This study localizes dimensions of freshwater salinization by directly measuring chloride concentrations in ungauged urban streams, assessing the relationship between chloride, copper and zinc in sample data, measures statewide trends for Iowa, and considers the regulatory and cultural environment of managing winter roads. Chloride concentrations in local, urban streams generally persist at higher levels than what is typical of natural Iowa waters. Runoff from snow melt events violate water quality standards, with chloride concentrations more closely resembling sea water than freshwater. Meanwhile, long-term trends at the statewide scale suggest levels are decreasing over time. Dissolved ions in groundwater from limestone aquifers encourage chemical buffering. Surface runoff in urban areas does not contain groundwater but does contain a large amount of salt from roads and other sources. More salt present year-round in streams influenced by surface water hydrology likely increases the potential for storm sewers, bridge decks and other urban infrastructure to corrode. Public agencies take varied approaches to freshwater salinization and related concerns. Regulation focuses on drinking water protection, and accounts for both household and industrial chloride sources. Snow and ice “fighters” see chloride as a tool, whereas scientists and regulated agencies consider it a pollutant of concern. This split leads to inconsistent patterns in decision-making and prioritization. Salt is a commodity, generating billions of dollars for suppliers throughout North America. Industry can play a significant role in solving what may ultimately become one of the most challenging water quality problems of the 21st Century.

Corrosion can take place as chloride ions accumulate above a critical concentration (CT) at the surface of a reinforcing bar inside concrete in marine service. The initiation of corrosion can be delayed by polarizing the steel cathodically, which is known to increase the value of CT. That effect is the basis of the cathodic prevention (CPrev) method to control corrosion of reinforcing steel in concrete. However, concrete cracks are a common occurrence and at cracks, the buildup of chloride ions is accelerated to the extent that CPrev may be less effective. The findings from an ongoing investigation to determine the effectiveness of cathodic prevention on cracked concrete exposed to a marine environment are presented. Experiments were conducted on reinforced concrete blocks with controlled-width cracks placed along the length of a central reinforcing steel bar. A ponding area on top of each specimen allowed for cyclic exposure to a 5% NaCl solution to imitate a marine environment. Crack widths ranging from 0.01 inch to 0.04 inch and polarization levels ranging from -330 mV to -540 mV were used. The onset of corrosion as a function of time of exposure was determined by measurements of the cathodic current demand needed to reach each target polarization level. The ranking of time to onset of corrosion was used as an indicator to determine how much cathodic prevention is necessary to effectively extend the life of cracked concrete. Results to date suggest that a minimum cathodic polarization level in the range of -540 mV would be needed.

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The catalytic hydrogenation of an aromatic sulfonyl chloride was investigated in continuous and semi-batch mode processes using a Robinson-Mahoney stationary basket reactor. A complete experimental unit was designed and built. The operating and analytical procedures have been developed and the methodologies to gather the kinetic data have been described. Hydrogenation reactions were conducted at a reaction pressure of 364.7 psia, at three different reaction temperatures: 85 °C, 97 °C and 110 °C, at five different residence times: 0.6 (only at 110 °C), 1.0, 1.5, 2.0, 3.1 hr, with the hydrogen to the aromatic sulfonyl chloride molar ratio: 8.0 mol/mol and hydrogen to argon molar ratio: 3.0 mol/mol. Intrinsic reaction rates of the reacting species were obtained on the surface of a commercial 1 wt% palladium on charcoal catalyst. The conversion and molar yield profiles of the reacting species with respect to process time suggest a deactivation of the 1 wt % palladium on charcoal catalyst. Kinetic data collected in a continuous process mode show that the catalyst is deactivated during an experiment when the process time equal to two to three times the residence time of the liquid within the reactor. XRD analysis shows that the active sites are blocked and an amorphous layer was formed on the surface of the palladium catalyst. Semi-Batch mode experimental data were obtained at 110 °C after 8 hours of reaction time for several aromatic sulfonyl chlorides. A kinetic model has been developed, which includes adsorption of individual components and surface reactions as well as rate equations of the Hougen-Watson type. A hyperbolic deactivation function expressed in term of process time is implemented in the Hougen-Watson equation rates. The mathematical model consists of non-linear and simultaneous differential equations with multiple variables. The kinetic parameters were estimated from the minimization of a multi-response objective function by means of a sequential quadratic program, which includes a quasi-Newton algorithm. The statistical analysis was based on the t- and F-tests and the simulated results were compared to the experimental data.

Thesis (Ph. D.)--School of Civil and Environmental Engineering, Georgia Institute of Technology, 2004. Directed by Frank E. Löffler. / Vita. Includes bibliographical references (leaves 182-200).

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No description available.

Glutamate-gated chloride channels (GluCl) belong to then icotinic ligand-gated ion channel family and are thus assumed to be heteropentamers. Each subunit contains a large extracellular N-terminal domain, four transmembrane domains (TM1--TM4), and an extracellular C terminal. Caenorhabditis elegans expresses various GluCl channels formed by alpha1, alpha2, alpha3, alpha4 and beta subunits. The best understood GluCl channel is expressed in pharyngeal muscle cells where it mediates response to the M3 motor neuron. alpha2 forms this channel, probably in association with beta. The alpha2 mutant lacks M3 neurotransmission which can be rescued by pharynx-specific alpha2 expression. My results show that alpha1 and alpha3 subunits cannot substitute for alpha2. Formation of chimeric constructs of alpha1, alpha2 and alpha3 pinpoints the M1--M3 transmembrane region of alpha2 as the minimal rescuing domain. This region may therefore be important for localization or, in association with another subunit, in the formation of the active channel.