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Human activities from climate change to waste discharges to water management are modifying ecosystems across the earth, often in ways that are not well understood. This project addresses the problem of better understanding changes in aquatic ecosystems as driven by human disturbances interacting with natural processes. More specifically, the project studies a) the mechanisms of biological and ecological response to stressors such as metal contamination, nutrient enrichment, physical habitat alteration, climate change, and introduced species, and b) the influence of species, communities, and ecosystem processes on the distribution, transport, and fate of chemical contaminants (e.g., metals, nutrients). Most studies...
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....
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.
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....
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...
Many difficult problems in river mechanics may have stemmed from inadequate understanding of the multiplicity and interaction of fluvial processes. Some of the problems may have been solved, but in a very simplified, approximate way. Many efforts have been directed, but without apparent success, to fully account for the causes, occurrences, and mechanisms of catastrophic events, such as flash floods, debris flows, and channel changes resulting from torrential storms, sudden snow or glacier melt, dam break, volcanic eruptions, and earthquakes. Such failures may be partially attributed to the deficiency and incompleteness of existing empirical formulas (or models) representing the relationships between various processes...
Although a major effort has been made to understand the hydrodynamics of surface waters, less effort has been devoted to the study of transport mechanisms and to the development and validation of computational models for simulating the transport of dissolved and suspended materials. Recent progress in hydrodynamics has created additional opportunities for advances in surface- water transport. It may be possible to develop and validate more physically correct descriptions of transport processes in terms of flow characteristics than have been previously available. Microscale processes must be expressed at the macroscale level by algorithms which can be validated in computational models using laboratory and field data....
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...
Climate displays an often-unrecognized order in both time and space. What may appear as a random sequence of precipitation at a point or within a watershed is actually the local expression of a broad integrated system of weather processes that are active on scales of 100’s to 1000’s of kilometers. Only when climate forcings and hydrologic responses are considered from a regional perspective does the order become evident. Understanding these regional processes provides a sound basis for national, regional, and local hydrologic analysis, resource management, and hazard assessment/mitigation. The objectives of this research are (1) to identify and quantify relations between large-scale atmospheric circulation and sea-surface...
The objective of this research is to study and quantitatively describe the factors that influence the response of macroinvertebrates to both anthropogenic and natural environmental factors and assess the effects macroinvertebrates have on the physical, chemical, and biological quality of aquatic systems. This involves 1) studying macroinvertebrate distributions across a range of spatial and temporal scales representing a variety of environmental settings and influences, 2) identifying and measuring the effects of stressors that are macroinvertebrate-specific, 3) identifying the effects macroinvertebrates have on the physical, chemical, and biological environment, 4) developing and applying statistical models that...
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...
The objectives are to 1) Quantify the hydrogeomorphic and ecological controls of nutrient and contaminant fluxes in wetland ecosystems; 2) Scale wetland fluxes from site to watershed scale; and 3) Identify the principals and modeling tools for managing wetland and river ecosystems. The focus will be on floodplain ecosystems, which are poorly studied due to the challenges of working in this environment and their inherent complexity.
Phytoplankton photosynthesis drives many biogeochemical and ecological processes in lakes, estuaries, and the ocean. For example, dynamic changes in pH, trace metal speciation, and concentrations of dissolved gases (oxygen, carbon dioxide, methane), inorganic nutrients (nitrate, phosphate, silicate), and organic compounds (amino acids, organosulfur compounds) are all closely associated with fluctuations in phytoplankton photosynthesis. Trophic linkages also exist, between the phytoplankton as primary producers and populations of consumer organisms including bacteria, zooplankton, benthic invertebrates, and fish. Our scientific understanding of lakes and estuaries as dynamic ecosystems is therefore dependent upon...
I conduct research on the transport and fate of organic contaminants in aquatic systems (terrestrial and marine). This entails field investigations and laboratory experiments that are designed to advance our understanding of natural processes and the effects of these processes on the behavior, mobility, and geochemical fate of organic chemicals of concern. I develop and apply new sampling and analytical techniques, identify potential molecular tracers, and develop models to predict contaminant fate. The laboratory I supervise houses analytical instrumentation that is used for detailed characterization of complex mixtures of organic chemicals as well as quantitative determination of targeted substances at ultra-trace...
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...
Microorganisms catalyze most of the natural redox reactions involving carbon, sulfur, nitrogen, and metals. Thus, geochemical models of the distribution and fate of natural and contaminant compounds must include a microbiological component, which requires an understanding of the physiological characteristics of microorganisms that control the rate and extent of microbially- catalyzed reactions. Project objectives are: (1) to quantify the rates of microbial processes that influence the geochemistry of surface-water and ground-water aquifers; (2) to determine the physiological characteristics that control the rate and extent of microbial processes; and (3) to develop mathematical models of the distribution of microbial...
Categories: Project; Tags: Aqueous Geochemistry, Metals
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.
Human activities from climate change to waste discharges to water management are modifying ecosystems across the earth, often in ways that are not well understood. This project addresses the problem of better understanding changes in aquatic ecosystems as driven by human disturbances interacting with natural processes. More specifically, the project studies a) the mechanisms of biological and ecological response to stressors such as metal contamination, nutrient enrichment, physical habitat alteration, climate change, and introduced species, and b) the influence of species, communities, and ecosystem processes on the distribution, transport, and fate of chemical contaminants (e.g., metals, nutrients). Most studies...
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.