George Hornberger - US grants

A general synthesis of how patterns of constraint and system scaling vary among ecosystems within different environmental regimes will be developed through mathematical modeling. The search will be organized around three objectives: (1) To synthesize existing data from a spectrum of ecosystems as represented by various LTER sites, in particular, the gradient of sites across the North American continent that includes the deciduous forest on the east through the Konza LTER site in the tall.grass prairie to the Central Plains LTER site in the short.grass prairie. This work will focus on the role of key environmental drivers (insolation, temperature, moisture, nutrients, and disturbance regimes) in structuring specific ecosystems. (2) To implement an integrated set of computerized simulators which are sufficiently general that they may be applied across this gradient. (3) To test model.generated hypotheses and predictions against independent data representing ecosystems that were not involved in the model development. The ecosystem.level phenomena of interest in this research imply spatial scales as typically connoted by the term"landscape" or larger, and decadal to centennial time scales. The emphasis on transitions between ecosystem types implies anextension to spatial scales that are at least regional, andultimately continental, in extent. Four models, which are already developed and well documented, will serve as the starting point for this research: (1) the CENTURY model of carbon and nutrient dynamics; (2) the MAGIC model of soil and water chemistry; (3) the FORET model of forest dynamics; and (4) the STEPPE model of succession in semiarid grasslands. A principal task in the research will be the development of appropriate interfaces between these models in the context of simulating the pattern in the continental scale gradient. The significance of this research is that it will help us to develop a modeling base in support of comparative ecosystem analysis among sites in the LTER network and the development of ecosystem theory. The research will also address the issue of how measurements made at small scales in space and time can be extrapolated. Both the development of theory and an understanding of issues of scale are essential to the development of sustainable management regimes for the Earth's ecosystems. Drs. Shugart, and Lauenroth are leaders in the field of ecological modeling. The institutional support available to them is superior.

This research will continue and extend the analysis of the relationship between vegetation pattern (species or lifeform composition, size structure) and ecosystem processes (nutrient cycling and water relations). This project has as its nucleus a set of interacting models that couple ecosystem processes to vegetation dynamics through growth, mortality, and regeneration of individual plants. The models will be implemented and tested at several sites, each a member of NSF's Long-Term Ecological Research (LTER) network, which represent a range of forests and grasslands arrayed along continental-scale temperature and precipitation gradients. Analyses will focus on two goals that are fundamental to ecosystem science and developing global environmental concerns: (1) to account for existing patterns in vegetation and ecosystem processes under current environmental regimes; and (2) to assess the potential responses of ecosystems to environmental variability, especially anthropogenic climate change. This project will contribute substantially to ecosystem science by further elucidating the "pattern-process" paradigm as applied to feedbacks among plant-demographic mechanisms, water relations, and nutrient cycling; and by providing a synthesis of these relationships over a broad spectrum of ecosystems but within a common framework. The project will also further develop networking capabilities among collaborating scientists.

Fundamental and applied problems associated with the contamination of the subsurface environment are receiving attention at local, national, and international levels. Groundwater contamination is clearly an urgent technical issue in our society. The University of Virginia has taken an interdisciplinary approach to the study of quantitative contaminant hydrogeology that places it in a unique position of national prominence in the field. With additional support for graduate students, the ongoing research and teaching program should allow them to craft a cohesive program that will provide the basis for understanding the fundamental technical issues of groundwater contamination and produce competent professionals who can address the details of this complex interdisciplinary problem from a variety of perspectives. Collaboration across departments is generating new research funds, additional faculty members, and new space; the University of Virginia is primed to expand its role in the training of critically needed technical professionals. This interdisciplinary academic program, encompassing hydrogeology, geochemistry, microbial ecology, chemical engineering, and civil engineering, shall evolve into a national resource by producing outstanding graduates to fill positions at other universities, national research facilities, federal agencies, and industry, and to train them to contribute to solving our Nation's problems in contaminant hydrogeology.

