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On-line HPLC/Spectrofluorometric techniques have been applied to the determination of polycyclic aromatic hydrocarbons (PAHs) in coal-derived products. The PAHs were isolated by preparative silica gel columns with a hexane mobile phase, and fractionated into five samples based on the number of condensed rings. Each fraction was separated by reverse phase HPLC with an acetonitrile/water mobile phase. Compounds were detected by means of on-line fluorescence detection. Naphthalene, pyrene, fluoranthene, benzo(a)anthracene and benzo(a)pyrene were verified by comparing the excitation and emission spectra obtained by a stop-flow technique with those of PAH standards. A Picramido bonded phase packing was prepared by the reaction of picryl chloride and amino bonded phase silica gel, forming a charge-transfer active phase. The retention mechanism of aromatic hydrocarbons on the picramido bonded phase column was studied in three ways: electronic effects (Hammett cr function); temperature effects on heats of adsorption and solvent effects on capacity factors. Chromatographic properties of the picramido bonded phase column were compared to those of silica gel and amino bonded phase columns. An on-line LC/LC column switching system was developed for PAH analysis of solvent refined coal (SRC). It utilized a guard column, an amino bonded phase, and a picramido bonded phase column. The guard column prevented the highly polar materials from entering the analytical columns; the amino bonded phase column separated PAH materials into groups based on an adsorption mechanism; the picramido bonded phase column separated PAHs based on charge-transfer mechanism, and provided better resolution. / Ph. D.

A groundwater monitoring study was conducted as part of a comprehensive program to remediate a former wood-preserving site that was contaminated with creosote. Twenty-five multi-level samplers (MLSs) were installed on-site and groundwater samples were collected and tested regularly between March 1998 and July 2000. Nearly one-thousand hybrid poplar trees were planted on-site in 1997 to help contain the groundwater plume and enhance phytoremediation. Ten polycyclic aromatic hydrocarbons (PAHs) were monitored along with several terminal electron acceptors (TEAs) and their reduced end products. The focus of the study was to determine the extent of natural biodegradation in the subsurface and assess the role of the poplar trees in site remediation. Since monitoring began, considerable progress has been made remediating the site and the contaminant plume has been shrinking consistently. PAH levels in the groundwater and soil have been reduced and individual MLSs show consistently decreasing contamination. At this point in the study it cannot be conclusively determined what impact the poplar trees are having on the progressing site remediation. However, there is a wealth of evidence indicating that natural biodegradation is playing a major role in site cleanup. Monitoring of TEAs indicates suggests that there are aerobic zones in the site aquifer, but that reduced conditions exist as well. Dissolved oxygen (DO) was found in many MLS ports, but other ports were devoid of both DO and nitrate and contained large quantities of aqueous Fe(II). Oxygen, nitrate and Fe(III) are being reduced on-site and data suggests that they are being used in the biological oxidation of PAHs. Although laboratory studies document the oxidation of PAHs under sulfate-reducing conditions, high aqueous sulfate values were recorded throughout the site, regardless of the level of contamination. Several possible mechanisms are proposed to explain the coexistence of high sulfate and PAHs in the site aquifer. The system may be redox-buffered by excess solid Fe(III) and Mn(III, IV) oxides. Also, dissimilatory sulfate-reducers are strict anaerobes and oxygen-rich rainwater may be toxic to them. The presence of a layer of coal below land surface creates pyrite oxidation conditions similar to those encountered in conjunction with acid mine drainage. The MLSs most affected by the coal layer have less PAHs and DO, lower pH, and higher sulfate and Fe(II) levels than other wells. The oxidation-reduction status of each MLS, based on oxygen, nitrate and Fe(II) measurements, appears to be closely related to the level of PAH contamination, suggesting that PAHs are the primary substrate being biologically oxidized in the site aquifer. These findings tend to support the general belief that the major limitation to natural biodegradation in subsurface environments is the delivery of adequate supplies of suitable TEAs to contaminated zones. / Master of Science

Experimental mole fraction solubilities of benzil, thianthrene, trans-stilbene, thioxanthen-9-one, diphenyl sulfone and dibenzothiophene sulfone are determined in pure noncomplexing and complexing solvents. Predicted solubility values are calculated for benzil, thianthrene, trans-stilbene and thioxanthen-9-one using expressions derived from Mobile Order theory. Large deviations between experimental and predicted solubilities in alcohol solvents exist, therefore optimized solute - solvent association constants are determined. Previously measured thianthrene solubilities in five binary alkane + cyclohexane solvent mixtures are compared with values predicted from Mobile Order theory using the measured solubility in each of the pure solvents as input parameters. The experimental mole fraction solubility of benzil in eight binary alcohol + 1-octanol solvent mixtures are also measured and compared with predicted values.

