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Hydrogeology and Environmental Science

Investigation of how physical, chemical, and biological processes influence soil development, groundwater flow, and the fate of microbial and chemical contaminants in modern surface and near-surface environments.

Annette Engel conducts interdisciplinary research that includes cave and karst aquifer evolution and speleogenesis, the role of natural organic matter in karst, geochemical controls on microbial metabolism, oil degradation and trajectories following environmental disturbances, the biodiversity of cave systems and coastal marine habitats, and symbiotic associations between bacteria and clams, invertebrates, and alligators. Her research falls broadly within the discipline of geomicrobiology, the study of the interactions between microorganisms and their geological and geochemical surroundings. Research involves a range of classical inorganic and organic geochemistry, stable isotope geochemistry, and molecular genetics methods within a microbial systems biology approach. Much of the instrumentation is available in Dr. Engel's laboratory. To quantify inorganic and organic compounds in water and gases, she applies basic wet and dry chemistry methods, ion chromatography, UV-Vis and fluorescence spectroscopy, Fourier transform infrared spectroscopy, gas chromatography, gas chromatography-mass spectrometry, and inductively coupled plasma mass spectrometry. She also uses X-ray diffraction and X-ray absorption spectroscopy using synchrotron radiation to understand mineralogical and elemental composition of natural materials. She uses stable isotope geochemistry, specifically of carbon, nitrogen, and sulfur, to characterize microbial signatures in water and sediment. For systems biology, she applies genomics and bioinformatics approaches that include DNA amplification protocols for PCR and quantitative PCR, and different gene sequencing methods, including next-generation high-throughput 454 and Illumina platform sequencing technologies to obtain DNA-based gene sequences and metagenomes ("who is there?") and also RNA-based transcriptomes ("what are they doing?") from environmental samples. To investigate metabolic potential directly from a sample, she routinely uses classical culturing methods and enzymatic assays. She also examines samples microscopically using gene probes for a full-cycle approach, where she can obtain genetic information and then probe material with specially designed probes to target specific microbes."

Terry Hazen's lab is a diverse group of scientific post doctoral fellows, research associates, technicians, and students in microbial ecology and environmental engineering. The primary research emphasis of the lab is basic and applied field microbial ecology, especially as it relates to bioremediation, biofuels, enhanced oil recovery, and water quality. The overarching vision for the lab is understanding the fundamental concepts of systems biology and environmental stress response pathways from the molecular to the ecosystem level to improve our knowledge of fundamental biogeochemistry and suggest exciting new applications that are relevant to the world's current problems. We have labs at both UT and Oak Ridge National Lab and active field studies in Puerto Rico, Alaska, Gulf of Mexico and Oak Ridge.

Melanie Mayes is Joint Faculty with the Climate Change Science Institute and the Environmental Sciences Division at the Oak Ridge National Laboratory. She conducts interdisciplinary research in carbon and nutrient cycling and in the fate and transport of metals, organics, and other contaminants in soils and rocks. She designs experiments to build better models of natural processes and is interested in diverse research at the intersection of water, minerals, solute chemistry, and biological cycling.

Her current research includes developing a mechanistic soil carbon cycling model that includes measurable soil carbon pools, sorption and desorption of dissolved organic carbon, and extracellular enzyme-facilitated decomposition of organic matter. The project also uses neutron reflectometry and molecular dynamics simulation to synergistically derive information on the molecular-level structure of organic carbon stabilized on soil minerals. She is actively involved with contaminant fate and transport, with two projects investigating the fate and transport of radionuclides and explosives, respectively, in aquifer materials at Departments of Energy and Defense facilities.

Larry McKay's research interests include: hydrogeology of fractured clay-rich residuum, fractured shale and glacial clay till; fate and transport of a variety of contaminant types, including industrial solvents, coal tar, radionuclides, explosives and pathogens; shale weathering; and paleosols. Dr. McKay was selected as the 2008 GSA Birdsall-Dreiss Distinguished Lecturer and visited approximately 55 universities or research institutions to give research talks.

Michael McKinney's research interests have generally focused on biological issues. He works on topics relating to modern biodiversity issues, such as the effects of urbanization on biodiversity, and especially how human activities are homogenizing the biosphere. I have served on the editorial boards of Evolutionary Ecology Research and Animal Conservation

Ed Perfect's research interests are centered on relations between pore space geometry and soil/rock hydraulic and chemical transport properties, as well as understanding the scale-dependency of these relations. Current research topics include:
Movement of chemicals in soil and rocks, and the resulting implications for agriculture and the environment, are topics of widespread public and scientific interest.  To control ground water pollution we must be able to predict transport processes within the variably-saturated (vadose) zone; contaminants must pass through this zone in order to reach groundwater.

