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    Yamafuji, Kazumasa (The University of Arizona., 2014)
    Biochar (BC), produced through pyrolysis of organic residues, is increasingly being used as a beneficial soil amendment. We studied the effects of BC and animal manure additions on carbon dioxide (CO2) release and nitrogen (N) dynamics in three semi-arid climate soils. The objective of this study was to understand how BC application modifies soil nitrogen dynamics and moderate the effects of manure application in semi-arid agricultural systems on different textured soils: the loamy sand (LS) soil, the silty loam (SL) soil, and the clay loam (CL) soil. We found the positive interaction of BC and manure with BC suppressing CO2 emissions in manure amended soils. BC increased nitrogen mineralization in manure-amended soils towards the end of the incubation period 28 days. No significant N immobilization was observed in unamended soils. BC and manure soil additions reduced N deficiencies in all three soils. A second study focused on measuring carbon dioxide emissions from biochar-amended alkaline semi-arid soil. The objective of this study was to test if acidified and non-acidified BC released the same amount of CO2. The results showed that the soil samples amended with acidified BC released more CO2 than those amended with untreated BC with high alkalinity. It is postulated that untreated BC could absorb CO2; whereas, acidified BC with no alkalinity could not. The LS soil amended with BC released less CO2 than LS soil control perhaps due to the soil microbial activity inhibitory effects of the BC’s residual water soluble polynuclear aromatic hydrocarbons. Thus, the interaction with BC and steer manure application could suppress the release of CO2.
  • Soil Modulation of Ecosystem Response to Climate Forcing and Change Across the US Desert Southwest

    Shepard, Christopher (The University of Arizona., 2014)
    The dryland ecosystems of the US Desert Southwest (SW) are dependent on soil moisture for aboveground productivity; the generation of soil moisture in the SW is dependent on both soil physical properties and climate forcing. This study is one of the first regional point-scale analyses that explores the role of soil physical properties in modulating aboveground vegetation dynamics in response to climate forcing in the SW. Soil texture accounted for significant differences in average aboveground primary productivity across the SW. However, soil texture could not account for differences in inter-annual aboveground productivity variation across the SW. Subsurface soil texture was tightly coupled with precipitation seasonality in accounting for differences in long-term average seasonal aboveground productivity in the Mojave and Sonoran Deserts. The results of this study indicate that the subsurface is a significant factor in modulating aboveground primary productivity, and needs to be included in future modeling exercises of dryland ecosystem response to climate forcing and change.
  • Batch and Column Transport Studies of Environmental Fate of 3-nitro-1,2,4-triazol-5-one (NTO) in Soils

    Mark, Noah William (The University of Arizona., 2014)
    NTO (3-nitro-1,2,4-triazol-5-one) is one of the new explosive compounds used in insensitive munitions (IM) and developed to replace traditional explosives, TNT and RDX. Data on NTO fate and transport is needed to determine its environmental behavior and potential for groundwater contamination. In this study, we measured how NTO in solution interacts with different types of soils and related soil properties to transport and fate behavior. We conducted a series of kinetic and equilibrium batch soil sorption experiments and saturated column transport studies under steady-state and transient conditions. NTO adsorbed very weakly to the studied soils. Adsorption coefficients (Kds) measured for NTO in a range of soils in batch experiments were less than 1 cm³ g⁻¹. There was a highly significant negative relationship between measured NTO adsorption coefficients and soil pH (P = 0.00011). In kinetic experiments, first order transformation rate estimates ranged between 0.0004 h⁻¹ and 0.0221 h⁻¹. There was a general agreement between batch and column-determined fate and transport parameters. However, transport studies showed an increase in the NTO transformation rate as a function of time, possibly indicating microbial growth.
  • Water Quality Assessment of the Santa Cruz River in Southern Arizona

