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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
Uranium mill tailings and related forms of low-level radioactive waste contain elevated contents of naturally occurring radionuclides that have been brought to the surface, processed for the recovery of uranium and/or other components and then disposed of in near-surface impoundments. The long-term fate of the tailings and their constituents will be determined by surficial earth processes. Project objectives are to study the chemical form in which radionuclides and selected stable elements are retained in surficial earth materials, particularly uranium mill tailings, and to identify processes operating in natural aqueous and terrestrial systems that may influence the transport of these constituents from these earth...
Reconstructions of continental paleoclimates of the Pleistocene Epoch have relied almost exclusively on packrat midden, lacustrine, and speleothem records. The isotopic (deuterium, oxygen-18, carbon-13) record of calcitic veins marking the sites of fossil ground-water discharge, have not been utilized. Preliminary work indicates that such veins contain continuous dateable records of Pleistocene paleoclimate and paleohydrology. The paleohydrologic interpretations should also be pertinent to selection of sites for the disposal and long term isolation of toxic wastes. Project objectives are: (1) infer paleoclimate and paleohydrology of selected regions based on variations in isotopic content of calcitic veins of ground...
Water quality and pollution contamination depend strongly on geochemical processes involving reactions with mineral surfaces and substrates. Such processes include weathering reactions that contribute dissolved chemicals, sorption that removes aqueous species, and electron transfer mechanisms that establish redox conditions. Although extensive research has been conducted on the aqueous chemistry, minimal information exists on the corresponding solid phases and their effects on chemical transport. Objectives of this project are to: investigate the composition and structure of common mineral surfaces and determine the extent of heterogeneity between specific surfaces and the bulk mineral phase; determine the mechanism...
Saline hydrologic systems provide a wide range of conditions within which to examine hydrochemically important mineral reaction (alteration or genesis) and to better define reactants and products controlling the chemical composition of many natural waters. The effects of complex reactions, in addition to simple solution and hydrolysis, are reflected in relatively gross chemical change and interaction with fine-grained sediment. The objective of this project is to use saline environments to determine mechanisms and relative importance of mineralogic processes which influence the solute composition of natural waters.
<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...
Adequate description of mass transport in hydrologic systems requires knowledge of the rates of the reactions among the gaseous, solid, and liquid phases present. This knowledge of reaction rates is necessary because many chemical reactions occur simultaneously in natural systems, and only a few of these appear to reach equilibrium, even after long contact times. Therefore, a complete description of the chemical processes and their rates will allow realistic modeling of mass transport in natural and perturbed hydrologic systems. The objectives of this project include determining the relative importance of the factors controlling water quality and devising experiments to quantify the process by studying two model...
Categories: Project; Tags: Aqueous Geochemistry
Natural organic polyelectrolytes are highly active materials that are present in practically all natural water systems. They interact with both organic and inorganic pollutants and nutrients, influencing, and in many instances, controlling the toxicity, rate of movement, persistence and rate of degradation of the pollutants and nutrients in aquatic environments. Detailed knowledge of the chemistry of natural organic polyelectrolytes is therefore of primary importance in understanding the chemical changes that affect all of the components of natural water systems. Organic polyelectrolytes are partially eliminated from drinking water by coagulation and chlorination; however, the products of chlorination are not known....
The overall objective of this project is to determine the role of chemical processes associated with dissolved organic carbon (DOC) on the transport and reactivity of both naturally occurring and anthropogenic compounds. Defining the roles of DOC in environmental and geochemical processes is critical to understanding the nature and quality of the Nation’s water resources, and is important for future management of these resources. This field of study has increased in relevancy as numerous environmental problems have been linked to processes involving organic matter. My project attempts to meet these needs by focusing on the chemical mechanisms controlling the fate, transport, and reactivity of naturally occurring...
The increasing need for understanding the effects of human activity on the chemistry of natural systems requires a continually increasing degree of sophistication in the models used to describe the processes through which these effects occur. Such models include thermodynamic and (or) kinetic models of: aqueous speciation, the chemistry of dissolved gases, gaseous and aqueous diffusion, transport of constituents across interfaces, redox processes, mineral-water interactions, the chemistry of anthropogenic inputs to natural systems, and isotope effects associated with these processes. Project objectives are to (1) identify the factors influencing the reactions and transport of solutes in natural waters; (2) evaluate...
Categories: Project; Tags: Aqueous Geochemistry