Event-based sediment budgets were developed in a small agricultural sub-watershed using radionuclide tracers in conjunction with traditional monitoring techniques. The result of these budgets quantified the flux of material from each sediment source in the sub-watershed. The first step in the study was to quantify the net flux of material through the watershed outlet for runoff events. Results indicated that a pronounced clockwise hysteresis effect occurred during all studied events. The cause of the hysteresis effect was attributed to exhaustion of the upland (i.e., hillslopes and floodplains) sediment source. The hysteresis effect was dampened during an extreme flash flood event that caused overbank flow. This dampening was attributed to an increase in upland sediment mobilization resulting from overbank flow. Results of the event-based monitoring were compared against a previously developed sediment rating curve that assumed a power-law relationship between suspended sediment transport and water flow rates. The results indicate that the power-law relationship grossly under predicted the sediment flux over each runoff event. A tracing technique was utilized to establish the relative contributions from the uplands and the stream channel (i.e., channel banks and bed). This technique used the relationship between the naturally occurring radionuclide tracers 7Be and 210Pbxs to differentiate eroded upland soils from channel-derived sediments in the suspended sediment loads. A simple two end-member unmixing model was used to determine the relative contribution from each source. Results indicate that the upland source was the dominant contributor to the suspended load early in the runoff events, but channel contributions were more prevalent at later stages, reinforcing the conclusion drawn from the hysteresis observation. Further analysis of the results indicated that the uplands contributed the majority of the material to the suspended load because the sediment transport rate during the early stages of the event was much larger than during the later stages. Therefore, watershed managers wishing to minimize non-point source pollution resulting from erosion should first focus their efforts on reducing erosion of upland soils.

The objective of this study was to determine the origin of sediment currently collected in Black Lake, an extremely productive salmon fishing environment located along a remote section of the Alaska Peninsula, AK. To meet the goals of this project, soil cores were collected at the site during an extensive field study. The field investigation was based on a prior numerical study, which revealed the most erodible areas and the hydrologic patterns in Black Lake and its tributaries, namely the Alec River. From this study, select locations of the catchment were chosen for coring. These included the Alec River Delta, Black Lake, and four tributaries in the catchment. These samples were analyzed for the radionuclides 137Cs and 210Pb to determine soil deposition rates using Gamma Spectroscopy. To determine the sedimentation rate of each coring location, spikes in the 137Cs activity were connected to the known cesium deposition peak in 1964 and the depth of soil above the peak was divided by the number of years that have passed. This gave a spatially averaged deposition rate within the lake of roughly 0.25 cm/y. This result closely compared to the numerical study of Elhakeem and Papanicolaou (2008) and to a study done in close proximity to Black Lake in the early 1990s (Stihler et al. 1992). The rate of each location was then validated by visually analyzing each core using soil color demarcation lines to determine the soil composition. This analysis resulted in the discovery of a variety of soil types ranging from silts and clays, to coarse sands, to volcanic tephra. It was concluded that the lake flow patterns, the introduction of volcanic material from nearby Mt. Veniaminof, and back water resulting from deposition occurring down stream of Black Lake at the Black River's junction with the West Fork River are some of the main contributors for the deposition in the lake.

No description available.

Made available in DSpace on 2014-10-09T12:35:55Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:25Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Made available in DSpace on 2014-10-09T12:35:55Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:25Z (GMT). No. of bitstreams: 0 / O fosfogesso, também denominado gesso agrícola, sub produto das industrias de fertilizantes fosfatados, pode ser utilizado como condicionador do solo devido a sua capacidade de proporcionar melhorias ao sistema solo-planta. No entanto, este resíduo concentra os radionuclídeos das séries do U e Th, presentes na rocha fosfatada usada como matéria prima, que podem impactar o meio ambiente. Com a finalidade de se verificar a concentração dos radionuclídeos biodisponíveis , foram analisadas amostras de fosfogesso e de fertilizantes fosfatados monoamônio fosfato e fertilizante superfosfato triplo, de duas procedências nacionais. A determinação da concentração de 226Ra, 228Ra e 210Pb se iniciou com a análise por espectrometria gama. Em seguida as amostras foram submetidas a um processo de extração branda com solução de EDTA-NH4 (0,05M) para que então o material lixiviado fosse analisado por meio de contagem alfa e beta total em detector proporcional de fluxo gasoso. Foram obtidos valores médios de extração de 1,6% - 1,7% para 210Pb, 0,5% - 1,4% para o 226Ra e 0,1% - 1,0% para o 228Ra nas amostras de fosfogesso. A baixa porcentagem de extração obtida para os radionuclídeos pode ser explicada tendo-se em vista que a solubilidade do fosfogesso variou de 7,7% a 16%. Para os fertilizantes fosfatados do tipo monoamônio fosfato os valores médios de extração foram inferiores a 26% para o 226Ra, inferiores a 10% para o 228Ra e inferiores a 10% para o 210Pb. Apesar da solubilidade da ordem de 77% dos fertilizantes fosfatados do tipo monoamônio fosfato, muito pouco dos radionuclídeos, presentes inicialmente, se concentraram na solução extraida. Para os fertilizantes fosfatados do tipo superfosfato triplo os valores médios de extração foram de 2,3% para o 226Ra, 1,2% para o 228Ra e 11,3% para o 210Pb. Mesmo com a solubilidade de 66% os fertilizantes fosfatados do tipo superfosfato triplo, muito pouco dos radionuclídeos, presentes inicialmente, se concentraram na solução extraida. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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