Gregg R. Davidson

Gregg R. Davidson
University of Mississippi | UM · Department of Geology and Geological Engineering

PhD

About

46
Publications
5,669
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
697
Citations
Citations since 2017
17 Research Items
236 Citations
2017201820192020202120222023010203040
2017201820192020202120222023010203040
2017201820192020202120222023010203040
2017201820192020202120222023010203040

Publications

Publications (46)
Conference Paper
University of Mississippi Field Station (UMFS) is 740 acres of natural research and educational facility located 18 km northwest of the University of Mississippi (UM) Oxford Campus MS. Initially, the facility was opened as a fish farm operated by Herbert Kohn Corporation and UM acquired the facility later on in 1985. Hydrologically, the UMFS is loc...
Conference Paper
University of Mississippi Field Station (UMFS) in Mississippi is a multidisciplinary natural research and educational facility. The Meridian Sand aquifer is underlain by a clay Wilcox group and is the main source of groundwater within the facility. The aquifer varies from artesian to unconfined within a very short distance. Electrical resistivity g...
Article
Full-text available
Heterogeneity in the hyporheic zone or near‐field geology can impart a threshold effect on groundwater‐surface water (GW‐SW) exchange. Variations in the texture of riverbed sediments and lithologic variations in adjacent and underlying geology are examples of common heterogeneities. Hydrologic interaction with these heterogeneities leads to distinc...
Article
Abstract Saturated wetland soils are typically depleted in oxygen due to rapid consumption by biological processes. Fine‐grained sediments limit the vertical flux of oxygenated surface water. In forested wetlands potential exists for advective transport along preferential flow pathways created by decomposing roots or tree remains, resulting in isol...
Conference Paper
Full-text available
Intensive pumping for irrigation in the Delta region of Mississippi has caused long-term depletion of groundwater in the Mississippi River Valley Alluvial Aquifer (MRVAA). An immediate need exists for better understanding of the MRVAA water budget, including quantifying inflows and outflows, and development of management strategies to provide a sus...
Article
The Mississippi River Valley Alluvial Aquifer ranks among the most overdrafted aquifers in the United States due to intensive irrigation. Concern over declining water levels has increased focus on understanding the sources of recharge. Numerous oxbow lakes overlie the aquifer that are often considered hydraulically disconnected from the groundwater...
Data
O’Reilly, A.M., Gratzer*, M.C., and Davidson, G.R., 2019. Sky Lake water level data, 2016-2018, Humphreys County, Mississippi: Lake stage, wetland stage, and groundwater levels in 11 wells. HydroShare, http://www.hydroshare.org/resource/05481f58200b49d4a0f4d542d4e15da1, created 25 August 2019.
Article
Seepage beneath artificial levees is a common concern during flooding events. Risk of levee failure is elevated when piping erodes channels beneath the levee, evidenced by the formation of sand boils where transported sediments discharge. Along the lower Mississippi River, pathways of floodwater beneath the levee vary with surface geology, followin...
Conference Paper
Full-text available
Some streams in northern Mississippi experience extensive precipitation of iron minerals on bottom sediments and plant matter, resulting in diminished photosynthetic production and biological diversity. At two streams, one with visible iron-precipitates and one without, two shallow wells were installed along a groundwater flow path toward each stre...
Article
Full-text available
The edge of regional aquifers can be complex hydrodynamic systems with unique flow dynamics, water quality, and continuity relationships with the main aquifer system. A site near the southwestern margin of the High Plains Aquifer (USA) was investigated to characterize the local hydrogeology and its relationship with the regional aquifer system. Mea...
Article
Short-term studies of wetlands show that wetlands scavenge pollutants, thereby mitigating the pollution of downstream water bodies. However, there are few long-term studies that demonstrate this effect. This study provides a wealth of data demonstrating that there is variable long-term mobility of metals and arsenic in wetland-lake systems. More th...
Article
Full-text available
