• ABSORPTION OF NITROGEN-OXIDES AND INFLUENCE ON NITROGEN TRANSFORMATIONS IN SOILS

      Eberhardt, Paul Joseph James, 1945- (The University of Arizona., 1972)
    • Addressing State Funding Assistance Through the Arizona State Aquatic Nuisance Species Management Plan: An Exercise in Policy Writing.

      King, Chad Eric. (The University of Arizona., 2002)
      Aquatic nuisance species (ANS) represent a growing problem in Arizona that is receiving little funding attention. With the objective of addressing this problem in a coordinated manner between state and federal agencies, the task of writing the Arizona State Aquatic Nuisance Species Management Plan was undertaken, this process and its results will be discussed. Section 1204 of the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 (P.L. 101-646), provides opportunity for federal cost-share upon adoption of a state management plan. Methodology included gathering input towards reworking an early draft of the plan at a number of meetings, including the Lower Colorado Giant Salvinia Task Force, the Salvinia molesta National Convention, and Southwest Vegetation Management Association, and researching the format and process used in writing plans recently adopted in other states. Developments in management needs were incorporated, several of the plan's tasks were initiated and the plan was presented to agency members for comments and review. The resulting management plan is now ready to be signed into action, requiring approval by the state governor as a final step towards providing additional funds to fight ANS.
    • ADSORPTION OF HEAVY METALS ON SOIL CLAYS (KAOLINITE, CADMIUM, MONTMORILLONITE, ZINC).

      PULS, ROBERT WILLIAM. (The University of Arizona., 1986)
      Metal cation adsorption is the predominant chemical mechanism governing the attenuation of toxic metal movement in soils. Clay minerals are the primary adsorbent surfaces in soils due to their ubiquitous nature and large reactive surface area. This study examined the relative affinity of the metals cadmium, nickel and zinc for the clay minerals kaolinite and montmorillonite. The influence which different mineral adsorbents and different complexing ligands in solution have on the adsorption of metal ions was assessed using the Hard-Soft Acid-Base Principle as a theoretical framework for predicting the maximum extent of adsorption and rate of adsorption. The HSAB principle is that hard bases prefer to complex hard acids and soft bases prefer to complex soft acids. The hypothesis that initiated these investigations was that the hard-soft character of mineral surfaces is due to their surface functional groups and can be measured using metal cation adsorption selectivity experiments where pH and complex ion formation are controlled. When complex ion formation in aqueous solution was minimized (i.e. in Ca(ClO₄)₂), adsorption decreased in the order of decreasing softness, CD > Zn > Ni for both clay minerals. Montmorillonite behaved as a slightly harder Lewis base than kaolinite, sorbing the harder Ni and Zn ions to a greater extent than Cd, although both minerals behaved as soft Lewis bases. In the presence of chloride and sulfate ligands, adsorption sequences changed and reflected results from typical soil solution studies. In some cases the adsorption sequences can be explained using the HSAB principle together with computer speciation data and this approach merits further consideration and research. Adsorption over time and calculated adsorption rate constants were generally consistent with equilibrium selectivity data. Adsorption rates decreased in the order Cd > Zn > Ni in Ca(ClO₄)₂ for both clay minerals. The adsorption curves reflect a two-step adsorption process involving a rapid exchange-type reaction followed by a much slower adsorption involving diffusion into the crystal or alteration of the surface through the formation of a new solid phase involving the adsorbed ions.
    • Adsorption/desorption of phenols on the Pima clay loam soil

      Yiannakakis, Alexandros Emmanuel, 1959- (The University of Arizona., 1988)
      A linear distribution isotherm described the sorption/desorption of four phenols on the Pima clay loam soil. The linear distribution coefficients for 2,4-dichlorophenol, 2-chlorophenol, phenol and 2,4,6-trichlorophenol were 3.61, 2.93, 0.87, and 0.79. Ionization of the phenols affected their relative distribution order. Hydrogen bonding of phenols to exposed mineral sites accounted for the greater measured sorption than was predicted. The effect of solid concentration on the distribution of phenols was tested over a 10-fold soil/solution range. When a log transformation was performed on the data, a highly significant inverse relationship existed between the distribution of phenols and the soil/solution ratio. A 3-fold increase in the dissolved organic carbon in solution was associated with the decrease in the distribution coefficient. A 3-fold increase in the fraction organic carbon in the soil occurred when dry sludge solids were added to the Pima soil. A substantial increase in the dissolved organic carbon in solution was associated with the addition of sludge solids to the soil. (Abstract shortened with permission of author.)
    • The Aggregated Precipitation of Iron Minerals in Three Systems: Tubular Growth, Liesegang Patterns, and Interfacial Cementation

