A.1. Need for Education and Research in Quantitative Contaminant Hydrogeology
Fundamental and applied problems related to the contamination of the subsurface environment are receiving attention at local, national, and international levels. Groundwater contamination is an urgent issue confronting us daily as our growing population requires both an increasing supply of good quality water and the means for safe disposal of increasing amounts of chemical wastes. Improved understanding of physical, chemical, and biological processes affecting the extent, migration, or remediation of subsurface contamination will lead to more successful recovery from current contamination and will guide better utilization of our Nation's resources in the future.
Research involving faculty and graduate students at the University of Virginia is addressing some of the pressing technical issues of groundwater contamination. Over the last decade, funded research programs at University of Virginia have studied the impact and remediation of acid mine drainage, biodegradation of organic compounds in soils, and the intrusion of seawater into coastal fresh groundwater supplies to name a few. The frontier issues in groundwater and soil water contaminant fate and transport that are currently being investigated include the transport of biocolloids in porous media, the kinetics of biological mediation of groundwater geochemistry in the presence of toxic organic compounds, the transport modeling of reactive solutes and particles, the migration of chemotactic bacteria, the potential for colloids to facilitate the migration of agricultural chemicals in groundwater, and the quantification, simulation, and design of in-situ bioremediation. This set of issues is of particular relevance to current concerns about hazardous waste in the environment. Because of the complexity of our natural environment, especially when contamination is considered, progress on any one of these questions has required interaction among specialists in different fields.
Research and teaching activities involving faculty in the Departments of Chemical Engineering, Civil Engineering, and Environmental Sciences have focused on groundwater in the shallow subsurface, including the unsaturated and saturated zones of soil and bedrock. The questions are fundamental. The approach is one that combines field observation, experimentation at different scales, and quantitative modeling. Recognizing that contaminants may be inorganic chemicals, organic chemicals, or microorganisms, it is clear that the physical environment of groundwater flow and contaminant transport, the chemical environment of contaminant-water-rock interactions, and the biological environment of microbially mediated processes will act to influence the fate of contaminants in a complex and interconnected way. In current research, all aspects of the fate of contaminants are examined through interdisciplinary study. The ultimate goal of such work is to develop predictive capability in describing contaminant behavior in the subsurface environment.
Because of the critical national need for trained technical people in the area of contaminant hydrogeology, because of the demand for an education in this interdisciplinary area by an increasing number of students from traditional backgrounds, and because of the outstanding record of research productivity on these interdisciplinary problems at the University of Virginia, we seek the award of a Camille and Henry Dreyfus Postdoctoral Fellowship in Environmental Sciences. We believe that the University of Virginia's Program of Interdisciplinary Research in Contaminant Hydrogeology (PIRCH) can offer a postdoctoral fellow the best opportunity in the Nation to broaden her or his experience from training in chemistry or chemical engineering through research in environmental sciences. In making this award to the University of Virginia, an opportunity to train a postdoctoral fellow for research and education in an interdisciplinary field of emerging national importance and in an educational environment free of cultural and gender bias will be secured. Furthermore, by recruiting a talented individual from another program, someone with technical skills not reproduced here, we can strengthen PIRCH even further to the benefit of current and future students and faculty.
A.2. Integration of Component Disciplines
Contaminant transport in the subsurface and its degradation by biological agents (bacteria) is a complex phenomenon requiring the synergistic integration of knowledge from several disciplines. In order to understand the mechanisms underlying the observed phenomena, insight is required into the geochemistry of the subsurface, the fluid mechanics of colloidal transport and two phase flow (particularly through a porous media), the biophysics of bacterial transport, and the kinetics of biodegradative processes. This insight can then be combined with concepts common to the engineering disciplines in order to model, simulate, and ultimately predict in a quantitative way the transport of contaminants and the movement of bacteria through the subsurface. These methods, which can be grouped together under the general rubric of quantitative contaminant hydrogeology, can then be used to design and optimize strategies for biological remediation and environmental restoration of contaminated sites.
