Projects
TThe
Environmental and Water Studies Program encompasses both teaching
and research. The research program emphasizes several major areas of
activity and, as a general philosophy, promotes interdisciplinary projects.
Laboratory research is generally conducted within the Environmental
Fluid Mechanics Laboratory and the Water Quality Control
Laboratory. Often faculty, staff and students from several
specialty areas work as a team on a given research endeavor.
Student participation is a vital element; at any one time,
approximately forty graduate students, representing all
levels of degree candidacy, are contributing to one or another
of the approximately twenty-five funded research projects.
The size and diversity of the research program provide numerous
learning opportunities outside the classroom, and stimulate
a level of excitement for learning through research that
is rare. Student-faculty relations are relaxed and friendly.
Student initiative is encouraged in conceiving and conducting
research, as well as in communicating results. Current research
includes laboratory and field studies on the movement and
fate of organic and inorganic compounds in ground water
and surface waters; physical, chemical, and biological processes
and mechanisms responsible for the release, transport, transformation,
and retention of contaminants; contaminant control processes
(especially the removal of trace contaminants); mathematical
modeling of important processes as well as hydrologic phenomena;
stochastic modeling of spatial variability and uncertainty
in ground water flow and transport; the development of alternative
energy sources; fundamental principles of physical, chemical
and biological treatment technologies for water, waste water
and solid wastes. In the environmental fluid mechanics area
current research is focused on stratified flows in lakes,
reservoirs, natural and forced convection flows in energy
systems, and simulation of mesoscale
phenomena in the oceans and surface layers of the atmosphere.
Other research includes hydrologic modeling, interaction
between surface water and ground water, and a comprehensive
program on the fundamentals of fluid transport, including
turbulence and mixing in natural water bodies and the mechanism
of dispersion in porous media flows. In the environmental
planning and management area current research is focused
on implementation of environmental policies and programs
in developing countries and on the applications of expert
systems in operating water resources systems. The following
is a list of currently active externally funded research
projects:
Topic:
Environmental Fluid Mechanics
Hydrology and Water Resources
Transport and Fate of Contaminants
in the Atmosphere
Transport and Fate of Contaminants in
Groundwater
Contaminant Control Technology
Environmental Planning and Management
Environmental Microbiology
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Environmental
Fluid Mechanics
Hydrology
and Water Resources
The Water
Supply of the Bay Area during Prolonged Droughts - Kitanidis, P. K.
(UPS Foundation)
The economy of the Bay Area has been booming and new housing developments
can be found to the edges of the Central Valley. Is there sufficient water
to support the existing population and such development rates? The purpose
of this research is to study the sources, availability, and reliability
of water for the greater San Francisco Bay Area, with emphasis on drought
conditions. An additional objective is to evaluate the need for gradual
water rationing as a drought progresses. The project includes statistical
analysis of time series of major sources, demand projections, the study
of conservation and rationing policies, and the conjunctive use of groundwater
and surface water.
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Conditioning
Model Predictions on Data and Solution of Inverse Problems in Contaminant
Hydrogeology - Kitanidis, P. K.
It is difficult to predict pollutant concentration in geologic formations.
However, by making sensible use of data, one can improve the accuracy
of predictions of models of mass transport and chemical fate. In practice,
the available observations are not sufficient for predicting a unique
scenario, as in the deterministic approach. The probabilistic approach
aims to simulate an ensemble of scenarios that are consistent with the
physical laws that govern representations of the flow, transport, and
transformation, as well as the available observations. These predictions
are useful in risk analysis and management, such as selecting the most
cost-effective remediation scheme or sampling strategy. We develop and
test new methods for incorporating the information contained in observations
to: (a) Estimate hydrogeologic parameters that control rates of groundwater
flow and the transport and transformation of chemicals in the subsurface,
(b) Generate an ensemble of equally likely chemical concentrations consistent
with process understanding and observations.
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Management
of Stochastic Dynamic Systems with Emphasis on Reservoir Operation
- Kitanidis, P. K.
Even when existing water-resource systems are managed efficiently, it
is hard for trial-and-error heuristic management to keep up with changing
demands and management objectives. Mathematical modeling and optimization
could contribute to improved management, but existing procedures are limited
in their effectiveness and acceptance, partially because they do not account
properly for hydrologic and demand uncertainty. However, recent advances
in algorithms and increases in computer power have made some problems
tractable without resorting to inappropriate simplifying assumptions.
We have been working to develop and apply methods that allow treatment
of previously unsolvable optimization problems, including the conjunctive
management of groundwater and surface water systems. The algorithms we
have developed for multi-dimensional stochastic dynamic programming problems
are the fastest available.
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Transport
and Fate of Contaminants in the Atmosphere
Effects of Future Emissions
and a Changed Climate on Urban Air Quality - Jacobson, M.Z.
(EPA). This is project to study the effects of changes in emissions
on climate and the resulting feedback of climate change on air quality
in Los Angeles, the Central Valley, and Atlanta during the next 50
years. We will examine the effects of emission changes resulting
from standard IPCC-SRES future emission scenarios. We will also examine
the effects of emission changes due to implementing a future fleet
of ethanol-gasoline, plug-in gasoline-electric hybrids, and wind-electrolysis-hydrogen-fuel-cell
vehicles. Finally, we will look at the future contribution of Asian
emissions to U.S. pollution. The study will involve model simulations
of climate and air quality with GATOR-GCMOM, which nests size-resolved
aerosols, gases, and meteorological variables together from the global
to urban scale. This model is unique because it allows the continuous
inflow of gas and aerosol information from the global to finer scales
(rather than running a separate global model offline to produce meteorology
a regional nested model) and treats physical processes and gridding
consistently on all scales. The model resolves transports (horizontally
and vertically) clouds and precipitation and forms them physically
from aerosol particles on nonglobal nested grids. The model will
first be used with 50-year A1B and B1 emission factors applied to
the 2005 U.S. National Emission Inventory. Three additional future
inventories, one with E85 (85% ethanol-15% gasoline) vehicles, one
with plug-in hybrid vehicles, and one with wind-hydrogen fuel cell
vehicles substituted for gasoline vehicles, will also be prepared.
Simulations will be run for 50 years, with nesting in Los Angeles,
the Central Valley, and Atlanta in years 1 and 50. First-year results
will be evaluated against data. This study will estimate the effects
of future emission scenarios on climate and the resulting climate
effects on U.S. air quality. While overall U.S. air quality is expected
to improve due to lower emissions, global warming may reduce this
benefit. The purpose of this project is to quantify the net effect
of global warming on air pollution. The study will also analyze a
future fleet of E85 vehicles on 3-D air pollution. Of interest is
determination of whether such vehicles will increase or decrease
ozone and PAN in different parts of the U.S. and how global warming
may affect their emission. Higher future emissions from Asia are hypothesized
to increase urban air quality problems in California and the west.
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Studying the effects of aircraft
exhaust on global and regional climate - Jacobson, M.Z. and S.K. Lele (FAA)
This is a project to quantify the effects of aircraft exhaust and contrails
on global and U.S. climate and atmospheric composition by combining
aircraft emission data with nested global-through-regional climate
modeling. The nested model to be used will be GATOR-GCMOM (gas, aerosol,
transport, radiation, general-circulation, mesoscale, and ocean model).
