Browsing by Author "Tick, Geoffrey R."
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Item 1,4-Dioxane cosolvency impacts on trichloroethene dissolution and sorption(Elsevier, 2019) Milavec, Justin; Tick, Geoffrey R.; Brusseau, Mark L.; Carroll, Kenneth C.; New Mexico State University; University of Alabama Tuscaloosa; University of ArizonaSolvent stabilizer 1,4-dioxane, an emerging recalcitrant groundwater contaminant, was commonly added to chlorinated solvents such as trichloroethene (TCE), and the impact of co-disposal on contaminant transport processes remains uncertain. A series of batch equilibrium experiments was conducted with variations of 1,4-dioxane and TCE composition to evaluate aqueous dissolution of the two components and their sorption to aquifer sediments. The solubility of TCE increased with increasing amounts of 1,4-dioxane, indicating that 1,4-dioxane acts as a cosolvent causing solubility enhancement of co-contaminants. The solubilization results compared favorably with predictions using the log-linear cosolvency model. Equilibrium sorption coefficients (K-d and K-f) were also measured for different 1,4-dioxane and TCE compositions, and the findings indicate that both contaminants adsorb to aquifer sediments and TCE K-d values increased with increasing organic matter content. However, the K-d for TCE decreased with increases in 1,4-dioxane concentration, which was attributed to cosolvency impacts on TCE solubility. These findings further advance our understanding of the mass-transfer processes controlling groundwater plumes containing 1,4-dioxane, and also have implications for the remediation of 1,4-dioxane contamination. (C) 2019 Elsevier Ltd. All rights reserved.Item Applicability of time fractional derivative models for simulating the dynamics and mitigation scenarios of COVID-19(Pergamon, 2020) Zhang, Yong; Yu, Xiangnan; Sun, HongGuang; Tick, Geoffrey R.; Wei, Wei; Jin, Bin; University of Alabama Tuscaloosa; Hohai University; Nanjing Normal University; Nanjing Medical UniversityFractional calculus provides a promising tool for modeling fractional dynamics in computational biology, and this study tests the applicability of fractional-derivative equations (FDEs) for modeling the dynamics and mitigation scenarios of the novel coronavirus for the first time. The coronavirus disease 2019 (COVID19) pandemic radically impacts our lives, while the evolution dynamics of COVID-19 remain obscure. A time-dependent Susceptible, Exposed, Infectious, and Recovered (SEIR) model was proposed and applied to fit and then predict the time series of COVID-19 evolution observed over the last three months (up to 3/22/2020) in China. The model results revealed that 1) the transmission, infection and recovery dynamics follow the integral-order SEIR model with significant spatiotemporal variations in the recovery rate, likely due to the continuous improvement of screening techniques and public hospital systems, as well as full city lockdowns in China, and 2) the evolution of number of deaths follows the time FDE, likely due to the time memory in the death toll. The validated SEIR model was then applied to predict COVID-19 evolution in the United States, Italy, Japan, and South Korea. In addition, a time FDE model based on the random walk particle tracking scheme, analogous to a mixing-limited bimolecular reaction model, was developed to evaluate non-pharmaceutical strategies to mitigate COVID-19 spread. Preliminary tests using the FDE model showed that self-quarantine may not be as efficient as strict social distancing in slowing COVID-19 spread. Therefore, caution is needed when applying FDEs to model the coronavirus outbreak, since specific COVID-19 kinetics may not exhibit nonlocal behavior. Particularly, the spread of COVID-19 may be affected by the rapid improvement of health care systems which may remove the memory impact in COVID-19 dynamics (resulting in a short-tailed recovery curve), while the death toll and mitigation of COVID-19 can be captured by the time FDEs due to the nonlocal, memory impact in fatality and human activities. (C) 2020 Elsevier Ltd. All rights reserved.Item Application of phosphate and surfactant-modified zeolite for remediation/attenuation of trace elements in soil and coal fly ash(University of Alabama Libraries, 2012) Neupane, Ghanashyam; Donahoe, Rona Jean; University of Alabama TuscaloosaThis dissertation presents results of a research work aimed at understanding and addressing trace element contamination sourced by coal fly ash and arsenic trioxide herbicide. Both alkaline and acidic fly ash samples were found to contain significant concentrations of environmentally available trace elements. The treatment of fly ash leachate with surfactant-modified zeolite (SMZ) decreased the mobility of several trace elements. In general, up to 30% of the As, Mo, and V; up to 80% of the Cr; and up to 20% of the Se and Sr were removed from the leachate after SMZ treatment. Batch experiments, surface complexation modeling, and X-ray spectroscopic tools were used to elucidate the kinetics and mechanisms of arsenate (As(V)) and phosphate (Pi) adsorption on ferric hydroxide. Both oxyanions showed similar adsorptions during single-ion adsorption experiments; however, As(V) was preferentially adsorbed during competitive adsorption experiments. Similarly, more As(V) was adsorbed when it was loaded in sequence in Pi-equilibrated system than vice versa. Both oxyanions competed for adsorption on ferric-hydroxide and each of them showed a limited capacity to desorb the other, and relatively, more pre-equilibrated Pi was desorbed by sequentially added As(V) than vice versa. The As K-edge EXAFS analysis indicated the presence mononuclear and binuclear bidentate As(V) surface complexes. The Fe coordination numbers (CN) of these complexes increased with increasing time and decreased with addition of Pi into the system. Finally, an arsenic-contaminated soil collected from an industrial site located in the southeastern