A physical model was used to study effects of gravity on areal recovery of a dense nonaqueous phase liquid (DNAPL) contaminant by alcohol pre-flooding and co-solvent flooding in dipping aquifers. Experimental results demonstrate a decrease in PCE recovery with increasing dip angle attributed to DNAPL swelling and migration, flood front instabilities, and bypassing of the source zone. Results demonstrate that alcohol pre-flooding can improve DNAPL recovery in the absence of a dip angle (horizontal orientation), but has negative effects when a dip angle exists. Electrokinetic experiments were conducted to examine effects of DC voltage gradient, pH, surfactants, ionic strength, and porous media on DNAPL movement in an electrical field. DNAPL movement was proportional to the applied voltage gradient and attributed to electroosmosis and electrophoresis. DNAPL droplets moved toward the cathodes under neutral and low pH conditions, and movement reversals were observed in high pH and ionic solutions / acase@tulane.edu

Two chemical oxidation technologies, the OMNIPURE(TM) electrolytic marine sanitation device (MSD) and the Purizer(TM) advanced oxidation process (AOP), were assessed to determine process efficiency enhancements Oxidation reduction potential (ORP), pH and free chlorine measurements indicated chlorine dioxide (ClO2·) and hypochlorite (OCl-) are the main oxidants produced by the OMNIPURE(TM) electrolytic cell. Hydrogen peroxide (H2O2) was produced by the cell in the absence of chlorine oxidants but it was not determined if H2O2 is formed with free chlorine. ORP levels also indicated the cell is capable of producing ferrate (HFeO4 -) from ferrous iron (Fe2+) in tests conducted to determine the quantity of milliequivalents of oxidants transferred to solution. Oxidant production efficiency may be enhanced by optimizing the electrolyte dose The Purizer(TM) Process design goal was to produce peroxone (O 3/H2O2) from oxygen, water and UV radiation; the original process design did not produce significantly more H2O 2 or greater ORP levels in solution than ozone (O3) gas applied to solution. The 254 nm UV lamp was changed to a dual frequency 185/254 nm lamp, the delivery system material was changed to glass (PyrexRTM ) and different configurations of UV radiation use and humidification were tested. Both humidified and dry 185/254 nm photolyzed O3 increased H2O2 production efficiency by up to 50 percent A nebulizing AOP was developed after assessment of existing technology was completed. The design intent in this process is to overcome observed limitations of bulk liquid treatment. It has been demonstrated to be more time efficient than and is cost-comparable to current AOP in bench experiments. Three optimal combinations of nebulized O3 gas, nebulized liquid H2O 2 and UV light were identified using constant liquid and gas flow rates and an excess dose of O3. O3 alone and O3 photolyzed by 254 nm UV degraded 90 percent of 200 mg/L EDTA within 5 minutes. Only the combination of O3 and 254 nm UV light was effective within fifteen minutes in a significant oxidation of chromium (III) to chromium (VI) which was used as an indicator of production of milliequivalents. Process efficiency can be enhanced by reducing the O3 dose and optimizing droplet size / acase@tulane.edu

Metals are released and accumulated in both living and environmental systems, and given the complex matrices unique to the two systems, there exist ion extraction and detection methods. This dissertation aims to combine analytical methods of both biological and environmental sciences to provide a means to assess the biological impact of environmental pollution Instrumentation commonly used for trace metal detection is too large or power consuming for practical field use. One trace level analytical method, cyclic voltammetry (CV), was adapted for field deployment. After using a 50% v/v nitric acid ion extraction method and optimizing CV instrumentation (e.g. mercury free high surface area graphite electrode cleaning and eliminating nitrogen purge) lead levels were determined in situ at three polluted urban locations in New Orleans, Louisiana. The results were compared to an established ion extraction method (ASTM D 3974) and analytical analyses (differential pulse polarography and dispersive X-ray diffraction). Despite higher ion and organic detection limits (two orders and four orders of magnitude, respectively) compared to other detection methods and spurious results at one test site, the field deployable analytical methods and instrumentation will provide environmental researchers with tools for the rapid analysis of environmental samples and identification of localized polluted areas with ion concentrations greater than 10 ppm The research measured lead extraction with simulated digestive acid exposure to polluted kaolin clay and Bayou Trepagnier sediment in vitro. The lead accumulation potential in catfish and crayfish based upon these experiments and published findings by other researchers, was estimated in catfish and crayfish to be 29.6 and 133 ppm, respectively Further development of the techniques and hardware in this work may provide researchers with tools that can identify environmental lead levels and predict lead ion bioaccumulation / acase@tulane.edu

