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Impact spherules are sand-sized spherical particles that have been interpreted to have formed by the cooling, crystallization, and quenching of melt droplets condensed from vapor plumes that are created during large meteor impacts. Spherules may be deposited globally as unique marker beds, such as at the K-Pg boundary. A minimum of 11 spherule beds have been identified in the Archean and Paleoproterozoic, and provide a record of impact events that predate any known craters. This study of 3.24 Ga impact spherules from the S3 spherule layer in the Barberton Greenstone Belt (BGB) in the Kaapvaal Craton of South Africa focuses on the heterogeneity of textures and geochemistry produced during the cooling and crystallization of spherules within a vapor plume. Type 4b spherules are layered phyllosilicate spherules with discrete differences in texture and composition between the inner and outer layer, even after alteration. Compositionally layered phyllosilicate spherules were analyzed using Energy Dispersive X-ray Spectroscopy (EDS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to measure major, trace, and rare earth element (REE) concentrations. Backscatter Electron (BSE) images and elemental X-ray maps indicate a range of compositional differences between the inner and outer layers of type 4b spherules. The majority of REE plots have nearly flat patterns, with little to no light to heavy REE fractionation; however, the outer layers consistently have higher concentrations, averaging about 10x chondritic, whereas the interiors are at or below chondritic levels with a mid-REE enrichment. The trace and REE patterns of the type 4b spherules are consistent with a more mafic inner layer and a more intermediate outer layer. Mechanisms to produce this layered texture may include: (1) accretion of less mafic material from the plume onto existing melt droplets as the plume continues to fractionate, (2) collision of melt droplets of different viscosities, (3) by differentiation within the melt droplet prior to crystallization, or (4) by diagenetic effects. Based on textures, such as distinct boundaries between layers, and compositional patterns, such as an enrichment of Ti and REE in the outer layer, the data best fits the particle collision formation mechanism hypothesis, which has important implications for impact plume studies, such as plume density, turbulence, temperature, and opacity. / Geology

Anthropic impacts adversely affect the productivity, integrity, connectivity, and resilience of riverine ecosystems, with widespread cumulative effects on the biota and biodiversity. The natural flow regime is a fundamental driver of physical and chemical processes, determining the morphological profile of the river systems and sustaining the complex network of ecological interactions and biological patterns. Therefore, in order to reach the environmental goals required by the binding legislation, and achieve a sustainable use of water resources, it is urgent to understand the mechanisms behind changes in the structure of biological communities along gradients of human disturbances which affect the flow regime. Indicators based on macroinvertebrates are widely used to assess the ecological status of water bodies, given their sensitivity/tolerance to pollution. However, in Alpine running waters, where chemical quality is less impacted than in lowland rivers, it is particularly important and valuable to detect the hydro-morphological alterations, and to discriminate them from chemical degradation, based on the responses of benthic macroinvertebrates to such multiple stressors. Therefore, this thesis aims at: i) examining the taxonomic and functional responses of macroinvertebrate communities to the different anthropogenic pressures acting on river systems; ii) evaluating the taxa/functional traits which mostly discriminate between hydrological and morphological alterations, and chemical degradation, to support effective bioindication methods. Focus of the research is to assess the macroinvertebrate community responses to the alterations caused by flow regulation and morphological alterations, which include water abstraction, diversion, stocking and the intermittent release of water from hydropower plants, banks artificialization and construction of weirs, dams, and other structures, each of these with environmental consequences of different scale and magnitude, such as the interruption of the longitudinal continuity, residual flow release and hydropeaking. The first part of this thesis is based on two empirical field studies, following respectively a manipulative and a mensurative approach, and focuses on changes in the taxonomic and functional composition due to river regulation and hydrological alterations. The first study, conducted in a set of seminatural streamside experimental flumes, simulates a residual flow stretch by reducing the discharge of the downstream sections (treatment) to 50% of the discharge of the upstream sections (control). Even within the short-term of our experiment (i.e., 3 weeks from the beginning of the simulation), we successfully simulated a small run-of-the river water abstraction and we recorded substantial changes in the EPT (Ephemeroptera, Plecoptera and Trichoptera) benthic assemblages. In fact, we observed shifts in functional (rather than taxonomic) EPT community composition over time, likely due to the active drift, from a typically rheophile to a more limnophile one as a response to the stress imposed by the flow reduction, related to decrease of flow. In the second study, we investigated the effectiveness of a hydropeaking mitigation measure on flow and biotic components, in a case study of hydropeaking reduction on a 10-km reach of the Noce Stream, a unique approach for Alpine streams to date. The hydrological analysis conducted applying two hydropeaking quantification indices (HP1 and HP2 of Carolli et al., 2015, and the COSH method by Sauterleute & Charmasson. 