Advising & Program Requirements
Original research is a key element of the graduate school experience. Through this experience, a students learns how to define a problem, design an investigation to study the problem, conduct the investigation, analyze and interpret the results, and defend their work in a public forum and in a written document.
Below are some examples of ongoing or recently completed research projects being conducted by graduate students in the department.
Students: Jonathan Love, Jarek Trela, Jessie Ackerman, and Randi Liescheidt
Advisors: Steve Van der Hoven and Bill Perry (School of
Biological Sciences)
Surface
water and groundwater in the U.S. and around the world have been
negatively impacted by increased nutrient loads due to the application
of agricultural fertilizers and discharge of treated waste water. One
strategy for reducing the nutrient loads is to pass agricultural
drainage and treated waste water through constructed wetlands prior to
discharge into streams or rivers. Most research in this field focuses
on removal processes occurring in the wetlands. Our focus is to
characterize the role of groundwater seeping in to and out of the
wetlands.
We are currently collaborating on research with The Nature Conservancy (TNC) at their Franklin Demonstration Farm in Lexington, IL. Among the numerous conservation practices being explored at the Demo Farm (see the 2009 Annual Report) are a series of constructed wetlands receiving subsurface tile drainage. Tile drainage usually discharges directly into the nearest stream, however, biogeochemical processes occurring in constructed wetlands can remove the nutrients in tile water. Specific goals of this project are to quantify groundwater interactions with each wetland complex and to quantify nitrogen cycling processes (denitrification, nitrification, and uptake) in each wetland. Water and nitrogen mass balances are being constructed through the use of injected tracer tests and measuring the natural nitrogen isotopic composition dissolved and solid nitrogen species.
In
another project, we are looking at the removal of nitrogen and
phosphorus from treated waste water seeping out of a constructed wetland
operated by the Bloomington Normal Water Reclamation District.
Preliminary data indicate that >90% of the nitrogen and 100% of the
phosphorus is removed in the subsurface. A 3-dimensional array of
monitoring wells has been installed around and beneath the wetlands, and
groundwater flow model will be used quantify the flux of water seeping
out of the wetlands. In addition to hydraulic head, the model will
be calibrated using the conservative tracer chloride. Chloride
concentrations in the waste water are an order of magnitude greater than
the natural site groundwater, and this difference can be used to
determine mixing ratios of groundwater and waste water as well as travel
times in and hydraulic conductivity of the aquifer underlying the
wetland.
Recent presentations and publications include:
Trela, J., Van der Hoven, S.J. and Love, J.W., 2009, Quantifying the effects of groundwater on nitrogen cycling in constructed wetlands receiving agricultural tile drainage, Geological Society of America Annual Meeting, Abstracts with Programs, Vol. 41, No. 7, p. 669.
Love, J.W., Van der Hoven, S.J. and Trela, J., 2010, Using Natural N Isotopes to Identify Nitrate Removal Mechanisms in Constructed Wetlands Receiving Agricultural Tile Drainage, Emiquon Science 2010: Restoration Ecology, Theory and Policy.
Van der Hoven, S.J., Trela, J., and Love, J.W., manuscript in preparation for the journal Wetlands, The Importance of Quantifying Groundwater Inflow and Outflow when Calculating N Mass Loss in Constructed Wetlands.
Student: Eric Dieck
Advisors: Steve Van der Hoven
The
Mahomet Aquifer is a major source of water in central Illinois.
The aquifer is confined by 200+ feet of fine-grained glacial till,
however previous noble gas evidence indicates that significant recharge
to the aquifer is occurring through the confining layer (Van der Hoven
et al., 2005). This evidence includes loss of noble gases dissolved in
the aquifer due to the formation of pockets of methane (known as drift
gas) in the confining unit overlying the aquifer. Methane is
generated by decomposition of organic matter in buried soil horizons.
Initially methane remains dissolved in the water, but as methane builds
the dissolved pressure can exceeds the hydrostatic pressure resulting in
degassing. This degassing also removes some of the noble gases
dissolved in groundwater when it first recharges. We have
extensive data on the noble gas concentrations in drift gas as well as
dissolved in groundwater.
Ongoing research seeks to create a model of the formation of drift gas pockets, and thereby constrain the amount of water recharging the Mahomet Aquifer through the confining layer. This modeling will the exchange of noble gases between the water moving through the confining layer and the drift gas in this layer using the model NUFT. Graduate student Eric Dieck will be interning at Lawrence Livermore National Laboratory (LLNL) in California during the summer of 2010. NUFT was developed at LLNL, and Eric will be working with one of the world's experts on multi-phase modeling to simulate creation of drift gas pockets and flow rates through the confining layer.
