Sustainable Built Environments Senior Capstone Project / This paper examines Subsurface Drip Irrigation(SDI) as a solution to water conservation in landscape irrigation. This is a problem because of the drought that the southwestern United States is experiencing, and the amount of water that landscapes utilize and which is ultimately wasted due to inefficient practices. Subsurface drip irrigation represents a potential solution due to its high efficiency and water saving ability; however, there are some problems within it as a system. Utilizing a multiple case studies approach, this paper looked at three of the top irrigation companies, Rain Bird, Toro, and Netafim, and examined how they innovated to overcome the problems with SDI. Synthesizing the best and most effective practices from each company, a model for improving SDI was generated.

Large optical systems fabrication is a demanding task due to the tight requirements and big scales. To make mirrors up to 8.4m in diameter necessitates technological development in materials, tooling, and metrology. These advancements are designed to not only produce optics on a near-unheard of scale, but to improve fabrication methods with each piece.For an optical surface to be properly polished, the amount of material removed during polishing must be greater than the volume of damage left behind by the grinding process. Mixed-mode grinding, which combines bound abrasives with a compliant binder material, is a valuable tool at this stage as it creates less damage while maintaining a fast and uniform cutting rate than traditional loose abrasive grinding.These materials are challenging for large optical surfaces due to the honeycomb structures used to lightweight the mirrors. Development is done to adapt the abrasive to handle the very low pressures and speeds required to avoid imprinting structure on the optical surface.We take a comprehensive approach in measuring mixed-mode behavior using 3M Trizact™. Prior works on bound abrasives have focused on specific properties: removal rates, subsurface damage, etc. None have yet to look at the entire scope of the material and its benefits. These properties will be analyzed along with different behaviors regarding surface scattering, Twyman effect bending moments, glazing, manufacturing expenses, and failure mechanisms. This comprehensive understanding of the abrasive allows manufacturers to create better grinding schedules and reduce overall expenses in fabrication.Trizact shows up to a three times faster removal rate while producing 30\% less subsurface damage than loose abrasives of similar size. Additionally, the surface has scatters less light which can be adapted through changes in processing to create a specular reflection for optical surface metrology.Based on our findings, this type of abrasive integrates into current optical fabrication processes as a pre-polishing material. Here, the transition to these abrasives becomes cost effective by rapidly eliminating damage created during the generating of the surface and reducing the amount of polishing required.

The addition of lead to the copper alloys increase the machinability of thework material (without reference here to environmental factors) and reduces the overall production cost of the components at different stages, despite copper being expensive, which makes a challenging task to replace lead. Since lead is dangerous to human health. Many materials are considered to replace lead in brass and silicon is one of the alternative. This thesis characterizes the lead and the lead free brass's surfacemetallurgy for a certain cutting data. The study includes identification of alteredmaterial zones (AMZ) defined by the plastic deformation, hardness alterationsand grain distributions.The study results include the analysis of deformed subsurface region andcomparison exemplifying differences between the two materials under twodifferent studies. / Lead free brass