      Stone, David Andrew (The University of Arizona., 2007)
      My research has focused on the precipitation of iron minerals, mostly oxides and hydroxides, in aqueous systems across steep pH and Eh gradients. Unlike most work in this area, which involves loose precipitates filtered out of solutions, I have focused on precipitated aggregates and, more specifically, on those that are self-organized into dis-crete structures or patterns. This topic is actually quite narrow because such types of natu-ral material organization are rare within the geochemical realm compared with the mor-phological richness of crystals, not to mention the phantasmagoria of life.My investigation of iron-based examples has included three types of physical sys-tems: 1) growth of tubular structures around bubbles coming off a charged cathode in a free solution where convection dominates; 2) development of Liesegang patterns within gelled solutions due to reactions dominated by diffusion; and 3) formation of a cement-ing matrix within the aqueous interface between particles of silica. The third case in-volves physical characteristics of the first two in that it is primarily a tightly packed, dif-fusion-limited process, but at least initially the generation of gases can create mechani-cally driven flows through the interstitial spaces.All three systems and studies are inextricably related for both tubular ('vermi-form') structures and Liesegang patterns are commonly found in natural iron-cemented sediments such as massive laterite, ironstone deposits, and banded iron formations. They are also found on a much smaller scale within discrete 'concretions' and represent the two poles of the gradient between convection-based and diffusion-based systems. As Seilacher (2001) states concerning concretions, "the distribution and precipitation of dis-solved constituents, such iron and manganese, proceeds in two radically different mor-phospaces, which are typified by dendrites [and I would include tubes and other linear growth] on the one hand and Liesegang rings on the other." Both have been observed in my lab creations with surprising frequency and tenacity even in systems thought to be in-hibitory.
    • Alfalfa water-production functions under conditions of deficit irrigation with saline water

      Pennington, Karrie Sellers,1949- (The University of Arizona., 1986)
      This experiment was designed to determine the shape of the yield response function relating crop yield to total amount of saline irrigation water applied. Such a function contains a built-in leaching fraction that is the inevitable consequence of the inability of the plant to extract 100 % of the water from a saline soil. In order to define the production function and to determine the leaching fractions, alfalfa (Medicago sativa L. cv. 'Mesa Sirsa') was planted in soil columns in a greenhouse. Two experiments were run sequentially. These were irrigated with water of differing salinities. The first with an EC of 4 dS/m (1.4 bars) and the second with an EC of 8 dS/m (2.9 bars). Both solutions were prepared by adding equivalent amounts of sodium chloride and calcium chloride to distilled water. The treatment variables were amounts of irrigation water applied. The amounts in both experiments were 110%, 100%, 75%, 50% and 25% of the measured evapotranspiration (ET). Four crop harvests were made in each experiment. At the end of experiment 1, (approximately 120 days), one column from each treatment was destructively sampled for soil salinity and water content measurements. The remaining columns were similarly sampled at the end of experiment 2 (approximately 120 days). The crop-saline water production functions for both experiments were linear. Leaching fractions in experiment 1 were 9, 9, 6, 5 and 5% for treatments 1-5 respectively. Experiment 2 leaching fractions for treatments 1-5 respectively were 23, 25, 18, 15 and 17%. The lowest rootzone soil water osmotic potentials achieved by the end of experiment 1 for treatments 1-5 were -19, -20, -18, -26 and -24 bars. Corresponding treatment values achieved by the end of experiment 2 were -18, -22, -28, -31 and -45 bars.
    • Analyses of Productivity of Nile Tilapia (Oreochromis niloticus), Red Tilapia (O. niloticus X O. mossambicus) and Pacific White Shrimp (Litopenaeus vannamei) Polyculture in a Recirculating System

