Accidental exposure to arsine (AsH₃) is possible in the semiconductor industry, metal mining, painting and herbicide preparation. First symptoms include intravascular hemolysis and dark red urine (hematuria), followed by abdominal pain, jaundice, and anemia. Exposure to AsH₃ is fatal in up to 25% of the reported human cases, usually caused by acute oliguric renal failure. The mechanism of AsH₃ toxicity in the kidney is unknown and was studied in vitro using established cell lines, primary cells, and isolated kidney. The hypothesis was that AsH₃ cause renal toxicity by its conversion to arsenite (AsIII). Renal cells were more susceptible to As(III) cytotoxic effects on ion homeostasis and cell integrity, but AsH₃ showed oxidative stress-like toxicity. Red blood cells were only susceptible to direct AsH₃ cytotoxicity. Hepatocytes, chosen because liver is also affected by AsH₃, were susceptible to both arsenicals. It was established that AsH₃ produce tissue specific toxicity. The toxicity of the AsH₃-produced hemolysate was also investigated. The complete hemolysate was toxic and this toxicity was associated with the soluble hemolytic products. AsH₃-induced nephrotoxicity was also studied in the isolated rat kidney. Unmetabolized AsH₃ was more toxic than hemolytic products in this system. Damage was found in the glomeruli, tubular epithelial cells, and vascular peritubular capillaries. Finally, the total amount of arsenicals produced by AsH₃ oxidation in the rat kidney and liver homogenates was determined. As(III) was formed four times as much compared to As(V) in the kidney. By comparison, the liver metabolized less than half of the arsenite formed by the kidney. In summary, in vitro systems were used to model tissue selectivity for AsH₃ toxicity and to investigate AsH₃ renal cytotoxicity. Red blood cells and hepatocytes were susceptible to unmetabolized AsH₃. AsH₃ was required to form As(III) to produce renal toxicity. The soluble hemolytic products produced by AsH₃ also contributed to the in vitro renal toxicity. Renal dysfunction produced by AsH₃ exposure (the cause for mortality), is caused by a combination of AsH₃-produced oxidative-stress toxicity and by cell integrity damage produced by As(III) formed from AsH₃ oxidation, and delivered to the kidney as soluble toxicants in the hemolysate.

This thesis studied empirically the air-handling etiology of the nonspecific symptoms of the eyes, respiratory tract, skin, and central nervous system in office workers, often termed the sick building syndrome. The results of a four-period crossover trial in 75 office workers suggest that 70% air recirculation when accompanied by an adequate intake of outdoor air can be used without causing adverse effects. A cross-sectional study of 2678 workers in 41 randomly selected office buildings from Helsinki metropolitan area provides evidence that mechanical ventilation, air conditioning, steam and evaporative humidification and air recirculation are risk indicators of studied symptoms in the existing Finnish office building stock. The results also suggest that outdoor-air ventilation rates below the optimal (15-25 L/s per person) increase the risk of the sick building syndrome symptoms with such sources of pollutants as present in mechanically ventilated office buildings. / Theoretical examination reveals that the sick building syndrome is a figurative concept of everyday language, rather than a singular disease entity. A theoretical model, the Office Environment Model, is presented to explain relations between the office environment and health.

Two field investigations were undertaken to study the role of water table management in reducing herbicide pollution of ground water. One of the three-year studies (1992-1995) was conducted in a sandy field near Joliette (Laurin farm), (Quebec) to monitor the herbicide metribuzin where potatoes were grown. Two water table management systems were evaluated, namely subsurface drainage and subirrigation. Soil and ground water samples were taken at two week intervals, once before and six times after the herbicide application. / The amount of rainfall received in the first few weeks following herbicide application is crucial in assessing the extent of ground water contamination. In 1992, fewer rainfall events occurred after the application as compared to 1993, so metribuzin leached slowly. In 1992, it appears that subirrigation reduced ground water contamination by a factor of 10 through enhanced degradation and the greater effect of dilution. However, the role of subirrigation in reducing the metribuzin contamination of ground water was negligible in 1993 due to considerable leaching soon after the application. / The second project was conducted in an organic soil in St-Patrice-de-Sherrington (Van Winden farm) where the herbicide prometryn was studied. Surface irrigation with a controlled water table was also used as a water table management system. One experimental unit was used for each of the three treatments (subirrigation, surface irrigation and subsurface drainage). / The herbicide application rate was greater at the Van Winden farm than in the Laurin farm (5.5 kg/ha versus 1.0 kg/ha). However, a higher adsorption coefficient of the organic soil minimized the leaching process. Ground water contamination was less extensive in the organic deposit. The effect of subirrigation in reducing ground water contamination was significant when the water table was shallow. Prometryn degradation was relatively slow during the summer. Moreover, significant amounts of prometryn carried-over into the soil after the winter season, so it appears to be a quite persistent herbicide in our climate.

