Rasmussen, Craig; Yamafuji, Kazumasa; Rasmussen, Craig; Artiola, Janick; Rasmussen, Craig; Walworth, James (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.
    • Water Quality Assessment of the Santa Cruz River in Southern Arizona

      Rock, Channah M.; McOmber, Todd Christian; Rock, Channah M.; McLain, Jean; Curry, Joan E. (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.
    • Soil Modulation of Ecosystem Response to Climate Forcing and Change Across the US Desert Southwest

      Rasmussen, Craig; Shepard, Christopher; Crimmins, Michael; Schaap, Marcel (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

      Dontsova, Katerina; Brusseau, Mark; Mark, Noah William; Dontsova, Katerina; Brusseau, Mark; Curry, Joan (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.
    • 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.
    • Does Increasing Solids Retention Time During the Wastewater Treatment Process Affect the Persistence of Antibiotic Resistance Genes?

      Rock, Channah; Walston, Stefan Eugene; McLain, Jean; Abrell, Leif; Gerrity, Daniel (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.
    • 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.
    • 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.
    • Deficit Irrigation of Bermudagrass and Seashore Paspalum for Golf Course Turf

      Walworth, James L.; Brown, Paul W.; Kopec, David M.; Bañuelos, Jaime; Walworth, James L. (The University of Arizona., 2010)
      We compared water deficit responses of 'Tifsport', 'Tifway 419', 'Tifgreen 328', and 'MidIron' bermudagrass (Cynodon dactylon x Cynodon transvaalensis), and 'SeaSpray', 'SeaDwarf', and 'Sea Isle 1' seashore paspalum (Paspalum vaginatum Swartz) under a linear gradient irrigation system in the desert Southwest. Target irrigation levels were 100, 80, 60, and 40% (2009) and 100, 80, 70, 60, and 40% (2010) of standard reference evapotranspiration (ETo). Actual water applied (including rainfall) was 100%, 83%, 66%, and 49% of ETo (2009) and 100%, 83%, 75%, 66%, and 49% (2010). Canopy temperatures increased, and quality and dry matter production declined with reduced irrigation. For optimum turfgrass quality, 75 to 83% ETo replacement was required; for acceptable quality turfgrass, 66 to 75% ETo replacement was needed for bermudagrass, and 75 to 80% ETo for seashore paspalum. Spring green-up was delayed by drought. Bermudagrasses, particularly 'MidIron', performed better than seashore paspalums under water stress conditions.
    • Soil Testing and Plant Analysis Relationships for Irrigated Chile Production

      Silvertooth, Jeffrey; Babcock, Esther; Silvertooth, Jeffrey; Brown, Paul; Walworth, James (The University of Arizona., 2010)
      In a field study of irrigated chile (Capsicum annum L.) production in southeastern Arizona and southwestern New Mexico from 2008 through 2009, soil and tissue test samples were analyzed for a full spectrum of nutrients at 16 different sites, including nitrogen (N) phosphorus (P), potassium (K), zinc (Zn), iron (Fe), and boron (B), with the objective of evaluating soil and tissue nutrient testing procedures and establishing basic testing guidelines and recommendations with respect to yield potentials. Results for soil and tissue analysis were correlated to yield results. The results provide estimates for baselines which can be tested through subsequent calibration experiments for the development of recommendations for critical soil and tissue test values. These soil test and plant nutrients values will be evaluated in subsequent experiments in an effort to better define fertilizer nutrient inputs in order to gain better nutrient management efficiencies in irrigated chile production systems.
    • Digital Soil-Landscape Classification for Soil Survey using ASTER Satellite and Digital Elevation Data in Organ Pipe Cactus National Monument, Arizona