2014) confirmed a partial mitigation of the hydropeaking in the stretch. As a consequence of the change in hydrological regime, we observed a different taxonomic and functional recovery in the benthic and hyporheic communities. In fact, macrobenthos was negatively affected by the reduced dilution of point and diffuse pollution; conversely, the hyporheic communities showed an increase in diversity and abundance of interstitial taxa, especially those exclusive to the hyporheic zone, likely due to changes in the interstitial space availability, brought by a reduction of clogging caused by fine sediments which were previously released with each hydropeaking wave. The second part of the thesis is based on large dataset analysis where expert knowledge has been integrated with machine learning and data-based approaches: the focus of thesis shifts towards a holistic approach, extending the investigation to the entire watershed of the Trentino Province by including macroinvertebrate field data collected between 2009 and 2019 from 160 sampling sites, distributed over 90 rivers and streams. Based on the expertise of field operators from the local Environment Agency (APPA), and the quality indices currently used according to the Water Framework Directive (WFD), all the APPA stream sites were classified according to the presence of known hydrological, morphological, and chemical alterations, including the co-occurrence of two or more alteration types; sites in pristine conditions were also identified. Seasonality, stream order and type, and other stream characteristics associated with the elevation gradient are important in flow-ecology investigation, and for this reason were included in the analysis. Moreover, these features are proxies for other variables which are closely related with the structure of the benthic community, such as current velocity, organic matter availability and substrate composition, and can also be related to the probability of expecting the presences of small hydropower plants and/or a diffuse or localized pollution sources. This second section of the thesis is divided into two parts: the first part describes the initial overall qualitative and quantitative analysis, which was conducted to determine to which extent a functional diversity-based approach better recognizes patterns in the benthic community compared to the WFD diversity indices. The second part describes the machine learning approach which we used to examine the degree to which a-priori expert classification matched data-driven classification based on the taxonomic and functional composition of benthic macroinvertebrates across different binary classification disturbances. A Random Forest analysis was performed independently on benthic-macroinvertebrate abundance (expressed as number of individuals per m2) and their functional compositions. The majority of stream sites were a-priori classified as impacted by either one or a combination of anthropogenic alterations (80%), with only 16% of sites in reference or pristine conditions. We observed high variability in benthic community assemblages, likely due to complex environmental interactions and caused by the cumulative/synergic effect of different alterations that negatively affect the discrimination between stressor-specific responses. The overall results of these large-dataset based analyses showed relevant outcomes, the main one being the good discrimination of unaltered sites from the altered ones, but a low discriminating power for the types of alteration (hydrological, morphological, pollution pf combination of two or three of them) based on taxonomic and functional composition of the benthic communities. The functional parameters directly related to the stream longitudinal preference, microhabitat preferences, flow velocity, hydrological and thermal regime, and food availability in the river network, well the most suitable to identify any type of river degradation. A further step in the detection of significant indicator taxa/traits was achieved with the machine learning approach, which resulted in robust and dependable predictive models, that identified the specific taxa and traits related to different stressors, thus representing a promising tool to support environmental assessment and water management. Overall, this thesis contributes to the identification of appropriate indicators based on macroinvertebrates taxonomic and functional sensitivity to different specific stressors, to use in the assessment of the Ecological Status of streams in mountain areas, with relevant outcomes for the water management of Alpine running waters, with particular regard to the definition of environmental flows, and to the mitigation of hydropeaking.

