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Profile of Dorthe Wildenschild, new SBI faculty member in Environmental Engineering
Posted: November 6, 2006
Since 2002, Dr. Dorthe Wildenschild has been a part-time OSU faculty member with a dual appointment in Geosciences and Civil, Construction, and Environmental Engineering. This Fall, Dr. Wildenschild became a full-time faculty member in Environmental Engineering – in part through funding from the Subsurface Biosphere Initiative.
What is the focus of your research?
My specialty is multi-phase flow and transport systems – two examples are air-water systems above the groundwater table where soil is only partially saturated, and immiscible systems, such as groundwater that has been contaminated with an oily substance (non-aqueous phase liquids or NAPLs as we call them).
For the last few years, my focus has been the use of imaging technologies to study these systems at a micro-scale. For example, most groundwater remediation techniques rely on the dissolution of contaminants into the surrounding water. This means that the rate of cleanup is ultimately controlled by the size of the area where the NAPL is in contact with water, rather than with the surrounding sediment grains (see image to the right). As one can imagine, this contact area is not easily measured – but it’s something my colleagues and I have been able to do with a technique called computed microtomography (CMT). CMT is a three-dimensional imaging technique similar to medical CAT scanning. We use synchrotron radiation in the imaging process and can produce really high resolution images (~5-15 micron). The images are so detailed that we can measure things like the area, curvature and spatial distribution of the interfaces between contaminant, water and sediment grains. The technique also allows us to make these measurements without destroying or altering the sample and we can repeat measurements for a wide range of fluid saturations.
Can you describe a couple of your current projects and collaborations?
One exciting collaboration related to the CMT work that I was just describing, is a project I've been doing with Bill Gray, at University of North Carolina. He has developed extensive theoretical descriptions of multi-phase systems based on first principles of thermodynamics. Now we’re trying to combine our micro-scale experimental results with his theory to learn more about these types of flow systems.
Another project I'm working on involves the measurement of some of the variables that control flow and transport in a multi-phase system. To understand and predict flow at, say, a contaminated groundwater site, we need information about the relationship between fluid saturation and fluid phase pressures. This relationship is specific to the porous system in question and is unique for each soil type. It is traditionally measured on small soil cores sampled from the field and the measurement has generally been done over periods of weeks to months. In recent years some people have started to accelerate this procedure by performing the measurements relatively fast. However, we have found that the relationship obtained in this way can differ significantly from the slow (steady-state) measurements. We are carrying out experiments, both at OSU and at the synchrotron to learn more about why this is happening and to find cut-off values for how much we can accelerate these measurements and still get the right results.
One of my PhD students, Mark Porter, is working on the lab experiments and is also running computer simulations to complement these investigations using the College of Engineering’s parallel programming resource (EECS High Performance Computing Cluster). The modeling work also involves Marcel Schaap, at University of Arizona, someone I’ve been collaborating with for over 5 years now.
What motivates your research?
I am really interested in understanding how fluids interact in a porous system. I am fascinated with lava lamps! For a number of years now, the scale of my research focus has become increasingly small - making the experiments smaller and more controlled has allowed me to better understand these processes. I am an experimentalist at heart, but use numerical models and collaborate with theoreticians to extrapolate beyond experiments and try to get at the bigger picture. Overall, I am concerned with keeping our water resources clean and living in a sustainable fashion. I would much rather plan ahead and prevent pollution rather than remediate groundwater later, yet once the damage is done I hope my work contributes to improved ways of cleaning up the mess.
How does your work intersect with the subsurface biosphere initiative?
For a number of years my focus has turned to increasingly small and controlled systems, yet, to apply research findings in a natural setting, such as soils or aquifers, it is necessary to include other disciplines because everything is connected; in most situations, one cannot single out the physics of flow without considering solute transport processes and chemical and biological alterations. The SBI provides a great opportunity for interdisciplinary collaborations and a chance for me to incorporate more biology into my flow and transport studies.
For example, through collaborations with Brian Wood in Environmental Engineering, I have become interested in trying to characterize microbial communities as they form biofilms in porous media using CMT. The actual architecture of biofilms in the subsurface is a bit of an open question, particularly how this architecture evolves in response to changes in hydrodynamics and other growth limiting or enhancing conditions. Our work is part of the broader efforts at OSU to harness subsurface microbial populations to aid in contaminant remediation.
One of my PhD students, Danielle Jansik, is part of the Subsurface Biosphere IGERT Program and is working in this area. She is trying to use phase contrast microtomography to image the biofilm in a system of grains, water, and biomass. Ultimately, she is studying how the evolving biomass influences hydrodynamics -- an important factor when designing and managing bioremediation at a field site. The main hurdle is that the biofilm looks pretty much like water to the penetrating x-rays, so contrast agents are needed for us to be able to distinguish the biomass from the water.
What courses are you teaching?
I am currently teaching ENVE 456/556 Sustainable Water Resources Development, ENVE 322 Fundamentals of Environmental Engineering, CE518 Groundwater Modeling, and I will be developing a new 600-level course on Imaging Techniques for Environmental and Biological Systems.
One of the courses you teach is ENVE 456/556 Sustainable Water Resources Development. What is this course about and how does it reflect your broader interests beyond the physics and chemistry of groundwater flow?
Some of the current concerns in the field of Environmental Engineering include the contamination of aquatic environments by pesticides and fertilizers from agricultural runoff, by oils and particulate matter via stormwater runoff from urban streets, and by atmospheric deposition of acids. An additional area of concern is contamination of groundwater, particularly by hazardous waste products that render the water unsuitable for human consumption and use. My course is really aimed at instilling a sense of environmental responsibility in the graduating engineers regarding these issues. The course incorporates a number of guest lecturers that provide real-life examples of sustainable water development and engineering.
I have worked in such diverse fields as Soil Science/Hydrology, Experimental Geophysics, Hydrogeology, and now am back in Environmental Engineering. This class is my modest attempt at increasing awareness among engineering students of water related issues and promoting respect for our natural environment.
What types of students are working with you on your research projects right now?
Earlier, I mentioned two Ph.D. students, Mark Porter and Danielle Jansik. I also have an M.S. student, Rebecca Weaver, working on groundwater management in the Umatilla Basin. In the last couple of years, I’ve also been enjoying working with undergraduate and high school students both at OSU and at the Advanced Photon Source at Argonne National Lab in Chicago. This past summer I supervised a couple of OSU SBI Undergraduate Interns.
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