Stay Connected
Dr. Christopher Liner, Department Chair
Email: liner@uark.edu
340 N. Campus Drive
216 Gearhart Hall
University of Arkansas
Fayetteville, AR 72701
P 479-575-3355
F 479-575-3469
E-mail: lmilliga@uark.edu
Research
| Click on any title below for more information. | |
| UA GEOS Thesis Library Inventory (updated 12/21/2017) | |
 |
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
|
  |
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.
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.
|
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
Trace Element and Radiogenic Isotope Lab
Trace element and heavy isotope analytical facility equipped for both solution and laser ablation analysis.
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
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
(under construction)
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.
