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The NRP had its beginnings in the late 1950's. Since that time, the program has grown to encompass a broad spectrum of scientific investigations. The sciences of hydrology, mathematics, chemistry, physics, ecology, biology, geology, and engineering are used to gain a fundamental understanding of the processes that affect the availability, movement, and quality of the Nation's water resources. Results of NRP's long-term research investigations often lead to the development of new concepts, techniques, and approaches that are applicable not only to the solution of current water problems, but also to future issues that may affect the Nation's water resources. Basic tools of hydrology that have been developed by the...
Categories: Project; Types: ScienceBase Project; Tags: Acid Mine Drainage, Aquatic Habitat, Arid Land Hydrology, Carbon Cycle, Contaminant Reactions and Transport, All tags...
I conduct research focused on understanding the role of microorganisms on both contaminated and pristine ecosystems. I carry out this work using a polyphasic approach that combines microbiology, molecular biology, and biogeochemistry to understand microbial processes. My work specifically aims to (1) assess the impact of microorganisms on the fate of organic and inorganic contaminants; (2) to investigate the microbial role in metal cycling, e.g., iron, uranium, and manganese cycling; (3) evaluate the potential of microbial populations to contribute to energy resources, either through coal bed methane production or mitigating contaminants due to nuclear energy production or unconventional oil and gas production;...
Robin Stewart's research is focused on identifying and understanding processes influencing the fate and bioavailability of selenium and mercury in food webs across a range of aquatic environments including estuaries, rivers, lakes and reservoirs.
Aquatic humic substances and other classes of dissolved organic material present in natural waters can control the biogeochemistry of trace metals and other solutes and can influence ecological processes in lakes and streams. The nature and reactivity of the dissolved organic material is in turn influenced by biological, chemical, and physical processes occurring in the aquatic environment. Recent advances in isolating and characterizing different fractions of the dissoloved organic carbon (DOC) and in measuring rates of microbial processes can be used to advance the understanding of the dynamic relationship between aquatic biota and dissolved organic material and trace metals in different environments. Project...
Categories: Project; Tags: Metals, Organic Compounds
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...
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...
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
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...
This project seeks to quantify, predict, and project the relative role of plant physiology, among other ecosystem drivers, on carbon, nutrient, and trace-metal biogeochemistry. Approaches span landscape-to-molecular scales as necessary to understand how human and stochastic alterations of wetland structure influence wetland function. Research sites represent a wide range of salinity and management conditions, from rice agriculture to coastal and restored wetlands. Primary goals include evaluating management and modeling approaches to quantify wetland carbon sequestration, greenhouse gas budgets and/or mercury methylation and export.
Research objectives: i) To determine whether metals, including dissolved, colloidal and particulate metals, are bioavailable and toxic to organisms; ii) To characterize and parameterize the physiological and geochemical processes governing metal bioaccumulation, toxicity and ultimately trophic transfer in aquatic ecosystems. iii) To model metal bioaccumulation and toxicity using kinetic models iv) To develop approaches that use isotopically modified metals, metal nanoparticles and metal bound to distinct mineral phases (such as Cu on ferric oxides) to quantify their bioavailability and toxicity to organisms, in particular invertebrates; v) To use enriched metal isotopes to gain mechanistic understanding of...
The overarching objective is to understand how anthropogenic sources of inorganic contaminants (metals) affect the structure and function of aquatic ecosystems. Elements of the research include: 1) develop and apply analytical methods and models to understand and predict metal bioavailability and bioaccumulation in aquatic organisms; 2) define effects of metal exposure on aquatic species; 3) communicate research findings to scientific and regulatory communities to support the management of water resources.
<p>The overall objective of my research is to understand the movement and quality of surface and groundwater using geochemical approaches. Some key issues that are considered in this research are the environmental aspects of energy and mineral resources, climate change, and carbon cycling and sequestration. The geochemical approaches that are used in this research include the use of isotopic tracers, trace elements, and radioisotopes. My research has focused on the sampling and analysis of produced waters from geologic carbon sequestration studies, geochemical characterization of sediment transport in the coastal zone, the environmental chemistry of mercury in coastal regions, and water quality analysis for samples...
General objectives are to 1) add to the fundamental understanding of Se biogeochemistry; 2) document Se sources and assess the environmental impacts of Se contamination; 3) construct and validate an ecosystem-scale Se methodology that connects dissolved Se to bioaccumulated Se within an occurrence of Se exposure; and 4) develop scenarios to illustrate ecosystem foodwebs and hydrologic settings that control Se exposure within a watershed or site as an ecologically consistent management approach for Se. Within that framework, the specific objectives are to 1) quantitatively apply ecosystem-scale Se modeling on a site-specific basis in support of fish and wildlife management or protection through collaboration with...
I conduct field and laboratory research on processes affecting the distribution of inorganic constituents in natural waters. Most of my research focuses on redox sensitive compounds of arsenic, chromium, iron, sulfur, and mercury. I also study conductivity methods and applications for natural waters. Field sites have included the Summitville mine, CO, the Boulder Creek watershed, CO, the Mojave Desert, CA, the Questa mine, NM, and Yellowstone National Park.
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...
To advance understanding of the factors controlling the environmental fate of elements which may be toxic or of other concern (e.g. greenhouse gases). For instance, microbes influence the partitioning of group 15 and 16 elements (Phosphorus, Arsenic, and Antimony; Sulfur, Selenium, and Tellurium) between dissolved and adsorbed phases, strongly affecting the quality of drinking water in aquifers around the world. On another topic, it is well known that methane and nitrous oxide are strong absorbers of IR radiation and act as greenhouse gases near the Earth’s surface. Bacteria in lakes, wetlands, and soils both facilitate and mitigate the flux of these gases and in so doing, shape our world. The primary goal of the...
The project focuses on the use of analytical techniques that we have developed to support a wide range of studies in water-rock interaction, integrating solid phase mineralogy and elemental chemistry and clay mineralogy into hydrologic and contaminant studies.
Micro-organisms alter the chemistry and productivity of aquatic environments by performing complex transformations of organic and inorganic molecules. In many cases, microbes can affect the speciation, mobility, bioavailability, and toxicity of toxic elements, such as Se, Hg, and As. The mechanisms by which these reactions proceed, the in situ rates of the transformation, their quantitative significance to element cycling, the responsible microorganisms and their physiology are only poorly understood. In this project, conceptual models of biogeochemical transformations will be developed by the combination of lab and field experimental work. Laboratory work will focus on identification of biochemical pathways, isolation...
Aqueous chemical models have become popular tools for the interpretation of natural water chemistry. Unfortunately, these models have deficiencies because of (1) incorrect or inconsistent thermodynamic data, (2) invalid assumption regarding the equilibrium state, (3) inappropriate or invalidated corrections for nonideality, (4) inadequate expressions for temperature dependence, (5) invalidated limitations for ionic strength, composition and temperature, and (6) lack of data on solid solution solubility. The plethora of models and databases has prompted federal agencies, especially hazardous waste and nuclear waste managers, to request geochemical code validation. Acid mine waters are a major source of water pollution...