      Hernandez - Barraza, Cesar Arturo (The University of Arizona., 2010)
      Improving the efficiency of production, profitability and nutrient utilization are the most important factors for aquaculture companies. Many research efforts have been focused to develop strategies that improve the productive performance of shrimp farms. One recognized strategy is polyculture, which can considerably improve farm production yields by optimizing use of available resources.Tilapia production in shrimp ponds (with and without shrimp) has increased rapidly in many countries including Thailand, the Philippines, Honduras, Mexico, Peru, and the inland desert of Arizona.A current practice in extensive, semi-intensive and intensive culture systems is the integration of tilapia with shrimp to increase total productivity. I tested this hypothesis in the present trials experimentally by co-cultivating tilapia and Pacific white shrimp in closed recirculating systems. The present series of experiments were carried out over a period of three years between 2007 and 2009. All of these studies were developed and conducted at the facilities of the Environmental Research Lab (ERL) of the University of Arizona in Tucson, AZ.A preliminary study included three treatments in low salinity water (5 ppt). White shrimp post larvae were stocked into cylindrical plastic pools and Red tilapias were stocked into aquaria. Equal numbers of shrimp were placed in all the treatments whereas fish (Red tilapia) density was variable. We found good growth and 100 % survival of shrimp and tilapia.The first experiment included five treatments with four replicates each with saline water of 10 ppt. Shrimp and Nile tilapia were weighed and distributed in 20 fiberglass tanks with capacity of 200 liters. There were evaluated finding statistically significant differences in growth of tilapia (P< 0.05) but no significant difference in growth of shrimp at different fish densities (P> 0.05)The second and third experiments included four treatments with four replicates each using the same shrimp density in each study but different fish density by treatment. Results of one-way analysis of variance (ANOVA) for the second experiment showed a significant effect of the shrimp- tilapia polyculture on the growth of Pacific white shrimp (P< 0.05) but not for tilapia (P> 0.05) compared with monoculture. In the third experiment, there were significant differences in the growth of shrimp (P< 0.05) but not significant differences in the growth of fish (P> 0.05). These experiments were conducted using slightly different culture systems.
    • Analysis and Molecular Characterization of an Unusual Copper Inducible Homeostasis Mechanism in Pseudomonas putida KT2440

      Quaranta, Davide (The University of Arizona., 2009)
      The purpose of this research was to identify and characterize novel molecular mechanisms in copper homeostasis. Pseudomonas putida KT2440 is a soil bacterium studied for its potential use in bioremediation of soils contaminated with aromatic organic contaminants. The cinAQ operon was analyzed. cinAQ is transcribed in presence of copper. The product of cinA is a periplasmic azurin-like protein with a methionine and histidine rich region, characterized by a high redox potential (456 ±4 mV). CinQ was shown to be a pyridine nucleotide-dependent nitrile oxidoreductase that catalyzes the reduction of preQ₀ to preQ₁, the first committed step in the biosynthetic pathway leading to the production of the unusual nucleotide queuosine. Gene disruption of cinQ in Pseudomonas putida KT2440 and in Pseudomonas aeruginosa PAO1 did not result in a significant increase in copper sensitivity on disk assays. Furthermore, a P. putida KT2440 cinA mutant also did not present a greater sensitivity to copper on disk assays while cinA mutants in Pseudomonas aeruginosa PAO1 presented increased toxicity to copper compared to the wild-type. CinA is by sequence similarity proposed to be an electron shuttle, and was shown to be upregulated in the presence of copper. Increasing CinA levels in the periplasm after copper stress may represent a mechanism used to regenerate the multicopper oxidase CopA (involved in Cu(I) to Cu(II) oxidation). Alternatively, CinA could act as an electron shuttle that takes part in an alternative electron transport chain once redox active copper is available, or it could represent a periplasmic copper chaperon. CinQ is involved in the biosynthesis of the rare hyper-modified nucleotide queuosine, found in the wobble position of several tRNAs, and required to avoid the readthrough of the stop codon UAG. Transcription of cinAQ was shown to be under the control of the two component system CinR-CinS. CinS is a histidine kinase, with a sensor domain located in the periplasm. CinR is the cognate response regulator that activates transcription of genes upon phosphorylation from CinS. The CinR-CinS two component system was shown to be responsive to 0.5 LM copper. CinS displayed very high metal specificity and elicited a response only in the presence of copper and silver, but not other metals. Modeling of the CinS protein structure, performed using Swiss Model and using the periplasmic sensor DcuS from Escherichia coli as a template, identified a potential copper binding site, containing H37 and H147. Sequence alignment of copper sensing histidine kinases further identified other conserved residues in the periplasmic domain. Site-Directed Mutagenesis was used to generate CinS mutants that were tested for their ability to activate the cinAQ promoter in presence of Cu. When challenged with copper CinS mutant H37R and H147R had an almost 10 fold reduction in copper sensitivity compared to the wild-type, indicating a possible role in Cu coordination. Other CinS mutants responded similarly to the wild-type in the presence of 10 μM of Cu.
    • Analysis of a gas-phase partitioning tracer test conducted in fractured media

