Sedimentos e nutrientes aportados a um reservatório de pequeno porte no Semiárido tropical

Abstract

The sediment and nutrients that are input to surface reservoirs compromise the quality and quantity of the stored water. The aim of this study was to investigate the dynamics of sediment and nutrient input along the drainage basin of a small reservoir in the semi-arid region. The reservoir under study was built in 1956 and has a storage capacity of 5.01 hm 3 . Seven trenches were dug along the drainage basin of the reservoir following the river. Sediment samples were collected at increasing depths of 20 cm until reaching the original riverbed. An analysis of particle size, total organic carbon (TOC), total nitrogen (TN), available phosphorus (P), exchangeable aluminium (Al), total iron (TFe) and pH was carried out. Approximately 60% of the sediment in the reservoir is composed of clay and silt, and 40% of sand. The greatest thickness of the sediment layer, as well as the greatest concentration of fine sediment, was registered in the section nearest to the dam. The values f o r TOC (2.47 < TOC < 34.47 g kg -1 ) and TN (0.69 <T N < 3.97 g kg -1 ) showed a positive and significant correlation with each other (r = 0.95) and with the fine sediment (r = 0.85; r = 0.77). The P (12.19 < P < 41.99 mg kg -1 ) showed an inverse relationship with the organic components, fine sediment, TFe and Al. The mean C/N ratio of 8.77 demonstrates the predominance of sources of anthropogenic pollution in the drainage basin of the reservoir. The fine sediment proved to a determinant factor in the retention and availability of TOC, TN and P, with the reservoir acting as a deposit for the input nutrients.

The Geochemical Sedimentary Record of a Historically Anthropogenically Impacted Coastal Lagoon (Rio de Janeiro State, Southeastern Brazil)

“…Granulometry interferes directly in pollutant sediment retaining. Finer sediment retains the highest amount of pollutants, in contrast to coarser sediment (Pereira et al, 2021;Poleto et al, 2009).…”

“…The statistical analysis indicated that concentration of trace elements in surface sediments, far above the maximum permissible limits established by Brazilian legislation (CONAMA, 2005;CONAMA, 2009) due to Cu and Pb exposure may be expected and, potentially, Cd. In this context, continuous monitoring concerning trace element contamination at the Maricá-Guarapina system is required, as potential food web bioaccumulation and biomagnification processes are noted, allied to the fact that fishing is a main socioeconomic activity carried out in this area and that Padre Lagoon is located within an Environmental Protection Area (Pereira et al, 2021). Many trace elements and metalloids are toxic to living organisms at any concentration, and even essential elements become toxic at higher levels than toxic threshold values.…”

How Forest Management with Clear-Cutting Affects the Regeneration, Diversity and Structure of a Seasonally Dry Tropical Forest in Brazil

“…Furthermore, in these areas, in addition to the lack of burning or stump removal, stubble is raked over the ground (see [25]). These factors, added to the high level of regeneration seen in this study following clear-cutting, should mitigate the impacts associated with agricultural use (compared to conventional management with itinerant agriculture), such as those seen on surface water resources in the region [32][33][34].…”

“…Disordered land use has been associated with advances in the processes that reduce the forested areas of the SDTF [31], adversely affecting the quality of surface water resources in artificial reservoirs [32][33][34], the main source of water in the region. On a global scale, areas of tropical forest are now smaller with reduced structural complexity and species richness and occupy steeper terrain than they did half a century ago [35].…”

Sustentabilidade No Uso De Fósforo: Uma Revisão Bibliográfica Com Foco Na Situação Atual Do Estado De São Paulo, Brasil

“…Foi possível notar também o impacto dos níveis de coluna d'água, onde, em sua diminuição, pela ressuspensão de sedimentos, existe o prejudicial incremento da concentração de fósforo. 42 A fim de atingir o enquadramento dos corpos d'agua, é necessário a aplicação de diferentes tipos de tratamentos, segundo os limites de lançamento de P, de modo que quanto menor a concentração final, maiores são as estruturas de tratamento e a sua complexidade. 43…”