Research

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UA GEOS Thesis Library Inventory (updated 9/15/2016)
 GIS
The Department of Geosciences has a strong research emphasis in geoinformatics (geospatial science and technology) with five departmental faculty (Aly, Cothren, Limp, Shi, Tullis) specifically focused on this research area - along with collaborators across campus and at other institutions. Specific areas currently under active research include:
- Integration of synthetic aperture radar Interferometry (InSAR), GPS and GIS to assess, monitor, and model geothermal processes and geohazards such as active volcanoes, earthquakes, landslides, and ground subsidence
- High performance geocomputation, spatial data mining, and Internet GIS
- Remote sensing and GIS-assisted decision support in landscape health
- Sensor modeling and 3D extraction from multiple airborne, UAS and satellite sensors
- Provenance interchange in GIS to accelerate the development of and access to high quality geospatial workflows
- Forest biophysical remote sensing based on in situ, optical and LIDAR sources
- Strategies for representation, display analysis and dissemination of complex heritage spatial data from field investigations
- Spatial econometrics and GIS applications in business
- Spatial-temporal analyses of social and business networks
- Applications of terrestrial and airborne 3D reality capture (photogrammetry, laser scanning, etc.)
- Computational strategies for the archival preservation and dissemination of spatial and collateral data
The departmental faculty have close research linkages with the more than one dozen full-time researchers at at the Center for Advanced Spatial Technologies (CAST) and utilize the extensive field and laboratory research instrumentation and hardware software capabilities of that center.  Faculty research is also closely linked with the U of A High-Performance Computing center. The Geosciences geoinformatics faculty have a strong record of extra-mural research with more than $15.8M in research funding awarded over the last  five years (2010-2015) from sources including NSF, NASA, USGS, DOD, DOJ, DHS, DOI, state agencies and others. Representative recent and current projects include NSF 919870, 1321443, 1519660, 1416509.NPS JACS-2013, JACS-2015, NASA NNH09ZDA001N-SAP, USGS AmericaView , NIH 1R21CA182874-01
GEOP-1     GEOP-2
Recent research topics related to petroleum include outcrop, wireline and 3D seismic integration to understand local and regional stratigraphy and structure. We have particular interest in carbonate reservoirs represented by the Mississippian Boone and St. Joe exposed in NW Arkansas and drilled as unconventional oil reservoirs in NE Oklahoma and SE Kansas. Related topics are seismic expression of paleokarst, occurrence and origin of chert within carbonates, and quantitative interpretation of seismic amplitude and attribute data.
We undertake fundamental and applied research with multichannel seismic, conductivity and ground-penetrating radar equipment. Problems of interest range from shallow mapping of geological formation contacts and faults, to environmental studies for subsurface objects or contaminating fluids. The methods are also relevant to geomorphology and archeology.
We are interested in the development and application of new surface wave techniques. Dispersive surface waves are routinely used to estimate the subsurface shear-wave velocity distribution, at all length scales. In the well-known Spatial Autocorrelation (SPAC) method, dispersion information is gained from the correlation of seismic noise signals recorded on the vertical (or radial) components. Our research includes the cross-correlation between radial and vertical components of the wavefield in a spatial cross-correlation method that is an adaptation of SPAC. The addition of cross-correlation information increases the resolution and robustness of the phase velocity dispersion information.
Our research interests in this field include the application of magnetic, gravity, and seismic techniques to investigate the geology and tectonics of the Pacific Northwest. The volcanic bedrock that underlies many of the basins in this region is well suited for imaging by potential field methods. Vegetation, recent deposits, and water conceal hazardous faults making surface mapping challenging. Anomalies in the Earths gravity and magnetic fields, caused by volcanic bedrock offsets, can be easily imaged using potential field techniques. We use these data from high-resolution geophysical surveys to map and characterize known and undiscovered faults. When combined with traditional surface geologic mapping and structural modeling, these geophysical results help delineate three-dimensional structure. This provides useful information to assess ground motion during earthquakes along with application to groundwater and geothermal energy resource modeling.

