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The study of spatial and temporal aspects of denitrification processes in Roxo catchment, Portugal.

Gamises, Fransiska (2009) The study of spatial and temporal aspects of denitrification processes in Roxo catchment, Portugal.

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Abstract:In this study, spatial and temporal soil denitrification of the Roxo catchment in southern Portugal was investigated based on field samples, laboratory techniques and satellite data. Further, a simple prototype model is proposed and implemented to obtain actual spatial and temporal denitrification rates (Da) at the catchment level. Undisturbed soil samples were incubated under anaerobic condition with addition of 3 mg potassium nitrate (KNO3) for 45 days, and potential denitrification rates were measured at regular intervals with the nitrate reduction method. Potential denitrification rates obtained for the current study area ranged from 0.0 to 0.7 g N m-2 d-1 with average NO3-N loss of 3.7 to 23.4 mg N kg-1 soil. The Nemis denitrification model concept was used and embedded in a spatial and temporal modelling framework. To obtain the denitrification model reduction functions for soil pH, soil nitrate, land surface temperature and soil moisture, all respective data of the model variables, where normalised to [0, 1] to be used in the prototype model to estimate Da . rates. To evaluate the soil moisture effect on the catchment level, we tested a Topographic Wetness Index (TWI). Dynamic and spatial soil moisture influences on denitrification for the catchment was tested using soil moisture outputs from the SWAT model. Land surface temperatures were derived from the Meteosat geostationary satellite and used in spatial temporal modelling. The annual denitrification rate for the current study area catchment was estimated at 0.29 g N m-2 d-1 when using SWAT derived soil moisture estimates. The Da for TWI derived soil moisture was estimated at 0.35 g N m-2 d-1. The proposed methodology is promising, but more detailed process descriptions and modelling of spatially and temporally varying soil moisture and temperature seems required to obtain more reliable estimates of this important environmental process, also in relationship to climate change. Keywords: Denitrification rate, nitrate reduction method, Nemis, soil moisture, land surface temperature, Topographic Wetness Index, remote sensing, GIS
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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