    McOmber, Todd Christian (The University of Arizona., 2014)
    Utilization of areas adjacent to rivers for agricultural and industrial purposes can have detrimental effects on water quality and can potentially impact human and ecosystem health downstream. In this study we tested water quality along a stretch of the effluent-dependent Santa Cruz River near Nogales, AZ. This stretch of river has historically been impaired, but prior to upgrades to the Nogales International Wastewater Treatment Plant (NIWTP) in 2009. Our work endeavored to assess water quality according to the Arizona Department of Environmental Quality (ADEQ) standards, and identify sources of pollution entering the river system. Heavy metals were analyzed via ICP. Three IDEXX quantification systems were used to detect E. coli, Enterococcus, and P. aeruginosa as fecal indicators or potential threats to public health. Potential fecal sources were analyzed using quantitative PCR targeting Bacteroides DNA markers for total, human, and bovine feces (Allbac, HF183, and CowM2, respectively). The NIWTP effectively removed chemical and biological contaminants. The lowest E. coli counts occurred at the site located at the NIWTP outfall (mean = 5 MPN/100ml) while the highest counts (mean = 348 MPN/100 ml) came from Nogales Wash, a tributary receiving untreated flow from Nogales, Mexico. The Allbac marker was detected in all samples, while approximately 97% of samples tested positive for HF183 and 33% tested positive for the CowM2 marker. Continued monitoring of effluent effects on river quality and evaluation of water quality degradation will lead to improvements in the management of Arizona's riparian areas and will ultimately contribute to healthy water bodies.
  • Sodium and potassium relationships in safflower

    Amorim Silva, Murilo Cesar, 1930- (The University of Arizona., 1972)
  • Does Increasing Solids Retention Time During the Wastewater Treatment Process Affect the Persistence of Antibiotic Resistance Genes?

    Walston, Stefan Eugene (The University of Arizona., 2013)
    Antibiotic resistance (AR) is reducing options for effective treatment of bacterial infections for clinically ill patients throughout the world. Our investigation examined the impact solids retention time (SRT) may have on the degradation of antibiotic compounds, proliferation of AR bacteria, and the persistence of antibiotic resistance genes (ARGs) during the wastewater treatment process. Results indicate the presence of ARGs related to clinically relevant antibiotics. Data analysis showed that antibiotic classes exhibit different removal efficiencies in the biological treatment processes (i.e. SRT); therefore, operating conditions at each WWTP can be optimized for highest efficiency removal. SRT of 19 days and higher indicated a high removal efficiency for all six ARGs of concern. Ultimately, identifying a critical value to optimize SRTs, where antibiotic degradation is maximized and AR is minimized, will provide information to WWTP operators, allowing treatment optimization to decrease harmful loading of Trace Organic Contaminants (TOrCs) in the environment.
  • Measuring Air-Water Interfacial Area in Unsaturated Porous Media Using the Interfacial Partitioning Tracer Test Method

    El Ouni, Asma (The University of Arizona., 2013)
    Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (A(ia)).This study used the standard approach comprising tracer injection under steady unsaturated-flow conditions with a uniform water-saturation distribution within the column. Sodium dodecylbezene sulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning and nonreactive tracers, respectively. Three types of porous media were used for the study: a sandy soil, a well-sorted sand, and glass beads. Initial water saturations, S(w), were approximately 80%, 80%, and 26 % for the soil, sand, and glass beads, respectively. Water saturation was monitored gravimetrically during the experiments. The maximum interfacial areas (A(ia)/(1-S(w))) calculated from the results of the experiments are compared among the three porous media used in this work, and compared to previous air-water interfacial area studies.
  • Quantifying catchment scale soil variability in Marshall Gulch, Santa Catalina Mountains Critical Zone Observatory

    Holleran, Molly E. (The University of Arizona., 2013)
    The quantification and prediction of soil properties is fundamental to further understanding the Critical Zone (CZ). In this study we aim to quantify and predict soil properties within a forested catchment, Marshall Gulch, AZ. Input layers of soil depth (modeled), slope, Saga wetness index, remotely sensed normalized difference vegetation index (NDVI) and national agriculture imagery program (NAIP) bands 3/2 were determined to account for 95% of landscape variance and used as model predictors. Target variables including soil depth (cm), carbon (kg/m²), clay (%), Na flux (kg/m²), pH, and strain are predicted using multivariate linear step-wise regression models. Our results show strong correlations of soil properties with the drainage systems in the MG catchment. We observe deeper soils, higher clay content, higher carbon content, and more Na loss within the drainages of the catchment in contrast to the adjacent slopes and ridgelines.
  • The Assessment of Escherichia coli as an Indicator of Microbial Quality of Irrigation Waters used for Produce