United States was amended with Pi and Ca to precipitate the arsenic as As-bearing apatite-like minerals. Phosphoric acid amendment of the soil with simultaneous addition of Ca dramatically decreased the mobility of soil As to near zero at pH > 6. Characterization of precipitate separated from the Ca-Pi treated soil by X-ray diffraction indicated that a carbonate-apatite mineral was formed in the soil and likely incorporated As(V) into its structure. The low solubilities of many of the Ca-Pi-As(V) minerals suggest that Ca-Pi treatment has promise as an effective, long-term method for in situ chemical fixation of As in contaminated soils and wastewaters.Item Assessing the Robustness of Deep Learning Streamflow Models Under Climate Change(University of Alabama Libraries, 2022) Qualls, Logan Michelle; Tick, Geoffrey R.; University of Alabama TuscaloosaLong Short-Term Memory networks provide the most accurate rainfall-runoff predictions to-date, but their reliability under climate change is not well understood. We explore the robustness of these models under climate nonstationarity by creating train and test data splits thatare designed to simulate climate bias. By training on forcing data from hydrological years of high (low) aridity and testing on data from hydrological years of low (high) aridity, we can begin to quantify the performance and relative robustness of that performance under climate nonstationarity. We benchmark against a calibrated conceptual model (the Sacramento Soil Moisture Accounting model) and a calibrated process-based model (the NOAA National WaterModel), and found that LSTMs were generally more accurate than both, even when trained on climatologically biased data splits. The process-based model did not show as large of a performance gap as the conceptual and deep learning models, however (i) this model was not calibrated on a climate-biased data split and (ii) LSTMs always out-performed the process-based benchmark, even when the LSTM training data had climatological bias. We find that although all hydrologic models reported here degrade under nonstationarity, DL models demonstrate greater robustness. We also tested the hypothesis that dynamic climate attributes as inputs into the LSTM would improve performance under climate nonstationarity. We found no predictive value with the addition of dynamic, as opposed to static, climate attribute inputs.Item Carbonation of flue gas desulfurization gypsum for CO2 sequestration(University of Alabama Libraries, 2021) Riddle, Jonathan B.; Donahoe, Rona J.; University of Alabama TuscaloosaThe IPCC asserts that to prevent a 2°C global temperature increase by the year 2050, CO2 must be removed from the atmosphere by sequestration. The goal of this study was to use FGD gypsum for CO2 mineralization and experimentally explore to find the optimal conditions for the highest conversation rates at ambient temperature while eliminating ammonia usage. While maintaining an alkaline solution using NaOH, a stirred reactor was utilized to study the effects of PCO2 (0.69, 2.07, 4.14, 6.89, and 17.24 bar), solution pH (12, 13, 13.5 and 14), solid-to-solution ratio (1:100, 1:80, 1:40, 1:100), and reaction time (10, 15, 30, and 120+ min) variation on the rate of conversion. The CaCO3 produced was calculated by Rietveld refinement of XRD patterns to determine the impact of each experimental variable.Experimental results showed solution pH was a primary control on mineralization, with nearly 100% conversion of FGD gypsum to CaCO3 occurring at initial pH = 13.5 and 14, for PCO2 > 2 bar and S:L = 1:100. At initial pH of 12, no gypsum conversion occurred. Reaction time also affected the amount of gypsum conversion to CaCO3. At initial pH = 13, S:L = 1:100 and PCO2 = 2.07 bar, 15 min was the optimum reaction time, achieving 75% conversion. However, with the same conditions at 360 min, a 61% conversion occurred, due to final pH’s below 7. Increasing S:L ratio resulted in increased gypsum-to-carbonate conversion. The optimal conditions for conversion of gypsum into calcite occurred at short reaction times of 15 min, low pressures at around PCO2 = 2.07 bar, and low solution ratios of S:L = 1:100, achieving 75% conversion. In contract, a reaction time of 360 min produced a result of only 61% conversion at the same PCO2 and S:L ratio, due to the pH dropping below 7. The results of this study demonstrate that FGD gypsum is a viable feedstock for CO2 mineralization, potentially offering a cheap and rapid method for carbon sequestration.Item Cave air C O_2 and drip-water geochemical variability at Desoto Caverns: implications for speleothem-based paleoclimate studies(University of Alabama Libraries, 2017) Dhungana, Rajesh; Aharon, Paul; University of Alabama TuscaloosaThis study has addresses the question whether speleothems from DeSoto Caverns (Childersburg, AL) can be used as paleoclimate archives for the Southeast USA. The monitoring program encompassed determination of cave air CO2, cave ambient conditions (i.e., air temperature, humidity), drip-water geochemistry and local rainfall amount, and stable isotopes of oxygen and hydrogen (Tuscaloosa, AL). The substantial attenuation of drip water isotope ranges (-3.1 to – 5.3 ‰ V-SMOW) relative to rainwater (-1.2 to -6.4 ‰ V- SMOW) is likely caused by mixing of freshwater with residual evaporated water in the epikarst zone. The cave drip water δ18O shows an interannual negative trend from the warm/dry year (2012) to the relatively cool/wet year (2013) suggesting that evapotranspiration above the cave plays an important role in drip water δ18O variability. Drip water Ca, Mg and Sr and Mg/Ca and Sr/Ca ratios exhibit lower values and higher ratios, respectively, during the warm/dry relative to the cool/wet year. The interannual rainfall amount variability likely exerts a dominant control on the elemental concentrations and elemental ratios of the drips. Cave air pCO2 varies seasonally with high values (up to 5.0 atm ×103) during summer when cave air flow