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Full-Text Articles in Physical Sciences and Mathematics
Internal Loading Of Nitrogen (N) And Phosphorus (P), Reduced N Forms, And Periodic Mixing Support Cyanobacterial Harmful Algal Blooms (Habs) In Shallow, Eutrophic Honeoye Lake (New York, Usa), Justin Adam Myers
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Cyanobacteria are important primary producers, but large cyanobacterial harmful algal blooms (HABs) have many negative ecological and health impacts and are becoming increasingly common. Honeoye Lake (New York, USA) is a shallow, eutrophic lake characterized by increasingly frequent HABs. Nitrogen (N) and phosphorus (P) loads often drive HABs in lakes, and sediment processes can contribute to N removal (e.g., denitrification) or loading (e.g., N fixation, remineralization). Sediment cores and lake water were collected during May–October (2016–2018) at two sites and incubated with no amendments (controls) or 15N stable isotopes to measure sediment nutrient fluxes and N cycling dynamics in Honeoye …
Atmospheric Effects On Radar/Ladar Detection Of Seismic Activity, Michelle Frances Via
Atmospheric Effects On Radar/Ladar Detection Of Seismic Activity, Michelle Frances Via
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This thesis investigates how well ground vibrations can be detected at ladar or radar wavelengths and how the atmosphere may impact the observation of such activity. First understanding atmospheric hindrances at each of these wavelengths is helpful to prioritize by those yielding best transmission results. A prerequisite to the outdoor field experiment performed for this study involves analyzing atmospheric effects characterization at six probable wavelengths using the Laser Environmental Effects Definition and Reference tool (LEEDR) developed by the Air Force Institute of Technology's (AFIT) Center for Directed Energy (CDE). These wavelengths, selected from the shortwave infrared and microwave portions of …
Stability Of Monomethylmercury In Water, Sarah Elyse Harvey
Stability Of Monomethylmercury In Water, Sarah Elyse Harvey
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Monomethylmercury (MMHg) bioaccumulates in aquatic food webs, leading to concentrations in fish that increase health risks for humans who consume fish. As a result of processes that produce and decompose it, MMHg concentrations are notoriously unstable in many natural waters. I examined the stability of MMHg in both filter-sterilized (< 0.1 µm) reagent-grade water and 0.22-µm filtered sediment pore water from Grand Lake St. Marys, Auglaize and Mercer Counties, Ohio, each at three MMHg treatment concentrations (1, 5, and 50 ng/L). Reagent-grade water samples were incubated under both light and dark conditions at either 5 or 26 °C for 112 days. Pore water samples were incubated in the dark at 26 °C, mimicking environmental conditions, for a period of 98 days. Decay constants (± 95% CI) for solutions containing either 1 or 5 ng/L MMHg in reagent-grade water ranged from 0.0009 ± 0.0013 to 0.1225 ± 0.0150 d-1, with greater decay constants at higher temperature and no significant effect of light exposure. In contrast, decay constants for 50 ng/L MMHg in reagent-grade water were much less than those in more dilute solutions, ranging from 0.0018 ± 0.0015 to 0.0055 ± 0.0023 d-1, with both light and temperature influencing MMHg decomposition. Decay constants of MMHg in pore water were found to be independent of initial concentration of MMHg; however, decay constants in pore water samples were 3-fold higher than those in reagent-grade water amended with the same initial concentration (p = 0.007). These results suggest that natural constituents in pore water accelerate MMHg decay reactions.