A quantitative understanding of the hydrochemical response of upland catchments is a fundamental goal of hydrologists and environmental chemists. Such knowledge is needed to ascertain the potential and realized effects, for example, of atmospheric deposition of acids and agricultural chemicals on the catchment (terrestrial and aquatic) ecosystems, of changes of climate on water quality, and of the role of hydrology in the transport of heavy metals and other trace contaminants. In particular, an improved understanding of the factors controlling the variation of dissolved organic carbon (DOC) in headwater streams is of scientific concern for at least two reasons. First, the overall carbon budget of lotic systems is of primary interest to aquatic ecologists seeking a fundamental scientific understanding of these systems. Second, DOC interacts strongly with other dissolved substances (heavy metals in particular) and therefore plays an important role in the transport of contaminants in streams. Heterogeneities in the amount of precipitation delivered to the surface of a catchment, in soil properties and vegetation coverage, and in incident solar radiation can pay an important role in the hydrological response of mountainous catchments. These heterogeneities may be particularly important in influencing how chemicals (e.g., DOC) are delivered from the terrestrial catchment to the stream. Complete characterization of heterogeneities over a catchment is essentially impossible, but is likely to be unnecessary for descriptions of hydrochemical dynamics at the scale of a whole catchment. A possibly fruitful hypothesis is that the heterogeneities that dominate the catchment response are relatively large scale and hence can be identified from readily available data--topography, aerial photography, and satellite imagery -- in conjunction with a modest data-collection program in the field. The proposed work will explore this idea. The effects of spatial patterns in topography, vegetation cover, snow accumulation and melt, and soil transmissivity on the hydrochemical response of the Snake River in Summit County, Colorado will be determined. Spatial data will be analyzed using techniques embodied within geographic information systems (GIS) and synthesized in the context of a hydrological model (TOPMODEL) that will be modified to take into account the identified landscape-scale heterogeneities. Field data on precipitation, flow, hydraulic conductivity, and dissolved constituents (sulfate and DOC, in particular) will be used to evaluate the working hypothesis of the links between large-scale heterogeneity, hydrology, and hydrochemical response.

9628368 Hornberger In many catchment-stream systems, the concentration and composition of dissolved organic material (DOM) is a critical water quality characteristic. Examples of processes controlled by DOM interactions are: 1) complexation of trace metals by the humic fractions of DOM which control both trace metal transport and bioavailibility; 2) enhancement of the solubility of hydrophobic organic contaminants; 3) formation of trihalomethanes in drinking water as a result of interactions between Chlorine and components of the DOM during water treatment; and 4) absorption of visible and UV radiation by DOM and generation of photoproducts. The DOM also can have indirect effects on water quality by influencing internal processes of aquatic ecosystems, e.g., photosynthesis and heterotrophic activity. In this proposal, we advance a plan of study to investigate in-stream processes and their interaction with catchment processes in determining the spatial and temporal patterns of quantity and quality of DOC in streams in the Rocky Mountains. The research tasks will include experimental additions of DOC-enriched water to stream segments to quantify interactions in the hyporheic zone, field monitoring to deermine synoptic spatial patterns along stream channels and in hillslope lysimeters of amounts and composition of DOC, and the extension of mathematical models to interpret the results. Studies of the in-stream processes will include continuing assessment of the roles of near-stream and catchment-scale processes.

Catchment structure, both surface topography and subsurface permeability, is an important determinant of catchment response to precipitation events. Stream water chemistry is in turn influenced by time-varying flow paths that characterize hydrological response. Although much progress has been made in recent years in understanding the flow paths and how chemical composition of waters reflect these paths, the impact of different simplifying assumptions underlying current models have not been explored systematically. In particular, the dynamics of a subsurface stormflow zone above a regional water table have not been addressed fully even though water in the vadose zone plays a major role in determining stream water chemistry. An explicit accounting of soil moisture must be part of an adequate quantification of catchment hydrochemical response. The goal of the study is to develop a quantitative and predictive physically-based model of the hydrological response of a saprolite-granite catchment and to explore the importance of surface topography and subsurface structure in determining catchment hydrochemical response.