The objective of this study was to synthesize and characterize new energetic polycyclic "cage" compounds. As part of a program involved in the synthesis of new polynitropolycyclic compounds, 2,6-dinitro-5-methoxy- 7-carbomethoxypentacyclo[5. 3 .0 . 0* • * . CP • i ° . 0* •8]decane has been synthesized. This is a model system which can be used to study (1) the effect of nitro substitution on the photolability of carbon-carbon double bonds and (2) to develop methods for avoiding Haller-Bauer cleavage in cage /3-keto esters when synthesizing polynitro-substituted cage compounds.

Thesis (M.Sc. (Chemistry)) --University of Limpopo, 2017 / The presence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of major concern since these compounds are highly persistent, toxic and wide spread pollutants. The aim of this study was to evaluate the levels of PAHs in water and sediment samples collected from Blood and Mokolo Rivers in Limpopo Province, South Africa. Liquid-liquid extraction (LLE) was used for the extraction of PAHs from water, whereas PAHs in sediments were extracted using optimised microwaveassisted extraction (MAE). Furthermore, ultrasonication and a combination of ultrasonication and mechanical agitation were used for the extraction of PAHs from sediments samples. The quantification of sixteen (16) PAHs in water and sediment was carried out using gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode and by GC-flame ionisation detector (GC-FID). Concentrations of PAHs in sediments were higher than in water. The highest concentrations of PAHs were obtained in Mokolo River sediments, with the concentration ranging between 0.044 and 51.9 mg/kg. The levels of PAHs recorded in Blood River sediments were lower than those obtained in Mokolo River with concentrations ranging between 0.014 and 3.10 mg/kg. In water samples, higher levels of PAHs were observed in Mokolo River (between 0.0219 and 1.53 µg/L) while lower concentrations were recorded in Blood River (between 0.0121 and 0.433 µg/L). In water and sediment samples from both Rivers, higher molecular weight (HMW) PAH compounds (4-6 rings) were found at greater concentration levels than lower molecular weight (LMW) PAHs (2-3 rings), and this can be attributed to pyrogenic activities in the study areas. The efficiencies and accuracy of the methods for the extraction of PAHs were determined by assessing the recoveries of samples spiked with known amount of standards (for water samples), while a certified reference material (CRM) was used for sediments. Percentage recoveries ranged from 67.6 to 115% for LLE and 83.8 to 125% for MAE for both sample types. Diagnostic ratio was used for the source identification of PAHs in sediment samples. Several PAHs ratios indicated that both pyrogenic and petrogenic could be the sources of these compounds in both rivers. Toxic equivalency factors (TEFs) and benzo(a)pyrene equivalent (BaPE) were used to quantitatively estimate the PAHs potential human health risk. The assessment of ecotoxicological risk indicated that the v sediment samples collected from Mokolo River are at high toxicity risk while sediments from Blood River are at low sediment toxicity risk. / Water Research Commission (WRC), National Research Foundation (NRF) and Sasol Inzalo Foundation

During the past 30 years, numerous studies have focused on the toxicities of polycyclic aromatic hydrocarbons (PAH). Laboratory and field studies have helped elucidate the detrimental effects of these chemicals on growth, reproduction and immune response. Polycyclic aromatic hydrocarbons are in the priority list of chemicals to be studied by different governmental agencies and universities and understanding their mechanisms of action is the focus of the current research. The manuscripts presented in this dissertation are focused on the effects and mechanism of action of PAH on disease susceptibility. After a dietary exposure to PAH for up to 50 days (chapter II) and samplings after 3, 7, 14, 28 and 50 days, a number of biomarkers of PAH exposure were measured: Fluorescent aromatic compounds (FACs) in bile, ethoxyresorufin-o-deethylase (EROD) in liver microsomes, cytochrome P450 1A immunohistochemistry in liver and kidney and adduct formation in liver. Additionally markers of oxidative stress were measured: comet assay in blood, protein nitration in kidney and F2-isoprostanes in kidney. Oxidative stress was a probable factor in PAH induced responses in fish adapted to long-term PAH exposures and aryl hydrocarbon activation was not necessarily involved in this process. Disease challenge with Aeromonas salmonicida (chapter III) resulted in differences in mortalities that demonstrated that fish exposed to PAH were more susceptible to disease than fish not exposed to PAH. Determination of gene expression in head kidney of fish exposed and not exposed to PAH challenged with A. salmonicida using microarray and RT-PCR technologies 2, 4, 10 and 20 days after challenge (chapter IV), suggested that PAH exposure was associated with down regulation of interleukin 8, transport associated protein 1, NF-kB modulator, recombination activating gene and major histocompatibility complex II two days after challenge in fish exposed to PAH. The transcript levels were closer to control levels 20 days after challenge, this indicated a recovery from the effect of PAH exposure. / Graduation date: 2006