is in stagnation mode and low values (down to 0.48 atm ×103) during winter when cave air flow is in ventilation mode. The data suggest that seasonal variations in the concentration of cave air CO2 affect the δ13C of drip water and by extension that of speleothem δ13C values. The documented abrupt hydroclimate changes at ~5 ka in a DeSoto stalagmite is synchronous with the reduction of the North Atlantic Deep Water (NADW) production suggesting the latter being the likely controlling factor. The periodic (68 ± 4 yrs periodicity) switches of seasonal rainfall amount dominance from winter to summer and back are a prominent feature of the mid-to-late Holocene δ18O time series of the speleothem. The observed 68 ± 4 yrs periodicity in stalagmite 18O agrees well with the ~ 70 yrs periodicity of the Atlantic Multidecadal Oscillation (AMO) suggesting the latter played a dominant role in the hydroclimate changes in the southeastern US during the late Holocene.Item Deepwater Horizon oil spill: using microcosms to study effects of crude oil in coastal sediments(University of Alabama Libraries, 2013) Rentschler, Erika Kristine; Donahoe, Rona Jean; University of Alabama TuscaloosaApproximately 4.9 million gallons of crude oil traveled with ocean currents to reach the Gulf coast after the Deepwater Horizon oil drilling rig explosion. Microcosm experiments were conducted to determine how oil contamination affects the concentration and distribution (between solid and aqueous phases) of trace elements in a salt marsh environment. Sediment and seawater from a salt marsh at Bayou La Batre, Alabama, were measured into jars and spiked with 500 ppm MC-252 oil. The solid phase and aqueous samples were analyzed by ICP-OES, ICP-MS, and IC. A second experiment was conducted using various concentrations (0 ppm, 10 ppm, 100 ppm, 500 ppm, 1000 ppm, 2500 ppm) of MC252 oil. ICP-OES data show variations in aqueous elemental concentrations occurred over the 14 day experiment. The pH for the water in the experiments ranged from 6.93 to 8.06. Significant positive correlations (r>0.75) were found in the solid phase samples between iron and the following elements: aluminum, cobalt, chromium, and nickel. Aqueous iron concentrations were highly correlated (r>0.75) with solution pH. The presence of iron oxide and clays in the salt marsh sediment indicates potential for adsorption of trace elements sourced from the environment and from crude oil contamination. The release of aqueous Fe (II) observed between two and 14 days is likely caused by reductive dissolution of iron-bearing clays or iron oxide. All the samples that contained oil behaved in similar ways with respect to time, but the controls showed almost no changes in the concentrations of the trace elements. Although the levels of some trace elements in the solid phase changed during the experiments, their final concentrations were at the same levels as the control samples. With the exception of nickel, the 14 day samples contained lower trace metal concentrations than the sterile control which contained no oil. The reason for this is likely attributable to the in situ oil-degrading bacteria, which were found to be present in the sediment. The oil-degrading bacterial community increased in the presence of oil and decreased as the oil concentration decreased. Oil-degrading bacteria are capable of inducing reductive dissolution in Fe (III) minerals.Item Dissolution and mass flux from trichloroethene- and toluene- hexadecane multicomponent nonaqueous phase liquid (NAPL) mixtures(University of Alabama Libraries, 2015) Padgett, Mark; Tick, Geoffrey R.; University of Alabama TuscaloosaRemediation efforts and contaminant transport predictions generally neglect the complicated dissolution and transport behavior associated with multi-component nonaqueous phase liquid (NAPL) sources. Therefore, it is important to understand the diffusion and dissolution processes occurring in these multicomponent systems as a function of mole fraction, molecular similarity/dissimilarity, and nonideal hydraulic factors. A series of laboratory scale NAPL-aqueous phase dissolution experiments were conducted to assess dissolution and intra- NAPL diffusion as a function of multicomponent NAPL composition (mole fraction) for both trichloroethene (TCE) and toluene (TOL). Predetermined volumes of target NAPL compounds were mixed with an insoluble n-hexadecane (HEX) NAPL to create mixtures that vary by NAPL composition. The ideality of resulting target compound dissolution was evaluated by quantifying NAPL-phase activity coefficient through Raoult's Law analysis. The results show that dissolution from the NAPL mixtures behave ideally for mole fractions above 0.2. As the target compound fraction of the NAPL mixture gets smaller, the dissolution behavior becomes increasingly nonideal (larger NAPL-phase activity coefficients). The TOL:HEX mole fraction mixtures show greater nonideality at equilibrium and initial elution concentrations for batch and column experiments when compared to TCE:HEX systems. Mass flux reduction analysis shows that the 0.5:0.5:, 0.2:0.8, and 0.1:0.9 mole fractions of both TCE and TOL behave similarly while the 0.05:0.95 mole fractions of TCE and TOL behave the most nonideally and exhibit mass flux reduction before any other mole fractions. Overall, the dissolution rates were constant and not controlled by NAPL composition-dependent factors. The results of this work may be used to improve transport predictions, remediation design, and risk assessments especially for sites contaminated by complex NAPL mixtures.Item Enhanced-solubilization of multicomponent dense immiscible liquid in homogeneous porous media(University of Alabama Libraries, 2014) Slavic, David; Tick, Geoffrey R.; University of Alabama TuscaloosaComplex multi-component nonaqueous phase liquid (NAPL) mixtures can significantly limit the effectiveness of groundwater remediation. The use of enhanced-flushing technologies has emerged as a promising technique for the remediation of sites contaminated with NAPL. A series of one-dimensional column experiments was conducted to quantify the effectiveness of four flushing agents (also called "solubilizing agents"; the terms are synonymous in this study) for the removal of a uniformly distributed multi-component NAPL source within a homogeneous porous medium. The columns were established with NAPL saturations (Sn) targeted between 10- 20%, consisting of an equal 1:1:1 mole mixture of tetrachloroethene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene (DCE). The solubilization agents investigated included 5 wt.