PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM099) Desorption of Toluene from Karstic Materials and Implications for Transport in Karst Aquifers.
Beddingfield, M1, Hines, T1, Painter, R1, Byl, T1, 2, 1 Tennessee State University, Nashville, TN, USA2 USGS, Nashville, TN, USA
ABSTRACT- Karst aquifers dominated by conduit flow are extremely vulnerable to fuel contamination such as leaky underground storage tanks or spills. There are direct flow paths through fractures and sinkholes that often allow pure product to move rapidly into the conduit system. Not much is known how the fuel will interact with the carbonate rock in the conduit system. The objective of this research was to bridge this information gap by measuring sorption and desorption of fuels to karst materials. The first phase of this study looked at the dissolution and desorption processes. Initial experiments (n=5) used karst bedrock fragments of known size soaked in toluene for 24 hours. Then the sterile-toluene rocks were placed in sterile distilled water. The concentration of toluene dissolved in the water was measured over increasing time periods. These data were used to derive a first-order exponential rate of dissolution/desorption [Cw(t)=Ciekt]. The empirical value for k was 0.8958. The toluene concentration in the water reached a maximum carrying capacity in approximately 3 weeks. These results have implications for designing a model that predicts the fate and transport of fuels in karst aquifers. The second phase of this work will focus on sorption and desorption in the presence of indigenous karst-aquifer bacteria.
Key words: sorpt, toluene, karst, dissolution