Research in our group is focused on "aquatic organic geochemistry". This includes studies of the biogeochemical reactivity of naturally-occurring organic compounds ("humic substances") in aquatic systems, as well as the development of more efficient separation and spectral identification methods for the complex mixtures commonly found in natural environments. Natural water bodies are dynamic, and the ecological impacts and ultimate fate of anthropogenic chemical contaminants introduced into them are largely dependent on their reactions with the "natural" constituents of the watershed. Unfortunately, the underlying chemical principles governing these reactions are largely unknown at his time, primarily because of a lack of sufficiently powerful analytical techniques. Our goal is a detailed understanding of the environmental geochemistry of surface and ground waters, with a major emphasis on development and application of new analytical techniques.

We are working with scientists at the National High Magnetic Field Laboratory (NHMFL) on the development of advanced mass spectrometry techniques for characterizing humic substances in a variety of surface waters. Using the ultrahigh resolution capabilities of high field (9.4T) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS), we have determined the molecular formulas of several thousand individual humic molecules with mass accuracies previously unobtainable. We are now focusing on determining molecular structures of humic substances containing nitrogen and phosphorus in order to better understand N & P cycling in estuaries and wetlands. Parallel work is also underway on development of high resolution Inductively Coupled Plasma Mass Spectrometry (ICP-MS) methods for quantitating very low levels of metals and nutrients associated with humics.

Because humic substances are inherently very complex mixtures, the development of increasingly powerful separation methods is an ongoing part of our work. For example, Capillary Electrophoresis (CE) appears to be a promising new separation technique for organic geochemists. We have focused on the effects of solution modifiers in CE, including free-flowing polymers additives (CEPA), and we are using Inverse CE (ICE) to measure binding constants of environmentally-significant metals (e.g. Cu, Hg) to humics. We are also studying enhancements to traditional liquid and supercritical fluid chromatography which are applicable to problems in organic geochemistry. This work includes the use of mobile phase additives in HPLC and unconventional "normal phase" modifiers in SFC.

Humic substances also play an important role in the distribution of chemicals in soils. For example, the binding of pesticides to soil particles depends on both the quantity and chemical character of soil organic matter. We have recently begun a study of new extraction techniques, including the use of organic modifiers and supercritical fluids, that will better predict the extent to which soil-bound pesticides will leach into ground water.

Stenson, A.C., Marshall, A.G., Cooper, W.T. 2003. "Molecular Fingerprinting of Aquatic Fulvic Acids by Ultrahigh Resolution ESI FT-ICR Mass Spectrometry", in Humic Substances: Nature’s Most Versatile Materials, Proceedings of the 20^th Annual Meeting of the International Humic Substances Society, Taylor & Francis, Boston, MA.

Stenson, A.C., Marshall, A.G., Cooper, W.T. 2003. "Exact Masses and Chemical Formulas of Individual Suwannee River Fulvic Acids from Ultrahigh Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectra", Analytical Chemistry, 75, 1275-1284.

Llewelyn, J.M., Landing, W.M., Marshall, A.G., Cooper, W.T. 2002. "Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Dissolved Organic Phosphorus Species in a Treatment Wetland after Selective Isolation and Concentration", Analytical Chemistry, 74, 600-606, .

Stenson, A.C., Landing, W.M., Marshall, A.G., Cooper, W.T. 2002. "Ionization and Fragmentation of Humic Substances in Electrospray Ionization Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry", Analytical Chemistry, 74, 4397-4409.

William T. Cooper. 2000. Normal-Phase Liquid Chromatography, in Encyclopedia of Analytical Chemistry, John Wiley & Sons, London.

Fievre, A., Solouki, T., Marshall, A., Cooper, W.T. 1997. "High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Humic and Fulvic Acids using Laser Desorption and Electrospray Ionization", Energy and Fuels , 11, 554-560.

Lavine, B.K., Hendayana, S., He, Y. and Cooper, W.T.1996. "Solid State 13C NMR Studies of Ionic Surfactants Adsorbed on Cyanopropyl Bonded Phase HPLC Columns: Implications for Micellar Liquid Chromatography", J. Col. Inter. Sci. 179, 341-349.