Flood Warning Systems are not a new commodity to the hydrologic world, however, the advancements in GIS data, hydrologic modeling tools, NEXRAD, and internet capabilities have allowed for improvements in flood prediction. This study applied techniques originally used in FAS-1 for a watershed in Houston, Texas to a large, highly sloped watershed in Austin, Texas where aquifer recharge is prominent. GIS was helpful in the framework of the model producing valuable hydrologic parameters and delineating the watershed. HEC-1 was used to create a model as the basis for a real-time radar based Flood Alert System. Advantages to the HEC-1 model are its ability to run in real time and the addition of gage-adjusted radar to the input. The HEC-1 model was tested and calibrated to various historical storms and is ready for real-time application. Together, these entities provide a strong foundation for the Flood Alert System in Austin, Texas.

The use of water-soluble fullerene-based compounds as sensitizers for reactive oxygen species (ROS) was investigated for the photodegradation of organic contaminants. A variety of conditions were evaluated to determine the production of ROS species by water soluble fullerene. Fullerol was an effective photosensitizer, particular under ultraviolet light. Fullerol produced a mixture of reactive oxygen species under both visible and ultraviolet irradiation. Evidence of both singlet oxygen and superoxide production was obtained. Water-soluble fullerene aggregates were not photocatalytic. Under dark conditions, fullerol appears to act as an antioxidant, while n-C60 had no antioxidant properties and under certain conditions may accelerate the production of ROS. Finally, it was demonstrated that membrane filtration can be used to separate the fullerene compounds from the process water. Nanofiltration membranes were used to remove fullerol from an aqueous solution. Fullerol rejection was approximately 98% and no fouling of the membrane was observed.

I performed traveltime tomography on a 3-D seismic refraction dateset collected at Hill Air Force Base, Utah in 2000. The survey covers a 95m by 36m area over a contaminated aquifer that is bounded below by a clay aquiclude, in which a paleochannel acts as a trap for the contaminants. Presented are results using an iterative, nonlinear, traveltime tomographic approach applied to 187,877 traveltimes. The resulting velocity model shows that the near-surface velocity increases by roughly a factor of 5 in the upper 15m, from about 300m/s to 1500m/s. Cross-sections through the model show a north-south trending low-velocity feature interpreted to be the channel structure. Checkerboard tests applied to the velocity model establishes a 7.5m lateral resolution throughout most of the depth range of interest. While the long wavelength features of the model reveal the paleo-channel, the velocity model is likely a broad and smooth characterization of the true velocity structure.

The premise that the structure of particle deposits can be predicted based on the knowledge of particle hydrodynamics, solution chemistry and surface chemistry of particles is explored in the framework of three environmental application areas: membrane filtration, in situ capping of contaminated sediments, and environmental sensing. The role of deposit morphology in membrane filtration was evaluated in bench-scale filtration experiments. Results from experiments were compared with theoretical expectations based on a mathematical model for permeate flux for limiting cases of dominant membrane and filter cake resistances. Microscopic examination of membrane cake cross-sections revealed a stratified structure and underscored the importance of coupling between hydrodynamic conditions and interparticle interactions for the permeate flux performance. The influence of suspension heterogeneity on the membrane cake structure was investigated in simulations of particle deposition. Particle Peclet number and collision efficiency were related to trends in colloidal deposit morphology as a function of particle transport and surface chemistry. The simulations identified potential limitations in modeling filter cakes as homogeneous material when suspensions are composed of several chemically distinct particulate fractions. The relationship between sediment cap morphology and transport characteristics across the cap were explored. Bentonite-cement composite is proposed as a new material for in situ capping of contaminated underwater sediments. In addition to being mechanically stable, such composites provide for a possibility to control cap microstructure through the fine-tuning of postdepositional hydration processes in the cap. Cement content and liquid-to-solid fraction were identified as two dominant factors that determine overall cap performance. Microscopic studies of composite structure, strength testing as well as numerical and laboratory modeling of diffusion across composite caps were used to establish formation-structure-performance links for the composites. Finally, the impact of variable deposit morphology on the efficiency of surface-enhanced Raman substrates was investigated. Ionic strength mediated silver nanoparticle deposition was explored as a route for the morphological design of optically active substrates for water quality monitoring. The critical dependence of the effect of surface-enhanced Raman scattering on the morphology of enhancing substrate was quantified as a basis for developing sensors with tunable sensitivity. Fractal analysis was used to quantify deposit morphologies and to correlate these to enhancement factors afforded by the substrates.