Ford
0083839

The release of chemical pollutants into groundwater disturbs the resident microbial community and triggers a complex network of feedback loops affecting the groundwater geochemistry, soil structure and microbial diversity of the system. Human intervention in the form of engineered remediation to restore the site introduces yet another disturbance to which the microbial community and abiotic components of the systems must respond. An emergent property typically associated with microbial communities is homeostasis. The objective of this research is to test the homeostasis hypothesis for a subsurface microbial community under the stress of a chemical pollutant release and the remedial actions which may follow.

To accomplish this objective will require effective collaboration among a team of scientists and engineers with expertise in microbiology, hydrology, biogeochemistry, engineering, ecological modeling, adaptive control theory, and data visualization. Incubator activities are designed to foster communications between experimentalists with an understanding of the physical system and mathematical modelers with quantitative tools for characterizing and predicting properties of the system. A relatively simple laboratory experiment [two bacterial species within a fixed-film flow-through column with a reactive mineral surface (iron) that serves as an alternative election acceptor in the absence of oxygen] is defined in order to explore three modeling approaches: (1) system of nonlinear partial differential equations for each species, (2) metabolic modeling, and (3) adaptive control theory. This prototype system will be used to focus the interdisciplinary discussions on a concrete problem and facilitate productive interactions. Additional modeling approaches will be explored through a brainstorming session, computer systems and a follow-up videoconference. A written summary from the workshop will be published in technical news journals to benefit the scientific community at large.

9909491
Herman

Colloids, mobilized within the vadose zone during rainfall events, scavenge and carry contaminants to underlying groundwater. Despite the importance of colloids as agents of vadose-zone contaminant transport, the factors influencing colloid movement through partially saturated porous media have not been rigorously explored nor formalized into a quantitative model. In particular, the role of flow transients on colloid interactions at solid-water interfaces, at air-water interfaces, and within thin films of water has not been adequately investigated to date. This research, carried out jointly by investigators at Yale and at UVA, will integrate laboratory-scale and field-scale experiments with mathematical modeling. We will measure colloid transport in laboratory experiments conducted with ideal media and with intact cores, and we will use these data to guide the development of a numerical model for the coupled advective-dispersive transport and mass transfer of colloids in unsaturated soils. The structure of the numerical model identified from analysis of the laboratory-scale experiments will form the foundation for a stochastic streamtube model, a model capable of accounting for the effects of spatial variability in soil properties on colloid fate and transport. The streamtube model will be tested against data from a field experiment in which colloid mobilization and transport is measured in response to transient flow events induced by controlled sprinkling over an instrumented field plot. Our work represents the first systematic approach to identifying the controls on colloid movement in water-unsaturated media under transient-flow conditions and provides a means to evaluate the contribution of the colloid track to contaminant fluxes within vadose-zone environments.

0208386
Mills
In field studies of groundwater in a range of hydrogeological settings, the rates of microbially mediated geochemical reactions have been shown to be far faster than hydrological transport rates. These relative rates lead to large changes in concentration of a variety of redox-sensitive chemical species over short distances within aquifers. In some systems, however, transient hydrological events (e.g., heavy precipitation on dry soil or floods in streams) can rapidly alter the geochemical environment in which the microbes exist. In that circumstance, the time constants associated with the physical events approach those of the microbially mediated processes. The proposed research addresses the question: How do hydrological processes and biogeochemical processes interact in the riparian-hyporheic zone of streams where time scales of the various processes are on the same order - hours to weeks? The proposed research will examine the effect of bank-storage events on reductive microbiological processes occurring in the riparian-hyporheic zone of a low-relief coastal plain stream. In particular, the concentration of nitrate-N in the groundwater feeding the stream is about 15 mg/liter, but the stream-water concentrations average only 1.6 mg/liter, suggesting high denitrification activity in the riparian- hyporheic zone. We envision the disruption of anaerobic processes during rain events in which rapid infiltration raises the water table and "flushes" chemicals (viz., nitrate) in the pore water out into the stream and perfuses the area with oxygenated water. We expect a similar disruption without flushing during storms in which a rapid rise in stream level pushes oxygenated water into the stream banks, thereby transiently extending the hyporheic zone. We will also examine the effect of flushing or bank-storage events on the denitrification and will document the rate of return of the functional abilities of the microbial communities to the pre-disturbance levels. Because these transient events have the potential to affect release of chemicals like nitrate from the groundwater into the surrounding surface waters, we will investigate how transient conditions in riparian soils affect the overall budget of biologically active chemicals. The proposed work includes detailed field observations, field manipulation experiments, laboratory batch and "mesocosm" experiments and mathematical modeling. We anticipate that we will learn how microbially mediated geochemical reactions and transient hydrological processes with time scales on the same order are linked. We will develop quantitative descriptions of these processes and investigate how frequently biogeochemical processes are "reset" by different hydrological events the synoptic data that we will examine how the transient effects of local processes influence regional nutrient fluxes.

