Estimación de la concentración de nitratos usando el modelo Hydrus 1d en el horizonte A de un suelo con cobertura de gramíneas en la zona central del Humedal la Florida
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This research is aimed at studying the flow and transport processes of nitrate from rainwater through the soil profile in the unsaturated zone of the area comprising the central zone of The Florida wetland for the year 2021. The research was first developed by collecting information corresponding to the physical properties of the soil from the research work "Relationships between geo morphometry and physical properties of soils in the central zone of The Florida wetland", the pedotransfer values were provided by bibliographic and database review. Climatological information was collected from NASA geostationary operational environmental satellites 4 and 5. The sampling units were chosen under a Complete Randomized Design DCA, the units chosen randomly were 5 points in which the A horizons were located on pasture cover whose depth varied between 25 and 55cm. Six samples were taken for each A horizon, the rainwater was sampled following the parameters of the "Guide for Rainfall Sampling of the International Atomic Energy Agency/Global Network on Isotopes in Precipitation" of 2014. The samples were taken to laboratory where the methodology of nitrate determination in water by UV spectrophotometry, IDEAM 2007, was adopted. Secondly, the HYDRUS 1D program was used which uses the numerical solution of the Richards equation and the advection-dispersion equation, to quantify the travel time of nitrate from the soil surface, through the A horizon, to the B horizon, and the concentration of nitrate through the soil A profile. Model evaluation will be performed by means of the Nash Sutcliffe coefficient and the standard deviation radius of the root mean squared error observations. The results showed an area with a topography with slopes of less than 1%, with an average daily rainfall of 9 mm, average temperatures of 8.5° C, moderately deep soils, formed mainly by fluvial-lacustrine deposits of sandy-loam and silt-clay texture, these soils have humidity ranging from 30% to 80%, and the results also identified the economic activities of intensive agriculture and livestock very close to the wetland water body. For the behavior of nitrate, it was observed that, in the rainy months, the nitrate content decreases in the days of higher precipitation and increases in the days of lower precipitation. The study concluded that nitrate remains longer in horizons with clayey texture, low hydraulic conductivity and apparent density of less than 1.5 cm3/g; in this horizon, nitrates take up to 60 days to decrease their concentration. On the other hand, for the sandy or sandy loam texture, nitrate concentration decreases in less time.