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The goal of my biodegradation research is to understand the processes controlling the rate of biodegradation of contaminants in the subsurface. This understanding will form the basis of methods to increase degradation rates without causing further degradation of groundwater quality. Recent work has focused on the fate of crude oil and agricultural nitrate contamination in the subsurface. Specific objectives for the crude oil research include: (a) determine the rate that contaminants are transported from the source zone; (b) provide an estimate of how long the spilled oil will continue to pollute the groundwater; and (c) determine the fate of products of biodegradation or so-called “secondary water quality impacts”...
Watershed-scale water quality and water availability are affected by the interaction between the landscape and surface and subsurface flows at multiple scales. Wide-spread agriculture leads to diffuse non-point sources of contamination by agricultural chemicals. Localized exchanges of surface water and groundwater through highly reactive streambeds can attenuate the impact of agricultural chemicals on water quality. Thus, understanding the patterns and trends in water quality within a watershed requires analyses at multiple scales to understand hydrologic processes and the integration of hydrology and water quality information. The main objective of my research is to develop a better understanding of the role of...
Quantitative understanding of groundwater and gas-rich fluid- and thermodynamics in volcanic areas is important for several reasons: 1) as a major source of hazard such as propellant in steam-driven explosions, lubricant in mudflows, and transport agent for toxic constituents such as arsenic and mercury that are dissolved from fresh volcanic rock, 2) groundwater pressure, temperature and chemical changes might signal one of the earliest warnings of volcanic unrest, 3) exploration and mining of geothermal energy and mineral deposits. Many of the geochemical, geodetic, and seismic signals measured at the ground surface as part of the volcano monitoring strategies have hydrothermal origins or magmatic origins modulated...
To study the mechanisms, pathways, and rates of transformation of carbon and nitrogen compounds (natural and contaminant) mediated by microorganisms in aquatic habitats and identify factors controlling these transformations and to examine the effect that these transformations have upon other biogeochemical processes.
Our research focuses on developing methods to analyze volcano-hydrothermal systems and on the application of these methods to particular volcanic systems in the western United States. Specific research questions include (1) What are the modes of heat and mass transport from magma to the shallow subsurface? (2) What are the pressure, temperature, and fluid-saturation conditions between magma and the land surface? (3) What controls the permeability of volcanoes? How does it vary in space and time? What role do temporal variations in permeability play in the evolution of volcanogenic hydrothermal systems and episodes of volcanic unrest? (4) How well-coupled are various fluid flow, transport, and mechanical deformation...
Movement of toxic and radioactive substances in aquifer systems occurs in all three phases and is controlled by both hydrologic and chemical forces. Solute movement can be greatly affected not only by physical dispersion, but by other factors such as exchange sorption, chemical kinetics, and ionic distributions. Movement of gases and particulate material in the unsaturated zone are controlled by many additional factors. Knowledge of how these physical and geochemical factors affect prediction of movement of toxic and radioactive wastes is only generally known for ideal systems. This project's objective is to develop field methods and techniques that will yield values for physical and geochemical factors of regional...
Evaluate the hydrologic and geochemical processes that control nitrate fluxes in agricultural settings. Important questions remain about the overall regional and global importance of groundwater nitrogen fluxes, denitrification (microbial reduction of NO 3 − to N 2), and the sources of electron donors contributing to this microbial reaction. Studies are needed that apply robust methods for measuring nitrogen fluxes and denitrification among multiple sites to evaluate important factors affecting N fluxes. These results, in combination with novel methods for efficient estimation of fluxes in groundwater, facilitate estimates of N fluxes in across large regions such as the Corn Belt. Quantify the effects of complex...
Efficient management of ground-water aquifers and geothermal reservoirs requires accurate estimates of the hydraulic properties of water-bearing formations. These are needed to predict water- level changes, aquifer storage capacity, and the rate of movement of chemical species or thermal energy. Analytical models, properly applied, can often be used to estimate the hydraulic and transport properties of complex aquifer systems. This project's objective is to obtain analytical solutions to specific problems of flow and transport in water- bearing formations that can be used for evaluating the hydraulic and transport properties of aquifers and geothermal reservoirs.
To elucidate and quantitatively explain the behavior of hydrogeologic systems typically characterized by hydrogeologic and physics-based complexity and data scarcity, for purposes of developing theory when needed, and with a focus on practical management (use and preservation) of water-resource systems to benefit humankind.
Management of ground-water resources requires that the extent and rate of movement of contaminants in the saturated and unsaturated zones be understood. The contaminants have been and will continue to be both accidentally and deliberately introduced into ground- water systems. Some of these contaminants constitute very hazardous conditions. Because of the immediacy of such contamination problems, understanding of the physical and chemical processes needs to be increased rapidly, and mathematical models derived from this understanding validated and documented. Although the basic mathematical transport models for ground-water systems have been developed, many of the parameters in these models have not been adequately...
