Análise da função de uma várzea na ciclagem de nitrogênio
Data
2017-11-15
Autores
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Biblioteca Digital de Teses e Dissertações da USP
Universidade de São Paulo
Escola de Engenharia de São Carlos
Universidade de São Paulo
Escola de Engenharia de São Carlos
Resumo
Descrição
Para identificar a influência de uma área de várzea do ribeirão do Feijão (São Carlos-SP) sobre a ciclagem de nitrogênio e sobre a qualidade da água superficial e subsuperficial, foram analisadas as características físicas e químicas da água e determinadas as taxas de nitrificação e desnitrificação dos sedimentos da várzea. A maior concentração dos compostos nitrogenados foi observada na água de interface subsuperficial da várzea, região mais ativa em termos de fluxos de água e materiais. As taxas de nitrificação variaram de 0,145 a 0,068 μmol N-NO3-.g-1.dia-1 e a rota metabólica predominante foi a autotrófica, na qual as bactérias utilizaram amônio como substrato. As taxas de desnitrificação tiveram um valor médio de 0,0081 nmol N2O.g-1.dia-1. Mediante um modelo de estimativa foi calculado que 70% da água que circula no Ribeirão do Feijão provém do lençol que flui sob terras secas e o restante das áreas de várzea da bacia. Foi observado que existe uma considerável redução das concentrações dos compostos nitrogenados, principalmente do amônio, desde as zonas ripárias mais distantes do curso do rio até o canal, passando pela área de várzea. O funcionamento da várzea como sistema de filtro e depuração das águas subsuperficiais que alimentam o rio foi evidenciada pelas características físicas e químicas da água do rio em relação ao uso do solo na bacia.
In order to identify the influence of a floodplain area of the Feijão stream (São Carlos-SP) on surface and subsurface water quality, the physical and chemical characteristics of the water were analyzed and the floodplain sediment\'s nitrification and denitrification rates were determined. The highest concentration of nitrogen compounds was observed at the floodplain\'s subsurface water interface it being the most active region with respect to water and solute flow. Nitrification rates varied between 0.145 and 0.068 μmol N-NO3-.g-1.day-1 and the autotrophic metabolic route dominated, in which bacteria use ammonia as a substrate. Denitrification rate average was 0.0081 nmol N2O.g-1.day-1. Through a model it was estimated that 70% of the water flowing in the Feijão stream came from the water table flowing under dry land, the remainder coming from the floodplain of the area. A significant reduction of nitrogen compound concentration, mainly ammonium, was observed between the more distant riparian zones and the river\'s channel going through the floodplain. The floodplain\'s action as a filtering system for the water reaching the river was brought out through the physical and chemical characteristics of the river water relative to land use in the catchment area.
In order to identify the influence of a floodplain area of the Feijão stream (São Carlos-SP) on surface and subsurface water quality, the physical and chemical characteristics of the water were analyzed and the floodplain sediment\'s nitrification and denitrification rates were determined. The highest concentration of nitrogen compounds was observed at the floodplain\'s subsurface water interface it being the most active region with respect to water and solute flow. Nitrification rates varied between 0.145 and 0.068 μmol N-NO3-.g-1.day-1 and the autotrophic metabolic route dominated, in which bacteria use ammonia as a substrate. Denitrification rate average was 0.0081 nmol N2O.g-1.day-1. Through a model it was estimated that 70% of the water flowing in the Feijão stream came from the water table flowing under dry land, the remainder coming from the floodplain of the area. A significant reduction of nitrogen compound concentration, mainly ammonium, was observed between the more distant riparian zones and the river\'s channel going through the floodplain. The floodplain\'s action as a filtering system for the water reaching the river was brought out through the physical and chemical characteristics of the river water relative to land use in the catchment area.
Palavras-chave
Ciclagem de nutrientes, Nitrogênio, Rios, Várzea, Foodplain, Nitrogen, Nutrient cycling, Streams