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The movement and fate of heavy metal inputs (Cd, Zn, Mn, Cu, Al, Fe, Pb, Ni and Cr) from highway runoff were investigated in a three-year study on 1.3 hectare retention facility near the Maitland Interchange on Interstate 4, north of Orlando, Florida. Physical characteristics of the retention pond and surrounding watershed were defined and field instrumentation was installed. Stormwater samples were collected over a one-year period, representing a wide range of intensities and antecedent dry periods. Stormwater characteristics were compared with average retention pond water quality to determine removal efficiencies for heavy metals within the pond. A total of 138 core samples were collected in the pond over a three-year period to investigate the horizontal and vertical migrations of heavy metals within the pond. Sediment core samples were also carried through a series of sequential extraction procedures to examine the type of chemical associations and stability of each metal in the sediments. An apparatus was built which allowed sediments to be incubated under various conditions of redox potential and pH to investigate the effects of changes in sediment conditions on the stability of metal-sediment associations. Five groundwater monitoring wells were also installed to monitor metal movement and accumulations under stormwater management systems. Heavy metal inputs from highway runoff were found to be predominantly particulate in nature, with dissolved fractions for most metals of only 25 percent. Upon entering the retention pond, most metal species settled into the sediments within 60-90 m of the inlet. Removal efficiencies for metals after entering the pond averaged 70-90 percent for particulate species and about 50 percent for dissolved species. Sediment concentrations of heavy metals were highest near the surface, with rapidly decreasing concentrations with increasing depth. Metal-sediment associations appear to be very strong for most metals, with the vast majority of metal inputs into the pond over the eight-year life still remaining in the top 10 cm. Concentrations of all heavy metals measured were higher in groundwaters beneath the pond that in the pond water; but for most metals, the increases only extended to depths of 1-3 m beneath the pond. In general, metal concentrations beneath swale areas were significantly higher than concentrations beneath the retention pond. Due to slow groundwater movement in the area, the effects of increased metal concentrations are very localized. Evidence was presented to suggest that mobilization of metals into groundwaters could substantially increase with time if maintenance procedures are not conducted.

ABSTRACT Continuous flow column studies were conducted to characterize suspended sol ids and heavy metal reduct ions through sedimentation with varying overflow rates. The heavy metals tested were cadmium, zinc, copper, iron, lead, nickel and chromium. Stormwater derived samples spiked with street sweepings categorized into particle size ranges less than 500 microns in diameter were utilized in the research. Overflow rates investigated ranged from 28 to 3600 gallons per day per square foot. Theoretical predictions of suspended solids reductions with the application of Stoke's Law exceeded observed reductions for the continuous flow system. Performance curves for all reductions over the observed range of overflow rates are described by a parabolic relationship with the general equation as follows: Reduced fraction= a+ b(Overflow Rate - c) 2 where a, b and c are constants specific to each parameter. Similarities in performance curves for all metals indicate a dependence on suspended solids for reductions. Cadmium and chromium reductions were a function of overflow rate, but did not show a statistically significant dependence on initial total suspended solids concentration. Lead, copper, zinc and iron reductions were a function of initial total suspended solids concentration as well as overflow rate. Iron and nickel exhibited dependence on initial concentration of the specific metal for reductions, as well as dependence on overflow rate and initial total suspended solids concentration. The steady-state models selected from the results of this research for total suspended sol ids and each of the heavy metals are limited to the mixture, specific experimental conditions, and range of overflow rates observed in this research. Observed reductions of total suspended solids and heavy metals are considered to be 1 imited to physical sedimentation processes, in that processes that may effect reductions of these elements in a natural system are not factors in the results of this research.

