Browsing by Subject "coagulation"
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Item Characterization of marine exopolymeric substance (EPS) responsible for binding of thorium (IV) isotopes(Texas A&M University, 2005-08-29) Alvarado Quiroz, Nicolas GabrielThe functional group composition of acid polysaccharides was determined after isolation using cross-flow ultrafiltration, radiolabeling with 234Th(IV) and other isotopes, and separation using isoelectric focusing (IEF) and polyacrylamide gel electrophoresis (PAGE). Phosphate and sulphate concentrations were determined from cultured bacterial and phytoplankton colloid, particulate and colloidal samples collected from the Gulf of M??xico (GOM). Characterization of the 234Th(IV)-binding biomolecule was performed using ion chromatography (IC), and gas chromatography-mass spectrometry (GC-MS). Radiotracer experiments and culture experiments were conducted in determining the binding environment of the 234Th(IV)-binding ligand (i.e., sorption onto suspended particles), as well as the origin of the ligand in seawater systems. In all samples, 234Th(IV) isoelectric focusing profiles indicated that 49% to 65% of the 234Th(IV) labeled EPS from Roseobacter gallaeciensis, Sagittula stellata, Emiliania huxleyi, Synechococcus elongatus and GOM Station 4-72m was found at a pHIEF of 2 in the IEF spectrum. The carboxylic acid group appeared at the same pHIEF as 234Th(IV) for EPS from Roseobacter gallaeciensis, Emiliania huxleyi, Synechococcus elongatus and GOM colloidal organic matter sample. The phosphate group appeared at the same pHIEF as 234Th(IV) for EPS from Roseobacter gallaeciensis, and Synechococcus elongatus sample. The sulphate group was found at the same pHIEF as 234Th(IV) for EPS from S. elongatus and GOM colloidal organic matter sample. The total polysaccharide content was only 14% and 8%, uronic acids were approximately 5.4% and 87.1%, and total protein content was 2.6% and 6.2% of total carbon content of Sagittula stellata and Synechococcus elongatus, respectively. Monosaccharides identified in both Sagittula stellata and Synechococcus elongatus were galactose, glucose, and xylose in common. In addition, Sagittula stellata contained mannose and Synechococcus elongatus had galactoglucuronic acid. Thus, depending on the species, the size, structural composition, and functional groups of the 234Th(IV)-binding, acidic polysaccharides will vary. From these observations, it is concluded that the steric environment and not necessarily the exact functional group might actually be responsible for thorium-234 complexation to macromolecular organic matter. This research helped to improve our understanding of the observed variability in POC/234Th ratios in the ocean and provided insights into factors that regulate organic carbon export fluxes.Item The application of eccentric rotating cylinder apparatus for the improved study of particle coagulation(Texas A&M University, 2004-11-15) Lee, Chun WooConcentric rotating cylinder and turbulent mixing devices have been frequently used in studying mixing and particle coagulation. However, these apparatus develop simple laminar flow (concentric rotating cylinders) or do not have well-defined flow (turbulent mixing devices). In this work, the eccentric rotating cylinder apparatus was investigated to find applicability for the improved study of coagulation based on the modified analytical solution of Ballal and Rivlin. Various eccentricity ratios, rotation speeds and viscosities were simulated to obtain optimum operating conditions. Inertial forces working on the fluid increased as the eccentricity ratio and rotation speed increase. As inertial forces increase, the eddy developed in wide clearance was more skewed in the direction of rotation. Both root-mean-square velocity gradient and average principal strain-rate, were increased by increasing eccentricity ratio. avaerage principal strain-rate were linearly increased as rotation speed increases, which suggested that average prinipal strain-rate can properly represent mixing intensity. Comparison of average principal strain-rate and RMS velocity gradient revealed that RMS velocity gradient overestimated mixing intensity and its error increased as eccentricity ratio increases. This study showed that the eccentric rotating cylinder apparatus has a non-uniform velocity distribution with well-defined fluid dynamics. Therefore, the eccentric rotating cylinder apparatus can be applicable as a model flocculator. However, in order to achieve reliable model predictability, the fluid Reynolds number must be below 200.