The PIRCH faculty represent a unique combination of experts in the major theoretical and experimental areas required to significantly impact the critical emerging field of quantitative contaminant hydrogeology. We have illustrated this in Figure 1 by indicating at the vertices of the triangle the research strengths of each of the groups in the participating departments. At the center are the research thrusts which draw upon these strengths. Those research frontiers that could not be comprehensively addressed without the proposed interdisciplinary effort are:
· fundamental processes of bioremediation: e.g., bacterial migration through porous media and adsorption onto surfaces, chemotaxis (ability of bacteria to orient otherwise random motion in the direction of increasing concentrations of the contaminants they are degrading);
· simulation and design: e.g., simulation of fate and transport of contaminants and optimal design of bioremediative treatment strategies.
The goal of our proposed postdoctoral fellowship is to train the candidate in interdisciplinary research in Environmental Sciences, Chemical Engineering, and Civil Engineering with a unique combination of knowledge and skills that will enable her or him to make a significant contribution toward solving our national problems of groundwater contamination. Another important aspect of such experience is learning to interact effectively with researchers in other disciplines than one's own, by knowing the language and having a base-level understanding of the questions and approaches of an allied discipline.
A.3. Evidence of Research and Teaching Excellence
Of the eight PIRCH faculty, four (Herman, Hornberger, Mills, and Ford) are established researchers at the University of Virginia. They have been honored with recognition of their contributions in scientific research: Herman by election to Fellowship in the Geological Society of America; Hornberger by appointment to the Ernest H. Ern Chair of Environmental Sciences, receipt of the Horton Award, and election as Fellow of the American Geophysical Union, to name a few; Mills by election to Fellowship in the American Academy of Microbiology; and Ford through the Department of Energy's Young Faculty Award in its Environmental Restoration and Waste Management Program and through DuPont's Young Faculty Grant. Hornberger's career-long scientific leadership and wisdom have been recognized recently in his election to the National Academy of Engineering. The other four faculty (Raffensperger, Culver, Smith, and Fernandez) are younger, and they are already compiling impressive accomplishments of their own. Raffensperger won a year-long appointment as a University Teaching Technology Initiative Fellow; Culver and Fernandez each won a National Science Foundation CAREER Award; and Smith and Culver have been named Lilly Teaching Fellows at the University of Virginia.
The PIRCH faculty have made great strides as a group of colleagues interacting in research and teaching. Their combined record in research productivity over the past six years is outstanding: approximately $8,300,000 in extramural research funding and more than 150 refereed journal publications. They have also brought in more than $793,000 in external funds for student fellowships. Of particular importance to the integrated, interdisciplinary efforts of the PIRCH faculty are the NSF-sponsored Graduate Research Traineeships in Quantitative Contaminant Hydrogeology (5 years, $555,000; P.I.'s Herman and Ford), the award to the PIRCH program of $322,000 by the University of Virginia's Board of Visitors through their Academic Enhancement Program, and an award by IBM through their Environmental Research Program to study in situ bioremediation ($1,454,327 for 5 years, P.I. Ford).
The combined record of these eight faculty members in the training of students is excellent. Over the period 1990 to 1995, the PIRCH faculty have graduated 28 M.S. (including 14 women, or 50%) and 7 Ph.D. (including 2 women) students. Our advanced-degree students have gone on to academic positions (or further graduate study in the case of M.S. students), industry, and government laboratories. Further, the PIRCH faculty have supervised 52 undergraduates in research projects for senior theses. Collectively, the PIRCH faculty presently advise a large number of academically outstanding students: 26 undergraduates (65% of which are women), 25 M.S. students (60% of which are women), and 23 Ph.D. students (43% of which are women). The quality of our students is first-rate; for instance, our ten NSF PIRCH Graduate Research Trainees have an average GPA of 3.62/4.0 and average GRE scores of verbal 603, quantitative 716, and analytical 704, each out of 800. The PIRCH faculty have supervised nine postdoctoral associates in the period 1993-1996. Our commitment to interdisciplinary training gives our students broad experience in coursework and in research. The PIRCH faculty have already materially influenced the pool of young professional scientists working in quantitative contaminant hydrogeology by training undergraduate, graduate, and postdoctoral students.