% solutions of two complexing sugars: hydroxypropyl-beta-cyclodextrin (HPCD) and methyl-beta-cyclodextrin (MCD), a 5 wt.% solution of a surfactant: sodium dodecyl sulfate (SDS), and a 50 wt.% solution of ethanol (EtOH). For comparison purposes, a water flush (pump-and-treat) experiment was also conducted as a control, representing the system by which no enhanced- solubilization occurred. In general, initial effluent NAPL concentrations were successfully predicted using Raoult's Law, with minimal deviation (error) between the observed and predicted concentrations. The experimental data were used to test the efficiency of each flushing agent by analyzing the normalized contaminant mass recovery, the mass ratio of contaminant removed to reagent used, and the mole ratio of contaminant removed to reagent used. Mass flux reduction analysis was also used to test the efficiency of the various flushing agents. The results of the analyses showed that EtOH was the most efficient flushing agent when analyzed based on a normalized mass recovery basis. SDS exhibited the most efficient removal when the experiments were analyzed by mass-contaminant removed to mass reagent used. Based on the moles-contaminant removed to moles reagent used ratio efficiency evaluation, MCD was the most effective flushing agent. The results of these experiments indicate that the addition of a chemical flushing agent greatly reduces the time needed to remove each NAPL component, compared to flushing with water alone (i.e., pump and treat). PCE showed the greatest relative solubility enhancement for all enhanced flushing agents tested. MCD and SDS were most effective flushing agents for the three-component NAPL system, removing all three components (DCE/TCE/PCE) with the least number of pore volumes. The HPCD flush showed no appreciable solubility enhancement for DCE and TCE; however, PCE did show a 10-fold enhancement in solubility for this experiment. In terms of mass flux reduction/mass removal (MFR/MR) evaluation, DCE (the highest solubility NAPL component) exhibited the greatest nonideal (inefficient) response during both the water and HPCD flushing experiments. Mass flux reduction behavior was less ideal for the MCD flush compared to the other enhanced-flushing agents. EtOH showed superior performance when evaluated based on a normalized contaminant mass recovery basis, but showed relatively poor performance based on a mass ratio or mole ratio removal evaluation. SDS surpassed all other flushing agents based on a contaminant mass- recovery to reagent used basis, whereas MCD exceeded the removal efficiencies of the other enhanced flushing agents. In general, technical grade HPCD and MCD are more expensive than SDS and EtOH, and therefore may be less desirable choices for use at greater scales; however, their toxicities to microbial communities in the subsurface and potential concerns to human health and the environment are negligible compared to SDS and EtOH. Results from this study indicate that several criteria should be used to evaluate the removal effectiveness of flushing agents for multi-component NAPL systems. Due to the variety of remediation scenarios that could be encountered in the field, these findings will be helpful in developing more efficient and effective remediation strategies and for enabling more accurate prediction of resulting NAPL concentrations to meet the needs of various contaminated sites impacted by chlorinated compounds such as PCE, TCE, and DCE.Item Establishing cost effective methods to analyze a wide range of pharmaceutical compounds through laboratory scale experiments aimed at assessing fate and transport mechanisms in groundwater(University of Alabama Libraries, 2015) Salome, Patrick Anthony; Tick, Geoffrey R.; University of Alabama TuscaloosaPharmaceutical and organic wastewater contaminants have been increasingly detected in drinking water and groundwater supplies. A stepwise approach was used to determine a simple and cost effective method for testing various classes of pharmaceutical compounds. A robust, accurate method was developed and validated using two commonly detected pharmaceuticals in water resources; sulfamethoxazole (SMX) and carbamazepine (CMP). Tandem solid-phase extraction in conjunction with high performance liquid chromatography (HPLC) analysis was effective for quantifying concentrations of analytes under environmentally relevant laboratory-scale scenarios. Using predetermined standards and known concentrations, an average recovery percentage of 96.25% was achieved in validation efforts. Batch tests consisting of streambed sediment and known concentrations of the study analytes were conducted over a 96-hour period to determine Freundlich adsorption isotherm coefficients (KF) and retardation factors (R). The results of these tests demonstrate that CMP had a greater affinity to adsorb to the sediment (K_F=8.79) compared to SMX (K_F=4.22) with corresponding retardation factors (R) of 49.3 and 20.7, respectively. In addition to the development of a promising cost-effective analytical method to quantify different types of pharmaceutical compounds in groundwater, this work also demonstrates that SMX (compared to CMP) may pose higher risk for entering drinking water supplies, as natural retention processes will be less under most conditions. Limits of detection using the SPE/SPE HPLC-UV method was 0.48 μg/L for SMX and 