Recent presentations and publications include:
Van der Hoven, S.J., Wright, R.E. , Carstens, D.A., and Hackley, K.C., 2005, Radiogenic helium 4 as a conservative tracer in buried-valley aquifers, Water Resources Research, 41, W11414, doi: 10.1029/2004WR003857.
Van der Hoven, S.J, Moran, J.E., and Sheldon, A.L., 2008, Field and Laboratory Investigations of Rapid Accumulation of 4He in Groundwater: Applications for Dating Young Groundwater, American Geophysical Union Fall Meeting.
Student: Tim Sickbert
Advisor: Eric Peterson
Tim conducted research tested the hypothesis that velocity differences perpendicular to the direction of stream flow could cause pressure differences that result in surface water/ground water exchange. In his own words, "Can flowing water in a stream suck water out of the ground?"
Tim formulated his question on Bernoulli's conservation of energy equation, which states that the energy of moving water is divided into gravitational and velocity components. At any point in a stream (i.e. the inside and outside of a meander), the total energy is the same. However, if the velocity components differ, then the gravitational (or pressure head) components must differ in order to conserve energy. So, the velocity differences may cause pressure head differences which may cause the flow of water across the stream bed.
To address his question, Tim installed nested peizometers in the stream bed and the stream banks, and has equipped them with pressure transducers. Tim's data indicate that the velocity differential observed in the stream may be to low to produce a measurable pressure difference. The work has provided an initial study from which to build, including the possibility of numerical modeling of the exchange. While Tim's work focused on two dimensions, future students will focus on three dimensions. Tim's research is funded by the Geological Society of America and Sigma Xi.
Advisor: Eric Peterson
In karst terrain, ground water is especially vulnerable to contamination from land-use activities because of the direct and rapid hydrologic link between surface water and ground water. When impacted surface water enters swallet or storm-water runoff flows into a sinkhole, contaminants enter the ground water directly. The direct connection to the ground water eliminates the possibility of soil filtration, degradation, and sorption of the contaminant.
Karst aquifers are vulnerable to surface water impact. Assessing the risks to a karst system requires knowledge of the sources as well as the pathways the water flows. Unlike traditional porous media aquifers, karst systems are complex due to flow along bedding planes, fractures, and conduits. Understanding the flow with karst aquifers is an important step in preserving the integrity of the system, including the biological habitat.
Julie's research focuses on identifying the various sources and pathways for the water of moving through the Horn Hollow system in Carter Caves State Park in Kentucky. Julie has collected some preliminary data and is in her initial stages of forming her hypothesis. Major ion samples were collected from 15 locations within the Horn Hollow Valley at baseline flow conditions and after a precipitation event. Fluxes of Ca2+ and Mg2+ were observed as the karst waters entered and exited the subsurface. Water types are dominantly Ca-HCO3 with two distinct subgroups based on major ion chemistry. The upstream portion of the system contains aggressive waters (Ca-Mg-HCO3-SO4) that are under-saturated with respect to Ca2+. Less aggressive waters (Ca-HCO3) are present in the downstream portion of the system, which includes Laurel Cave and Cave Branch, and are over-saturated with respect to Ca2+. The increase in saturation with respect to Ca2+ through the system may be the result of limestone dissolution, a change in concentration of CO2, or a change in temperatures as waters flow through the system. Mass flux calculations of Ca2+ and Mg2+ will be performed to determine dissolution rates within the upper Horn Hollow system.
Advisors: Dave Malone and Eric Peterson
The Ticona Channel is a part of the pre-glacial drainage system in Illinois that has been buried by glacial sediments. Coarse-grained sediments fill the bottom of the valley, forming a potentially valuable aquifer for nearby communities. The objective of Bryce's research is to define the geometry of the channel, map the sediments that fill the channel, measure aquifer properties of the coarse-grained sediments, and examine the interaction of channel sediments with the nearby Vermillion River.
Bryce employed a wide variety of techniques to conduct his investigation. These techniques include s-wave geophysics, borehole geologic and geophysical logging, surface geologic mapping, and groundwater modeling.
Bryce's research was funded by the Illinois Board of Higher Education through the Illinois State Geological Survey (ISGS), and by a United States Geological Survey EDMAP grant. His research is a part of a larger collaboration between the department and the ISGS. Over the past two years, numerous undergraduate and graduate students have collaborated with ISGS scientists on geologic, geophysical, and geochemical investigations of buried valley aquifers throughout Illinois. Bryce has submitted the results of his research for publication, and is currently pursuing a Ph.D. at Northern Illinois University.
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