We believe this setting is ideal for a Camille and Henry Dreyfus Postdoctoral Fellow. Our existing PIRCH program provides a rich context of coursework in Environmental Sciences, Civil Engineering, and Chemical Engineering; in-house seminars by faculty and students; visiting seminar speakers from other universities, industry, federal agencies, and national laboratories; an annual research retreat; and a variety of research activities and projects. A postdoctoral fellow could chose to participate in any aspect of our ongoing activities, including some teaching and supervision of students. We know from experience that postdoctoral associates attempting to become more broadly experienced in interdisciplinary knowledge, research experience, and teaching can benefit greatly from time spent at the University of Virginia.
A.4. Justification for Postdoctoral Fellowship
As with all universities, the quality of the faculty determine the excellence of the institution. In emerging areas of critical national need such as contaminant hydrogeology, there are very few universities in the country that can claim the quality of faculty that the University of Virginia can. And, importantly for the postdoctoral fellow, we are a group of friendly colleagues engaged in ongoing interdisciplinary research and teaching that would welcome the opportunity to bring in a postdoctoral associate. This person would gain research experience as well as significant interaction with graduate and undergraduate students at a first-rate academic institution. We believe this experience would prepare the postdoctoral fellow for his or her own successful career at university.
A.7. Description of Research Projects
We have several ongoing, collaborative, interdisciplinary research projects that involve PIRCH faculty and undergraduate and graduate students. We selected for brief description here several projects that offer great potential for interdisciplinary research in environmental sciences. The postdoctoral fellow could be engaged in a variety of approaches and scales of investigations: laboratory- or field-based research, experimentation, and modeling.
We expect to recruit the best possible postdoctoral fellow by giving several options for research projects rather than narrowly prescribing what the fellow would pursue here. Further, many of the postdoctoral fellow's research expenses would be supported by one of our existing grants. The stipend from the Dreyfus Foundation would support the postdoctoral fellow's salary and some basic expenses while funded research programs of the PIRCH faculty would support needed equipment, supplies, travel, and other expenses.
A.5.a. Colloid-facilitated transport of contaminant agrochemicals
This project is taking an integrated approach in evaluating the important controls on the fate of a widely used herbicide - atrazine - from initial occurrence in the unsaturated soil zone in an agricultural area to ultimate occurrence in the groundwater of a bedrock water-supply aquifer. We must expand our understanding of herbicide movement throughout the entire soil-bedrock system in an agricultural watershed in order to support intelligent management decisions about land use and its impact on sustainable water supply. Our interest in watershed-scale transport requires consideration of a number of processes occurring at different scales of time and space. We are working to develop a conceptual model of atrazine transport through a watershed by taking the approach of considering geochemical, hydrological, and microbiological processes and their rates in different settings in the subsurface environment. We are investigating processes such as transport through preferential flow paths in heterogeneous soils and bedrock; sorption, potentially with hysteresis, to mineral surfaces and particulate organic matter in the soil and bedrock immobile matrix; sorption to inorganic and organic mobile colloids that facilitate transport; and biodegradation of herbicide solutes and of bound residues in the unsaturated soil and in the water-saturated deep soil and bedrock. The relative importance of individual processes influencing the fate of atrazine will emerge through comparisons of their time constants.
Limestone valleys underlie extensive areas of agricultural land throughout the humid eastern U.S., and one such watershed, the site of a U. S. Geological Survey National Water Quality Assessment study, is the focus of our current research. At the Muddy Creek site in Rockingham County, Virginia, the fate of atrazine in the subsurface will be determined by the relative rates of several hydrological, geochemical, and microbiological processes, some of which have not been adequately considered previously. The time scale of water flow through unsaturated and saturated heterogeneous soils sets the temporal framework for the extent to which adsorption, desorption, and biodegradation may mediate the migration of atrazine in the subsurface. Observations of water flux and atrazine and colloid concentrations in the field over a range of rainfall conditions will establish the conditions of intact soil column experiments in the laboratory. Independent experiments on atrazine adsorption and desorption kinetics to the soil matrix and to mobile colloids, on formation of bound residues, and on biodegradation of dissolved and bound atrazine will establish the time constants of those processes. The role of colloid-facilitated transport will be explicitly evaluated, addressing an important gap in the literature. The rate of hydrological transport will be evaluated against the rates of geochemical and microbiological reactions in order to elucidate the critical mechanisms influencing atrazine biogeochemistry. We anticipate that the time scales of the transport, sorption, and degradation reactions change with changing conditions of the hydrological, geochemical, and ecological milieu. Even in this rather typical watershed, the environmental setting is likely to be distinctly different in (1) the unsaturated, biologically active shallow soil, (2) the water-saturated, deeply weathered, clay-rich residuum, and (3) the groundwater in a fractured, karstic limestone bedrock. With the proposed research we will attempt to clarify our holistic understanding of the processes that dominate and at what time scales they are important in controlling the fate of atrazine in groundwater of an agricultural watershed.
