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Seasonal Dynamics Of Dissolved Iron On The Antarctic Continental Shelf: Late-Fall Observations From The Terra Nova Bay And Ross Ice Shelf Polynyas, P. N. Sedwick, B. M. Sohst, C. O'Hara, S. E. Stammerjohn, B. Loose, M. S. Dinniman, N. J. Buck, J. A. Resing, S. F. Ackley

OES Faculty Publications

Over the Ross Sea shelf, annual primary production is limited by dissolved iron (DFe) supply. Here, a major source of DFe to surface waters is thought to be vertical resupply from the benthos, which is assumed most prevalent during winter months when katabatic winds drive sea ice formation and convective overturn in coastal polynyas, although the impact of these processes on water-column DFe distributions has not been previously documented. We collected hydrographic data and water-column samples for trace metals analysis in the Terra Nova Bay and Ross Ice Shelf polynyas during April-May 2017 (late austral fall). In the Terra Nova …

Adapting Tropical Forages To Low-Fertility Soils, Idupulapati M. Rao

IGC Proceedings (1997-2023)

Tropical forages growing in low-fertility acid soils usually increase the amount of dry matter partitioned to roots at the expense of shoot growth, but substantially different adaptive attributes to such soils have been found, both between and within species. By possessing the C₄ pathway of photosynthesis, grasses are more efficient than legumes in using N, Ca, and P, whereas legume roots are more efficient in extracting nutrients from low-fertility soils. Phosphorus uptake efficiency (mg of P uptake in shoot biomass per unit root length) of the legume Arachis pintoi is several times higher than that of the grass Brachiaria …

Investigating Gallium Inclusion In Aluminum And Iron Oxyhydroxides, Corey A. Palmer

Masters Theses

Because Ga shares many physicochemical properties with Al and Fe, Ga may be able to incorporate into Al and Fe oxy-hydroxides. Understanding how Ga incorporates into these oxy-hydroxides may be crucial for finding Ga-rich bauxite deposits. In order to find the difference in Ga inclusion rates into oxy-hydroxides, as well as understand the mechanisms for this Ga inclusion, Al and Fe oxy-hydroxides were synthesized in the lab with Ga additions of 2 mol % Ga and 20 mol % Ga for a low-Ga and high-Ga treatment, respectively, along with a no added Ga control. X-Ray diffraction analyses confirmed the formation …

The Effects Of Seasonal Variations In Chemistry And Hydrology On The Microbial Community And Its Sulfide Oxidation Potential In A Naturally Acidic Maine Stream, Raymond C. Kahler Iii

Electronic Theses and Dissertations

Sulfide minerals oxidize through interaction with water and oxygen, releasing hydrogen ions. The process often occurs naturally near metal sulfide deposits, and can be accelerated through mining. Microorganisms accelerate the rate of sulfide oxidation. Acidified streams typically contain high metal concentrations (e.g. aluminum) and microbes in these systems may develop resistances to metal toxicity. Stream flow can affect sulfide oxidation and microbial community structure. Baseflow can influence stream chemistry from interactions with the surrounding bedrock, while stormflow affects stream chemistry and the local microbial community through dilution and addition of microbes transported by runoff. Microbial community composition is affected by …

Differential Effects Of Canopy Trimming And Litter Deposition On Litterfall And Nutrient Dynamics In A Wet Subtropical Forest, Steven J. Hall, Whendee L. Silver, Grizelle González

Steven J. Hall

Humid tropical forests have the highest rates of litterfall production globally, which fuels rapid nutrient recycling and high net ecosystem production. Severe storm events significantly alter patterns in litterfall mass and nutrient dynamics through a combination of canopy disturbance and litter deposition. In this study, we used a large-scale long-term manipulation experiment to explore the separate and combined effects of canopy trimming and litter deposition on litterfall rates and litter nutrient concentrations and content. The deposition of fine litter associated with the treatments was equivalent to more than two times the annual fine litterfall mass and nutrient content in control …

Monitoring The Influence Of Acid Deposition On Soil And Implications To Forest Health In The Daniel Boone National Forest, Tyler M. Sanderson

Theses and Dissertations--Forestry and Natural Resources

Combustion of fossil fuels has contributed to many environmental problems including acid deposition. The Clean Air Act (CAA) was created to reduce ecological problems by cutting emissions of sulfur and nitrogen. Reduced emissions and rainfall concentrations of acidic ions have been observed since the enactment of the CAA, but soils continue to receive some acid inputs. Soils sensitive to acid deposition have been found to have low pH, a loss of base cations and a shift in the mineral phase controlling the activity of Al³⁺ and/or SO₄^2-. If inputs continue, soil may be depleted of base …

Aluminum In Silica Phases Formed In Hot Springs, Nancy W. Hinman, J. Michelle Kotler

Geosciences Faculty Publications

Sinters are difficult to characterize with traditional methods and are often described by their chemical composition alone. Yet information about the depositional environment and possible diagenetic processes is available in atomic structure. This study probes the atomic structure of siliceous sinters from two geothermal areas using nuclear magnetic resonance (NMR) spectroscopic techniques. Specifically, this study demonstrated that Al is present in tetrahedral coordination with or without octahedral coordination in geyserites from Yellowstone National Park, WY, USA and Geyser Valley, Kamchatka, Russia.

