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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 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.
To measure, predict, and understand the flow of water through the soil and rock of the unsaturated zone. Specifically to advance (1) knowledge of aquifer recharge rates for improved management of water resources, (2) the assessment and quantification of hazards from contaminants near the earth's surface, and (3) the understanding of soil moisture processes in relation to ecological habitat. Results are directed toward large-scale problems of water quality, water availability, land-use evaluation, and environmental impacts of climate change.
Determine source and sink strengths and environmental controls of greenhouse gases at the Earth’s surface and the role of management in modulating the exchange near the surface. Evaluate the role of land use and climate change on evapotranspiration rates over various land surfaces toward regional assessments with the aid of models and remote sensing.
Characterizing Groundwater Flow and Chemical Transport in Fractured Rock From Meters to Kilometers: The objectives of my research are to develop a conceptual understanding of geologic, geochemical, and biological processes that affect groundwater flow and chemical transport in complex geologic settings, such as fractured rock and karst aquifers, and to test hypotheses under field scale conditions. Because the geologic complexity of fractured rock and karst aquifers can manifest itself differently over increasingly larger physical dimensions, the formulation of hypotheses and the design of field scale experiments are undertaken over physical dimensions that range from meters to kilometers.
Objectives are quantitative scientific examination of hydrologic processes in the near-stream environment to determine spatial and temporal patterns of stream exchanges with shallow ground, for the purpose of improved understanding of streambed exchanges and resulting impacts on water resources and stream ecology.
My primary objective is to understand the function of the benthic community at various spatial scales with the goal of understanding and modeling the benthic community processes at the ecosystem level. Specifically, my goals are to (1) explore ecological and physical processes that are affected by the benthic community and that effect benthic community composition and function; (2) look at these processes at a variety of time scales (days to seasons and inter-annual time scales) so that hydrologic, climate, and exotic species effects on benthic communities and their ecosystems can be understood; (3) develop habitat and energetics models of dominant members of the benthic community that can be dynamically linked...
The responsible use of our Nation's ground-water resources requires an ability to predict changes in water quality as a result of human impacts. Prediction of chemical quality in the ground-water environment depends on a detailed understanding of both chemical and hydrologic processes. To determine the spatial and temporal variability of ground-water quality, it is necessary to identify reactions occurring in the system, to define their kinetic and thermodynamic properties, and to determine how the configuration of the hydrologic regime influences ground-water quality. The objectives of this project are to: (1) identify chemical reactions in ground-water systems using observed chemical and isotopic composition of...
Coupled Transport and Geochemical Processes Determining the Fate of Chemicals in Surface Waters
Sediment moves through a river system in response to specific events and changing conditions in the drainage basin. The movement of sediment is usually discontinuous. Episodes of movement are separated by periods of storage that can range from less than a year to more than one thousand. Understanding the movement and storage of sediment in rivers is important to navigation, flood control, and other aspects of river engineering, as well as to the prediction of the fate of contaminants adsorbed on sediment particles. This project's objectives are to assess: (1) changes in river sediment loads over periods of decades or longer, and the factors (natural or artificial) that cause the changes; (2) rates at which sediment...
There is a general lack of knowledge of fundamental processes governing the fate and transport of anthropogenic organic compounds in surface and ground waters. Interactions of organic contaminants with natural organic coatings on sediments and aquifer porous media are not well understood. Furthermore, abiotic and biological transformations of organic contaminants in surface and ground waters require extensive fundamental investigations if their effects on Water Quality are to be understood. Objectives are to (1) determine physicochemical and biological processes, controlling the fate and transport of organic compounds in surface and ground waters; (2) determine bioavailability of hydrophobic organic contaminants...
The biological and chemical characteristics of aquatic environments depend on a generally complicated balance of physical, chemical, and biological processes. Basic to describing these characteristics is an understanding of transport processes including both advection and mixing. For a given water body, these processes depend heavily on the mass, momentum, and energy transfers at boundaries and the internal response of the system. Many of these transfers and responses are poorly understood. Broad goals of this project are to quantitatively understand the physical processes responsible for the transport of conservative and nonconservative solutes of biological and chemical importance. Through the use of time series...
Categories: Project; Tags: Solute Transport
To better understand climate variability and possible climate change effects on surface hydrology, water resources and related natural and human managed systems in the western U.S., with emphasis on California.
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.
Research Objectives: To better understand the response of watershed hydrology, freshwater management and estuaries to climate variability and change. In the estuarine component of this research, there is an emphasis on the responses of physical processes that drive ecological variability and change.
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.
In recent years, there has been increasing interest and study concerned with the possible relations between the chemical quality of natural waters and human health and disease. Medical researchers recognize areal patterns of health and disease in the U.S. and suspect that these patterns may be controlled by both environmental and non-environmental factors. After excluding non- environmental factors, it appears that local and regional differences in water quality may have an effect on health and disease. Such differences influence the total dietary intake of necessary major and trace elements and the concentration of certain potentially toxic chemical constituents. The objective of this project is to discover and...
Categories: Project; Tags: Water Quality
Wetlands are hydrologically controlled ecosystems essential to estuarine, marine, lacustrine, and riverine productivity. To improve our understanding of these ecosystems we need information on (1) wetland hydrologic variables/ budgets and their relation to wetland vegetation and nutrient cycling; (2) wetland dynamics and boundary fluctuations; (3) wetland functions and values; and (4) short- and long-term temporal changes. Wetland plants may serve as sensitive hydrologic indicators of water-quality parameters such as salinity, turbidity, pH, nutrients; presence of various pollutants; or frequency and duration of inundation. Submersed aquatic wetlands have many functions including (1) providing habitat for invertebrate...
Categories: Project
Managing water use in riverine and estuarine systems requires an understanding of the governing supply, circulation, mixing, and flushing processes. Qualitative and quantitative evaluation of the hydrodynamic and transport properties of such water bodies can be computed via mathematical/numerical simulation models. To accurately simulate both the temporal and spatial variations of the flow, which significantly define the transport processes, the simulation model must be capable of accounting for hydraulic and tide-induced fluctuations, water withdrawals, discharges, winds, nonuniform geometric configurations, and other manmade or natural factors. Objectives of this project are to investigate and develop various...