Reaeration, or the diffusion of O2 through the unsaturated zone and into an aquifer system, is a mechanism that influences the extent of hydrocarbon contaminant bioattenuation in ground water. A series of laboratory and numerical modeling experiments were completed to determine the amount of O2 supplied to an anaerobic aquifer by reaeration under various unsaturated zone conditions and to quantify the impacts of reaeration on the migration of hydrocarbon plumes in ground water. Results from laboratory experiments indicated that reaeration flux rates exhibited a bimodal distribution and either approached 12,000 Mg/M2-day or were less than 2,000 Mg/M2-day. Soil water content significantly affected the reaeration flux rate while soil type, soil O2 utilization rate, and unsaturated zone thickness did not influence the reaeration rate. In some cases, the capillary rise impeded O2 transport into the bulk ground water due to high water content near the base of the capillary region. An unsaturated zone transport model was developed to predict reaeration flux based on the effective diffusion coefficient of soil (Ds), liquid-side mass transfer coefficient (KL), Soil O2 utilization rate (Rsoil), and unsaturated zone thickness (z). Good agreement was generally found between the predicted and experimental flux results. Results from numerical modeling experiments indicated that reaeration reduced the steady-state length of hydrocarbon plumes in ground water for aquifer hydraulic conductivities of K = 10--2 cm/s and K = 10--4cm/s. Important groundwater reaeration parameters having an influence on the steady-state hydrocarbon plume length included the concentration of O2 in the overlying soil gas (C O2(g)), the ground water mass transfer coefficient (KL,GW), the vertical dispersivity in the saturated zone (alphav), and the zone of reaeration or the thickness of the top model layer (ZR). The relative importance of each of these parameters was on the order of alphav > > KL,GW > CO2(g) > ZR.

The Rice University Fine Particulate Matter Air Sampling Study (1999--2000) identified and quantified the fine particulate matter (PM2.5) in an urban setting in Houston, Texas. The study lasted over two time periods to characterize the seasonal changes; the summer period was between August 16, 1999 and October 1, 1999 and the winter period was between December 18, 1999 and January 31, 2000. PM2.5 was isolated with a cyclone separator and quantified through gravimetric analysis. The major gaseous species (SO 2, gaseous NO3, NH3) and chemical species (organic carbon, elemental carbon, SO42--, NO3 --, NH4+, Na +, K+, and Cl--) were collected by multiple types of filter media and analyzed by ion chromatography, gas chromatography, mass spectrometry, and thermal/optical carbon analysis. PM 2.5 concentration during the summer and winter periods was 8.2 +/- 0.6mug/m3 and 6.2 +/- 0.6mug/m3 respectively and did not exceed the NAAQS PM2.5 standard. The major particulate species (in terms of mass fractions in the summer/winter) were OC (39%/36%), SO4 (20%/9%), NH4 (8%/4%), EC (3%/3%), and NO3 (1%/7%). In both time periods, a large mass fraction was attributed to unknown materials (28%/38%). The OC, SO4, and NH4 mass fraction decreased from the summer to the winter while the NO3 and EC mass fraction increased. The organic fraction of the particulate matter contained n-alkanes and polycyclic aromatic hydrocarbons.

