Quantifying stream phosphorus dynamics and total suspended sediment export in forested watersheds in Vermont

Globally the quantity of reactive phosphorus (P) in soils, streams and groundwater has greatly increased throughout the 20th and early 21st centuries. This phenomenon is problematic in Vermont, evidenced by the repeated cyanobacteria blooms in shallow bays in Lake Champlain. While many studies have focused on P dynamics in agricultural watersheds, there is limited information on P dynamics in forested watersheds. Current remediation plans under the Lake Champlain total maximum daily loads (TMDL) call for substantial reductions in P loadings from forested areas of the basin. However, the lack of information and knowledge regarding forest P dynamics limits management and remediation plans. This study was conducted in three small forested watersheds, ranging in size from 2.5 to 8.3 square kilometers that have been managed under varying practices, including logging and maple sugaring. All three watersheds drain into Missisquoi Bay, a shallow bay in Lake Champlain that consistently has seasonal algal blooms. Streams in the forested watersheds were instrumented with turbidity sensors and pressure transducers to measure stage. A rating curve was developed during field visits to relate stage to discharge. Water samples were collected from May through November 2017 using ISCO Automated Samplers. A total of twenty storm events were captured, along with periodic baseflow sampling, and these data were used to characterize P concentrations and calculate seasonal P loadings. Results indicate that there is a strong positive relationship between turbidity, total suspended sediment and total phosphorus concentrations (R2 ranging from 0.64 to 0.83). The results of this project provide insight into transport of P and total suspended sediment within forested catchments of Lake Champlain tributaries. In particular, the research shows that fluxes in total phosphorus are linked to fluxes in total suspended sediment and that the overall monthly totals of P being exported from forested catchments are low, relative to urban, suburban and agricultural areas

Electrocoagulation for Treatment of Disinfection Byproducts, Organic Matter, and Per-And Polyfluoroalykl Substances.

Technologies are needed to treat contaminants such as disinfection byproducts (DBPs), trace organic compounds (TOrCs), and per- and polyfluoroalkyl substances (PFAS) in water to improve consumer safety and mitigate chronic risk. This dissertation focused on evaluating electrocoagulation (EC) and hydrogen peroxide (H2O2)-enhanced EC (peroxi-electrocoagulation; EC:H2O2) for treatment of these contaminants. The impacts of source water quality (such as natural organic matter [NOM]) on overall performance was assessed and the non-destructive and destructive pathways involved in treatment were evaluated. The first objective focused on EC performance for mitigating the formation of regulated DBPs in water to better substantiate EC’s performance relative to regulations and conventional treatment technologies. This objective was achieved by conducting a series of EC and conventional coagulation tests for multiple NOM sources and measuring the DBP formation potential following post-treatment chlorination. Overall, EC had similar performance to conventional coagulation, indicating that EC may be a competitive DBP mitigation technology. The second objective focused on enhancing the oxidizing capabilities of iron-EC by adding hydrogen peroxide to boost the oxidant yield via EC:H2O2. This process provided oxidative destruction of TOrCs in tandem with non-destructive separation pathways that can treat NOM as well as TOrCs. The energy inputs required for EC:H2O2 were favorable compared to other oxidative technologies, substantiating the case for EC:H2O2 as a combined destructive and non-destructive process for water treatment. The third objective assessed EC:H2O2 for PFAS mitigation and the influence of six different NOM sources on treatment efficiency. PFAS removal was observed for systems with and without NOM. However, the PFAS treatment pathways were different in NOM-containing systems, wherein more non-destructive removal, such as floatation layer accumulation, occurred. This difference may be due to the interactions between low molecular weight NOM, iron, and PFAS that form complexes that are more susceptible to non-destructive treatment and inhibit destructive treatment. These findings showed that real-world waters can heavily influence PFAS mitigation processes relative to treatment in synthetic laboratory matrices without background NOM and shift removal pathways. Overall, this research shows that EC and EC:H2O2 may serve as effective water treatment technologies for real-world waters containing NOM

Electrocoagulation-Electrooxidation for Mitigating Trace Organic Compounds in Model Source Waters

Conventional coagulation and oxidation are well suited for many drinking water operations to meet regulatory requirements for safe drinking water. However, these processes require auxiliary chemicals and materials that must be transported from off-site, which increases complexity of operations, and can pose difficulties for small treatment systems. Electrochemistry offers an innovative method to induce coagulation and oxidation processes for water treatment. Electrocoagulation (EC) together with electrooxidation (EO) is an attractive option for drinking water treatment systems because these processes generate iron coagulants using iron EC electrodes and oxidants (e.g., free chlorine and reactive oxygen species) using boron-doped diamond EO electrodes. This research evaluated the performance of combined EC-EO as a water treatment process for mitigating trace organic compounds in model groundwaters and surface waters. The trace organic compounds evaluated were acyclovir, trimethoprim, and benzyldimethyldecylammonium chloride (BAC-C10). These compounds represent different classes of trace organics found in source waters for drinking water treatment facilities. EO-only removed greater than 70% of acyclovir and trimethoprim in model groundwater matrices, but negligible BAC-C10 was removed relative to control experiments. Alternately, in surface waters, EO-only treatment was effective for BAC-C10 removal, but not for acyclovir and trimethoprim removal. EC-EO for model surface water treatment removed 73.5 ± 1.25% of dissolved organic carbon and improved downstream EO treatment of acyclovir, trimethoprim, and BAC-C10 by factors of 3.4, 1.7, and 1.4, respectively based on mean removal. However, EC-EO of model groundwater improved removal for only BAC-C10 (factor of 5.2 improvement), whereas ACY and TMP removal did not improve. BAC-C10 removal via EC-EO in groundwater was attributed to the particle separation step. EO was generally more energy efficient in treating model groundwaters than model surface waters. EC-EO improved the energy demands for treating model river water