Central to tapping mode atomic force microscopy is an oscillating cantilever whose tip interacts with a sample surface. The tip-surface interactions are strongly nonlinear, rapidly changing, and hysteretic. We explore numerically a lumped-mass model that includes attractive, adhesive, and repulsive contributions as well as the interaction of the capillary fluid layers that cover both tip and sample in the ambient conditions common in experiment. To accomplish this, we have developed and used numerical techniques specifically tailored for discontinuous, nonlinear, and hysteretic dynamical systems. In particular, we use forward-time simulation with event handling and the numerical pseudo-arclength continuation of periodic solutions. We first use these numerical approaches to explore the nonlinear dynamics of the cantilever. We find the coexistence of three steady state oscillating solutions: (i) periodic with low-amplitude, (ii) periodic with high-amplitude, and (iii) high-periodic or irregular behavior. Furthermore, the branches of periodic solutions are found to end precisely where the cantilever comes into grazing contact with event surfaces in state space corresponding to the onset of capillary interactions and the onset of repulsive forces associated with surface contact. Also, the branches of periodic solutions are found to be separated by windows of irregular dynamics. These windows coexist with the periodic branches of solutions and exist beyond the termination of the periodic solution. We also explore the power dissipated through the interaction of the capillary fluid layers. The source of this dissipation is the hysteresis in the conservative capillary force interaction. We relate the power dissipation with the fraction of oscillations that break the fluid meniscus. Using forward-time simulation with event handling, this is done exactly and we explore the dissipated power over a range of experimentally relevant conditions. It is found that the dissipated power as a function of the equilibrium cantilever-surface separation has a characteristic shape that we directly relate to the cantilever dynamics. We also find that despite the highly irregular cantilever dynamics, the fraction of oscillations breaking the meniscus behaves in a fairly simple manner. We have also performed a large number of forward-time simulations over a wide range of initial conditions to approximate the basins of attraction of steady oscillating solutions. Overall, the simulations show a complex pattern of high and low amplitude periodic solutions over the range of initial conditions explored. We find that for large equilibrium separations, the basin of attraction is dominated by the low-amplitude periodic solution and for the small equilibrium separations by the high-amplitude periodic solution. / Ph. D.

Three rain events were sampled from a storm drain at Manassas Mall in Manassas, Virginia. The urban runoff samples obtained were placed into lab-scale Plexiglas~ settling columns to monitor removal of total hydrocarbons (THC) by extended quiescent settling. Samples were collected from the columns at specific depths and times over the 48-hour settling period. The samples were analyzed for total hydrocarbon content on a Horiba oil content analyzer. Hydrocarbon values were averaged at each column depth in order to construct average THC concentration and average THC percent removal profiles over settling time. Maximum average THC removals were 77.8%,32.5%, and 73.6%, respectively, for Storms #1, 2, and 3 after 48 hours of quiescent settling. These average removals corresponded to depths of -2 feet, -1 foot, and -3 feet in the 5-foot tall columns. According to traditional sedimentation theory, pollutants settle out of water to the bottom of the container of interest. This did not appear to be solely the case in this hydrocarbon sedimentation study. It appeared that sedimentation was not the sole removal mechanism at work. Some fractions of oil and grease seemed to reorganize into low-density sub-groups and float to upper regions of the column. Also, the majority of THe removal occurred within the first 18 hours of settling for two of the three storms sampled. / Master of Science

A Statistical formulation for estimating the average time of detention within a pond for a captured runoff volume is presented. It is assumed that mixing takes place during an event and that settling occurs over the period required to empty the captured volume or the time between successive events, whichever is smaller. This analytical detention time is used in conjunction with a pollutant settling efficiency-detention time curve to estimate the settling efficiency. This curve is generated from Storm Water Management Model (SWMM) simulations and shown to be independent of runoff statistics, pond configuration, and arbitrary but constant influent concentration under complete mixing. The analytical detention time estimate, in combination with the settling efficiency curve and an expression for the capture efficiency of the pond provides a valuable desktop method for the planning level design of detention basins for pollutant removal. The method performs quite well when compared to the results obtained from long-term SWMM simulation runs. / Master of Science