Subgrid-scale information about contrails will be obtained from Large-Eddy
Simulation (LES) modeling. Three issues to be examined over the long
term are the effects of aircraft exhaust on contrails and their feedback
to climate, gas-phase aircraft exhaust on tropospheric/stratospheric
chemical composition, and the effect of soot aerosol emissions from
aircraft on climate. The rigorous completion of all three of these
tasks will take at least three years; however, in the first year, for
which funding is requested here, we propose to provide a preliminary
quantification of the spatially-distributed effects of aircraft contrails
on global climate and, at higher resolution, U.S. regional climate.
On both scales, we will provide domain (global and regional)-averaged
and spatially-varying statistics and maps of, for example, near-surface
temperature changes, surface and top-of-the-atmosphere irradiance changes,
and cloud fraction changes due to contrails. Such information will
attempt to address the question of the extent to which regional effects
of contrails are much more significant than seen in the global average.
We will evaluate the model against data to the extent possible, although
evaluation is unlikely to be complete within one year. If the project
is funded past the first year, the study will extend and improve the
LES modeling, examine the effects of contrails at higher resolution
and over a longer period over the U.S. with the improved LES results,
and address the questions of the effects of aircraft on tropospheric/stratospheric
composition and atmospheric heating through soot emissions.
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Indoor Air Pollution and Health
in Developing Countries: An Intervention Study in Bangladesh– N.G. Miller and L.M. Hildemann (Environmental Venture Fund, Woods
Institute for the Environment)
Half the world's population relies on dung, brush and wood as their
primary source of energy for cooking and heating, and biomass combustion
indoors is viewed as a major contributor to indoor air pollution in
developing countries. Indoor air pollution has been shown to be associated
with acute respiratory infections -- in fact, the World Health Organization
has attributed 5% of all female deaths in the developing world to indoor
air pollution. This project aims to assess the short- and long-term
effectiveness of various social and economic incentives at inducing
rural villagers in Bangladesh to acquire and use an improved cookstove.
The health benefits of the improved cookstove will be assessed by measuring
the real-time exposure of the cook to indoor particulate matter (smoke)
before and after changing cookstove technologies.
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Indoor Bioaerosols in Home Environments ˆ Hildemann,
L. M. (Clorox Company) Individuals in the U.S. spend ~90% of their
time indoors, where the concentrations of airborne particles ("bioaerosols")
like molds and fungi can be much higher than outdoor levels. This study
will measure bioaerosols inside and outside of typical homes, assessing
how building characteristics (e.g., flooring type, age of structure)
and the behavior of residents (e.g., cleaning frequency, activity level,
presence of pets) influence the concentration levels of molds and fungi
present.
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Characterization of Particulate
Matter Generated from the Operation of Motor Vehicles – Hildemann,
L. M. (Ford Research Foundation) Increasing regulations on particulate
matter (PM) emissions over the next decade are expected to impact
the motor vehicle industry. A major issue.is whether these new regulations
will be based on the mass, the number,or the chemical composition
of the PM. This research will examine and develop new technologies
for measuring the chemical composition of PM in modern-day motor
vehicle emissions.
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Studying the Mixing State of
Aerosols and Its Impact on Global Climate – Jacobson, M. Z. (NSF) The goal of this project
is to analyze the effect of the mixing state of aerosols on global
and regional direct forcing and temperatures. One scientific question
to be addressed is, what is the global- and regional-scale mixing state
of aerosol-particles and what is the resulting direct radiative forcing?
A second question is, which feedbacks of aerosol-particles to climate
are important and which ones are not? A third question is, what are
the climate effects of (a) fossil-fuel soot and organic matter, (b)
biomass burning gases and particles, (c) sulfur dioxide and resulting
sulfate, and how do the effects of these components compare with the
effects of CO2 and CH4?
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Studying the Effects of Ca,
Mg, and K on Aerosol Size and Composition, NOy, and Radiative Transfer – Jacobson, M. Z.
(NASA). This is a project to study the effects of calcium, magnesium,
and potassium on aerosol size and composition. These chemicals, present
in soil dust and/or sea spray, have been found to have an important
effect on aerosol size distributions in and relatively clean air, shifting
nitrate from the coarse mode to the accumulation mode. For this study,
the feedback between these chemicals on radiative parameters, such
as UV, total solar, and infrared irradiance and top-of-the-atmosphere
radiative forcing will be examined. The calculations will also be coupled
with gas-phase chemistry to estimate the effects of Ca, Mg, K, and
total aerosols on gas-phase NOy concentrations. The purpose of this
exercise is to estimate the extent to which aerosols as a whole and
individual aerosol components affect the NOy:NOx ratio, which is typically
overpredicted in many models.
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Studying the effects of source-specific
gas and particulate emissions on global climate and atmospheric composition – Jacobson,
M.Z. (NASA) This is a project to study the effects of controlling
current and future anthropogenic gas and particulate emissions on global
climate and atmospheric composition. The proposal involves the development
of current and future global anthropogenic gas and particulate emission
inventories by source category and the global simulation of the climate
response and atmospheric composition resulting from changes in emissions.
The overall goal of the study is to improve our understanding of the
effects of different gas and particle emission sources on climate and
on atmospheric composition. The research is a collaborative effort
among scientists at Stanford University and Argonne National Laboratory.
For this study, up-to-date and estimated future global emission inventories
for all important gas and particle components from biomass burning,
coal, natural gas, biofuel, diesel, and gasoline, will be developed.
The inventories will be used, together with existing inventories from
other gas and particle sources, in an air-pollution/climate model to
examine effects on global climate and atmospheric composition. Such
a study is important from a scientific and policy perspective. It will
try to address questions such as, what are the time-dependent combined
effects of biomass-burning gases and aerosol particles on climate and
what are the time-dependent climate effects of combined gas- and aerosol
particle emissions from diesel vehicles, gasoline vehicles, power plants,
and indoor biofuel/coal burning. This study will also enable an examination
of the global distribution of gas and particle components. It will
allow an examination of the climate response of nitrogen oxide (NOx)
and reactive organic gas (ROG), methane, and carbon monoxide emissions
through their feedback to tropospheric ozone and secondary particulate
matter.
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Using satellite data and models
to study the effect of global climate on regional pollution and vice
versa – Jacobson,
M.Z. (NASA) This is a project to use satellite data with models to
examine the effects of regional pollution on the global atmosphere
and the effects of global chemical and climate change on regional air
quality. The project involves three major task areas: gathering and
gridding appropriate satellite and in-situ data for comparison with
models, comparing models on the global and regional scales with the
satellite retrievals and the in-situ data, and using the models to
address the main issue listed. The effect of global chemical and climate
change on regional air quality will be evaluated with a nested global-through-urban
scale air pollution/climate/weather forecast model. Baseline simulations
for 2001 will be run and compared with satellite retrievals, sounding
data, and with data from a network of several thousand near-surface
monitoring stations. The global portion of the model will then be applied
to simulate changes in climate over multiple years due to estimated
changes in greenhouse gas and particulate emissions determined from
Special Report on Emission Scenarios (SRES) scenarios. The effects
of climate change on air pollution in the nested grids will be evaluated
in years 20 and 50. Simulations will be affected by estimated changes
in future global emissions. The effects of regional pollution on the
global atmosphere will be examined by first comparing results from
two regional models with satellite data and in-situ measurements from
a field campaign, then examining the fate of the pollutants as they
exit from the urban/regional to larger scale. Sensitivity tests will
be run under both current and future climate and emission conditions
to examine the relative importance of different organic gases, emitted
on the urban/regional scale, on export of ozone and aerosols to the
large scale. Sensitivity tests will also examine the effect of model
grid resolution and subgrid treatment on ozone and aerosols venting
and dilution from the urban to larger scales.