      Simon, Michelle A. (The University of Arizona., 2004)
      This work successfully applied the gas-phase partitioning tracer method to determine the NAPL, water and air saturations in the vadose zone at the field scale. This project was one of the first, and still one of the few, field-scale gas-phase partitioning tracer tests. This work differs from other work in that it was conducted in a high water content, fractured clay. There were three primary components of this work. First, gas-phase tracers were identified and their NAPL-air and Henry's Law constants measured. There were four types of tracers used in this study: noble gases or nonpartitioning tracers; alkanes, which were expected to be nonpartitioning tracers; perfluorides, NAPL partitioning tracers; and halons, NAPL and water partitioning tracers. A laboratory method for measuring NAPL-air partition coefficients was developed and TCE-air partition coefficients were measured for the perfluoride and halon tracers. The second component of this study involved conducting a field-scale gas-phase partitioning tracer test, the results which were used to estimate NAPL, water and air saturations. The NAPL saturation, calculated to be an extremely low value, resulted in an estimate of NAPL mass present that is similar to the amount that has subsequently been extracted from the test site via SVE remediation. The alkane tracers, which had been used previously in laboratory column studies as nonpartitioning tracers, were more retarded than the perfluoride tracers at this site. It was the alkane tracers, and not the halon tracers, that were used to determine the water content. The water content was estimated to be approximately 90%, which is unexpectedly high for a vadose zone. Additionally, the tracer response time, vacuum data, and other geological data indicated that the tracer test was performed in fractured clay. The third component of this work comprised an analysis of the tracer test data to determine transport parameters. The analysis employed matching eight simple mathematical models to the experimental data. All of the models tested: two porous, three double-porosity, and three fracture-based (single fracture, multifracture, fracture-matrix) models could reasonably match the experimental data and no one model resulted in consistently superior predictions than the others.
    • Analysis of the Phylogenetic and Functional Dynamics of Microbial Communities in Metalliferous, Acid-Generating Mine Tailings Subject to a Phytostabilization Treatment