An investigation was undertaken to better understand the hydrogeologic framework of the Rio Cobre and Rio Minho-Milk river basins, Jamaica, West Indies. A quasi three-dimensional finite-difference groundwater flow model was used to conceptualize flow conditions and establish a hydrogeologic budget of the region. The Rio Cobre and Rio Minho-Milk river basins lie on the Clarendon Block, an area with a complex geologic history. The geologic history includes: 1) the intrusion of calc-alkaline granites, 2) morphotectonic sedimentation, 3) three episodes of deformation by transpressional and transcurrent tectonics, 4) the deposition of a highly permeable, Tertiary carbonate platform, and 5) the development of near surface karst oriented with the major NNW-SSE fault trend in the basins. Since deposition, compression, faulting, and solution have modified the distribution and thickness of carbonate rocks impacting the ground-water flow of the region. The most notable features are the older NNW-SSE trend dip-slip faults and the younger E-W trend strike-slip faults, notably the South Coast Fault (SCF) formed during the Laramide Orogeny. The White Limestone aquifer is the principal aquifer of the Rio Cobre and Rio Minho-Milk river basins in the parishes of St. Catherine, Clarendon, and partly in Manchester. It is characterized by intercalated sequences of permeable rubbly and micritic carbonate rocks. The age of the rocks range from Late Cretaceous (Maastrichtian) to Recent. The permeability of the South Coast fault and the high hydraulic conductivity value associated with the Tertiary carbonate platform (480 m/d) in the Lower Rio Minho-Milk River basin control the gradient of the potentiometric surface and ground water flow in that region The agreement between the measured and the simulated hydraulic heads obtained for this steady-state model suggests that the values assigned to the hydraulic properties that characterize the ground-water flow of the White Limestone aquifer are reasonable. Recharge to the area occurs as net recharge in addition to upland subsurface inflow across the general head boundary in the northern part of the study area. Comparisons of calculated and observed values of head indicate that simulated groundwater flow field generally agree with field conditions. Several simplifying assumptions were made for the conceptualization and simulation of flow in the basins: 1) during the 1998 water year, ground-water in the basins was considered at steady-state, 2) pumping does not significantly affect the level of hydraulic heads; therefore pumping wells are not simulated, 3) Net recharge from precipitation varies spatially, 4) karstification and aquifer heterogeneity impact on the distribution of hydraulic conductivity, 5) Darcy's law is applicable to flow through the fractures and solutions openings in a karst region, 6) flow in the White Limestone aquifer occurs in the uppermost 650 m and vertical flow is assumed to be controlled by intervening units, 7) evaporation was not explicitly simulated in the model. Recharge rates were considered as "net recharge," and 8) submarine discharge occurs from the aquifer along the coast where aquifers are hydraulically connected to the sea. Ground-water flow in the basins was conceptualized as a quasi three-dimensional flow system in which two model layers were used. The model boundaries selected to represent natural hydrologic boundaries include (1) a no-flow along the western and eastern boundaries, (2) a constant head boundary along the freshwater/saltwater interface; (3) a general head boundary along the northern boundary; and (4) a horizontal-flow barrier boundary along the South Coast Fault; and (5) river leakage boundaries along major rivers draining the coastal basins. The simulated region is an area of 2,550 square kilometers, two-thirds of which is hilly and the remainder, irrigated plains with small swamps draining the area. The model consists of over 337,500 cells and employed a regular grid spacing of 200m x 160m. The model was designed and calibrated to steady-state conditions from data observed/estimated during water year 1998. The Water Resources Authority of Jamaica (WRAJ) will use the results of the modeling study as a predictive tool for long-term management and monitoring of water resources in the region. The model was calibrated using a manual trial-and-error adjustment of parameters. Hydraulic conductivity values in both model layers, hydraulic conductivity at the general-head boundary, and streambed conductance were adjusted during successive simulations until computed head values approximated field conditions. The computed potentiometric surface is an adequate or reasonable match on a regional scale, with the general horizontal hydraulic gradient oriented with the main fault trend NNW-SSE in both basins. Sensitivity tests of the calibrated model were conducted on net recharge, hydraulic conductivity, hydraulic conductivity assigned along the general-head boundary, and streambed vertical conductance to determine if differences between simulated and observed values were similar to the range of uncertainty in the values of input data and boundary conditions. Based on the results obtained from the sensitivity analysis, it is apparent that the model is extremely sensitive to changes in horizontal hydraulic conductivity and recharge in the form of precipitation. The model is least sensitive to streambed vertical hydraulic conductivity. / Master of Science

<p dir="ltr">Impact cratering is the most pervasive geologic process to have shaped our Solar System. At the largest scales, impact basins provide a window into the primordial structure of the impacted body as the mechanics governing their formation and evolution are dependent on the planet's surface structure at the time the basin was formed and for several tens of millions of years thereafter. This dissertation focuses on Mercury's Caloris basin, its largest best-preserved impact basin, to aide in characterizing the internal and surgical structure of a young Mercury.</p><p dir="ltr">Mercury has been visited by two spacecraft over the past several decades, providing us with a wealth of information about its surface morphology, its unique internal structure, and chemical makeup. Views of Caloris basin show that it preserves evidence of Mercury's early volcanic history both within its interior and in an annulus surrounding the basin, though they mask our ability to determine whether Caloris formed as a culturing basin. The plains units within the basin record the evolution of the regional stress field and its interplay with Mercury's persistent global contraction in the form of brittle deformation features and linear long-wavelength topographic undulations. </p><p dir="ltr">This dissertation attempts to unravel the sequence of events that led to Caloris basin's present-day configuration to aide in characterizing Mercury's thermomechanical structure and how it has evolved over geologic time. Impact simulations are used to reproduce Caloris basin's crustal structure which is indicative of Mercury's thermal state at the time of its formation. Results from these models are used as initial conditions in subsequent finite element models that explore how the basin evolved over geologic time. Here, it will be shown that Mercury's thermal structure and the large impact velocities experienced on the planet inhibit its formation as a multiring basin. Further, Mercury's thin silicate shell causes Caloris to undergo a unique postimpact evolution compared to other large impact basins, potentially resulting in its formation as a mascon basin without the need for the emplacement of its interior volcanic plains.</p>