 Dendrochronology and Climatology
The Tree-Ring Laboratory (TRL) was established in 1979 and concentrates on the development of exactly-dated annual ring-width chronologies from ancient forests worldwide. Tree-ring chronologies are based on small core samples extracted non-destructively from living trees and cross-sections cut from dead logs. They provide unique archives of environmental history and have many inter-disciplinary applications. Undergraduate and graduate students can earn a Geography B.A. or M.A. with an emphasis on Tree Ring Research.
We specialize in the reconstruction of past climate and stream flow, the socioeconomic impacts of past climatic extremes, the dating of historic structures, and the identification and mapping of ancient forests. We conduct research in the southeastern United States, the southern Great Plains, California, Mexico, and southern Africa. The TRL is active in the conservation of ancient forests, and has assisted the preservation of ancient forest remnants in the cypress-tupelo forests of the South, the oak-hickory forests of the central United States, the blue oak woodlands of California, and the conifer forests of Mexico. The TRL helped establish the Ancient Cross Timbers Consortium which unites universities, federal and state agencies, conservation organizations, and private landowners for research, education, and conservation efforts in these widespread ancient forest remnants still found on the margins of the southern Great Plains.

 

 

The Savoy Experimental Watershed (SEW) is a collaborative Research Site for the Study of Animal Waste Management in Mantled Karst Terrains. The main goal of (SEW) is to establish and maintain a long-term research site for comprehensive, multi-disciplinary research of animal waste impacts on surface and subsurface water quality and hydrogeology.

Arkansas Surface Water Mapping Program (ASWaMP)

- Side-scan Sonar Imaging of Beaver Reservoir, NW Arkansas
- Sedimentation in Beaver Reservoir, NW Arkansas
- Bathymetry, Sedimentation, Water Quality of Lake Fayetteville, Fayetteville, AR
- Historic Bathymetry of Lake Sequoyah, Fayetteville, AR
- Processes of Shore Line Change at Yellowstone Lake, Yellowstone National Park, WY
- Impacts of Highway Engineering on the Shore Zone of Yellowstone Lake, WY
- High-Resolution Mapping of Lake Fort Smith, Arkansas (pending)
- Sedimentation in Lake Taneycomo, Missouri (pending)
- High-Resolution Bathymetry and Sediment Mapping of Fremont Lake, WY (pending)

Arkansas Water Resources Research

- Groundwater Hydrology of the Grand Prairie, Arkansas
- Hydrogeology of the Savoy Experimental Watershed, Arkansas
- Hydrogeology of Mantled Karst, Ozark Plateaus, Arkansas
 Mississipian Section

 

GEOS 4053 Geomorphology - students work on field projects on the Red River floodplain in southwestern Arkansas.  They examine aerial photographs to study the geomorphology and cores taken from a variety of fluival environments, natural levees, channel-fill point bars, backswamps, and crevasse splays to interpret the soil development and sedimentation.  Each student writes a research report with their interpretations. Geomorphology is taught by Dr. Margaret Guccione, who has published many papers and presented her work at professional meetings around the world. 
GEOS 4253 Petroleum Geology - students learn the basics of exploration for oil and gas, including well log analysis, seismic interpretation, and use the software used by many in the industry.  Taught by Dr. Doy Zachry.
GEOS 560V Exploration Methods - a special problems course for grad students that includes more in-depth studies and research into oil and gas exploration.  Taught by Dr. Christopher Liner

 

 Petra's Treasury

 