      Valentín-Vargas, Alexis (The University of Arizona., 2013)
      Extensive research conducted over the last decade has demonstrated the great potential of phytostabilization for the reclamation of abandoned mine tailing piles. The right combination of plant species and soil amendments can facilitate the growth of a permanent vegetative cover on the tailings that will help minimize the mobilization of metal-bearing particles by means of wind dispersion and water erosion. Despite previous research efforts, the diversity and potential role of microbial populations inhabiting the root zone of the plants on the stabilization of the metal(loid) contaminants remains mostly unresolved. The study presented in this dissertation represents one of the first comprehensive efforts aimed to understand the ecology and dynamics of microbial communities colonizing both bulk and rhizosphere tailings during phytostabilization as an initial step towards elucidating the role of microbes in the stabilization of metal(loid) contaminants during the remediation treatment. This study was divided into two main projects: (1) the first aimed to monitor the temporal variations in functional and taxonomic diversity of prokaryotic populations in acid-generating metalliferous mine tailings during phytostabilization to determine how they respond to and/or influence changes in environmental parameters and to identify key patterns in their composition that may serve as bioindicators of soil health and the success of the remediation treatment; and (2) the second aimed to expand our understanding of the dynamics of root-associated bacterial, fungal and archaeal communities during mine tailing phytostabilization and how the dynamic behavior of the communities correspond to the growth of plants, the addition of soil amendments, and fluctuations in environmental conditions. The results presented here demonstrate that different microbial groups respond differently to changes in environmental conditions during phytostabilization, suggesting that by monitoring the behavior of specific microbial groups in the systems (as bioindicators) we may be able to assess the effectiveness of the remediation treatment. Furthermore, the results from the taxonomic and functional analysis of the microbial communities served as the basis for the development of a model that explains the ecology and distribution of dominant microbial groups in the tailings that may significantly contribute to the oxidation of iron-sulfides, the production of acid mine drainage, and to facilitate plant establishment and survival during phytostabilization.
    • Andisols of the San Francisco Volcanic Field, Arizona

      Chen, Chuangming, 1960- (The University of Arizona., 1988)
      Six pedons derived from volcanic cinders from the San Francisco Volcanic Field near Flagstaff, Arizona, were studied to evaluate their physical, chemical, and mineralogical properties for inclusion in the proposed soil order Andisol. All the pedons meet the requirements for the Andic soil properties and they are thus classified as either Typic Ustivitrand or Melanic Ustivitrand Subgroups of Andisol Order. The proposed classification is discussed with respect to the guidelines presented in the ninth International Committee of Classification on Andisols (ICOMAND) letter.
    • Antimicrobial Efficacy of Copper Alloys in Changing Environmental Conditions

      Elguindi, Jutta Ehlert (The University of Arizona., 2011)
      Copper cast alloys de-activate antibiotic-resistant bacteria on contact and could be very effective in decreasing potentially harmful microorganisms in the environment. In this study copper alloys with varying copper contents were utilized to evaluate their antimicrobial effects on Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecium in changing environmental conditions. The survival rates of P. aeruginosa wild type and its derivative transposon mutants of the cin operon on copper cast alloys were investigated in order to demonstrate the influence of genes involved in copper resistance. The gene disruption of the response regulator of the cin operon resulted in shorter survival rates on copper alloys, which was also influenced by temperature and method of exposure. Bacteria often have acquired copper resistance mechanisms in order to withstand higher copper concentrations in their surroundings, which may be a factor in their survival rates on copper surfaces. Copper- and antibiotic-resistant E. coli and E. faecium strains were obtained from pigs raised on feeds containing copper sulfate and antibiotics. Survival rates of these bacteria were influenced by the percentage of copper in the alloys, varying moisture conditions on copper surfaces, suspension media used, and differences between strains. Survival was also dependent on copper corrosion rates since corrosion inhibition with benzotriazole or a thick surface layer of thermal oxide resulted in prolonged survival on copper surfaces. Corrosion of copper surfaces releases copper ions which directly affect bacterial survival on copper alloys. The results obtained in this study emphasize that copper alloys are effective as antimicrobial materials but changing environmental conditions can significantly influence bacterial survival on copper surfaces. These findings can be applied to a better utilization of copper alloys in water, food, and healthcare environments. Antibiotic- and copper ion-resistant bacteria can be killed on contact with copper alloys which makes the proliferation of these microorganisms less likely and reduces the risk to human health. However, in a very different environment copper ion-resistant microbes can be useful for plant-microbe associations in bioremediation of copper mining wastelands.
    • Application of Advanced Molecular Techniques in Applied Environmental Microbiology

