No description available.

Ph.D. / Environmental Science and Engineering / Chromate-containing precipitates can affect the mobility of toxic Cr(VI) in the subsurface, control its concentration in groundwater, limit its bioavailability, and impede remediation of chromium contaminated sites. This dissertation focuses on two iron-chromate precipitates, KFe [subscript 3](CrO4)[subscript 2](OH)[subscript 6] (the chromate analog of the sulfate mineral jarosite) and KFe(CrO4)[subscript 2].2H2O, that we identified in a soil contaminated by chrome plating solutions. The precipitates were identified using scanning and transmission electron microscopy, as well as powder x-ray diffraction. KFe[subscript 3](CrO4)[subscript 2](OH)[subscript 6] occurs as small (2-5 um) crystals interspersed within the bulk soil. KFe(CrO4)[subscript 2].2H2O forms crusts of larger crystals (10-50 um) in cracks and fractures of the soil. / Due to highly mathematical nature of the abstract, only the first paragraph is shown.

Background: Fraction of exhaled nitric oxide (FENO) is a promising non-invasive index of airway inflammation that may be used to assess respiratory effects of air pollution. We evaluated FENO as a measure of airway inflammation after controlled exposure to diesel exhaust or ozone. Methods: Healthy volunteers were exposed to either diesel exhaust (particle concentration 300 mu g/m(3)) and filtered air for one hour, or ozone (300 ppb) and filtered air for 75 minutes. FENO was measured in duplicate at expiratory flow rates of 10, 50, 100 and 270 mL/s before, 6 and 24 hours after each exposure. Results: Exposure to diesel exhaust increased FENO at 6 hours compared with air at expiratory flow rates of 10 mL/s (p = 0.01) and at 50 mL/s (p = 0.011), but FENO did not differ significantly at higher flow rates. Increases in FENO following diesel exhaust were attenuated at 24 hours. Ozone did not affect FENO at any flow rate or time point. Conclusions: Exposure to diesel exhaust, but not ozone, increased FENO concentrations in healthy subjects. Differences in the induction of airway inflammation may explain divergent responses to diesel exhaust and ozone, with implications for the use of FENO as an index of exposure to air pollution.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Inductively coupled plasma-mass spectrometry (ICP-MS) offers exceptional sensitivity and multi-element capability for trace metal analysis but the formation of polyatomic ions (particularly below m/z = 80) can cause, serious interferences. Such species can be introduced via precursor atoms in atmospheric gases, the sample matrix or impurities in the argon support gas. This thesis describes the development of a portfolio of analytical methods coupled with ICP-MS detection for the determination of trace metals such as manganese, cobalt, copper, nickel, zinc, mercury and lead in complex matrices such as sea water. A literature review of coupled techniques is given in Chapter one. Chapter two discusses the effect of sea water on the analytical performance of ICP-MS. Initial studies were carried out using a single channel flow injection (FI) manifold and included an investigation of the addition of nitrogen to the nebulizer gas flow of the ICPMS for the reduction of the ArNa* polyatomic ion interference at m/z = 63 on the Cu signal. This was followed by a multivariate simplex optimisation for the suppression of the ArNa* polyatomic ion interference at m/z = 63 and non-spectroscopic interferences affecting other masses in sea water, for the determination of Cu, Cr, Mn, Ni, Co, Zn and Pb. In Chapter three an on-line FI-ICP-MS matrix elimination method for the determination of trace metals such as Mn, Co, Cu, Zn and Pb in sea water is discussed. The method involved chelation of the analytes onto Chelex-100 or MetPac CC-1 iminodiacetate (IDA) .resin, with the simultaneous removal of indirectly interfering matrix species, particularly Na and CI ions. Results showing how the effects of the interferences were overcome, together with validation of the method by the analysis of open ocean, coastal and estuarine certified reference materials are reported. s Chapter four compares FI approaches coupled with AFS, ICP-AES and ICP-MS detectors for the determination of total mercury. Initial studies compared figures of merit for FI (conventional pneumatic nebulization) and Fl-cold vapour generation (CVG) coupled with ICP-AES and ICP-MS. Detection limits for total Hg were improved by developing simple on- and off-line preconcentration procedures using a MetPac CC-1 micro-column incorporated in a FI manifold vAth conventional pneumatic nebulization. An AFS detector was then used in the development of a method for the determination of total mercury with an on-line bromide/bromate oxidation step. In chapter five an LC-ICP-MS method for the speciation of Hg in sea water samples is described. The method involved the separation of mercury(II) chloride, methylmercury chloride and ethylmercury chloride on a Cig ODS stationary phase with an ammonium acetate/acetonitriIe/2-mercaptoethanol mobile phase. In order to achieve the necessary detection limits required for the determination of mercury in real sea water samples (< 50 ng r^), an off-line preconcentration method using a dithiocarbamate resin was used.

