Browsing by Subject "elemental sulfur"

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    The Effects of Surfactants on Colloidal, Nanoparticulate, and Dissolved Sulfur
    (Office of the Vice Chancellor for Research, 2016-04-08) Kurek, Martin; Druschel, Greg; Gilhooly, William P., III
    Elemental sulfur is generally insoluble in water unless in the presence of a surfactant. This phenomenon was investigated by Steudel and Holdt in 1988 by filtering mixtures of sulfur, water, and surfactants through a 0.45 micron filter; however, since then sulfur nanoparticles smaller than 0.45 microns have been detected. The smaller than expected particle size suggests that the distribution of elemental sulfur in water with surfactants may be partitioned into colloidal, nanoparticulate, and truly dissolved components. Experiments have been conducted measuring the sulfur solubility in water with several chemical surfactants and varying filter sizes smaller than 0.45 microns. These experiments were conducted under equilibrium conditions with the solubility being measured using HPLC and square wave voltammetry. Kinetic studies detailing the solubility of sulfur with the surfactants over time have also been investigated. Data regarding the size and occurrence of sulfur nanoparticles present in water and the surfactants has been collected as well to give a complete description of the system under examination. Sulfur isotope fractionation of the dissolved sulfur species is also an interesting component of the system that is currently being investigated using stable isotope ratio mass spectrometry of 34S.
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    Fluorescence Measurements Of Phototrophic Sulfur Bacteria For Applications In Water Column Profiling
    (Office of the Vice Chancellor for Research, 2015-04-17) Gurdasani, Simran S.; Harper, Lynsie A.; Petrache, Horia I.; Ray, Bruce D.; Gilhooly, William P., III; Johnson, Merrell A.
    Unlike plants that produce oxygen during photosynthesis, phototrophic sulfur bacteria use sulfide and sunlight to produce carbohydrates and elemental sulfur. These bacteria require a unique aquatic environment to thrive: one that is anoxic (depleted of oxygen) and rich in hydrogen sulfide. Such conditions are found in a number of stratified lakes around the world including several in Northern Indiana. Studying the ecology and geochemical conditions that promote habitable conditions for phototrophic bacteria in lakes provides insight into the Early Earth (thought to be anoxic), ocean anoxic events of the Mesozoic (70-250 million years ago) and modern low oxygen conditions of coastal environments such as the Dead Zone of the Gulf of Mexico. However, locating and directly sampling these bacterial populations in vast bodies of water is not an easy task. In this project, we investigate fluorescent properties of purple sulfur bacteria in order to develop a dependable sensor that can be deployed in the water column. We report a number of measurements of purple sulfur bacterium fluorescence in the near infrared region when excited at discrete wavelengths in the UV range. We use these bench-top measurements to design a water-proof apparatus equipped with an absorption and luminescent detector for localization of bacteria in lake water. This device will be deployed in anoxic lakes of Northern Indiana to find the in situ water column position of phototrophic bacteria.
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    The use of dithiothreitol for the quantitative analysis of elemental sulfur concentrations and isotopes in environmental samples
    (Elsevier, 2018) Kurek, Martin R.; Gilhooly, William P., III; Druschel, Gregory K.; O'Beirne, Molly D.; Werne, Josef P.; Earth Science, School of Science
    Determining the concentration and isotopic composition of elemental sulfur in modern and ancient environments is essential to improved interpretation of the mechanisms and pathways of sulfur utilization in biogeochemical cycles. Elemental sulfur can be extracted from sediment or water samples and quantified by converting to hydrogen sulfide. Alternatively, elemental sulfur concentrations can themselves be analyzed using HPLC and other methodologies; however, the preparation and analysis times can be long and these methods are not amenable to stable isotopic analysis. Current reduction methods involve the use of costly and specialized glassware in addition to toxins such as chromium chloride or cyanide to reduce the sulfur to hydrogen sulfide. The novel reduction method presented here uses dithiothreitol (DTT) as a less toxic reducing agent to obtain both elemental sulfur concentrations and isotopic composition from the same sample. The sample is dissolved in an aqueous or organic liquid medium and upon reaction with DTT, the elemental sulfur is volatilized as hydrogen sulfide and collected in a sulfide trap using an inexpensive gas extraction apparatus. The evolved sulfide concentrations can easily be measured for concentration, by absorbance spectrophotometery or voltammetry techniques, and then analyzed for sulfur isotopic composition. The procedure is quantitative at >93% recovery to dissolved elemental sulfur with no observed sulfur isotope fractionation during reduction and recovery. Controlled experiments also demonstrate that DTT is not reactive to sulfate, sulfite, pyrite, or organic sulfur.