Organic pollutants in anaerobic acidogenic systems have not been studied extensively despite the potential of acidogenic treatment to be an efficient and economical pretreatment process. In this study, fate and toxicity of four priority pollutant phenols (pentachlorophenol, PCP; 2-nitrophenol, 2-NP; 4-nitrophenol, 4-NP; and 2,4-dinitrophenol, 2,4-DNP) were investigated in an acidogenic, glucose-degrading anaerobic enrichment system Chemostat cultures (1.5-day SRT) were acclimated to 21, 42, and 59 muM (6, 12, and 17 mg/l) PCP for up to 261 days. No biodegradation of PCP was observed even in acclimated cultures. Extraction of PCP in serum bottles showed sorption to biomass was the dominant mechanism for PCP removal. PCP concentrations of 21--121 muM (6--35 mg/l) partially inhibited glucose degradation. In contrast to the control, the test chemostats with PCP showed formation of lactate and ethanol with lower acetate concentrations. Hydrogen-utilizing methanogens were inhibited by 21--121 muM (6--35 mg/l) PCP. Hence, contrary to expectations, the usefulness of anaerobic acidogenic cultures for degradation of PCP could not be substantiated In contrast to PCP dechlorination, nitrophenol transformation occurred rapidly in serum bottles with unacclimated acidogenic culture, mainly to the corresponding aminophenols. Abiotic nitrophenol removal was negligible. The ortho-nitro group was much more rapidly reduced than the para-nitro group, and removal of 2-NP and 2,4-DNP was faster than removal of 4-NP by almost an order of magnitude. With initial nitrophenol concentrations of 328--414 muM, first-order transformation rate constants were 0.061 hr-1 and 0.079 hr-1, respectively, for 2-NP and 2,4-DNP, versus 0.0034 hr-1 for 4-NP. Competitive inhibition coefficients for glucose uptake were comparable for 4-NP and 2,4-DNP and much lower than those for 2-NP. Literature values for methanogens and sulfate-reducers show that acidogens are more resistant to nitrophenol toxicity. The yield constant Y was significantly lower than in control serum bottles at high concentrations of all three nitrophenols tested, and the decay constant b was negligible at high concentrations of 2-NP and 2,4-DNP. Overall, the rapid removal of nitrophenols makes acidogenic systems a suitable pretreatment step for subsequent aerobic systems, while further research is necessary on factors stimulating PCP degradation by non-methanogenic anaerobes / acase@tulane.edu

This research evaluated the applications of variogram based geostatistical techniques in remediation of aquatic contaminated sediments. Five issues related to spatial interpolation and mapping of aquatic sediment contaminant concentrations were focused: Was spatial continuity of a concentration contaminant specific and water body specific? Were the geostatistical models as good as the deterministic spatial models? Could secondary data improve predictions and reduce uncertainty? How did sampling size influence? What was the influence of extreme high concentration measurements? Sediment data from two river sites, two ocean sites and a lake site were used in the study. Metal concentrations from four sites and PCB concentrations from one site were spatially modeled. Two types of geostatistical approaches, univariate kriging and cokriging, and four types of deterministic interpolation techniques, inverse distance weighted, global and local polynomials, and radial basis functions were compared for different data sizes. In geostatistical approaches, three theoretical variograms were fitted: spherical, experimental and Gaussian with nugget effect. Three types of krigings were studied: simple kriging, ordinary kriging and kriging with the trend Altogether 500 spatial interpolation models were fitted. Number of factors such as water body shape, contaminant type, data density and sample size, data spread pattern in the region, and extreme concentrations were found to influence the spatial modeling of sediment contaminant concentrations. In general, geostatistical models were found better than deterministic models. Cokriging a contaminant concentration with other contaminant concentrations, soil particle percentages, water depth and previous measurements of the same attributes in the region improved the predictions. Studying extreme high concentrations showed how hotspot prediction could be improved by modifying the modeling approach, depending on the pattern and locations of the extreme concentrations. As the influence of the high concentrations was significant in the models developed with small sizes of data, a thorough comparison of root mean square error with and without the high concentrations was recommended during the model selection Future studies should address the issues such as incorporating soft data in models, cost factor in modeling and incorporating geostatistical models with mechanistic contaminant sediment transport models developed on physical, chemical and biological properties / acase@tulane.edu