      Rasmussen, Craig; Nauman, Travis William; Rasmussen, Craig; van Leeuwen, Willem J.; Guertin, Phillip D. (The University of Arizona., 2009)
      Digital soil mapping supervised and unsupervised classification methods were evaluated to aide soil survey of unmapped areas in the western United States. Supervised classification of landscape into mountains and basins preceded unsupervised classification of data chosen by iterative data reduction. Principal component data reduction, ISODATA classification, Linear combination of principal components, Zonal averaging of linear combination by ISODATA class, Segmentation of the image into polygons, and Attribution of polygons by majority ISODATA class (PILZSA process) comprised steps isolating unique soil-landscape units. Input data included ASTER satellite imagery and USGS 30-m elevation layers for environmental proxy variables representing soil forming factors. Results indicate that PILZSA captured general soil patterns when compared to an existing soil survey while also detecting fluvial soils sourced from different lithologies and unique mountain areas not delineated by the original survey. PILZSA demonstrates potential for soil pre-mapping, and sampling design efforts for soil survey and survey updates.
    • Vegetation Controls on the Dynamics and Quality of Soil Organic Carbon in an Arid, Hyperthermic Ecosystem

      Rasmussen, Craig; White II, David Allen; Rasmussen, Craig; Chorover, Jon; Walworth, James (The University of Arizona., 2008)
      Arid lands comprise vast regions of terrestrial land, highlighting the importance of understanding their role in the global carbon cycle. The objective of this study was to determine the effect of Prosopis velutina (mesquite), Larrea tridentata (creosote) and a combination of Bouteloua barbata, Bouteloua aristidoides, Aristida adscensionis, and some Cynodon dactylon (mixed grass) vegetation types on soil organic carbon (SOC) dynamics and quality in an arid, hyperthermic ecosystem of southern Arizona. This was accomplished by quantifying vegetation type control over: (i) local scale SOC stocks; (ii) soil aggregate stability; (iii) SOC turnover and microbial community composition; (iv) the distribution of SOC in physically defined fractions; and (v) the thermal nature and composition of SOC. The results from this study demonstrated significant variation in SOC dynamics and quality between vegetation with potential feedbacks to SOC sequestration of atmospheric CO₂.
    • Mobilization of Lead and Zinc in Acid Sulfate Mine Tailings

      Chorover, Jon; Vazquez-Ortega, Angelica; Chorover, Jon; Maier, Raina; Rasmussen, Craig (The University of Arizona., 2008)
      In this thesis, column experiments were conducted in order to determine the effect of irrigation with local groundwater on mobilization of lead and zinc in 50 years old sulfate-acid mine tailings. In addition, the influence of soluble oxalic acid, a common rhizosphere organic acid, was assessed by varying its concentration across an environmentally relevant range. In general, metal contaminant dissolution was not affected by the presence of oxalic acid. In both tailings, Zn mobilization was higher than Pb suggesting the presence of more kinetically labile Zn phases, regardless of the treatment used. Lead mobilization was also low because effluent solutions were near to equilibrium conditions with respect to gypsum, preventing Pb dissolution from Pb-sulfate minerals. Geochemical modeling also indicated that lead release was controlled by anglesite and plumbojarosite dissolution. Zinc release appears to be controlled by Zn-talc and goslarite.
    • Evapotranspiration, Consumptive Water Use, And Responses To Self-Imposed Drought Of Three Warm Season Grasses Grown In A Semi-Arid Region

      Walworth, James L; Henry, William Nathan; Walworth, James L (The University of Arizona., 2007)
      Evapotranspiration rates (ET) and consumptive water use (CWU) were measured for three desert turfgrasses using weighing lysimeters with a calcined clay growth medium. Water use rates were compared over a two-year study for 'Sea Isle I' seashore paspalum (Paspalum vaginatum) and A138 desert saltgrass (Distichlis spicata), along with 'Tifway' bermudagrass (Cynodon dactylon x Cynodon transvaalensis). Saltgrass showed elevated leaf canopy temperatures for extended periods before exhibiting visible wilt symptoms while 'Tifway' bermudagrass and seashore paspalum wilted readily, even at relatively high soil water contents. Saltgrass transpired for 11.9 d on average before drought stress was observed. Seashore paspalum maintained leaf turgor, on average 5.6 d without irrigation, whereas 'Tifway' bermudagrass averaged 4.0 d before requiring irrigation. The two-year average Kc values for three grasses before self-imposed drought was expressed by visible leaf wilting were 0.85, 0.79, and 0.74, for A138 saltgrass, 'Sea Isle I' seashore paspalum, and 'Tifway' bermudagrass, respectively.
    • Field Measurement of the Soil-Water Storage Capacity of Evapotranspiration Covers Using Lysimeters.

