- Dr. Mathieu Sebilo, Institut d’Ecologie et d’Environnement de Paris, Université Pierre et Marie Curie, France
- Date: May, 20, 2014 12:00 am
- Place: Sala d'Actes del Institut de Ciències de la Terra Jaume Almera(ICTJA)
- Location: C/ Solé i Sabarís s/n, Barcelona
Using available data on nitrogen concentration in surface and groundwater as well as a modelling approach, a budget of nitrogen transfer has been established at the scale of the 75 000 km² watershed of the Seine River system. 3 major sectors can be distinguished: (1) Upstream areas, where diffuse sources of nitrogen leached from agricultural soils play a dominant role, but where riparian areas denitrify as much as 50% of the nitrate before it reaches surface water. (2) Major branches of rivers where domestic and industrial inputs are concentrated, still mostly under the reduced (ammonium and organic) nitrogen forms. (3) The major fluvial and estuarine sector of the Seine, downstream from Paris, where these point inputs are metabolized through nitrification and denitrification. It will be shown how the measurement of natural isotopic composition of nitrogen in nitrate and ammonium allows, by use of a modelling approach, to independently validate this nitrogen budget in these 3 different sectors.