DESCRIPTION (provided by applicant): The long-term objective of this application is to enhance the biomedical research capabilities in molecular and cellular biology in the Department of Biology and the UVA. Specific aims are to renovate on the ground floor of Gilmer Hall to provide the following: 1) three modern molecular and cellular biology research laboratories; 2) support areas and conference rooms for use of these and other cell and molecular biology laboratories; and 3) research and support space to consolidate at one site the currently dispersed personnel and equipment of an existing research laboratory. Morphogenesis was identified in an internal and external review of the Department of Biology as the major initiative for emphasis. The Biology Department is strong in developmental genetics, developmental biology, and imaging technology, especially in light of complementing strengths in the School of Medicine nearby, and morphogenesis is an area of exciting progress with the advent of the genome projects, development of new imaging and biophysical methods, and new possibilities for medical applications in stem cell research. To enhance existing strengths and take advantage of these new developments, the Department of Biology must strengthen its cell biological approaches to morphogenesis, specifically in such areas as the cytoskeleton, molecular motors, cell adhesion, cell polarity, transport and localization of RNA and proteins, cell adhesion, and cell migration. The proposed renovations will include new laboratory space for two new research faculties in these areas and provide support areas for these and existing laboratories throughout Gilmer Hall, thus enhancing biomedical research programs in Biology and elsewhere at the University.

Proposal ID: 0450264
PI/Institute: Hornberger/University of Virginia

Collaborative Proposal: Hydrologic Regulation of Dissolved Organic Matter Biogeochemistry from Forests through River Networks

Louis A. Kaplan, Anthony K., Aufdenkampe, Charles L. Dow, J. Denis Newbold, and George M. Hornberger


Each year, massive amounts of organic carbon, in the form of dissolved molecules, are transported to the oceans of the world by rivers. The source of most of that carbon is the upper layer of soils within small watersheds, and the movement of water through soils controls organic carbon delivery from the landscape to streams. Standing on the streambank, the investigators look both upslope and downstream, focusing on the interactions of water movement and organic carbon supply, investigating processes within the hillslope soils, individual stream reaches, and the entire river network. This proposal will integrate dynamic mathematical models that describe organic carbon movement, transformation, quantity and quality in terrestrial and aquatic environments and will generate the first model that links the water cycle and the carbon cycle of river catchments.

The research will have important outcomes for the management of drinking water resources, where watersheds are recognized as the first stage of treatment. Additionally, an increased understanding of the dynamics of organic molecules in water will provide valuable information about the fate and transport of potentially harmful anthropogenic compounds that stick to and are transported with those naturally occurring molecules. Lastly, in developing an understanding of the cumulative role of small streams in the carbon cycle of large rivers, the researchers will contribute information concerning the value of headwater streams to society.