0.60 μg/L for CMP.Item Evaluation of submarine groundwater discharge and groundwater quality using a novel coupled approach: isotopic tracer techniques and numerical modeling(University of Alabama Libraries, 2013) Ellis, John H.; Tick, Geoffrey R.; Dimova, Natasha T.; University of Alabama TuscaloosaIt has been recognized that submarine groundwater discharge (SGD) may be one of the principal pathways for delivering nutrients to surface water bodies, resulting in eutrophication of many nearshore coastal areas throughout the world. A one-year study of the coastal aquifer system (A1, A2, A3-Aquifers) of Gulf Shores, Alabama was conducted to assess SGD fluxes, characterize contaminant and nutrient transport through the aquifer system, and determine the availability of future aquifer resources. A three-dimensional density-dependent groundwater flow and transport model (SEAWAT), based on the coupling of MOFLOW and MT3DMS, was used to simulate the transport of nitrate and sulfate through the groundwater system to the coast. The model was refined and calibrated using independently determined field-based radon (222Rn, t1/2=3.82 d) isotopic tracer time-series surveys across a portion of the model area to enhance estimates of nearshore SGD. Two SGD approaches, integrated with 222Rn-determined seepage rates, were developed to determine (1) localized; and (2) entire-shoreline SGD. Thirty-two groundwater wells within the study area were sampled to constrain the groundwater 222Rn end-member in the model and characterize the extent of nutrient contamination. The ArcGIS database was used to spatially plot and interpret nutrient and 222Rn data, and generate iso-concentration maps detailing groundwater contamination and aquifer piezometric surfaces across the study area. Radon concentrations measured in groundwater from the shallow A1 and deeper A2 Aquifers were statistically identical, an indication that there is direct connection between the two systems. Elevated nitrate and sulfate concentration (up to 30 mg/L and 724 mg/L, respectively) were observed through active monitoring with zones of principal discharge identified in the lower A2 Aquifer. A groundwater seepage rate of 18.3 cm/day, calculated through the radon mass-balance model at a model area lake, was used to calibrate the numerical model surficial aquifer zone. Final shoreline seepage fluxes of 6.41 and 8.62 cm/day were determined from the results of both the multi-cell and shoreface numerical model simulation SGD approaches, respectively. The results of the two numerical SGD methods demonstrate good agreement with the 222Rn-derived methods, and provided an effective approximation technique that can be inexpensively duplicated in other similar shoreline areas.Item Experimental simulation of arsenite leaching on soils and mechanism of arsenite oxidation(University of Alabama Libraries, 2012) Yue, Ziming; Donahoe, Rona Jean; University of Alabama TuscaloosaArsenic trioxide was widely applied to soils in North America as an herbicide during the 1950-60s. These herbicide applications led to soil arsenic contamination at numerous sites. Decades after the herbicide application, the contaminated soil served as a secondary source for long-term leaching of arsenic into the groundwater system. To understand the history of arsenic contamination at these sites, column experiments were conducted to simulate the herbicide application and subsequent arsenic leaching processes. The experimental data showed that the effluent solution arsenic became dominantly As(V) after 180 pore volumes (equivalent to ~60 years of natural leaching, assuming a 50% recharge rate) of leaching, which represented an abnormally rapid arsenite oxidation rate (up to 60 mg/L/6.5 hours As(V)) (Yue and Donahoe, 2009). During peak arsenic release, the arsenite oxidation rate doubled (120 mg/mL/6.5 hours). Homogeneous As(III) oxidation cannot be responsible for the observed oxidation rate because the half life of As(III) in air can be up to one year (Eary and Schramke, 1990). Incubation experiments were designed, where sterilized and inoculated serum bottles with added aqueous As(III) and soil were compared for their aqueous total arsenic and As(V) concentrations. The aqueous As(V) in the innoculated series increased with time but remained below detection in the sterile series. This indicated that the As(III) oxidation observed in the column experiments was caused by the microbes in the soil. Bacterium strains A4 and A12 were isolated from the column soil and were tested to be the efficient arsenite oxidizers in the column experiments. Strain A12 shared 100% 16S rDNA sequence with Burkholderia. fungorum LMG 16225^T, while strain A4 shared 99.1%, 97.3% and 96.7% 16S rDNA sequences with strains Burkholderia. zhejiangensis CCTCC AB 2010354^T, B. glathei DSM 50014^T and B. sordidicola KCTC 12081^T, respectively. A polyphasic characterization, including phenotypic and biochemical characterization, 16S rDNA sequence analysis, DNA-DNA hybridization, and fatty acid analysis, was conducted on strain A4 to determine its taxonomic position. The results showed that strain A4 represented a novel species in the genus Burkhoderia, for which the name Burkholderia arsenicoxydans sp. nov. is proposed. The type strain is A4^T (=ATCC BAA-2404^T=CCTCC AB 2012027^T).Item Groundwater flow dynamics and contaminant transport to coastal waters under low recharge conditions: regional-scale study of the aquifer system underlying southern Baldwin County, Alabama(University of Alabama Libraries, 2009) Murgulet, Dorina; Tick, Geoffrey R.; University of Alabama TuscaloosaThis study examined the influence of drought conditions and increased hydrological stresses on the groundwater system flow dynamics, submarine groundwater discharge, and nitrate transport and discharge to the Gulf of Mexico. The results of these studies demonstrate that current stresses on the aquifer have led to significant saltwater intrusion and or direct infiltration into fresh