Hazardous Metallic Elements in Tennessee Copper Basin Stream Sediments: Sources, Concentrations, and Distributions

Sampling and Analyses Procedure

Sampling was conducted for analyses in various streams and rivers feeding into the Copper Basin watershed being sure to gather samples from within the watershed and outside the watershed as background samples from which to compare results. Sites were chosen using four 7.5’ quadrangles covering the Copper Basin Area; Ducktown Quadrangle, Isabella Quadrangle, Mineral Bluff Quadrangle, and the Epworth Quadrangle. Each sample was collected using a plastic spoon with the sediment collected deposited into a Ziploc plastic bag which was then deposited into a second plastic bag. Samples were collected from both stream channels and banks. Disposable plastic spoons were used in order to both prevent major element contamination through use of a metal instrument and to prevent cross-contamination between samples. Once collected, each sample was labeled and a GPS coordinate was then obtained for each sample site. Each sample was then processed into pressed pellets and analyzed with the Oxford MDX 1800 X-ray Fluorescence spectrometer.

History of the Copper BasinCopper was first discovered in 1843, and just four years later the copper began to be mined. In the early 1850s, the mining industry began to boom and wagon trails were created and more companies moved into the area to begin mining. The first smelter, which is used to remove the copper ore from the rocks, was built in 1854 on Potato Creek. In the 1860s, due to the American Civil War, the mining industry slowed a bit but did not cease. The creation of the Marietta and North Georgia Railway in 1890, which connected Knoxville, TN and Atlanta, GA, greatly increased copper production. Copper mining continued throughout the 1900s up until July of 1987 when the mines were official closed.

AbstractThe Tennessee Copper Basin, southeast Tennessee, is an area affected by over 100 years of mine-impact degradation to regional landscape, flora, and fauna. Early mining and ore processing techniques resulted in stripping of the landscape for wood fuel and the production of atmospheric sulfuric acid. The resulting acidic rains and oxidation of bedrock sulfide minerals sterilized the soil, resulting in long-term erosion of metallic elements such as arsenic (As), lead (Pb), and uranium (U) into the local watershed. Although mining operations ceased in 1987, the Copper Basin still exhibits signs of environmental stress. This focus of this research is geochemical study of Copper Basin stream sediments to determine which environmentally hazardous metallic elements are present at concentrations higher than natural background, and the sources of those sediments. The research has direct implication to long-term environmental and health studies of the Copper Basin. According to the U.S. EPA, human consumption of As may cause illnesses, ranging from cardiovascular ailments to skin disease, or even death. Consumption at lower concentrations may cause illnesses ranging from cardiovascular ailment to skin disease. The consumption of Pb on both children and adults are well known, and include mild headaches, reproductive disorders, and long-term damage to the brain and nervous system. U is a radioactive element, which even at very low concentrations may present cancer risks. Our research identifies the primary sources of Copper Basin metals-bearing sediments as old mine tailings deposits and bedrock exposures. X-ray fluorescence spectrometry (XRF) analyses of sediment samples collected downstream of tailings ponds and bedrock outcrops show the presence of As ≤ 44 ppm, Pb ≤ 244 ppm, and U ≤ 32 ppm. Additional metals present are copper, zinc, and nickel. The geographic distribution of these metallic elements also is being assessed as a measure of whether their concentrations change during downstream sediment transportation.

Environmental damage in the Copper Basin The copper mining and smelting industries in the Copper Basin were the most influential human activity that was detrimental to the environment. Logging of the surrounding area to provide fuel for the open-air roasting of the ore were the first to cause damage to the environment. The roasters released toxic sulfur dioxide into the atmosphere which fell as acid rain when it precipitated (Quinn 1988). The result of the lumbering and open-air roasting caused the death of the vegetation in the area, and with an annual rain fall of 58 inches, the lack of vegetation caused the terrain to become even more susceptible to erosion. By 1907 the sulfur dioxide fumes had damage an estimated 200,000 to 640,000 acres in the area, and in the center of the basin was a 7,600 acres of severely eroded landscape which was completely devoid of plant life (Quinn 1988). Not only was the vegetation in the area affected by the mining but the water quality of the area was also affected. Since the beginning of mining operations, the Ocoee River has been contaminated by the mining waste present in both the water and stream bed sediments (Muncy). Even though the companies of the Copper Basin were killing the environment, they were also trying to sustain it as best they could.

Photos courtesy of the EPA

Photos courtesy of the EPA

Photos courtesy of the EPA

Mayfield, Aaron; Anderson, Brad; Hornaday, Jake; Marston, Bart; Cribb, J. Warner, Department of Geosciences, Middle Tennessee State University, Murfreesboro, Tennessee

Acknowledgments

Funding for this research is provided by StepMT and FRCAC grants to Aaron Mayfield and Warner Cribb. We gratefully appreciate the support of the MTSU Undergraduate Research Center and the MTSU Office of Research. Funding for the MTSU x-ray fluorescence lab is provided by the National Science Foundation. We also thank Ken Rush, Director of the Ducktown Basin Museum, for his support.

Overview

Although numerous studies have been conducted studying the toxic metal concentrations in the Copper Basin Watershed, none have focused on the toxic metal load present in the stream bed sediments. The purpose of this study is to determine whether or not toxic elements are mobile within the stream sediments and how quickly the toxic metals attenuate with respect to distance from potential contaminant sources. This study focuses on five toxic metals: arsenic, cadmium, lead, thorium, and uranium. Through erection of graphical models, attenuation rates for these particular toxic elements are determined, as well as any potential contaminant sources possibly enriching the sediment load.

Potential Tennessee Copper Basin toxic metal contaminant sources

Sample sites in the Tennessee Copper Basin.

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Trace element Attenuation rateArsenic (As) - 0.3 ppm/km

Cadmium (Cd) - 0.9 ppm/kmLead (Pb) + 1.6 ppm/km

Thorium (Th) + 0.1 ppm/kmUranium (U) + 0.03 ppm/km

Results & Conclusions

1. The presence of toxic metals in Tennessee Copper Basin stream sediments is due to erosion from a) tailings ponds, b) abandoned mines, c) bedrock outcrops

2. Lead, Thorium, and Uranium concentrations increase in the downstream sediment supply.

3. Arsenic and Cadmium concentrations decrease in the downstream sediment supply.

4. For Cd and As, concentration ranges decreases with downstream sediment transport.

5. For Pb, TH, and U, concentration ranges do not change appreciably with downstream sediment transport.

Future Work

Future studies will sample stream water and pH over the sediment sample sites. Water analyses be carried out using the inductively coupled plasma mass spectrometer to determine which toxic metals may be dissolved into surface water.