Exposure to Secondhand Smoke:
Effects of Proximity -- Hildemann, L.M. (Tobacco-Related Diseases Research Program) The
level of secondhand smoke to which an individual is exposed depends
on that person's proximity to the smoker, as well as on the fluid mechanics
of the environment. This field project will measure the magnitude of
the near proximity effect in typical indoor and outdoor environments,
over a length scale of a few meters, using a large array of real-time
carbon monoxide monitors. These data will be used to develop a model
that accounts for the proximity effect as well as background concentration
levels in predicting smoke concentration levels as a function of location
relative to a smoker, and this model will be tested via experiments
with actual smokers.
Human Exposure Analysis for
Pollutants from Secondhand Smoke -- Hildemann,
L.M. (Flight Attendant Medical Research Institute) This project will
test and develop the utilization of real-time particle monitors for
assessing tobacco smoke concentrations in indoor environments where
there is smoking. Measurements will be taken of airborne particle concentrations
as a function of distance from both smolder-smoked cigarettes and actual
smokers. Comparisons will be made between CO and PM levels to assess
whether turbulent or molecular diffusion dominates dispersion processes
in the indoor environment. With these and other data, an Incremental
Exposure model will be developed to assess how different microenvironments
and/or proximities to smoking activities contribute to a person's daily
exposure to secondhand smoke..
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Transport
and Fate of Contaminants in Groundwater
Analysis
of Halogenated Organic Particle-Scale Desorption via Column Studies and
C-13 Solid State NMR Spectroscopy - Reinhard, M. (EPA)
Research has shown that a significant fraction of organics sorbed to soils
and sediments (geosorbents) resists desorption. This fraction is not amenable
to conventional treatment and needs special consideration in fate and
transport assessment. In this project we identify sorbent properties that
govern slow desorption and compare results of desorption studies with
predictions based on mechanistic models. The approach is to artificially
contaminate geosorbents with TCE, deuterated TCE and/or PCE either individually
or as mixtures and to quantify rate of desorption as a function of initial
sorbent loading and desorption conditions. Data suggest that the sorption
sites of the slow desorbing fraction reside in micropores and that diffusion
of is sterically hindered.
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Field-Testing of Palladium-Catalyzed Hydrogenation for Chlorinated
Hydrocarbon Removal - Reinhard, M. and Roberts, P.
This project aims to evaluate palladium catalyzed hydrodehalogenation
using hydrogen gas as a method for removing halogenated hydrocarbon
compounds form contaminated water. Preliminary studies indicate that
hydrodehalogenation proceeds under mild conditions when facilitated
by a palladium catalyst. The project goal is to gain operational experience
with the H2/Pd process under field conditions. Specifically we aim
to: 1) quantify catalyst efficacy; 2) identify and minimize the factors
contributing to catalyst fouling; 3) measure competing reactions and
determine their hydrogen consumption; 4) evaluate the need for pretreatment;
and 5) determine how best to supply hydrogen safely and economically.
Results will be used to optimize the process, provide design criteria,
and evaluate cost effectiveness compared with alternative treatment
methods.
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The Fate and Transport of Wastewater Indicator Compounds During Groundwater
Recharge with Water of Wastewater Origin - Reinhard, M. (Orange
County Water District).
In many water-short areas treated effluents are often the only alternative
to augment existing water supplies. Increasingly, effluents are treated
so that they can be percolated into the ground to augmented depleted
aquifers. This project aims to assess the microbial, chemical and physical
processes that affect the fate and transport of anthropogenic contaminants
during water percolation and groundwater transport. The data will be
useful for developing models that predict the water quality of recharge
water as a function of source water quality, soil type, residence time
in the ground, and travel distance. Such models will serve to develop
science-based regulations for artificial water reuse operations.
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Diffusional Rate Limitations in Heterogeneous Porous Media: Model Structure,
Scale, and Geologic Characterization - Freyberg, D.L. and P.V.
Roberts (EPA)
This recently completed project focuses on elucidating the nature and
environmental significance of both physico-chemical and apparent diffusional
rate limitations during solute transport in saturated, heterogeneous
porous media, with a view to evaluating the role of diffusional limitations
in contaminant remediation. The research considers the relative importance
of diffusion and slow advection manifested over a range of spatial
scales, from the grain scale up to regional scales, within the context
of analytical and numerical transport models that account for advection,
diffusion, dispersion, and sorption.
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Strategies for Maintaining Open Water in a Rapidly Sedimenting, Small
Reservoir - Cohen, P.S. and D.L. Freyberg (Packard Foundation)
Searsville Lake is a small reservoir on Stanford's Jasper Ridge Biological
Preserve which is rapidly filling with sediments from the Corte Madera
Creek watershed. The reservoir provides important avian habitat and
is used actively in both research and teaching at the Preserve. This
project is exploring opportunities to manage the sediment flux tthrough
Searsville Lake so that a modest amount of open water can be maintained
in the reservoir.
Assessing the Water Balance for Large Ephemeral Streams in Arid Environments
- Freyberg, D.L. (USGS student support)
Ephemeral channels in arid and semi-arid environments are an extremely
important hydrologically and ecologically. Flow in ephemeral channels
is complex, involving short, rapidly rising and falling hydrographs,
significant sediment and debris transport, and nearly complete infiltration
of the flow over a channel reach. Closely coordinated with an ongoing
USGS field data collection project, this dissertation research couples
field data with numerical modeling in an attempt to better characterize
and predict groundwater recharge from ephemeral channels.
Engineering Pedagogy--Teaching Turbulent Diffusion in Engineering Fluid
Mechanics - Freyberg, D.L. and J.R. Koseff (NSF student support)
This doctoral research project focuses on the pedagogy of engineering
fluid mechanics, in particular, teaching and learning the concept of
turbulent diffusion. Closely coupled with laboratory research studying
the role of turbulent diffusion in the foraging behavior of lobsters,
this doctoral project is using advances in science education, cognitive
science, and psychology, along with carefully designed experimentation
and testing, to develop effective teaching techniques for a key, difficult
concept in fluid mechanics.
Characterization and Modeling of Sorption Processes for the Nevada
Nuclear Waste Storage Investigations - Leckie, J. O. (Los Alamos
National Laboratories)
The objectives of this research is to investigate the adsorbtive behavior
of the uranyl and neptunyl ions in aqueous systems continuing goethite,
hematite and, possibly, feldspars. These studies will include experimental
work with competing ligands (e.g., carbonate, EDTA, natural humics)
as well as studies to investigate competitive behavior with calcium
and magnesium. The resulting data will be modeled using surface complexation
models.