    Brassill, Natalie A. (The University of Arizona., 2013)
    Escherichia coli is a bacterial species that lives in the gut of all warm-blooded animals, fish, birds as well as reptiles and is commonly used as an indicator of fecal contamination in water. This project assessed currently used culture based media for the detection of E. coli in irrigation waters used in Arizona and California, and will present recommendations towards the most reliable media for the evaluation of irrigation waters used for produce. Currently, no microbial indicator standards exist for irrigation waters used for produce production in the United States. The produce industry suggests that the recreational water standard guideline (126 E. coli/100 ml) established by the United States Environmental Protection Agency (USEPA) be used. There is concern that the false positive rate of E. coli detection may be high in these waters giving false indications of the level of risk from enteric pathogens. This project evaluated three commercially available media for E. coli detection to test irrigation waters from three agricultural areas (Yuma and Maricopa, AZ and Imperial Valley, CA) and then assessed false positive rates by utilizing Polymerase Chain Reaction (PCR) and DNA sequencing of the bacterial isolates. The media that were chosen for evaluation were (1) MI Agar, (2) IDEXX Colilert Quanti-Tray® and (3) m-ColiBlue24® broth, all evaluation media accepted by the USEPA and widely used in the monitoring of irrigation water quality by the produce industry. Four hundred and fifty 1-L irrigation water grab samples were collected between March 2012 and November 2012. The samples were analyzed for both cultural counts and water quality parameters including temperature, salinity and pH. Isolates positive and negative for E. coli were then selected and assessed utilizing PCR and DNA sequencing. The false positive rate of each method was found to be high, with MI Agar, m-ColiBlue24® broth and the IDEXX Colilert Quanti-Tray® at an accuracy of 67%, 72%, and 51% respectively. A false positive result is reported when presumptive E. coli sub cultured from the media is found to be non-E. coli through molecular analysis. Overall the IDEXX Colilert Quanti-Tray® performed at a greater rate of accuracy than the other two media evaluated, however, high false positive rates may lead to inaccurate assessment of water quality.

    ABRAHAMS, JONATHAN ERIC (The University of Arizona., 1984)
    Field trials were conducted in Tucson, Arizona to evaluate the effects of certain aspects of water and crop management on germination and stand establishment of directly seeded guayule (Parthenium argentatum), using drip irrigation. In a study in May, 1983, seed cover and seed placement were the principle experimental variables, under three irrigation frequencies and two water levels. Vermiculite covered seed plots had significantly more germination than the non-covered plots. Germination was higher in seed rows placed at 4 cm from the drip line than at 9 cm. In a study in October, 1983, irrigation frequency, irrigation water level, and seed placement were analyzed for their effect on stands during germination and post-emergence phases of growth. Significant differences were found as a result of seed placement and it's interaction with irrigation water level. Highest stands occurred under the low water level treatment, with seeds placed at a distance of 5 cm from the drip line.
  • Nitrous oxide emissions from desert region soils

    Guilbault, Michael Roland, 1967- (The University of Arizona., 1993)
    This study was conducted to determine emission rates of nitrous oxide (N₂O) gas from arid region locations. Fluxes were measured at an effluent-irrigated turfgrass location in Arizona, a Sonoran desert location, and a savannah location in Africa. Fluxes were measured by a closed chamber method at the Arizona locations on a weekly basis during the summer of 1991, and at the African location during two separate three day studies during the summer of 1992. Soils were sampled at each location during each sampling period and analyzed for water content, nitrate, pH, and total organic carbon content. Nitrous oxide fluxes in Arizona averaged approximately 13 and 0.7 kg N₂O-N ha⁻¹ yr⁻¹ for the turfgrass and desert locations respectively. The average fluxes from the African sites were 1.3, 1.6, and 1.3 kg N₂O-N ha⁻¹ yr⁻¹ for a millet field, fallow field, and "tigerbush" plateau, respectively. Diurnal and seasonal variability was observed.
  • Response of two desert shrubs to nitrate