Nitrous oxide is released into the atmosphere from a variety of human activities. This gas is roughly 300 times as potent as carbon dioxide in trapping heat in the Earth?s atmosphere, and thus even small quantities of emissions may constitute a meaningful share of US greenhouse gas emissions. One path for nitrous oxide releases is from the application of fertilizers to lawns because a portion of these fertilizers is converted to nitrous oxide by soil bacteria. Not only are the physical factors that affect nitrous oxide emissions from households not well quantified, but social science research and research into climate change mitigation laws and policies associated with lawncare has not been a focus in the past. An integrated, interdisciplinary study is needed to answer questions related to (1) the physical processes that lead to nitrous oxide emissions from household nitrogen-containing fertilizer use, (2) the types and levels of individual and household activities that affect household nitrous oxide emissions from fertilizer use; (3) the values, beliefs and norms associated with these individual and household activities; and (4) the communities and social networks associated with these activities. This project is a study of the Richland Creek Watershed, which encompasses 28.5 square miles of primarily residential neighborhoods in Nashville, Tennessee. These neighborhoods represent a diverse range of residents in terms of race, income, education, and ownership patterns. A coordinated set of biophysical and social-science data will be collected and analyzed to address the science questions. To understand how social and economic influences affect fertilizer use in Richland Creek neighborhoods, the research team will conduct a series of surveys with 600 households grouped in 60 blocks in the watershed. We also will conduct 60 focus groups, one for each sampled block. To provide the link to the release of nitrous oxide, physical samples will be taken at locations around the watershed. Nitrous oxide fluxes from the soil will be measured using soil covers and soil moisture and temperature will be measured at the sampling sites using a wireless sensor array.

Using data derived in this research, theoretical explanations of household, sub-neighborhood, and neighborhood behaviors and their effect upon fertilization rates will be tested and, through links with measured biophysical processes, emission rates of a powerful greenhouse gas, nitrous oxide, will be included. The project will lead to knowledge of how much of nitrogen-containing fertilizer applied to lawns is converted to nitrous oxide as affected by soil and meteorological conditions; how household lawncare decisions around fertilizer use are affected by a neighborhoods? norms and characteristics; which household-level beliefs, norms, and characteristics affect fertilizer use; how neighborhood-level norms and characteristics interact with household characteristics; and how the combined knowledge of emissions and behavioral characteristics can be used to explore options to effect reductions of nitrous oxide emissions from fertilizer use. In particular, the research results may indicate that a number of policy or community-level interventions may be appropriate for reducing the household share of greenhouse gas emissions and that these interventions may be quite cost effective in comparison with more often used regulatory measures targeting industrial sources.

Water scarcity is a growing concern in the U.S. and throughout the world, affecting an estimated one third of the population on every continent. The problem is particularly urgent in developing countries heavily reliant on agriculture, which can account for as much as 85-90% of fresh water usage. Effective water resource management has significant implications for food security, health, and worldwide political stability. This is increasingly important in the face of a growing population, dramatic shifts in land use, and changing climatic conditions. Historically, the world?s farmers have relied on traditional practices to manage water, but now find themselves challenged by new conditions that require adaptation to these farming practices. Understanding the complex array of factors?psychological, social, environmental, and political?that facilitate and constrain effective adaptation requires an integrated research agenda that transcends traditional disciplinary boundaries. This research draws upon the core disciplines of psychology, sociology, hydrology, and engineering in order to investigate these issues among paddy farmers within the Mahaweli River Watershed, Sri Lanka?a largely agricultural region that is a microcosm of the sort of massive changes occurring throughout the world in environmental, institutional, and social systems. These changes include impacts of drought as well as an ongoing national resettlement plan to populate and develop regions of the watershed. The research team will use a multi-level, multi-method approach that incorporates longitudinal farmer surveys, regional level drought indices (coupled with short- and long-term drought forecast methods), key informant interviews, and archival analysis. The research team will investigate how farmers adapt to changing water availability and how these decisions are affected by psychological, social, institutional, and environmental factors. The team will examine water availability and rice yields in light of farmers? adaptive actions, changing rainfall and temperature patterns, land use changes, and water allocation decisions. These multiple streams of data will be integrated using agent-based modeling to generate a rich set of future scenarios to characterize how changes to social and institutional circumstances and in the natural environment may affect farmers' adaptive actions and their effectiveness in managing vulnerability to water scarcity.

This project will not only advance our theoretical knowledge within and across disciplines; it will provide much needed practical information about sustainable water resource management to farmers and decision makers in a developing country where water scarcities have major implications for food security. A recent report from the U.S. National Intelligence Agency looking forward to the year 2040 concludes: ?Water problems will hinder the ability of key countries to produce food and generate energy, posing a risk to global food markets and hobbling economic growth.? This research is directed towards averting the worst of such consequences by furthering the knowledge of farmers, local community leaders, national governmental leaders, and researchers about strategies to reduce water stresses and facilitate adaptation. Additionally, the team has incorporated a major educational aspect in the project to train the next generation of scholars in a thoroughly interdisciplinary framework. As such, they will be mentored not only in theory and methodology but also in how to communicate research to diverse audiences, including policymakers and some of the world?s most vulnerable populations.