Sixteen years into the twenty-first century, many are dismayed at the resiliency of skepticism about science in the United States. On wide-ranging subjects, such as vaccinations, genetically modified foods, climate change, evolution, and the age and origin of the Earth and universe, a sizable percentage of the population continues to hold and promo...
Article
Full-text available
Quantifying the effectiveness of erosion control practices in watersheds remains a difficult problem. Determination of recent sediment accumulation rates for lake sediments in agricultural watersheds using radioisotopes, such as lead-210 (210Pb) and cesium-137 (137Cs), is potentially a valuable means of assessing the effectiveness of soil conservat...
Conference Paper
We examined the relationship between inundation and NDVI (a spectrally derived indicator of plant productivity) in a 0.48-km 2 bald cypress stand in Sky Lake, an oxbow lake of the Yazoo River basin (Mississippi). We calculated NDVI from 63 cloud-free Landsat-5 scenes for 2003-2011. Inundation was estimated from daily pressure-transducer measurement...
Article
Identifying and quantifying sources and sinks of CO2 is integral to developing global carbon budgets and effectively modeling climate change. Adsorption of CO2 onto mineral and soil surfaces has generally been regarded as an insignificant sink, though few studies have investigated adsorption on natural materials at temperatures and CO2 concentratio...
Chapter
Full-text available
Flood-control reservoirs designed and built by federal agencies have been extremely effective in reducing the ravages of floods nationwide. Yet some structures are being removed for a variety of reasons, while others are aging rapidly and require either rehabilitation or decommissioning. The focus of the paper is to summarize collaborative research...
Article
Shortly after peak stage of the 2011 Mississippi River flood, water samples were collected from the river, from sand boils near the toe of the levee, and from actively flowing relief wells over a 55 km stretch north of Vicksburg, MS. Two distinct pathways for seepage under the levee were identified based on the elemental composition of water sample...
Article
Full-text available
The effectiveness of erosion control methods is difficult to measure, hampering the development of management practices and preventing accurate assessment of the value of erosion control structures over time. Surface erosion can vary widely over an area, particularly if gully erosion is present, and the use of sediments transported in streams for q...
Article
Full-text available
The Balcones Escarpment of south-central Texas is the eroded topographic expression of an en echelon fault zone where Cretaceous carbonates have been modified by karst processes influenced by structural and stratigraphic controls. While the modern confined Edwards Aquifer flows through cavernous voids at the base of the escarpment, air-filled caves...
Article
Full-text available
Trace element mobility in bald cypress (Taxodium distichum) was investigated for a suite of elements using cores from century-old trees from a wetland in Humphreys County, Mississippi. Element mobility was determined by comparing the dendrochemistry of decadal increments over the life span of a tree, and by comparing increments of the same age coll...
Article
Full-text available
A 100-y geochemical record preserved in the sediments of a Mississippi oxbow lake yields evidence that chemicals entering from agricultural fields are only temporarily sequestered in the riparian fringe prior to active removal and transport to open water. Elevated concentrations of Pb and As, corresponding to peak historical use of lead arsenate pe...
Article
Full-text available
Excerpt Sediments stored in lakes represent a valuable archive that can be used to reveal the erosion history of watersheds. A portion of the soil that is moved down gradient during runoff events is deposited in lakes, and the rate at which sediment accumulates should be proportional to the rate of erosion from the surrounding land. The ability to...
Article
Full-text available
The history of sediment accumulation in an oxbow lake located on the Mississippi alluvial floodplain was reconstructed based on sedimentation rates determined using 14C activities from bulk sediment fractions and from 210Pb and 137Cs measurements. Higher rates of sediment accumulation consistent with frequent flooding when first abandoned 3,800 to...
Article
Full-text available
In the absence of identifiable macrofossils in lacustrine sediments, radiocarbon dating must rely on pollen or bulk sediment fractions. Bulk sediment fractions are not generally preferred because they contain an unknown mixture of organic material of variable age, they may contain dead carbon such as lignite that is difficult to eliminate, and mate...
