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Toxic contaminants and naturally occurring substances found in the subsurface can exist in multiple phases, and undergo complex reactions including biodegradation. A comprehensive and quantitative understanding of the processes controlling the fate and transport of subsurface contaminants is necessary to develop policies and strategies for managing water-quality conditions in different land use and environmental settings. Numerical models that simulate flow, transport, and reactions are useful tools for understanding the fate of chemicals in the subsurface when used in conjunction with field and laboratory studies. The research efforts of this project consider flow and chemical behavior in the saturated and unsaturated...
My research focuses on the application of remote sensing to rivers as a means of more efficiently characterizing fluvial systems, primarily channel form and behavior. More specifically, I develop, test, and apply methods of measuring various river attributes, such as depth, streambed composition, turbidity, and flow velocity, from different types of remotely sensed data, including multi- and hyperspectral images and near-infrared and green LiDAR. These techniques provide higher resolution, essentially continuous data over larger spatial extents than could be surveyed via conventional field methods and thus could facilitate river research and management. My research involves a combination of numerical radiative...
Improve understanding of physical and biogeochemical processes affecting water quality of groundwater and surface water. Research focus includes multidisciplinary field and laboratory studies to determine factors affecting sources, movement, and fate of nutrients and reactive inorganic contaminants in the hydrologic cycle. Improve the usefulness of stable isotopes and other environmental tracers in hydrology and biogeochemistry by developing new techniques and approaches. Research topics include analytical techniques for stable isotopes in compounds separated from groundwater and surface water, stable isotope forensics, enriched isotope tracer experiments to quantify transport and reaction rates, field and...
Recent increases in the atmospheric concentrations of carbon dioxide and methane have emphasized the need for a more complete understanding of the processes that control carbon transfer among air, land, and water. Knowledge of the amount, rate and chemical form of carbon transfer across environmental interfaces, such as the land-air and water-air interfaces, is of particular importance. These fluxes are commonly controlled by a combination of physical, biological, and chemical processes at or near the interface. Isolation of the primary mechanisms that determine carbon transfer across the interface allows for development of process-based models that can be used for carbon mass transfer estimates at the ecosystem...
The Reaction-Transport Modeling Group provides environmental managers and policy makers with the understanding and tools needed to predict how decisions made today can improve the amount of clean water available to both society and to nature in the future. In support of the project goals, I have developed the Water, Energy, and Biogeochemical Model (WEBMOD). WEBMOD integrates the latest understanding of hydrologic processes with the full gamut of geochemical simulations available in PHREEQC to simulate conservative and reactive transport of solutes that cycle between the atmosphere, the soils, and bedrock.
Coupled Transport and Geochemical Processes Determining the Fate of Chemicals in Surface Waters
My primary objective is to characterize the hydrology and water chemistry of watersheds and how they are affected by both natural factors and disturbance. I study the role of precipitation type, intensity, and spatial distribution in driving runoff and transport of sediment, carbon, nutrients, and major ions in both disturbed and undisturbed sites. My research incorporates field research and existing climate, hydrologic, and water-quality data to distinguish between the roles of climate, land-cover change, and disturbance in driving watershed processes. I strive to communicate research findings to scientists, regulators, and the public in order to support the management of water resources.
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...
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...
My research program is multifaceted and involves the development of integrated hydrological, geochemical, and biological knowledge on the source-to-receptor approach to assessing impacts of emerging contaminants (hormones, personal care products, pharmaceuticals, commercial cleaning products). This applied research is targeted on issues important to water-resource managers and policy makers, and the results communicated to a spectrum of stakeholders. The current focus of my research is the impact of biologically-active contaminants on aquatic organisms, and the relationship to receiving water (surface water and groundwater) attenuation capacity. Several major classes of contaminants are being investigated – endocrine...