Radionuclide Speciation in Heterogeneous Aqueous Geochemical Environment
- Leckie, J. O. (Sandia National Laboratory)
This project is concerned with experimental and theoretical studies
of the interaction of radionuclides with mineral/solution interfaces
likely to be found in the WIPP site high level waste repository. The
experimental part involves both time dependent and equilibrium studies
of neptunyl and uranyl ion interactions with clays and hydrous iron
oxides over a range of ionic strengths (1 x 10-3M - 3M) and in the
presence of competing ligands. The theoretical aspects are concerned
with the development of modeling approaches for adsorbate interactions
with clay surfaces.
Particle-Particle Interactions in Marine Systems: Steady-State, Continuous
Flow, Aggregation Studies - Leckie, J. O. (NSF)
Four linked objectives highlight this proposed study of aggregation/sedimentation
dynamics. First, a new type of laboratory apparatus will be developed
to allow previously unachieved simulation of a continuous flow, steady
state system. The simulation apparatus is designed for study of real
time aggregation from the simplest processes to relatively complex,
biologically mediated processes in controlled, reproducible conditions.
Second, two innovative particle size measuring technologies are proposed
which allow noninterfering observation of aggregation/sedimentation
dynamics. Development and adaptation of these techniques aims at avoiding
the sampling artifacts, limited size range and restrictive fluid and
particle requirements inherent in many traditional measuring techniques
(i.e., electrozone, settling rate). Third, an experimental sequence
is suggested which uses controlled variations of particle type, surface
chemistry and fluid conditions to assess the interplay of physical,
chemical and rudimentary biological factors that have been scantly
addressed by previous research. Particular effort is devoted to elucidating
both the unique and interactive mechanisms by which exopolymers from
selected marine organisms enhance or retard aggregation. Fourth, laboratory
findings will be modeled to provide a usable tool for future predictive,
design, and analytical work.
Pore-Scale Hydrodynamics and Physicochemical Transport. Constitutive
Relations of Solute Transport and Transformation at the Darcy Scale -
Kitanidis, P. K. (WRHSRC, NSF, DuPont)
In terms of physico-chemical fundamentals, the transport and transformation
of reactive solutes is most satisfactorily understood and quantified
at the pore scale. However, this scale is too microscopic for almost
all practical applications. In practice, the smallest scale for modeling
the transport and chemical fate of solutes in porous media is the laboratory
or Darcy scale, which is much larger than the pore scale. At the Darcy
scale, a complex medium that actually consists of pores, a solid matrix
with biofilm, etc., is replaced by a homogenized medium characterized
by constitutive relations among macroscopic variables and parameters.
The general advection-dispersion-reaction equation, which is the starting
point of every practical modeling effort, is based on these relations
and parameters and purports to describe the transport behavior of a
concentration spatially averaged over a block of the order of at least
centimeters. What is the appropriate form of this equation and what
parameters should be used? This research aims at providing answers
to these questions. The methodology followed is to model flow, transport,
and chemical transformations at the pore scale and then to scale up
in order to derive constitutive equations and parameters. The constitutive
equations and parameters to be obtained will thus be consistent with
the fundamental physico-chemical principles as well as the heterogeneity
of the medium. The longer-term objective is to promote a firmer understanding
of the factors that control the transport and chemical fate of pollutants,
substrates, and electron acceptors at the Darcy scale.
Factors Controlling Solute Dilution in Heterogeneous Formations -
Kitanidis, P. K. (NSF, SGF)
Although the effect of heterogeneity on the spreading of contaminant
plumes has been studied, the effect of heterogeneity on dilution remains
to be determined, especially at "early" times relevant in
tracer tests and remediation projects. Dilution is measured by the
peak concentration and the volume occupied by solute. Spreading is
quantified by the spatial second moment of the concentration distribution.
In assessing environmental impacts of groundwater contamination, it
is important to be able to anticipate peak concentrations, not just
the spatial extent of contamination. We conduct theoretical analysis,
detailed numerical simulations, and comparisons with field data. Contaminant
dilution measures are related to the porous media constitutive parameters
and, primarily, the variability of hydraulic conductivity and the local
dispersion. Predictions of dilution are made via analytical approximations,
which lead to predictive partial differential equations. The approximations
validity is assessed through numerical simulations and the results
are evaluated by comparison with results from field experiments. Objectives:
(a) a better understanding of the time-evolution of contaminant concentration
levels, and (b) guidelines to the practitioner for assessing dilution
of contaminants in heterogeneous geologic formations.
Use of In-situ Bioaugmentation for Remediation of an Aquifer Contaminated
with Carbon Tetrachloride - Phase III - Criddle, C.S. (Michigan
Department of Environmental Quality)
This project involves full-scale demonstration of bioaugmentation for
remediation of a site contaminated with carbon tetrachloride. Among
the many issues explored are factors affecting transport and competitiveness
of a non-native microorganism, carbon tetrachloride degradation, denitrification,
chemical delivery, and the role of subsurface heterogeneity.
In Situ
Stabilization of Persistent Organic Contaminants in Marine Sediments -
Luthy, R.G., U. Ghosh, R.N. Zare and collaborators at the US Army Engineer
Research and Development Center, Vicksburg, MS and the University of
Notre Dame (US Department of Defense, Strategic Environmental Research
and Development Program) The addition of coal-derived sorbents is being
evaluated as a treatment technology to reduce the bioavailability and
toxicity of polychlorinated biphenyls [PCBs] and polycyclic aromatic
hydrocarbons [PAHs] in sediments. This work comprises a suite of tests
with contaminated sediment from Hunters Point Naval Shipyard, San Francisco
Bay.
Contaminated Sediment Processes and Bioavailability - Luthy, R.G.,
S.G. Monismith, D. Epel and R.N. Zare (Stanford University Bio-X Interdisciplinary
Initiative Program and collaborators at the US Geologic Survey, Menlo
Park, CA) Organic contaminants in sediments pose long-term risks to human
health and the environment. This project seeks to understand how the binding
of organic contaminants with sediment particles affects the uptake and
accumulation of polychlorinated biphenyls [PCBs] and polycyclic aromatic
hydrocarbons [PAHs] by particle-feeding organisms, such as clams native
to San Francisco Bay.
Characterization of Lampblack Materials in Soils - Luthy, R.G.
(Gas Technology Institute, Chicago, IL) Lampblack was produced as a by-product
from the former oil gasification processes used in California. The distribution
and binding of polycyclic aromatic hydrocarbons [PAHs] in lampblack material
from field sites are studied to assess how this material binds the PAHs
and reduces exposure.
Microscale Characterization of the Binding and Sequestration of Nitroaromatics
in Soils - Luthy, R.G. and U. Ghosh (US Army Engineer Research and
Development Center, Vicksburg, MS, and University of Notre Dame) Microscale
analytic techniques are applied to soils contaminated with TNT to assess
whether crystalline TNT exists in the soil and how this affects the biotreatability
of TNT-impacted soils from Army ammunition sites.