groundwater, especially within the upper aquifers of the region. The nitrate and chloride data analyses reveal the persistent presence of multiple nitrate impacted zones within the study area. Stable isotope data support the hypothesis that nitrate in the investigated aquifers originates from the nitrification of ammonium in soils from a mixture of sources ranging from fertilizer to sewer and/or manure and that denitrification, the breakdown of nitrates to nitrogen gas, is not significant in the investigated aquifer system. Furthermore, groundwater isotope data indicates that water in the aquifer system of the study area is most likely to have originated from precipitation and soil infiltration through relatively localized recharge and that the aquifer system in the study area is highly dynamic, experiencing mixing of recent recharged waters with older, ambient groundwaters. The presence of low residence times and the absence of denitrification reveal the oxic character of this system. As a proxy for a number of contaminant types, the groundwater flow and transport model was used to simulate nitrate transport in response to variable-density groundwater flow. The simulation results indicate that in the investigated aquifer system complexities arise because groundwater flow dynamics and contaminant transport are additionally influenced by density variations that can occur from the incursion of saltwater. The model predicts that the Beach Sand and Gulf Shores Aquifers will be impacted by severe saltwater intrusion whereas the deeper 350 and 500-Foot Aquifers will experience no saltwater intrusion for the entire simulation period. Consequently, nitrate discharge to the Gulf of Mexico originates from the lower part of the aquifer system through submarine groundwater discharge. This research will serve as a tool which may be applied to other similar coastal systems for more effective management strategies.Item High resolution, U/Th dated (32,000 to 11,000 years), oxygen and carbon isotope proxy climate records from a stalagmite in Desoto Caverns, Alabama, USA(University of Alabama Libraries, 2010) Lambert, William Joseph; Aharon, Paul; University of Alabama TuscaloosaThis study addresses the question whether speleothems from DeSoto Caverns (Childersburg, AL) can serve as archives of paleoclimate conditions for the Southeast, USA. The focus of the study involves determining present-day controls of cave water δ^18 O and δ^13 C followed by interpretation of stalagmite δ^18 O and δ^13 C variability in comparison to climate events of the past. The monitoring program involved a 3-year study of cave waters and local rainfall (Tuscaloosa, AL) during years characterized by a significant trend from wet to dry conditions. Decreasing recharge of the cave aquifer was expressed as an interannual trend of declining drip flow rates, which was punctuated by seasonal oscillations due to varying rates of evapotranspiration. Amount-weighted mean monthly rainwater δ^18 O range from -1.5 to -8.3 /, show a mean seasonal amplitude of ~4 /, and exhibit an interannual trend toward ^18 O-enrichment that I interpret as being governed by global atmospheric circulation patterns. The cave's aquifer attenuates seasonal δ^18 O variability, records 20% of rainfall's interannual ^18 O-enrichment, and is biased toward winter rainfall δ^18 O. Cave waters display strong seasonal variability in dissolved inorganic carbon (DIC) and δ^13 C, which range from 0.2 to 6.0 mM and 2.7 to -12.9 / (VPDB), respectively. The data suggest the strongest seasonal controls are cave air ventilation/stagnation and varying CO_2 fluxes through the soil horizon and epikarst. δ^13 C of active speleothems imply the precipitating aragonite captures the seasonality observed in source dripwaters and time-series δ^13 C records of stalagmites carry the imprints of drip annual means entailing climate-driven δ^13 C seasonal biases. A fossil stalagmite provided a high-resolution proxy record of rainfall variability between 31.9 and 11.3 ka. I propose a more southerly polar jet stream (PJS) promoted increased winter rainfall amounts during cold phase events while warm phases result in a higher PJS position and decreased winter rainfall. The Younger Dryas was characterized by a dramatic change in the PJS path as warm air from the Gulf of Mexico infiltrated deep into the continent's interior and substantially decreased winter rainfall. Establishment of near modern climate conditions greatly enhanced deposition rates before changes in flow paths through the epikarst prevented stalagmite deposition since 11.3 ka.Item A high-resolution hydroclimate record of the last three millennia from a cored stalagmite at Desoto Caverns (Alabama, USA)(University of Alabama Libraries, 2010) Dhungana, Rajesh; Aharon, Paul; University of Alabama TuscaloosaLate Holocene climate changes in the Southeast USA are poorly documented due to the paucity of high-resolution paleo-records. This study provides high-resolution records of rapid hydroclimate changes in the Southeast over the last three millennia. The records are based on stable isotope rainfall proxies whose time series are constrained by precise U/Th dates from a stalagmite sampled at DeSoto Caverns. The average growth rate of the stalagmite was 149 µm/yr prior to 1400 years and it has been growing with an average growth rate of 42 µm/yr in the last 1400 years. During the past three thousand years stable isotope time series document six wet episodes (at ~ 2950, 2450, 1675, 1200, 700 and 70 years ago) alternating with six drier periods (at ~ 3100, 2800, 1900, 1500, 800 and 300 years ago). The biannually resolved 18O record agrees well with the contemporaneous SST record from the Sargasso Sea cores suggesting that changes in moisture availability in the Southeast are likely linked to subtropical North Atlantic SST variability. Power spectra analysis of the stalagmite-based oxygen isotope record reveals statistically significant periodicities at 24±1 and 36±1 year that are consistent