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Filters: Tags: Radioisotopes (X) > partyWithName: Office of the Chief Scientist for Water (X)

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The purpose of my research group is to develop new methods and applications of environmental isotopes to solve problems of national importance. In specific, the overall goal is to use environmental isotopes, combined with other biogeochemical measurements and hydrologic and biogeochemical modeling, to increase our understanding of biogeochemical and hydrological processes, nutrient and organic matter sources, subsurface flowpaths, and water age distributions in diverse environments. Many of our studies piggyback on the sampling efforts of major monitoring programs to investigate causes of hypoxia and food web problems. Our work provides critical scientific support for these monitoring programs. A long-term career...
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...
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...
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...
The goal of my research is to develop innovative approaches for the detection trace gases and expanding our understanding of their environmental cycles. Dissolved gases can be used as age tracers and climate markers, provide information about biological activity and recharge conditions, and provide unique fingerprints of superficial activity in aquifer systems. This sort of information is valuable to both scientific and resource management communities, and there are many benefits to enhancing our knowledge of the class of compounds.