Heterogeneous geologic material affects ground-water flow and transport on all scales. On the local scale, changes in hydraulic and geochemical properties can occur over distances on the order of centimeters. On the intermediate scale, the heterogeneity of intra-aquifer depositional layers in unconsolidated material and fractures in consolidated material influences the pathways of ground-water movement. On a regional scale, the heterogeneities due to a really extensive aquifers and confining units affect the flow system in a system wide manner that influences both the boundaries of the system and the generalized pathways of fluid movement in the system. An assessment of the importance of heterogeneity at all scales...
Research goals are (1) to develop reaction-transport models with varying levels of complexity and data requirements, providing guidelines for the appropriate application of these models given field conditions and limited resources; (2) to incorporate the effects of surface-chemistry phenomena into reaction-transport modeling; (3) to develop methods to identify and quantify important chemical and biological reactions affecting transport of inorganic and organic substances; and (4) to compile estimates of reaction rates and reaction-rate laws for chemical and biological reactions. In addition to model development, the project undertakes field, laboratory, and theoretical studies to investigate field-scale chemical...
Improve understanding of physical and biogeochemical processes affecting water quality of groundwater and surface water. Research focus includes multidisciplinary field and laboratory studies to determine factors affecting sources, movement, and fate of nutrients and reactive inorganic contaminants in the hydrologic cycle. Improve the usefulness of stable isotopes and other environmental tracers in hydrology and biogeochemistry by developing new techniques and approaches. Research topics include analytical techniques for stable isotopes in compounds separated from groundwater and surface water, stable isotope forensics, enriched isotope tracer experiments to quantify transport and reaction rates, field and...
Hydrology of Fractured Rocks: My research objectives currently focus on characterizing the heterogeneity of fractured rock properties, and understanding the role of this heterogeneity in groundwater flow, chemical transport, and contaminant remediation. I conduct this research through methods development, field investigations, and numerical modeling. For example, recent research involves numerical modeling of multiple cross hole field aquifer tests in fractured rocks to test hypotheses about the spatial distribution of hydraulic conductivity at different scales. My research also includes collaboration on a range of topics with objectives related to contaminant characterization and remediation in fractured rocks....
Permeability – the ease of fluid flow through porous media – varies about 17 orders of magnitude in geologic media. My research concerns fluid and solute transport in the low part of the of the range (~ 10-19 – 10-25 m2), where measurements are difficult, standard relations such as Darcy’s law are unverified, and unfamiliar phenomena that include osmosis and ultrafiltration affect movement of water and solutes. Testing can sample only small volumes of low-permeability formations, and finding ways to characterize them on regional scales – and thereby detect leakage through fractures and faults - is especially important for problems such as repository siting, CO2 and other waste injection, and protection of aquifers....
The overarching objective of my research is to integrate hydrology, pedology, chemistry, and physics to develop an improved process-level understanding of fluid, solute, and heat transport in unsaturated zones with applications ranging from geologic hazards to carbon storage in soils. I try to develop multi-disciplinary understanding of unsaturated zones in diverse settings with respect to groundwater-recharge and contaminant-transport determining processes, soil formation, and soil-water-plant-atmospheric interactions. I lead teams and work with others to generate individual and multidisciplinary synthesis products that address long-standing problems of fundamental importance to water resources, such as groundwater...
To measure, predict, and understand the flow of water through the soil and rock of the unsaturated zone. Specifically to advance (1) knowledge of aquifer recharge rates for improved management of water resources, (2) the assessment and quantification of hazards from contaminants near the earth's surface, and (3) the understanding of soil moisture processes in relation to ecological habitat. Results are directed toward large-scale problems of water quality, water availability, land-use evaluation, and environmental impacts of climate change.
This project studies evaporation, groundwater mixing, surface-water circulation, groundwater/surface-water interactions, contaminant migration and remediation, and other hydrochemical and biologic processes. The isotope variations are related to (1) purely physical processes, (2) heterogeneous chemical equilibria, and (3) reaction kinetics. The isotope effects of many of these processes are not sufficiently understood or quantified to make the most effective use of stable isotope techniques in hydrologic research. This project aims to develop theoretical and instrumental mass spectrometric techniques through experimental investigation, and to test applications in suitable field locations to improve the utility of...
Develop new micrometeorological approaches and instrumentation to measure ET in a variety of challenging field settings. Develop ET models with applications to specific locations to allow users to predict ET easily and inexpensively. Investigate the performance of micrometeorological methods in complex terrain. Relate changes in ET to changes in weather patterns (e.g. El Nino in a desert setting) or to changes in land use (e.g. agricultural conversion, forest thinning). Develop guidelines for use of micrometeorological methods at limited fetch sites
Plan and conduct research on flow in the unsaturated zone with emphasis on development of experimental techniques and theory to describe the effects of soil physical factors, preferential flow paths, and other physical and chemical parameters of environmental importance on contamination of groundwater.