The wide use and the incomplete metabolism of antibiotics, along with the poor removal efficiency of current treatment systems, results in the introduction of large quantities of antibiotics to the environment through the discharge of treated and untreated wastewater. If not treated or attenuated near the source of discharge, the antibiotics can be distributed widely in the environment. In this research, sulfamethoxazole (SMX), a common sulfonamide antibiotic, was selected as a model compound due to its presence in the environment and its resistance to remediation and natural attenuation. Among the various entry routes, discharges from on-site disposal systems are of particular interest due to the wide use of these systems. The complex nature of subsurface transport downstream of these systems adds difficulties to the removal of SMX from subsurface discharges. For this research, two processes that impact SMX removal, biodegradation and sorption, were examined to determine the primary factors governing the elimination of SMX from septic effluent discharges in the subsurface. To characterize the biodegradation of SMX, batch experiments were conducted with SMX in the presence of septic effluent and soil for both aerobic and anoxic conditions. Results showed that SMX removal was limited in the septic effluent but increased in the presence of soil, demonstrating the important role of the soil in SMX removal in both aerobic and anoxic conditions. Addition of external nutrients (ammonium and sulfate) had small effects on SMX removal, although SMX removal was enhanced under aerobic condition with increased dissolved organic carbon. To overcome the limited sorption of SMX on soil, soil amendments were developed and evaluated using biochar, a green and cost-effective adsorbent. Biochars produced from different types of feedstock were characterized for different pyrolysis temperatures, and their adsorption behaviors were examined and compared with commercial biochar and activated carbon (AC). Adsorption isotherms were developed and adsorption kinetics of soil, biochar and AC were studied. Results showed that adsorption on soil, biochar and AC followed three different kinetics models and their equilibrium isotherms followed the Freunlich model. Higher adsorption rates were achieved with biochars prepared at the higher temperature. A lab-engineered biochar with pine sawdust at 500 °C achieved comparable sorption capacity to AC. SMX transport in subsurface was also explored with saturated soil columns filled with soil that was mixed with biochar at different percentages. Significant SMX removal (including complete elimination at a low flowrate and over 90 % elimination at a high flowrate) for all cases was primarily attributed to biodegradation. These results provide insight into the transport and transformations affecting SMX, and then provide a basis for developing low-cost approaches for the mitigation of SMX.

Globally, human activities are altering nutrient biogeochemical cycles. The impact of humans on silicon (Si) cycles remains largely unexplored. Understanding the cycle of Si is important because weathering of siliceous rocks is a substantial sink of atmospheric carbon. Additionally, Si is required by diatoms. Diatoms form the base of important socioeconomic food webs, responsible for ~50% of oceanic net primary production, and deliver atmospheric carbon to ocean sediments as part of the ocean’s biological pump. My dissertation aims to assess the role of anthropogenic activities in altering Si cycling across the land-ocean continuum. Chapter 2 focuses on how assimilation of biogenic silica (BSi) by trees may be impacted by projected changes in climate. Using samples collected during a multi-year, snow removal experiment, I show that increased frequency and duration of soil freezing in winter significantly decreased (-28%) BSi in sugar maple (Acer saccharum) fine roots compared to control plots. Importantly, I observed that fine roots are a previously undescribed pool of BSi within sugar maples, accounting for 29% of total sugar maple BSi while only 4% of sugar maple biomass. Chapter 3 examines the origin and fate of Si within wastewater for the City of Boston. I determined the total dissolved silica (DSi) load in wastewater influent (69,500 kmol DSi year-1), then parsed the total DSi flux between Si contributions of sewage (49%), groundwater infiltration (39%), and surface runoff inflow (12%). In Chapter 4, I study the DSi load carried by treated effluent. I determined that effluent load (67,800 kmol DSi year-1) is not statistically different from influent load, indicating that wastewater treatment does not remove DSi. In Chapter 5 I demonstrate how humans impact concentrations of DSi in urban groundwater. Groundwater DSi increases with human presence and urban areas have significantly higher concentrations of DSi compared to groundwater conditions along the Massachusetts coast. I demonstrate that historic variables defining fill techniques, fill material, and pre-fill land-use out preform geologic variables in predicting urban groundwater DSi concentrations. This dissertation highlights human alterations to biological assimilation, fate, and effects of Si in sewage, and centuries-long subsurface Si impacts that perturb the distribution and availability of a nutrient intimately tied to water quality and climate.