The harmonic mean, 7Q2 (7-day, 2-year low-flow), and 7Q10 are streamflow characteristics used to determine stream waste load allocations. Predictive equations for these characteristics of ungaged Texas streams are developed using multiple regression analysis to relate streamflow characteristics to basin parameters at 63 gaged streams. Gamma, LPIII (Log-Pearson type III), and mixed-LPIII distributions are used to predict the 7Q2's and 7Q10's. Basin parameters used in the analysis include contributing drainage area, channel length and slope, basin shape factor, precipitation, and hydrologic soil group. The harmonic mean regression equation included slope, precipitation, and area and had a higher adjusted R$\sp2$ than the 7Q2 and 7Q10 equations. Gamma 7Q2 and 7Q10 estimates yielded more reliable equations than LPIII and mixed-LPIII estimates. A region-based regression analysis yielded an even higher adjusted R$\sp2$ for the harmonic mean than the statewide equation, implying that regional regression equations may be more reliable than statewide equations for Texas.

There is often a fraction of contaminants in the subsurface which is observed to persist for long periods of time and resist removal. The phenomenon of incomplete or slow desorption has been shown in the laboratory for many different soil and sediment types and chemicals and a model was developed known as irreversible sorption. Hydrocarbon data from several field sites are compared to the linear and irreversible sorption isotherms and it appears that field data are described by a combination of the linear and irreversible models. A one-dimensional transport model which includes a linear or irreversible term for sorption generally predicts significantly lower concentrations with the linear term than the irreversible term. However, estimates of risk through groundwater and air exposure pathways decrease when sorption is described by the irreversible model. The combination of these factors with the uncertainties that remain presents a complicated problem for site management.

In industrialized countries, many aquatic environments are polluted with contaminants, such as metals. Metals can be found in the particulate matter of the sediment [1, 2]. Metals could be potentially dangerous to biota, if released. The metals can be released to the environment by oxidation due to resuspension (dredging). Neither the water column metal concentrations nor the sediment metal concentrations are good indicators of the amount of metals that will be available during a resuspension. A new method was developed, the new DRET test, to predict the amount of metals available during a six hour resuspension of anoxic sediment using an in-situ ChelexRTM resin as a constant adsorption-potential sink. This method was adapted from DiGiano's et al. [3] DRET test for use with metals instead of organic contaminants. The new DRET test could be used in the field to predict the possible metals available before a resuspension event occurred.

Supercritical water (SCW; above 374°C & 22 MPa) possesses the characteristics of non-polar solvents. It has been studied as a promising medium for decomposition of hazardous organics. Experimental research has been conducted to determine the phase behavior of SCW and organics in an oxidative environment via a Diamond Anvil Cell, coupled with a Fourier Transformed Infrared Spectrometer, an optical stereomicroscope and a high-resolution 3CCD camera. Homogeneous phases in H2O-O2, H2O-naphthalene and H2O-O2-naphthalene systems were identified. Flameless oxidation was observed to take place in the homogeneous phases. The chemical evolution and destruction rates of naphthalene/decachlorobiphenyl/cellulose during supercritical water oxidation (SCWO) were established using a batch reactor-based system, simulating practical conditions. Reaction pathways in SCWO were established for naphthalene, decachlorobiphenyl and the industrial sludge. They suggest the involvement of radicals in the reaction mechanism. In the proposed mechanism, ionic reactions were coupled with radical reactions. A significant role of intermediates during SCWO of organics is postulated and explained for the first time. A high activation energy of 139 kJ/mol indicated that the homogeneous SCWO of naphthalene was kinetic-controlled rather than diffusion-controlled. Complete elimination of typical noxious products NO x associated with hydrocarbon-air flames was confirmed in the SCWO of sludge wastes. / A new function describing H2O-O2 interactions under SCW conditions has been determined. It allows for calculations of the critical properties and phase behavior of SCW-O2 system. This function can be applied to determine the effect of pressure on the reaction rate constants in supercritical water.