An in-depth investigation of integral asymmetric poly(vinylidene fluoride) (PVDF) membranes has been carried out for the extraction of organic compounds from dilute aqueous solutions. Flat sheet membrane performance for low and high-boiling non-polar organic components was excellent, with separation factors as high as 4,900 and high organic fluxes. Polar organic components were also separated effectively from water but the separation factors were lower than non-polar organics. There was no change in membrane performance when either the dense or porous surface of a PVDF membrane contacted the feed solution as long as the feed solution flow rate was sufficiently high. The effect of membrane preparation conditions, such as casting solution composition, air humidity and temperature during film drying, on membrane performance was quantified. Although the water flux through the resulting membrane changed significantly, the organic (benzene) flux was essentially independent of the fabrication method. Variations in casting conditions also changed the mean diameter of a small number of pores in the dense layer of PVDF membranes. Water fluxes during benzene/water separation correlated with increasing pore size, indicating that such pores were providing pathways for water movement across the hydrophobic dense layer. Based on benzene swelling and diffusivity measurements in homogeneous PVDF films, pores in the dense layer of an asymmetric membrane control permeate enrichment by either a pore flow or membrane distillation mechanism. The total time for asymmetric PVDF flat sheet membrane casting was reduced from 69-72 min to 7 min, while maintaining a high organic (benzene) separation factor with only a small drop in transmembrane benzene flux Asymmetric PVDF hollow fiber membranes, with an internal diameter of 0.05-0.06 cm, an outside diameter of 0.07-0.08 cm, and a dense layer (approximately 3 $\mu$m in thickness) on the inner fiber wall have been fabricated and tested for the removal of ppm concentration of organics from water. Membranes were made by air drying the outside of the fiber for about 20 seconds and passing a fluid through the fiber bore. The set of casting conditions that produced the best hollow fiber membranes, with a benzene separation factor of 1,834 (for a 120 ppm benzene-in-water feed solution at 25$\sp\circ$C and a downstream pressure of 0.025 atm) and a tensile strength 26.8 MPa, was a spinning solution of 25 wt% PVDF/30 wt% dimethylacetamide/45 wt% acetone and a bore fluid of 70 vol% water/25 vol% acetone/5 vol% dimethylacetamide. These membranes also separated effectively toluene, chloroform, and styrene from water. A small module containing 6-30 PVDF hollow fibers performed equally well for organic extraction from water with either a bore-side or shell-side feed when the feed solution flow rate was sufficiently high to eliminate concentration polarization. Changes in organic flux and separation factor for variations in the organic feed concentration, temperature and downstream pressure were qualitatively similar to those observed for asymmetric PVDF flat sheet membranes / acase@tulane.edu

