Isotopic methods have been developed over the last 10 years as a method for determining chemical interactions of chlorinated solvents. These methods are especially promising for. This study attempts to employ and develop compound specific isotopic analyses of TCE and cDCE, along with chemical data, to characterize the degradation of TCE in a fractured bedrock aquifers. The Smithville site is a contaminated field site with extremely high levels of TCE contamination that is currently undergoing monitored remediation. From December 2008 until April 2010 extended samples were collected from the site to provide additional data analyses including isotopic data. The redox conditions at the site are anoxic to reducing, with sulfate reduction and methanogenesis as dominant terminal electron accepting processes. Redox data indicates that well electrochemical conditions are highly variable within the site, including areas near the source zone that not very reducing. Documented changes in groundwater conditions to much more reducing environments indicate that oxidation of organic matter is occurring at the Smithville site in select wells. Chemical analyses of TCE, DCE, VC, ethene and ethane are employed determine whether reductive dechlorination was occurring at the site. Results of field testing indicate that many wells on site, especially in the proximity of the source zone, dechlorination products were found. The isotopic data had a high range in both carbon and chlorine isotopes. Chlorine isotopic data ranges from a δ37Cl(TCE) of 1.39 to 4.69, a δ37Cl(cDCE) of 3.57 to 13.86, a δ13C(TCE) of -28.9 to -20.7, and a δ13C(cDCE) of -26.5 to -11.82. The range in values indicate varying degrees of degradation throughout the site, with the same wells grouping together. Combined chemical, redox and isotopic data shows that degradation seems to be a removal process for TCE at the Smithville site. Concentrations of chemicals created as a result of TCE degradation verify degradation, especially in wells 15S9, R7 and 17S9. Historically production of DCE in significant amounts, above 1.0 ppb, was observed to only occur after 2003. In addition to this, DCE data shows that the percentage of DCE made up of cDCE is above 96%. This indicates that microbes most likely mediate the processes that formed DCE from TCE. The linear regression of the delta-delta plot for isotopic TCE data shows line that is likely a direct function of the carbon and chlorine isotopic fractionation imparted upon the original TCE released. The slope found is consistent with data collected from other studies though cannot be applied to determining the process directly given the range of variability in isotopic field data.

In an event of a radiological dispersion device (RDD) detonated by terrorists in a high population density area, the hospitals and other medical facilities will be overwhelmed by people who may or may not have been contaminated by radioactivity. Under such circumstances, it would be desirable to identify people who have inhaled radioactive particles and direct them immediately for further treatment. A portable 3 by 3 NaI detector, which is widely available at most universities, was studied as a tool to identify and calculate the activity of unknown radioisotopes for such an RDD event.

Coral-based climate reconstructions typically have not used multiple cores from a region to capture and replicate a climate signal largely because of concerns focused on coral conservation, analytical expense, and time constraints. Coral Sr/Ca reproducibility through the 20th century was investigated using three intra-colony and three inter-colony coral records, from the reefs offshore of Amédée Island, New Caledonia. Different sampling resolutions were examined in coral Sr/Ca (fortnightly and monthly) and delta 18O (fortnightly, monthly, and seasonally) as well as similar scale subsampling of the daily in situ SST record. The mean coral Sr/Ca, delta 18O, and daily SST values do not change as a function of sampling resolution. The coral Sr/Ca signal is highly reproducible; the average absolute offset between coeval Sr/Ca determinations between any two coral Sr/Ca time series is 0.036 mmol/mol (approximately 0.65°C), which is less than twice the analytical precision of the coral Sr/Ca measurements. The stack average of the monthly coral Sr/Ca variations and monthly anomalies are significantly correlated with monthly in situ SST (r equals -0.95, -0.56, respectively) for the period 1967 to 1992 and monthly 1-degree gridded SST data product (r equals -0.95, -0.53, respectively) for the period 1900 to 1999. The coral Sr/Ca-SST reconstruction exhibits decadal-scale fluctuations that exceed those observed in the gridded SST time series, which may reflect true differences between the SST at a shallow reef site and those averaged over a 1-degree grid box or they may reflect inadequacies in the methodology used to create the gridded SST product when few observations are available. A warming trend of approximately 0.6°C is observed in the coral Sr/Ca-SST record. Monthly coral Sr/Ca records and seasonally resolved coral delta 18O record from this site share variance in the latter half of the 20th century, but not in the early 20th century, suggestive of a change in seawater delta 18O.

No description available.

No description available.

No description available.

As a result of the legacy of industrial contamination over the last century, areas of sediment deposition in the St. Lawrence River at Cornwall, ON, contain high concentrations of mercury (Hg). The popular sport-fish species, yellow perch (Perca flavescens) and walleye (Sander vitreus) have been found to contain mercury concentrations exceeding Ontario Ministry of Environment consumption guidelines. Interestingly, a paradox exists between two contaminated sites – despite elevated sediment Hg concentrations at Zone 2, fish from Zone 1 contain higher Hg concentrations. Further research has indicated that these patterns of Hg were not attributed to growth rate, condition factor, diet composition, or trophic position of yellow perch. Rather, Hg concentrations in yellow perch may be described by the heterogeneity of prey contamination and fish bioenergetics. As a result of the paradox between total Hg (THg) concentrations in sediments and biota between two contaminated sites, it was necessary to examine the benthic invertebrate community and how it may transfer Hg from sediments to yellow perch. This apparent paradox now extends to all prey items, since prey items from the stomach contents of yellow perch caught in Zone 1 were significantly more contaminated than those of Zone 2. Use of δ15N and δ13C, measures of trophic position and energy source, respectively, indicated that prey selection, but not food chain length, may also be an important factor in explaining the variation in Hg burdens in yellow perch. Small-scale patterns of biomagnification, as shown by a comparison of δ15N and logTHg, indicated that the rates of biomagnification were similar among zones, but the amount of THg present at the base of the food web was twice as high at Zone 1 as at other contaminated sites. Overall, the relative importance of vertical and horizontal food web structure changed spatially and temporally, highly influencing THg concentrations of prey items and yellow perch. / Thesis (Master, Biology) -- Queen's University, 2007-08-02 08:02:40.26

No description available.

