Ph.D., 2005 University of New Hampshire, Durham, NH, USA

SES 2446
Phone (312) 996-7207
ebowley@uic.edu

Methane and nitrous oxide emissions from restored wetlands exposed to elevated nutrient loads.

Ph.D., 2006 Université d'Orsay - Paris XI & Commissariat à l'Energie Atomique (CEA-Saclay), Orsay, France

SES 2456
Phone (312) 413-8271
smekki@uic.edu

Study of uranium-silicate formation kinetics in low temperature aqueous solution.

In the plutonium-production facilities at the U.S. Department of Energy's Hanford Site, radioactive liquid byproducts were stored in large buried tanks, constructed in clusters, or 'tank farms.' One of the tank farms was constructed in 1946 specifically to store and separate solid waste sludges and liquids. While transferring sludges tank-to-tank in 1951, an inter-tank pipeline ruptured, and about 350,000 L of waste were released to the ground, including more than 7000 kg of uranium in alkaline media (also containing sodium carbonate, nitrate, phosphate, and sulfate). Beneath the tank farm, a groundwater contaminant plume, 250 m wide and 900 m long, has been shown by uranium isotopic analysis to originate from the 1951 leak. As a radiochemist, I am currently taking part in a research project with Pr. Kathryn Nagy and Pr. Neil Sturchio, to synthesize and characterize the different uranium species that may form in the presence of minerals (feldspar and quartz) and groundwater simulating the vadose zone chemical conditions of the Hanford Site. We are collaborating with Lynda Soderholm of the Chemistry Division at Argonne National Laboratory to obtain insight at the molecular scale of the local structural environment of uranium species (3-8 Å) using X-ray scattering and spectroscopic methods (High Energy X-ray Scattering (HEXS), EXAFS spectroscopy). We hope to construct a complete description of the formation, structure, and chemical influences on the existence of different U species observed in the Hanford subsurface. My previous work is related to the characterization of luminescent heavy metals (europium and uranium) complexes in novel solvents, Room Temperature Ionic Liquids (RTILs, which are inflammable, nonvolatile, and recyclable), potentially usable to replace traditional organic solvents (volatile, polluting, and flammable). The main goal was to understand fundamental solvation processes of the luminescent probes and then design a new extraction path of the heavy metals as a possible replacement for traditional nuclear fuel reprocessing (involving hazardous volatile organic compounds). A biphasic extraction system using 'green solvents' - Supercritical carbon dioxide and RTILs - in conjunction was investigated and showed quantitative extraction efficiencies (> 95 %) of CO₂-philic ligands/metal complexes.

Ph.D., 2005 Institute National Polytechnique de Lorraine, Nancy, France

SES 2456
Phone (312) 413-8271
yokochi@uic.edu

Noble gas geochemistry: Hydrosphere, Atmosphere and Mantle

Noble gases (He, Ne, Ar, Kr, Xe) are inert and highly volatile elements. As their inertness keeps them from complicated processes involving chemistry, they are the simplest (thus the best!) tracers of physical processes such as mixing and kinetic fractionation. Several radiogenic and radioactive isotopes also provide useful chronometers.

I am currently taking part in a research project involving 81Kr (half life = 229,000 yr) and 85 Kr (half life = 10.8 yr) with Neil Sturchio. Radiokryptons are ideal tracers of water ventilation ages, which can be used to constrain flows rates and/or mixings of subsurface waters. The recent development of the ATTA instrument (atomic trap trace analysis) at Argonne National Laboratory makes it possible to analyze these extremely low abundance (<10E-11) isotopes. We are in progress of constructing a system to extract and purify krypton dissolved in water for the analysis using ATTA.

My previous works are related to non-radioactive noble gases and nitrogen which is occasionally considered as "6th noble gas". Because primordial volatile elements are preserved in the Earth's mantle, analyses of noble gases in mantle-derived samples can shed light on the origin of the atmosphere. My favorite work among those is based on the xenon isotope systematics of mantle-derived samples from the Kola Peninsula, Russia, from which we proposed that the primitive degassing of the Earth continued over several hundreds of Myr, over Hadean.