A.5.b. Role of bacterial transport in remediation of contaminated soil
In situ bioremediation relies on the ability of bacterial populations to biologically transform chemical contaminants such as chlorinated hydrocarbons into less toxic substances. A critical factor in successfully implementing this technology is assuring sufficient contact between the bacteria and contaminant to allow degradation to proceed. Therefore, mathematical models capable of predicting the dynamic distribution of bacterial populations within contaminated aquifers are necessary for determining the changing contaminant levels due to bacterial degradation. The development of a mathematical model with predictive capability will allow us to simulate and evaluate different treatment strategies at a relatively low cost prior to their implementation. For example, we may wish to compare treatments involving biostimulation and bioaugmentation for a particular contaminated site. Biostimulation requires the addition of nutrients to stimulate the activity of indigenous bacterial populations. Optimizing the location and frequency of nutrient addition is critical for an effective clean-up. Bacteria may preferentially locate near the nutrient source where they would reproduce rapidly and fill the pore space, thereby preventing nutrient delivery to the highly contaminated areas. Bioaugmentation requires the addition of genetically engineered or laboratory-adapted organisms to the contaminated site. In this case, it is critical for the bacteria to move away from the injection wells and toward the source of the contaminant. On a microscopic level, undissolved organic contaminants are often trapped in the interstices of the porous matrix or associated with the surfaces of the soil particles. Contaminants such as these are typically the most difficult to remove. Bacterial motility may impact the residence time of bacteria near high concentrations of trapped contaminant and the length of time that bacteria associate with surfaces. A quantitative understanding of the role that motility plays in bacterial transport may suggest ways to exploit it for technological advantage in cleaning up the most persistent and difficult contamination situations.
Until recently, approaches to modeling bacterial transport in subsurface environments have drawn heavily on analogies to solute transport that regard the bacteria as nonmotile colloids. Our approach is to apply our understanding of bacterial swimming behavior at the microscopic level and relate properties such as speed, run length, and turn-angle distribution to macroscopic-level coefficients analogous to diffusion coefficients which are need to predict dispersion coefficients required as input for advection-dispersion models. A combination of mathematical modeling, laboratory-scale experiments, and computer simulation will be used as research tools. The tracking microscope, stop-flow diffusion chamber assay, and cellular dynamics algorithms, capabilities unique to the PIRCH faculty's state-of-the-art experimental and computational laboratories, provide an ideal environment for the proposed development of mechanistic-based models for predicting large-scale migration. Our efforts are directed toward quantifying bacterial motility in order to assess its impact on engineering parameters used in advection-dispersion models for bacterial transport.
We also are extending our laboratory and modeling work to include experimentation at the field scale in a DOE-sponsored project. Although the reductionist approach of eliciting mechanisms using ideal laboratory studies is critical for identifying the structure of models, a phenomenological approach is also needed to develop models that can be useful under field conditions. The form of the bacterial transport models identified from laboratory studies certainly serves as a useful starting point for describing field situations. Questions of whether "effective" parameter values used in these models will succeed in the field need to be answered. The response of bacterial transport to departures from ideality must be explored in the field so that the potential for bacterial migration in geological formations can be estimated. Our work on field experimentation at a site on the Eastern Shore of Virginia seeks to provide this information.
A.5.c. Remediation of TCE-contaminated groundwater
The PIRCH faculty at the University of Virginia are working to develop innovative, cost-effective technologies to remediate groundwater contaminated by hazardous organic compounds. At present, efforts are being focused on remediation efforts at the Defense General Supply Center (DGSC) in Chesterfield County, Virginia. Groundwater at the site has been contaminated by the improper disposal of bulk drummed chemicals in an unlined, open storage area from 1942-1982. As a result of this practice, chlorinated solvent plumes have developed in the shallow, unconfined aquifer and in the deeper, confined aquifer. The primary contaminant in these plumes is trichloroethene (TCE). A conventional groundwater pump-and-treat remediation system is currently under construction and is scheduled to begin operation within the next 12 months. In our work, we seek to investigate the utility of injection of a nonionic surfactant, oxygen, and methane into the aquifer.