Traumatic brain injuries (TBIs) encompass an array of head trauma caused by diverse mechanisms, including falls, vehicular accidents, and sports-related incidents. These injuries vary from concussions to diffuse axonal injuries. TBIs are characterized by the linear and rotational accelerations of the head during an impact, which are influenced by various factors such as the velocity and location of the impact and the contact surface. Consequently, the accuracy of laboratory tests designed to evaluate protective technologies must closely mirror real-world conditions. This dissertation explores the boundary conditions essential for accurately replicating head impacts in laboratory settings. The research aims to improve the reconstruction of head impacts, concentrating on two main areas: 1) examining various aspects of friction during head impacts and 2) biomechanically characterizing the head impacts sustained by older adults during falls. This study provides insights into the overall influence of friction during head impacts. It investigates the friction coefficients between the helmet's shell and the impact surface, as well as between human heads, headforms, and helmets. Additionally, it assesses how these frictional interactions influence oblique impact kinematics. Defining static and dynamic friction coefficients of the human head and headforms is needed to develop more realistic head impact testing methods, define helmet-head boundary conditions for computer-aided simulations, and provide a framework for cross-comparative analysis between studies that use different headforms and headform alterations. This research also introduces and evaluates the accuracy of a model-based image mapping method to measure head impact speeds from single-view videos in un-calibrated environments. This measurement technique advances our comprehension of head impact kinematics derived from uncalibrated video data. By applying this method, videos of falls involving older adults were analyzed to determine head impact speeds and boundary conditions. The resulting data was used to construct headform impacts, capturing linear and rotational head impact kinematics. These reconstructions can inform the development of biomechanical testing protocols tailored to assess protective gear for older adults, with the goal of reducing fall-related head injuries. / Doctor of Philosophy / Traumatic brain injuries (TBIs) are head injuries that can happen in many ways, such as from falling, car accidents, or playing sports. These injuries can range from mild concussions to more severe cases, brain bleeds, or skull fractures. They happen when the head moves quickly or spins because of a hit, which can be affected by the speed of the impact, where on the head the impact happens, or what the head impacts against. Therefore, the accuracy of laboratory reconstruction head impact tests must closely mirror real-world conditions. This dissertation explores the boundary conditions essential for accurately replicating head impacts in laboratory settings. The research aims to improve the reconstruction of head impacts, concentrating on two main areas: 1) examining various aspects of friction during head impacts and 2) biomechanically characterizing the head impacts sustained by older adults during falls. This study provides insights into the overall influence of friction during head impacts. It investigates the friction coefficients between the helmet's shell and the impact surface, as well as between human heads, headforms, and helmets. Additionally, it assesses how these frictional interactions affect head impacts. Understanding how friction influences head impacts is crucial for improving helmet testing methods and allows for more consistent comparisons across various research studies that use different headform models or modifications. This research also introduces and evaluates a method to calculate head impact speeds by analyzing video footage, even if the video was not taken with special equipment or setup. This approach improves our understanding of head movements during accidents by using video clips of falls, particularly those involving older adults, to determine the head speeds and conditions of the impact. The information gathered from these analyses helps to reconstruct these impacts using a headform to measure injury metrics. These reconstructions are crucial for designing tests that can evaluate safety equipment meant to protect older adults from head injuries during falls.

Traditional trails near backcountry stream corridors are often designed with disregard to their potential ecological impact. Ecological and trail related literature show that riparian landscapes are sensitive to recreation impacts. This thesis examines concepts for designing trails in ecologically compatible ways near backcountry stream corridors. The synthesis of the literature regarding the biophysical processes of stream corridors and the effects of trails on the environment is used to help develop principles and guidelines for locating trails near backcountry stream corridors. In turn, these principles and guidelines assisted in the development of a trail assessment manual useful to scientists, planners, and designers. Seven trail impacts are assessed: excessive soil erosion, wet trails, water on trails, excessive trail widths, multiple trails, root exposure, and stream sedimentation. Three backcountry study sites from the Appalachian Ridge and Valley Province of Virginia are evaluated. A ranking and measurement procedure is developed to characterize environmental, use, design/siting, construction, and maintenance factors because each of these influence the degree of impacts along studied trails. Results show that many steep trail segments, especially those without proper drainage features have incised or eroded trail treads. Likewise, many trail segments without drainage features located along flat adjacent landforms have wet soil and water on trail impacts. Overall results show that as use amount or type increase there is a parallel in trail and environmental degradation. Finally, a stream crossing and trail drainage concept is developed illustrating ways to reduce sediment inputs into nearby streams. / Master of Landscape Architecture

