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I conduct long-term investigations on the fate and geochemical effect of organic contaminants in subsurface environments. I use a combined field and laboratory approach in a variety of hydrogeologic environments in order to meet these objectives. The principal questions being addressed by this project are: 1. How do long-term changes in biogeochemical processes affect the fate of organic and inorganic constituents in aquatic environments? and 2. Does availability of electron acceptors and electron donors control the progress of degradation reactions? My overarching objective is to increase our understanding of the transformation of contaminants from hydrocarbon spills, wastewaters from oil and gas development,...
Dams have been built in this century that impound virtually all major rivers in the United States. The purposes vary and include flood control, navigation, hydropower generation, and storage for irrigation and domestic uses. About 2,500 reservoirs of 5,000 acre-feet or more, store about 480 million acre-feet, about 1/4 of the annual runoff. Storage capacity is dominated by large reservoirs such that the 600 largest store more than 90 percent of the total. Lake Powell, behind Glen Canyon dam, stores water (ca. 27 million acre-feet) in the Upper Basin of the Colorado River for controlled release according to the Colorado River Compact (8.23 million acre-feet per year) and to generate electricity for sale to consumers...
Categories: Project; Tags: Lakes, Water Quality
Analysis of heat and fluid flow in geothermal systems is needed to adequately describe both the natural state of such systems and their response to fluid production for energy development. The analysis may involve analytical or numerical solution techniques, but requires delineation of realistic conceptual models for specific geothermal systems. This, in turn, requires the collection and synthesis of geologic, geophysical, geochemical, and hydrologic data. Periodic monitoring of changes in geothermal systems, including surficial thermal manifestations, can aid in understanding the natural conditions of flow and effects caused by crustal unrest and geothermal development. Objectives are to elucidate the processes...
Categories: Project; Tags: Geothermal Resources
The determination of inorganic constituents and their impact on water quality requires an in-depth knowledge of the interactive water chemistry relationships. The ability to measure trace and ultratrace concentration levels of inorganic constituents as well as their chemical form and speciation plays a significant role on the chemical, toxicological, transport and overall environmental impact on surface- and ground-water hydrology. The development of state-of-the-art analytical chemistry technology to the solution of specific hydrologically related problems requires extensive laboratory and field research and development effort. Project objectives are to (1) Investigate and develop new concepts and approaches to...
Categories: Project; Tags: Trace Elements, Water Quality
Many hydrological and geochemical processes associated with lakes and wetlands are poorly understood. Characteristics of wind and vapor profiles over lakes, which are basic controls on evaporation, have been studied in detail for only a few large reservoirs in the western United States. Many commonly used methods of estimating surface runoff to lakes and wetlands, are inaccurate. Hydrogeologic controls on seepage to and from all surface-water bodies have not been studied adequately, either from theoretical or field perspectives. Research on these components of lake and wetland hydrology is especially critical to individuals responsible for management, protection, and restoration of these resources. The major objective...
My research objectives include characterization of dissolved and particulate natural organic acid influence on the reactivity, bioavailability, and mobility of metal ions and inorganic surfaces in aquatic environments. An important research objective of my project is examination of formation and dissolution rates of carbonate minerals. Biocalcification is a significant carbon sink in the world carbon budget and requires further investigation. I study aspects of biocalcification processes that proceed through a highly unstable calcium carbonate polymorph – amorphous calcium carbonate (ACC) stabilized by organic acids. I use chemical thermodynamics and kinetics to better describe and predict the fate and distribution...
Develop, enhance, and extend theory and methods to investigate and characterize fluid flow, solute transport, heat transport, and stress/deformation changes in fractured and porous media for application to diverse areas, including the assessment of groundwater availability in bedrock terrains, remediation of contaminated sites, and evaluation of potential hazards such as induced seismicity from fluid injection.
The intrusion of industrial, agricultural and domestically produced organic chemicals and wastes into the aquatic environment is a well known reality and is considered to be one of the most important environmental problems. The widespread finding of these anthroprogenic substances, in addition to naturally occurring organics, and their detrimental impact on the Nation's water resources points to our need to understand how these substances act and react in the environment. Knowledge of transport, persistence, transformation, solubility, sorption, and reaction kinetics is needed to determine the fate of the substances in the hydrosphere. Objectives of project are to (1) identify organic substances associated with...
Categories: Project; Tags: Contaminants, Organic Compounds
Research Objectives: Brian uses field and laboratory measurements combined with numerical modeling to understand hydrologic processes and problems in disturbed landscapes. His research seeks to understand water and solute movement, plant community recovery, and the changes in hydrologic processes and associated water resources after landscape disturbances. Brian's work spans multiple scales, investigating the plot- and catchment-scale processes that dictate the emergent behaviors observed at watershed scales. Additional research interests include hydrologically-driven slope failure, sediment transport, soil physics, contaminant transport, and surface-water/groundwater interaction.
Temperature and salinity are two key estuarine habitat variables. Understanding how these variables are distributed around the bay leads to a better understanding of habitat types and distribution in the Bay. Additionally, understanding the distribution of salinity in the Bay allows us to better understand the transport processes that drive material transport and supply throughout the Bay. Time series of water temperature and specific conductance (salinity is calculated from conductivity and water temperature) are needed (1) to improve our understanding of the hydrodynamics of the estuary (e.g., gravitational circulation), (2) for calibration of multi-dimensional flow and transport models of the Bay, (3) to better...