Under aerobic conditions, TCE can be biodegraded by a cometabolic process. Cometabolic biotransformation of TCE typically involves biostimulation of a mixed population of methane-oxidizing bacteria to produce an enzyme capable of oxidation of chlorinated ethenes like TCE. Although TCE can be biodegraded relatively quickly in groundwater containing oxygen and methane, this technology will not necessarily remediate an aquifer on a short time scale because of the presence of TCE that is sorbed to the saturated-zone soil. Because TCE that is sorbed to soil is not believed to be bioavailable, the slow desorption of TCE from soil to groundwater can be a limiting factor determining the time required to bioremediate an aquifer. The sorption of nonionic organic compounds to natural soil is believed to be caused by solute partition between water and the soil organic matter in accord with the solute's solubility in the two phases. Several researchers have proposed the use of surface-active agents (surfactants) to increase the rate of nonionic solute desorption from soil to water in contaminated aquifers. In this regard, the use of surfactants shows promise, in conjunction with pump-and-treat systems, for the remediation of contaminated aquifers.
We propose to study this process first in the laboratory using long-term contaminated soil samples from DGSC and then in a pilot-scale field experiment at the site. In the laboratory, we will first identify surfactants that have beneficial effects of pollutant desorption without having an adverse effect on the methanotrophic bacteria. Using batch and column experiments with sterile and nonsterile controls and computer simulations of the experimental data, we will separate the effects of the surfactant on the rates of desorption and the effects of the oxygen and methane on the biodegradation rates. Sensitivity analyses of our calibrated model will allow us to make conclusions regarding the relative importance of the two processes (e.g., enhanced desorption and biodegradation). The model will also let us directly quantify the beneficial effects of surfactant, oxygen, and methane on remediation relative to natural conditions.
A.5.d. Viscous fingering
Recent research at the University of Virginia has begun to focus on the phenomenon known as "viscous fingering" as applied to chromatography. When one liquid passing through the porous medium of a chromatography column is followed by a second liquid that is of lower viscosity than the first liquid, flow instabilities along the liquid-liquid interface arise as the less-viscous liquid attempts to bypass the first liquid. These flow instabilities result in the appearance of "fingers" of the low-viscosity liquid encroaching into the high-viscosity liquid and cause tailing of chromatographic peaks. Several researchers have presented mathematical descriptions of viscous fingering, however, validation of these theories with experimental data has been problematic because of the difficulties associated with direct measurement of the size and distribution of the fingers. Invasive techniques often alter the liquid-liquid interface or do not provide enough resolution to verify mathematical models. PIRCH faculty in Chemical Engineering have developed state-of-the-art equipment to non-invasively measure time-varying viscous fingering in a three-dimensional porous medium using magnetic resonance imaging.
This research effort will focus on the role of heterogeneities of the porous media, such as pore-size distribution, permeability, and chemical composition, in the formation of viscous fingers for soil-water-trichloroethene systems. The existing magnetic resonance imaging system will be modified to accommodate soil cores having varying degrees of heterogeneities. These samples will include intact soil cores collected from one or more field sites. The soil samples will be characterized by quantification of particle-size distribution, pore-size distribution, surface area, and organic-carbon content. The effects of varying soil properties on finger formation will be identified. Results of these experiments are critical to the evaluation of appropriate models for the flow and transport of multiphase fluids.
B. Faculty Participants
JANET S. HERMAN, Director of PIRCH; Ph.D., Geochemistry, The Pennsylvania State University, 1982. Associate Professor of Environmental Sciences, University of Virginia, 1988 - present. Elected Fellow of the Geological Society of America, 1994. Chairperson, Frontiers in Aqueous Geochemistry Symposium, Goldschmidt Conference, 1990; Convener, Special Session on Particle Transport in the Subsurface and its Geochemical Impact, Spring Meeting, American Geophysical Union, 1990; Associate Editor, Applied Geochemistry, 1992 - present; Associate Editor, Geological Society of America Bulletin, 1993 - present; Program Committee, Symposium on "Breakthroughs in Karst Geomicrobiology and Redox Geochemistry", 1994; Co-principal Investigator, Environmental Geochemistry Research Initiative, Geosciences Directorate, National Science Foundation, 1994 - 1995; Panelist, National Sciences Foundation, Earth Sciences Division, Research Experience for Undergraduates - Sites, 1994; Meinzer Award Committee, Hydrogeology Division, Geological Society of America, 1995 - present.