Doctor of Philosophy

dissertationCardiorespiratory endurance is a major component of health-related fitness testing in physical education. FITNESSGRAM recommends the 1-mile Run/Walk (1-MRW) or the Progressive Aerobic Cardiovascular Endurance Run (PACER) to assess cardiorespiratory endurance by estimating aerobic capacity, or VO2 Peak. No research to date has cross-validated prediction models from both 1-MRW and PACER using current FITNESSGRAM criterion-referenced (CR) standards. Additionally, new prediction models for 1-MRW without a body mass index (BMI) term are needed to attenuate the problems incorporating this index into an aerobic capacity model. The purpose of this dissertation was to cross-validate various prediction models using 1-MRW and PACER and to develop alternative 1-MRW aerobic capacity prediction models for adolescent youth. Participants included 90 students aged 13 to 16 years. Each student completed the 1-MRW and PACER, in addition to a maximal treadmill test to measure VO2 Peak. Multiple correlations among various models with measured VO2 Peak were considered strong (R = 0.74 to 0.78). CR validity, examined using modified kappa (Κq), percentage of agreement (Pa), and phi was considered moderate among all models (Κq = 0.25 to 0.49; Pa = 72% to 79%; phi = 0.38 to 0.65). Two new models were developed from 1-MRW times, one linear and one quadratic model. The linear and quadratic models displayed multiple correlations of R = 0.77 and R = 0.82 with measured VO2 Peak, respectively. CR validity evidence was considered moderate with (Kq = 0.38; Pa = 73%; phi = 0.57) using the linear model and (Kq = 0.34; Pa = 70%; phi = 0.54) using the quadratic model. The accuracy of these models was confirmed using k-fold cross-validation. In conclusion, the prediction models demonstrated strong linear relationships with measured VO2 Peak, acceptable prediction error, and moderate CR agreement with measured VO2 Peak using FITNESSGRAM's CR standards to categorize health groups. The new 1-MRW models displayed good predictive accuracy and moderate CR agreement with measured VO2 Peak without using a BMI predictor. Despite evidence for predictive utility of the new models, they must be externally validated to ensure they can be generalizable to larger populations of students

Understanding asteroid collisional history through experimental and numerical studies

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect

Surveys, Astrometric Follow-up & Population Statistics

Asteroid surveys are the backbone of asteroid science, and with this in mind we begin with a broad review of the impact of asteroid surveys on our field. We then provide a brief history of asteroid discoveries so as to place contemporary and future surveys in perspective. Surveys in the United States have discovered the vast majority of the asteroids and this dominance has been consolidated since the publication of Asteroids III. Our descriptions of the asteroid surveys that have been operational since that time are focussed upon those that have contributed the vast majority of asteroid observations and discoveries. We also provide some insight into upcoming next-generation surveys that are sure to alter our understanding of the small bodies in the inner solar system and provide evidence to untangle their complicated dynamical and physical histories. The Minor Planet Center, the nerve center of the asteroid discovery effort, has improved its operations significantly in the past decade so that it can manage the increasing discovery rate, and ensure that it is well-placed to handle the data rates expected in the next decade. We also consider the difficulties associated with astrometric follow-up of newly identified objects. It seems clear that both of these efforts must operate in new modes in order to keep pace with expected discovery rates of next-generation ground- and space-based surveys.Comment: Chapter to appear in the book ASTEROIDS IV, (University of Arizona Press) Space Science Series, edited by P. Michel, F. DeMeo and W. Bottk

Excise Taxes, Consumer Demand, Over-Shifting, and Tax Revenue

This paper examines over-shifting in excise taxes, using the constant elasticity demand function under monopolistic competition. We apply the solution for price from this model to previous studies to obtain estimated price elasticities of demand. We also derive the excise tax, which maximizes tax revenue under this formulation, resulting in a revenue-maximizing tax-price ratio based upon the price elasticity. The model is applied to some previous experience regarding excise tax increases for alcoholic beverages and cigarettes. Our study offers structural insights behind empirical research that finds over-shifting. The model can also be used to help construct excise tax policy

Divide and Conquer Evolutionary TSP Solution for Vehicle Path Planning

The problem of robotic area coverage is applicable to many domains, such as search, agriculture, cleaning, and machine tooling. The robotic area coverage task is concerned with moving a vehicle with an effector, or sensor, through the task space such that the sensor passes over every point in the space. For covering complex areas, back and forth paths are inadequate. This paper presents a real-time path planning architecture consisting of layers of a clustering method to divide and conquer the problem combined with a two layered, global and local optimization method. This architecture is able to optimize the execution of a series of waypoints for a restricted mobility vehicle, a fixed wing airplane