Environmental field analysis provides advantages that allow real-time decisions, interactive sampling and cost effective solutions to the problems faced at the time of investigation. Gas chromatography (GC), a widespread technique for the determination of organic pollutants in the environment, has also shown to be useful in environmental field analysis. Thermal desorption of solid environmental sample provides a technique for liberation of volatile analytes from the samples without the need for solvent extraction. Combining the thermal desorption technique with a field gas chromatograph (GC) thus provides the possibility of on-site determination of organic contaminants in soils. However, to better characterize trace level contaminants in complex sample matrices, laboratory analysis using analytical instrument with great separation and resolution power is required. Comprehensive two-dimensional gas chromatography (GC X GC) is such a powerful analytical tool that provides enhanced separation and resolution capacity for the task. The project presented here involves the development and validation of a field method for the analysis of total polychlorinated biphenyls (PCBs) in soils, and determination of individual PCB congeners in the same samples by further laboratory analysis. The field analytical system developed was a field portable GC interfaced with a thermal desorber. The identification of PCB congeners was realized by a GC X GC system with a time-of-flight mass spectrometer (TOF-MS) as a detector. The field method was developed by optimizing and characterizing the method using PCB standards, followed by the application of the developed method to environmental soil samples. Finally, analyses of PCB congeners in environmental soil samples were performed using the GC X GC system.

Environmental field analysis provides advantages that allow real-time decisions, interactive sampling and cost effective solutions to the problems faced at the time of investigation. Gas chromatography (GC), a widespread technique for the determination of organic pollutants in the environment, has also shown to be useful in environmental field analysis. Thermal desorption of solid environmental sample provides a technique for liberation of volatile analytes from the samples without the need for solvent extraction. Combining the thermal desorption technique with a field gas chromatograph (GC) thus provides the possibility of on-site determination of organic contaminants in soils. However, to better characterize trace level contaminants in complex sample matrices, laboratory analysis using analytical instrument with great separation and resolution power is required. Comprehensive two-dimensional gas chromatography (GC X GC) is such a powerful analytical tool that provides enhanced separation and resolution capacity for the task. The project presented here involves the development and validation of a field method for the analysis of total polychlorinated biphenyls (PCBs) in soils, and determination of individual PCB congeners in the same samples by further laboratory analysis. The field analytical system developed was a field portable GC interfaced with a thermal desorber. The identification of PCB congeners was realized by a GC X GC system with a time-of-flight mass spectrometer (TOF-MS) as a detector. The field method was developed by optimizing and characterizing the method using PCB standards, followed by the application of the developed method to environmental soil samples. Finally, analyses of PCB congeners in environmental soil samples were performed using the GC X GC system.

Electron-impact ionization of low-temperature water ice leads to H+, H2+, and H+(H2O)n=1-8 desorption. The threshold energy for ESD of H2+ from CI and H3O+ from PASW and ASW is 22 ± 3 eV. There is also a H2+ yield increase at 40 ± 3 eV and a 70 ± 3 eV threshold for ESD of H+(H2O)n=2-8 from PASW and ASW. H2+ production and desorption involves direct molecular elimination and reactive scattering of an energetic proton. Both of these channels likely involve localized two-hole one-electron and/or two-hole final states containing 4a1, 3a1 and/or 2a1 character. The 70 eV cluster ion threshold implicates either an initial (2a1-2) state localized on a monomer or the presence of at least two neighboring water molecules each containing a single hole. The resulting correlated two-hole or two-hole, one-electron configurations are localized within a complex and result in an intermolecular Coulomb repulsion and cluster ion ejection. The changes in the yields with phase and temperature are associated with structural and physical changes in the adsorbed water and longer lifetimes of excited state configurations containing a1 character. The dependence of the ESD cation yields on the local potential has been utilized to examine the details of HCl interactions on low temperature ice surfaces. The addition of HCl increases cluster ion yields from pure ice while decreasing H+ and H2+ yields. These changes reflect the changes in the local electronic potential due to the changing bond lengths at the surface of the ice as HCl ionizes and the surrounding water molecules reorient to solvate the ions. This work has been extended to ionic solutions at higher temperatures using a liquid jet and ultraviolet photoionization to interrogate the surface of aqueous ionic interfaces. Desorption of protonated water clusters and solvated sodium ion clusters were measured over a range of concentrations from NaCl, NaBr, and NaI solutions. The flux dependence indicated a multiple photon process and the proposed mechanism involves a Coulomb explosion resulting from the repulsion of nearby ions. The surface is investigated with regard to its importance in heterogeneous atmospheric chemistry.