      Iker, Brandon Charles (The University of Arizona., 2013)
      Recent advancements in molecular biology such as next generation sequencing and more sensitive and rapid molecular detection methods like qPCR, have historically been developed for clinical applications in human genetics and for health care diagnostic purposes. The high demand for faster and more accurate molecular assays in the health care field has driven rapid development of inexpensive molecular techniques that when applied to the science of environmental microbiology, provides an unprecedented level of understanding of the microbial world around us. The goal of this dissertation is to begin to apply more advanced molecular technologies to problems in applied environmental microbiology. Appendix A is a brief literature review of next generation sequencing technologies for applications in environmental microbiology. Appendix B focuses on the development of a more robust virus nucleic extraction kit for the detection of viral genomes from environmental samples found to contain high concentrations of qPCR inhibitors, such as humic acids or heavy metals. Appendix C summarizes one of the largest virus surveys done in the US, using state of the art qPCR technologies in both wastewater influent and effluent from two wastewater treatment plants in the Southwest. Data suggests that traditional virus indicators may not be a viable tool to evaluate fecally impacted source water or virus removal during water treatment. The third study summarized in Appendix D, provides one of the first insights into the microbial ecology of biofilms utilized as biological treatment media using Roche 454 amplicon sequencing of the 16S rRNA gene.
    • Application of cyclodextrins for remediation of organic compounds and heavy metals in soils.

      Wang, Xiaojiang (The University of Arizona., 1995)
      Cyclodextrins, being microbially produced compounds, were investigated for their potential to increase the removal of low-polarity organic compounds in subsurface remediation. It is found that the apparent solubilities of many hydrophobic organic compounds are significantly increased in hydroxypropyl-β-cyclodextrin (HPCD) solutions. The relative solubilities (S(t)/S ₒ) of compounds increase linearly with increasing HPCD concentrations. The solubilization power of HPCD is found to be much greater than that of miscible cosolvents and to be less than that of synthetic surfactants. The lower solubilization power of cyclodextrin can be increased by the addition of a third component such as cyclopentanol. The addition of 0.1% cyclopentanol significantly enhances the solubilization power of β -cyclodextrin (β -CD) for pyrene, acenaphthene, phenanthrene, and fluoranthene which are able to form 1:2 complexes with β-CD in the presence of cyclopentanol. In contrast, cyclopentanol produces no pronounced effect and a marked decrease in the solubilization power of β -CD for naphthalene and anthracene, respectively. These two compounds form 1:1 complexes with β -CD both in the absence and presence of cyclopentanol. The solubilization of all PAHs by γ-cyclodextrin (γ -CD) is significantly enhanced by 1% cyclopentanol. This result indicates that cyclopentanol can increase the hydrophobicity of β -CD cavity without inducing structure-dependent selectivity. We investigated the ability of a modified cyclodextrin, carboxymethyl- β-cyclodextrin (CMCD), to simultaneously complex with low-polarity organic compounds and heavy metals. The results of this experiment show that CMCD could simultaneously enhance the solubilities of the selected organic compounds and complex with Cd²⁺. The complexation of Cd²⁺ by CMCD is not significantly affected by changes in pH or by the presence of relatively high concentration of Ca²⁺.
    • Application of the Hillslope Erosion Model to predict annual sediment yield in Southwest New Mexico.

      King, Chad Eric. (The University of Arizona., 2002)
      The Big Burro Mountains in southwest New Mexico has been undergoing a decrease in herbaceous vegetation and an increase in woody vegetation. Through numerous unnamed ephemeral drainages this area contributes a significant amount of sediment into Mangas Creek, which is a tributary of the Gila River. In 2004, a prescribed burn was conducted to remove the woody vegetation and encourage the growth of herbaceous cover vegetation to reduce the amount of hillslope erosion. The Hillslope Erosion Model was utilized to predict sediment yield occurring in both a burned area and a nearby unburned area. Erosion bridges were established onsite to measure sediment yield. A data logging rain gauge was also located at the monitoring site to measure rainfall duration and intensity. Preliminary data indicates that the Hillslope Erosion Model was found to be a reliable tool for predicting hillslope erosion following rain events greater than one inch.
    • Applications of the inverse approach for estimating unsaturated hydraulic parameters from laboratory flow experiments