<p>Controlled drainage is a management strategy designed to mitigate water quality issues caused by subsurface drainage. To improve controlled drainage system management and better understand its hydrological and environmental effects, this study analyzed water table recession rate, as well as drain flow, nitrate and phosphorus loads of both free and controlled drainage systems, and simulated the hydrology of a free drainage system to evaluate surface runoff and ponding at the Davis Purdue Agricultural Center located in Eastern Indiana. </p> <p>Statistical analyses, including paired watershed approach and paired t-test, indicated that controlled drainage had a statistically significant effect (<i>p</i>-value <0.01) on the rate of water table fall and reduced the water table recession rate by 29% to 62%. The slower recession rate caused by controlled drainage can have negative impacts on crop growth and trafficability by causing the water table to remain at a detrimental level for longer. This finding can be used by farmers and other decision-makers to improve the management of controlled drainage systems by actively managing the system during storm events. </p> <p>A method was developed to estimate drain flow during missing periods using the Hooghoudt equation and continuous water table observations. Estimated drain flow was combined with nutrient concentrations to show that controlled drainage decreased annual nitrate loads significantly (p<0.05) by 25% and 39% in two paired plots, while annual soluble reactive phosphorus (SRP) and total phosphorus (TP) loads were not significantly different. These results underscore the potential of controlled drainage to reduce nitrate losses from drained landscapes with the higher level of outlet control during the non-growing season (winter) providing about 70% of annual water quality benefits and the lower level used during the growing season (summer) providing about 30%. </p> <p>Three different methods including monitored water table depth, a digital photo time series and the DRAINMOD model simulations were used to determine the generation process of surface ponding and runoff and the frequency of incidence. The estimated annual water balance indicated that only 7% of annual precipitation contributed to surface runoff. Results from both simulations and observations indicated that all of the ponding events were generated as a result of saturation excess process rather than infiltration excess.</p> <p>Overall, nitrate transport through controlled drainage was lower than free drainage, indicating the drainage water quality benefits of controlled drainage, but water table remained at a higher level for longer when drainage was controlled. This can have negative impacts on crop yields, when water table is above a detrimental level, and can also increase the potential of nutrient transport through surface runoff since the saturation excess was the main reason for generating runoff at this field.</p>

<div>The atomic force microscope (AFM), traditionally known as a nanoscale instrument for surface topography imaging and compositional contrast, has a unique ability to investigate buried, subsurface objects in non-destructive ways with very low energy. The underlying principle is the detection of interactions between the AFM probe and the sample subsurface in the presence of an external wave or eld. The AFM is a newcomer to the field of subsurface imaging, in comparison to other available highresolution techniques like transmission or scanning electron microscopy. Nevertheless,</div><div>AFM offers signicant advantages for subsurface imaging, such as the operation over a wide range of environments, a broad material compatibility, and the ability to investigate</div><div>local material properties. These make the AFM an essential subsurface characterization tool for materials/devices that cannot be studied otherwise. </div><div><br></div><div><div>This thesis develops a comprehensive qualitative and quantitative framework underpinning the subsurface imaging capability of the AFM. We focus on the detection of either electrostatic force interactions or local mechanical properties, using 2nd-harmonic Kelvin probe force microscopy (KPFM) and contact-resonance AFM (CRAFM),</div><div>respectively. In 2nd-harmonic KPFM we exploit resonance-enhanced detection to boost the subsurface contrast with higher force sensitivity. In CR-AFM we use the dual AC resonance tracking (DART) technique, in which the excitation frequencies are near one of the contact resonance frequencies. Both techniques take advantage of the maximized response of the cantilever at resonance which improves the signal to noise ratio. These enable high-resolution subsurface mapping on a variety of polymer</div><div>composites.</div></div><div><br></div><div><div>A relevant challenge is the ability to reconstruct the properties of the subsurface objects from the experimental observables. We propose a method based on surrogate</div><div>modelling that relies on computer experiments using nite element models. The latter are valuable due to the lack of analytical solutions that satisfy the complexity of the geometry of the probe-sample system and sample heterogeneity. We believe this work is of notable interest because offers one of few approaches for the non-destructive characterization of buried features with sub-micron dimensions.</div></div>