Mass spectrometers are analytical instruments that convert neutral atoms and molecules into gaseous ions and separate those ions according to the ratio of their mass to charge, m/z. The measurement is reported as a mass spectrum: a plot of relative intensity vs. m/z that can be used to deduce the chemical structure and composition of materials and compounds. Initially, the use of mass spectrometers was restricted to the analysis of volatile compounds. Recent advances in the development of ionisation techniques to produce intact molecules directly from samples in the liquid or solid phase, has extended the powerful use of mass spectrometry to compounds of increasingly higher molecular mass. The aim of this study was twofold: develop diagnostic techniques for the in-situ measurement of isotope ratios in laser isotope separation experiments; and to correlate it with the measured isotope ratios on the collected product. The outcome is a thesis that can be divided into two distinct fields of application: Firstly; the Atomic Vapour Laser Isotope Separation (AVLIS) of lithium, and secondly the Molecular Laser Isotope Separation (MLIS) of uranium, In both AVLIS and MLIS pulsed laser systems were used to ionise and/or dissociate atomic or molecular beams. The pulsed nature of the lasers is ideally suited to in-situ time-of-flight detection of the produced ions. Different types of inter-changeable ion sources are common to the same TOF mass spectrometer. Each of these sources is selected according to its application. For instance, applications vary from photo- and multiphoton ionisation (laser ionisation) to surface analysis (laser desorption or particle bombardment) to chromatography (electron impact ionisation). Four different source configurations were considered in this study: (i) Atomic Laser Isotope Separation (AVLIS) of lithium; (ii) Multiphoton Ionisation (MPl) of UF6 gas; (iii) Non-resonant ionisation during Laser Desorption (LDI) of solids; and (iv) Matrix-Assisted Laser Desorption (MALD) of biopolymers. The design of each of these sources will be discussed in detail in chapters to follow. Bulk analysis of harvested laser-produced products needs to be in correlation with in-situ analysis. Three different characterisation methods were used in this study: (i) Laser Desorption Time-of-Flight Mass Spectrometry (LD-TOF-MS) (ii) Quadrupole-based Secondary Ion Mass Spectrometry (SIMS); and (iii) TOF-MS-based Secondary Ion Mass Spectrometry (TOF-SIMS). Chapter I describes the principles of time-of-flight mass spectrometry, design parameters, as well as the instrumentation that were designed and constructed for the purposes of this study. Chapter II describes the principles of Secondary Ion Mass Spectrometry (SIMS). In particular, research done on the establishment of tools to the non-expert user of SIMS to select analyses conditions, is described. Chapter III reports on the application of TOF-MS and SIMS during the AVLIS of lithium. Chapter IV reports on the application of the different combinations of TOF-MS, LD-TOF-MS, SIMS, and TOF-SIMS during the MLIS of uranium. / Thesis (Ph.D.)-University of Natal, Durban, 1999.

Isotopic methods have been developed over the last 10 years as a method for determining chemical interactions of chlorinated solvents. These methods are especially promising for. This study attempts to employ and develop compound specific isotopic analyses of TCE and cDCE, along with chemical data, to characterize the degradation of TCE in a fractured bedrock aquifers. The Smithville site is a contaminated field site with extremely high levels of TCE contamination that is currently undergoing monitored remediation. From December 2008 until April 2010 extended samples were collected from the site to provide additional data analyses including isotopic data. The redox conditions at the site are anoxic to reducing, with sulfate reduction and methanogenesis as dominant terminal electron accepting processes. Redox data indicates that well electrochemical conditions are highly variable within the site, including areas near the source zone that not very reducing. Documented changes in groundwater conditions to much more reducing environments indicate that oxidation of organic matter is occurring at the Smithville site in select wells. Chemical analyses of TCE, DCE, VC, ethene and ethane are employed determine whether reductive dechlorination was occurring at the site. Results of field testing indicate that many wells on site, especially in the proximity of the source zone, dechlorination products were found. The isotopic data had a high range in both carbon and chlorine isotopes. Chlorine isotopic data ranges from a δ37Cl(TCE) of 1.39 to 4.69, a δ37Cl(cDCE) of 3.57 to 13.86, a δ13C(TCE) of -28.9 to -20.7, and a δ13C(cDCE) of -26.5 to -11.82. The range in values indicate varying degrees of degradation throughout the site, with the same wells grouping together. Combined chemical, redox and isotopic data shows that degradation seems to be a removal process for TCE at the Smithville site. Concentrations of chemicals created as a result of TCE degradation verify degradation, especially in wells 15S9, R7 and 17S9. Historically production of DCE in significant amounts, above 1.0 ppb, was observed to only occur after 2003. In addition to this, DCE data shows that the percentage of DCE made up of cDCE is above 96%. This indicates that microbes most likely mediate the processes that formed DCE from TCE. The linear regression of the delta-delta plot for isotopic TCE data shows line that is likely a direct function of the carbon and chlorine isotopic fractionation imparted upon the original TCE released. The slope found is consistent with data collected from other studies though cannot be applied to determining the process directly given the range of variability in isotopic field data.