Browsing by Author "Dean Hesterberg, Committee Member"

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Adaptation of the PourThru Nutrient Extraction Procedures to Greenhouse Crop Production
(2002-11-15) Cavins, Todd J.; John Dole, Committee Member; Ted Bilderback, Committee Co-Chair; Bill Fonteno, Committee Member; Keith Cassel, Committee Member; Brian Whipker, Committee Co-Chair; Dean Hesterberg, Committee Member
The purpose of this research was to adapt the PourThru nutrient extraction technique, which is the displacement of the bulk solution from the production container without a destructive harvest, to commercial greenhouse crop production. PourThru is a quick and easy nutrient sampling technique that is not laboratory oriented and can help prevent costly nutritional problems for greenhouse crop producers. Additionally, time domain reflectometry (TDR) was evaluated as an experimental tool to measure substrate moisture content, which may affect PourThru extraction. Time domain reflectometry is quick, non-destructive and has potential for use in automation of moisture content determination in greenhouse production. Previous PourThru research had focused on techniques for use on large nursery containers (≈ 3800 cm3) versus the smaller floriculture containers (≈ 1500 cm3) and no exact calibration of PourThru nutrient values to saturated media extract (SME) values, the current standard for nutrient testing, had been completed. Therefore, studies were implemented to examine the relationship of PourThru to SME, evaluate irrigation systems and timing effect on PourThru results as well as develop recommended influent and leachate volumes to ensure an unadulterated sample. Calibration curves were developed between PourThru and SME values and r2 values ranged from 0.91 to 0.99 for linear relationships. Irrigation systems did affect electrical conductivity (EC) values and alternative interpretive standard values were developed dependent upon irrigation system. Timing of the PourThru was important to ensure adequate leachate was collected for sample analysis and the amount of influent affected EC values and the amount of leachate collected. The use of TDR was effective in small containers (980.6 and 2177.5 cm3); however, care should be taken to match probe size to container size to ensure representative sampling. The largest limitation to TDR use was the bulk density of the substrate being analyzed. Approximately a 50 to 75% underestimation occurred when substrate bulk densities were below 1.2 g.cm-3, but material specific calibration improved TDR accuracy to within 4%.
Alternative Substrates for Estimating TCE-degrading Capabilities of Toluene-oxidizing Bacteria
(2002-07-24) Hicks, Kristin Adair; Dean Hesterberg, Committee Member; Deanna Osmond, Committee Co-Chair; Michael R. Hyman, Committee Co-Chair
One of the primary impediments to the implementation of bioremediation is uncertainty about success in the field. Soils and microbial populations are heterogeneous and it is difficult to extrapolate biodegradation rates from small samples to field scale. While biodegradation rates can be estimated from microcosm studies, in situ methods offer a more meaningful gauge of resident microbial activity. One method used to estimate biodegradation rates in the field is the newly developed Push-Pull technique. While this technique can be conducted on site, it is normally not possible to use target pollutants as the reactive substrates. Consequently, alternative, benign reactive tracers must be used. Ideally, these alternative, reactive tracers interrogate the same enzyme systems that are responsible for the biodegradation of the target pollutant. The objective of this study was to develop a reactive tracer system that could be used to assess toluene-dependent trichloroethylene (TCE) degradation. Our approach has been to determine whether a series of pure strains of toluene-oxidizing bacteria (Burkholderia cepacia G4, Pseudomonas putida F1, Pseudomonas putida mt2, Pseudomonas mendocina KR1), each with different toluene-oxidizing enzymes systems, are capable of cometabolically oxidizing a series of eleven potential alternative substrates. These substrates include simple alkenes, alkanes, and cyclic alkanes. The kinetics (Ks and Vmax) of the biotransformation of these compounds have been determined. While oxidation products were observed for a number of these substrates in connection with one or more of the test organisms, isobutylene was co-oxidized by all test organisms. Oxidation of isobutylene by each organism yielded kinetics constants comparable to the corresponding kinetics of TCE degradation. The enzyme system expressed by Burkholderia cepacia G4 catalyzed the epoxidation of isobutylene while the remaining enzyme systems catalyzed allylic alcohol formation. Isobutylene has potential in field scale Push-Pull studies as a tool for evaluating rates of aerobic toluene-dependent TCE degradation and of differentiating the relative contributions of the TCE-degrading population. A pilot study of this alternative substrate at Edwards Air Force Base will test whether it can be used successfully to estimate in situ degradation of TCE. Analysis of isobutylene oxidation products in toluene-enriched ground water may offer an inexpensive and effective method of measuring the degradation of TCE at contaminated sites nationwide.
