Now showing items 21-40 of 390


      Niebla, Elvia Elisa (The University of Arizona., 1979)

      Bucks, Dale Alan (The University of Arizona., 1979)

      Turjoman, Abdul Mannan (The University of Arizona., 1978)

      Morin, George Cardinal Albert,1943- (The University of Arizona., 1977)
    • Measuring Air-Water Interfacial Area in Unsaturated Porous Media Using the Interfacial Partitioning Tracer Test Method

      Brusseau, Mark L.; El Ouni, Asma; Curry, Joan E.; Zhong, Hua (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

      Rasmussen, Craig; Holleran, Molly E.; Chorover, Jon; Guertin, David P. (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

      Rock, Channah; Brassill, Natalie A.; McLain, Jean E.; Gerba, Charles; Nolte, Kurt (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.
    • Monitoring Microbial Water Quality via Online Sensors

      Pepper, Ian L.; Sherchan, Samendra Prasad; Pepper, Ian L.; Gerba, Charles P.; Snyder, Shane A. (The University of Arizona., 2013)
      To protect public health, detection and treatment technologies have been improved to monitor and inactivate pathogens in drinking water. The goal of this dissertation is to evaluate and utilize multiple online sensors and advanced oxidation processes to document both the detection as well as destruction of microbial contaminants in real-time. Reviews of rapid detection technologies for real-time monitoring of pathogens in drinking water and advanced technologies to inactivate pathogens in water are shown in Appendices A and B. The study in Appendix C evaluated the efficacy of real-time sensors for the detection of microbial contaminants. Bacillus thuringiensis was used in this research as a surrogate for Bacillus anthracis to determine each sensor response and detection capability. The minimum threshold responses of sensors were determined by injecting B.thuringiensis into deionized (DI), raw (unfiltered) tap water, or filtered tap water over a concentration range of 10² - 10⁵ spores/ml. The BioSentry sensor responded to increases in concentration over the range of 10² - 10⁵ spores/ml. Below this range, sensors provided signals undistinguishable from background noise. The select sensors can detect microbial water quality changes, and these advanced technologies can be integrated to monitor intrusion events in water distribution systems. The study in Appendix D evaluated the efficiency of the UV reactor for inactivation of MS2 coliphage. The virus MS2 coliphage (ATCC 15597-B1) has been proposed by the U.S. Environmental Protection Agency as a standard for UV reactor validation in the United States. In addition, MS2 is used as a surrogate for enteric viruses due to its similar size and morphology. Following UV radiation at a flow rate of 2gpm, infective MS2 showed a reduction of 5.3- log₁₀ when quantified with cultural plaque counts, whereas corresponding quantitative polymerase chain reaction (qPCR) data showed only a 1.7- log₁₀ reduction in viral RNA copy number. In contrast, plaque assay revealed a 5.8- log₁₀ inactivation; a slight increase in infective MS2 coliphage reduction at 1 gal per min but qPCR results indicate a 2.8- log₁₀ reduction in viral RNA copy number; a one log more inactivation compared to 2 gpm. When H₂O₂ was added at either 2.5 or 5 mg/l with UV at either flow rate, enhanced MS2 inactivation occurred with a greater than 7 log₁₀ reduction observed via plaque counts, indicating that all added MS2 had been inactivated, since no plaques were formed after incubation at 37°C for 24 hours. Correspondingly, qPCR data only showed a 3-4 log₁₀ reduction in viral RNA copy number. The study in Appendix E utilized online sensor to document the destruction of E.coli and Bacillus thuringiensis spores by UV/H₂O₂ treatment. In this study, Escherichia coli was tested for potential UV/H2O2 treatment in DI water and online sensors were also integrated to monitor the destruction in real-time. Pilot-scale experiments were performed using a Trojan UVSwift SC reactor (Trojan Technologies, London, ON, Canada) at a flow rate of 1 gal./min (gpm). UV radiation and UV/H₂O₂ combination in E.coli cell suspensions resulted in a >6 log₁₀ reduction of the viable counts. Similar exposure to B.thuringiensis spores resulted in a 3 log₁₀ reduction in viable counts. Scanning electron microscopy of the treated samples revealed severe damage on the surface of most E.coli cells, yet there was no significant change observed in the morphology of the B. thuringiensis spores. Following UV/H₂O₂ exposure, the BioSentry sensor showed an increase in the unknown, rod and spores counts, and did not correspond well when compared to viable counts assays. Data from this study show that advanced oxidation processes effectively inactivate E. coli vegetative cells, but not B.thuringiensis spores which were more resistant to UV/H₂O₂.