Article
Full-text available
Picric acid is an explosive historically produced and disposed at the Louisiana Army Ammunition Plant (LAAP) in northern Louisiana. The potential for natural degradation of picric acid was investigated by creating picric-acid slurries with four LAAP sediments of variable composition and monitoring for up to 98 days. The concentrations of picric aci...
Article
Full-text available
Bald cypress (Taxodium distichum) is known to respond to increases in precipitation with increased radial growth even when rooted in continuously saturated sediments where water is not a growth-limiting factor. Measurements of 18 O, Cl , 3 H and hydraulic head in surface water and shallow groundwater in an oxbow lake-wetland in northern Mississippi...
Article
Full-text available
Since 1948, the United States Department of Agriculture has assisted construction of over 10,000 flood control dams, many of which are reaching the end of their design life. Rehabilitation by dredging, or decommissioning by dam removal both have the potential to mobilize contaminants currently sequestered in the sediments. Plans to rehabilitate a s...
Article
Full-text available
Sediment cores were collected from 2 sites in the forested fringe of an oxbow lake surrounded by land that was converted from forest to agricultural use in the late 19th century. The 2 sampling areas were selected to represent areas of high (West site) and low (East site) current sediment accumulation rates, based on distance from a perennially dis...
Article
Sulfur hexafluoride was injected as a tracer gas into the air stream during air-drilling of a borehole in the unsaturated zone of a partially-welded, fractured tuff at Apache Leap, Arizona. One-meter intervals were later isolated at multiple depths and pumped to purge drilling air from each interval. The volume of air purged (at 1 atm, 20 °C), rang...
Article
The radiocarbon activity of carbon collected by vacuum distillation from a single partially saturated tuff began to decline after approximately 60% of the water and carbon had been extracted. Disproportionate changes in 14C activity and δ13C during distillation rule out simple isotopic fractionation as a causative explanation. Additional phenomena...
Article
The occurrence and significance of aqueous flow through fractures in unsaturated tuff was investigated at the Apache Leap Research Site near Superior, Arizona. Water samples for geochemical and isotopic analysis were collected from water seeping from fractures in a mine haulage tunnel, from the saturated zone in a vertical borehole (USW UZP-4), and...
Article
Full-text available
In a long-term evaluation of the injection of treated wastewater into an alluvial aquifer near El Paso, TX, the boron (B) concentration and B stable isotopic values were investigated as potential intrinsic tracers of recharge-water source. The B stable isotopic values (delta(11)B) of background groundwater (14 parts per thousand) and water from ant...
Article
The theoretical minimum difference between the δ13C of soil CO2 (a concentration) and soil-respired CO2 (a flux) was previously thought to be 4.4‰. It is shown here that the difference is a function of the δ13C of soil-respired CO2, with possible minimum values less than 4.4‰. A simple equation is given which allows the δ13C of soil CO2 or soil-res...
Article
Full-text available
Distillation offers four advantages over current centrifugation and compression methods for obtaining pure-water carbon: 1) carbon recovery is possible from rocks that will not yield water by centrifugation or compression; 2) the mass required for 14C analysis can typically be obtained in a single extraction, eliminating the need for storing and co...
Article
*The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and eva...
Article
The B isotopic ratio of a fly ash leachate can be very different from the B isotopic ratio of a natural groundwater. Mixtures of leachate and groundwater typically result in nonlinear B isotope mixing curves that enable identification and quantification of leachate contamination in a groundwater at much lower levels than possible using concentratio...
Article
This is a final technical report for a project of the U.S Nuclear Regulatory Commission (sponsored contract NRC-04-090-51) with the University of Arizona. The contract was an optional extension that was initiated on July 21, 1994 and that expired on May 31, 1995. The project manager was Thomas J. Nicholson, Office of Nuclear Regulatory Research. Th...

Network

Cited By