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PM07 Pollutant Chemistry Transport, Cycling and Fate
(PM098) Development of a computer program that uses residence-time & biodegradation to predict BTEX removal in karst aquifers.
Fitzwater, R1, Painter, R1, Watson, V1, Byl, T1, 2, 1 Tennessee State University, Nashville, TN, USA2 USGS, Nashville, TN, USA
ABSTRACT- Approximately 40% of the United States east of the Mississippi River is underlain by karst aquifers. Karst ground-water systems are extremely vulnerable to contamination; however, the fate and transport of contaminants in karst areas are poorly understood because of the complex hydraulic characteristics of karst aquifers. Ground-water models developed using Darcy′s Law coupled to rates of biodegradation are useful for predicting the fate of fuels in unconsolidated aquifers, but have little utility in karst conduits. Conceptual models developed for karst aquifers have a consistent theme of non-ideal flow, storage and active flow components. This research used a residence-time distribution (RTD) model approach that integrated residence times of contaminants isolated in storage areas with the residence time of contaminants moving through conduits coupled to a pseudo-first order rate of biodegradation. The microcosms consisted of 4 1-liter chambers connected with small glass tubing. A peristaltic pump provided a consistent flow of karst water from a 10-gallon reservoir. First, a quantitative dye study was done to establish the residence time distribution of the three systems. This was followed by a sterile toluene run to measure sorption of toluene to the microcosm systems. The third microcosm run incorporated karst bacteria and toluene. The removal of toluene predicted by the RTD-biodegradation model and the experiment were within 2% agreement (n=3). The RTD-biodegradation model is currently being transformed into a user friendly program that utilizes MS Excel ® with Visual Basic interfaces. The prototype program will be demonstrated in the presentation.
Key words: transport, model, karst , fate
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