. Magnetospheres dominate the magnetic signal in the Watts Bar watershed. a b s t r a c tThe magnetic properties of riverbed samples collected after the 2008 Tennessee Valley Authority (TVA) coal ash spill in Kingston, Tennessee are investigated. Coal ash persists in this fluvial environment because 400,000 m 3 of ash remains in areas that were not dredged. The magnetic fraction is low in comparison to other coal ash; 1.4 wt% in a sample from the failed ash storage cell increasing to 3.0 wt% in riverbed samples in the Emory River near the spill. Thermomagnetic analysis, XRD, SEM and polarized light microscopy identified magnetospheres with magnetite and maghemite from the Kingston coal ash as the magnetic carrier. Anthropogenic nonspherical magnetic particles are introduced from the industrialized Tennessee River watershed prior to reaching the Watts Bar Reservoir. A bivariate plot of anhysteretic remanent magnetization (ARM) versus mass-normalized low field magnetic susceptibility (v LF ) models the mixing of ash in the rivers, identifying both enrichment of magnetospheres by sorting near the spill and dilution with native sediment downstream. Concentration-dependent magnetic parameters in ash-bearing samples are approximately 2-56 times stronger than those of the ash-free watershed samples. This study supports the use of magnetic parameters to track the ash as it is eroded and transported 71 km downstream to the Watts Bar Dam and suggests that v LF can be utilized to track the migration of coal ash in other river systems.

Magnetic susceptibility as a proxy for coal ash pollution within riverbed sediments in a watershed with complex geology (southeastern USA)

“…H CR /H C values for sediment with [ 13-14% ash range from 1.13 to 2.61 with an average of 1.81. These are similar to the hysteresis parameters observed for Kingston Fossil Plant coal ash (Cowan et al 2015). In contrast, diabase dikes have M R /M S values between 0.22 and 0.45 (McEnroe and Brown 2000), allowing a means to identify samples for which sediment derived from dikes could interfere with the use of v LF in coal ash detection.…”

“…In the Watts Bar Reservoir System impacted by the TVA spill we used the mass-normalized low field magnetic susceptibility (v LF ) of riverbed samples to measure the coal ash content. This rapid, efficient and inexpensive method predicted ash concentrations greater than 15% (Cowan et al 2013(Cowan et al , 2015.…”

“…The effectiveness of using magnetic susceptibility to quantify ash mixed with Dan River sediment is tested. Previously, we used magnetic susceptibility as an analytical tool to quantify ash from the Tennessee Valley Authority (TVA) spill at the Kingston Fossil Plant (Cowan et al 2013(Cowan et al , 2015. In 2008, coal ash slurry spilled directly from an ash storage cell into the Emory River and after these deposits were scoured, suspended and mixed with river sediment the concentration of ash could not be visually quantified.…”

“…Oxidation of pyrite (FeS 2 ) in pulverized coal at high temperature produces molten iron spheres and sulfur, and the iron oxidizes to form magnetite and hematite (Flanders 1994). Ash from the failed TVA storage cell had a relatively low weight percent magnetic fraction (MF) of 1.4%, which was composed of predominately magnetite and maghemite (Cowan et al 2013(Cowan et al , 2015. However, even a small amount of ferrimagnetic material was sufficient to impart a strong contrast in v LF compared with the paramagnetic or diamagnetic sediments derived from sedimentary rocks in the Emory and Clinch River watershed (Cowan et al 2013).…”

Assessment of heavy metal pollution in Vistula river (Poland) sediments by using magnetic methods

“…Magnetometry is also applied for tracing the transport of pollutants along the river by observing the migration of the strongly magnetic spherical-shaped particles (spherules) associated with heavy metals, which commonly originate from urban activities (power plants, smelting industries, disposal sites, municipal wastes) (Cowan et al 2015;Desenfant et al 2004;Li et al 2011;Zhang et al 2011). Changes in concentration-dependent magnetic parameters along core sediments can adequately reveal the distribution of river pollution over time.…”