Signaling and sensing with rotating magnet sources have both Terrestrial and Extraterrestrial applications. The dual spinning magnet unit presented in this paper is a simple, lightweight solution to help understand soil densities and locate water and ice pockets, for example, on Mars. Traditional magnetic telemetry systems that use energy-inefficient large induction coils and antennas as sources and receivers are not practical for extraterrestrial and remote field sensing applications. The recent proliferation of strong rare-earth permanent magnets and high-sensitivity magnetometers enables alternative magnetic telemetry system concepts with significantly more compact formats and lower energy consumption. There are also terrestrial applications, for example, subterranean objects such as underground infrastructure and unexploded ordnances (UXO) that are often unmapped and difficult to find on Earth. Current ground penetrating radar units are expensive, large, and heavy. The research presented explores the viability and possibility to develop a unit that will induce an oscillating magnetic field with controllable shape to reliably locate buried ferromagnetic and non-ferromagnetic objects while remaining lightweight and cost effective. A Dual Rotating Magnet (DRM) design is presented. Experiments and numerical simulations assess the system for terrestrial and extraterrestrial detection of: 1) differences in soil densities, 2) water and ice pockets at shallow depths in the subsurface, and 3) subterranean ferromagnetic and non-ferromagnetic objects of interest.

This research characterizes the nature of fractures in Paleozoic and Mesozoic caprock seal analogs exposed in central and south-eastern Utah. The results of this research show evidence for fluid flow and mineralization in the subsurface as well as reactivation of fractures suggesting that the fractures act as a loci for fluid flow through time. The heterolithic nature of the caprock seals and meso-scale (cm to m) variability in fracture distributions and morphology highlight the strong link between the variation in material properties and the response to changing stress conditions. The variable connectivity of fractures and the changes in fracture density at the meso-scale plays a critical role in subsurface fluid flow. The presence or formation of new fractures can result in seal bypass systems, which can cause failure of hydrocarbon traps, CO2 geosequestration sites, waste and subsurface fluid repositories. An integrated approach of field, borehole geophysical, burial and stress history modeling, rock strength testing, and numerical modeling are used to understand the effects changing material properties, rock strength, and stress history have on sealing capacity. Simplified stress history models derived from burial history curves are combined with laboratory derived rock properties to understand the importance variations in rock properties and differential and effective mean stress have on the mechanical failure of fine-grained clastic sedimentary rocks. Burial history and rock strength data show that in units that experience similar burial depths and changing mechanical property exert a control on deformation type. Geomechanical models reveal changes in local strain magnitudes at locked mechanical interfaces, suggesting that elastic mismatch between layers results in differential strain distribution. Characterization of fracture patterns, rock strength variability and the modeled changes in subsurface strain distribution is especially important for understanding the response of low-­‐permeability rocks to changing stress in the subsurface, and is applicable to multiple geo-engineering scenarios such as exploitation of natural resources, waste disposal, and management of fluids in the subsurface. The analyses presented in this dissertation provide analog fracture data for fine-grained clastic rocks and a dataset for better understanding the importance of heterogeneity in low permeability rocks.

Cette étude s'inscrit dans le cadre de la modélisation distribuée à base physique des interactions entre processus de surface et de subsurface. Une nouvelle approche de modélisation, dite darcéenne multidomaine , est présentée. Les équations de Richards et de l'onde diffusive sont respectivement utilisées pour décrire le processus d'infiltration et de ruissellement. L'équation de l'onde diffusive est transformée en une équation de diffusion non linéaire similaire à l'équation de Richards. L'écoulement d'eau à la surface du sol est alors assimilé à un écoulement dans un milieu poreux aux propriétés particulières. Une couche de milieu poreux, appelée couche de ruissellement, est introduite dans le domaine de calcul. L'ensemble de la dynamique surface/subsurface est alors décrite dans un continuum darcéen par une seule équation de Darcy non linéaire avec des paramètres domaine-dépendants. Cela permet notamment d'imposer une continuité hydraulique entre l'eau de surface et l'eau de subsurface. Un modèle de transport permettant de s'attaquer à la problématique de la séparation d'hydrogramme est également implémenté. Le modèle développé est évalué à partir de cas tests classique de la littérature. Une analyse de sensibilité ainsi qu'une étude détaillée du ruissellement hortonien sont ensuite présentée. Enfin, l'expérience réalisée par l'IRD sur la parcelle de Thies au Sénégal est reproduite. Les résultats sont encourageants et laisse penser que l'approche de modélisation développée permet de reproduire correctement à petite échelle la dynamique fortement couplée des systèmes hydrologiques de type parcelle ou versants.