The objective of this study was to develop novel techniques for on-line sample pre-treatment for use with atomic spectroscopy. Preconcentration of the analytes using either complexation of the analyte(s) on an analytical column or by in-situ (in atomiser) trapping on a pre-coated graphite tube has been used. The samples were manipulated using flow injection analysis and detection achieved in most cases by ETAAS. All aspects of the study are supported by reference to the literature. Using the above approach, a new method has been developed to determine mercury in environmental (sediment) and biological (tuna fish) samples. This approach successfully achieved a sample throughput of 20-30 sample per hour, with a method detection limit of 0.2 ng g*^ (3a) and a precision of less than 10% at the 0.1 ug g"^ level. An interference study was conducted and seven elements ( As\, Cd", Cu", Ni", Pb". Sb'' and Se"") shown to give less than a 5% interference when the interferent concentration was 2 orders of magnitude greater than the Hg. Silver showed a 9% interference when one order of magnitude greater than the Hg. The technique of "in atomiser trapping" was applied to the determination of As, Bi, Sb and Se, in lake water samples. The hydrides were sequestrated upon an Ir coated graphite tube and the instrumental and chemical parameters optimised for multi-element determinations. Iridium has been identified as the best trapping material (coating) for multi-element determinations. The final method gave detection limits of 0.82, 0.04, 0,26 and 0.29 ug 1'^ (500 ul sample loop) for As, Bi, Sb and Se respectively. A characteristic mass of 177 pg for As, 91 pg for Bi, 107 pg for Sb and 90 pg for Se was achieved. Good agreement was obtained with certified and standard reference materials and the method was successfully applied to the determination of As, Bi, Sb and Se in lake water samples. Six elements (Cd, Cu, Fe, Mn, Ni and Pb) were selected for determination in seawater samples by multi-element on-line column preconcentration. The sample stream was mixed on-line with a buffered solution of diethylammonium dithiocarbamate (DDDC). and the metal-DDC complex retained upon a Cie RP silica column. Ethanol was then used to elute the metals from the column directly into the graphite tube. Disappointing results, were obtained due to interference problems, and although more work is required before this approach may be routinely used, it is shown to have potential for the future. Overall, this study has shown that novel methods employing flow injection methodologies for separation and preconcentration are a viable way to prepare environmental sample for analysis by ETAAS. Further it has demonstrated that multi-element analysis is possible for low levels of analyte despite the presence of troublesome matrices, although further work is required to achieve the ultimate goal of a universal method suitable for all analytes irrespective of the sample type.

Just as children eventually learn that covering their eyes does not make them invisible, we as adults have realized that just because harmful substances are "out-of-site" it does not necessarily mean they are gone for good. As we expanded our ability to think abstractly we began to consider how our actions affect our future and the lives of future generations. For example, we established procedures for the handling and disposal of high level radioactive waste and other hazardous materials because of the threat such materials pose to the environment. To date, however, the effect of atmospheric pollutants on groundwater supplies has been virtually ignored. Atmospheric pollution sources include, but are not limited to, smoke stack emissions, releases from power plants, weapons testing and manufacturing, fires, explosions, and deflation from tailings, spills and playas. This study evaluates the potential for groundwater to be contaminated by a point-source atmospheric emission. Pollutant concentrations in groundwater are estimated using a Gaussian model of atmospheric transport, a transfer function model for transport through the unsaturated zone, and a two-dimensional groundwater flow model based on Darcy's law to simulate transport in the saturated groundwater system. A sensitivity analysis of the composite atmospheric-groundwater transport model suggests that the most important factors influencing the susceptibility of a groundwater system to contamination by an aerosol source are: the concentration of the source, the amount of recharge, the depth to the water-table, and the velocity distribution in the unsaturated zone. This study indicates a significant potential for pollution of groundwater systems by aerosols. Shallow aquifers are especially vulnerable; however, deeper aquifers where rapid travel times through the unsaturated zone exist are also susceptible to aerosol contamination. / text

No description available.

This research was developed as one of the first studies to investigate riverine litter problems. Baseline assessment methods were formulated to define the scope and nature of this pollution form. Assessments were carried out in three catchments; the Taff East Lyn and Avill. The Taffwas found to be atypical regarding the extent of the litter. In all catchments plastic sheeting formed the principal litter component. The study also included an examination of the factors influencing the sources, pathways and sinks riverine litter pollution. These factors were drawn together through the development of a research model. Assessments of two quantifiable sources, sewage inputs through Storm Water Overflows (SWOs) and fly-tipping wastes, were undertaken. Greatest inputs of sewage-derived solids were introduced to the river through malfunctioning SWOs, the most numerous single component being sanitary towels. Whilst sewage-derived material constituted approximately 23% of all items on the River Taff large quantities of waste, especially plastic sheeting, originated from fly-tipping sites. Mobility of litter once introduced to the system was greatly dependent on river flow regimes. Some litter types, e.g. plastic sheeting, were more mobile than others and tended, after floods, to be stranded on vegetation. Due to its high profile within the catchments and expected longevity, plastic sheeting was chosen for river-bank degradation trials. Results indicated that photodegradation occurred within samples, but only in the initial exposure period and that any further breakdown was likely to result from physical abrasion. Marine areas were considered to be potential sinks for riverine litter, especially its more mobile components. An alternative sink for certain litter types such as cloth might be incorporation into the river-bank due to an ability to aggregate soil/sediment particles.