Microbial antibiotic resistance is an emerging environmental pollution problem with deleterious effects on water supplies and human health. Currently, little is known about the role of environmental factors in the maintenance, propagation and attenuation of antibiotic resistance. This study investigated the effects of antibiotic exposure concentrations, nutrient availability, and microbial growth rate on resistance dynamics, as well as, the porous medium transport characteristics of antibiotic resistance vectors. Exposure to high antibiotic concentrations increased, (1) the percentage of resistant bacterial strains in soil, (2) the persistence of resistant strains in soil and (3) the relative abundance of resistance genes in bacteria; and decreased the Shannon Weaver diversity index. Rich growth medium enhanced resistance plasmid maintenance and stability even in the absence of selective pressure of the antibiotic possibly be alleviating the metabolic burden imparted on the carrier bacteria by the resistance plasmids. The growth rate exerted a strain-specific response on resistance dynamics, with higher plasmid instability (i.e., increased loss) observed at higher growth rates (Pseudomonas aeruginosa), but no such effect observed for an Eschericha coli strain. Resistance vector plumes may be enhanced by: (1) groundwater conditions conducive to plasmid coagulation and colloid formation of approximately 1 mum, and (2) high concentrations of resistant bacteria that exhibit fast initial deposition, and strong blocking behavior after matrix deposition. The results of this research suggest that decreasing environmental antimicrobial concentrations will be conducive to the attenuation of microbial antibiotic resistance, but may not be sufficient in completely eliminating the resistance reservoirs, thus additional control methods may be needed to minimize the impact of these pollutants. The results should also provide insight to improve regulatory and sustainability decision-making processes related to the use of antibiotic in animal agriculture.

Three experiments focused on the contribution of rice productivity to methane emission were conducted in Texas flooded rice paddy soils during 1994-95 growing seasons. Measurements of methane emission from different rice paddy soils during 1991-92 growing seasons (Sass et al., 1994) and from ten different cultivars in 1993 growing season (Willis, 1995; Sass and Fisher, 1995) were cited to quantify the relationships of methane emission with soil, rice cultivar and grain yield. Under the similar soil sand content and agronomic management regime, total seasonal methane emission was positively correlated with rice grain yield and aboveground biomass at harvest. Linear relationships of daily methane emission with aboveground vegetative biomass and root biomass were also observed. On a carbon to carbon basis, the ratio of methane emission to rice net primary productivity was dependent on soil and rice variety, and increased with rice plant development. Models emphasized the contributions of rice plants to the processes of methane production, oxidation and emission and also the influence of environmental factors were developed to predict methane emission from flooded rice fields. Relative effects of soil texture, soil temperature and rice variety on methane production/emission were quantified by three dimensionless indices: soil index, temperature index and variety index, respectively. Model validation against observations from various regions of the world, including Italy, China, Indonesia, Philippines and USA demonstrated that methane emission can be predicted from rice growth and development, cultivar character, soil texture and temperature, and organic matter amendments. Of these, rice growth and development is a principal parameter governing the processes of methane production, oxidation and emission in irrigated rice paddies. Model estimates suggest that annual amount of methane emitted from Chinese rice fields ranges from 7.03 to 13.32 Tg CH$\sb4$ yr$\sp{-1}$ with an average value of 9.45 Tg CH$\sb4$ yr$\sp{-1}$ under permanent irrigation and the majority of methane was emitted in the region located at latitude between 25$\sp\circ$ and 32$\sp\circ$ N. Comparisons of estimated with the observed emissions show that the estimates were in general close to the measurements at most locations.