      Fangmeier, Delmar D.; ABRAHAMS, JONATHAN ERIC; Ray, Dennis; Matthias, Alan D. (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

      Matthias, Allan D.; 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

      Glenn, Edward P.; 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

      Sinclair, Norval A.; 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)
    • Risk assessment of viruses in water

      Gerba, Charles P.; Crabtree, Kristina Dawn, 1968- (The University of Arizona., 1996)
      The human health significance of waterborne viruses has previously relied on epidemiological data from documented waterborne outbreaks. It is difficult, however, to assess the risks involved to individuals and communities from exposure to low levels of contamination. Risk assessment is a useful tool in the interpretation of water quality data and can be used to better understand the significance of exposure to low-level contamination of viruses in water. Microbial risk assessment was applied to determine the risks associated with environmental exposure to waterborne coxsackievirus and adenovirus. Annual risks of infection for drinking water were determined to be as high as 10⁻¹ for both coxsackievirus and adenovirus at exposure levels of 0.13 PFU/l and 0.001 IU/l, respectively. A comprehensive cost-of-illness analysis was conducted for three waterborne viruses--Norwalk virus, rotavirus, and non-polio enterovirus--to determine the economic impact of waterborne viruses in the United States. Annual medical costs and productivity losses were estimated in 1993 dollars using actual outbreak information and data from epidemiological studies. It was estimated that $1.1 to $6.9 billion is spent each year in the United States due to these viral illnesses, with potentially $0.39 to $2.4 billion attributable to water. The United States Environmental Protection Agency (USEPA) has initiated the Information Collection Rule (ICR) in which water utilities serving >100,000 people will be required to collect data on the concentrations of specific microorganisms in source and finished water beginning in 1997. Selected water utilities will be required to archive water samples for possible further viral analyses. A risk assessment approach was undertaken to determine which virus would be appropriate for the analyses of the archived water samples. The following viruses were selected based on the nature of the different diseases associated with each, their occurrence in waterborne outbreaks, and their resistance to inactivation by disinfectants: rotavirus, coxsackievirus, hepatitis A virus, adenovirus, Norwalk and Norwalk-like viruses, astrovirus, and hepatitis E virus. The polymerase chain reaction (PCR) is the recommended detection method. The results of these analyses will provide both a database on the occurrence of these viruses in water as well as their susceptibility to water treatment.
    • An evaluation of DNA fingerprinting methods for subtyping Salmonella

      Pepper, Ian L.; Burr, Mark Daniel, 1949- (The University of Arizona., 1996)
      The use of DNA typing and fingerprinting methods to identify and discriminate strains of bacteria, including Salmonella, has increased dramatically in recent years. Traditional typing methods, including serotyping and phage typing, have often not adequately discriminated strains, nor have they always identified virulent or antibiotic resistant strains. In a literature review, DNA-based methods, including plasmid analysis, restriction fragment length polymorphism (RFLP) analysis, and polymerase chain reaction (PCR) fingerprinting methods were evaluated. Plasmid analysis, including plasmid profiles and plasmid fingerprints have been shown to be useful primarily in short-term investigations of disease outbreak. However, plasmid profiles or possession of individual plasmids have generally not been good indicators of cell phenotypes overall. RFLP fingerprinting of Salmonella utilizing probes from ribosomal DNA, insertion sequence IS200, or random sequences has been reported. Ribotypes detected with ribosomal probes have generally been shared among different serotypes, whereas IS200 profiles have tended to be more serotype-specific. AP PCR and rep-PCR primers have been shown to discriminate Salmonella isolates, but fingerprints have been more difficult to reproduce and interpret than RFLP fingerprints. Several authors have reported bands of varying intensities, and some faint bands have not been reproducible. Improved methods of resolving and detecting PCR products are necessary. In a laboratory study, 85 environmental Salmonella isolates belonging to 22 serotypes were fingerprinted by 16S RFLP ribotyping, by rep-PCR, using ERIC (enterobacterial repetitive intergenic consensus) primers, and by AP PCR. Ribotypes were shared by isolates from different serotypes. ERIC PCR and one AP PCR primer produced fingerprints that discriminated among the different isolates, but did not identify serotypes. Another AP PCR primer produced simple patterns that neither discriminated isolates, nor identified serotypes. In a second related laboratory study, computer-assisted matching of AP PCR fingerprints of several known isolates was evaluated. Aliquots of the PCR reaction were run in the same and different gels, and the fingerprints bands were scored by two technicians on a presence-absence basis, and matched by creating dendrograms. Although replicate fingerprints of an isolate appeared reproducible, they were not always scored identically. Thus, the computer was not always able to correctly match fingerprints.
    • The impact of microbial population dynamics on the transport and biodegradation of organic compounds

      Brusseau, Mark L.; Sandrin, Susannah Kathleen (The University of Arizona., 2001)
      The impact of microbial population dynamics on the biodegradation and transport of organic compounds was evaluated in this study. At the laboratory-scale, results from miscible-displacement studies demonstrated that transport and biodegradation behavior in systems with increasing biologic diversity and population density variation was considerably more variable. Biokinetic parameters associated with biodegradation of the target compound were found to be considerably different in batch versus flow-through systems. While growth rates were always higher in the flow-through systems, the impacts on microbial lag and cell yield were opposite in different soils. In homogeneous sand, microbial lag was longer and column cell yields were larger than values reported under batch conditions. However, in more heterogeneous soils, microbial lag was shorter and column yields were smaller in the flow-through systems. This was determined in part using a one-dimensional contaminant transport and biodegradation model that incorporates the effects of microbial lag, inhibition, bacterial transport and nonuniform distribution of microbes, which was developed as a part of this study. In the second part of this study, a contaminant transport and biodegradation model incorporating linear biodegradation was applied to recovery data from small input pulses of biotracers at the field scale. One field site was low in oxygen and fairly homogeneous. The other had been subjected to a surfactant flush that enhanced oxygen concentrations, and thus microbial population densities, near the injection wells. Application of this model allowed for quantitative determination of the spatial distribution of microbial activity at the field sites.