Despite recent increased awareness of the critical role that the vadose zone plays in the hydrologic cycle, key constitutive relationships such as the relative permeability function are rarely determined directly.  Furthermore, existing models that are used to predict flow and transport in the vadose zone are often unreliable because they are based on empirical parameters that cannot be readily upscaled from the laboratory to the field.

My research mainly focuses on the development of more physically-based constitutive relationships for variably-saturated porous media.  I am particularly interested in the use of fractal geometry to model and upscale these relationships.  I am also investigating new/improved experimental techniques for measuring their input parameters.  My research program involves a combination of theory development and modeling, laboratory experimentation, as well as some fieldwork.  It always includes a strong quantitative component, and often involves the use of statistical analyses.

Recent and ongoing research projects can be grouped into the following categories:

Fractal modeling of soil and rock physical properties

  • modeling pore space geometry as related to hydraulic properties

fractal and lacunarity analyses of rock fracture patterns

  • upscaling aquifer/reservoir heterogeneity using geometrical multifractals
  • multifractal analysis of grayscale images

Measuring hydraulic properties

Centrifuge system used for measuring relative permeability

  • determining point estimates of the capillary-pressure saturation relation
  • measuring relative permeability by transient flow centrifugation
  • electromagnetic methods for measuring soil water content
  • using neutron computed tomography to "see" the phase structure of water in porous media

Transport of chemicals and micro-organisms

  • predicting steady-state transport parameters from static physical properties
  • transient methods for determining transport parameters
  • transport of uranium in partially-saturated, coarse-textured sediments

Soil aggregation and carbon sequestration

Centrifuge system used for measuring particle-size distribution

  • determining the aggregate-size distributions of soil & marine sediments
  • use of SAXS and SANS to quantify pore-size distributions and pore-scale carbon contents
  • modeling geologic carbon sequestration in deep brine aquifers

I strongly believe that, because of their complexity, most vadose zone problems require a multidisciplinary approach.  My training and experience has been in Soil Physics, Hydrogeology, and Physical Geography.  While many of my primary research collaborations are with colleagues in these three areas, I enjoy working with scientists and engineers from a variety of different disciplines.  This is perhaps not surprising given my own diverse background.  Over the past few years I have worked closely with Agricultural Engineers, Applied Mathematicians, Chemists, Civil Engineers, Geophysicists, Microbiologists, Nuclear Physicists, Soil Chemists, and Structural Geologists on various projects.

My long-term goal is the development of a suite of physically-based, readily-measurable hydraulic functions that hopefully will supplant some of the more empirical approaches currently in use.  Much of my work has been at the pore-scale.  However, I am also interested in the measurement and analysis of large-scale physical properties and processes

Anna Szynkiewicz's interests involve studies of global geochemical and biogeochemical cycles related to the lithosphere and hydrosphere using stable isotope tracers (S-O-H-C-Zn) and chemical methods. This interdisciplinary research integrates areas of low-temperature geochemistry and water-rock interaction, hydrogeology, and environmental studies. Szynkiewicz is trying to integrate these fields in order to better quantify the chemical weathering of crustal rocks as a result of climate and to enhance knowledge and understanding of modern and past hydrological cycles on Earth.

Szynkiewicz also attempts to elucidate human impacts such as land cultivation and hydraulic fracturing on natural ecosystems. Consequently, her recent environmental studies have been focused on characterizing sources of salinity in agricultural districts of Chihuahuan and Sonoran Deserts as well as investigating sources of methane in groundwater of Central Appalachian Basin impacted by hydraulic fracturing and surface mining. Major research findings of these studies have been published recently in Chemical Geologyand Applied Geochemistry.

Szynkiewicz's earliest research focused on the characterization of anthropogenic impacts on freshwater environments in Eastern Europe related to acid rain in mountain and lake ecosystems. She used multiple stable isotope tracers (S-O-H-C) to calculate the sulfate inputs from atmospheric acid wet deposition and performed several incubation experiments to evaluate the buffering capacity of lake sediments in response to anthropogenic acidification of freshwater. Major research findings of these studies have been published in Chemical Geologyand Applied Geochemistry.

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