With a rise in wearable sensor technology and the desire to investigate head impacts in previously unstudied groups, wearable head impact sensors have reached nation-wide popularity for their promising benefits to consumers and researchers. However, there are risks in relying on such technology before proper validation of its performance has been completed. Preliminary tests have found that current sensors vary widely in performance. The objective of this work was to develop and implement a test method for evaluation of wearable sensors in an ideal laboratory environment. A custom pendulum was used to impact a NOCSAE headform mounted on a Hybrid III neck. Sensors were tested under helmeted and unhelmeted conditions, according to their prescribed use. The headform was impacted at four locations, each at four impact energies ranging from 25 g to 100 g. Peak and time series headform kinematics output by each sensor were compared to accelerometers and angular rate sensors inside the headform. Average and standard deviations of peak sensor error and normalized RMS error were evaluated at each test condition to describe sensor performance. Requirements were set in the slope and coefficient of determination from linear regressions constrained through the origin to describe adequate sensor performance under ideal conditions. Sensors that met the requirement in at least one kinematic variable will be further evaluated in more realistic on-field and cadaver tests. The combination of all testing phases will be used to provide an overall sensor evaluation for both researchers and consumers. / Master of Science

Drought is one of the most severe natural disasters and detrimentally impacts water resources, agricultural production, the environment, and the economy. Climate change is expected to influence the frequency and severity of extreme droughts. This dissertation evaluates drought conditions using a variety of hydrologic modeling approaches include short-term drought forecasting, long-term drought projection, and a coupled surface-groundwater dynamic drought assessment. The economic impacts of drought are also explored through a linked economic impact model. Study results highlight the need for various drought assessment approaches and provide insights into the array of tools and techniques that can be employed to generate decision-support tools for drought mitigation plans and water resource allocation. For short-term drought forecasting, the Soil and Water Assessment Tool (SWAT) and Variable Infiltration Capacity (VIC) models are used with a meteorological forecasting dataset. Results indicate that eight weeks of lead-time drought forecasting show good drought predictability for the Contiguous United States (CONUS). For the drought projection at a finer scale, both SWAT and VIC models are applied with Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model outputs to derive multiple drought indices for the Chesapeake Bay watershed and five river basins in Virginia. The results indicate that current climate change projections will lead to increased drought in the entire Chesapeake Bay watershed and Virginia river basins because of increases in the sum of evapotranspiration, and surface and groundwater discharge. The impacts of climate change on future agricultural droughts and associated economy-wide implications are then evaluated using the VIC and IMPLAN (IMpact analysis for PLANning) model for the several congressional districts in Virginia. The result indicated that increases in agricultural drought in the future would lead to decreases in agricultural productions and job losses. Finally, a coupled framework using the VIC and MODFLOW models is implemented for the Chesapeake Bay and the Northern Atlantic Coastal Plain aquifer system, and the results of a drought index that incorporates groundwater conditions performs better for some drought periods. Hydrologic modeling framework with multiple hydrologic models and various scales can provide a better understanding of drought assessments because the comparisons and contrasts of diverse methods are available. / PHD / Drought is one of the most severe natural hazards and negatively impacts the water resources, agricultural production, the environment, and the economy. Climate change influences the frequency and severity of extreme droughts. This dissertation assesses drought conditions using various hydrologic-modeling methods, which are drought forecasting, climate change impacts on drought, economic influences of droughts, and a coupled model approach. Study results highlight the need for various drought evaluation techniques that can generate decision-support tools for drought mitigation plans and water resource management. For short-term drought forecasting, two hydrologic models are used with a meteorological forecasting dataset. Results indicate that eight weeks of lead-time drought forecasting show good drought predictability for the Contiguous United States (CONUS). For the drought projection at a finer scale, two models are also used with multiple climate models for the Chesapeake Bay (CB) watershed and five river basins in Virginia. The results indicate that current climate change projections will lead to increased drought in the entire CB watershed and Virginia river basins. The impacts of climate change on future agricultural droughts and associated economy-wide implications are then evaluated using the hydrologic and economic models for the several congressional districts in Virginia. The results indicate that increases in agricultural drought in the future would lead to decreases in agricultural productions and job losses. Finally, a coupled model is implemented for the CB and the Northern Atlantic Coastal Plain (NACP) aquifer system, and the results of a drought index that incorporate groundwater conditions performs better for some drought periods. Hydrologic modeling framework with multiple hydrologic models and various scales can provide a better understanding of drought assessments because the comparisons and contrasts of diverse methods are available.

As an applied approach to recreation management, adaptive management allows researchers and protected area managers to cooperatively improve management policies, and achieve the dual mandate to protect natural resources and provide high-quality recreational experiences. Through an evaluation of the efficacy of campsite and campfire management policies, this research provides land managers with an empirical assessment to aid in the adaptation and improvement of their visitor management strategies. Results from the Shenandoah National Park camping management study suggest that an established camping visitor containment strategy succeeded in reducing the areal extent of camping impacts while minimizing restrictions on visitor campsite selection options. Findings from the campfire research in seven protected areas indicate that current campfire policies have been largely ineffectual at reducing resource damage, and may exact a heavy toll in visitor experiences via campfire restrictions. The incorporation of resource and social research in this research offers a holistic approach to the evaluation of management objectives and affords protected area managers a more balanced perspective on the assessment of their policies. The conclusions reached by this integrated research will provide land managers with germane and timely information that will allow them to adapt their policies to better achieve their recreation management objectives. / Master of Science