      Chartrand, Shawna Lee.; Glenn, Edward P. (The University of Arizona., 2004)
      Three soils were tested as possible substrates for an evapotranspiration cover for a Uranium mill tailings disposal site in Moab, Utah. Small weighing field lysimeters were used to determine the field capacity of soils with the effect of a coarse-grained capillary barrier placed beneath the soil to increase water retention. Water was ponded on each lysimeter and then covered with plastic to prevent evaporation. Lysimeters were drained and weighed periodically throughout the experiment. Field capacity was determined by the weight of the lysimeter when drainage stopped. Results were compared to a mathematical model for estimating water storage of capillary barriers. Results from particle size analyses were also compared to water storage results and we found that both sand and clay were significant factors (p <0.05) in explaining water storage. After determining the water-holding capacity of the soils, recommendations on the most suitable soil for the Moab evapotranspiration cap will be made.
    • In Situ Characterization of Unsaturated Soil Hydraulic Properties at the Maricopa Environmental Monitoring Site

      Graham, Aaron Robert; Wierenga, Peter J. (The University of Arizona., 2004)
      Characterization of the unsaturated hydraulic properties is fundamental in modeling soil water flow and contaminant transport in the vadose zone. The objective of this study was to develop a database of in situ determined unsaturated hydraulic properties for a 50 x 50 meter field site. Two infiltration experiments were conducted. Neutron probe and tensiometers were used to determine soil water content and soil water potential to a depth of 10 meters throughout the irrigation and redistribution phases of both experiments. Unsaturated hydraulic conductivity was determined from changes in soil water content using the instantaneous profile method with a simplified unit gradient approach. Hydraulic properties determined from the redistribution phase of experiment 1 were evaluated by means of a one-dimensional forward simulation of wetting front arrival times at the 3, 5 and 10 m depths for experiment 2. It was found that predictions of wetting front arrival times at 10 m were late by an average of 15%. The hydraulic gradient averaged 0.97 throughout the redistribution phase of experiment 1, thus the unit gradient assumption, used to determine unsaturated hydraulic properties for nine locations and 40 depths within the 50 x 50 m field plot, was justified for this deep layered profile.
    • Integrative Aquaculture and Agriculture: Nitrogen and Phopshorous Recycling in Maricopa, Arizona.

      Stevenson, Kalb T.; Fitzsimmons, Kevin; Clay, Patrik (The University of Arizona., 2003)
      A study was conducted in Maricopa, AZ over three field cropping seasons from December 2001 through April 2003 in order to determine the effects of fish effluent irrigations on field crops and to determine the sustainability of nutrient recycling through an integrative aquaculture-agriculture system. Treatments were designed to compare current fertilization and irrigation methods to possible integrative strategies in order to conserve natural resources. The discharged outflow from two sources of irrigation water, (well water and effluent from a fish pond/reservoir), were tested throughout the duration of the study. Maricopa's NO3-rich well water, was consistently found to contain slightly higher total N concentrations than the fish effluent, which contained higher NH4, organic N, and PO4 concentrations. Unfavorable spatial distribution of pond sludges (containing significantly higher amounts of N and P than well water) resulted in the remainder of large stores of nutrients along the pond bottom. Because a nutrient sink was created within these pond reservoirs, fish effluent irrigations were found to have no significant effect on cotton or barley yields. Vegetative plant growth, however, was significantly affected in several instances, probably by the slow, yet advantageous process of organic matter degradation near soil surfaces. Any significant increases in vegetative growth were found only in effluent-irrigated plots and occurred later in crop seasons. Analysis of the pond sludge confirmed that if pond sediments could be more efficiently removed and applied to land, the benefits from such an integrative system could have great ecological and financial benefits (i.e. decreasing chemical fertilizer use, using water to a greater potential, producing an extra crop of fish, and having lower fertilization costs).
    • Application of the Hillslope Erosion Model to predict annual sediment yield in Southwest New Mexico.

      King, Chad Eric.; Fitzsimmons, Kevin (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.
    • Addressing State Funding Assistance Through the Arizona State Aquatic Nuisance Species Management Plan: An Exercise in Policy Writing.

      King, Chad Eric.; Fitzsimmons, Kevin (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.