      Fleming, John Bentley (The University of Arizona., 2001)
      Estimates of soil hydraulic parameters are essential for predicting and describing water movement in unsaturated soils. Inverse approaches to estimating soil hydraulic parameters have gained great favor. However, limited effort has been placed on obtaining estimates using observed experimental data. Moreover, little has been advanced in applying these approaches to larger scale, multidimensional systems. In this research, several transient laboratory experiments were conducted using both repacked and intact soil cores, and larger scale 1 and 3-dimensional repacked soil columns. Measurements of soil water matric potential and water content were used to obtain parameter estimates for the closed form van Genuchten soil water relations. For the soil cores, measurements were obtained using pressure outflow, upward infiltration and evaporation procedures. For the 1-dimensional soil columns, these same data were obtained using upward and downward infiltration procedures. For the 3-dimensional soil columns, a point source application of water was used. Optimizations were carried out With HYDRUS-1D and HYDRUS-2D using observed matric potential and water content data to define the objective function. For the repacked and intact soil cores, parameters were also estimated by nonlinear least squares fit to retention data obtained from the pressure outflow and evaporation procedures. Parameter estimates obtained by nonlinear least squares fits to the pressure outflow and evaporation retention data were seen to be similar to those obtained by optimization. However, parameter estimates based on data obtained from the upward infiltration experiments were considerably different than those obtained from the evaporation experiments. These differences are attributable to hysteresis. Parameter estimates obtained for the repacked soil cores were seen to be inadequate in terms of predicting matric potential responses in larger scale soil columns. This was also true when parameter estimates obtained from the larger scale repacked soil columns were used to predict matric responses during 3-dimensional flow in the largest scale soil columns. The results of this work show that inverse methods when used in conjunction with upward infiltration and evaporation procedures can provide accurate estimates of unsaturated hydraulic parameters. When used together, these experimental methods can be used to obtain data and hydraulic parameters describing both the imbibition and drying branches of the soil water retention response. These results further show that estimated parameter values based on measurements made at one scale tend to be inappropriate in terms of adequately describing systems at larger scales.
    • Applying spectral mixture analysis (SMA) for soil information extraction on the airborne visible/infrared imaging spectrometer (AVIRIS) data

      Accioly, Luciano Jose de Oliveira (The University of Arizona., 1997)
      The research objectives of this study were formulated to produce the soil spectral maps using spectral mixture analysis on the AVMS data of the Walnut Gulch Experimental Watershed, Tombstone, Arizona. To accomplish this objective the spectral characteristics of eight soils of this Watershed were determined considering the effect of the source of illumination/sensor viewing geometry, degree of wetness (dry vs wet), surface roughness, and the source of the spectra (field, sieved samples and lab) on the selection of image and reference endmembers. The scale effect of the source of spectra was also studied in connection with AVIRIS spectral response. The soils presented anisotropic behavior which varied inversely with the wavelength, and it was reduced under wet conditions. Loss of information occurred when moving from large scale data set (lab, sieved sample, and field spectra) to small scale data (AVIRIS). Cluster analysis and factor analysis were used to extract information about how soil reference endmembers are grouped in relation to viewing angles, degree of wetness and the source of the spectra. Factor analysis was applied to identify the key set of bands that carried most of the information. Soil spectral classes varied as a result of scale effects, soil conditions (wet or dry), and viewing angles. Factor analysis showed that with four unique bands (located at 0.410, 1.310, 0.650, and 2.400 p.m) it was possible to reconstruct the four basic soil spectral curves (Epitaph, Graham, McAllister, and Baboquivari) from the lab dataset. AVERT S image was modeled using mixture analysis on the basis of image endmembers and reference endmembers. Based on the four dimensions of the AVIRIS data image endmembers were defined by three soil spectra (McAllister, Stronghold-3, and Graham) and by one spectra of green vegetation. The shade fractions were separated from dark soils (Graham and Epitaph)on the basis of the spatial context The target test identified at least seven reference endmembers in the AVIRIS scene of the Watershed however; mixture analysis failed in obtaining fraction images from these reference endmembers. Mixture analysis was able to produce fraction images with a relatively high error for a small set (3) of reference endmembers (McAllister and Graham soils, and walnut leaf). However when applied to a subset of pixel extracted from the AVIRIS image mixture analysis identified the reference endmembers and quantified their proportions.
    • Approaches to assessing microbial communities in soil, two examples: Biosurfactant production and phenanthrene degradation

