A computational approach was utilized to evaluate the degree to which Zn(II), Cd(II), Hg(II), and Pb(II) hydrolyze and complex with chlorides at pH and chloride concentration levels encountered in natural waters and soil solutions. The significance of hydroxy and chloride complexes of these heavy metal ions is discussed in relation to solubilities of sparingly soluble salts, Hg(II) adsorption on clays, and Hg(II) interactions with organic functional groups. Occurrence of and competition between Hg(II) hydroxy and chloride complexes is important at all pH and chloride concentrations encountered in natural waters. Hydrolysis of Pb(II), Zn(II), and Cd(II) increases markedly above pH 5, 7, and 8, respectively, and the chloride complexes are important above chloride concentrations of approximately 10⁻² M. Hydrolysis and chloride complexation increases the solubilities of sparingly soluble salts of these heavy metal ions by deca-orders depending on the degree of complexation. Intrinsic solubilities of the heavy metal hydroxides are greater than the solubilities obtained from the corresponding solubility products, except for Cd(OH)₂° The effects due to complexation may in many cases overshadow salt effects. Studies on Hg(II) adsorption by Montmorillonite (53 mg/10 ml), vermiculite (47 mg/10 ml), and kaolinite (182 mg/10 ml) showed that at Hg(II) levels of 0.1, 0.5, 2.5, and 5.0 ppm adsorption was low but increased with increase in Hg(II) concentration. Highest amount of Hg(II) adsorbed was 0.3 mmoles per 100 g clay at the 5 ppm level and in the presence of vermiculite. Lowest adsorption was with kaolinite. Equilibrium pH and pCl measurements indicate that Hg(OH)₂° was the main species present. Lower adsorption by kaolinite could not be assigned solely to clay difference since the proportion of HgCl₂° in the equilibrium solution was higher than for the other two clays. Highest percentage of added Hg(II) adsorbed was attained at 0.5 ppm level for montmorillonite and vermiculite and at 2.5 ppm level for kaolinite. When Hg(II) existed as HgCl₄ in the equilibrium solution there was a tendency towards negative adsorption (repulsion). At Hg(II) levels of (25-1000 ppm) HgCl₂° in the equilibrium solution did not exchange any significant amounts of exchangeable Ca. Potentiometric titrations were performed first on Hg(II)-chloride solutions after an iterative procedure was developed for predicting such titrations. Titrations of Hg(II) in presence of different chloride concentrations were quantitative and followed the predicted course. The titrations of Hg(II) in presence of resin and peat at various chloride concentrations indicated that chlorides compete effectively with the organic functional groups for Hg(II). However, at the same time unexpected acidity sources were apparent at the higher chloride concentrations. Possible origin of such acidity has been postulated. The potentiometric titrations showed that more research is required in order to obtain a full understanding of the various acidity sources especially when organic and inorganic complexes are present. / Ph. D.

Saline soils in the Dry Valley region of McMurdo Sound, Antarctica, contained bacteria showing salt tolerance or requirement. Soils were plated by the spread plate method on soil extract-peptone-yeast extract media to which sodium chloride had been added in concentrations from 0 to15 per cent (w/v). Bacteria isolated from these media at 2 °C, 5 °C, and 15 °C were predominantly Gram negative rods with few Gram positive rods and cocci. No filamentous fungi or Halobacterium spp. were observed on the media used. At 15 C there were no isolates from media containing greater than 15 percent added salt; however, counts of 1.4 x 10³ colonies per gram of soil were found at this concentration. As the incubation temperatures were lowered, salt tolerance was lowered. The data indicate that the limited soil microflora observed in saline soils and ponds may be attributed to a combination of low maximal summer temperature and high salinity. / Master of Science

Heat causes breakdown of the water containing colloid gel structures. This phenomenon, known as heat syneresis, has been shown to be effective as an aid to dewatering municipal sewage sludges. Samples of primary sludge, and 1:1 mixtures of primary plus activated sludges, and primary sludge plus trickling filter humus were heated to various temperatures for a variety of holding times. The heat treated sludge was then cooled and its dewaterability measured by both filter leaf and specific filtration resistance tests. The primary sludge exhibited a marked improvement in filterability when held at a temperature of 170 to 185 °C for 20 minutes or more. The 1:1 mixture of primary and activated sludges showed this excellent dewaterability when held at temperatures as low as 145 °C for 20 minutes. Very little increase in filterability was noted when the holding time was increased to 40 minutes. The mixture of primary sludge and trickling filter humus showed no such improvement when heat treated at any of the typical good conditions for the other mixtures. Design and cost evaluations of two plant scale systems (one with high pressure sludge pumping; one without) for heat treating domestic sludge show the process to be economically feasible for a design population of 100,000 persons. The annual cost of the heat treatment system was estimated to be one and one-half times that of conventional anaerobic digestion followed by lagoons or sand beds and approximately 50 to 75 per cent of the annual cost of present sludge treatment by vacuum filtration. The easier handling of the heat treated sludges and the economics of the synereis operation could have an important influence on the design, cost, and operation of waste treatment plants in the United States. / Ph. D.

This thesis investigates the main issues to be considered in designing an airport for the present and the future. Points for consideration include a review of the: • Changes in airport design and their effect on airport planning and air transportation • Effects of the airline industry on a community; for example, noise effects, potential for future growth, etc. • Additional services that should be provided by airport facilities other than passenger handling • Complex nature of the facility, in addition to the need for design flexibility • Basic airport configurations and their characteristics In addition, Roanoke Municipal Airport was selected as a design exercise. The new facility was planned as a regional airport for the year 2000. This part of the study includes the plan, which is a description of the design process, the program which discusses in detail the requirements for the airport facilities, and the actual design which is illustrated by models and drawings. / Master of Architecture

This dissertation presents several empirical tests to measure the relative abilities of alternative models in capturing the unobservable process by which economic individuals may form expectations of future inflation. Three empirical representations of the inflation expectations process are tested: an autoregressive model which uses only past inflation data; a rational expectations model which utilizes the structural economic relationships in the economy (excluding past inflation); and a general model which exploits both the information sets just described. These competing approaches are each subjected to tests for rationality and predictive accuracy. The rationality tests employed in this study are the breakpoint test suggested by Sargent and the incorporation of each model's inflation predictions into an analysis of the Fisher equation. To gauge the predictive accuracy of each model, post-sample extrapolations were generated and compared by means of the root-mean-squared error and Theil inequality coefficient. The outcome of these various tests provides support to the contention that, for an individual attempting to obtain optimal (error minimizing) forecasts of future inflation would select the relatively simple autoregressive model over the rational expectations or general approaches. In three out of four tests presented, the autoregressive model performed as well if not better than its more informational intensive competitors. / Ph. D.