Establishment and Stabilization of pH in Container Root Substrate.
(2010-07-23) Jeong, Ka Yeon; Paul Nelson, Committee Chair; Dean Hesterberg, Committee Member; Brian Whipker, Committee Member; Wei Shi, Committee Member; Markus Peterson, Committee Member
Impact of Management and Texture on Soil Organic Matter Fractions
(2007-12-20) Gruver, Joel Brooks; Michael Wagger, Committee Co-Chair; Shuijin Hu, Committee Co-Chair; Dean Hesterberg, Committee Member; Wei Shi, Committee Member
Growing concerns about elevated levels of atmospheric CO2 and associated climate change have increased interest in soil C. While general increases in the adoption of conservation management practices may result in C sequestration, efficient utilization of soil as a C sink will require identification of soils with high potential for sequestration and improved methods of monitoring soil C. The objectives of this research were to: 1) evaluate the historical roots, experimental validation and subsequent impact of the C saturation relationships proposed by Jan Hassink, 2) evaluate the effects of management and texture on aggregation and C fractions using soil from two long term experiments, 3) develop new methods of structural disruption and physical fractionation that address shortcomings in existing methods, 4) evaluate the impact of antecedent C on C and aggregate dynamics and 5) evaluate the simplified MnoxC method proposed by Weil et al. (2003). Collectively, the literature we reviewed did not support broad application of simple C saturation relationships such as those proposed by Hassink but did support selective use of fine mineral content as an indicator of C storage capacity. Results from two incubation experiments demonstrated the modulating effect of antecedent C on soil C and aggregate dynamics following structural disruption and residue addition. Positive effects of residue and structural disruption on aggregation were greatest in soil with low antecedent C. Residue decomposed more rapidly in soil with high antecedent C but had a greater priming effect in soil with low antecedent C. Addition of a 15N labeled nitrate source revealed that immobilization of nitrate-N within microaggregates is a minor process irrespective of structural disruption and antecedent C. Carbon contained in microaggregates within stable macroaggregates from an organic transition experiment was sensitive to C input regime but unrelated to fine mineral content. Strong tillage system effects on C fractions, aggregation and texture (tillage intensity↑ = ↓C, aggregate stability and sand content) were identified in soil from a long term tillage system study. Permanganate oxidizable C (Weil method) was found to be a sensitive indicator of management effects on soil C particularly after correction for non-linearity.
Phosphate Binding and Fe(III) Reduction as Affected by Fe(III) and Organic Matter Interactions.
(2010-10-22) Kizewski, Fiona; James Martin, Committee Chair; Jerry Whitten, Committee Member; Dean Hesterberg, Committee Member; Paul Maggard, Committee Member; Joseph Burton, Committee Member
Production of Co-Siderophore Complexes by Ligand-Promoted Dissolution
(2009-07-13) Bi, Yuqiang; Owen Duckworth, Committee Chair; Dean Hesterberg, Committee Member; Detlef Knappe, Committee Member
Recent research indicates that siderophores, a class of biogenic ligands with known exceptional affinity for Fe(III), can also strongly complex Co(III), an element essential to normal metabolic function of microbes and animals. This study was conducted to examine the siderophore-promoted dissolution rates and mechanisms of Co from model synthetic Co-bearing minerals to elucidate the role of siderophores in biogeochemical processes of Co. Dissolution of heterogenite (CoOOH) and four Co-goethites (Co-FeOOH) with different levels of Co substitution were investigated in the presence of a trihydroxamate siderophore, desferrioxamine B (DFOB), using batch and flow-through experiments, respectively. By measuring the complex and total metal concentrations in dissolution products, dissolution rates via multiple pathways were measured as a function of pH. Results showed that DFOB promoted dissolution of Co from Co-bearing minerals via pH-dependent mechanisms. For heterogenite, ligand-promoted dissolution was the dominant pathway at neutral to alkaline pH, while reductive dissolution became dominant for pH < 6. Cobalt substitution in Co-goethite resulted in increased total dissolution rates of both Co and Fe, but ligand-promoted and reductive Co dissolution pathways were difficult to examine due to the slow dissolution rates. The fast dissolution rate of heterogenite, coupled with the high affinity of Co(III) for DFOB, suggests that siderophore-promoted dissolution of Co(III) oxides is a biogeochemically favorable process. Although the association of Co with Fe oxide mineral may limit the Co dissolution rate, siderophore-promoted Co dissolution may still be an effective enough way to increase Co bioavailability. The results also suggest the possibility of radionuclide 60Co by siderophores from recalcitrant Fe oxide phases, which may be important to the fate and transport of 60Co in contaminated environments.