The present research seeks to study the decrease in diffusivity rate as relative humidity (RH) decreases and modeling drying shrinkage of hardened cement paste as a poroviscoelastic respose. Thin cement paste strips of 0.4 and 0.5 w/c at age 3 and 7 days were measured for mass loss and shrinkage at small RH steps in an environmental chamber at constant temperature. Non-linear drying diffusion rate of hardened cement was modeled with the use of Fick's second law of diffusion by assuming linearity of diffusion rate over short drops of ambient relative humidity. Techniques to determine drying isotherms prior to full equilibration of mass loss, as well as converting mass loss into concentration of water vapor were developed. Using the measured water vapor diffusivity, drying shrinkage strain was modeled by the theory of poroviscoelasticity. This approach was validated by determining viscoelastic properties from uniaxial creep tests considering the effect of aging by the solidification theory. A change in drying diffusion rate at different RH was observed in the 0.4 and 0.5 w/c pastes at different ages. Drying diffusion rate decreases as RH drops. This can be attributed to a change in diffusion mechanisms in the porous media at smaller pore radius. Shrinkage modeling with an average diffusion coefficient and with determined viscoelastic parameters from creep tests agreed well compared to the shrinkage data from experiments, indicating that drying shrinkage of cement paste may be considered as a poroviscoelastic reponse.

Adsorption kinetics and adsorption-desorption of atrazine on organoclay composites prepared with the surfactant 6-piperazin-1-yl-N,N'-bis-(1,1,3,3-tetramethyl-butyl)-(1,3,5)triazine-2,4-diamine and Houston Black clay were studied using the indirect batch equilibration procedure. The organoclay composites sorbed significantly more atrazine than the Houston Black clay. Adsorption equilibrium was reached after 72 h for the organoclay composites. Atrazine adsorption isotherms were described by linear partitioning. The Koc values ranged from 605 to 5271 L kg-1 for the organoclay composites compared to a value of 41 L kg-1 for the Houston Black clay. The organoclay composite containing 20% surfactant on a total weight basis provided the most efficient adsorption of atrazine, although organoclay composites containing much lower amounts of surfactant also adsorbed significant amounts of atrazine. An average of 11% of sorbed atrazine was released during desorption. Characterization of desorption products showed only atrazine molecules being released from the organoclay composites.

