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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;...
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.
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...
The overarching objective of this Project is to determine how and why biogeochemical cycles of macronutrients (i.e. C, Fe, S, etc…) and those for certain trace contaminants (e.g. Hg, Se, As, etc…) covary at the ecosystem and regional scales. General approaches to this end include: comparing and contrasting key biogeochemical pathways both within the sub-habitats of a given ecosystem and among systems that involve a wide range of land-use practices, fostering collaborations with other USGS and non-USGS scientists on projects that are regional in scope, have a fundamental biogeochemical/microbiological focus, and that balance basic environmental research with management / society ‘needs-driven’ research expanding...
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...
1. Riverbank Filtration (RBF) Microbiology: Determination of removal efficiencies of microbes within bank filtration sediments under varied geohydrologic conditions (sediment geology, organic/inorganic geochemistry and flow regime) using flow through, 2-D sand tank, and static minicolumns. 2. Compare RBF attenuation rates for pathogen surrogates (virus to oocyst-sized) to those of natural systems (outflow regions in lakes and ponds) using our previously published methods. These have important implications regarding groundwater under the direct influence of surface water (GUDI). One component involved assessing the subsurface mobility of non-toxic cyanobacteria, subsurface mobility of cyanobacteria and cyanophage...
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...
Our objectives are: • A better understanding of bacteria-contaminant interactions in ground water, because of the persistence of many contaminants in the subsurface environment and because of increasing demands for both high-quality ground water and on-land disposal of toxic chemicals. • A better understanding of microbial transport through the terrestrial subsurface because of the implications for public health (microbial contamination of wells) and because of its roles in groundwater ecology and in the fate of groundwater contaminants.
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...