The University of Arkansas PETRA PROJECT is an ongoing project established in 1990 to assess and record various aspects of landscape change in the classical period city of Petra, Jordan.  Aspects include deterioration influences and rates for limestone and sandstone architecture and rock, cultural heritage management issues for the UNESCO World Heritage site and region, urban planning and local Bedouin studies (Bdoul) in Wadi Musa and Umm Sayhoun, and prehistoric and historic environmental landscape change and influences. University of Arkansas graduate students in the Department of Geosciences and the Environmental Dynamics Program participate in various components of the research project, completing theses and dissertations while conducting fieldwork in Petra and the region.
Now after more than 100 million voters have chosen Petra, Jordan as one of the NEW SEVEN WONDERS of the WORLD, it is imperative that this ongoing research project continue as tourism will dramatically increase, infrastructure will become increasingly strained, and the environment in and around Petra will be impacted drastically. This magical yet sensitive site needs increased research so that its stewardship may continue now and in the future.
Evidence indicates that Petra has been occupied since 3000 BCE, and Greek, Roman and Aramaic records mention Nabataean culture in the region since 500BCE. However, it was the sacredness of Mount Hor (or Jebel Haroun) that deir closeupbrought early notoriety to Petra since it was the reputed burial site of Aaron, the brother of Moses. Many believe that Bedouins have occupied and roamed the region long before Moses’ arrival about 1250BCE, or later when Rome annexed the region in 104AD as Felix Arabia Petraea. This hidden Valley passed into legend with the passage of time and remained unknown until the 19th Century, when in 1812, Johann Burckhardt visited the Valley surreptitiously dressed as a Bedouin traveler wishing to sacrifice a lamb at the mountaintop tomb of Aaron. Since the earliest days of the Nabataean civilization, followed by Roman invaders and partners, then raided by Crusaders, defended by Sa’aladin, the hidden valley of Petra was unknown to outsiders. Researchers did not ‘discover’ Petra until the early 1900s, when historians, geographers and archaeologists extensively studied and surveyed Petra and its monuments, tombs, buildings, tells, and temples.
Petra is a crescent-shaped Valley confined by high fault-bound sandstone walls that may have been the home to more that 50,000 people 2,000 years ago with more than 500 known tombs, structures and monuments. The unique architecture of Petra represents an interesting melding of indigenous Nabataean, Hellenistic, Roman styles, uses and decoration. Since sandstone represents a common building material and a dominant landscape component across the region and its structures have a known exposure (roughhly 2,000 years old), Petra represents an ideal outdoor laboratory for sandstone deterioration research since (i) the structures (ie tombs, temples) were carved during known periods, (ii) many of the structures were hewn and have not been moved, (iii) restoration has been recorded and/or is visible, (iv) the sandstone has been extensively studied and is relatively consistent in lithology. Petra’s two primary formations are the Cambrian Umm Ishrin and Cambrio-Ordivician Disi sandstones and represent one of the oldest, most widespread and relatively unaltered sandstones units on Earth.
Although the PETRA PROJECT was initiated in 1990 with a focus on architectural deterioration and stone decay, over the years it has expanded to included aspects of the cultural and social landscape, and cultural heritage management. Originally the research looked at climatic influences on rock weathering, however it became apparent that visitors were accelerating the rock breakdown faster than nature had in 2,000 years -- humans and their effects were added to the investigation of the architecture and landscape. At first, variations in sandstone lithology were correlated to environmental variables like aspect, moisture, sunlight (insolation), slope, and biotic coverage (lichens, plants). Later, other variables were studied including respiration and humidity from tourists, and visitor frequency across the Valley. Various research components follow that have been investigated so far:
This study examined 26 variables related to surface recession that created a statistical matrix of nearly 14,000 data points creating the largest sandstone weathering data set known. 526 baseline recession measurements were taken across the Theater (in a stratified random scheme) and related to 26 variables that included aspect (220 degrees of coverage), insolation (mjoule/m2/yr), matrix lithologic constituents (calcium, iron, manganese, silica), clast lithologic components (siliceous, calcareous), lichen genera and coverage, and daily & annual shadowfall.
Sandstone matrix constituents of iron and silica were found to decrease overall sandstone weatherability, while calcium matrix components were found to increase deterioration in areas that receive more than 5500 megajoules/square meter/year of solar radiation — a typical southern aspect in mid-latitude, arid regions. Moreover, when iron matrix concentrations exceed 4-5% (by weight), original stonemason dressing marks are still clearly evident, indicating a nearly unweathered state in 2,000 years. Surface recession rates for sandstone in the Roman Theater were determined to range from 15 70mm per millennium on horizontal surfaces to 10 20 mm/millennium on vertical surfaces.
While the Theater study explains significant sandstone weathering relationships and hierarchies, it created more questions and Petra’s monuments and quarries afforded new research opportunities. So, quarries and monuments across Petra - like the Blocks of Djinn - were studied for surface recession relationships to aspect. Insolation was found to have the greatest effect on weathering on southwestern and southeastern aspects (and not southern faces as is often discussed), indicating that insolation may be most influential in sandstone weathering when in tandem with increased wetting-drying and/or heating-cooling cycles.
As tourism grew in Petra and the, studies into anthropogenic influences on sandstone deterioration are warranted and the Khazneh (Treasury) represents the perfect sites due to its popularity. Over a  five-year study with Arkansas graduate students Mick Frus, Mohammed Salem, and Chris Angel, it was found that interior surfaces have dramatically receded due to visitor touching, leaning and rubbing, as much as 40mm in less than 50-100 years (period of increased tourism). This indicates that a 4 by 3 meter wall area has lost a volume of sandstone of approximately one half cubic meter in these 100 years from 0.5 to 2m above the floor indicating surface recession from human contact .