American cities recognize water supply as a central scientific, technological, and socioeconomic problem. In response to the public concern with the risks posed to water supplies, cities and related metropolitan water organizations have faced the need to undertake transitions in their systems of water supply and management. These transitions involve a mix of social, economic, political, and technological change. Of the various approaches to satisfying water demand, water conservation, as an essentially free new "source" of water, is typically the most cost effective. Water conservation also has significant indirect benefits, such as energy conservation and the reduction of stress on ecosystems. The goal of this research is to understand better why some cities have moved ahead to have extensive water conservation policies and some have not. The research also will investigate why cities with similar water shortage regimes respond differently to proposals to deepen and extend water conservation. An extensive data base on water availability, water use, and the conservation policies for major cities in the U.S. will be assembled and analyzed. Interviews with public officials involved in water conservation planning will provide context. The project will educate students across many disciplines and will produce results that will be useful in guiding water managers and political leaders on different water conservation strategies

Several major research questions will be addressed to understand how U.S. metropolitan areas have transitioned to advanced water conservation strategies to minimize impacts of water stress. What is the range of water conservation transitions in American cities? What social and hydroclimatological factors affect the pattern of water conservation transitions? The research project will test hypotheses developed from the existing literature on sustainability and related policies to determine the factors that affect the pace and depth of the transition toward a higher level of water conservation. A comprehensive data set for as many as 381 cities will be assembled and analyzed using statistical and data visualization methods. The project will develop the first systematic, interdisciplinary database of water conservation regimes in American cities. The research will develop detailed case studies of four cities using interviews of key public officials and will incorporate the information gained into mathematical models that include decision variables as well as physical constraints. These studies will explore the complex properties of the interactions of political power, user practices, infrastructure design, and hydroclimatology in achieving high levels of water conservation.

Urban water-supply systems consist of both physical infrastructure and policies that govern their use. These systems are designed to be adaptable to a wide range of supply and demand conditions. However, climatic and social shifts are placing new stresses on water-supply systems that require substantial changes, also called transitions, to maintain system performance. This research analyzes transitions across 12 large-scale urban water systems in the United States to achieve two goals: 1) to better document the interactions among various environmental and human factors that may prompt transition, and 2) to identify which infrastructure and policy design choices can foster practical transitions to increase sustainability. To accomplish these goals this project will gather and analyze long-term human and environmental data to synthesize relationships and trends, and develop two complementary models to identify pathways that can lead to a sustainable water-supply transition. This project will directly involve stakeholders in multiple stages of the research to both learn from their experiences and ensure that outputs meet their needs. This project also will provide education and training opportunities to help students develop the competencies needed to collaborate across fields, a skill that is essential to tackle current environmental challenges.

The proposed research utilizes a "convergence" approach to investigate how integrated urban water systems can be managed effectively as they face increasing pressures from climate change, population growth, and other environmental factors. This research will involve a longitudinal analysis of system stressors, an examination of hydrological detection and change, construction of a Bayesian model to forecast the probability of stressors exceeding thresholds for transition, and development of a dynamic model to identify promising design choices. This project will benefit urban water-supply systems in four ways by: 1) combining institutional analysis with dynamic modeling to gain new insights into the role of institutions in shaping system dynamics; 2) linking the detection and attribution of hydrological change to watershed and policy processes, which will result in new knowledge about the drivers and the impacts of hydrological change; 3) synthesizing quantitative and qualitative data, stakeholder knowledge, and inductive and deductive modeling approaches to enhance system performance; 4) identifying how specific infrastructure and institutional design choices affect system resilience and transition probability. Knowledge relating design to outcomes is key because, although cities cannot control the dynamics of hydrological or human systems, they can alter design choices. Examining urban water transitions can also offer general insights for other socio-environmental challenges where preemptive intervention will be beneficial.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.