Geology topics

Thomas Duane Byl

Publications and source records attributed to Thomas Duane Byl.

3 recordsLinked to original sources

USGS2000

Biodegradation of chlorinated ethenes at a karst site in middle Tennessee

This report presents results of field and laboratory investigations examining the biodegradation of chlorinated ethenes in a karst aquifer contaminated with trichloroethylene (TCE). The study site, located in Middle Tennessee, was selected because of the presence of TCE degradation byproducts in the karst aquifer and available site hydrologic and chlorinated-ethene information. Additional chemical, biological, and hydrologic data were gathered to evaluate whether the occurrence of TCE degradation byproducts in the karst aquifer was the result of biodegradation within the aquifer or simply transport into the aquifer. Geochemical analysis established that sulfate-reducing conditions, essential for reductive dechlorination of chlorinated solvents, existed in parts of the contaminated karst aquifer. Other areas of the aquifer fluctuated between anaerobic and aerobic conditions and contained compounds associated with cometabolism, such as ethane, methane, ammonia, and dissolved oxygen. A large, diverse bacteria population inhabits the contaminated aquifer. Bacteria known to biodegrade TCE and other chlorinated solvents, such as sulfate-reducers, methanotrophs, and ammonia-oxidizers, were identified from karst-aquifer water using the RNA-hybridization technique. Results from microcosms using raw karst-aquifer water found that aerobic cometabolism and anaerobic reductive-dechlorination degradation processes were possible when appropriate conditions were established in the microcosms. These chemical and biological results provide circumstantial evidence that several biodegradation processes are active in the aquifer. Additional site hydrologic information was developed to determine if appropriate conditions persist long enough in the karst aquifer for these biodegradation processes to be significant. Continuous monitoring devices placed in four wells during the spring of 1998 indicated that pH, specific conductance, dissolved oxygen, and oxidation-reduction potentials changed very little in areas isolated from active ground-water flow paths. These stable areas in the karst aquifer had geochemical conditions and bacteria conducive to reductive dechlorination of chlorinated ethenes. Other areas of the karst aquifer were associated with active ground-water flow paths and fluctuated between anaerobic and aerobic conditions in response to rain events. Associated with this dynamic environment were bacteria and geochemical conditions conducive to cometabolism. In summary, multiple lines of evidence developed from chemical, biological, and hydrologic data demonstrate that a variety of biodegradation processes are active in this karst aquifer.

Tennessee↗

USGS1995

Characterizing water quality in the North Fork-Fall Creek Hydrologic Unit Area, Tennessee

The North Fork-Fall Creek Watershed in Bedford County, Tennessee is a karst terrain with a complex interconnection between ground water and the surface water-drainage network. Multiple sources of agricultural and domestic contamination make the effective design of best management practices difficult. Ongoing investigations by the U.S. Geological Survey and several county, State, and Federal agricultural agencies are attempting to refine source identification and improve the effectiveness of best management practices in the basin.

Tennessee↗

USGS1994

Biomonitoring our streams

Testing for chemical pollution in our nation's streams has traditionally meant using analytical chemistry. In recent years, environmental agencies have endorsed biological monitoring to enhance or replace chemical monitoring. The theory behind biological monitoring (biomonitoring) is to use the organisms living in the aquatic system as a measure of water quality. This concept was applied to air quality and used by miners who took canaries into deep mines with them. If the canary died, the miners knew the air was bad, and they had to leave the mine. Biomonitoring an aquatic system uses the same theoretical approach . Aquatic organisms are subject to pollutants in the stream as it flows by, day or night. Consequently, the health of the organisms reflects the quality of the water they live in. If the pollution levels reach a critical concentration, certain organisms will die, migrate away, or fail to reproduce, eventually leading to the disappearance of those species at the polluted site. Normally, these organisms will return if conditions improve in the system. The three general components of an aquatic ecosystem that influence the biological community are: water chemistry, geomorphology, and hydrology. Each component influences the health of the biological community individually and together . Toxic chemicals are only a single factor within the water-chemistry component. The relation of these three components to each other can be shown on a triangle (figure 1). The relative importance of one component may change with time and location . At certain times of the year or in different geographical settings, a single factor may exert primary control on the well-being of the biological community. For example, straightening a stream and removing all woody debris drastically alters a stream's geomorphology. This results in loss of natural habitat and shelter for certain organisms. The organisms that require this shelter will disappear from the modified system. Separating the influence of one component from the others is difficult. Consideration of all three components and their interactions is critical when interpreting biomonitormg data.

Open-File Report↗