PAH and PCB Binding to Sorbent Material - Luthy, R. G. (Ford Motor
Company) Mass transfer and phase partitioning studies are evaluating the
rate of transfer of PAHs and PCBs from contaminated sediment to sorbent
material.
Cyanide Measurement and Chemistry in Wastewater Effluent - Luthy,
R. G. (Water Environment Research Foundation and others; with Carnegie
Mellon University, Malcolm Pirnie, Inc and Clarkson University) A multi-investigator
project is evaluating cyanide measurement and speciation at low levels
in chlorinated effluent. The effect of chlorination on possible formation
of cyanide at low levels is studied. The collaborators include various
large municipal wastewater treatment plants across the United States.
(with David A. Dzombak, Carnegie Mellon University)
Mobility of PCBs in Contaminated Soils/Sediments - Luthy, R. G.
(US EPA) A novel passive, wick sampler is designed to measure hydrophobic
organic compounds in soil pore water. Laboratory tests assess the device's
hydraulic performance and capture efficiency for chlorinated aromatics.
The role of separate phase oil containing PCBs is modeled to evaluate
the release of PCBs from hydraulic oils in sediment and soil (Sean McNamara).
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Contaminant
Control Technology
Toxic Trace Metal Removal Processes - Leckie, J. O. (WRHSRC, EPA)
General project objectives are to study the adsorption/desorption characteristics
of toxic metals and metalloids, including radionuclides as well as stable
isotopes, under conditions where competing organic ligands are present
and where remobilization might occur (e.g., contaminated ground water
systems, mixed industrial wastes). The investigation will focus on several
of the following: Cd, Ni, Pb, Cr, Cu, Co, As, and/or Se. The selection
of organic ligands will include commercially used sequestering agents
(e.g., EDTA) as well as metabolic products from microbial degradation
of organic matter. Major experimental variables are pH, temperature, type
and concentration of solid, organic ligand and ionic strength. In addition,
the fundamental aspects of adsorption reactions of trace metal ions within
the pores of porous particles will be studied. This aspect of the study
will focus on cases where overall rate of adsorption is limited by internal
mass transport constraints. Part of the intent in studying the internal
mass transport limited adsorption is to define the chemical and physical
limitations of the adsorption process as a function of pore size distribution
and to describe the observed phenomena in a mathematical format.
In Situ Anaerobic Bioremediation of Fuel Contaminated Ground Water
- Reinhard, M. (Office of Naval Research).
Ground water contaminated with fuel is typically anaerobic. Under these
conditions, microorganisms will use alternate electron acceptors in the
order nitrate, sulfate, and carbon dioxide to degrade petroleum derived
contaminants. This project aims to demonstrate and evaluate the efficacy
of in situ bioremediation that relies on the addition of low doses of
alternate electron acceptors. The approach is to amend a contaminated
zone of an anaerobic gasoline plume with mixtures of alternate electron
acceptors and to observe the enhanced removal of hydrocarbon contaminants.
The data will be used to demonstrate the technical viability of anaerobic
bioremediation approaches.
Palladium Catalyzed Reduction of Water Contaminants Under Environmental
Conditions - Reinhard, M. (EPA).
Many halogenated hydrocarbon compounds are rapidly dehalogenated by hydrogen
gas in the presence of a heterogeneous metal catalyst. In addition, catalyzed
hydrogenation rapidly reduces some inorganic oxyanions such as nitrate
to less toxic forms. The objective of this project to establish the mechanistic
basis for designing metal catalyzed detoxification processes. The reactions
that occur during simulated treatment at the catalyst surface are investigated
using kinetic and surface analytical methods.
Reductive Transformation of Chlorinated Ethenes Catalyzed by Vitamin
B12 - Reinhard, M. (WRHSRC).
Transition-metal coenzymes such as vitamin B12 have been implicated as
the responsible agents in the respiratory of cometabolic dehalogenation
of chlorinated hydrocarbon compounds. Potential biological dehalogenation
pathways have been derived from studies in abiotic systems in which catalytic
amounts of Ti(III) were used as the bulk reductant. The overall objective
of the project is to improve our understanding of the chemistry of B12
mediated dehalogenation reactions. The kinetics of trichloroethylene (TCE)
dehalogenation is being studied in abiotic model systems with Ti(III)
as the reductant and B12 as the catalyst. The results obtained in abiotic
systems are compared with results obtained in biological systems.
Heavy Metals Incorporation into Ceramic Crystalline Matrix - Leckie,
J. O. (EPA) The objective of this project is the illucidation of the physical-chemical
processes by which selected heavy metals (Pb, Cr, Cu, Co, Cd) are incorporated
into the ceramic matrix during firing of clay/metal bearing sludge mixtures.
Details of the bonding and location of metals in the ceramic crystalline
matrix will be studied using XRD, EXAFS, XPS and SEM. Additional spectroscopic
tools include NMR and FTIR. The major experimental variables are type
of metal, metal /clay ratio, time and temperature of firing process.
In Situ Treatment of Chlorinated Solvents - McCarty, P. L. (DuPont
Chemicals, WRHSRC, EPA, DOE)
Several species of bacteria have been isolated and identified by others
that have the ability to reductively dehalogenate chlorinated aliphatic
hydrocarbons (CAHs). However, an individual or group of organisms responsible
for the complete dehalogenation process from tetrachloroethylene (PCE)
to ethene has not yet been identified. The objectives of this study are
to describe the bacterium or groups of bacteria that are responsible for
conversion of tetrachloroethene (PCE) to ethene in aquifer samples taken
from a contaminated site in Victoria, Texas, and to examine the factors
affecting the rate and extent of transformation.
Mechanisms,
Chemistry, and Kinetics of Anaerobic Biodegradation of cDCE and VC - McCarty,
P.L. and Spormann, A.M. (U.S. DOE and DuPont Chemicals)
Biological reductive dehalogenation of the chlorinated ethenes, tetrachloroethene
(PCE) and trichloroethene (TCE) to cis-1,2-dichloroethene (cDCE), vinyl
chloride (VC) and then ethene is of great interest both for natural attenuation
and engineered remediation of these hazardous contaminants in groundwater.
This study was directed towards a better understanding of the factors
affecting the rate and extent of conversions of cDCE and VC to ethene,
which are generally considered the rate limiting steps in the overall
process. The objectives of this study are to (1) determine the biochemical
pathways for reductive dehalogenation of cDCE and VC, including identification
of the enzymes involved, (2) determine the chemical requirements, especially
the type and quantity of electron donors needed by the microorganisms
for reductive dehalogenation, and (3) evaluate the kinetics of the process
with respect to the concentration of both the electron donors and the
electron acceptors (cDCE and VC).
Hydrodynamic
and Biological Factors Affecting Aquifer Clogging During In-Situ Bioremediation
- McCarty, P. L. (WRHSRC, EPA) With in-situ bioremediation processes,
bacteria are stimulated to grow on substrates introduced into groundwater.
