Estudio multi-isotópico de la atenuación natural de la contaminación por nitratos en un sistema acuífero regional: Plana de Vic ( Osona, NE España)

The presence of nitrate in groundwater of the Osona area is derived from the intensive cattle raising. Even though local administration regulates and controls the present use and distribution of manure as fer tilizer, according to legal application rates, nitrate pollution in Osona shows the effect of decades of uncontrolled manure application. Vitòria (2004) using stable isotopes determined the presence of denitrification processes (natural attenuation of nitrate pollution) in a small area located in the Osona province. The main goal of this still on-going research (2005-2006) is to determine the extent of denitrification at a regional scale, and the processes that control natural attenuation, using multi-isotopic methods (dD, d18O, T, d34S, d15N, d13C). Results show that denitrification is active in two areas, and that this process is linked to pyrite oxidation. In the studied area, data do not allow to identify the role of or ganic matter oxidation in denitrification. The observed denitrification processes reveal optional strategies for nitrogen attenuation