Novel metal carboxylate precursors for ceramic materials have been developed which provide extremely low deposition temperatures and/or precise control of metal stoichiometry Low temperature metal oxide precursors based on metal complexes of $\alpha$-oximino carboxylate ligand pyruvic acid oxime (PAO) have been developed. Complexes of this ligand with a variety of metal cations, including main group elements, transition metals and rare-earths have been prepared. Results from X-ray analysis of a number of these complexes demonstrate that the ligand forms five membered metallocyclic structures with the complexed metal cation through one oxygen of the carboxylate group and the nitrogen from the oximino moiety. These complexes decompose cleanly within the range of 76 to 251$\sp\circ$C with simultaneous generation of the volatile decomposition products, water, carbon dioxide and acetonitrile. Based on these experimental data, a mechanism for the decomposition of the metal complexes of the $\alpha$-oximino carboxylate ligands has been proposed, which includes the formation of a six-membered cyclic transition state. It has been established that improvement of the solubility characteristics of these PAO complexes as well as lowering of their decomposition temperatures can be achieved by variation of the substituents R and R$\sp\prime$ in the molecule of the $\alpha$-oximino carboxylate ligand RC(=NR$\sp\prime$)COOH. One of these ligands t-BuC(=NOH)COOH was identified as exceptionally promising in terms of both solubility and low decomposition temperatures Precise stoichiometry precursors for ferrite and perovskite materials have been designed, which fix the metal to metal ratios by crystallization processes. High purity mixed metal oxalates of the type MTiO(Ox)2 $\cdot$ xH$\sb2$O (M = Sr, Ba) have been prepared in a simple procedure which includes ion exchange of the starting material K2TiO(Ox)2 $\cdot$ 2H$\sb2$O to the corresponding proteo-derivative H2TiO(Ox)2 $\cdot$ xH$\sb2$O and its subsequent reaction with Ba$\sp{2+}$ and Sr$\sp{2+}$ containing salts. These relatively insoluble mixed metal oxalates have been converted by reflux in an excess of methoxyacetic acid to methoxyacetates, having significantly higher solubility in water and organic solvents Precise stoichiometry mixed ferrite precursors have been prepared in a similar procedure, in which the readily available starting material NaFeEDTA has been ion exchanged to the corresponding proteo-derivative and subsequently reacted with water soluble salts of divalent metals such as Ni, Mg, Co and Cu. This procedure yields the mixed metal ferrite precursors as crystalline compounds in excellent purity without any sodium contamination The MOD approach has also been utilized for encapsulation of radionuclides into Synroc mineral phases. Three different MOD procedures have been designed which use different carboxylate ligands and encapsulation procedures. The first two approaches utilize NaPAO/disodium fumarate and sodium polyacrylate to precipitate the radionuclides and the Synroc forming elements from aqueous solution. Firing of this precipitate to ceramics results in the encapsulation of all but the alkali metal radionuclides into Synroc mineral phases. The third procedure involves conversion of the nitrate salts (in which form the radionuclides in radwaste are usually present) to acetates by reduction of the nitrate ions with excess acetaldehyde in acetic acid. Removal of the acetic acid solvent furnishes an amorphous acetate precursor, the pyrolysis of which at 800$\sp\circ$C leads to encapsulation of all of the radionuclides into the Synroc matrix. (Abstract shortened by UMI.) / acase@tulane.edu

This thesis introduces the Old River Control Complex (ORCC) and defines the existing problem of different water versus sediment diversions. Because this is a water control complex, where structures were built to keep the Atchafalaya River from taking over the Mississippi River and to generate power, it is crucial for the system to function properly to maintain a balanced sediment regime. The slightest changes in the sediment environment can be critical for the Mississippi, Atchafalaya, and Red Rivers, and for the Old River Outflow Channel itself. Scouring and deposition occurs due to an existing imbalance of sediment concentrations. Therefore, analyzing the available sediment data for stations in the vicinity of ORCC is important to understand the overall shifts of sediment occurring in this area. Stations defined as key sediment sampling stations in this vicinity are: Red River above Old River Outflow Channel, Simmesport, Coochie/Union Point, Tarbert Landing, and Old River Outflow Channel. If the sources for the shifts of sediment can be defined, additional recommendations for future handling methods can be made, and excessive scouring and deposition, which result in high maintenance costs, can be prevented. (Abstract shortened by UMI.) / acase@tulane.edu

Aerobic degradation of Saudi Arabian crude oil was conducted under various conditions representative of a coastal marine environment. Both bench-scale and laboratory-scale aerobic reactors were utilized to study the changes of intertidal soil contaminated with crude oil. Weathering experiments of the crude oil were conducted to gain insight into the degree of volatilization losses, and to quantify abiotic losses from biodegradation losses of the crude oil The bench-scale aerobic column studies indicated that Gulf of Mexico conditions were nutrient-limited during short term studies, and the total petroleum hydrocarbon (TPH) content of the soil was reduced sixty to seventy percent in five weeks with supplemental nutrients Aerobic laboratory-scale batch shaker flask studies were utilized for long-duration (seventy-eight week) experiments. Gravimetric loss of hydrocarbons ranged from eighty to eighty-nine percent under various conditions. Based on weathering tests, approximately twenty percent of this loss was attributed to volatilization. Supplemental nutrient additions did not increase the ultimate gravimetric loss of crude oil in the long-duration experiments. Significant degradation of the asphaltene fraction of the crude oil was observed in the long-duration studies / acase@tulane.edu

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