Abstract

LEITAO, Bruno et al. Quadrennial monitoring of nitrates in the Nitrate Vulnerable Zone of Esposende-Vila do Conde. Rev. de Ciências Agrárias [online]. 2021, vol.44, n.4, pp.1-10.  Epub Nov 09, 2021. ISSN 0871-018X.  https://doi.org/10.19084/rca.25060.

The Council of the European Communities in 1991, through the Directive 91/676/EEC of 12 December 1991, recognized the importance of protecting areas of high susceptibility to water pollution, caused or induced by nitrates (NO3 -) of agricultural origin. One of these areas is the Nitrate Vulnerable Zone (NVZ) of Esposende-Vila do Conde, created in 1997 by Ordinance No. 1037/1997 of October 1, at the date designated as the free aquifer of Esposende and Vila do Conde, included in the list of Vulnerable Zones present in Ordinance 164/2010, of March 16. This article aims to disseminate the results of the monitoring of farms in the NVZ of Esposende-Vila do Conde, in a work carried out over a period of twelve years (three quarters) and based on Geographic Information Systems for the analysis of groundwater pollution caused by nitrates of agricultural origin. Through the use of the geostatistical interpolation technique IDW (Inverse Distance Weighting), and using the data obtained from 1,517 expeditious analyzes to the groundwater of farms and carried out between 2008 and 2019, it was possible to determine a decrease in the surface with high levels of contamination by nitrates (> 100 mg NO3-/ L) which decreased from 1,261 ha in the 2008-2011 quadrennium to 666 ha in the 2016-2019 quadrennium.

Keywords : Geostatistical interpolation technique; Nitrate Directive; Nitrate Vulnerable Zone; groundwater; hole; pit.

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