      Bodour, Adria (The University of Arizona., 2002)
      This dissertation is concerned with studying aspects of the ecology of microorganisms from a functional perspective using different microbial populations in soils. In the first study, an investigation was done on the distribution of biosurfactant producing microorganisms. In the second study, temporal changes were observed in an indigenous phenanthrene degrading community following a long-term pulse of phenanthrene.
    • Aquaculture Development in the 21st Century: A Feasibility Study

      VanderLugt, Kyle Richard (The University of Arizona., 2010)
      Continued growth of the aquaculture industry is needed in the 21st century in response to increasing demand from inflated populations and declining wild fisheries capture. Meeting this demand will require bridging the gap between industrialized countries including the United States, and developing and least developed countries (e.g. Mexico, Uruguay, and Uganda). As the aquaculture industry becomes more globally interconnected, industrialized nations will likely be pressured to develop more sustainable practices which are natural resource conservative while developing countries will be pressured to increase production capacity and develop more intensive operations. Albeit with many inherent challenges, a globalized strategic plan is needed to bridge this gap. This dissertation identifies and discusses several of these inherent challenges. Firstly, potential business models are explored with the concept of how information technology can be utilized to integrate small-scale farms in multi-national agribusiness and also coordinate multi-national supply with global demand. Next, the economic impact of aquaculture development is explored. Economic multiplying models may be utilized to predict where aquaculture development will have the most significant and rapid economic impact on rural communities. Lastly, new systems of aquaculture technology are developed which are resource conservative and also have the potential to be scaled to meet industry needs. Re-circulating integrated agriculture-aquaculture (RIAA) systems combine fish and plant production whereby the nutrient rich aquaculture effluent is utilized to irrigate plants. The advantages and disadvantages of these experiments were discussed. While further research is needed to maximize the benefits of RIAA technology, the results demonstrate that these systems provide both economic and environmental benefits over traditional farming methods. Ultimately, this dissertation explores how novel technology can be implemented in strategic locations to provide a sustainable food supply capable of promoting economic growth through the distribution of seafood products to satisfy domestic and global demand.
    • Aspects of ecosystem health in the Colorado River Delta, Mexico

      Garcia Hernandez, Jacqueline (The University of Arizona., 2001)
      Two aspects of ecosystem health in the Colorado River delta were investigated as part of the present dissertation. The following is a summary of the most important findings: Contaminants of natural origin (e.g. selenium) and anthropogenic activities (e.g. pesticides) represent a potential threat for humans and wildlife in the Colorado River delta. Fourteen locations were sampled for bottom material and biota from March 1998 to April 2000. Concentrations of selenium in bottom material ranged from 0.6-5.0 μg/g. Concentrations of selenium in biota ranged from 0.5-18.3 μg/g, 23% of these samples exceeded the toxic threshold where reproductive impairment in birds from dietary exposure is reported. Concentrations of DDE exceeded the lower critical dietary level for sensitive species in 30% of biota samples. No clear relationship could be found between the concentration of Se in bottom material and the concentration of Se in fish. Nevertheless, smaller Se concentrations in biota were found at sites that had an outflow and exposure or physical disturbance of the bottom material was uncommon. Greater concentrations of Se in biota were found at sites with strongly reducing conditions, no output, and subsequent periods of drying and flooding or dredging activities, and at sites that received water directly from the Colorado River. The southwestern willow flycatcher (Empidonax traillii extimus ) is an endangered neotropical migrant with only 300-500 breeding pairs. The objective of the second study was to determine the presence/absence of this bird in the Colorado River delta. Surveys were conducted from June to July, 1999 and from May to June, 2000 using an audio tape of this subspecies' songs to elicit responses. We detected a total of 50 willow flycatchers in the Colorado River delta in the months of May to June. None were detected in July, thus, the birds were most likely migrants. Restoration of the intensively used stopover sites of the Colorado River delta appears to be essential for the overall recovery of this subspecies. Additionally, we propose a possible willow flycatcher summer migratory route throughout the series of coastal estuaries found adjacent to the coast of Sonora.