Global Estimates Of Mineral Dust Aerosol Iron And Aluminum Solubility That Account For Particle Size Using Diffusion-Controlled And Surface-Area-Controlled Approximations, Qin Han, Charles S. Zender, J. Keith Moore, Clifton S. Buck, Ying Chen, Anne Johansen, Christopher I. Measures

All Faculty Scholarship for the College of the Sciences

Mineral aerosol deposition is recognized as the dominant source of iron to the open ocean and the solubility of iron in the dust aerosol is highly variable, with measurements ranging from 0.01–80%. Global models have difficulty capturing the observed variations in solubility, and have ignored the solubility dependence on aerosol size. We introduce two idealized physical models to estimate the size dependence of mineral aerosol solubility: a diffusion‐controlled model and a surface‐area‐controlled model. These models produce differing time‐ and space‐varying solubility maps for aerosol Fe and Al given the dust age at deposition, size‐resolved dust entrainment fields, and the aerosol …

Rapid And Noncontaminating Sampling System For Trace Elements In Global Ocean Surveys, Gregory A. Cutter, Kenneth W. Bruland

OES Faculty Publications

A system for the rapid and noncontaminating sampling of trace elements with volumes of up to 36 L per depth and including the dissolved and particulate phases has been developed for ocean sections that are a crucial part of programs such as International GEOTRACES. The system uses commercially available components, including an aluminum Seabird Carousel with all titanium pressure housings for electronics and sensors to eliminate zinc sacrificial anodes and holding twenty-four 12 L GO-FLO bottles, and a 7500 m, 14 mm Vectran conducting cable (passing over an A-frame with nonmetallic sheave) spooled onto a traction winch. The GO-FLO bottles …

Controls On Dissolved Cobalt In Surface Waters Of The Sargasso Sea: Comparisons With Iron And Aluminum, R. U. Shelley, Peter N. Sedwick, T. S. Bibby, P. Cabedo-Sanz, T. M. Church, R. J. Johnson, A. I. Macey, C. M. Marsay, E. R. Sholkovitz, S. J. Ussher, P. J. Worsfold, M. C. Lohan

OES Faculty Publications

Dissolved cobalt (dCo), iron (dFe) and aluminum (dAl) were determined in water column samples along a meridional transect (∼31°N to 24°N) south of Bermuda in June 2008. A general north-to-south increase in surface concentrations of dFe (0.3-1.6 nM) and dAl (14-42 nM) was observed, suggesting that aerosol deposition is a significant source of dFe and dAl, whereas no clear trend was observed. for near-surface dCo concentrations. Shipboard aerosol samples indicate fractional solubility values of 8-100% for aerosol Co, which are significantly higher than corresponding estimates of the solubility of aerosol Fe (0.44-45%). Hydrographic observations and analysis of time series rain …

Phonon Density Of States Of Iron Solid Solutions At Ambient And High Pressures Using Nuclear Inelastic X-Ray Scattering (Nrixs), Samantha L. Combs, Elizabeth A. Tanis, Malcolm Nicol

Undergraduate Research Opportunities Program (UROP)

Nuclear resonant inelastic x-ray scattering (NRIXS) of synchrotron radiation uses the energy transferred during the inelastic nuclear absorption of photons to determine phonon density of states for solid Mössbauer isotopes. This type of experiment can be conducted at ambient and high pressures with the use of a diamond anvil cell (DAC) and a rhenium gasket. Here, we are concerned with the phonon DOS of α-FePt 10% at pressures up to 30 GPa, as well as FeAl 4.3%, 6.4%, and 27.1% at ambient pressures. The iron samples used are doped in order to increase the pressure at which the alpha to …

Biogeochemistry Of Arsenic And Antimony In The North Pacific Ocean, Gregory A. Cutter, Lynda S. Cutter

OES Faculty Publications

The biogeochemical cycles of the metalloid elements arsenic and antimony were examined along a 15,000 km surface water transect and at 9 vertical profile stations in the western North Pacific Ocean as part of the 2002 IOC Contaminant Baseline Survey. Results show that the speciation of dissolved arsenic (As III, As V, and methylated As) was subtly controlled by the arsenate (AsV)/phosphate ratio. An additional fraction of presumed organic arsenic previously reported in coastal waters was also present (~15% of the total As) in oceanic surface waters. Dissolved inorganic antimony displayed mildly scavenged behavior that was confirmed by correlations with …

The Effects Of Temperature And ƑO2 On The Al-In-Hornblende Barometer, J. L. Anderson, Diane R. Smith

Geosciences Faculty Research

The Al-in-homblende barometer potentially offers a basis for estimating crystallization pressure for granitic batholiths. However, owing to the simplicity of its formulation, misuse of the barometer can occur. Many granitic intrusions are emplaced at conditions inconsistent with those of the existing experimental calibrations, including f_O2 < NNO and/or variable to high temperature. The barometer is sensitive to variations in both f_O2 and temperature: low f_O2 can cause calculated pressures to be high by a factor of two or more, and the effect of temperature is up to 2 kbar per 100 °C, depending on total Al abundance.