A regional water resource model has been developed to simulate optimal water allocation patterns as both municipal and agricultural consumers respond to changes in water supply and rising salinity levels. Analysis of contemporary (1995) conditions indicates evidence of inefficiency in regional market institutions. The added security municipalities derive from higher prioritization of water rights is accompanied by economic inefficiencies in regional water allocation, particularly during drought. It is argued that removal of municipal protection would lower regional economic losses at small cost to municipal water users. Salinity damages to agriculture are modeled with attention to economic principles and a water-salinity-yield relationship that allows greater flexibility in water use with rising salinity. This approach differs from previous work and likely results in smaller reductions in regional net benefits as salinity increases. Empirical data support the use of this method as more accurate in estimating regional salinity effects. Analysis of optimal irrigator behavior indicates that employing surge technology for water intensive crops maximizes regional net benefits. Other more efficient irrigation technologies (relative to flood irrigation) do not enter into optimal solutions. Although useful as a conservation tool, more economically desirable irrigation strategies have little ability to mitigate salinity-related damages. Salinity-related damages in the municipal sector are conservatively estimated, but still sufficient to influence the economic desirability of reverse osmosis when salinity reaches specified thresholds. Salinity threshold for small municipalities (2 MGD) is 1195 mg/l, and for larger cities (12 MGD) 1655 mg/l. Results indicate that these damages can also play a role in determining target concentrations for TDS removal in finished water. Regional observations indicate that urban expansion coincides with the removal of large tracts of irrigated farmland. Current trends suggest the reduction in irrigated acreage makes water available at a rate that significantly outpaces any reasonable estimate of growing municipal demand. Under these conditions, water scarcity becomes less common and the impetus for more efficient and costly technologies is reduced. Projected salinity increases (from 900 to 1600 mg/l TDS) result in a relative decline in regional net benefits of 3--4% as compared with holding salinity fixed at contemporary levels. Following conclusions, five policy recommendations are offered for improving regional water resource development.

The ground in Houston is a shifting landscape of heavy clay soils, flat topography, and intense rainfall. When this environment is overlaid with fixed, man-made infrastructures, the two systems interact to exacerbate natural phenomena such as subsidence, faulting, and urban flooding. In response to an investigation into the relationship between Houston's infrastructure, its ground, and its climate, this thesis proposes the development of mid-scale flood control basins. Retention basins in the Houston area exist at the two scalar extremes: very large, regional facilities, and small, scattered, individual ponds. Generally, these facilities are not only inaccessible when flooding occurs, but also divorced from their surroundings; they are not designed to be used even when dry. In contrast, the proposed basins are enmeshed with a range of programs and infrastructures, designed to simultaneously accommodate urban life and water, and work to create a fluctuating character and intensity of program and activity.

This thesis addresses several key issues in the design of foam processes in porous media. Laboratory experiments were performed to identify the conditions for the generation of strong foam. They demonstrated that strong foam in homogeneous porous media is obtained above a critical dimensionless number that represents the point when there are sufficient lamellae to create discontinuity in all flowing gas paths. The critical number corresponds to a critical pressure drop that scales inversely with the square root of permeability. The results imply that mobilization and division is the primary mechanism for the generation of strong foam in homogeneous media. Effects of heterogeneity on foam generation and propagation are studied. Steady-state analysis suggests snap-off occurring near permeability increase due to the drop in capillary pressure. Experiments in homogeneous and heterogeneous sand-packed columns revealed that the foam mobility in the two cases could indeed differ by two orders of magnitude, due to snap-off for flow across an abrupt increase in permeability. This mechanism of foam generation is dependent on the degree of permeability contrast and the gas fractional flow. At low gas fractional flow, a permeability contrast of at least about 4 is necessary. Snap-off also occurs when the increase in permeability is gradual. In this case, small capillary number (e.g. low flow rate) is required. A simple foam model was developed and incorporated into an existing reservoir simulation package. In addition to a fixed increase in foam effective viscosity---a feature that is common in many previous models, the increase in trapped gas saturation during imbibition is included. The latter is critical to model diversion in surfactant-alternating-gas processes. Observations from a field-scale foam application for aquifer remediation were reviewed. The reservoir simulator that included the foam model was successfully utilized to simulate the process and interpret its results. The field results are consistent with the conditions for strong foam and the effects of heterogeneity identified in the laboratory. Simulations indicated that foam mobility in the vertical direction, which is generally perpendicular to stratification, was about 1 to 2 orders of magnitude less than its horizontal mobility. The reduction in vertical mobility due to snap-off in stratified media implies that foam in field-scale processes should propagate farther than previously thought.