When this is done, there is a potential for clogging of the aquifer by
excessive bacterial growth, thus restricting the movement of groundwater
and making it difficult to introduced additional chemicals. The object
of this study is to learn better how clogging of aquifers occurs, and
what characteristics of the aquifer, the chemicals introduced, and microorganisms
contribute most to the clogging problem. In order to study these factors,
a laboratory investigation is being conducted in which enhanced imaging
is used to better evaluate the hydrodynamic and biological factors involved.
Field
Demonstration of Vertical and Horizontal Recirculation Wells for In Situ
Treatment of Chlorinated Solvent Contaminated Groundwater - Mark N.
Goltz, Perry L. McCarty, Steve M. Gorelick, and Gary Hopkins. (Strategic
Environmental Research and Development Program) The purpose of this study
is to evaluate the potential for removal of chlorinated organic solvents
at their source in an aquifer by combining two processes, in-well vapor
stripping and in situ aerobic cometabolic biodegradation. The combined
system is termed BioEnHanced In Well Vapor Stripping (BEHIVS). The system
will be evaluated at full scale in the field at a trichloroethylene (TCE)
contaminant groundwater site at Edwards Air Force Base.
Development of Effective Aerobic Cometabolic Systems for the In-situ
Transformation of Problematic Chlorinated Solvent Mixtures - Lewis
Semprini, Daniel Arp, Perry L. McCarty, and Gary Hopkins (Strategic Environmental
Research and Development Program) The goal of the proposed research is
to demonstrate the potential of using propane and butane-utilizing microorganisms
to transform problematic chlorinated solvent (CAH) mixtures in groundwater.
The demonstration at the Moffett Federal Airfield Test Site will be aimed
towards recirculation well treatment systems that can be used to create
bioreactive passive barriers in contaminated aquifers. Our research with
microorganisms stimulated on propane or butane has demonstrated the potential
for transforming a broad range of CAH mixtures that have been problematic
with other cometabolic substrates. Microcosm studies conducted with subsurface
solids and groundwater from contaminated DOD sites, however, have shown
that propane and butane-utilizers are often absent in the subsurface,
or have long lag periods before effective stimulation is acheived. The
proposed work will demonstrate effective methods to create passive treatment
barriers through both bioaugmentation and the use of recirculation well
technology. Microbial growth and maintenance for effective cometabolic
treatment will be achieved through propane or butane addition to the subsurface.
In addition, we will explore the use of mixed cometabolic substrates for
the treatment of problematic CAH mixtures.
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Environmental
Planning and Management
The following is a current list of projects that are being either
undertaken or supervised by Leonard Ortolano, UPS Foundation Professor
of Civil Engineering. Several of these projects are being undertaken
by Ph. D. students in the Interdisciplinary Program on Environment
and Resources ( http://iper.stanford.edu ) and
by Professor Ortolano with recent Stanford Ph D graduates
Policy-Level Strategic Environmental Assessments: Lessons
from Case Studies and National Program Evaluations
Interest in the application of environmental assessment procedures
to policy proposals is growing. Six case studies and two national program
evaluations are analyzed to identify lessons that can be drawn about
the state of the practice of policy-level strategic environmental assessment
(SEA). The analysis shows that SEA's influence on policy outcomes depends
heavily on how assessments are integrated into policy design. Based
on the case studies, a typology consisting of four modes of integration
is presented. For some (but not all) approaches to integration, SEAs
can be an effective mechanism for enhancing inter-agency coordination
and public involvement in policy making and for integrating environmental
considerations into policy design. The national evaluations show that,
in many instances, ministries required to prepare SEAs on proposed
policies do so in a pro forma fashion, and the SEAs do not significantly
influence policy outcomes. Strategies are proposed for augmenting existing
incentives so that the full potential of policy-level SEA can be realized.
Implementing French Policies to Regulate Agricultural Pollution
of Groundwater
The design and implementation of regulations
to control groundwater pollution from agriculture is a subject of
considerable significance throughout the world. There is considerable
interest in the French approach to this regulatory issue because
of the existence of water management institutions linked to France's
six water agencies). These agencies, which cover all of continental
France, have a unique approach to integrating stakeholder participation
in the creation of basin-wide water management plans. The agencies
also have economic tools - in the form of water fees, effluent charges
and subsidy programs - that influence plan implementation. This research
investigates the strategies used by these agencies to assist in regulating
groundwater pollution from agriculture, such as pollution of aquifers
with nitrogen from feedlots. The approaches taken by the French water
agencies must be consistent with both applicable European Union directives
and the complex inter-ministerial arrangements for enforcing environmental
rules that existed before the agencies were created. This research
identifies characteristics of the French strategy for controlling
pollution from agriculture are successful, and it aims to identify
general lessons that can be learned from the French experience.
Influence of a Water Rights Markets on Settlements of Environmental
Disputes in New Mexico
After decades of contention, several long-standing water disputes
in New Mexico have reached the stage of settlement without relying
on the State's complex and time-consuming process for adjudicating
water rights. These conflicts involve diverse groups including Native
American tribes with sovereign nation status, irrigation-based acequia communities
where water rights descend from Spanish land grants, irrigation districts
and other farmers and ranchers, residential well owners, urban and
industrial water users and environmental interests. In attempting to
untangle the factors that have encouraged this relatively sudden movement
toward settlements, this research focuses on the influence of emerging
markets in water rights. The linkages between the rights markets and
settlements exist because settlements allow senior rights holders to
legally define their rights and thereby make them both enforceable
and marketable. Junior rights holders, fearing that they may lose the
water they currently are able to access, welcome the settlements because
they can purchase water rights on the market. This research is being
done with the collaboration of Sandia National Laboratory and with
the cooperation of several offices of the New Mexico state government.
Cooperatives, Social Networks and the Supply
of Water to the Poor in Argentina
In many parts of Argentina,
the poor have gained access to drinking water by organizing themselves
into cooperatives, voluntary membership organizations that are democratic
and member controlled, and that have a "double bottom line":
they must remain financially sustainable and deliver water to all
their members, including the poor. These two goals are sometimes
in conflict. This research investigates propositions concerning how
social networks among members of cooperatives, and affiliations between
leaders of cooperatives and local elites, affect the ability of cooperatives
to meet their dual goals. The research includes a survey of all cooperatives
delivering water supply services in Argentina as well as in-depth
case studies of water cooperatives operating in the peri-urban areas
of Buenos Aires.
Organizational Learning in Small Community
Water Providers in California
This research, which aims to better
understand how rural water supply infrastructure can provide reliable
and safe drinking water supply in a sustainable fashion, focuses
on how small community water providers learn to solve problems and
adapt to changing circumstances. Organizational learning in small
community water providers is conceptualized in a way that recognizes
ways in which small water providers in California interpret their
external environments, and the research considers the capacity of
these organizations to respond to exogenous institutional factors.
A comparative case study analysis is being conducted of several small
community water providers in California. Results from this
research will contribute to organizational learning theory as well
as to the development of innovative learning tools for small water
systems.