In the Summer of 2003, Mo Salem, a graduate student in Geography and Dr. Paradise recorded and assessed each visitor that entered and exited Petra in the hopes of determining tourist movement through the Park.  Recording each tourist that entered Petra through the main gate (Bab as-Siq), to then pass the Khazneh and Theater, they mapped the tourists' movements throughout the valley and their use of related infrastructure. Their exit was also recorded as to where they walked, why, and how quickly. This extensive study is invaluable in cultural site management -- determining what resources they use and when, where they are in the Valley and how fast they move, how quickly they leave and by what route is fundamental in management research.  Maps were then created for each portion of the Valley and City during various times of the day to determine how many visitors are where and where.  This research and mapping project has been studied and utilized in Petra's new Park Management Plan.
Over the Summer of 2007, graduate student Chris Angel and Dr. Paradise digitally mapped the Bdoul Village of Umm Sayhoun using satellite imaging, flyover photography, ground-level imagery, GIS and computer cartography.  Since the village was created in the early 1980s, it is a unique opportunity to assess a new city of 2000 residents since its creation.  Aspects of urban morphology, materials and construction, perception of space, and topophilia are addressed. The Bdoul clan of Bedouins were forced to relocate in 1984-1985 when the new designation of the UNESCO title as a World Heritage Site was implemented on the Valley of Petra and its surrounding area -- so how does a previously semi-nomadic clan create a permanent city?   This important baseline study has strong implications now that Petra has been designated as the one the NEW SEVEN WONDERS of the WORLD.
Weathering studies have shown that wetting and drying cycles accelerate deterioration, however little is known about human-induced moisture changes affecting deterioration of stone architecture; humans contribute to ambient humidity through respiration, transpiration, perspiration. So, comprehensive interior and exterior humidity measurements were made in Petra’s most celebrated structures, al-Khazneh and Urn Tombs in conjunction with data on visitor numbers and frequency over a ten-year period (1998-2008). This study found that small visitor groups entering the tomb chambers caused interior relative humidity increases of 5% to 15%. Statistical correlations of determination (r2) explained that correlations increased dramatically when the tourist numbers were compared to relative humidity in the chambers both simultaneously (r2=0.007, 0.136), and to fifteen minute delays (r2=0.707, 0.895). These relationships indicate that it takes ten to twenty minutes for human respiration and transpiration to contribute to relative humidity in chambers of this volume (2,000-3,600m3) – an important finding regarding the possible anthropogenic acceleration of architectural deterioration.  Further research in these popularly visited tombs will continue, in addition to more chamber humidity measurements across Petra.
The popular, touristic, and scholarly maps of Petra represent the current structure footprints of Petra and not the contemporaneous structure and monument locations and footprints.  For instance, Byzantine, Roman and Nabataean structures are cartographically represented alongside each other.  So however similar in space, there are nearly unrelated in time.  So the Arkansas team of cartographers, GIS technicians, and geographers including graduate students Chris Angel and Daniel Snyder, are currently taking advanced GPS readings to merge with ground-level structural measurements, isohypsometry (DEMs), and historic data to create an innovative time series of Petra's urban morphology over time from the Neolithic period of Umm al-Biyara, to Nabataean and Roman city, to the Byzantine and Crusader sites, to the new locations of Petra's new structures and infrastructure.
As a part of a large collaborative project with UNESCO, the American Center of Oriental Research (ACOR), the Petra National Trust (PNT), the Jordanian Department of Antiquities (DofA), and the Petra Development & Tourism Regional Agency (PDTRA), the University of Arkansas is working to facilitate the creation of a new, extensive geographic information system (GIS) that will combine elements and layers of elevation, hydrography, imagery, infrastructure and energy, geology and soils, demographics, structures, etc.  After our 2011 field season in Petra, this year represents the first year to merge and meld these layers and data planes into one cohesive and up-to-date GIS, all in the hopes of creating a strong and effective management and sustainability tool for the Valley and local environment - inshallah.
Research since 2010 has identified a number of features (i.e. bedrock scoring, perched alluvium, absent architectural features) that indicate the city center of Petra may have been inundated by catastrophic flood(s).  Extensive flood deposits have been excavated and identified in and alongside the Colonnaded Street Shops indicating flood surges may have reached 3-5m in height.  Roman-Byzantine coins found below and above the paleo-flood alluvium dates the possible disaster to the 4th century, indicating that it may have followed the earthquake swarms of the 3-4 century which have razed the effective Roman-Nabatean flood abatement structures such as dams, weirs and cisterns.  A flood of this magnitude would have abruptly halted all operations in the city for months to years, and may have facilitated the downfall of Petra’s Golden Age.
Research since the 1990s has continually divulged relationships between solar marker days (solstice, equinox) and the alignment and orientation of Petra’s most prominent structures and monuments.  Many of Petra’s tombs and buildings are displaying such relationships with inner-chamber illumination and penetration on these marker days (only), and/or with structural alignments with sunset and sunrise paths intersecting at prominent horizon sites such as Jebel Haroun, Umm al-Biyara, and true west and east pathways.  Important structures, such as the Royal Tombs, show such solar-architectural alignments.  This ongoing landmark research is changing the way we look at Petra’s urban morphology, architecture, and religion/cosmology.