with those observed in the contemporaneous atmospheric 14C production record. The 24 years periodicity is also consistent with the 24-year NAO Index periodicity. On the basis of our analysis we propose that the hydroclimate in the Southeast USA over the last three millennia was intimately linked to NAO variability powered by solar activity fluctuations.Item Impact of elevated dissolved CO_2 on aquifer water quality(University of Alabama Libraries, 2015) Pugh, John David; Donahoe, Rona Jean; University of Alabama TuscaloosaCarbon capture and storage (CCS), specifically by means of geologic sequestration (GS), is a developing technology to reduce CO2 emissions to the atmosphere. This technology involves separating CO2 from flue gas and transporting the CO2 to underground storage locations that are isolated from the atmosphere. These storage locations are typically permeable and porous geologic formations that are not useful for any other purpose, such as drinking water. Geologic carbon sequestration operated at full-scale will require extensive performance monitoring, including potable groundwater monitoring. However, researchers and regulators do not fully understand what impact elevated CO2 levels would have on groundwater quality in the event that CO2 should leak into an overlying aquifer. The focus of the current study was to thoroughly characterize the properties of a typical Gulf Coast potable aquifer for purposes of performing a controlled CO2 release experiment and to construct coupled geochemical and transport models capable of predicting impacts from CO2 migration into a drinking water aquifer. The aquifer is a methanogenic environment composed primarily of quartz and feldspars, with minor or trace amounts of pyrite, mica, illite, smectite, and kaolinite. The formation water is dominantly Na-HCO3, consistent with the theory and PHREEQC modeling results that suggest aquifer freshening and ion exchange have played dominant roles in determining the present-day dissolved major ion composition. This study also presents the design and implementation of a closed loop pumping and injection system designed to simulate CO2 leakage into a test site aquifer. Process monitoring results indicated that the test was performed with minimal variation in key process parameters, including temperature, pressure and injectate pH. In situ instrumentation deployed in monitoring wells allowed continuous readings of groundwater pH and conductivity, which were critical parameters for evaluating the aquifer response to carbonation and acidification. Successful modeling simulation of the pH response using results from the aquifer testing program suggested that the test was implemented and monitored appropriately and that that future data interpretations and modeling of the field experiment were not compromised by test design. Test results showed that no constituent was mobilized in excess of US EPA maximum contaminant levels, but that many constituents (primarily major and minor cations) were released in a pulse-like response at levels above their baseline concentrations. Dissolution of trace carbonate and pyrite in the aquifer are hypothesized to have triggered cation exchange reactions, a dominant geochemical process affecting major and minor cation behavior in the aquifer. Overall, the test has shown that the migration of carbon dioxide into a drinking water aquifer can mobilize ions into solution, but at levels that may not exceed EPA MCLs under the field conditions tested for this specific system. Data presented here are potentially applicable to assessments across the Gulf Coast, where the potential for deep geologic carbon sequestration and continued reliance upon groundwater resources are high.Item Influence of flow regime on U(VI) sorption kinetics in fine sediments at the Hanford site, Washington, USA(University of Alabama Libraries, 2012) Moser, Jessa V.; Zheng, Chunmiao; University of Alabama TuscaloosaThe effect of flow rate on U(VI) sorption kinetics was investigated by a series of column tests using the reactive mass fraction (<2mm) of sediments from the 300 Area in Hanford, WA. Three sets of constant flow rates subject to multiple stop flow events were employed to obtain U(VI) breakthrough curves at the column outlet. A lognormal distributed multi-rate surface complexation model was used to match the experimental breakthrough curves and calibrate the parameters of the multi-rate distribution. The results from the column tests clearly show that the mean of the lognormal distributed sorption rate constants increase with the flow rate, while the standard deviation of the lognormal distributions decreases with the flow rate. This finding is the first empirical evidence for the flow rate dependence of the multi-rate sorption kinetics and is thus of fundamental importance for future efforts to further improve the predictive modeling and remediation of U contamination.Item Investigation of natural weathering processes and artificial treatment techniques in the attenuation of toxic metals from coal fly ash(University of Alabama Libraries, 2010) Bhattacharyya, Sidhartha; Donahoe, Rona Jean; University of Alabama TuscaloosaCoal fly ash contains high levels of hazardous trace elements such as As, B, Cr, Mo, Ni, Se, Sr and V, which may have a negative impact on the environment due to potential leaching by acid rain and groundwater. This study seeks to develop new fly ash management techniques by determining the effects of natural weathering on trace element mobility in fly ash and by evaluating the potential use of surfactant-modified zeolite and ferrous sulfate treatment for attenuating the mobility of trace elements associated with fly ash. The effects of weathering on trace element mobility in fly ash were studied using batch competitive adsorption experiments. Fresh fly ash shows high adsorption capacity for As, V and Mo, while weathered fly ash shows high affinity for Ni, Sr, As and V. Both fresh and weathered fly ash show low adsorption