    Hines, Stefani Dawn, 1970- (The University of Arizona., 1998)
    The response of two native Arizona plants, fourwing saltbush (Atriplex canescens) and greasewood (Sarcobatus vermiculatus), to five concentrations of nitrate (tap water only, 50 mg/L, 100 mg/L, 750 mg/L, and 2000 mg/L as nitrate) is investigated. Their growth, transpiration, and nitrate and percent nitrogen tissue concentrations were measured. All of the plants' responses were affected by nitrate concentration. In general, it can be concluded that both fourwing saltbush and greasewood tolerated nitrate concentrations as high as 2000 mg/L. However, greasewood's optimal growth was at Level 4 (750 mg/L nitrate) and its tissue nitrate approximately doubled from an average of 572 ± 255 mg/kg at Level 4 to 1020 ± 511 mg/kg at Level 5 (2000 mg/L nitrate). Fourwing saltbush demonstrated a remarkable ability to tolerate large quantities of nitrate and convert it to organic nitrogen at high concentrations. Fourwing saltbush's largest dry mass, 14.48 ± 2.03 g, was at 2000 mg/L of nitrate.
  • The effect of microorganisms on soil structure development in copper mine tailing

    Turk, Colleen Mary, 1961- (The University of Arizona., 1995)
    Organic matter amendments have long been known to improve native organic matter content, aggregation and structure of soils. In the laboratory, however, organic matter amendments to autoclaved soils have no such effect. This may explain the failure of many reclamation attempts on mine tailing wastes, which often proceed without regard for the microbiological processes necessary for soil formation and cycling of plant nutrients. In this study, incubation of tailing waste with soil microbes and a simple carbon source proved sufficient to increase the formation of water stable aggregates from tailing particles. Autoclaved control samples showed no change in aggregation. The incorporation of microbial cell mass into the mineral matrix of the tailing was observed using scanning electron microscopy. These results suggest that microbial activity is necessary in order to incorporate organic matter into the abiotic matrix of tailing, promoting aggregation and ultimately soil formation from this material.

    Ebinger, Michael Howard (The University of Arizona., 1984)

    Morse, Sandra Lynn, 1957- (The University of Arizona., 1982)
  • Selenium uptake and it's effect on growth of carrots, squash, and sudan grass

    Algharaibeh, Mamoun A., 1969- (The University of Arizona., 1996)
    A greenhouse pot experiment was conducted to study the amount of selenium accumulation and the effect of selenite on growth of carrots, squash, and sudan grass. Selenium was added to sandy soil as sodium selenite at five rates (0.02, 0.08, 0.32, 1.28, and 5 mgn) in a randomized complete block design including a control, in three replicates. Addition of 5 mg/l selenium reduced the total biomass (in carrots and squash) as much as 97% and as much as 85% in sudan grass. Crops in the control treatment and those exposed to 0.02 mg/l did not accumulate selenium to levels considered toxic to animals and humans. All other treatments resulted in levels of accumulation that could pose hazards when consumed by animals and humans. Based on the interpolated irrigation concentration that caused 50% yield reduction (observed data), sudan grass was the most tolerant crop (4.0 mg/l)while squash plants were the least tolerant (0.9 mg/l) and carrots were intermediate (2.2 mg/l).
  • Sorption and transport characteristics of cadmium and dissolved natural organic matter with a coarse loamy soil

    Milczarek, Michael Arthur, 1962- (The University of Arizona., 1994)
    Various humic substances were reacted with a coarse loamy soil in both batch studies and column experiments. Solution pH was not buffered, rather monitored to more closely approximate a "real life" scenario. Humic substances were also reacted with soil that had been pre-saturated with various concentrations of cadmium nitrate solution. The batch experiments were characterized by interference from antecedent natural organic matter in the soil, causing high nonlinearity in the data. Humic substance sorption in the column experiments was characterized by early breakthrough of a small fraction, followed by long extended tailing. Complete breakthrough was never observed in any of the column studies. Sorption phenomena is believed to be primarily controlled by the structural configuration of the humic substances, with solution pH and the valence of cations in the electrolyte solution having the greatest effect on sorption. Implications to humic substance transport in natural systems will be discussed.

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