I am interested in landscape dynamics, generally focused on understanding and predicting changes in the patterns and functions of landscapes in response to anthropogenic effects. The objectives of my research are to gain an understanding of the processes that control landscape form and function as well and key interactions between hydrology, sediment transport, climate, vegetation, and human impacts in a variety of settings. Examination of these processes and interactions in different environments can ultimately lead to a more general and regional perspective of landscape morphodynamics and evolution. The recent research that I have initiated at USGS is a reflection of my direction and interests. I am keenly...
My research program is multifaceted and involves the development of integrated hydrological, geochemical, and biological knowledge on the source-to-receptor approach to assessing impacts of emerging contaminants (hormones, personal care products, pharmaceuticals, commercial cleaning products). This applied research is targeted on issues important to water-resource managers and policy makers, and the results communicated to a spectrum of stakeholders. The current focus of my research is the impact of biologically-active contaminants on aquatic organisms, and the relationship to receiving water (surface water and groundwater) attenuation capacity. Several major classes of contaminants are being investigated – endocrine...
The responsible use of our Nation's ground-water resources requires an ability to predict changes in water quality as a result of human impacts. Prediction of chemical quality in the ground-water environment depends on a detailed understanding of both chemical and hydrologic processes. To determine the spatial and temporal variability of ground-water quality, it is necessary to identify reactions occurring in the system, to define their kinetic and thermodynamic properties, and to determine how the configuration of the hydrologic regime influences ground-water quality. The objectives of this project are to: (1) identify chemical reactions in ground-water systems using observed chemical and isotopic composition of...
Reconnaissance and chemical and isotope sampling of thermal springs in the western United States has not generally provided information of sufficient detail to permit the geothermal potential of most individual areas to be determined with any certainty. This is especially true in the Cascade Mountain Range, where the chemical geothermometers indicate much lower temperatures of water-rock equilibrium than the sulfate-isotope geothermometer and the geologic setting seem to require. This discrepancy could be due to simple mixing of thermal and fresh water or rapid equilibration of water with the surrounding country rock as the fluids rise to the surface; alternatively, the sulfate-isotopic composition could be an artifact...
The broad objective of my research is to determine rates and controls of organic carbon metabolism as a fundamental component of the terrestrial-aquatic-atmospheric exchange of carbon. I quantify the relative importance of intrinsic substrate properties and environmental variables to carbon metabolism, and the impact of climate change and other disturbances. I combine field and laboratory study approaches to understand the numerous controls on carbon cycling processes. Much of my research has focused on boreal and arctic systems, where nearly ½ of the global soil organic pool resides and is vulnerable to climate change. My research objectives in boreal and arctic regions include: 1) quantifying the release...
Biotic responses to climatic change or human manipulation are inherently complex because of wide differences in organism sensitivities and response times, the influence of history and scale, and the various interactions between organisms and with the physical system. In arid and semi-arid lands, which cover about 12.5 percent of the Earth's land surface, the effects of climatic variability on vegetation are greatly magnified, particularly because most plants exist near their physiological limits. How arid land vegetation might in turn affect climate is uncertain, though there is some indication that decreasing cover and increasing albedo could promote regional drought. Whether in response to projected Greenhouse...
A large amount of geophysical data is recorded in water wells and test holes but interpretation is subject to significant uncertainties. The data are used in ground-water models; to evaluate potential waste disposal sites; the effects of ground- water contamination, and to guide aquifer development, including geothermal reservoirs. The development of quantitative log interpretation techniques to derive more accurate data and to evaluate the statistical uncertainties in the data will reduce costs in ground-water investigations. Project objectives are to evaluate presently available logging equipment and log interpretation techniques and develop improved instrumentation and analytical techniques for specific ground-water...
Categories: Project; Tags: Fractured Rock, Hydrogeology
Benthic invertebrate communities, composed of sessile, relatively long-lived species, provide a record of effects of short- and long-term environmental changes through species composition and abundance changes. Thus, they are often used as water-quality indicators. However, their use in water-quality studies requires assumptions that communities remain at steady state except when influenced by human activity. Long-term studies show that natural variation over a variety of time scales often masks human-induced changes. Estuarine benthic communities, often dominated by suspension feeders, have an unknown but potentially large controlling effect on phytoplankton biomass, and thus may be important in limiting eutrophication....
Categories: Project
The Tropical and Arid Regions Climate Project seeks to quantify past variations in climate and the hydrologic balance through studies of paleo and modern surface- and ground-water systems using stable isotope and other chemical methodologies. Objectives of the Tropical and Arid Regions Climate Projects are to determine: (1) the frequency and severity of drought during the past 10,000 years, (2) the frequency and severity of major cooling events that led to glacial advances in the Colorado Rockies, (3) the frequency of hurricanes that impacted the Carribbean and Gulf of Mexico over the past 400 years, and (4) the impact of climate change on prehistoric Native Americans.
Many aspects of ground-water flow and transport resist standard, deterministic modeling techniques: either there exist elements which are overly complex or which are simply unpredictable. These elements may have either a spatial character, as heterogeneity in porous media, or a temporal character, as recharge events to an aquifer. Provided that an adequate representation can be found, then these aspects of flow and transport frequently are better modeled by taking the complex or unpredictable element to be a stochastic process. Given an adequate representation, then the following questions may be addressed: (1) What is the implication of these elements for flow and transport in porous media? (2) Given observations...
Categories: Project; Tags: Statistical Hydrology