Silva, Hérika Cavalcante Dantas daSilva, Rayane Dias da2023-08-162023-08-162023-05-26SILVA, Rayane Dias da. Liberação de fósforo da interface água-sedimento e os efeitos da variação de volume, ressuspensão e difusão em um reservatório raso do semiárido: um estudo em escala experimental. Orientador: Hérika Cavalcante Dantas da Silva. 2023. 51f. Dissertação (Mestrado em Engenharia Civil e Ambiental) - Centro de Tecnologia, Universidade Federal do Rio Grande do Norte, Natal, 2023.https://repositorio.ufrn.br/handle/123456789/54515High concentrations of nutrients, mainly phosphorus, result in the eutrophication of inland water sources. Among the main sources of phosphorus for these ecosystems, the sediment stands out as an internal source of nutrients in reservoirs, since the phosphorus accumulated in the sediment can be released due to internal fertilization in shallow lakes. The tropical semi-arid region of Brazil has low precipitation and high temperatures, conditions that result in high evaporation and fluctuations in the water level of reservoirs used for supply. Thus, the objective of this research was to evaluate, on an experimental scale, how changes in volume of a eutrophic reservoir in the tropical semi-arid region affect the processes of sediment resuspension by wind and molecular diffusion, as well as their influence on the release of phosphorus from the sediment. to the water column. Thus, an experiment was carried out in microcosms using water from the Dourado reservoir and deionized water simulating the sediment-water interface of the reservoirs. Thus, to analyze the effect of volume variation, 150 g of sediment were introduced initially with 900 ml or with 400 ml of bottom water from the Dourado reservoir or deionized water, in 1L beakers. Therefore, to analyze the diffusion, water from the reservoir was introduced into some microcosms and deionized water into others. The resuspension behavior of the sediment was analyzed using the jar test equipment. The microcosms had two events of surface agitation of the water column, one on day 14 and another on day 28 of the experiment, in which the forces of wind waves were simulated by the rotation of propellers, thus inducing resuspension with an agitation time of 2 minutes and a low rotation (20 rpm) and a higher rotation (40 rpm). Thus, through collected and analyzed aliquots, it was possible to quantify the concentrations of soluble reactive phosphorus and total dissolved phosphorus released from the sediment into the water column in the microcosms, and thus calculate the P release rate from the sediment to the column of water. The values of soluble reactive phosphorus release rates in microcosms with larger volumes ranged from (0.09 – 0.61 mg.m-2.day-1) and in microcosms with low volumes were between (0.05 – 0. 18 mg.m2.day-1) using deionized water. While, the release rates of total dissolved phosphorus in the microcosms with larger volumes ranged from (0.93 – 1.31 mg.m-2.day-1) and in the microcosms with low volumes were between (0.23 – 0. 26 mg.m-2.day-1) using deionized water. The values of soluble reactive phosphorus release rates in microcosms with larger volumes ranged from (0.15 – 0.22 mg.m-2.day-1) and in microcosms with low volumes were between (0.01 – 0. 04 mg.m-2.day-1) using water from the Dourado reservoir. While, the total dissolved phosphorus in the microcosms with larger volumes ranged from (0.79 – 1.05 mg.m-2.day-1) and in the microcosms with low volumes were between (0.16 – 0.28 mg.m -2.dia-1) using water from the Dourado reservoir. From the results it was observed that the release of phosphorus in deionized water was greater than in water from the reservoir. This study confirmed that through molecular diffusion, flow occurs from the gradient containing higher concentrations of phosphorus, such as sediment, to overlying water without phosphorus, such as deionized water. In addition, the greater release of phosphorus occurred in microcosms that had larger volumes that had volume reduction, in relation to microcosms that had low volumes, in which they reduced their volumes until they were almost dry, as an effect of the volume variation, together with the environmental conditions. Since the volume variation associated with environmental conditions of temperature, pH and dissolved oxygen can contribute to increasing the flux of mobile phosphorus from the sediment to the natural water in the reservoir. In this context, the release of phosphorus from the sediment raises the concentrations in the water, maintaining the eutrophic state of the reservoir.Acesso AbertoEutrofizaçãoFertilização internaSecaFluxos de nutrientesGradiente de concentraçãoFlutuação de nívelmasterThesisCNPQ::ENGENHARIAS::ENGENHARIA CIVIL