capacity for Se and B. Weathering reduced the adsorption capacities of fresh fly ash for As, B, Cr, Mo, Se and V, indicating increased mobility in ash disposal environments. The effectiveness of surfactant-modified zeolite (SMZ) as a PRB material was studied using batch experiments under competitive adsorption conditions. The results showed that SMZ preferably adsorbed V, Mo and Cr over As and Se. Unmodified zeolite (UMZ) showed high adsorption capacities for Ni and Sr. Both SMZ and UMZ failed to remove B from solution. The use of SMZ as a PRB material in coal fly ash management will be limited by its low affinity for B as well as its relatively low affinity for As, Se and cations. Ferrous sulfate treatment of coal fly ash successfully reduced the mobility of oxyanionic trace elements. The unbuffered 1:30 FS treatment was highly successful; oxyanion mobility reductions were: As (24-91%), Cr (82-97%), Mo (79-100%), Se (41-87%) and V (55-100%). On the other hand, the 1:30 FS fly ash treatment failed to reduce the mobility of B, Ni and Sr. Ferrous sulfate treatment is cost effective and can be applied directly to fresh fly ash produced in electric power plants, as well as to the fly ash already placed in the ash disposal facilities.Item Novel in-situ NAPL modification technique for persistent source-zone control and remediation(University of Alabama Libraries, 2015) Mateas, Douglas Joseph; Tick, Geoffrey R.; University of Alabama TuscaloosaThe remediation of groundwater contaminated due to NAPL (non-aqueous phase liquid) sources has been shown to be generally ineffective at reducing aqueous-phase NAPL concentrations to levels suitable for site closure. A novel, in-situ NAPL source-zone remediation method was tested in the laboratory using equilibrium batch tests and two-dimensional flow-cell experiments. The goal of this remediation method was to reduce the aqueous solubility and mass-flux of a target, toxic NAPL component through the in-situ creation of a NAPL mixture source-zone. Predetermined volumes of insoluble, benign n-hexadecane (HEX) or vegetable oil (VO) were injected into a toxic trichloroethene (TCE) source-zone through a simulated well within the flow-cell to form a NAPL mixture (TCE-HEX or TCE-VO). Initial NAPL-aqueous phase batch tests were conducted prior to the flow-cell experiments to evaluate the effects of various NAPL mixture ratios on equilibrium aqueous-phase concentrations of TCE and toluene (TOL) and to design optimal benign NAPL (HEX/VO) injection volumes for the flow-cell experiments. Variations in remediation performance between the different HEX injection volumes were relatively minor, and therefore inconsistent with Raoult's Law. This phenomenon likely resulted from non-uniform mixing of the injected HEX with TCE in the source-zone. VO injection produced a more favorable remediation result by causing TCE concentrations and mass-flux in the flow-cell to decrease more rapidly than with HEX injections. This phenomenon occurred because the injected VO was observed to mix more homogeneously with TCE in the source-zone due to a lower mobilization potential. Overall, this study indicated that the delivery of benign HEX/VO into the target, toxic TCE source-zone was effective in significantly reducing contaminant aqueous-phase concentration and mass-flux at intermediate scales. This novel remediation method may be feasible at larger scales, such as pilot field-scale studies, and may be a cost-effective solution to efficiently mitigate environmental pollution, attain regulatory compliance, and expedite site closure.Item Paleoclimate reconstructions over the last century from a tropical speleothem on Niue Island, South Pacific(University of Alabama Libraries, 2010) Murgulet, Valeriu; Aharon, Paul; University of Alabama TuscaloosaThe study examines the question whether speleothems from Niue Island (19°00'S, 169°50'W), a large carbonate platform located at the edge of West Pacific Warm Pool, can serve as archives of hydroclimate controlled by El-Niño/Southern Oscillation (ENSO) and of catastrophic cyclones that frequent the island. Niue Island is heavily karstified, with modern and fossil speleothems hosted by coastal and inland caves. The flank margin caves on Niue are shown to be formed by the action of corrosive groundwaters on uplifted Pleistocene-age reef carbonates in a tectonically active region. The focus of this study is an actively growing stalagmite sampled from a flank margin cave (Avaiki Cave) that contains about 146 years of deposition (2002-1856 AD). The stalagmite consists of sub-annual couplets alternating between white porous calcite laminae deposited during the austral summer and dark, compact calcite laminae deposited during the austral relatively dry winter. High resolution (sub-annual) stable isotope and trace element profiles accompanied by trace element X-ray mapping were used to test the validity of ENSO-controlled hydroclimate and tropical cyclones archived in the stalagmite. The results show that interannual variability in the stalagmite d18O and d13C time series agrees well with instrumental-derived ENSO phases (El Niño and La Niña events during 1866-2002) and the sea level pressure differential (Samoa-Fiji)-based SPCZ index (SPI) that controls the interdecadal hydroclimate variability. Severe cyclones that directly impacted Niue Island over the last century are recorded by abrupt, large increases in trace element concentration values of Mg, and S accompanied by stable isotope positive excursions bearing seawater-derived signatures. Application of selected trace elements (i.e., Mg, Na, S, P) as proxies of severe storms is a novel technique that can be successfully applied in carbonate coastal areas with flank-margin caves impacted by severe cyclones. This study also demonstrates that sub-annual geochemical cycles in trace element laminae, unresolved by analytical linear transects due their complex distribution pattern, are successfully imaged by large area X-ray mapping of the stalagmite