 

 

 

 

 

Water Resources/Watershed Science

Arkansas Surface Water Mapping Program (ASWaMP)

- Side-scan Sonar Imaging of Beaver Reservoir, NW Arkansas
- Sedimentation in Beaver Reservoir, NW Arkansas
- Bathymetry, Sedimentation, Water Quality of Lake Fayetteville, Fayetteville, AR
- Historic Bathymetry of Lake Sequoyah, Fayetteville, AR
- Processes of Shore Line Change at Yellowstone Lake, Yellowstone National Park, WY
- Impacts of Highway Engineering on the Shore Zone of Yellowstone Lake, WY
- High-Resolution Mapping of Lake Fort Smith, Arkansas (pending)
- Sedimentation in Lake Taneycomo, Missouri (pending)
- High-Resolution Bathymetry and Sediment Mapping of Fremont Lake, WY (pending)
Arkansas Water Resources Research
- Groundwater Hydrology of the Grand Prairie, Arkansas
- Hyrdogeology of the Savoy Experimental Watershed, Arkansas
- Hydrogeology of Mantled Karst, Ozark Plateaus, Arkansas

 

 Karkevagge

 

Professor John Dixon's research interests lie primarily in the area of Critical Zone processes and landscape evolution.  He is interested in the nature and rates of chemical weathering in Arctic and alpine environments.  Since 1990 he and his research teams have worked in Scandinavia, especially in Swdish and Norwegian Lapland, as well as in the Jotunheimen of southern Norway.  In addition he is also interested in regolith processes in arid environments, especially in the genesis and environmental significance of relict soils.Ongoing research in Surficial Processes and Quaternary Studies at the Department of Geosciences:Origin of a Pleistocene Mississippi River splay through Marianna Gap in Crowleys Ridge.