Three Recent Publications (of 40 total):
Mills A. L., Herman J. S., Hornberger G. M., and DeJesus T. H. 1995. Effect of solution ionic strength and iron coatings on minerals grains on the sorption of bacterial cells to quartz sand. Applied and Environmental Microbiology 60: 3300-3306.
Cozzarelli I.M., Herman J.S., and Baedecker M.J. 1995. Fate of microbial metabolites of hydrocarbons in a Coatal Plain aquifer: The role of electron acceptors. Environmental Science and Technology 29: 458-469.
Sacks L.A., Herman J.S., and Kauffman S.J. 1995. Controls on high sulfate concentrations in the Upper Floridan aquifer in southwest Florida. Water Resources Research 31: 2541-2551.
ROSEANNE M. FORD, Associate Director of PIRCH; Ph.D., Chemical and Biochemical Engineering, University of Pennsylvania, 1989. Associate Professor of Chemical Engineering, University of Virginia, 1994-present. Department of Energy, Environmental Restoration and Waste Management Program, Young Faculty Award, 1991-1993. American Institute of Chemical Engineers: Member since 1984, Session Co-Chair for Annual Meetings, 1992-1994; American Chemical Society: Member since 1989, Session Co-Chair for National Meeting, 1991; Sigma Xi: Member since 1991, University of Virginia Chapter President-Elect 1991-1992, President 1992-1993 and Member of the Executive Committee 1991-1994; Participating Faculty 1991-1996, Member of Executive Committee 1994-1997, Interdisciplinary Graduate Program in Biophysics; Panelist, National Science Foundation, Bioengineering Division, Research Initiation Awards and Equipment Grants, 1992; Panelist, National Science Foundation, Environmental Geochemistry and Biogeochemistry Grants, 1996; Invited Speaker, Gordon Research Conference, Theoretical Biology and Biomathematics, 1996 and Annual Meeting of Society for Industrial Microbiology, Boston, MA, 1994.
Three Recent Publications (of 19 total):
Frymier P.D., Ford R.M., Berg H.C., and Cummings P.T. 1995. Three-dimensional tracking of motile bacteria near a solid planar surface. Proceedings of the National Academy of Science, USA 92: 6195-6199.
Barton J.W. and Ford R.M. 1995. Determination of effective random motility coefficient for bacterial migration through sand cores. Applied and Environmental Microbiology 61: 3329-3335.
Strauss I., Frymier P.D., Hahn C.M., and Ford R. M. 1995. Analysis of bacterial migration: II. application to experimental studies of multiple chemical gradients. American Institute of Chemical Engineers Journal 41: 402-414.
Other participating faculty. Teresa Culver, Assistant Professor of Civil Engineering. Research interests in environmental systems analysis. More than six refereed journal publications. Funding includes NSF Career Research Award 1995-1999. Erik Fernandez, Assistant Professor of Chemical Engineering. Research interests in transport in porous media. More than ten journal articles. Funded research from NSF, Dupont, and ACS among others. George Hornberger, Ernest H. Ern Professor of Environmental Sciences. Research interests include transport of colloids through geological media. More than eighty journal articles. Funded research from NSF, EPA, and DOE. Aaron Mills, Professor of Environmental Sciences. Research interests include microbial processes in the subsurface. More than eighty journal articles. Funded research from DOE, NOAA, and EPA. Jeff Raffensperger, Assistant Professor of Environmental Sciences. Research interests in multicomponent reactive transport in groundwater. Nine journal articles. Funded research from Virginia Water Resources Center and ACS. James Smith, Assistant Professor of Civil Engineering. Research interests include bioremediation of contaminated aquifers. More than fifteen journal articles. Funded research from EPA, USGS, and Virginia Water Resources Center.