Contentious Politics in Liquefied Natural
Gas Facility Siting in California
The siting of locally
unwanted land uses (LULUs) - for example, hazardous waste facilities,
landfills, prisons, and power plants - continues to be a challenging
task. The goal of this research is to better comprehend the context
and factors that spark local community mobilization and to understand
mobilization processes in the context of LULUs. Efforts to site Liquefied
Natural Gas facilities in California provide a basis for studying
community mobilization processes in detail. A number of hypotheses
- drawn from the facility siting, public participation and social
movements literatures - related to community mobilization around
LULU siting proposals can be derived. Use of a comparative case study
methodology allows for the continual refinement of hypotheses while
gathering new information in the different contexts surrounding each
case.
Effects of China's Legal System on Enforcement of Environmental
Regulations
Increasingly, polluters facing environmental penalties in China are
relying on laws that allow them to challenge the government's regulatory
decisions in court. Plaintiffs in these cases can prevail if they are
able to demonstrate that regulators erred in imposing penalties. Research
at municipalities in Hubei Province is investigating whether and how
these legal actions by polluters have affected both the organizational
structures and administrative procedures used by local environmental
protection bureaus. The focus is an enforcement procedures used by
these bureaus. Qualitative aspects of the research rely on a multiple
case study designs where each case relies on legal documentation as
well as interviews with lawyers, judges, plaintiffs and environmental
officials among others. Quantitative data based on archival court records
is also compiled and analyzed. The research is being conducted in collaboration
with the Environmental and Resource Law Research Center of the Zhongnan
University of Economics and Law in Wuhan.
Adoption and Implementation of Vehicle Emission Standards
in Chinese Cities
Automobile ownership in China has grown
rapidly since the 1980s, and many large cities have experienced serious
air pollution problems due to releases from automobile tailpipes.
Since the mid 1990s, automobiles have become the primary source of
urban air pollution in China. To tackle this problem, in the 1990s
governments at both local and national levels began to take strict
measures to control emissions from vehicles. Arguably, the most prominent
of these measures was the stringent "Euro
series" of vehicle emission standards, which refers to a series
of European emission standards, such as Euro I, and Euro II. The process
of adopting and implementing the Euro series has not been a smooth
one. In some cases, national agencies simultaneously issued inconsistent
vehicle emissions regulations, and in other cases, the regulations
issued were not implementable. This research uses alternative models
of organizational decision making to explain inconsistencies and shortfalls
in implementation. It also focuses on the implementation of emission
control requirements in Beijing and Shanghai. A large data set on emission
test results for sections of Beijing is used to investigate whether
some motor vehicle models have consistently had difficulties in meeting
tailpipe emission standards. This part of the study relies on both
descriptive statistics and logit modeling.
Policy Change in Japan: the Tokyo Metropolitan Government's
Regulation of Diesel Pollution
For many years, the government of Japan had a fairly relaxed policy
towards the regulation of emissions from diesel vehicles. Due in large
measure to diesel pollution, air quality in Tokyo declined substantially
in the late 1980s and remained poor in the following decade. In 1999,
Tokyo took the initiative in modifying diesel emission regulations
and made them much more stringent than the national requirements. This
research examines reasons for Tokyo's actions and the extent to which
these actions caused the national government to change diesel emission
regulations for the entire country. The study also investigates how
Tokyo's new policy structured the Japanese domestic market for diesel
pollution control technologies. In addition, the research employs a
quantitative approach to calculate the influence of Tokyo's new policy
on total emissions from diesel trucks.
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Environmental
Microbiology and Biotechnology
Biochemistry and Genetics of Anaerobic Oxidation of Aromatic Hydrocarbons
- Alfred Spormann (NSF)
Oxidation of aromatic hydrocarbons, such as benzene, toluene, ethylbenzene,
and xylenes (BTEX) by anaerobic bacteria is of considerable biochemical
and environmental interest. The enzymes involved in the initial degradation
reactions of these substrates are dramatically different from the well-characterized
aerobic oxidation reactions: In all aerobic pathways, the initial reactions
involve mono- or dioxygenases that require molecular oxygen as a substrate.
Anaerobic bacteria face the biochemical problem of how to perform the
first oxidation step in the absence of molecular oxygen.
From an environmental point of view, degradation of these aromatic hydrocarbons
is important, because they represent major components of the water soluble
fraction of gasoline fuel. Leaking underground fuel storage tanks or surface
spills often release these compounds into aquifers. Through research in
the recent years, two fundamentally different modes to initiate anaerobic
mineralization of alkylbenzenes are emerging: Methyl benzenes are activated
by addition of the methyl groyup to fumarate, and benzylsuccinate synthase
represents the prototype of this reaction. Alkylbenzenes with side chain
lengths of * 2 carbons are anaerobically oxidized at the methylene carbon
for which ethylbenzene dehydrogenase serves as the prototype.
One focus of our research is the novel enzyme benzylsuccinate synthase
which catalyzes as the initial reaction in anaerobic activation of toluene
the addition of the toluene methyl group to fumarate to form benzylsuccinate:
http://www-ce.Stanford.EDU:80/~spormann/Bss%20reaction.JPG
This is a unique non-redox reaction to activate methyl benzenes and also
a novel mode to form a new carbon-carbon bond. This enzyme is of considerable
interest because it carries an organic free glycyl radical. Biochemical
and molecular studies are directed to elucidate the reaction mechanism.
A similar reaction is involved in anaerobic activation of m-xylene.
The other focus is on anaerobic ethylbenzene dehydrogenase which catalyzes
the first reaction in anaerobic ethylbenzene mineralization. Ethlbenzene
dehydrogenase is an unusual enzyme because it catalyzes the oxidation
of a hydrocarbon in the absence of molecular oxygen and converts ethylbenzene
to 1-phenylethanol with p-benzoquinone as electron acceptor. http://www-ce.Stanford.EDU:80/~spormann/EBreactions.JPG
Biochemical studies are conducted with purified enzymes, and gas chromatography
(GC), gas chromatography/ mass spectrometry (GC/MS), HPLC, and spectrophotometry
assist in analyzing these unusual reactions.
A parallel genetic approach is directed to identify the structural genes
involved and to understand the molecular mechanisms of their control.
The current focus of the genetic approach is to generate mutants defective
in aromatic hydrocarbon metabolism, and to isolate and to clone the genes
involved by genetic complementation.
Anaerobic
transformation of chloroethenes and evolution of pathways for transformation
of "unnatural" compounds. - Alfred Spormann (SERDP)
Next to the BTEX compounds, chlorinated alkenes, such as tetrachloroethene
(PCE), trichloroethene (TCE), dichloroethene (DCE), and vinyl chloride
(VC) are another important class of groundwater contaminants in the U.S..
These chlorinated aliphatic compounds are exclusively of anthropogenic
origin and have been introduced involuntarily into the environment only
within the last decades. Chlorinated aliphatic solvents are frequently
used for the degreasing of engines and in dry-cleaning processes. PCE
and TCE, but more importantly VC, are highly toxic compounds, and their
concentrations in drinking water are regulated. Interestingly, under anaerobic
conditions PCE and TCE are metabolized to VC, and, thus, are converted
into a product that is more toxic than the parent compound. From a fundamental
point of view, the microbial transformation of these compounds is very
interesting because these unnatural chemicals were introduced into the
environment only a few decades ago. Nevertheless, pathways that metabolize
these compounds have evolved in some organisms. Thus, research on these
novel microbes that can completely degrade these unnatural compounds allows
us to address the more fundamental question of how novel pathways for
the degradation of unnatural compounds evolve in nature.