Batholiths emplaced at elevated temperature and portions of plutons that crystallized below …

Liming Tobacco Soils, J. L. Sims

Soil Science News and Views

Control of soil acidity by liming is very important in successful tobacco culture. Adding lime to an acid soil increases the availability of nearly all plant nutrient elements, increases the efficiency of added fertilizers, and prevents the toxic effects of high concentrations of soluble aluminum, manganese, and iron. It is a natural tendency for most Kentucky soils to become acid with time due to losses of bases (calcium, magnesium, potassium, and sodium) from soil by rainfall, However, tobacco soils possess certain unique problems that warrant careful monitoring of soil pH every two to three years.

The Construction And Operation Of A Universal Specimen Mount With Protective Lead Shield For The Purpose Of Determining Pole Figures Using The Schulz-Decker Transmission Technique, Richard L. Fausner

Bachelors Theses and Reports, 1928 - 1970

It was the purpose of this study to construct a universal mount, to construct a protective lead shield, to operate the instrument, and to provide a pole figure using the transmission method of Schulz and Decker. There are at present several lengthy x-ray methods of determining the grain orientation of metals. These methods are mainly photographic. In order to provide a rapid means of obtaining the necessary information concerning the grain orientation of a metal, a universal mount was constructed.

The Effect Of Germanium On The Current Efficiency In The Electrolysis Of Pure Zinc Sulfate Solution, Keith R. Bock

Bachelors Theses and Reports, 1928 - 1970

It has long been recognized that electrolytic zinc cells are extremely sensitive to impurities. In fact, cer­tain impurities present in amounts as low as 0.1 mg/1 cause a serious loss of current efficiency. Also, the presence of several impurities in the electrolyte may accelerate the detrimental effect of each impurity.

Recrystallization Of High Purity Aluminum, Virgil H. Griswold Jr.

Bachelors Theses and Reports, 1928 - 1970

If a metal is first cold-worked and then heated to a sufficient temperature for an adequate length of time, the hardening properties due to cold-working disappear, and the metal will return more or less to its original state. Upon examination of the microstructure, we find that new grains have replaced the old grains through what is called recrystallization. The final size of the recrystallized grains depends upon three important variables--the degree of cold-work or deforma­tion, annealing temperature, and annealing time.

The Effect Of Manganese On The Age Hardening Of Aluminum-Copper Alloys, Keith P. Burgess

Bachelors Theses and Reports, 1928 - 1970

It is known that age-hardening occurs in alloys of the solid solution type containing a hardening constituent, of a metal or metallic compound which is more soluble in the solvent phase at higher tempertures than at lower temperatures.

The Metallography Of Aluminum Casting Alloys, Donald D. Goehler

Bachelors Theses and Reports, 1928 - 1970

The purpose of this thesis is to supply the Montana School of Mines with an up to date source of information concerning the metallography of aluminum casting alloys. This thesis is designed as a continuing project. Ultimately, it is hoped that a catalog containing all the typical structures of aluminum casting alloys will develop.

The Age-Hardening Of Aluminum With Mgzn2, Sidney E. Worthen

Bachelors Theses and Reports, 1928 - 1970

The purpose of this thesis is to investigate the age-hardening of aluminum with magnesium and zinc in such proportions as to conform to the compound MgZn₂.

Because of a lack of time and proper equipment, the only property investigated was the hardness as indicated by the Rockwell Superficial Hardness Tester.

The Age Hardening Of Silver With Copper-Silicide, Joseph Edward Shaw

Bachelors Theses and Reports, 1928 - 1970

The successful application of the phenomenon of pre­cipitation hardening to aluminum and copper has indicated the possibility of hardening all metals in the same way. The phenomenon of age hardening was discoveredin 1911, and since that time much research has been car­ried on in all parts of the world on various alloy sys­tems.

Structure Of Eutectics, Dilip K. Das

Bachelors Theses and Reports, 1928 - 1970

The present paper is a result of work done on the study of structures of eutectics of a certain eutectic-forming binary systems. In this research work no systems with intermetallic compounds have been studied.

The Electroplating Of Cadmium From Sulfate Solutions, Lewis S. Prater

Bachelors Theses and Reports, 1928 - 1970

It has been proven that cadmium forms a very satisfactory plate on steel, which has to withstand severe corrosion, especially the corrosion of sea water and spray. The metal is now successfully plated electrolytically from cyanide solutions, but wherever work is carried on with cyanide, there is great danger of poisoning to the workers.

The Electrolytic Deposition Of Chromium Upon Aluminum, E. Fults, L. D. Voerge

Bachelors Theses and Reports, 1928 - 1970

The purpose or this investigation is primarily to determine the best conditions for plating chromium on aluminum. The work was carried out with the hope of obtaining coherent deposits, and of determin­ing the conditions under which such deposits may be duplicated.