Mass transport deposits form a significant portion of the rock record in both modern and ancient basins. Their geometry, composition, distribution and genesis are poorly understood, making it difficult to predict anything about these deposits in assessing subsurface basin stratigraphy or modern seafloor hazards. A tremendous effort has been made in the last few years to characterize and better understand seafloor failures in numerous margins of the world. These mass failures have triggered the interests of geologists, particularly in the oil and gas industry, as they can form prominent seals and reservoirs. To increase our knowledge base of mass transport complexes (MTCs), the characteristics of 259 siliciclastic deposits worldwide, were analyzed in terms of their volume, area, length, thickness, lithology, and tectonic settings. In some instances, MTCs were geo-referenced and digitized into ArcGIS and their dimensions were calculated. These data reveal several interesting points and suggest a number of statistically significant predictive relationships. Sand-rich mass transport deposits show a propensity to be short and thick. Muddy MTCs show a propensity to be longer and thinner. The highest number and largest volume of clastic mass transport deposits occur along passive margins. These mega-MTCs are typically muddy with lengths up to 800 km and volumes up to 5000 km3. Sandy and gravelly Quaternary-age MTCs show maximum lengths of less than 300 km and with volumes less than 2000 km3. Pre-Quaternary MTCs are systematically under-documented in literature, but known occurrences are found in passive, active and convergent margins. The largest (30,000 to 40,000 sq km) occur along the older Tertiary margin of West Africa. To date, 41 separate mass transport deposits composed dominantly of carbonate material have been identified in literature. The most extensive and voluminous (7000 km3) carbonate mass transport complexes occur in the Citronens Fjord, Offshore Greenland. They are 200m thick, Silurian-age mega-breccias that were deposited in a convergent margin setting. On comparison carbonate MTCs tend to show longer flows with coarser grain sizes, while clastics show coarser grained deposits to be of more limited length. The Mad Dog area, Gulf of Mexico is a region of active salt tectonics and mass transport processes. Consequently, it was selected to form a focus study area to test the relationships developed during this project. MTCs in this region were grouped into four main types based on their size, geomorphology and internal structure. Their geometries indicate they are comparable to MTCs found offshore Oregon and New Jersey and are most likely muddy in nature. / text

Three aquifers of diverse lithology and hydraulic character form the ground-water reservoir in the Roswell basin. The main aquifer, the carbonate aquifer, is developed in carbonate rocks of Permian age. It is the source of about two-thirds of the ground water pumped in the basin and receives more than 90 percent of the recharge to the basin. The second most important aquifer is the shallow aquifer which lies near the Pecos River in beds of sand and gravel of both Permian and Holocene age. About one-third of the ground water pumped in the basin comes from the shallow aquifer. Prior to pumping, the main source of recharge to the shallow aquifer was probably ground water leaking upward from the carbonate aquifer. Since pumping began, the main source of recharge to the shallow aquifer is probably return flow of irrigation water pumped from the carbonate aquifer. Natural discharge of ground water from the shallow aquifer into the Pecos River causes a gain in th.e base flow of the Pecos River in the Roswell basin. The third aquifer, the shallow-artesian aquifer, is in red beds and evaporite beds of Permian age. This aquifer overlies the carbonate aquifer and underlies the shallow aquifer. The shallow-artesian aquifer acts as a minor aquifer and also as a semi-permeable unit which partly confines ground water in the carbonate aquifer. Vertical permeability of the shallow-artesian aquifer is variable and depends on the lithology and thickness of the aquifer. Hydraulic head in the shallow-artesian aquifer also varies quite widely depending on the depth to which a well penetrates the aquifer. All ground-water aquifers in the basin transect formational boundaries and are therefore not closely related to the named geologic formations. A flow net analysis of the carbonate aquifer and of the shallow aquifer imply that geologic structure is important in the movement of ground water in the basin by limiting the transmissivity of the shallow and carbonate aquifers, by forming the present pattern of surface water drainage, and possibly by the contamination of fresh ground water by highly saline ground water. The flow net analysis also shows areas of recharge to the shallow and carbonate aquifers, and areas where the carbonate aquifer looses water to the shallow-artesian aquifer and to the shallow aquifer.