 

 

 

With expertise in the earth sciences, architecture, building materials, cartography, and natural hazards, we are increasingly requested by foreign agencies to assist in the evaluation of seismic risk (and tsunami and volcanic-related quake activity), and regional and/or community policies. As this unique research agenda develops it has become clear that cultural differences and perceptions in risk assessment are dramatically influential. As a result, our team at the University of Arkansas’ Geosciences Department has started to investigate these similarities and differences by interviewing and surveying hundreds of individuals in high-risk communities.

Natural Hazards/Active Tectonics

Natural Hazards and Risk Perception (US, Mediterranean, North Africa, Middle East)
Dr. Tom Paradise has an extensive background in hazards perception and disaster policy and preparedness across the US, Mediterranean, North Africa and the Middle East. Since the 1990s while living, teaching and researching in Hawaii and the Middle East, Dr. Paradise has managed research and overseen scores of students conducting similar research on natural hazards, risk perception, hazards assessment and mitigation.  His current hazards research focus examines aspects of perception, hazards, natural disaster across religious communities (Muslim, Christian, Jewish)  How we modify our perception of natural hazards based upon faith and religion is the focus of his work and that of his graduate student team at the University of Arkansas.
With expertise in the earth sciences, architecture, building materials, cartography, and natural hazards, Dr. Tom Paradise is increasingly requested by foreign agencies to assist in the evaluation of seismic risk (and tsunami and volcanic-related quake activity), and regional and/or community policies. As this unique research agenda develops it has become clear that cultural differences and perceptions in risk assessment are dramatically influential. As a result, his team at the University of Arkansas’ Geosciences Department has started to investigate these similarities and differences by interviewing and surveying hundreds of individuals in high-risk communities.  300 people have been interviewed in Agadir, Morocco (2003), then 400 respondents in Messina on Sicily (2005), and 400 quake survivors in Northern Pakistan (2008). This extensive ongoing research project is being conducted in the hopes of establishing a huge network of related surveys and interviews to help understand why some communities prepare and plan for imminent disaster and others do not.
Some related recent publications by Paradise include:
Paradise, T.R. 2008. "Islam and Earthquakes: risk perception and the Qur'an". Journal of Islamic Law & Culture v10: 2, 213-229, doi: 10.1080/15288170802285447 
Paradise, T.R. 2007. "Earthquake, Islam & risk perception -- case studies from Morocco". Studies in Disasters & Gender, Northumbria University: 29pp
Paradise, T.R. 2006. “Perception of Earthquake risk in Agadir, Morocco: a case study from a Muslim community", in Environmental Hazards vol 6: 3, 167-180, doi: 10.1016/j.hazards.2006.06.002
Paradise, T.R. 2006. “Seismic Risk perception in the Muslim community of Agadir, Morocco”. in Journal of North African Studies vol 1, 3: 243-262.
Recent related research topics, theses, and dissertations include:
­ GIS analysis of environmental perception and aquifer mining across the Madaba Plain, Jordan (PhD 2008)
­ Post-Katrina Hurricane Risk Perception and Comparative Demographic Assessment, New Orleans (MA 2008)
­ Seismic Hazard and Risk Perception in Messina, Sicily (MA 2007)
­ Water resource and depletion hazard perception among rice farmers on the Arkansas Delta (MA 2007)
­ Assessment of flood hazard from Hurricane Jeanne on Hispaniola using GIS and remote sensing (MA 2006) 
­ Analysis of antecedent American terrorist activities using spatial visualization & GIS (MA 2006)
­ Seismic risk perception and architectural safety in Agadir, Morocco: 40 years after the great quake (MA 2005)
­ Safety from the Storm: risk perception analysis and safety in Tornado Alley (MA 2004)
­ Arkansas tornado risk perception and reality using GIS (MA, 2003)
­ Environmental degradation perception and ‘eco’-tourism in Wadi Rum, Jordan (slated MA 2009)
­ Before and after Hurricane Ike: perception of risk in Galveston, Texas (slated MA 2009)

 

 

 