Removal of 2-Methylisoborneol and Geosmin by High-Silica Zeolites and Powdered Activated Carbon in the Absence and Presence of Ozone.
(2010-08-26) Yuncu, Bilgen; Detlef Knappe, Committee Chair; Joel Ducoste, Committee Member; Francis Lajara De Los Reyes, Committee Member; Dean Hesterberg, Committee Member
Soybean Root Growth in Acid Subsoils in Relation to Magnesium Additions and Soil Solution Chemistry
(2006-05-30) Hashimoto, Yohei; Daniel W. Israel, Committee Member; Paul V. Nelson, Committee Member; T. Jot Smyth, Committee Chair; Dean Hesterberg, Committee Member
Aluminum tolerance of soybean [Glycine max (L.) Merr.] by citrate secretion from roots, leading to external complexation of toxic Al species in solution, is enhanced by addition of μM Mg²⁺ to hydroponic solutions. The objectives of this dissertation were to assess ameliorative effects of μM Mg additions on soybean root growth in acidic subsoils and to relate the soil solution ionic compositions to soybean root growth. Roots of soybean cultivar Plant Introduction 416937 extending from a limed surface soil compartment grew for 28 days into a subsurface compartment containing acid subsoils [Cecil (oxidic and kaolinitic), Creedmoor (montmorillonitic) and Norfolk (kaolinitic)]. The three Mg treatments consisted of the native equilibrium soil solution concentrations in each soil (50 or 100 μM) and MgCl₂ additions to achieve 150 and 300 μM Mg (Mg150, Mg300, respectively) in the soil solutions. Root elongations into Mg-treated subsoils were compared with a CaCO₃ treatment limed to achieve a soil pH value of 5.5. Subsoil root length for the treatments without added Mg or lime decreased in the order of the Cecil followed by Norfolk and Creedmoor subsoils, and corresponded to the increasing order of percent Al saturation (27, 61 and 83%, respectively). Subsoil root growth and dry matter responses to the Mg treatments were less than the lime treatments, and there were no differences for the Mg150 and Mg300 treatments as compared to the treatments without added Mg or lime. Citrate adsorption experiments found that over 66% citrate added in the subsoils were adsorbed and biodegraded, suggesting that root secreted citrate in the soil might readily be unavailable to complex Al for ameliorating its rhizotoxicity. Root length relative to the limed treatments for all subsoils (RRL) was poorly related to the activity of soil solution Al species (Al³⁺ and Al-hydroxyl species) and Mg²⁺. However, the RRL values were more closely related to the parameters associated with soil solution Ca activity including Ca²⁺, Al³⁺⁄Ca²⁺, and Al³⁺;⁄(Ca²⁺ + Mg²⁺), suggesting that Ca could be a primary factor ameliorating Al and H⁺ rhizotoxicity in these subsoils. Increased tolerance to Al rhizotoxicity of soybean by μM Mg additions to hydroponic solutions, inducing citrate secretion from roots to externally complex toxic Al species, may be less important in the acid subsoil with a poor native Ca available to root growth.