In Micellar-Enhanced Ultrafiltration (MEUF), a surfactant is added to a wastewater stream containing an organic solute. Most of the solute is solubilized in micelles, which are aggregates of surfactant molecules, formed in the feed solution. Separation is achieved through retention of the micelles by an ultrafiltration membrane. Since much of the solute is within the micelles, a membrane with a molecular weight cut off (MWCO) much larger than the molecular weight of the solute is used. Although some unsolubilized solute and surfactant monomers pass through the membrane, the use of a surfactant with a low critical micelle concentration (CMC) ensures little contamination of the permeate by surfactant monomers. / Solubilization tests and MEUF experiments were performed with an aqueous feed solution of benzoic acid (molecular weight 122) and Rhodameen T12/90 (molecular weight 798), a twin-head, cationic tertiary amine surfactant. This surfactant has an 18 carbon hydrophobic tail and two hydrophilic polyoxyethylene heads. The equilibrium solubilization of benzoic acid by surfactant solutions was measured by semiquilibrium dialysis. The maximum solubilization was nearly one mole of benzoic acid per mole of Rhodameen. / MEUF was carried out in hollow fiber polysulfone membrane units with MWCO of 5,000 and 30,000. The permeate flux and overall rejection of benzoic acid and surfactant were measured for different initial feed compositions and initial surfactant concentrations under varying transmembrane pressures (TMP). The flux increased with TMP and decreased with Rhodameen concentration, but was not affected by the benzoic acid concentration. The highest rejections of benzoic acid (90%) and Rhodameen (95%) were obtained when the molar ratio of surfactant to solute in the feed was 1.2.

The sorption/desorption behavior in soil/water systems of $ sp{14}$C-radiolabeled naphthalene and nine of its nitrogen-substituted derivatives; quinoline, isoquinoline, quinoxaline, 1-aminonaphthalene, 2-aminonaphthalene, 1-amino-2-methylnaphthalene, 1-nitronaphthalene, 2-nitronaphthalene and 1-nitro-2-methylnaphthalene were investigated with respect to their physico-chemical properties and the type of interaction they form with soil organic and mineral matter. In turn, an investigation into the effect that sorption/desorption has on the bioavailability of these organic compounds and their mineralization kinetics was conducted. / The non-polar naphthalene, the slightly polar quinoxaline and the three nitronaphthalene compounds sorbed through hydrophobic interaction giving rise to linear sorption isotherms that are typical of partitioning processes in which organic matter functions as a partition medium. Amino-naphthalenes, being polar and slightly basic, adsorbed through cation exchange, hydrogen bonding and formed coordination complexes at soil organic and mineral matter surfaces. Quinoline and isoquinoline, due to their relatively high dipole moment, intercalated the interlamellar space of layered-soil minerals. However, quinoline did not exhibit a specific type of interaction in the interlamellar region, while isoquinoline molecules adsorbed specifically, probably through surface protonation or coordinate covalent bonding with metal ions, and produced micelles upon sorption between the basal planes of clay particles. The discrepancy between the sorption behavior of quinoline and that of isoquinoline is attributed, in part, to the stronger hygroscopic nature of the former compound, its lower acidity constant and to the asymmetric shape of its molecules. / The desorption behaviors of naphthalene and 1-nitro-2-methylnaphthalene, both yielding concave up desorption isotherms, show a readily reversible component that gradually gives way to an irreversible one. The -CH$ sb3$ group, in the case of 1-nitro-2-methylnaphthalene, reduced hysteresis which is attributed to an increase in the hydrophobicity of the molecule and the steric effect that the methyl substitution has on hydrogen bonding. Desorption of quinoline and isoquinoline followed a hysteresis loop (concave down desorption isotherm) such that reversibility increased with decreasing soluble concentrations in the aqueous phase. Amino-naphthalenes adsorbed irreversibly at soil surfaces which is suggestive of strong interaction forces resembling those of a chemical reaction. / The mineralization of all studied compounds gave rise to hyperbolic mineralization curves comprising two phases; an initial fast one followed by a second slow phase with gradually declining rates. / Quinoline maximum mineralization rates were first order with respect to soluble concentrations and the amounts of quinoline mineralized initially coincided with the soluble fraction. In contrast, the amounts of isoqoinoline mineralized during the fast phase exceeded its corresponding fractions in solution. Mineralization exhibited saturation-type kinetics (Michaelis-Menten type) which probably indicates that the biodegradation of isoquinoline was mediated by its sorption in the micellar form. / Finally, naphthalene maximum mineralization rates correlated linearly with total concentrations (soluble and sorbed) and the total amounts mineralized during the fast phase exceeded substantially the soluble fraction. (Abstract shortened by UMI.)