HR: 0800h
AN: B11A-0064    [Abstracts]
TI: Abiotic Dissolved Organic Matter-Mineral Interaction in the Karstic Floridan Aquifer
AU: * Jin, J
EM: jinj@ufl.edu
AF: University of Florida, Department of Geological Sciences 241 Williamson Hall P.O. Box 112120, Gainesville, FL 32611, United States
AU: Zimmerman, A
EM: azimmer@ufl.edu
AF: University of Florida, Department of Geological Sciences 241 Williamson Hall P.O. Box 112120, Gainesville, FL 32611, United States
AB: Dissolved organic matter (DOM)-mineral interaction (e.g. adsorption, desorption, mineral dissolution) in groundwater is a significant factor controlling geochemical, environmental and microbial processes and may be helpful in efforts to track groundwater sources or contaminant fate. Despite its importance, the dynamics and consequences of these abiotic interactions remain poorly understood, largely due to the inaccessibility and heterogeneity of the subsurface, as well as the chemical complexity of DOM. This study models the OM-mineral interactions that takes place in the Floridan aquifer through laboratory adsorption-desorption experiments using DOM (groundwater, river water, soil extracts) and carbonate minerals (calcite, dolomite) collected in north Florida. High performance liquid chromatography-size exclusion chromatography (HPLC-SEC) and UV-fluorescence excitation-emission matrix (EEM) spectrophotometry was used to examine the organic compound types exhibiting preferential affinity for carbonate minerals. Our results show that the DOM-carbonate adsorption/desorption isotherms are well described by the Freundlich model. Freundlich exponents (average value: 0.6488) less than one indicated a filling of adsorption sites. Minerals from Ocala tend to have higher adsorption affinity as well as adsorption capacity than those from Suwannee River Basin; however, both were found to have mineral dissolution. Two fluorescent signals, indicative of a fulvic-like (at excitation wavelength 295-310 nm, emission 400-420 nm) and a protein-like (275/345nm) moiety, were detected in DOM. A reduction in the fulvic-like peak intensity occurred following carbonate adsorption while the protein-like peaks remain almost unchanged indicating the preferential adsorption of fulvic acids. HPLC-SEC results (DOM properties as a function of molecular weight) will be discussed. The chemical properties of DOM in environmental groundwater samples will also be presented and evaluated in light of the above experimental results.
DE: 1022 Composition of the hydrosphere
DE: 1055 Organic and biogenic geochemistry
DE: 1831 Groundwater quality
DE: 1847 Modeling
SC: Biogeosciences [B]
MN: 2007 Fall Meeting