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The thesis is divided into four sections. 1. Sample-first preparation: A method for surface-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of cyclic oligosaccharides¡GIn this work, we report the application of a sample first preparation method for the analysis of cyclic oligosaccharides when using bare AuNPs as the assisted matrix. In the sample first method, the analyte is deposited first and then followed by the bare AuNPs. The cyclic oligosaccharides, including £\-, £]-, and£^-cycodextrin (CD), are difficult to ionize by MALDI-MS, but they could be cationized very efficiently using bare AuNPs as matrixes in combination with a sample first preparation method. The sample first method not only provides high sensitivity for the measurement of neutral carbohydrate but also improves the spot homogeneity. This practical method was further validated by the analyses of biological samples, including neutral carbohydrate, neutral steroid, aminothiols, and peptides. 2. Gold nanoparticles as assisted matrix for detecting small biomolecules from high salt solutions through laser desorption/ionization mass spectrometry¡GThe neutral steroid and carbohydrates, which are difficult to be ionized by using MALDI, but cationized very efficiently by SALDI coupled with the sample first preparation method even if they are dissolved in a high-concentration NaCl solution. Under identical conditions, this practical method was further validated by the analysis of indolamines and peptides. It has also been utilized to analyze the small biomolecules in urine samples. 3. Phosphate-modified TiO2 nanoparticles for selective detection of dopamine, levodopa, adrenaline, and catechol based on fluorescence quenching¡GIn contrast to these studies, we report a simple approach for the selective detection of DA, L-DOPA, and adrenaline by phosphate-modified TiO2 (P-TiO2) NPs in the presence of fluorescein. After the binding of DA, the P-TiO2 NPs become neutral and even positively charged. The adsorption of fluorescein on the particles results in the quenching of fluorescein by TiO2-DA complexes, which have strong absorption at 428 nm. By monitoring the decreases in fluorescence at 520 nm for fluorescein, we calculated the limits of detection (LODs) for DA, L-DOPA, and adrenaline at a signal-to-noise (S/N) ratio of 3, which were 33.5, 81.8, and 20.3 nM, respectively. The results imply that the proposed methods have great potential for use in the selective analysis of catecholamines in biological samples and clinical applications. 4. Sodium hydroxide as pretreatment and fluorosurfactant-capped gold nanoparticles as sensor for the highly selective detection of cysteine¡G Under acidic conditions, fluorosurfactant (FSN)-capped AuNPs are aggregated in the presence of homocysteine (HCys) and cysteine (Cys) but not in the presence of cysteinylglycine, glutathione, and £^-glutamycysteine. When adding NaOH to a solution of HCys, the five-membered ring transition state is formed through intramolecular hydrogen abstraction. By contrast, it is difficult for Cys to form a fourmembered ring transition state after Cys has been pretreated with NaOH. As a result, the HCys-induced aggregation of the FSN-capped AuNPs is suppressed because the five-membered ring transition state exhibits relatively larger steric hindrance and has stronger interaction with the FSN molecules. Thus, we can discriminate between Cys and HCys on the basis of different aggregation kinetics. Under the optimum condition, we have validated the applicability of our method through the analyses of Cys in urine samples. It is believed that this approach has great potential for the detection of Cys in biological samples.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 105 p. : ill. Includes abstract. Includes bibliographical references (p. 100-105).

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references.

As part of the radioactive exercises taking place around the world anthropogenic radionuclides were introduce to Puerto Rico’s terrestrial and aquatic environments beginning in 1962. Two major projects took place in the island, the Rain Forest Project and the construction of a Boiling Superheat Nuclear Power Plant (BONUS). While in operation several accidental shutdowns occurred at the BONUS facility. One of these accidental shutdowns released 582 MBq into the nearby environment. Vieques an island located few miles east of the main island has received anthropogenic inputs of heavy metals resulting from military practices conducted by the US Navy. Due to the potential presence of Cs-137 in soils and sediments in Puerto Rico a radiological assessment was performed. Downcore soil and sediment analysis as well as surface samples analysis was conduct in these three sites indicating the presence of Cs-137. Activity range varies among site from below detection limit to 12 dpm/g at Vieques, 15 dpm/g at Espiritu Santo Estuary and 12 dpm/g at the BONUS Facility. ICP-OES analysis indicates the existence of an oxic environment at the sedimentary system of the island. Cs-137 retention is strongly influenced by particle grain size and at the study sites clay was present in less than 20% for most sites. An X-ray diffraction analysis show that kaolinite and smectite are present at all sampling sites and illite is absent. To further analysis the ability of soil and sediments to retain adsorption and desorption was conducted using clay reference material and samples from the island. All samples, reference and natural, used in the study were placed in an aqueous solution that contained MES buffer (5.0 micromol, pKa of 6.1), ammonium nitrate (0.010 M) and the five metals (individual concentrations ranged from 0.48 micromol to 1.6 micromol). Solution pH was adjusted by titration with acid or base, depending on the nature of the sample. Results were quantified as distribution coefficients. These results indicate that the absorption and retention of Cs-137 in the sediments in Puerto Rico is driven by the mineralogy of the site.