Cave and Karst Systems

An understanding of the interplay of hydrology and biogeochemical processes that control transport and processing of nutrients in karst watersheds is critical to the design of sustainable land-use practices over karst terrains. Our understanding of the processes operating in karst systems, however, lags considerably behind that of other aquatic ecosystems (such as marine, riverine, wetlands, and granular aquifers). The availability of dissolved organic matter, a strong control in biogeochemical cycling of nutrients within the karst soil system, is easily altered by agricultural, wastewater treatment outfalls, septic systems, and other activities in the karst watersheds. Whereas karst ground-water movement has recently received focused study, controls on the carbon availability and movement, particularly the DIC-DOC-CO2 (g) dynamics have received little attention. Carbon is the basic substrate which must be available for processing nutrients--and specifically nitrate. Basic geochemical monitoring is being conducted which includes continuous pCO2 measurement and isotopic characterization of DIC and DOC behavior moving through the karst-soil system. These data are facilitating source identification and delineation of the complex interaction between water quality and nutrient cycling in karst. This project will establish controls on the effect of carbon cycling and local hydrology on the effective processing of nutrients in mantled-karst watersheds of the Ozarks.
Currently we are working in a cave system in Madison County to help understand the interplay of climate, hydrology, and nutrient processing.  Sampling infrastructure design aims at collection of soil gas, soil water, ground water at various points moving along flow paths including caves, and cave CO2.  The data set being accrued will help draw direct correlation between the surface conditions and cave responses and enable elucidation of controls on nutrient processing.  Data also will allow for characterization of climate effects with improved understanding of CO2-speleothem dynamics and the development of the archived climate records of the cave system. 
Researchers Dr. Phillip D. Hays pdhays@uark.edu USGS Liaison
  Dr. J Van Brahana brahana@uark.edu  
  Erik Pollock    epolloc@uark.edu  

Use of Phosphate-Oxygen Isotope Ratios as a Tracer for Sources and Cycling of Phosphorus in the Illinois River in AR and OK
Excess phosphorus in streams causes eutrophication, which diminishes an aquatic system's capacity for supporting a healthy and normal ecosystem and diverse aquatic communities, water supply needs, and aesthetic and recreational value.  Phosphorus concentrations and sources are a significant regional concern at the Upper Illinois River Watershed in northwestern Arkansas and northeastern Oklahoma, as well as for streams across the Nation.   Recently developed isotopic methods enable determination of oxygen isotope composition of soluble reactive phosphate (SRP), potentially allowing sources of phosphates in aquatic systems to be identified.  For this method, phosphate is chelated into a magnesium hydroxide precipitate, reprecipitated as cerium phosphate, and then dissolved and precipitated as silver phosphate which works well for isotopic analysis.  We are interested in phosphate isotopic composition because oxygen isotopic ratios reflect those of input sources.  As organic phosphorus is oxidized, oxygen is derived largely from water, and d18OP reflects the d18O of local water.  Isotopic fractionation of dissolved inorganic phosphate can occur, but only as a result of enzyme-mediated biologic reactions.  The expected equilibrium of
d18OP has been empirically derived for phosphates produced by microbial cultures and the temperature-dependent fractionation may add insight to the amount of SRP cycling occurring in the river.  If PO4 demand is low relative to input, the d18OP will reflect the isotopic signatures of the input sources, allowing sources to be identified and transport of PO4 to be characterized.   Input sources such as wastewater effluent (29‰), poultry litter extract (20‰) and commercial fertilizer extract (18‰) have been sampled and analyzed.  Water samples from the Illinois River are now being sampled.  This method has not been not previously been applied in the central United States, but we hope results will give us better understanding of the sources, transport, and cycling of phosphorus in the Illinois River and similarly impacted streams in the region.

 

 

 

The University of Arkansas Stable Isotope Lab was established in 2000 with funds from the National Science Foundation and the State of Arkansas. We have three isotope ratio mass spectrometers (one Delta XP and two Delta Plus IRMS systems) for stable isotope analysis allowing the capability to measure the C, N, O, or H isotope composition of trace gasses, solid, and liquid samples. To complement our compound-specific IRMS (Isotope Ratio Mass Spectrometry) work, we have an Agilent GC with a Quadrupole mass spectrometer for compound identification and quantification.