Recently, we discovered a novel mode of anaerobic reductive vinyl chloride
transformation to ethylene. Previously known reductive dehalogenation
of PCE, TCE, or chlorobenzoates were shown to involve corrinoids as the
catalytically active reagent. Through inhibitor studies with cell-free
extracts from an anaerobic, VC-dehalogenating mixed culture, we discovered
that VC reduction to ethene does not involve a corrinoid. Current, work
investigates the microbial and molecular mechanism of this novel enzymatic
activity. Understanding the fundamentals of natural dehalogenation of
unnatural compounds will provide crucial knowledge that will allow also
the development of novel in situ strategies to specifically target biodegradation
of VC to this microbial mechanism. Furthermore, understanding this mechanism
may also provide tools for engineering a chemical remediation scheme,
as has been done using vitamin B12-based chemical reductive dehalogenation
of PCE and TCE that was first discovered as a prokaryotic transformation
reaction.
In addition, a novel research approach explores the in vitro engineering
of enzymes with novel catalytic properties for the transformation of recalcitrant
chemicals by use of directed evolution.
Functional Genomics and Physiology of Microbes in Biofilms - Alfred
Spormann, Gordon E. Brown, Jr. (NSF)
Microbial biofilms are structures where microbes are attached to a surface
and embedded in an extracellular polysaccharide (EPS) matrix. Microbial
biofilms form on virtually all aqueous environmental interfaces, including
the surfaces of ships, pipes, and sewers, and on soil mineral particles.
Biofilms are of enormous economic, medical, and biogeochemical importance.
Our work is at the interface of molecular microbiology, molecular microbial
ecology, and biogeochemistry.
Biofilms are dynamic structures and undergo a developmental process consisting
of (i) initial attachment, (ii) microcolony formation, (iii) maturation,
and (iv) detachment. Because cells are constrained in a biofilm and because
free diffusion of small molecules is affected within a biofilm, these
bioflms exhibit a high degree of internal heterogeneity, where the overall
biological activity of a biofilm is controlled by an intricate structure-function
relationship. Therefore, individual cells, as well as the overall microbial
community, respond to changes in the environment. Thus, the activity of
a microbe within a biofilm is a function of its position in the biofilm.
We are studying the cell-cell and cell-substratum intractions using
a new genomic approach in conjunction with confocal laser scanning
microscopy (CLSM). Our goal is to understand and to predict the complex
metabolic and signaling interactions that occur between biofilm microbes.
We use two model microbes, Shewanella oneidensis MR-1 and Vibrio cholerae.
The genome of both microorganisms has been sequenced, and we are using
DNA microarrays to generate profiles of whole cell gene expression
during cell-cell and cell-surface interactions. CLSM is a powerful
technology to visualize individual microbial cells in biofilms and
to visualize the expression of individual genes in biofilm cells.
This allows us to observe directly metabolic and signaling cell-cell
interactions in active biofilms. This CLSM work is conducted here
at the new Stanford Biofilm Research Center.
S. oneidensisutilizes the surface of insoluble Fe(III) minerals as
electron acceptor and forms biofilms on such minerals. The reduced
Fe(II) minerals, in turn, are critically important for geochemical
redox reactions involved in abiotic heavy metal mobilization and
reductive degradation reactions. We are specifically interested in
the molecular processes that control S. oneidensis biofilm formation
and stability, and that are involved in redox reactions between biofilm
cells and the mineral subtratum.
V. cholerae forms biofilms on inorganic and organic, including chitin,
surfaces. It is believed that chitin provides a critical metabolizable
substrate for this microbe to persistent in marine environments. Also
here, we are using a genomic approach to uncover cell-cell and cell-substratum
interactions of V. cholerae in marine environments and on chitin surfaces.
This project is part of an interdisciplinary NSF-funded research effort
(CREAMS) on "Chemical and Microbial Interactions on Environmental
Surfaces"
Reductive processes for the bioremediation of chlorinated solvent metal
mixtures - Craig Criddle, Alfred Spormann (NIEHS).
Mixtures of chlorinated solvenets and metals pose a significant challenge
for bioremediation. This work focuses on the transfer of the the carbon
tetrachloride degradation genes encoding production of pyridine-2,6-bis(thiocarboxylate)
(PDTC) from Pseudomonas stutzeri strain KC to Shewanella oneidensis
MR1 to create an organism with increased metal tolerance and the ability
to dechlorinate carbon tetrachloride.
Field-scale evaluation of biostimulation for remediation of uranium-contaminated
groundwater - Craig Criddle, Peter Kitanidis, and Gary Hopkins
(U.S. DOE).
Microbial reduction of uranium may prevent its migration to receptor
streams. However, application of this technology to field sites is
untested, and future site remediation will require improved understanding
of basic processes and implementation strategies in heterogeneous environments.
The goals of this work are (1) to develop a predictive capability for
the rates and mechanisms controlling microbial reduction of U in heterogeneous
field settings, and (2) to develop a system capable of delivering electron
donor to a highly heterogeneous subsurface environment enabling spatially
uniform in situ immobilization of U in groundwater upon passage through
a subsurface biocurtain. This work involves a 3-phase field study in
a near surface aquifer at Oak Ridge, TN. This aquifer contains very
high levels of nitrate and part per million levels of U(VI). The nitrate
must be removed because it prevents reduction of U, and, if the nitrate
is reduced to N2 the resulting gas could reduce aquifer permeability.
We will test in-situ concepts for nitrate removal: an in-well vacuum
stripper; an in-well bioreactor; and ion selective resins. The most
effective and least expensive system will be coupled to a system for
in-situ uranium removal. By removing the nitrate, we will be able to
impose hydrological and geochemical controls on the U source permitting
reliable determination of U reduction rates within a downgradient biocurtain
for U immobilization. We plan to use field-scale and companion bench-scale
studies to evaluate hypotheses on dissimilatory metal-reducing activity,
and we will be monitoring changes in microbial community dynamics using
molecular methods.
Proof of gene expression during bioaugmentation - Craig Criddle
(WRHSRC, EPA)
Experimental justification for bioaugmentation is typically obtained
by comparing the bioremediation of inoculated and uninoculated samples.
This approach is adequate for bench-scale studies. At full scale, however,
design and operation of uninoculated controls is difficult and expensive.
Inadvertent inoculation of "uninoculated" regions must be
avoided, and the inoculated and uninoculated regions must initially
be geologically, chemically, and biologically similar. Other methods,
besides the use of uninoculated control regions, are needed to establish
that added organisms are in fact mediating the desired transformations.
A logical approach is to prove expression of the genes required for
the desired transformation. Gene expression occurs at different levels
as the synthesis of mRNA (transcription), the formation of polypeptides
(translation), and the biochemical reaction itself. Proof of gene expression
is best obtained at each level, because each piece of evidence strengthens
the conclusion that gene expression is occurring as intended. This
proposal explores each level of gene expression for the bioremediation
of carbon tetrachloride by Pseudomonas stutzeri KC.
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